To further improve the system integration and convenience of the battery charging system for electric vehicles, this letter proposed a multipurpose magnetic coupler-based charging solution that integrates bidirectional on-board charger (OBC), wireless power transfer (WPT), and an auxiliary power module (APM). The proposed solution presents multiple highlights: 1) the first exhibited solution to integrate OBC, WPT, and APM in one unit; 2) magnetic integration that uses a multiwinding WPT pad to eliminate the main transformer of OBC and APM; and 3) topological integration that saves multiple active and passive devices. This letter includes a description of the system topology, operation principles of individual charging modes, a novel magnetic coupler, and the design methodology. Finally, a prototype was constructed and different charging modes were tested to validate the proposed design.

As the counterparts of alternators, the auxiliary power modules (APMs) in electric vehicles (EVs) play an irreplaceable role in bridging the high-voltage (HV) propulsion system with the low-voltage (LV) auxiliary system. With the increasing demands of fast charging, the HV propulsion system is seeing an evolution from the 400 to the 800 V system. Adapting to such trends, the APM faces the challenge of a much wider input voltage range, particularly in EVs with a reconfigurable battery pack. This article proposed a reconfigurable current-fed dual active bridge (CFDAB) based converter. It accepts a record-wide input voltage from 180 to 900 V and an output voltage from 6 to 16 V. The closed-form solutions of switching current are with consideration of coupled inductor current, the key characteristics of CFDAB, and simple control to secure zero-voltage switching and minimize the switching current. Design implementation is also discussed in this article. A 3-kW prototype with a peak efficiency of 97% was built and tested. The experimental results proved the feasibility of using the proposed topology and control for the ultrawide APM applications.

This article focuses on the design of a 650 V/150 A gallium nitride (GaN) power module. Direct bonded copper (DBC) is employed for the thermal pad insulation and the printed circuit board (PCB) is adopted for the flux cancellation, isolated bias power supply, and gate-drive-circuit integration. The packaged module exhibits high current capability (>150 A), high compactness ( $45\times 33\times9.6$ mm3), and excellent thermal resistance (0.43 °C/W). The insulated drain–source and integrated isolated gate-drive circuit also facilitate the assembly of GaN devices, particularly in high-power applications. Double pulse test (DPT) at 450 V/150 A shows ~50 V voltage spike only, which makes the proposed module well suited for high-power applications.

While the employment of wide bandgap (WBG) devices in high-frequency and high-voltage applications brings benefits such as reduced system size and improved efficiency, it aggravates the electromagnetic interference (EMI) issue due to fast switching. High-frequency EMI noise suppression relies mainly on the filter design, where the filter's performance is strongly affected by parasitics. Through analyzing the common-mode (CM) equivalent circuit of a half-bridge power module, this letter identifies the key parasitics that dominate the performance of a common-mode filter (CMF) at high frequencies. To minimize the parasitics, the concept of integrating the CMF inside the WBG power module package is developed to improve the noise attenuation. A π-type CMF is integrated with a half-bridge GaN-based power module as a prototype to validate the concept. Experiments are conducted by measuring the CM noise spectrum received by the line impedance stabilization networks (LISNs) from the hard switching of the designed power module under 70 V and 80 kHz. Comparing the measured results of the integrated CMF to the externally-added CMF, up to 50 dBμV more attenuation is achieved by the integrated CMF in the frequency range of 10 MHz to 100 MHz, verifying the theoretical analysis and the established CM equivalent circuit.

Lateral gallium nitride (GaN) high-electron-mobility transistors (HEMTs) present better electrical characteristics compared to silicon or silicon carbide devices such as high switching speed and low gate charge, but also present additional challenges on the module design. This paper discusses a high-density GaN power module with double-sided cooling, low inductance, on-package decoupling capacitors, and integrated gate drivers. The GaN dies as well as the gate drive are sandwiched between the printed circuit board (PCB) and direct bonded copper (DBC) substrate to achieve compact loop and double-sided cooling effect. Design considerations and thermal performance are analyzed. A module assembly procedure is presented utilizing the layer-by-layer attachment process. Finally, a 2.7 cm × 1.8 cm half-bridge GaN power module is fabricated and tested, achieving a low power-loop inductance of 1.03 nH, and the overshoot voltage of the switching waveform is less than 5% under a 400-V/25-A double-pulse test. The thermal resistance is 0.32 K/W, verified by simulation and experimental results. The design and assembly process can be generalized and applied to high power applications to achieve high power density and high performance.

To accelerate the dynamic response in a dual active bridge converter, feed-forward control can be applied in parallel to the conventional PI controller for closed-loop control. The transformer current thus changes significantly due to the phase shift change. A current spike can appear during load transients, particularly when using multiple phase shift modulation. Effort has been made in the previous literature to implement active compensation between two different steady-state operations to eliminate the transformer current spike; however, this results in a complicated control structure. This letter thus proposes a novel modulation method unifying the transformer current for dual phase shift and triple phase shift modulation to mitigate the transformer current spike when switching among various phase shift controls during load transients. By applying the proposed pulsewidth modulation strategy, the instantaneous value of the transformer current stays the same at the beginning of the switching period even with different steady-state modulation techniques. Also, full-operation-range zero-voltage switching can be realized for the primary side or the secondary side switches by combining with the proposed modulation strategy. An experimental prototype demonstration validates the proposed modulation strategy.

The current limiting function enables the solid-state circuit breaker (SSCB) to have proper protection coordination. It allows sustained overcurrent for a certain period while preventing the fast fault current increase in dc systems. For the conventional method of using switches alone to limit the current, the high loss results in a short withstand time and low current limiting capability of the SSCBs. In this letter, a control strategy is proposed to utilize the energy absorption component to handle the major part of the energy during the current limiting stage to increase the current limiting capability for series-connected SSCB switching cells. The proposed method is experimentally verified to have more than 3X current limiting withstand time compared to the conventional control strategy in a case study.

Common-mode voltage (CMV) is one of the major concerns in modern motor drive systems using pulsewidth modulation (PWM) controls. To alleviate the CMV issue, a series of different PWM methods have been proposed. However, due to the physical limits of the three-phase structure, none of those reduced-CMV PWMs (RCMV-PWMs) can fully eliminate the CMV. As the motor phases have been extended to even numbers, such as six phases, opportunities to eliminate the CMV by a proper modulation scheme emerge. This article proposes a new modulation method to fully eliminate or reduce the CMV for the full modulation span of a dual-three-phase motor drive system, thereby helping to shrink the CM filter. Mathematical models are built indicating its effectiveness of eliminating the CMV in the linearity range of the modulation index and reducing the CMV in the overmodulation range. Simulation results along with experiments implemented on field-programmable gate array controlled dual inverters validated the effectiveness of the proposed control algorithm.

The need for analytical models and tools to investigate common-mode (CM) and differential-mode (DM) signals in motor drive systems is evident in previous literature, which focuses on simulations and experiments. In this article, an analytical model of CM voltage (CMV) for various pulsewidth modulation (PWM) schemes is presented as a double Fourier integral (DFI) and the DM current (DMI) is described by mathematical equations. The model is applied to different modulation schemes such as space vector PWM, two types of discontinuous PWM, and active zero state PWM (AZSPWM) for two-level and three-level multiