In the emerging transportation electrification applications, there is an increasing demand on concurrently pursuing high reliability, high energy efficiency, and high power density of power converters. Conventional cooling technologies, such as using bulky heatsinks or cold plates, have constrained further performance improvements of power converters. Based on an innovative immersion cooling technique, this paper presents a high-fidelity, multi-physics modeling and experimental validation framework for a 100-kW, five-level active neutral point clamped (5L-ANPC) power inverter, making it the first comprehensive study on this topic. The study begins by examining the electrical performance of the 5L-ANPC inverter, followed by the computation of semiconductor losses to be used as heat sources in subsequent thermal simulations. Afterwards, the immersion-cooled inverter is modeled and analyzed by conducting high-fidelity computational fluid dynamics (CFD) simulations. Various operating conditions and thermal design factors for the immersion-cooled 5L-ANPC inverter are considered, and the related impacts are investigated to characterize the thermal performance of the inverter. The results demonstrate significantly reduced semiconductor junction temperatures and more uniform heat distribution compared to conventional air cooling. The findings highlight the advantages of immersion cooling in thermal management, leading to higher output power and higher reliability. Finally, prototypes of air-cooled and immersion-cooled inverters are developed with intensive testing to compare the thermal performance. The multi-physics simulation results showing the superior performance of immersion cooling are also verified in the experiments.

The rapid adoption of fast-switching wide-bandgap (WBG) semiconductor devices in motor-drive systems has introduced significant benefits in achieving high efficiency and high power density, but also posed challenges associated with reflected overvoltage phenomena. Such reflected overvoltages impose severe high-frequency voltage stress on motor stator windings, which accelerate insulation degradation and undermine the reliability of motor stator windings. Traditionally, RLC dv/dt filters have been used as an effective mitigation technique for limiting voltage slew rates and protecting the motor winding against these reflected overvoltages. However, these filters introduce excessively additional losses, size, and weight to the overall motor-drive systems. In contrast, the recently proposed smart coil circuit (SCC) is emerged as an alternative mitigation technique. This new approach enables effective suppression of reflected overvoltages with ultra-high efficiency through its adaptive, ultra-compact, and self-powered design. This paper presents a comparative study of the smart coil mitigation technique versus the conventional RLC dv/dt filter for overvoltage mitigation. The comparison focuses on operating efficiency, the effectiveness of mitigating overvoltage stress on motor stator windings, and identifying which mitigation technique is more effective for various operating conditions. Finally, comparative experimental validations based on a 2-hp motor-drive system demonstrate the effectiveness of both mitigation methods and provide an assessment of their strengths and limitations in WBG based motor-drive systems.

Solid-state transformers (SSTs) are attracting increasing attention in modern power conversion systems due to their higher efficiency, improved power density, and increased power quality compared with conventional bulky electromagnetic transformers. Despite these advantages, the widespread adoption of SSTs is still limited by reliability concerns, mainly due to the large utilization of semiconductor power devices and the resulting higher probability of switch faults, among which open-circuit faults (OCFs) are probably the most common type of device failures for practical SST applications. To address this challenge, a fast online OCF diagnostic method is proposed in this paper. The method monitors abnormal variations in the high-frequency transformer current and voltage, combined with the existing real-time switching state information, to detect and identify faulty switches without requiring any additional hardware. This non-intrusive and cost-effective method avoids extra system complexity and cost, and achieves rapid OCF detection within only a few switching cycles (i.e., 30 $\mu$s of detection time in this study). Simulations and experimental results validate the accuracy, robustness, and fast diagnostic capability of the proposed method under various operating conditions.

Advanced thermal management is critical for enhancing the efficiency, reliability, and power density of electric vehicle traction inverters. In this letter, targeted at a Silicon Carbide (SiC) three-phase three-level T-type traction inverter, a comparative performance evaluation of a novel immersion cooling technique versus conventional heat sink and cold plate-based cooling methods is presented. Multiphysics modeling, simulation, and analysis are conducted, and experiments based on an SiC T-type inverter prototype are carried out to verify the performance comparison. Key thermal performance metrics, including steady-state junction temperature of the SiC mosfets and thermal distribution of the SiC inverter, are presented. The results reveal that immersion cooling demonstrates obvious advantages under certain conditions, such as high power levels and elevated flow rates. The conclusion provides new insights on thermal management of power converters, highlighting immersion cooling as a promising solution for traction or propulsion power converters.

Power electronic converters (PECs) are fundamental components in various safety-critical applications such as electrified transportation and renewable energy generation. Therefore, ensuring the reliability of PECs throughout their entire life cycle has become increasingly important. In this context, owing to the ongoing digitalization and data engineering trends, digital twin (DT) technology has become a promising tool to improve the reliability and performance of PECs through online health monitoring and intelligent decision-making. This paper presents a comprehensive and in-depth review of DT development for high-reliability PECs. A four-stage systematic framework is proposed to review the development of DT: 1) converter-level and system-level application types, 2) implementation objectives, 3) modeling methodologies, and 4) supporting mathematical algorithms. In addition, the paper explores the concept of active versus passive DT decisions based on their objectives and interaction with the physical controller of PECs. To provide more insight into health monitoring objectives, a topology-oriented classification of DT implementation methods is presented, which enables readers to locate and understand relevant DT solutions based on various converter types with electrical or thermal modeling. This paper aims to serve as a practical guide for researchers and engineers involved in the development or analysis of DT models for PECs.

While wide bandgap (WBG) switches have revolutionized power electronics and motor-drive systems, the high $dv/dt$ associated with these fast-switching semiconductors can easily induce reflected high-frequency overvoltage spikes on motor stator terminals. The shorter rise time of the voltage pulses confines the cable length between the inverter and the motor in practice to avoid overvoltage across the motor stator windings. Even with shorter cables, voltage spikes from variable-speed drives can still cause premature insulation failure and reduce the remaining useful lifetime of the motors. While effective, conventional methods such as $dv/dt$ passive filters or active gate drivers are usually bulky and/or inefficient. To address this problem, an overvoltage mitigation solution, named “Smart Coil,” is introduced in this article. The smart coil circuit is installed in parallel with the first coil of each motor phase, which typically experiences the highest reflected overvoltage. Upon detection of overvoltage, the proposed ultracompact smart coil circuit, located at the motor junction box, is activated to limit voltage stress across the coils. Since the smart coil is connected in parallel with the first coil, it only needs to process very low pulsed power during the overvoltage transients. Therefore, it has high efficiency and an ultracompact footprint while effectively mitigating voltage spikes. The proposed smart coil circuit can be easily scaled for various motor-drive systems regardless of the cable length or rise time of the switching devices. Simulation and experimental test results are provided to verify the effectiveness of the proposed method.

Liquid-immersed power transformers are an integral part of the electrical grid. Long and reliable service life is of crucial importance in the design and operation of these power apparatuses. Transformer lifetime is mainly determined by the winding insulation system, which ages faster at high temperature. Nanofluid is a new type of oil with enhanced thermal and dielectric properties. Adding nano particles to the cooling oil increases its thermal conductivity, leading to more effective thermal conduction of the transformer. Therefore, hotspot temperature in the transformer windings decreases and hence the lifetime of the transformer is improved. On the other hand, utilization of nanofluids enhances the withstanding capability of the insulation material by scavenging the moisture in the transformer oil. In this paper, various laboratory oil samples will be introduced to serve as the next-generation transformer coolant. In order to understand and verify the behavior of the newly developed oils, finite element analysis and finite volume methods are used for the multi-physics simulations. A comparative study and experimental validation are conducted to show the superiority of nanofluid with respect to the state of the art mineral oil in terms of hotspot temperature and dielectric insulation strength which lead to lifetime improvement.

Power transformers serve as indispensable elements in nearly every electrical power system. Ensuring the continuous operation of power transformers is pivotal in maintaining the reliability and safety of the power network. Hotspot temperature (HST) in windings is a key factor that indicates the health condition of a power transformer. To determine the temperature of the transformer windings, it is essential to obtain the temperature distribution inside the transformer. This paper introduces a high-fidelity multi-physics modeling and simulation framework focused on predicting the reliability of large power transformers. The methodology relies on the application of three-dimensional (3D) finite element analysis (FEA) and computational fluid dynamics (CFD). In particular, electromagnetic modeling and simulation using FEA are conducted to calculate transformer losses. Subsequently, a thermal-hydraulic model is established to determine the temperature distribution. More importantly, this is to identify the HST in the transformer windings, which is further utilized to determine the transformer lifetime. Additionally, a sensitivity analysis is carried out to evaluate how the properties of the cooling oil affect both temperature distribution and HST. Finally, experimental results are provided to confirm the multi-physics modeling and simulation results.

High-performance switching devices such as SiC MOSFETs introduce high-frequency ringing and overvoltage transients at motor terminals, leading to uneven voltage distribution across windings. In SiC-driven motors, the first coil and initial turns experience significant overvoltage stress, increasing the risk of insulation degradation and interturn faults. This study proposes an analog circuit to mitigate overvoltage stress. The circuit detects high dv/dt in the first coil and adaptively inserts a ceramic capacitor via a GaN switch, forming a low-impedance path for high-frequency currents. This diverts part of the transient energy to the second coil, reducing stress on the first coil and promoting uniform voltage distribution. The GaN switch remains closed to sustain the high-frequency current path through the capacitor, adapting to different operating conditions and cable lengths. The circuit was prototyped and experimentally validated on a 2hp induction motor driven by a SiC inverter, demonstrating its effectiveness in mitigating overvoltage stress. This compact solution enhances the reliability of SiC-driven motor systems by addressing uneven high-frequency voltage distribution.

Model predictive position control (MPPC) is a promising control method for planar switched reluctance motors (PSRMs) to achieve high-precision trajectory tracking. However, the control performance of MPPC may deteriorate due to a mismatch between the system model and the actual system. To address this issue, online parameter identification can be used as an alternative method to model refinement. In this paper, an MPPC method based on recursive extended least squares (RELS) is proposed to improve the trajectory tracking performance of a laboratory-developed PSRM system. The conventional dynamic model and RELS-based parameter identification dynamic model for the PSRM are established. The predictive model is developed using the parameter identification dynamic model, with its parameters updated online. The control law is derived from the developed predictive model and the defined cost function, and the system stability is subsequently analyzed. The simulation and experimental results show improvement in the trajectorytracking performance of the PSRM system. The effectiveness of the proposed method is verified.

In this article, a predictive position control method based on an intelligent prediction model with nonlinear disturbance is proposed to improve the position tracking performance of precision motion systems. The intelligent prediction model is constructed employing an optimized neural network structure. This model takes the motor state, control, and disturbance sequences as inputs, producing predictive position sequences as outputs. The disturbance sequence related to the reference speed sequence is initially unknown and requires determination. To enhance the model accuracy and the practical applicability of control applications, the model structure is optimized into a linear form with nonlinear disturbances, improving its practical applicability for controlling precision motion systems. The unknown model parameters are determined through a designed algorithm using the backpropagation method and experimental data. Subsequently, the intelligent prediction model is utilized to develop a predictive position controller. Moreover, an explicitly analytical control law is derived to achieve high-precision and robust position tracking while reducing energy consumption to the greatest extend. The developed controller comprises state feedback control, feedforward control, and disturbance feedforward compensation, leading to a more streamlined and compact control configuration. Finally, the effectiveness of the proposed method is validated via the comprehensive experiment.

This article presents an innovative digital twin (DT) strategy for health monitoring of five-level active neutral point clamped (5L-ANPC) power converters, which are extensively utilized in high-power, safety-critical applications. Despite their widespread use, the reliability of 5L-ANPC inverters is often compromised due to the large number of semiconductor devices employed, posing challenges for their broader deployment in safety-critical applications. The proposed approach introduces a real-time DT replica that continuously monitors crucial parameters to assess the inverter’s performance and detect open-circuit (OC) faults in the switches. This methodology not only enhances reliability but also reduces maintenance downtime costs. Specifically focusing on OC switching faults, this article presents a fast online DT-based fault diagnostic method. The proposed diagnostic technique leverages the existing dc-link capacitor and flying capacitor voltages, along with load current data and switching patterns, eliminating the need for any additional sensors. The detection process takes less than a fundamental period of the inverter output frequency to diagnose any faulty switch accurately. Experimental results validate the robustness and effectiveness of the proposed DT health monitoring method across various operating conditions.

The extended Kalman filter (EKF) is widely applied in the permanent magnet synchronous motor (PMSM) position estimation method. However, the estimation accuracy will be degraded, when measurement noise is not 0-mean random noise. To solve this problem, this article proposes an EKF algorithm with moving horizon estimation (MHE) to estimate the rotor position of PMSM more accurately. The proposed MHE EKF algorithm uses the concept of a moving time-domain window to estimate the motor operating status by integrating the window information of the N moments. By establishing a cost function and adding random noise to replace the measurement error, the prediction problem is transformed into an optimization problem. The simulation and experiment results show that this algorithm can effectively improve the accuracy of estimation position.

As a major components of modern transportation systems, the highway transportation system is one of the most significant carbon emission contributors in the entire transportation sector. Although there are numerous distributed renewable resources along the highway system, their diversified inherent characteristics and heterogeneous operational conditions present challenges to fully utilize those clean energy resources for the highway transportation system. Towards the carbon neutrality targets, it is important to investigate the integrated multi-energy conversion, control, operation and planning for the self-sustained highway transportation system from an energy-transportation nexus perspective. Therefore, the coordinated interaction of the various components of the highway transportation energy system becomes essential. This entails not only advancements in energy conversion technologies but also the development of intelligent control systems, sustainable operational models, and forward-thinking planning to enable self-sustained energy ecosystems along the highway.

In this article, multiple advanced low-switching-frequency modulation and control schemes are investigated for dual three-phase permanent-magnet synchronous motor (PMSM) drives. The modulation schemes under investigation include multisampling space vector modulation (MS-SVM), selective harmonic elimination pulsewidth modulation (SHEPWM), and synchronous optimal pulsewidth modulation (SOPWM), whereas the control schemes include complex vector control, model predictive control (MPC), and flux trajectory control-based model predictive pulse pattern control (MP3C). The difference between three-phase and dual three-phase PMSM drives at low switching frequencies is analyzed. Moreover, an optimal pulsewidth modulation (PWM)-based MP3C scheme is proposed for the dual three-phase PMSM, where the optimal PWM modulation and MP3C control are combined such that the optimal steady-state and dynamic control performance is achieved among the modulation and control schemes investigated. Experimental results are given to compare and validate the proposed control scheme.

Integrated onboard battery charger (IOBC) is an emerging technology that charges electric car battery packs using the same circuitry for electric propulsion, reducing the cost and weight of an electric vehicle (EV). During charging, while ensuring zero-average torque to avoid rotation, permanent magnets (PMs) synchronous motors with fractional slot concentrated winding (FSCW) may be subjected to irreversible demagnetization due to sub and super space harmonics with relatively high magnitudes. This article presents the design and optimization of six-phase surface-mounted PM (SPM) and interior PM (IPM) motors with FSCW, considering the impact of PM demagnetization during IOBC. A detailed thermal and demagnetization analysis is conducted to identify the risk of PM demagnetization during propulsion and IOBC modes. The performance and demagnetization risk for SPM and IPM motors with different power ratings used in commercial EVs are compared at various operating conditions. In the integrated charging process, grid-to-vehicle (G2V) and vehicle-to-grid (V2G) power circulations are practically implemented. Simulations are conducted using a 3-D finite element analysis. Experimental results of a 15 kW IPM motor are provided for further verification.

Aiming at extending the constant-torque region, a high-performance single-stage control strategy is proposed for the current-source inverter (CSI) fed permanent-magnet synchronous motor (PMSM) drive system in this article. Different from traditional CSI-fed motor drives, both the dc-link current and the motor speed are regulated by the CSI for single-stage operation. A novel cascaded closed-loop control structure is proposed, where the speed controller and the dc-link current controller are designed as the outer and inner loops, respectively. The input dc voltage can be boosted for higher terminal voltages of PMSM, and the constant-torque operation range is extended and the efficiency is improved for the CSI-fed drive due to the avoidance of flux-weakening operation. Moreover, the cascaded closed-loop current controller is developed, which can suppress the LC resonance excited by low-order current harmonics in the single-stage operation. To achieve the smooth transition between the two-stage operation in the low-speed region and the single-stage operation in the high-speed region, a hysteresis comparator-based switching strategy is proposed. Experiments have been conducted to verify the effectiveness of the boost feature of CSI and the proposed control scheme.

The employment of robots in numerous emerging applications, e.g., disaster rescue, nuclear waste remediation, and space exploration, is of paramount importance due to their improved safety, flexibility, and productivity. Due to the harsh environmental conditions, the robotic arm joint motors and power electronic drives are vulnerable to electrical faults and mainly contribute to joint failures. To substantially improve the reliability and robustness of the robot arms utilized in remote, hazardous, and safety-critical environments, autonomous fault-tolerant and fail-active operation for these robotic arms experiencing joint failures should be developed. In the literature, many strategies have been proposed for fault prognosis, diagnosis, and health monitoring of electric motors and drives using online data analytics of the fault signature information. Thus, this paper presents an extensive up-to-date review of joint motor types, common fault types, and robot joint fault prognostics, diagnostics, and health management. First, various joint motors are introduced and compared, considering their performance advantages, disadvantages, and wide applications. Furthermore, joint motors for collaborative robotic applications are summarized and compared as illustrative examples. After that, fault types are reviewed with a further classification by fault locations, namely, stator windings, rotors, and bearings. In addition, health monitoring techniques are classified into methods for stator winding, rotor, and bearing faults. These methods are intensively compared with respect to motor and fault types, proposed health monitoring techniques, and control strategies. Finally, conclusions and future research trends are summarized.

This study demonstrates an effective dispatching scheme of utility-scale wind power at one-hour increments for an entire day with a hybrid energy storage system consisting of a battery and a supercapacitor (SC). Accurate forecasting of wind power is crucial for generation scheduling and economic operation. Here, wind speed is predicted by one hour ahead of time using a multilayer perceptron Artificial Neural Network, which exhibits satisfactory performance with good convergence mapping between input and target output data. Furthermore, an adaptive neuro-fuzzy inference system is employed to devise a state of charge (SOC) controller to accurately estimate the grid reference power (P$_\mathrm{Grid,ref}$) for each one-hour dispatching period. This type of desired P$_\mathrm{Grid,ref}$ estimation is critical to ensure the energy storage system (ESS) completes each dispatching period with its starting SOC and has adequate capacity available for next-day operation. Also, the particle swarm optimization technique is implemented to optimize the life cycle cost of the ESS based on its depth of discharge usage, which is vital for minimizing the cost of a dispatchable wind power scheme. The actual wind speed data of four different days as a representative of each season recorded at Oak Ridge National Laboratory are utilized in the simulations to provide a realistic economic assessment for dispatching the wind power.

With the growing adoption of both residential and commercial electric vehicles (EV) and the rapid deployment of EV charging stations, it is of paramount importance to assess the potential overloading impact of intensive EV charging on the operation and planning of power distribution systems. Targeting at the west Kentucky rural area, this research leverages the Distribution Resource Integration and Value Estimation (DRIVE) and HotSpotter software tools to investigate the potential impact of EV charging on the operation of regional distribution systems and the lifetime degradation of power transformers. The research outcome helps identify possible distribution system overload risks and mitigation solutions to meet future intensive EV charging necessity under assumed EV adoption scenarios. Possible overloading in the distribution systems and undervoltage violations are examined. In addition, the overload impact of EV charging is investigated by conducting a multi-physics reliability analysis of a distribution transformer.

In this article, the influence of aluminum eddy currents (AECs) in the planar switched reluctance motor (PSRM) stator array on electromagnetic properties and control performance is investigated. A model is developed to analyze the eddy current density distribution based on Maxwell’s equations, and an inductance model is derived that considers the eddy current effect. The effect of AECs on PSRM position control performance is qualitatively analyzed. The distribution of AECs and ohmic loss is verified through finite element analysis (FEA). The validity of the developed inductance model is experimentally verified. A material substitution method is proposed to eliminate the AEC. Experimental results show that the position control accuracy of the PSRM prototype is improved by an average of 6.94% after the elimination of AECs, while the motor efficiency is improved by 6.51%.

An online approach for diagnosing high-resistance connection (HRC) faults in five-phase permanent magnet synchronous motor drives is presented in this article. The development of this approach is based on a so-called “magnetic field pendulous oscillation (MFPO)” technique and symmetrical components method. Under HRC fault condition, a “swing-like” MFPO phenomenon is observed compared to the healthy condition. Furthermore, with the extracted current features in symmetrical components domain, different HRC fault types are successfully identified and distinguished. These fault types include single-phase faults, e.g., HRC fault in phase-A; two-phase nonadjacent faults, e.g., HRC fault in phase-A&C; and two-phase adjacent faults, e.g., HRC fault in phase-A&B. Meanwhile, the localization of the faulty phase/phases is also accomplished, and the fault severity is estimated. In this approach, only sensing of the phase currents is needed. Hence, the implementation cost is very low since the sensory data of the currents are typically already available in the closed-loop vector-controlled drives for control purpose and no additional sensors or related signal conditioning circuits are required. The effectiveness of the presented diagnostic approach is verified by simulations and experimental results.

A hybrid renewable energy source (HRES) consists of two or more renewable energy sources, suchas wind turbines and photovoltaic systems, utilized together to provide increased system efficiency and improved stability in energy supply to a certain degree. The objective of this study is to present a comprehensive review of wind-solar HRES from the perspectives of power architectures, mathematical modeling, power electronic converter topologies, and design optimization algorithms. Since the uncertainty of HRES can be reduced further by including an energy storage system, this paper presents several hybrid energy storage system coupling technologies, highlighting their major advantages and disadvantages. Various HRES power converters and control strategies from the state-of-the-art have been discussed. Different types of energy source combinations, modeling, power converter architectures, sizing, and optimization techniques used in the existing HRES are reviewed in this work, which intends to serve as a comprehensive reference for researchers, engineers, and policymakers in this field. This article also discusses the technical challenges associated with HRES as well as the scope of future advances and research on HRES.

In this article, a min-max model predictive control (MPC) method of planar motors is proposed for the first time to achieve robust precision position tracking, which has a low computational burden and strong capability to deal with the problems of stability, robustness, optimization, and input constraints. A state-space model with a homogeneous state equation is built to describe the dynamics of the time-varying reference trajectory. Combining the state-space model of the reference trajectory and that of the planar motor, an augmented state-space model is established to obtain an error state formulation. Then, using the error state formulation, a min-max optimal control problem subject to the constraints on bounded uncertainty, stability, and control input is developed. Moreover, applying the theory of asymptotically stable invariant ellipsoids and employing the nested invariant ellipsoids, the explicitly linear state-feedback control laws are obtained using a linear-matrix-inequalities based offline control algorithm. Finally, the min-max MPC is applied to a planar motor system developed in the laboratory for an experimentally comparative study. The results demonstrate the effectiveness of the proposed min-max MPC of planar motor for robust precision position tracking applications.

Global transportation has shifted toward electromobility to achieve net-zero emission, and in the next few decades, commercial electric aircraft is likely to become a reality. This transition has embarked on through the existing more electric aircraft (MEA), and the ultimate goal will be potentially achieved by hybrid-electric and all-electric airliners, along with green fuels, such as green hydrogen or supercritical CO2 (sCO2) and its potential Gg CO2 equivalent elimination—with or without combustion. Electric propulsion replaces conventional jet propulsors with electric fans powered by electric generators rotated by an engine, a combination of generators and energy storage, or just energy storage. An appealing idea is to distribute the electric fans along the aircraft wings or tails to improve aerodynamics, boost energy efficiency, and reduce carbon emissions and acoustic noise. Focusing on distributed electric propulsion (DEP) systems, this article reviews the state-of-the-art advancements in aircraft electrification. Three major DEP categories, i.e., turboelectric, hybrid-electric, and all-electric propulsion technologies, are investigated. Although all of them utilize electric fans as propulsors, their system structures and power generation stages are different. Hence, comprehensive considerations are required to optimize the DEP system designs. Starting with the multifarious electrical system architectures proposed in the literature, a thorough review is conducted including the system parametric specifications, design considerations of power converters, the power electronics devices’ characteristics in cryogenic conditions, and various energy storage systems. This review aims to provide a reference to researchers, engineers, and policy-makers in aviation to accelerate the progress toward future net-zero emissions.

In this article, a novel electric machine having permanent magnets (PMs) in both stator and rotor parts, and fed with dc biased phase current is proposed. The innovative characteristic of the proposed machine is that it contains multiple field excitation sources including stator PM, rotor PM. and dc component in the phase current. Thus, the exciting field can be greatly strengthened. What is more, the exciting field is flexible and adjustable thanks to the variable dc component. Therefore, the proposed machine is expected to exhibit high torque density, wide constant power operation range. This article first illustrates the basic operation principle, slot/pole combination equation, and the topology. Then, performance of six machines with different slot/pole combination is analyzed. After that, effects of several key design parameters on machine performance are researched theoretically and by finite-element method and genetic algorithm. And neural network is applied to verify the correctness of torque and torque ripple. Finally, the electromagnetic performance including flux density, back electromotive force, torque quality of an optimized machine is illustrated.

An online diagnostic approach of open-phase faults for a five-phase permanent magnet synchronous motor (PMSM) fed by a closed-loop vector-controlled drive is presented in this article. This approach is accomplished based on the magnetic field pendulous oscillation (MFPO) phenomenon, in which a significant “swing-like” pendulous oscillation in the magnetic field is observed in case of open-phase faults. According to an analysis of the signatures of MFPO patterns under faulty conditions, all possible open-phase faults are detected, including single-phase open faults, two-adjacent phase open faults, and two-nonadjacent phase open faults. Moreover, this approach is capable of localizing the faulted phase/phases by further extracting the phase angle features of MFPO angular position waveforms under faulty conditions. Meanwhile, in order to minimize the number of sensors to reduce the implementation cost of this diagnostic approach, a phase-locked loop technique is developed to overcome the fault masking difficulties associated with the compensation action of the closed-loop vector-controlled drive. As a result, this diagnostic approach only requires four current sensors and a speed sensor, which are typically already available in five-phase PMSM drive systems for control purposes. Finally, experimental results demonstrate the effectiveness of the presented approach.

The main purpose of this article is to provide an instructive review of the technological challenges hindering the road toward more electric powertrains in aircraft. Hybrid, all-electric, and turboelectric powertrain architectures are discussed as possible fuel consumption and weight reduction solutions. Among these architectures, the short-term implementation of hybrid and all-electric architectures is limited, particularly for large-capacity aircraft due to the low energy/power density levels achievable by state-of-the-art electrical energy storage systems. Conversely, turboelectric architectures with advanced distributed propulsion and boundary layer ingestion are set to lead the efforts toward more electric powertrains. At the center of this transition, power converters and high-power density electric machines, i.e., electric motors and generators, and their corresponding thermal management systems are analyzed as the key devices enabling the more electric powertrain. Moreover, to further increase the fuel efficiency and power density of the aircraft, the benefits and challenges of implementing higher voltage powertrains are described. Lastly, based on the findings collected in this article, the projected roadmap toward more electric aircraft powertrains is presented. Herein, the individual targets for each technology, i.e., batteries, electric machines, and power converters, and how they translate to future aircraft prototypes are illustrated.

This article proposes a common-mode voltage (CMV) attenuation method for the three-phase current source inverter (CSI)-fed permanent-magnet synchronous machine drive. The key of this method is to introduce an auxiliary circuit branch connected in parallel with the dc link. Based on the dedicated switching strategy, the zero-voltage-switching conditions are provided for the main switches in the CSI. In particular, the zero current vector is newly constructed without utilizing shoot-through operation in the CSI. Thus, the CMV in the traditional CSI drives is attenuated significantly. Compared with the existing research on CMV suppression, the proposed method will not compromise the modulation index range or increase output current harmonics. Meanwhile, the overshoot voltage can be clamped by the auxiliary power circuit in the dc link under open-circuit fault in the power switches. The system configuration, operating principle, analysis of operation modes, as well as the control scheme are described in detail. Both simulation and experimental results are presented to verify the performance of the proposed method.

The silicon carbide (SiC) devices have attracted more and more attention due to the capability of withstanding higher blocking voltage, higher switching frequency, and higher temperature. However, challenges for SiC devices applied in voltage-source-inverter fed motor drives such as electromagnetic interference (EMI) issues and limited over-current capability still limit the further application of SiC devices. In this article, a novel SiC devices based zero-voltage-switching (ZVS) current-source-inverter (CSI) is proposed for permanent-magnet synchronous motor (PMSM) drive. The key is to propose an auxiliary resonant circuit, which achieves ZVS conditions for all switches in power circuits and reduces the dv/dt of high speed SiC devices. The resonant capacitor in the auxiliary circuit can clamp overvoltage caused by possible open-circuit faults. To further reduce the EMI, the random switching frequency pulsewidth modulation is designed for the proposed CSI motor drive. The system configuration, working principle, circuit design, and control schemes are described in detail. Both simulations and experiments are presented to verify the effectiveness of the proposed ZVS-CSI fed PMSM drive system.

High-power-density high-speed electric motors for aircraft hybrid-electric propulsion (HEP) applications require high fundamental output frequency from power inverters. Conventional silicon (Si)-based megawatt (MW)-scale power inverters typically have low switching frequency that is not sufficient to meet the dynamic and harmonic requirements for such applications. An MW-scale medium-voltage three-level active neutral-point-clamped (ANPC) inverter based on a hybrid utilization of silicon carbide (SiC) and Si power devices (i.e., “SiC+Si”) has been developed for high-speed HEP drive applications, which has a rated output frequency of 1.4 kHz at 1-MW active power. To evaluate the power capability and efficiency of this ANPC inverter in the laboratory, power pump-back tests need to be carried out. In this article, control methods for single- and three-phase inverter pump-back tests have been developed to evaluate the performance of such high-frequency propulsion drives. The implementation and experimental results are presented to verify the efficacy of the control methods and the performance of the MW-scale “SiC+Si” ANPC inverters.

This article proposes a predictive position control of long-stroke planar motors to achieve micrometer-scale positioning under long-stroke time-varying trajectory tracking for use in high-precision positioning applications. The motivation consists in the potential application of model predictive control in long-stroke planar motors for high-precision positioning systems. This control is the first of its kind for planar motors. A dynamic model of a long-stroke planar motor developed in the laboratory is built, and then a predictive model is established to predict future positions of the motor. An additional term is introduced to a cost function to improve the positioning accuracy, which provides an output feedback control action to the motor for reducing the model error of the predictive model. By minimizing the cost function, an analytically explicit solution of the optimal control sequence is obtained, which makes the computational burden of the controller low. The stability of the control system is discussed based on the closed-loop state-space model. Moreover, the selection of stable control parameters is theoretically given. Simulation and experimental results demonstrate the effectiveness of the proposed control method of long-stroke planar motors for use in high-precision positioning applications.

In this article, an improved pulsewidth modulation (PWM) strategy is introduced for three-level active neutral point clamped converters based on a hybrid configuration of silicon carbide (SiC) mosfets and silicon (Si) insulated gate bipolar transistor (IGBTs). Compared with the conventional PWM strategies in the literature, this proposed PWM strategy enables the SiC switches only to interface with small commutation loops, thus the turn-off voltage overshoots caused by the parasitic loop inductance and high di/dt are much lower. Soft switching is achieved across all the IGBTs, and the switching losses of the converter only dissipate from the SiC mosfets, leading to high efficiency of the converter. Also, with this improved PWM strategy, the conduction loss at zero voltage output of this converter is reduced due to the turn-on of two parallel conduction paths. Furthermore, this proposed PWM strategy can protect the body diodes of the SiC mosfets from conducting large load current. All these advantages with the proposed PWM strategy are experimentally verified in a megawatt-scale three-phase three-level “SiC+Si” hybrid active neutral point clamped inverter developed for electric aircraft propulsion applications.

In this article, a predictive position control method based on a novel input-constrained nonlinear dynamic model (NDM) is proposed for time-varying position tracking of planar motors. The motivation lies in the possible utility of this method for motion systems. This method uses NDM subject to input constraint to deal with actuator saturation rather than uses a constrained optimization problem, such that it differs from conventional model predictive control. The NDM is represented in state–space equations (SSEs) to describe dynamic behaviors of the system constituted by the planar motor and an input saturation module. In contrast to linear SSEs, this model has the same linear vector-matrix form; the difference is that it applies saturation functions of states to replace states of state equation in linear SSEs for representing nonlinearity. By employing a self-designed neural network, the parameters of this model are determined via experimental sample data. With this model, a nonlinear multistep predictive model subject to input constraint is developed. Additionally, an explicitly analytical state feedback control law is approximately deduced by solving an unconstrained optimization problem subject to the nonlinear predictive model. Finally, simulation and experimental results show the effectiveness of the proposed method.

One of the major failure causes in the power modules comes from the severe thermal stress in power semiconductor devices. Recently, some local control level methods have been developed to balance the power loss, dealing with the harsh mission profile, in order to reduce the thermal stress. However, there is not any specific system level strategy to leverage these local control level methods responding to the multiple inverters situation. Besides, the impacts of these methods on the thermal cycle and lifetime of the power modules in the long-term time scale have not been evaluated and compared yet. Hence, in this article, a centralized thermal stress oriented dispatch (TSOD) strategy is proposed to take full advantage of these local control level methods, including the switching frequency variation and the reactive power injection, to reduce the thermal stresses for multiple inverters. In addition to the PI controller, the finite control set model predictive control (FCS-MPC) is also explored to synergize with the proposed strategy. The results from the real-time model-in-the-loop testing on a four-paralleled-inverters platform, the reliability assessment, and the experiments all validate the effectiveness of the proposed centralized TSOD strategy on the thermal stress reduction.

Finite control set model predictive control (FCS-MPC) has been widely studied and applied to the power converters and motor drives. It provides the power electronics system with fast dynamic response, nonlinear system formulation, and flexible objectives and constraints integration. However, its variable switching frequency feature also induces severe concerns on the power loss, the thermal profile, and the filter design. Stemming from these concerns, this article investigates the variable switching frequency characteristics of FCS-MPC on the grid-connected inverters. An intuitive relationship between the switching frequency and the magnitude of the converter output voltage is proposed through the geometry analysis, where the switching frequency is maximized when the converter output voltage is around one-third of the DC bus voltage and decreasing when the output voltage moves away from this value. The impacts of this variable switching frequency property on the power loss and current harmonics are also analyzed. Simulation and experimental results both verify the proposed property. With this intrinsic property, FCS-MPC can autonomously achieve a less-varying temperature profile of power modules and an improved reliability compared with the conventional control strategy.

In this article, a novel soft-switching current-source rectifier (CSR) based bidirectional on-board charger (OBC) system is proposed for electric vehicles (EVs) comprising multiple battery sets. Besides the CSR's inherent advantages of higher-quality input voltage waveforms, enhanced short-circuit-current tolerant capability and long lifetime of dc choke, the cascaded configuration of dc choppers can implement the higher dc-link voltage with multiple low-voltage battery sets, and the low-voltage devices can be used. With the auxiliary resonant circuit in dc link, the soft-switching operation can be achieved for all power switches in the proposed power conversion circuits. Moreover, the high dv/dt caused by high-speed switching silicon carbide devices can be reduced with the capacitor in the auxiliary circuit. The collaborative operation strategy is proposed for the CSR and the dc choppers, which enables reduction of switching frequency of dc choppers and current ripple in dc link simultaneously. The experimental results are presented to verify the performance of the proposed the OBC system.

This letter proposes a four-leg current-source inverter (CSI) fed three-phase motor drive. Different from the previous four-leg CSI inverter, the proposed configuration introduces the fourth leg in CSI, which connects to the neutral point of the motor through an extra output filter capacitor. Therefore, the proposed configuration can not only reduce the common-mode voltage (CMV) under the normal condition, but also provide the fault-tolerant operation ability under open-circuit faults in windings and switches. The dedicated space vector modulation (SVM) strategies have been designed. Compared with prior research on CMV reduction, the four-leg method has the full range of modulation index and will not increase any harmonics in the currents. Meanwhile, the fault-tolerant ability is offered, which can further enhance the reliability of the motor drive. A laboratory prototype has been built to experimentally verify the effectiveness of the proposed motor drive topology and the control schemes.

This article proposes a new position estimation method based on an unsaturated flux linkage model for planar switched reluctance motors (PSRMs). The bipolar-voltage-injection method is used to measure the flux linkage, and it is found that ripples caused by iron loss and aluminum eddy current with different amplitudes appear at the troughs of the flux curve. The effect of the losses on the flux linkage measurement is revealed in this article, and the loss compensation models are built based on the analysis. The improved flux linkage model is proposed with the loss compensation models. Then, the position estimation method is given with the improved flux linkage model. Flux linkage measurement result shows that the model with loss compensation has higher accuracy than the conventional model. Initial and planar-motion position estimation experiments are carried out for the PSRM. The initial position estimation error is from -0.4 to 0.4 mm. The planar-motion position estimation errors are from -1.1 to 1.1 mm in the X-axis and from -1.2 to 1.0 mm in the {Y-axis, and the effectiveness of the proposed flux linkage model is verified.

Aiming at tolerating common electric faults of multiphase motor drives comprehensively and minimizing the adverse impacts from the remedial scheme itself, a diagnosis-free self-healing scheme is put forward for the open-circuit faults of dual three-phase permanent-magnet synchronous motor (PMSM) drives. First, the self-healing mechanisms of dual three-phase PMSM drives are analyzed in detail. On the basis of theoretical analysis, the repressed self-healing capability of the dual three-phase PMSM drives is fully released by optimizing the current references on harmonic subspace. Since the diagnosis process is not required in the proposed self-healing scheme, the misdiagnosis problem and the prolonged damage caused by the additional time cost of diagnosis can be fundamentally avoided. The proposed self-healing scheme can be generally applied to open-switch faults, single open-phase faults, and multiple open-phase faults in the multiphase motor drives. No change is required for the machine model, modulation strategy, or control framework under different open-circuit faults. Thus, the complex transition strategies among different fault-tolerant control methods for different faults can be avoided, and the adverse impacts from the remedial scheme itself can be minimized. Experimental verification is presented to prove the validity of the proposed self-healing scheme.

Modular multilevel converters (MMCs) have been one of the most broadly used multilevel converter topologies in industrial applications, particularly in medium-voltage motor drives and high-voltage dc power conversion systems. However, due to the utilization of large amount of semiconductor devices, the reliability of MMCs becomes one of the severe challenges constraining their further development and applications. In this paper, common electrical faults of the MMC have been summarized and analyzed, including open-circuit switching faults, short-circuit switching faults, dc-bus short-circuit faults, and single line-to-ground faults on the ac side. A thorough and comprehensive review of the existing online fault diagnostic methods has been conducted. In addition, fault-tolerant operation strategies for such various fault scenarios in MMCs have been presented. All the fault diagnosis and fault-tolerant operation strategies are comparatively evaluated, which aims to provide a state-of-the-art reference on the MMC reliability for future research and industrial applications.

Flying capacitor multilevel (FCML) inverter is an attractive power converter topology which provides high-quality staircase output voltage waveforms by cascading flying capacitor cells. However, the large number of semiconductor devices utilized in the FCML inverters degrades the hardware reliability, which may constrain such converters from being applied in safety-critical applications. Targeting at open-circuit switching faults, a fast online fault diagnostic method for FCML inverters is presented. Conventional phase-shifted PWM (PSPWM), which can naturally balance the voltage across flying capacitors, is used as the modulation method in this work. Hence, to retain the simplicity feature of the PSPWM, the proposed diagnostic method is developed so that it does not require any voltage measurements of flying capacitors. Only the output AC voltage and current data along with the switching PWM signals from the microcontroller are needed to detect an open-circuit switching fault, and all such sensory data is typically available in the inverter, requiring no additional sensors or hardware for the implementation of this diagnostic method. The detection process takes 5% of the fundamental period of the inverter output signals to diagnose the faulty switch. Simulation and experimental results are presented to verify the effectiveness of the proposed diagnostic method.

Thermal stress has been identified as one of the major failure causes in power modules. Generated from the power loss, thermal stress accelerates the degradation of semiconductor devices and downgrades the system reliability. This article presents a finite control set model predictive control (FCS-MPC) oriented to reduce the power loss over the mission profile and relieve the thermal stress in power modules. Conventional control approaches including the switching frequency regulation, the reactive power injection, and the dc-bus voltage adaption show an effective progress. However, the increased control loops and complicated modulation schemes limit the system performance and practical implementation. In the proposed FCS-MPC, a secondary problem formulation is defined to reduce the power loss for the thermal stress reduction in power modules. It is simply integrated with the primary problem formulation in order to achieve the power flow control and power loss reduction simultaneously. An energy-based loss model is proposed for the loss prediction. The impact of the weightings between primary and secondary problem formulations is investigated and a most efficient weighting curve with a weighting-zones strategy is presented to design the proposed FCS-MPC. The proposed FCS-MPC is validated in the simulations and experiments. A 2.5-kW grid-tied inverter prototype is developed for the hardware testing and validation.

This study demonstrates a dispatching scheme of wind-solar hybrid power system (WSHPS) for a one-hour dispatching period for an entire day utilizing battery and supercapacitor hybrid energy storage subsystem (HESS). A frequency management approach is deployed to extend the longevity of the batteries through extensively utilizing the high energy density property of batteries and the high power density property of supercapacitors in the HESS framework. A low-pass filter (LPF) is employed to decouple the power between a battery and a supercapacitor (SC). The cost optimization of the HESS is computed based on the time constant of the LPF through extensive simulations in MATLAB/SIMULINK platform. The curve fitting and Particle Swarm Optimization approaches are applied to seek the optimum value of the LPF time constant. Several control algorithms as a function of the battery state of charge are developed to achieve accurate estimation of the grid reference power for each one-hour dispatching period. This estimation helps to minimize the energy storage cost, in addition to ensuring that the HESS has sufficient capacity for next-day operation. The optimum value of depth of discharge for HESS considering both cycling and calendar expenses has also been investigated for the best competitive energy storage cost for hourly dispatching the power of the WSHPS. This research also presents an economic comparison to investigate the significance of using different types of energy storage for hourly dispatching the WSHPS. The simulation results show that the presented HESS is superior to battery or SC-only operation.

An accurate mover position is important for a planar switched reluctance motor (PSRM) to achieve precision positioning; however, position sensors are susceptible to the influence from harsh conditions and are relatively expensive. In this article, an assistant-mover-based position estimation method is proposed to increase the reliability and reduce the cost of a PSRM system. The method is based on a mapping relationship between the flux density and position of the assistant mover. First, the configuration of the assistant movers is presented. Then, an analytical model of the flux density of the assistant mover is developed by using an equivalent magnetic circuit method. Based on the analytical model, the parameters of the assistant mover are determined. According to the flux density characteristics, a position estimation algorithm with the advantages of not requiring previous experimental data, simple computation, and small memory consumption is developed. Moreover, considering the deviation in the characteristics of each assistant mover, a compensation strategy is proposed to obtain better position estimation accuracy. Finally, the proposed method is implemented with the PSRM system. The effectiveness of the proposed position estimation method is verified experimentally.

Medium voltage DC(MVDC) system is considered as a promising technology to improve the efficiency and power density of electric aircraft propulsion(EAP) drives. To adapt to the MVDC voltage level and achieve high drive performance, a five-level active neutral point clamped(5L-ANPC) inverter consisting of three-level ANPC and flying capacitor circuits is investigated, which possesses higher voltage capability, lower output harmonics, as well as mitigated dv/dt and common-mode voltage. To fulfill the requirements of high-speed operation and pursue further enhanced efficiency and power density of the inverter for the next-generation EAP drives, Silicon Carbide(SiC) semiconductor devices are considered for implementing the 5L-ANPC inverter. However, the large commutation loops associated with certain switching states of the inverter lessen the benefits of configuring all the switches as SiC devices. As a result, a hybrid Si/SiC 5L-ANPC inverter is developed with a synchronous optimal pulse(SOP) width modulation strategy for controlling the switches in cell 2 and finite-control-set model predictive controller(FCS-MPC) for those in cell 3 of the inverter. Consequently, in the proposed topology, the SiC devices are merely used for the high-frequency switches in cell 3 and the rest of the low-frequency switches are configured with Si IGBTs. This Si/SiC hybrid ANPC inverter concurrently provides high efficiency and low implementation cost at high-speed operation mode. Simulation and experimental results are provided to verify the effectiveness of the proposed hybrid inverter.

The Multilevel inverters (MLIs) are a new breed of power electronics converters. They are primarily used for the conversion of dc power to ac power. The two-level inverters are conventionally used to obtain ac power, but it requires operating the switches under very high switching frequency. Besides, the two-level inverter necessitates the use of LC filters with the switches operating under high dv/dt stress. The MLIs offer the advantage of utilizing several dc voltage sources to generate a stepped ac waveform with the proper arrangement of switches. Investigation of a Transistor Clamped T Type H-Bridge Multilevel Inverter (TC-TT-HB-MLI) with Inverted Double Reference Single Carrier PWM Technique (IDRSCPWM) for Renewable Energy Applications are discussed in this paper. A PV source is taken as an input to the TC-TT-HB-MLI. For different modulation indices like 0.85, 1 and 1.25, the FFT analysis is performed and presented, which corresponds to the variations in the irradiations from solar energy. A single unit of the TC-TT-HB-MLI is extended to a generalized MLI structure named Generalized Transistor Clamped T-Type H-Bridge Multilevel Inverter (GTC-TT-HB-MLI). The significant benefits of GTC-TT-HB-MLI are the multiple numbers of reductions in the switch count, and driver circuit counts for a higher number of MLI levels. Fast Fourier Transform (FFT) analysis is carried out on the MLI output to calculate the total harmonics distortion (THD). The experimental verification is performed using SPARTAN 3E-XCS250E; the gate signals are generated and provided to the switches.

In this paper, diagnosis and tolerant control schemes have been studied for common electrical faults in T-type three-level inverter fed dual-three phase permanent magnet synchronous motor (PMSM) drives for safety-critical applications. Based on vector space decomposition and double three-phase space vector modulation, diagnostic and tolerant control methods have been developed comprehensively for open-phase faults, open-switch faults, and short-switch faults in T-type three-level inverter fed dual-three-phase PMSM drives, in such way that misdiagnosis of different faults sharing similar faulty features can be avoided. In particular, a two-step diagnostic scheme is proposed in order to simplify the diagnostic process. The first step is to identify the faulty phase and fault category by analyzing current trajectories on harmonic subspace, and the second step is to determine the specific fault type in a small fault-searching area obtained from the first step. In the aspect of fault-tolerant control, a novel current compensation method is proposed for open-phase fault without changing the machine model, space vector diagram, and control framework. Open-switch faults and short-switch faults are tolerated by making full use of the remaining vectors after faults. The validity of the proposed fault diagnosis and tolerance schemes has been verified by experiments.

THE electric machine systems have been utilized widely and played important roles in many industrial applications. The high-reliability electric machine systems and fault-tolerant operation technology are critical enablers for the industry to unlock significant improvements in system maintainability, total life-cycle costs, and overall system reliability. The high-reliability electric machine systems offer features of simple and robust structures, and low failure rate. When unavoidable failures occur, the faulty parts in electric machine systems should be diagnosed accurately and isolated effectively. The fault-tolerant strategies can help the system maintain operation performance in some certain aspects, and thus keep the total system working continuously.

A comparative study of five-phase outer-rotor flux-switching permanent magnet (FSPM) machines with different topologies for in-wheel traction applications is presented in this paper. Those topologies include double-layer winding, single-layer winding, C-core, and E-core configurations. The electromagnetic performance in the low-speed region, the flux-weakening capability in the high-speed region, and the fault-tolerance capability are all investigated in detail. The results indicate that the E-core FSPM machine has performance advantages. Furthermore, two kinds of E-core FSPM machines with different stator and rotor pole combinations are optimized, respectively. In order to reduce the computational burden during the large-scale optimization process, a mathematical technique is developed based on the concept of computationally efficient finite-element analysis. While a differential evolution algorithm serves as a global search engine to target optimized designs. Subsequently, multiobjective tradeoffs are presented based on a Pareto-set for 20 000 candidate designs. Finally, an optimal design is prototyped, and some experimental results are given to confirm the validity of the simulation results in this paper.

This paper introduces a general method for determination of the most suitable winding configurations for five-phase flux-switching permanent magnet (FSPM) machines, associated with feasible stator/rotor-pole combinations. Consequently, the effect of winding configurations on the performance of a five-phase outer-rotor FSPM machine is thoroughly investigated, including non-overlapping concentrated windings (single-layer, double-layer, and multi-layer) as well as distributed winding. The electromagnetic characteristics in the low-speed region, the flux-weakening capability in the high-speed region, and the fault-tolerant capability under faulty situations are evaluated and compared in detail. This work shows that compared with the conventional single-layer or double-layer concentrated windings, the FSPM machine with multi-layer type winding exhibits lower torque ripple and losses. Meanwhile, the motor with distributed windings possesses higher torque density and larger inductance. Finally, a prototype is manufactured, and the analysis results are validated by experiments.

A hybrid-electric propulsion system is an enabling technology to make the aircraft more fuel saving, quieter, and lower carbide emission. In this article, a megawatt (MW) scale power inverter based on a three-level active neutral-point-clamped (3L-ANPC) topology will be developed. To achieve high efficiency, the switching devices operating at carrier frequency in the power converter are configured by the emerging silicon carbide (SiC) metal-oxide-semiconductor field-effect transistors, while the conventional silicon (Si) insulated-gate bipolar transistors are selected for switches operating at the fundamental output frequency. To obtain high power density, dc bus voltage is increased from the conventional 270 V to medium voltage of 2.4 kV to reduce cable weight. Also, unlike the traditional 400 Hz dominated aircraft ac systems, the rated fundamental output frequency here is boosted to 1.4 kHz to drive the high-speed motor, which helps further to reduce the motor weight. Main hardware development and control modulation strategies are presented. Experimental results are presented to verify the performance of this MW-scale medium-voltage “SiC+Si” hybrid 3L-ANPC inverter. It is shown that the 1-MW 3L-ANPC inverter can achieve a high efficiency of 99% and a high power density of 12 kVA/kg.

High slew rate of the line voltage (dv/dt) has been a concern for power inverters based on the emerging wide bandgap switching devices, such as silicon carbide (SiC) MOSFETS. Particularly, for SiC-based power inverters feeding electric machines interconnected with long cables, there could be more severe insulation stress on the stator windings in electric machines, due to the higher dv/dt output from the SiC inverters. Compared to the conventional lower voltage electric transportation applications (e.g., 270 V dc), higher dc bus voltage of 500-600 V can dramatically reduce cable weight and systematic copper losses, hence improve the power density and efficiency of power converters. However, high dc bus voltage further increases the dv/dt level in the converter ac line voltages. Driven by the necessity of developing SiC inverters with 500 V dc bus in electric transportation applications while attenuating the dv/dt stress to a low level, this paper presents a multi-domain design approach for dv/dt filters that comprehensively considers the constraints in electrical, magnetic, and thermal domains. Experimental results based on a 75 kW SiC inverter are provided to verify the efficacy of this design approach.

A novel fault-tolerant three-level power converter topology, named advanced three-level active T-Type (A3L-ATT) converter, is introduced to increase the reliability of multilevel power converters used in safety-critical applications. This new fault-tolerant multilevel power converter is derived from the conventional T-Type converter topology. The topology has significantly improved the fault-tolerant capability under any open circuit or certain short-circuit faults in the semiconductor devices. In addition, under healthy condition, the redundant phase leg can be utilized to share overload current with other main legs, which enhances the overload capability of the converter. The conduction losses in the original outer devices can be reduced by sharing the load current with the redundant leg. Moreover, unlike other existing fault-tolerant power converters in the literature, full output voltages can be always obtained in this proposed A3L-ATT converter during fault-tolerant operation. A 13.5-kW ATT-A3L converter prototype was developed and constructed using silicon carbide MOSFETs. Simulation and experimental results were obtained to substantiate the theoretical claims of this new fault-tolerant power converter.

This paper investigates the comparative design optimizations of a five-phase outer-rotor flux-switching permanent magnet (FSPM) machine for in-wheel traction applications. To improve the comprehensive performance of the motor, two kinds of large-scale design optimizations under different operating conditions are performed and compared, including the traditional optimization performed at the rated operating point and the optimization targeting the whole driving cycles. Three driving cycles are taken into account, namely, the urban dynamometer driving schedule (UDDS), the highway fuel economy driving schedule (HWFET), and the combined UDDS/HWFET, representing the city, highway, and combined city/highway driving, respectively. Meanwhile, the computationally efficient finite-element analysis (CE-FEA) method, the cyclic representative operating points extraction technique, as well as the response surface methodology (in order to minimize the number of experiments when establishing the inverse machine model), are presented to reduce the computational effort and cost. From the results and discussion, it will be found that the optimization results against different operating conditions exhibit distinct characteristics in terms of geometry, efficiency, and energy loss distributions. For the traditional optimization performed at the rated operating point, the optimal design tends to reduce copper losses but suffer from high core losses; for UDDS, the optimal design tends to minimize both copper losses and PM eddy-current losses in the low-speed region; for HWFET, the optimal design tends to minimize core losses in the high-speed region; for the combined UDDS/HWFET, the optimal design tends to balance/compromise the loss components in both the low-speed and high-speed regions. Furthermore, the advantages of the adopted optimization methodologies versus the traditional procedure are highlighted.

This paper proposes a position estimation method for a planar switched reluctance motor (PSRM). In the method, a second-order sliding mode observer (SMO) is used to achieve sensorless control of a PSRM for the first time. A sensorless closed-loop control strategy based on the SMO without a position sensor for the PSRM is constructed. The SMO mainly consists of a flux linkage estimation, an adaptive current estimation, an observing error calculation, and a position estimation section. An adaptive current observer is applied in the current estimation section to minimize the error between the measured and estimated currents and to increase the accuracy of the position estimation. The flux linkage is estimated by the voltage equation of the PSRM, and the estimated flux linkage is then used to estimate the phase current in the adaptive current observer. To calculate the observing error of the SMO using the measured and estimated phase currents, the observing error of the thrust force is introduced to replace the immeasurable state error of the position and speed of the mover. The sliding surface is designed based on the error of the thrust force, and stability analysis is given. Once the sliding surface is reached, the mover position is then estimated accurately. Finally, the effectiveness of the proposed method for the PSRM is verified experimentally.

This paper presents the design, control, and experimental performance evaluation of a long-stroke planar switched reluctance motor (PSRM) for positioning applications. Based on comprehensive consideration of the electromagnetic and mechanical characteristics of the PSRM, a motor design is first developed to reduce the force ripple and deformation. A control scheme with LuGre friction compensation is then proposed to improve the positioning accuracy of the PSRM. Furthermore, this control scheme is proven to ensure the stable motion of the PSRM system. Additionally, the response speed and steady-state error of the PSRM system with this control scheme are theoretically analyzed. Finally, the experimental results are presented and analyzed. The effectiveness of the precision long-stroke motion of the PSRM and its promise for use in precision positioning applications are verified experimentally.

This paper presents the operation principle and benefits of a novel power converter topology named three-level two-stage decoupled active neutral point clamped (3L-TDANPC) converter, which is implemented based on a hybrid utilization of silicon (Si) insulated gate bipolar transistors (IGBTs) and silicon carbide (SiC) metal-oxide semiconductor field-effect transistors (mosfets). The 3L-TDANPC converter can achieve high efficiency with limited number of SiC mosfet modules while keeping balanced loss distribution among the switching devices, which helps increase the converter power ratings. In addition, in this 3L-TDANPC converter, the SiC mosfet has a potential to ride through short-circuit fault because of the presence of Si IGBTs. The key challenges that are associated with system resonant current are investigated and the methods to damp such resonant current are proposed and explained in detail. The simulation and experimental results based on a 1-MW 3L-TDANPC converter prototype confirm the expected benefits of this proposed converter and the effectiveness of the proposed resonant current damping methods.

A resilient fault-tolerant silicon carbide (SiC) three-level power converter topology is introduced based on the traditional active neutral-point-clamped converter. This novel converter topology incorporates a redundant leg to provide fault tolerance during switch open-circuit faults and short-circuit faults. Additionally, the topology is capable of maintaining full output voltage and maximum modulation index in the presence of switch open and short-circuit faults. Moreover, the redundant leg can be employed to share load current with other phase legs to balance thermal stress among semiconductor switches during normal operation. A 25-kW prototype of the novel topology was designed and constructed utilizing 1.2-kV SiC metal-oxide-semiconductor field-effect transistors. Experimental results confirm the anticipated theoretical capabilities of this new three-level converter topology.

This paper proposes a nonlinear flux linkage model in 2-D plane for the planar switched reluctance motor (PSRM). The inputs of the proposed model are the 2-D positions and the current, and the output is the flux linkage. The proposed model is established via a cascade-forward backpropagation neural network (CFNN). The designed CFNN consists of four layers: one input layer, two hidden layers, and one output layer. The first hidden layer has 20 neurons with a tan-sigmoid transfer function, and the second hidden layer has 20 neurons with a log-sigmoid transfer function. The output layer is a pure linear layer. The sample set with 179 755 samples is obtained experimentally in a dSPACE-based PSRM system by applying the dc excitation method. The sample set is divided into three sets. 35% and 30% of the samples are randomly chosen as the training sample set and validation sample set, respectively, and the remaining samples are utilized as the test sample set to assess the generalization performance of the CFNN-based model. According to the results of the test sample set, the maximum relative error is 11.05% and the mean relative error is 0.42% when the current ranges from 1 to 9 A. The CFNN has the capability to build a multi-input nonlinear model. The CFNN-based model is capable of reflecting the variations of flux linkage in 2-D plane caused by manufacturing tolerances. The effectiveness of the CFNN-based model is finally verified.

Hybrid switches configured by paralleling Silicon (Si) Insulated Gate Bipolar Transistors (IGBT) and Silicon Carbide (SiC) Metal-Oxide Semiconductor Field-Effect Transistors (MOSFET) have been verified to be a high-efficiency cost-effective device concept. In this paper, a current-dependent switching strategy is introduced and implemented to further improve the performance of Si/SiC hybrid switches. This proposed switching strategy is based on a comprehensive consideration of reducing device losses, reliable operation, and overload capability. Based on the utilization of such Si/SiC hybrid switches and the proposed switching strategy, a 15-kW single-phase H-bridge inverter prototype was implemented and tested in the laboratory. Simulation and experimental results are given to verify the performance of the hybrid switches and the new switching strategy.

On-line condition monitoring is of paramount importance for multilevel power converters used in safety-critical applications. A novel on-line nonintrusive diagnostic method for detecting open-circuit switch faults in silicon carbide (SiC) metal-oxide-semiconductor field-effect transistors (MOSFETs)-based T-type multilevel converters is introduced in this paper. The principle of this method is based on monitoring the abnormal variations of the dc-bus neutral-point current in combination with the existing information on instantaneous switching states and phase currents. Advantages of this method include faster detection speed and simpler implementation compared to other existing diagnostic methods in the literature. Moreover, this diagnostic method is immune to the disturbances of inverter's dc-bus voltage unbalance and load unbalance. In this method, only one additional current sensor is required for measuring the dc-bus neutral-point current; therefore, the implementation cost is low. Simulation and experimental results based on a lab-scale 20 kVA adjustable speed drive with a three-level SiC T-type inverter validate the effectiveness and robustness of this novel diagnostic method.

The performance of a novel three-phase four-leg fault-tolerant T-type inverter topology is introduced in this paper. This inverter topology provides a fault-tolerant solution to any open-circuit and certain short-circuit switching faults in the power devices. During any of the fault-tolerant operation modes for these device faults, there is no derating required in the inverter output voltage or output power. In addition, overload capability is increased in this new T-type inverter compared to that in the conventional three-level T-type inverter. Such increase in inverter overload capability is due to the utilization of the redundant leg for overload current sharing with other main phase legs under healthy condition. Moreover, if the redundant phase leg is composed of silicon carbide metal-oxide-semiconductor field-effect transistors, quasi-zero-voltage switching, and zero-current switching of the silicon insulated-gate bipolar transistors (IGBTs) in the conventional main phase legs can be achieved at certain switching states, which can significantly relieve the thermal stress on the outer IGBTs and improve the whole inverter efficiency. Simulation and experimental results are given to verify the efficacy and merits of this high-performance fault-tolerant T-type inverter topology.

The proposed hybrid method combines computationally efficient finite-element analysis (CE-FEA) with a new analytical formulation for eddy-current losses in the permanent magnets (PMs) of sine-wave current-regulated brushless synchronous motors. The CE-FEA only employs a reduced set of magnetostatic solutions yielding substantial reductions in the computational time, as compared with the conventional FEA. The 3-D end effects and the effect of pulsewidth-modulation switching harmonics are incorporated in the analytical calculations. The algorithms are applied to two fractional-slot concentrated-winding interior PM motors with different circumferential and axial PM block segmentation arrangements. The method is validated against 2-D and 3-D time-stepping FEA.

Thermal management plays a critical role in the performance of the power electronic converters. Immersion cooling, as a new promising thermal management solution for power electronics, can significantly improve the efficiency, power density, and reliability of power converters. In this paper, based on the simulation and experimental investigations, the efficiency improvement of an immersion cooled Silicon Carbide (SiC) traction inverter is characterized in comparison to the scenario based on conventional cooling solution with heatsinks and fans. It shows that the peak efficiency of the immersion cooled 5-kW 2-level SiC inverter can be improved by up to 0.16%, and the semiconductor hotspot temperature is significantly reduced by 9.6 °C, enabling much improved power cycling lifetime.

Robots have shown promising prospect in numerous applications, such as space exploration and disaster rescue. Due to the harsh environmental conditions (e.g., high temperature) in many applications, motor drive systems in the robotic arms are vulnerable to hardware failures such as inverter switching aging or faults. To address this challenge and avoid significant downtime cost, a digital twin based online health monitoring model, is developed for diagnosing potential switching faults that could occur to the robotic brushless DC (BLDC) motor drives. Specifically, the online digital twin health monitoring model is based on a dynamic neural network (DNN). Various DNN architectures have been tested to determine the best trade-off between the model accuracy and computational efficiency, which is to ensure that the proposed model can be embedded into a microprocessor and used in real-time applications. Finally, the efficacy of the proposed DNN-based digital twin approach is validated with testing data in a BLDC motor-drive prototype.

This paper proposes a novel multi-input Integrated Charger Inverter (ICI) topology with Galvanic isolation for electric vehicles (EV), capable of performing driving, regenerative braking, charging and vehicle-to-grid operation. Through multifunctionality, the proposed EV powertrain architecture reduces the size, weight, volume, and cost of the EV, which in turn translates to significant cost savings. The integrated dual-active bridge (DAB) in series with the traction inverter facilitates galvanic isolation and a flexible interface to the battery pack that can be expanded to higher voltages with advancing technologies. The bi-directional power flow capability of the proposed ICI architecture advances the role of EVs as active participant of the grid management through Vehicle-to-Grid (V2G) and Grid-to-Vehicle (G2V) functions. Simulation and experimental results are presented in the paper.

This paper aims to develop a high-frequency distributed model of the stator windings of permanent magnet synchronous machines (PMSM) fed by wide bandgap (WBG) drives with long cables. Specifically, the high-frequency distributed models of PMSM stator windings are investigated in the Ansys Electronics Desktop, and the WBG voltage source inverter and its PWM strategy are implemented in Ansys Maxwell Circuit. Distributed prameter circuit models are constructed to examine the nonlinear high-frequency surge voltage distribution in the stator windings of an interior PMSM. Moreover, a finite element model is used to extract the distributed parameters for the high-frequency modeling of the PMSM stator windings. The proposed high-frequency models are developed by calculating the winding parasitic capacitance matrix using the electrostatic solver. After that, the electrostatic and magnetic solvers are coupled by using the calculated capacitance in the magnetic solver. Finally, the induced overvoltage across the motor stator windings are investigated with a novel adaptive impedance coil (AIC) overvoltage mitigation method.

This research focuses on the development of an ultra-compact and high-efficiency quad-active-bridge (QAB) DC-DC multiport converter, which can be used to interconnect photovoltaic (PV) panels, battery energy storage (BES), and electric vehicles (EVs) with a DC distribution grid. Emerging gallium nitride (GaN) switching devices are utilized to achieve high switching frequency, high efficiency, and high power density. Additionally, a multi-winding planar transformer is employed in the QAB converter to provide galvanic isolation and interconnect different power ports for flexible power flow management. Single-phase shift (SPS), extended-phase shift (EPS), and dual-phase shift (DPS) modulation strategies are investigated and compared to regulate the power flow in various operating modes. Electrothermal modeling and simulation of the QAB converter are conducted, and a 15 kW GaN-based QAB converter prototype is developed for experimental validation.

Solid-state transformers (SSTs) have multiple advantages compared to conventional bulky electromagnetic transformers, including higher efficiency, higher power density, and improved power quality. However, hardware reliability has been a challenge constraining broad applications of SSTs. Such reliability concern mainly arises from a large number of semiconductor switches utilized in SSTs. To address this challenge, an innovative online diagnostic method for open-circuit switch faults will be presented for a multiport SST system, which possesses four isolated power ports to interconnect various energy sources. Specifically, in this new diagnostic method, the variations of the high-frequency transformer AC current and voltage will be monitored and analyzed under various switching patterns, in order to identify potential switch faults with a fast diagnostic speed. Simulation and experimental results are presented to characterize and validate the proposed open-circuit fault diagnostic method.

The transition to electric vehicles (EVs) needs advanced motor and drive technologies optimized for desired traction performance. When designing an electric motors for EV applications, numerous factors need to be considered, including high reliability, high power density, low cost, high torque density, high efficiency over wide operation regions, and low torque ripple. As traditional three-phase motor designs face increasing challenges in meeting these performance goals, multiphase motor designs are becoming increasingly attractive, but the related design optimization has not been thoroughly investigated. Multiphase induction motors (IMs) are among the best rare-earth free traction motors for EV applications. In this paper, the design and multi-objective optimization of a nine-phase IM is presented, shedding light on the motor performance during rated and peak loading conditions. Moreover, the motor performance at the maximum speed is considered to ensure that practical EV constraints are met. The design optimization process is developed using Ansys Electronics Desktop and Ansys optiSLang. Finally, intensive finite element simulations are carried out to validate the superiority of the optimal design.

This paper presents the thermal characterization of Gallium Nitride (GaN) transistors based Quad-Active-Bridge (QAB) converters with a novel stationary liquid immersion cooling technique. This QAB multiport converter interconnects photovoltaic (PV) panels, battery energy storage (BES), electric vehicles (EVs), and DC grid. To provide a cost-effective cooling solution with improved dielectric insulation capability, the GaN QAB converter is immersed into a dielectric coolant with no pump and heat exchanging units. Multi-physics analysis is conducted to characterize the thermal performance of the stationary immersion cooled converter, which shows satisfactory thermal management capability compared to the conventional air cooling methods. The GaN QAB converter's ultra-compact footprint complements the cooling benefits, supporting reliable high-frequency operation. The findings confirm stationary immersion cooling as a viable solution for compact, high-performance GaN power converters in emerging applications such as electric vehicles and data centers.

This paper investigates the overvoltage spikes in motor drive systems caused by fast-switching transistors, e.g. SiC-MOSFETs. These fast-switching devices produce high-frequency overvoltage spikes that are unevenly distributed across the stator windings, resulting in non-uniform stress on the windings’ insulation. This uneven stress arises from higher leakage currents in the first turns and coil, attributed to stray capacitances between the stator windings and the motor frame. Therefore, the most significant overvoltage stress occurs in the first coil, which is located closest to the motor terminals. Such stress can cause insulation breakdown and inter-turn short-circuit faults. To address this, the paper discusses an adaptive surge impedance technique, aimed at reducing stress in the first coil of each phase. This technique employs a parallel circuit incorporating an analog voltage sensor for detecting overvoltage onset and a GaN transistor, paired in series with a ceramic capacitor. This setup specifically targets high-frequency currents, thereby having no impact on the motor’s torque profile. Given the high-temperature robustness of GaN components and the reliability of ceramic capacitors, particularly in the pico-farad range, this solution ensures that the motor’s standard operations remain unaffected by potential component failures. Furthermore, experimental testing has demonstrated that this method mitigates the uneven distribution of high-frequency overvoltage stress across the stator windings, thereby enhancing overall system reliability.

Online health monitoring of robotic joint motor drive systems is of paramount importance for robots utilized in remote, safety-critical, and hazardous environments. Joint motors and the associated power electronic drives are prone to hardware failures in harsh environments and may yield joint failures. Brushless DC (BLDC) motors and the related inverters have been considerably used in robotic arms; therefore, numerous inverter fault diagnostic strategies for BLDC motor drives have been proposed in recent literature to enhance the system’s reliability and avoid downtime cost. In this paper, a robust fault diagnosis technique of semiconductor switches is proposed for BLDC motor drive systems in robotic applications based on the stator current signature analysis. The performance of the BLDC joint motors is investigated under inverter switches' open-circuit faults using finite element (FE) co-simulation tools. Besides the robust fault diagnosis capability, the proposed methodology is capable of identifying the faulty switch based on a knowledge table by considering several fault conditions. The robustness of the proposed technique has been verified through extensive simulations under numerous speed and load scenarios. Finally, theoretical findings are validated using the Kinova Gen3 robot arm to highlight the effect of joint faults on the robot’s reachability of desired task locations.

Aircraft electrification has received increasing attention due to the significant benefits, such as low carbon emissions, high energy efficiency, low operation cost, and reduced acoustic noise. Limitations on both the low energy density with the present battery technologies and slow battery charging speed highly affect the widespread adoption of electric aircraft, especially for megawatt-scale large aircraft. Thus, this paper presents an isolated integrated on-board battery charger (IOBC) using an existing six-phase surface-mounted permanent magnet (SPM) synchronous propulsion machine for MW-scale electric aircraft. Besides exploiting the existing powertrain apparatuses, i.e., the six-phase motor and inverter, in the propulsion and charging modes of operation, the proposed charger offers galvanic isolation to meet safety standards and code compliance. Moreover, zero average torque production during charging and unity power factor operation at the grid side can be simultaneously achieved. The proposed charger concept entails simple hardware reconfiguration to switch between the propulsion and charging modes of operation. Furthermore, this paper adopts a 36-slot/34-pole fractional slot concentrated winding (FSCW)-based SPM machine, which is designed and optimized based on the magnetic equivalent circuit (MEC) model and the multi-objective genetic algorithm (MOGA) design optimization approach, respectively. Eventually, theoretical findings are verified based on 2D and 3D finite element (FE) simulations.

The adoption of SiC MOSFETs in power converters has been increased extensively due to their distinct advantages over silicon (Si) transistors. SiC-based inverters considerably enhance the system performance in motor drives and electric vehicles due to their capability to operate at high switching frequency and, therefore, enhanced efficiency. However, the rapid switching characteristics of SiC devices introduce overvoltage challenges in electric motors. The high dv/dt associated with the short rise and fall times of SiC switches can result in voltage stress at the initial turns of the stator windings, particularly those closest to the motor input terminals. These overvoltage spikes pose a risk to the motor insulation, leading to potential degradation and incipient faults in electric motors. This paper studies a solution to address the voltage stress across the initial turns of the stator windings. This solution implements GaN-based hardware across the first coil in each motor phase to suppress the high-frequency overvoltages. The effectiveness of this approach is demonstrated using a 2hp induction motor driven by a SiC inverter through both 3m and 30m cables.

This paper proposes a fast model predictive control (FMPC) method without weighting factors and mitigated common-mode voltage (CMV) for a five-level active neutral point clamped (5L-ANPC) inverter-fed electric aircraft propulsion system with a coreless axial flux permanent magnet (CAFPM) motor. This motor is specifically designed for electric aircraft propulsion through a combined electromagnetic and thermal evaluation, benefiting from a high specific power density, efficiency, and integrated thermal management system. The proposed method utilizes the deadbeat approach to calculate the reference voltage vector and compensate for the one-time interval delay between the predicted and applied switching commands. The angle and amplitude of the reference voltage vector in the inverter’s space vector diagram are utilized to find the optimum voltage vector from a series of candidate voltage vectors with mitigated CMV values to one-sixth of the DC-link voltage. Moreover, hierarchical cost functions without weighting factors are adopted to achieve multi-objective optimizations and predict the optimum switching state. Compared to the conventional MPC method, the proposed method requires significantly shorter calculation time, leading to utilizing high sampling frequencies and improving the steady-state and dynamic performance of the motor-drive system. The performance of the proposed method is investigated in the takeoff and cruise modes of an electric aircraft’s mission profile.

Silicon Carbide (SiC) multilevel power converters have been intensively investigated in recent years due to their advantages in efficiency, power density, and others. However, for safety critical applications such as high-power electric propulsion systems, high reliability is generally a first priority to be considered during the design process. Targeted at 3-level SiC active neutral point clamped (ANPC) converters, this paper investigates the power cycling lifetime extension with various pulse width modulation (PWM) schemes. An online extension strategy of power cycling lifetime is proposed, followed by analysis and verification in electro-thermal simulations.

The triple active bridge (TAB) is a promising 3-port DC-DC converter technology which performs bi-directional power transfer with galvanic isolation. Due to intensive interactions between parameter selection and a TAB converter’s performance in efficiency, specific power, reliability, and cost, many design considerations need to be simultaneously weighed to achieve an optimal converter. In this paper, a genetic algorithm based design optimization framework is developed to enhance the performance of a TAB converter with respect to multiple design objectives. Switching devices, thermal management systems, passive components, and the design of a planar multi-winding transformer are accounted for to ensure multidisciplinary performance benefits. Initial optimization results when aiming to attain the highest specific power and efficiency are presented, and the related design trade-offs are discussed.

Soldering joint failure is a common concern in power electronic converters. It mainly occurs due to the thermal expansion of various materials during fast-switching operation, which will lead to breaks and cracks in the power components over the time such as semiconductor switches. Immersion cooling is known to reduce the device temperature in circuits and manage the heat generated by the semiconductor switches more efficiently compared to the scenario with conventional indirect cooling techniques. Therefore, temperature gradient between the power components is decreased and soldering joint aging failures will be mitigated. This paper presents multi-physics modeling and analysis of a power converter including thermal and structural analyses. The deformation and equivalent stress of the semiconductor switch model are examined. It is shown that in the immersion cooling scenario, deformation and stress are much less than those with the conventional methods.

This paper aims to develop a flexible power management approach to interconnect multiple energy resources based on an isolated, monolithic multiport DC-DC power converter. Specifically, a high efficiency, ultra-compact Quad-Active-Bridge (QAB) DC-DC converter is proposed to interconnect photovoltaic (PV), battery energy storage (BES), electric vehicle (EV) charging/discharging, and a distribution grid. Fast-switching Gallium Nitride (GaN) high-electron-mobility transistors (HEMTs) are employed to achieve higher energy efficiency and power density. To meet the high voltage requirements on the DC grid port, a three-level active-neutral-point-clamped (ANPC) bridge based on 650V GaN HEMTs is developed. To provide galvanic isolation among different power ports, a high-frequency, multi-winding planar magnetic transformer is utilized to couple different power ports for flexible power management. The control and efficiency at four operating modes of the QAB converter are investigated for various weather conditions, and electro-thermal simulations for the QAB converter, including the planar transformer, are carried out in PLECS and Ansys software. Moreover, a 15-kW GaN HEMT based QAB DC-DC converter prototype is implemented for experimental verification.

The conventional model predictive control (MPC) applied to five-level active neutral point clamped (5L-ANPC) inverters faces a few major challenges, including a significantly heavy computational burden and an intricate tuning of the weighting factors to balance the DC-link and flying capacitor voltages. This paper presents a simplified MPC without weighting factors to leverage the desirable features of MPC within a distributed electric propulsion (DEP) system consisting of a 5L-ANPC inverter-fed axial flux permanent magnet (AFPM) motor-drive system. The proposed method compensates for the one-step delay between the commanded and applied voltage vectors in calculating the reference voltage vector. Afterwards, the optimum voltage vector is selected based on the sign of the calculated reference voltage vector using a deadbeat approach and its updated mapping position in smaller sections within the space vector of the inverter. Finally, a simplified cost function without weighting factors is presented to select the optimum switching state. The proposed method takes remarkably shorter execution time than the conventional MPC does, leading to higher sampling frequency and better steady-state performance. The performance of the proposed method is evaluated in the Acceleration and Cruise Modes of a DEP system’s flight mission profile.

Distribution transformers play a backbone role in the power grid, and it is of paramount importance to ensure high reliability of distribution transformers. Supraharmonics, an unregulated category of harmonics ranging from 2 kHz to 150 kHz, has been gaining increasing attention in recent years due to high penetration of power electronic systems in the electrical distribution network such as inverter-based resources. The presence of supraharmonics in the distribution grid poses a severe threat to the normal performance of distribution transformers, leading to higher losses and eventually higher winding temperature and reduced lifetime of the transformer. This paper focuses on the impact of supraharmonics on the reliability of distribution transformers by considering different scenarios in multi-physics modeling and simulation environment. Harmonic analyses are conducted, followed by thermal modeling, to highlight the overlooked impact of supraharmonics in diminishing the reliability of distribution transformers in the power grid.

In wind-turbine power generation systems, generators are typically located in the nacelles, and medium-voltage power converters are mostly placed at the bottom of the tower for maintenance convenience, resulting in long cables (e.g., 50–150 meters) interconnected between generators and power converters. Consequently, the high dv/dt caused by fast-switching high-voltage semiconductor devices such as silicon carbide (SiC) MOSFETs coupled with the long cables induces high-frequency reflected overvoltage across the generator stator windings. Due to uneven voltage distributions across various coils in each phase, significantly higher voltage spikes will be induced in the first few coils close to the converter side, leading to insulation degradation and winding short-circuit failures. To mitigate such reflected overvoltage across the generator windings and improve the wind-turbine system reliability, a high-efficiency, ultra-compact and low-cost mitigation solution targeting the first few coils will be developed and presented in this paper.

Robots have been increasingly applied for harsh operating environments, such as disaster rescue, space exploration, and nuclear waste remediation. Robotic arms in such environments with extremely high/low temperatures and air pressure are prone to hardware failures, especially for joint motors and power electronic drives. Brushless DC (BLDC) motors are extensively used in robotic applications because they exhibit high reliability and efficiency. Thus, this paper presents a design optimization approach for high-torque BLDC motors for robotic applications to enhance the reliability and fault-tolerance capability based on a multi-objective genetic algorithm (MOGA). Owing to the inherent advantages of fractional-slot concentrated windings (FSCW) over distributed windings, this paper adopts BLDC motors with various slot/pole combinations. On the contrary, distorted flux distribution is one main drawback of FSCW, which may yield radial forces on the rotor. Moreover, the thermal behavior of the proposed slot/pole combinations is investigated, showing the resulting thermal stress. Finally, a broad comparison of the employed winding layouts is introduced to highlight the effect of the radial forces on the rotor deformation using finite element analysis (FEA). The higher the slot/pole combination, the higher the radial forces and rotor deformation.

The air-gap airflow will affect the performance of the high-speed slotless permanent magnet synchronous motor (HSSPMSM). However, the influence of airflow is often neglected in motor design, leading to discrepancies between the designed and actual performance. This paper conducts the design and analysis of the HSSPMSM considering the influence of air-gap airflow. The coupling relationships among airflow, electromagnetic, thermal, and mechanical are established. The dimensions design and performance analysis of the HSSPMSM are performed. Based on the designed dimensions, a lOkW/40krpm HSSPMSM prototype is developed. The experimental results indicate that the developed HSSPMSM matches the design requirements.

Neutral point clamped (NPC) multilevel converters have been intensively utilized in many industry sectors, such as transportation electrifications, data centers, renewable energy generation, industry automation, and others. However, one major drawback with NPC converters is the unbalanced loss distribution among the semiconductor switches, which limits the maximum allowable output power and output frequency of the converters. In this paper, a novel immersion cooling technology is developed for NPC converters for transportation electrification applications, particularly for electric aircraft propulsion systems. The immersion cooling technology helps to balance the semiconductor thermal distribution with homogenous cooling, in addition to providing enhanced dielectric insulation capability for power converters operating at high altitude for aviation applications. This concept and the performance advantages are verified by comparing the immersion cooling case with the conventional heatsink cooled converters.

This paper examines the non-uniform overvoltage distribution on stator windings in AC motors driven by SiC-based inverters. The first coil of the stator winding experiences particularly severe overvoltage stress. To address this challenge, the paper suggests employing a circuit with adaptive impedance across the first coil. Surge impedance mismatch between the cable and motor has been identified as a cause of voltage reflection, leading to high-magnitude and high-frequency voltage ringing at the motor terminals. These overvoltage ringings/spikes pose a risk of insulation failure in the windings. To address this issue, the proposed adaptive circuit mainly includes a capacitor and a bidirectional gallium nitride (GaN) switch across the first coil. The purpose of this circuit is to ensure uniform voltage distribution by efficiently suppressing the occurrence of overvoltage spikes. A comprehensive experimental analysis is conducted to evaluate the effectiveness of the capacitor in mitigating voltage spikes, and the results are discussed in depth. The experimental setup involves a 2 hp, 460 V motor powered by a SiC-based inverter, connected through 4/C 10 AWG 30m and 18m cables. Preliminary experiments demonstrate that inserting a small capacitor during the initial few cycles effectively reduces overvoltage stress across the first coil by approximately 47%.

There are currently two existing methods to compute the fault-tolerant workspace of a redundant robot arm for a given set of artificial joint limits. However, both of these methods are very computationally expensive. This article proposes using a mixture density network to learn the probability that a rotation angle belongs to the fault-tolerant rotation ranges. A difference filter is used to remove outlying rotation angles predicted by the network, and the remaining rotation angles are grouped together to generate the fault-tolerant workspace. Because this method is highly computationally efficient, it can be used alongside a genetic algorithm to compute the optimal artificial joint limits to maximize the area of the fault-tolerant workspace for a given robot arm. The predicted fault-tolerant workspace is compared to the actual fault-tolerant workspace, which proves the effectiveness of this algorithm. The computational speed of this proposed algorithm is roughly 390 times faster than the traditional method. Finally, a trajectory is placed within the fault-tolerant workspace predicted by the proposed method, and the experimental results show that this trajectory is tolerant to arbitrary joint failures.

Power electronics and electric motor-drive systems have been increasingly utilized in various emerging industry applications, such as electric vehicles, electric aircraft, data centers, and energy storage systems. However, conventional thermal management technologies such as heat sink and indirect liquid cooling for power electronics and motor drives face increasing challenges in further improving the systematic reliability, power density, and energy efficiency. Thus, developing advanced cooling technologies will be of paramount importance to boost the performance of power converters. In this paper, multi-physics modeling and performance characterization of a 50-kW Silicon Carbide (SiC) T-Type power converter equipped with immersion cooling is presented. First, the electrical performance of the converter is investigated, and semiconductor losses of the converter are calculated which serve as the heat sources for the subsequent thermal simulation. Afterwards, the thermal behavior of the liquid-immersed converter is simulated and compared with the conventional heat sink design considering different operating conditions. By conducting computational fluid dynamics (CFD) simulations in Ansys Fluent, the enhanced heat flow dissipation of oil immersion cooling for the T-Type power converter is demonstrated.

In this article, influence of aluminum eddy current in the PSRM stator array on the electromagnetic properties and control performance is investigated. The eddy current density distribution model is established based on Maxwell’s equations, and the inductance model is derived considering the eddy current effect. The effect of aluminum eddy current on the PSRM position control performance is qualitatively analyzed. The aluminum eddy current distribution and ohmic loss distribution characteristics with the mover at different positions are verified by finite element analysis. The validity of the developed inductance model is experimentally verified. A material replacement method is proposed to eliminate the aluminum eddy current. The experimental results show that the position control accuracy of the PSRM prototype is improved by 6.94% on average after the elimination of eddy currents, while the motor efficiency is improved by 6.51%.

High dv/dt from the emerging SiC variable-frequency drives can easily induce overvoltage across the motor stator winding terminals, especially for long-cable-connected and high-voltage motor-drive systems. Due to the fast switching speed and surge impedance mismatch between cables and motors, this overvoltage can be two times or even higher than the DC-bus voltage of the inverter, resulting in motor insulation degradation or irreversible breakdown. The most common solution to mitigate such overvoltage is to install a dv/dt or a sinewave filter at the output of the drive, which decreases the efficiency and power density of the system. Among different stator coils, the first one (close to the drive side) is the most susceptible to insulation breakdown since it experiences higher overvoltage than the others due to the nonlinear distribution of the reflected surge voltages. In this paper, an innovative high-efficiency ultracompact mitigation solution is introduced, which is a tiny auxiliary circuit embedded inside the motor stator (or at the motor terminal box), specifically across the first few coils of each phase (i.e., smart coils). The proposed smart coil circuit effectively mitigates the surge overvoltage, which can be scalable to any type of motor-drive systems, regardless of cable length and semiconductor rise time. The proposed solution can dramatically improve the reliability, efficiency, and power density of motor-drive systems.

Aircraft electrification is an enabling technology to achieve zero emissions within the aviation industry. Designing power conversion systems for aircraft applications requires the concurrent consideration of power density, efficiency, and reliability. Since these objectives cannot be optimized simultaneously, a Pareto front of designs which show adequate trade-offs between multiple objectives is desired. This work proposes a multi-objective design optimization method using a genetic algorithm to quickly and accurately produce candidate designs of an electric aircraft propulsion converter. A topology comparison between multiple voltage source converters is conducted to determine each converter’s suitability to aircraft propulsion applications.

The transition to electric aircraft has gained worldwide attention as initiatives and legislations are presented in support of zero-emission aviation industry. Due to the high-power and high reliability requirements for electric aircraft propulsion, multiphase electric machines become attractive in such applications, which enables the possibility of having integrated on-board battery charger (IOBC). IOBCs fully leverage the existing powertrain propulsion elements, i.e., the multiphase machine and power inverter, into the charging process, requiring no additional hardware for fast charging. Moreover, zero average torque production and unity power factor operation at the grid side can be simultaneously achieved. Thus, this paper proposes an IOBC concept for electric aircraft, utilizing a multiphase surface-mounted permanent magnet (SPM) synchronous machine. First, an asymmetrical six-phase 36-slot/34-pole SPM machine design is presented based on the magnetic equivalent circuit (MEC) model. Thereafter, the machine is optimized using a multi-objective genetic algorithm (MOGA) optimization approach. Finally, finite element (FE) simulations have been carried out to verify the theoretical findings.

Semiconductor junction temperature is a key factor determining reliability and energy efficiency of power electronic converters. It also contributes directly to thermal management requirements, which impacts both volumetric and gravimetric power densities of power converters. The thermal coupling displayed by multiple semiconductor devices placed on the same heat sink can cause difficulty in the calculation of the steady-state junction temperature of each component. This paper describes a novel method by which the average losses of each individual semiconductor are used to quickly solve for all devices’ steady-state junction temperatures. The technique employs an iterative approach which then in turn only necessitates a single, brief, time-based thermal simulation, thus bolstering execution speed. When compared to the results from PLECS simulation software, the proposed method can accurately determine the steady-state junction temperatures in only 15-20% of the time, and after including the single, short simulation, there is a 30% speed improvement at low switching frequencies.

The advent of electrified aviation has ushered in a greater need for energy efficient, power dense, reliability-oriented design of power conversion systems. Conventionally, the entire design process consumes large quantities of time, effort, and engineering resources. To address this problem, this paper proposes a genetic algorithm enabled multi-objective design optimization framework by which one can quickly generate many iterations of a back-to-back current source converter for turboelectric aircraft propulsion systems. The automated design methodology can locate optimal trade-offs between design objectives (i.e., reliability, power density, energy efficiency, cost, etc.) and generate the Pareto front for a user-specified optimization problem.

In this paper, a novel digital twin approach is introduced for the health monitoring of five-level active neutral point clamped (5L-ANPC) power converters, which have been applied in many safety-critical high-power applications. By establishing a real-time interactive digital replica (i.e., digital twin), various parameters are measured to monitor the inverter's health condition, enabling improved reliability and lower downtime cost. To address challenges posed by multiple series-connected semiconductor switches in the 5L-ANPC converter where different switches have different junction temperatures, the on-state resistance of multiple switching devices is estimated. This estimation is achieved by using particle swarm optimization (PSO) and sensed signals. The sampled data and the PSO cost function are modified to minimize estimation errors, improving the precision of health monitoring. The robustness and effectiveness of the proposed method are demonstrated by considering various switching devices. As the first-ever digital twin approach developed for the health monitoring of multilevel power converters, the proposed technique significantly enhances the reliability of multilevel converters for high-power safety-critical applications.

High-frequency electromagnetic transformer (HFET) is one of the critical components in a solid-state transformer (SST) system, as it can provide galvanic isolation and voltage conversion between primary and secondary sides. Although SSTs are well-known for multiple beneficial features, there are reliability concerns with the HFET, especially for medium-voltage or high-voltage systems configured with fast-switching wideband gap power converters. In this paper, comprehensive multi-physics reliability modeling is presented to fully investigate the different physics of the SST systems. To this end, electromagnetic analysis by finite element method is first carried out to acquire the performance characteristics of the HFET. Afterwards, temperature distribution of the HFET is obtained based on electromagnetic results such as winding and core losses. Finally, electrostatic simulation is conducted to examine the effects of voids, which contributes to partial discharging on the dielectric strength of the insulation system. Since the three disciplines are closely related to each other, an innovative lifetime estimation model is proposed to incorporate the effect of insulation degradation due to partial discharging on the aging acceleration of the transformer in order to improve the accuracy of the lifetime estimation.

The growing focus on aircraft electrification has led to a great emphasis on distributed electric propulsion (DEP). This paper proposes a simplified fixed switching frequency model predictive control (SFSF-MPC) for an axial flux permanent magnet (AFPM) motor drive fed by a three-level T-type inverter in a DEP system. This inverter has multiple performance benefits for DEP applications due to providing more voltage vectors; however, its use in the conventional finite control set MPC (FCS-MPC) leads to an increased computational burden and hinders using higher sampling frequencies. The proposed SFSF-MPC aims to reduce the computational burden in the conventional two-step FCS-MPC by offering a set of candidate voltage vectors, which are determined based on the spatial position and magnitude of the reference voltage vector. Only the voltage vectors close to the reference voltage vector participate in optimizing the cost function. Meantime, a switching frequency regulation strategy is applied based on the gate signal edge detection to maintain a fixed switching frequency. Counting the gate signal edges can predict the switching frequency and optimize it within the cost function. Moreover, the neutral point potential is balanced by equalizing the voltages of the DC-link capacitors based on the compensated stator currents. The performance of the proposed SFSF-MPC is evaluated in the cruise mode of an electric aircraft mission profile.

Robots have shown promising prospects in numerous applications, such as space exploration, disaster rescue, and nuclear waste remediation. Due to harsh environmental conditions, robotic arms are vulnerable to joint failures, especially the faults with joint motors and power electronic drives. Thus, optimal design of the employed motors is paramount to achieve a reliable and fault-tolerant robotic arm. The employment of brushless DC (BLDC) motors in robotic applications is of particular interest, not only for high reliability but also for high efficiency and high torque-producing capability. BLDC motors can be equipped with distributed and fractional-slot windings; however, fractional-slot concentrated winding (FSCW) outperforms distributed winding owing to their notable advantages, e.g., high slot fill factor, short-end turns, and low cogging torque. On the other hand, the resultant flux distribution is highly distorted. Therefore, this research presents the design optimization of BLDC motors with two fractional-slot windings, namely, non-overlapped 18-slot/16-pole and overlapped 18-slot/10-pole, based on the finite element methodology (FEM). Selected motors are first designed based on the sizing equations and further optimized using a multi-objective genetic algorithm (MOGA). Finally, a thorough performance comparison of the proposed winding configurations is conducted to highlight the optimal slot/pole combination for robotic applications.

The optimal scheduling for dispatchable utility-scale solar PV power with a hybrid energy storage system consisting of a battery and a supercapacitor (SC) is investigated in this paper. The optimal capacity of the energy storage system (ESS) is assessed based on its usage of depth of discharge, which is critical for minimizing the cost of a dispatchable PV power scheme. The hybrid system can successfully dispatch the scheduled power at any dispatching horizon by leveraging the optimal ESS capacity. Both cycling and calendar expenses are taken into account during the cost optimization of the ESS to make it more practical. Furthermore, a state of charge (SOC) control technique based on a fuzzy inference system that takes into account both battery and SC SOC is used to accurately estimate the grid reference power for each dispatching horizon considered in this study.

The objective of this study is to investigate the expenditure of different kinds of energy storage systems (ESSs) for the economical dispatching of solar power at one-hour increments for an entire day for megawatt-scale grid-connected photovoltaic (PV) arrays. Accurate forecasting of PV power is vital for generation scheduling and cost-effective operation. A multilayer perceptron Artificial Neural Network (ANN) is utilized to predict PV irradiance one hour ahead of time, which performs well with good convergence mapping between input and target output data. Moreover, this research proposes a state of charge (SOC) control algorithm based on an adaptive neuro-fuzzy inference system (ANFIS) that can accurately estimate the grid reference power for each one-hour dispatching period, which is necessary for ensuring the ESS completes each dispatching period with its starting SOC and has sufficient capacity for next-day operation. Finally, an economic comparison is presented utilizing the Hybrid Optimization of Multiple Energy Resources (HOMER Pro) software to develop a cost-effective ESS for an hourly PV power dispatching scenario.

When considering the mission profile of an electric aircraft power inverter, two main operating modes are of more interest. When the aircraft is climbing, 100% power output is typically demanded for a short time duration. The second operating mode of interest is cruise mode where much lower output power (e.g., 30% of rated power) is generally demanded for most of the flight time. High efficiency during the cruise mode is preferred to achieve longer flight range, while high reliability is also critical for such applications. In this paper, an advanced 3-phase 4-leg T-type inverter topology is developed, which provides the peak power during the climbing mode and high efficiency at the cruising mode, in addition to fault-tolerant capability to semiconductor switching faults. Specifically, this paper focuses on current-sharing operation during the climbing mode to provide the peak power and soft-switching at the cruising mode to achieve high efficiency, in which the redundant leg is leveraged when there are no switching faults. Simulation results are presented to confirm the inverter performance for electric aircraft application considering its specific mission profile. Current-sharing is applied during climbing conditions to reduce thermal stress on the outer IGBTs of the main phase legs by 5% of the junction temperature. Soft-switching is enabled in cruise mode to reduce switching losses of the inverter by 41.1% compared to that in a conventional T-type inverter.

The recently emerging field of electrified aviation requires design automation which is able to quickly and accurately create light-weight, efficient, and reliable electric propulsion drives for potential mass production. This paper proposes a systematic multi-objective design methodology intended for aviation applications, specifically focusing on power electronic drives. Due to the high priority of reliability in such safety-critical applications, the lifetime estimations due to three major contributing factors are considered during the design optimization, namely, semiconductor power cycling lifetime, semiconductor cosmic radiation susceptibility, and DC-link capacitor power cycling lifetime. When used to design a back-to-back voltage source converter, the design optimization algorithm produced 114,817,329 solutions within approximately 2 hours. The resulting optimized performance with respect to power density, efficiency, and reliability was 11.66 kW/kg, 98.81%, and 223.48 Failures-in-Time (FIT), respectively.

An improvement of the conventional solid state dc breaker (SSDCB) is developed for shipboard medium-voltage dc (MVDC) system protection. By combining a high temperature superconducting fault current limiter (HTS-FCL) with a SSDCB based on Slicon Carbide (SiC) MOSFETs, the efficiency of the SSDCB portion is improved while the number of switching devices necessary is significantly reduced with the assistance of the HTS-FCL. The natural current limiting properties of HTS cables are leveraged such that the HTS-FCL has negligible insertion losses and passive fault limitation. In normal operation, the nominal load current flows through the superconductive HTS-FCL and SiC MOSFETs with low conduction losses. During a fault, the HTS-FCL becomes a significant resistance which limits the peak magnitude of fault current. This reduces the number of SiC devices in the SSDCB which then interrupts the fault. After interruption, a metal-oxide varistor device clamps the transient overvoltage which limits voltage stress and excessive switching losses. Simulation results are provided to verify the main functionality of the breaker in a 20 kV shipboard MVDC power system.

Power transformers are the essential components in almost every electric power network. Uninterrupted operation of power transformers plays a critical role in guaranteeing the reliability and safety of the power grid. In this paper, aiming at predicting the reliability of large power transformers, multi-physics modeling and simulations are carried out based on three-dimensional (3D) finite element analysis (FEA) and finite volume method (FVM). Specifically, FEA electromagnetic modeling and simulation is performed in Ansys Maxwell to extract the transformer winding losses. Afterwards, thermal model is established in Ansys Fluent to obtain the temperature distribution, and more importantly to identify the transformer winding hot-spot temperature (HST). Accordingly, aging acceleration factor is determined by the winding HST. A sensitivity analysis is also conducted to determine the effects of oil properties on the temperature distribution and HST.

Aircraft electrification is an emerging technology to enable net-zero emissions for global aviation. When designing an electric aircraft propulsion system, multiple objectives are desirable for the power electronic converters such as concurrently high efficiency and high power density. This requires computationally efficient design optimization. The approach proposed in this work aims to optimize an electric aircraft propulsion converter on the basis of high power density, high efficiency, high reliability, and low cost. This design methodology has been examined and a candidate solution set has been generated for a back-to-back voltage source converter rated at 1 MW with a DC-link voltage of 2.4 kV. Using a selection of commercially available power components, accurate calculations, including cost, have been conducted for the 17,107,272 solutions in just 20 minutes approximately. Of the 7,930 designs in the Pareto front when using the objectives of power density, cost, efficiency, and reliability, the optimal performance on each goal for the propulsion power converter system is 11.151 kW/kg, $22.03/kW, 98.302%, and 1,642 FIT, respectively.

Medium voltage DC (MVDC) is an emerging technology to enable the transmission and distribution systems of electric aircraft to be more lightweight and efficient. In this paper, a performance comparison is presented between three options of megawatt-scale medium-voltage (MV) power inverters based on Silicon Carbide (SiC) power modules. These three options include: two-level MV inverter based on 3. 3kV high-voltage SiC modules, two-level MV inverter based on series connections of 1. 7kVSiC modules, and three-level active neutral point clamped (ANPC) MV inverter based on 1. 7kVSiC modules. Specifically, the efficiency and reliability have been compared and discussed, which will provide a reference for engineers and researchers to develop electric aircraft propulsion drives in the future.

This paper demonstrates a dispatching scheme of slider-crank wave energy converter (WEC) power generation using two different kinds of energy storage components, namely, Lithium-ion (Li-ion) battery and Supercapacitors (SC). The performance of the two energy storage components has been compared in order to develop the most economical energy storage system for WEC hourly dispatching scheme. The cost optimization of the energy storage system considering both cycling and calendar aging expenses is made based on its usage of depth of discharge. In this study, extensive simulation is conducted in MATLAB/Simulink platform, and it is found that SC is a better solution than Li-ion battery in terms of economic assessment for hourly dispatching WEC power.

This study demonstrates a dispatching scheme of solar PV power utilizing two different types of energy storage components, namely, lithium-ion (Li-ion) battery and supercapacitors (SC). The cost optimization of the energy storage system, considering both cycling and calendar aging expenses, is assessed based on its usage of depth of discharge. It is found that the Li-ion battery is a better solution than the SC in terms of economic assessment for hourly dispatching PV power. Also, multilevel inverters, T-type and I-type neutral point clamped (NPC) inverters, are investigated due to their superior attributes: high efficiency, low total harmonic distortion, and reduced common-mode voltage. The power losses between the three-level T-type and I-type NPC inverters are compared, to identify the superior grid inverter topology for this application. The inverter loss analysis is conducted using the parameter values of the switching devices in the MATLAB/SIMULINK environment, and the T-type NPC inverter was found to exhibit better performance than the I-type NPC inverter for megawatt-scale grid connected PV arrays. Furthermore, an LCL filter has been designed for higher efficiency and better harmonic attenuation to interface the inverter with the utility grid.

Constrained by the low energy density of Lithium-ion batteries with all-electric aircraft propulsion, the hybrid-electric aircraft propulsion drive becomes one of the most promising technologies in aviation electrification, especially for wide-body airplanes. In this paper, a three-port triple active bridge (TAB) DC-DC converter is developed to manage the power flow between the turbo generator, battery, and the propulsion motor. The TAB converter is configured based on Silicon Carbide (SiC) MOSFET modules operating at high switching frequency, so the size of the phase shifting magnetic transformer can be significantly reduced. Different operation modes of this hybrid-electric propulsion drive based on the SiC TAB converter are modeled and simulated to replicate the takeoff mode, cruising mode, and descendent mode of a typical flight profile. The results show the TAB reaches a peak efficiency of 99.74% at 60% of full load during takeoff and achieves soft-switching operation at full load across operating modes.

This study investigates a dispatching scheme of megawatt-scale solar PV power for a one-hour dispatching period for an entire day utilizing an isolated multiport converter configuration and battery energy storage system. A multilevel triple active bridge (TAB) dc-dc converter has been proposed where a neutral-point-clamped (NPC) H-bridge is employed in the high-voltage side, and the conventional two-level full-bridge is configured in the low-voltage side across the high-frequency transformer. The power losses between the proposed TAB-NPC converter and conventional TAB converter are compared to identify the superior multiport converter topology for this application. The converter loss analysis is conducted using the parameter values of the switching devices in the MATLAB/SIMULINK environment, and the proposed TAB-NPC converter is found to exhibit better performance than the conventional TAB for megawatt-scale grid-connected PV arrays. Furthermore, the curve fitting and Particle Swarm Optimization techniques are implemented to seek the optimum value of depth of discharge for the battery energy storage system taking into account both the cycling and calendar expenses. A fuzzy inference system as a function of the battery state of charge is also developed to accurately estimate the grid reference power for each one-hour dispatching period, which helps to develop a cost-effective energy storage system for hourly dispatching PV power scheme.

This paper aims to optimize the expenditure of a hybrid energy storage system that includes a battery and supercapacitor (SC) for economical dispatching wind power at one-hour increments for an entire day for a megawatt-scale grid-connected wind turbine system. The frequency management technique is employed to exploit the technical merits of the two-energy storage apparatus and to optimally allocate the power flow between two storages to dispatch a committed pre-determined constant power into the grid. The cost optimization of the HESS is computed based on the time constant of the low pass filter (LPF) through extensive simulations in a MATLAB/SIMULINK environment, and a Contemporary Particle Swarm Optimization (CPSO) approach is implemented to seek the optimum value of the LPF time constant. Moreover, a state of charge (SOC) control algorithm based on a fuzzy inference system considering both battery and SC SOC is proposed in this study to accurately estimate the grid reference power for each one-hour dispatching period. This research also demonstrates an economic comparison to investigate the impact of utilizing different kinds of energy storage for hourly dispatching wind power. The simulation results exhibit that the presented HESS is superior to a battery or SC-only operation.

Moving toward electric propulsion drives in aircraft applications is a significant step forward to enhance the efficiency of aviation systems. Taking advantage of medium voltage DC (MVDC) as a leading edge technology can further increase the efficiency and power density. To this end, emerging wide-bandgap devices with lower switching losses can be incorporated into multilevel inverter topologies. However, existing Silicon Carbide (SiC) switches have weak short-circuit capability. This is the main downside of all-SiC inverter topologies which restrains their application in safety-critical applications. On the other hand, Silicon (Si) IGBTs have better short-circuit performance, although rendering higher switching losses. To overcome this challenge, a hybrid "Si+SiC" five-level active neutral point clamped (ANPC) inverter is proposed in this paper to improve the short-circuit capability of the aircraft propulsion drive systems. Simulation results comparing the efficiency and short-circuit capability of all-SiC, all-IGBT, and hybrid "Si+SiC" topologies are presented to demonstrate the effectiveness of the proposed topology.

Increasing penetration of the Photovoltaic (PV) systems in electric power generation sector entails high-reliability grid-connected PV inverters. In fact, inverter faults are one of the most common root causes for PV system failures that significantly increase the levelized cost of energy (LCOE). Meanwhile, higher voltage levels are favorable for utility-scale PV applications due to higher energy efficiency. Hence, a novel fault-tolerant four-leg five-level active neutral point clamped (5L-ANPC) inverter is proposed in this paper. In a fault scenario, the fourth leg can replace any of the faulty phases of the inverter to provide the fault-tolerant capability for post-fault operation. In normal healthy condition, the fourth-leg can be used for heavy-load current sharing to mitigate the thermal stress on the semiconductor devices of the main phase legs, which further enhances the PV system reliability. Simulation results are demonstrated to verify the effectiveness of the proposed PV inverter.

Medium-voltage electric propulsion is a promising technology to enable the electrification of aircraft, especially for twin-aisle aircraft. The performance of the medium-voltage power converter plays a critical role in the overall electric propulsion performance. To pursue higher efficiency, reliability, and power density, this paper investigates the comparison of the current source converter, direct and indirect matrix converters, with respect to a multilevel voltage source converter. The emerging Silicon Carbide (SiC) MOSFET modules are used to configure the power converters to achieve higher efficiency and power density. All these converters are modeled and simulated for a megawatt-scale propulsion drive system rated at medium voltage. Simulation results are presented and analyzed to provide a reference for the future aircraft propulsion designs.

PV generation is a key contributor to a carbon-neutral power system. With proper planning and operation, it has significant potential to improve system reliability as well. Nevertheless, solar availability is volatile which poses a challenge to ensure an uninterrupted grid-supporting performance. One critical factor leading to the loss of PV generation is PV inverter malfunctioning as it is the most frequent fault scenario in PV systems. Despite this, there is still inadequate study into PV inverter reliability, especially for online non-intrusive health monitoring methods. In addition, effective PV planning calls for quantitative study into PV impact on grid reliability. This paper is one of the first efforts to bridge this gap. We first reveal the significance of PV generation to grid reliability by studying its impact on grid transient performance in both DC and AC networks. It can work as an input to PV planning problems, for example, to determine the optimal siting and operation strategies. Then, we develop an online monitoring algorithm to provide situational awareness information into PV inverter health. At last, we develop fault-tolerant control strategies for PV inverters to enhance PV availability. A case study verifies the proposed work.

This paper presents the fault-tolerant current source inverter based motor-drive system, which can diagnose the open-circuit failure of the switches and restructure the topology of the inverter to keep the inverter operating in the post-fault condition. The proposed diagnostic method is able to detect the open-circuit fault both in the main switches and those of the redundant switches. During fault-tolerant operation, the identified faulty switch is fully replaced by one of the switches from the fourth leg to ensure full rating operation of the inverter without any extra overrating requirements for switches. In addition, wide bandgap (WBG) devices are employed to conFigure the redundant fourth leg. During normal operation, soft switching is enabled across all the silicon IGBTs, while just WBG devices in the fourth leg undertake hard switching. Thus, the inverter efficiency is improved and the thermal stress in the IGBTs is relieved.

Medium voltage dc system is a promising technology to significantly improve the efficiency and power density of electric aircraft propulsion drives. In this paper, a five-level active neutral point clamped (5L-ANPC) topology is selected as the inverter for the propulsion drives, due to its higher voltage capability and lower output harmonics as well as reduced common-mode voltage. To meet the high-speed requirement of the aircraft propulsion drives and to boost the efficiency and power density of the inverter, Silicon Carbide (SiC) semiconduc-tor devices are considered for the 5L-ANPC inverter. However, the large commutation loop associated with some of the switching states of the inverter prevent configuring all the switches as SiC devices. As a result, a hybrid "Si+SiC" five-level ANPC inverter and a synchronous optimal pulse width modulation strategy are developed, in which the SiC devices are only used for the switches at the ac output side and the rest of the switches are configured with Si IGBTs. This hybrid ANPC inverter concurrently achieves high efficiency and low implementation cost, at high-speed operation mode. Thermal modeling and simulation results are presented to verify the performance of the proposed hybrid inverter.

A new member of Modified CUK Converter family with a two-switched inductor module (MCCSI): Modified CUK Converter with XYL configuration (MCCSI-XYL), Modified CUK Converter with LYZ configuration (MCCSI-LYZ) and Modified CUK Converter with XLZ configuration (MCCSI-XLZ) is introduced in this paper. The highlighting points of the proposed converters are (i) single switch topologies, (ii) continuous input current, (iii) high voltage gain, and (iv) inverted output. The voltage gain analysis of three configurations is carried out in detail. Additionally, the comparison of the three converters is made w.r.t. the component count and voltage gain. The MatLab simulation results meet the mathematical analysis and validate the functionality and feasibility of the presented three converters.

The national electric power grid is being transformed into a smart grid through deploying a huge number of distributed sensors across the network, a two-way communication system, intelligent control and optimization algorithms, and advanced hardware components. An increasing volume of data are collected by the sensing system, and transfer of these data to a central location for centralized processing poses burden to the communication system and the central computing system. Edge computing, a distributed computing paradigm, processes data and makes proper decisions locally, stores data locally and provides selected, processed data to a higher level, and thus may significantly relieve communication burden and reduce response time of certain control applications. This paper explores possible applications of edge computing to enhance distributed optimization and control of smart grid, including power system asset management, distributed charging scheme and microgrid protection.

This paper aims to optimize the cost of a battery and supercapacitor hybrid energy storage system (HESS) for dispatching solar power at one-hour increments for an entire day for megawatt-scale grid-connected photovoltaic (PV) arrays. A low-pass filter (LPF) is utilized to allocate the power between a battery and a supercapacitor (SC). The cost optimization of the HESS is calculated based on the time constant of the LPF through extensive simulations in a MATLAB/SIMULINK environment. Curve fitting and Particle Swarm Optimization (PSO) techniques are implemented to seek the optimum value of the LPF time constant. A fuzzy logic controller as a function of battery state of charge is developed to estimate the grid reference power for each one-hour dispatching period. Since the ambient temperature and PV cell temperature are different, this study also considers the relationship between them and presents their effects on energy storage cost calculations.

In this paper, a novel zero-voltage-switching (ZVS) current-source rectifier (CSR) based bidirectional on-board charger (OBC) system is proposed for electric vehicles with silicon carbide (SiC) devices. Compared with the traditional voltage-source converter based counterparts, the proposed method offers the advantages including higher-quality output voltage waveforms, enhanced short-circuit-current tolerant capability and longer operation lifetime. Furthermore, ZVS can be achieved for main power switches in CSR with the additional auxiliary power branch. Thus, the switching losses can be further decreased. Besides, the high dv/dt caused by high speed switching SiC devices can be reduced with the capacitor in the auxiliary circuit. Hence, the EMI of high-frequency switching of SiC devices can be mitigated effectively. Both simulations and experimental results are presented to verify the performance of the proposed method.

High efficiency, high power density, and high reliability are three essential criteria for evaluating aircraft propulsion drives. In this paper, a current source inverter (CSI) based on Silicon Carbide (SiC) normally-on MOSFETs is proposed for electric aircraft propulsion drives. The high-frequency operation of the SiC CSI enables lower value of dc-link inductance. Additionally, unlike the conventional voltage source inverters (VSI), the inherently sinusoidal line-to-line voltages waveforms output from the CSI waives the necessity of having a bulky sinewave filter or dv/dt filter, even for long-cable-fed motor drive applications. Therefore, high efficiency and high power density can be concurrently achieved for the proposed propulsion drive. Moreover, differing from the VSI, CSI with normally-on semiconductor switches can tolerate uncontrolled generator fault in which the microcontroller is tripped by electromagnetic inter-ference or other causes when the permanent magnet synchronous machine is operating at high speed with large induced back electromotive force. Simulation results are presented to confirm the high performance of such a SiC CSI based aircraft propulsion drive.

The hybrid utilization of photovoltaic and wind turbine, known as the wind-solar hybrid power system (WSHPS), is one of the most promising renewable energy technologies for satisfying the power load demand, since they have complementary energy generation profiles and reduced capacity for energy storage. This paper demonstrates a successful dispatching scheme of the WSHPS for a one-hour dispatching period for an entire day using battery and supercapacitor hybrid energy storage system (HESS). Frequency management technique is utilized to increase the longevity of the batteries through comprehensively utilizing the high power density property of supercapacitors and the high energy density property of batteries in the HESS scheme. Several control algorithms based on the battery state of charge are developed to achieve accurate estimation of the grid reference power for each one-hour dispatching period that helps to minimize the energy storage cost, in addition to ensuring the energy storage system with sufficient capacity to be available for next-day operation. This study also presents an economic comparison to investigate the impact of using different kinds of energy storage systems for hourly dispatching the power of the WSHPS. The simulation results show that HESS outperforms battery-only or supercapacitor-only operation.

A novel hybrid circuit breaker for medium voltage dc (MVDC) electric shipboard power systems is proposed. The breaker combines the benefits of the efficiency of a mechanical breaker and the interruption speed of a solid-state breaker. The proposed breaker utilizes a fast-ramping current source with a fast-actuating vacuum interrupter (VI) to provided ultra-fast response time and high on-state efficiency. During normal operation, nominal load current flows through the vacuum interrupter in the main conduction branch, providing a low-resistance path with negligible losses. During a fault, a current zero crossing is achieved by the use of a controllable resonant current source (RCS). By leveraging the high switching frequency capabilities of Silicon Carbide (SiC) devices, the current source achieves higher frequency of resonance than previously possible with the silicon counterparts. After interruption, the surge arrester in the energy absorption branch clamps overvoltages and dissipates all residual system energy. Simulation results from the PLECS software environment are presented to verify the functionality of this proposed breaker in a 20 kV MVDC system for electric shipboard applications.

A novel hybrid circuit breaker is proposed that utilizes a fast-ramping resonant current source and an ultra-fast vacuum interrupter (VI) for medium voltage dc (MVDC) applications. The design offers a compromise between mechanical and purely solid-state dc circuit breakers with high efficiency and fast fault interruption speed. The breaker consists of 3 parallel branches: the resonant current source (RCS) module, vacuum interrupter, and energy absorption branch. In normal operation, the vacuum interrupter is closed and conducts load current, resulting in high efficiency. During fault operation, the resonant current source ramps up to oppose the fault current in the vacuum interrupter to force a zero current crossing. In post-fault operation, the metal oxide varistor in the energy absorption branch clamps overvoltages and dissipates residual line current and energy. Gallium Nitride switching devices are used to configure the RCS modules to achieve higher frequencies and lower switching losses than the conventional silicon counterparts. Modeling and simulation results from PLECS software are presented to prove the functionality of this design in a 2.4 kV MVDC propulsion system for electric aircraft.

As an environmental friendly vehicle, the increasing number of electrical vehicles (EVs) leads to a pressing need of widely distributed charging stations, especially due to the limited on-board battery capacity. However, fast charging stations, especially super-fast charging stations may stress power grid with potential overload at peaking time, sudden power gap and voltage sag. This paper discusses the detailed modeling of a multiport converter based EV charging station integrated with PV power generation, and battery energy storage system, by using ANSYS TwinBuilder. In this paper, the control scheme and combination of PV power generation, EV charging station, and battery energy storage (BES) provides improved stabilization including power gap balancing, peak shaving and valley filling, and voltage sag compensation. As a result, the influence on power grid is reduced due to the matching between daily charging demand and adequate daytime PV generation. Simulation results are presented to confirm the benefits at different modes of this proposed multiport EV charging circuits with the PV-BES configuration. Furthermore, SiC devices are employed to the EV charging station to further improve the efficiency. For different modes and functions, power losses and efficiency are investigated and compared in simulation with conventional Si devices based charging circuits.

High-speed permanent magnet synchronous machine (HSPMSM) has been widely used in high speed direct-drive applications due to its high power density and high efficiency. However, the low inductance of the HSPMSM under the condition of low carrier ratio of the motor-drive system, especially in medium and high power systems, results in high current harmonics. This paper proposes a hybrid pulse width modulation (PWM) strategy in full speed range of HSPMSM system based on a hybrid utilization of the space vector PWM (SVPWM) method and the selective harmonic elimination PWM (SHEPWM) method, in addition to having a RLC harmonic filter. The operating principle of the SHEPWM is analyzed firstly, and the structure and working principle of the system are expounded. Then, a comparison between the SHEPWM and SVPWM is carried out considering the current harmonics. Furthermore, the SHEPWM and the RLC filter are combined to achieve a better overall performance. Finally, the dynamic switching technology under different PWM methods is investigated to achieve smooth transition, and the proposed control strategy in this paper is verified by simulation results.

This paper presents a finite control set model predictive control (FCS-MPC) method to reduce the power module loss while meeting the converter performance requirements. Many modulation-level and system-level loss reduction strategies are proposed by either changing the switching frequency or adjusting the reactive power. However, increased control loops and complicated modulation schemes restrict the system performance and implementation. With the features of model predictive control, FCS-MPC has the capability to achieve several control targets by simultaneously optimizing multiple objective functions. In the proposed FCS-MPC, a secondary objective function is defined to reduce the power loss of semiconductor devices and relieve the thermal stress for power modules. This control mechanism provides the system with not only the straightforward effectiveness, but also maintaining the converter performance requirements. The proposed FCS-MPC is validated in the simulations and experiments. A 2.5-kW PWM rectifier prototype is developed to demonstrate the proposed control method.

Power electronic converters are key components in hybrid-electric propulsion aircraft systems. Light weight and high efficiency converters are essential to achieve the goal of reduced fuel burn and emissions. For larger commercial aircraft, it is beneficial to increase the distribution voltage level from conventional 270Vdc to medium voltage for lower system losses and cable weight. A high-power density megawatt-scale medium-voltage power converter based on hybrid 3-level active-neutral-point-clamped (3L-ANPC) converter is developed to meet these requirements. This paper presents the hardware design and experimental test results of the converter.

Fault tolerance plays a critical role for power electronic systems in safety-critical applications such as the distributed generation of renewable energy. Particularly, multi-level power converters have been intensively utilized in medium-voltage or high-voltage distributed generations, the circuit topologies of which contain many more switching devices, leading to increased device failure probability. However, one main drawback with the majority of the existing fault-tolerant power converter topologies is the degraded efficiency due to the addition of the redundant phase leg or power semiconductor modules. A new 3-phase 4-leg fault-tolerant active neutral point clamped (ANPC) converter is proposed to tolerate switching faults under faulty condition, which also provides high efficiency under normal healthy condition by leveraging the redundant leg for current sharing with other main phase legs. In this paper, the efficiency of this fault-tolerant ANPC inverter will be investigated under the proposed switching schemes with the current sharing capability. The experimental results verify that this new 3-phase 4-leg fault-tolerant ANPC converter achieves higher efficiency under the current sharing switching scheme than that without current sharing, under normal/healthy operating condition.

In this article, the conventional landsman DC-DC converter is modified to achieve the high inverting voltage conversion ratio for renewable energy applications. A new Switched Reactive Circuitry (SRC) made of one inductor, one capacitor, and two diodes are incorporated to lift the voltage conversion ratio. The characteristics waveform and operation of the proposed converter is discussed in detail. The proposed converter finds the major role in renewable energy integrated application where the high voltage demanded. The proposed landsman converter is compared with existing landsman converter and recently proposed converter in terms of voltage conversion ratio. The proposed configuration has higher voltage conversion ratio compared to conventional landsman converter. The simulation results match with theoretical analysis and validate the feasibility and functionality of the proposed converter.

The utility-scale photovoltaic (PV)-battery systems typically include multiple power converters connected to the grid via traditional line frequency transformers (LFT), which may be considered bulky, and inefficient when compared with the emerging solid state transformers (SST). This paper proposes a SST with power and voltage controls for utility-scale PV-battery systems. The PV system was modeled based on available data from a universal solar facility located in Kentucky, USA. Furthermore, this paper provides detailed controller designs for the proposed utility-scale PV-battery system based on a SST which includes: the PV-side dual-active bridge (DAB) converter tracks the maximum power point, the PV inverter for steady power transformation to the grid, battery-side DAB converter for maintaining stiff dc bus voltage, and the battery inverter for voltage support and balanceing the power mismatch between the grid demand and the PV generation. Moreover, medium frequency transformer (MFT) and Silicon Carbide (SiC) MOSFETs are utilized in the DAB converters and inverters, to improve the efficiency of the PV-battery system. The simulation results based on the data retrieved from an operational PV facility, on one hand, are presented to confirm the benefits of the proposed SiC SST based PV-battery system; on the other hand, provide an alternative analysis on power losses and efficiency for the utilityscale PV farms.

Reliability of power inverters is of paramount importance in safety-critical applications, such as electric vehicles, electric aircrafts, and the like. A failure of a semiconductor device may cause cascaded faults in the power inverters and thus the systems or even lead to catastrophic disasters. Particularly, for low-speed high-power motor-drive applications, the power cycling lifetime of semiconductor device and thus the power inverters will be subject to dramatic degradation during long time of heavy-duty operation, which in fact has received little attention over the past years. In this paper, a novel discontinuous pulse width modulation (NDPWM) strategy will be investigated to improve the power cycling lifetime of MOSFET-based power inverters for low-speed high-power motor-drive applications. Simulation and experimental results verified the efficacy of the NDPWM method, and performance comparison is conducted with the traditional SVPWM and DPWM methods.

Hybrid-electric propulsion is an enabling technology to make aircraft more fuel-efficient, quieter, and create lower carbon emissions. This paper presents a high power density medium-voltage (MV) megawatt-scale power converter based on a hybrid three-level active neutral-point-clamped (3L-ANPC) topology. To achieve high efficiency, the switching devices that operate at the carrier frequency are Silicon Carbide (SiC) Metal-Oxide Semiconductor Field-Effect Transistors (MOSFETs). Conventional Silicon (Si) Insulated-Gate Bipolar Transistors (IGBTs) switches operate at the fundamental output frequency. 2.4kV dc bus voltage was chosen to reduce system cable weight. The fundamental output frequency of the converter is 1.4kHz to drive a high speed motor The large fundamental frequency helps reduce system weight. Filters are designed to meet dv/dt limits on ac side and EMI specifications on dc side. Main hardware development and control modulation strategies are presented. Experimental results are included to verify the performance of this MW-scale power converter. The converter achieves a high efficiency of 99.1%, specific power density of higher than 18kVA/kg and high power density of 10MVA/m3.

Acoustic transmitters used in underwater communication system typically utilizes the PIEZO-Electric elements in their construction. The PIEZO-Electric sends data when it is supplied by an AC voltage in an operating period. The water depth in a location where the transmitters are operated determines the required supply voltage level of the transmitter. A high-efficiency high step-up high-power density (HHH) converter plays a critical role in supplying PIEZO-Electric transmitters in underwater applications. Moreover, the PIEZO-Electric transmitters (PZETs) must occupy a small space for underwater applications. Hence, a DC-DC HHH converter is proposed in this paper which is able to operate in zero voltage switching (ZVS) conditions; while the absence of a transformer or any coupled inductor in the topology significantly improves the power density. In this paper, when the DC-DC HHH converter increases voltage level to the desired value, a full-bridge converter provides required AC voltage to supply the PZETs. Simulation results demonstrate the effectiveness and high efficiency of the proposed converter during supplying a PZET. Also, a converter prototype is implemented to demonstrate the performance of the converter in the provision of soft switching as well as boosting.

High power density medium voltage high speed electric motors for aircraft hybrid electric propulsion applications often require high output fundamental frequency from the power inverter. Conventional Si-based medium voltage drive has a switching frequency that is not sufficient to meet the dynamic and harmonic requirements for such application. A “SiC+Si” hybrid three-level active neutral point clamped (ANPC) inverter has been developed as high-speed motor drive for hybrid electric propulsion. Single-phase and three-phase pump-back tests are performed to validate the power capability and basic control functions. The implementation and test results will be reported in this paper.

This paper proposes an improved mathematical model for a novel electromechanical actuator (EMA) based on Lagrange-Maxwell equation. This model avoids the analysis to complicated electromechanical coupling relationship of the novel EMA. It views the novel EMA as a whole and establishes its mathematical model from the viewpoint of energy. Moreover, the nonlinear factors of novel EMA can be reflected more accurately and comprehensively in this improved mathematical model. By adopting the triple closed loop control based on current chopping control (CCC), both the improved mathematical model and the conventional mathematical model are simulated. The simulation results indicate that the improved mathematical model can not only reflect the adverse effects of nonlinear factors, but also reflect the dynamic performance of novel EMA more precisely than the conventional one. In addition, the experiments are also made. The results of experiments verify the accuracy and superiority of improved mathematical model.

Fault-tolerant power converters play a critical role in the transportation electrification. However, fault-tolerant operation, high efficiency, and low cost usually result in design criteria that have conflicting constraints and goals. The majority of the fault-tolerant power converter topologies presented in the literature confirm these conflicts. In this paper, three types of fault-tolerant neutral-point clamped (NPC) converters are investigated. Various modulation strategies are explored to reduce the losses of the redundant phase leg. The simulation and experimental results show that the Switching Frequency Optimal Phase opposition Disposition modulation strategy is the most effective approach in minimizing the losses in the redundant phase leg.

In this paper, an improved pulse width modulation (PWM) strategy is introduced for three-level active neutral point clamped (ANPC) converters configured by Silicon Carbide (SiC) MOSFETs and Silicon (Si) IGBTs. Compared with the existing PWM strategies in the literature, this improved PWM strategy only interfaces with small commutation loops, therefore the turn-off voltage overshoots caused by the parasitic loop inductance are much lower. Soft switching is achieved across the IGBTs. Also, the conduction loss at zero voltage output is reduced due to the turn-on of two parallel conduction paths for zero voltage output. Furthermore, this proposed PWM strategy can protect the body diodes of the SiC MOSFETs from carrying large load current. To verify all these benefits of the improved PWM strategy, a megawatt (MW) scale three-phase three-level ANPC inverter is developed and implemented, and the experimental results are presented to verify the efficacy and merits of this improved PWM strategy.

Using wide bandgap (WBG) devices has been a promising solution to improve the efficiency of power inverters for photovoltaic (PV) applications. However, for multilevel inverters, using WBG devices to improve the inverter efficiency can increase the system cost dramatically due to the high price of WBG devices in the present market as well as the large number of power devices typically required in multilevel inverter topologies. In this paper, a five-level transistor clamped H-bridge (TCHB) inverter will be further investigated. This inverter requires much lower number of semiconductor switches and fewer isolated dc sources than the conventional cascaded H-bridge inverter. To improve the inverter efficiency, semiconductor switches operating at carrier frequency will be configured by Silicon Carbide (SiC) devices to reduce the dominant switching losses, while the switches operating at fundamental output frequency (i.e., grid frequency) will be constituted by Silicon (Si) devices. As a result, both of the peak efficiency and California Energy Commission (CEC) efficiency of the TCHB inverter are significantly improved and dramatic system cost increase is avoided. In addition, due to the faster saturation characteristic of the IGBT devices, the large short-circuit current in SiC MOSFETs is constrained under the condition of load short-circuit faults. In other words, this proposed “SiC+Si” hybrid TCHB inverter can ride through a load short-circuit fault. Simulation and experimental results are presented to confirm the benefits of this proposed hybrid TCHB inverter.

This paper introduces an on-line open-phase fault diagnostic approach for five-phase permanent-magnet synchronous machines (PMSMs) fed by closed-loop vector-controlled drives. Based on the concept of magnetic field pendulous oscillation (MFPO) phenomenon, typical operating characteristics under various faulty conditions are investigated for the PMSM drive system, including single-phase open fault, two-adjacent phase open fault, and two-nonadjacent phase open fault, respectively. Moreover, to reduce the implementation cost of the developed diagnostic method, a phase-locked loop (PLL) technique is adopted to overcome the fault masking difficulties associated with the compensation action of the closed-loop drives. In addition, original theoretical derivation of the proposed fault diagnostic technique is presented. This approach can effectively detect and identify various types of open-phase faults, as well as help localize the faulty phase.

Hybrid-electric propulsion system is an enabling technology to make the aircrafts more fuel-saving, quieter, and lower carbide emission. In this paper, a megawatt-scale power inverter based on a three-level active neutral-point-clamped (3L-ANPC) topology will be developed. To achieve high efficiency, the switching devices operating at carrier frequency in the power converter are configured by the emerging Silicon Carbide (SiC) Metal-Oxide Semiconductor Field-Effect Transistors (MOSFETs), while the conventional Silicon (Si) Insulated-Gate Bipolar Transistors (IGBTs) are selected for switches operating at the fundamental output frequency. To reduce system cable weight, the dc-bus voltage is increased to 2.4 kV. Unlike the conventional 400 Hz aircraft electric systems, the rated fundamental output frequency here is boosted to 1.4 kHz to drive the high-speed motor, which can also reduce system weight. Main hardware development and control modulation strategies are presented. Experimental results are presented to verify the performance of this MW-scale medium-voltage “SiC+Si” hybrid three-level ANPC inverter. It is shown that the 1-MW 3L-ANPC inverter can achieve a high efficiency of 99% and high power density of 12 kVA/kg.

Power inverters based on wide bandgap (WBG) switching devices are being increasingly applied in new-generation adjustable speed drives (ASDs), due to their benefits of high efficiency and high power density. However, the high change rate of the output voltage (dv/dt) generated from the fast switching operation of the WBG devices in ASDs, such as Silicon Carbide (SiC) MOSFETs, could cause significant surge voltages which will be unevenly distributed in the motor windings, especially in the first coil of the stator windings. This paper will investigate various approaches to mitigate the surge voltage stress on the stator windings of a 5-hp induction motor, which is driven by a SiC-MSOFET-based ASD prototype. Simulation and experimental results verify that the stress of surge voltage and dv/dt on the first few turns of the first coil is much higher than these on other winding turns, which can be mitigated by three effective approaches, including using multilevel inverter, dv/dt filter, and integrated motor drive techniques.

Solar race cars require compact components operating at high efficiency. This paper proposes the use of a coreless axial flux permanent magnet machine, which has the attributes of low stator mass, negligible core loss and virtually zero cogging torque, as the propulsion motor. A three-phase inverter with its dc bus fed from a three-port DC/DC converter, which accepts inputs from a solar panel and battery powers the propulsion motor. Galium nitride (GaN) devices are used in the three-port converter, allowing very high switching frequencies thereby reducing the size of the transformer which provides galvanic isolation between the two sources and output. The three-port converter ensures operation of the solar panel at its maximum power point and also allows bi-directional power flow between the propulsion motor and battery depending on operating conditions. Operation over a wide range of speeds, which is required by the solar race car application, is achieved by the new approach of current weakening. This method involves raising the dc bus voltage of the motor side inverter at speeds exceeding the rated.

Reliability of multilevel power converters has received increased attention over the past few years, due to the relatively high component failure probability caused by the large number of switching devices utilized in the converter topologies. Thus, the fault-tolerant operation of multilevel converters plays an essential role in safety-critical industrial applications. This paper introduces an improved fault-tolerant inverter topology based on the conventional three-level T-Type neutral-point-clamped (NPC) inverter. Unlike other existing three-phase four-leg fault-tolerant inverter topologies, the fault-tolerant T-Type inverter topology proposed here can significantly enhance the overall thermal overload capability of the inverter, in addition to providing desired fault-tolerant capability. The operating principle of this proposed fault-tolerant T-Type inverter is detailed in this paper, and simulation results are presented to verify the advantages of this improved inverter topology.

A novel fault-tolerant power converter topology is developed based on conventional active neutral point clamped (ANPC) converter. The effect on converter performance due to open/short circuit faults of power devices is investigated. By leveraging the redundant leg in the proposed topology, the lost voltage vectors in the space vector diagram can be restored. This new fault-tolerant topology is capable of maintaining the full output voltage and maximum modulation index during post-fault operation stage. A 25-kW converter prototype based on using 1.2kV SiC MOSFETs has been built in the laboratory, and the experimental results verified the efficacy of the proposed fault-tolerant ANPC converter.

The performance of a novel three-phase four-leg fault-tolerant T-Type inverter topology is presented in this paper, which significantly improves the inverter's fault-tolerant capability regarding device switch faults. In this new modular inverter topology, only the redundant leg is composed of Silicon Carbide (SiC) power devices and all other phase legs are constituted by Silicon (Si) devices. The addition of the redundant leg, not only provides fault-tolerant solution to switch faults that could occur in the T-Type inverter, but also can share load current with other phase legs. Moreover, quasi zero-voltage switching (ZVS) and zero-current switching (ZCS) in the Si Insulated-Gate Bipolar Transistors (IGBTs) of the main phase legs can be achieved with the assistance of SiC Metal-Oxide Semiconductor Field-Effect Transistors (MOSFETs) in the redundant leg. Simulation and experimental results are given to verify the efficacy and merits of this high-performance fault-tolerant inverter topology.

On-line condition monitoring is of paramount importance for multilevel converters used in safety-critical applications. A novel on-line diagnostic method for detecting open-circuit switch faults in neutral-point-clamped (NPC) multilevel converters is introduced in this paper. The principle of this method is based on monitoring the abnormal variation of the dc-bus neutral-point current in combination with the existing information on instantaneous switching states and phase currents. Advantages of this method include simpler implementation and faster detection speed compared to other existing diagnostic methods in the literature. In this method, only one additional current sensor is required for measuring the dc-bus neutral-point current, therefore the implementation cost is low. Simulation and experimental results based on a lab-scale 50 kVA adjustable speed drive (ASD) with a three-level NPC inverter validate the efficacy of this novel diagnostic method.

This paper investigates the modeling, simulation and implementation of sensorless maximum power point tracking (MPPT) of permanent magnet synchronous generator wind power system. A comprehensive portfolio of control schemes are discussed and verified by simulations and experiments. Particularly, a PMSG-based wind power emulation system has been developed based on two machine drive setups - one is controlled as wind energy source and operated in torque control mode while the other is controlled as a wind generator and operated in speed control mode to attain MPPT. Both simulation and experimental results demonstrate a robust sensorless MPPT operation in the customized PMSG wind power system.

Active front end (AFE) converters have been extensively used in industrial motor-drive systems due to their energy regenerative capability and low harmonic distortions. However, the Pulse Width Modulation (PWM) switching operation in AFE converters generates higher common-mode voltage than their non-regenerative diode front-end (DFE) counterparts. Such significant common-mode voltage can be converted to common-mode current through common-mode capacitance in the system. This large common-mode current can cause overvoltage of the dc-bus of a DFE converter system where both AFE and DFE converter systems share the same ac source. This paper investigates such overvoltage phenomena occurring in a DFE dc-bus in a multiple converter system. Mechanism of such dc-bus overvoltage will be explained, and both simulation as well as experimental results are presented to confirm the theoretical analysis. Moreover, a dc-bus clamping circuit is recommended to clamp the DFE dc-bus voltage, thus any overvoltage that could trip the DFE drive can be avoided.

This paper investigates the modeling, simulation and implementation of a wind power system based on a Permanent Magnet Synchronous Generator (PMSG). A comprehensive portfolio of control schemes are discussed and verified by Matlab/Simulink simulations, in the context of grid integration and Maximum Power Point Tracking (MPPT) operations. Particularly, to investigate the Fault-Ride-Through (FRT) and robustness capabilities, various wind speed scenarios and a line voltage droop are introduced to the wind power system to investigate its dynamic performance. A reference power curve, i.e., power versus generator speed, is employed in the turbine model to implement the MPPT. In addition, a position/speed sensorless operation approach based on Sliding Mode Observer (SMO) is implemented to reduce system cost and improve control reliability. Simulation and experimental results demonstrate the robust control of the power and speed in the PMSG wind power systems.

This paper investigates the power cycling lifetime of a three-phase three-level neutral-point-clamped (NPC) inverter used in a 50-kVA adjustable speed drive (ASD). Considering the short lifetime of NPC inverters under low output frequency conditions, an improved discontinuous pulse width modulation (DPWM) method is introduced to extend the inverter lifetime. This improved DPWM method is achieved by injecting a zero-sequence signal with relative high frequency into the voltage reference signals, which is in order to obtain lower swing value of the junction temperatures in the Insulated Gate Bipolar Transistors (IGBTs). Both simulation and experimental results are presented to verify the effectiveness of this solution.

In this paper, a new type of hybrid switching device with parallel connection of SiC and Si active switches, such as “SiC JFET + Si IGBTs” or “SiC MOSFET + Si IGBTs”, is introduced and applied to a 250kW back-to-back Voltage Source Converter (VSC). Considering the different switching speeds and output characteristics of SiC and Si devices in such hybrid structure, a novel optimal switching pattern is proposed to enable the Zero Voltage Switching (ZVS) for Si IGBTs. This proposed switching pattern optimally utilizes the better conduction characteristics and lower switching loss of SiC devices based on the instantaneous load current values, therefore significantly reduces the semiconductor losses in comparison to conventional all-Si VSCs. Simulations of back-to-back converters with different hybrid devices namely, “SiC JFET + Si IGBTs” and “SiC MOSFET + Si IGBTs”, are carried out in PLECS environment. Simulation results illustrate that the overall efficiency of back-to-back VSC can be improved by up to 4.8% if conventional Si devices are replaced with “SiC+Si” hybrid devices with the proposed switching pattern.

Stator winding short-circuit faults are among the most common faults that could occur in permanent magnet synchronous machines (PMSM). Therefore, on-line diagnosis of incipient stator winding short-circuit faults plays an important role contributing to the safe operation of PMSMs. However, the efficacy of known diagnostic methods varies with the types of stator winding configurations in PMSMs. This paper compares the effectiveness of diagnosis of stator winding short-circuit faults in series and parallel winding connections of PMSMs, with the same interior permanent-magnet rotor configuration. Two existing diagnostic methods have been applied to detect the severity of stator short-circuit faults happening in both series and parallel winding connection in PMSMs. Simulation analysis has been carried out in ANSYS Maxwell to compare the severity of magnetic saturation caused by equivalent short-circuit fault in series and parallel winding connected PMSMs. Experimental results lead to the conclusion that PMSMs with parallel winding connections can mask the influence of such stator short-circuit faults under certain circumstances, and thus it is more challenging to detect such incipient faults in parallel-winding-connected PMSM in comparison with series-winding-connected PMSMs.

Permanent magnet synchronous machines (PMSM) have been widely used in various applications due to their characteristics of high power density, high efficiency, and high torque to current ratio. However, PMSMs are not immune to electrical faults, which requires an efficient and reliable condition monitoring method to avoid downtime or even catastrophic failures. This paper introduces a novel diagnostic method for PMSM stator winding short-circuit faults, which are of the most common type of faults that could occur in PMSMs. The implementation of this new diagnostic method is based on pattern identification of the loci of the machine's current space vectors. This method is computationally efficient and does not require voltage or position sensors. Experimental verification shows that such a method can detect the short-circuit fault at an incipient stage better than other existing diagnostic methods.

Multilevel converters have been widely used in traction drive systems due to their attractive output performance. However, one major disadvantage of multilevel converters is the large number of switching devices employed, which could increase the failure probability of drive systems. Thus, an effective diagnosis method for switch faults in multilevel converters is of high importance for the fault-tolerant operation of such drive systems. This paper introduces an on-line diagnosis method for open-circuit switch faults that could happen in one of the most promising multilevel converters: Active Neutral-Point-Clamped (ANPC) converter. This diagnostic method is implemented based on the comprehensive information of pole voltages, phase currents, and switching states of ANPC inverters. Compared with the existing diagnostic methods in the literature, the presented method in this paper has lower cost and shorter detection time (less than one fundamental cycle). Simulation results verified the effectiveness and robustness of the introduced fault diagnosis method.

This paper presents a flux-weakening solution by employing the voltage boost capability of Z-source inverters to overcome the voltage limitation in conventional drives for high-speed applications, e.g. hybrid/electric vehicles. In this control strategy, a flux-weakening algorithm has been developed to achieve constant output power of an interior permanent magnet synchronous motor (IPMSM). Correspondingly, a flux-weakening control strategy including a closed-loop speed control is presented. Compared to existing flux-weakening methods, this attractive control strategy allows an IPMSM to largely extend its constant power speed range and operate at higher speed with larger torque. Theoretical analysis is given in detail, and corresponding simulation results are presented to verify the presented control technique.

This paper presents a novel loss balancing modulation method for more evenly distributing semiconductor losses in multilevel active neutral-point-clamped (ANPC) converters. The presented method is achieved by optimally utilizing the redundant switching states of space vector pulse width modulation (SVPWM) in ANPC converters. A comparison of the effect of losses distribution between the proposed loss balancing SVPWM (LB-SVPWM) method and the conventional phase-shifted PWM (PS-PWM) methods is carried out in simulation. The effectiveness of the presented LB-SVPWM method is also verified in ANPC converters based on all-SiC MOSFETs. The results show that the proposed method can distribute the device losses more evenly, especially for all-SiC based ANPC converters, which can in turn improve the output power capacity and switching frequency. In addition, with utilization of the introduced loss balancing SVPWM method in ANPC converters, 15% higher output voltage and lower harmonic distortion can be achieved compared to PS-PWM modulated ANPC converters.

The rapid development of renewable energy systems (RES), especially photovoltaic (PV) energy and wind energy, poses increasing requirements for highpower, low-loss, fast-switching, and reliable semiconductor devices to improve system power capacity, efficiency, power density and reliability. The recent commercialization of wide bandgap (WBG) devices, specifically Silicon Carbide (SiC) and Gallium Nitride (GaN) devices, provides very promising opportunities for meeting such requirements with their attractive features of high voltage blocking capability, ultra-low switching losses, fast switching speed, and high allowable operating temperatures. This paper analyzed the performance benefits and application challenges of using SiC or GaN devices in both PV and wind energy conversion systems. Solutions to these challenges of using WBG devices in various RES were reviewed and proposed, and the benefits of using such emerging devices were confirmed in simulation based on a 250 kW commercial-scale PV inverter and a 250 kW doubly fed induction generator wind turbine system.

Experimental characterization of interior permanent magnet (IPM) synchronous machines experiencing winding short-circuit faults is necessary in developing diagnostics indices to be used in detecting short-circuit winding faults. Known fault indices include the current spectrum analysis, the negative-sequence components method, and the space-vector based pendulous oscillation method. This paper applies all three methods to experimental turn-to-turn short-circuit fault data acquired from a 3.5 hp IPM motor energized by a PWM voltage source inverter. The results are compared and analyzed, and since none of the three methods presented unambiguously demonstrate the existence of a winding short-circuit fault, the practical difficulties of short-circuit fault detection and mitigation are discussed in that light.

Information of rotor position and speed plays an crucial role in variable-speed wind energy conversion systems. Traditional sensors based position detection methods not only increase hardware complexity and system cost, but also face severe challenges on reliability caused by the disturbances from the varying weather and harsh operating conditions in wind energy generation sites. Thus, with the aim of eliminating position sensors and developing a reliable position self-sensing technique, this paper proposes a position self-sensing control method based on sliding mode observer for a 2 MW permanent magnet synchronous generator (PMSG) wind turbine system. In addition, a three-level neutral-point-clamped (NPC) back-to-back converter with space vector pulse width modulation (SVPWM) is developed for the full-scale power conversion, which has lower voltage stress on the switching devices and less harmonic distortion in the output voltage compared with those in traditional two-level power converters. Simulation analysis is carried out to verify the effectiveness of the proposed self-sensing method and the three-level SVPWM based back-to-back NPC converter. The simulation results soundly justified the feasibility of the proposed control scheme and power conversion strategy.

This paper presents the application and losses analysis of three-level active neutral-point-clamped (ANPC) back-to-back converters in a doubly-fed induction generator (DFIG) wind energy conversion system (WECS). A phase-shifted sinusoidal PWM strategy with the advantages of doubling the apparent switching frequency and better balancing loss distribution among switches is employed for the ANPC back-to-back converters. Comparative losses analysis between three-level ANPC and traditional NPC converters is conducted based on the applications in a 1.5 MW DFIG WECS. Moreover, dynamic modeling and control strategies for the DFIG WECS are introduced. Finally, simulation analysis of the three-level ANPC converters excited 1.5 MW DFIG WECS is carried out. The simulation results verified the advantages of ANPC converters and the corresponding modulation strategy on improving loss distribution and doubling apparent switching frequency in this WECS application.

The proposed hybrid method combines Computationally Efficient-Finite Element Analysis (CE-FEA) with a new analytical formulation for eddy-current losses in the permanent magnets (PMs) of sine-wave current regulated brushless synchronous motors. The CE-FEA only employs a reduced set of magnetostatic solutions yielding substantial reductions in the computational time as compared with conventional FEA. The 3D end effects and the effect of PWM switching harmonics are incorporated in the analytical calculations. The algorithms are applied to two fractional-slot concentrated-winding interior permanent magnet motors with different circumferential and axial PM block segmentation arrangements. The method is validated against 2D and 3D Time Stepping (TS) FEA.

The phenomenon of overvoltage at motor terminals in long-cable-fed PWM AC drives poses a severe stress on motor insulation systems. The overvoltage is typically caused by the high change rate of the inverter output voltage (dv/dt) and the surge impedance mismatch between the inverter, connecting power cable and the motor. This paper presents a comparative survey of the existing methods of overvoltage suppression, which includes passive filters at both motor terminals and inverter terminals. The design methodologies, effectiveness, and practical applicability of these passive filters are discussed through computer simulations based on Ansys/Simplorer 9.0, and the promising approaches are recommended for researchers and industrial users.

As a novel type of motor drive with promising prospect, the switched reluctance drive (SRD) has multiple control parameters and flexible control strategies. To control SRD efficiently and conveniently, a human-machine interface (HMI) is needed to set and monitor parameters in different SRD application situations. This paper presents a scheme on designing a HMI for SRD based on microcontroller P89C668. In addition to setting and displaying various operating parameters, the HMI could also control SRD to work in different states and show fault code in the circumstances of malfunction alarm. Asynchronous serial communication is employed in the communication between P89C668 and SRD main controller. Moreover, multi-class menu design is realized in the HMI menu display. Functional characteristics, hardware design, communication protocol and software design of HMI are all introduced in detail. Results of practical application demonstrate that the design scheme is feasible and reliable, and the HMI has achieved the advantages of convenient operation, complete function and reliable working.

Abstract—A four-phase 8/6 pole and 75kW switched reluctance motor drive based on 32-bit digital signal processor TMS320F2812 is designed. The details of the controller design and analysis are discussed. In addition, aiming at solving the nonlinear problems of the switched reluctance motor, fuzzy-PI hybrid algorithm is presented to control the motor speed and the phase current. Experimental results show that the hardware and software design of the switched reluctance drive system are reasonable, and the proposed fuzzy-PI double closed-loop control strategy is feasible and correct.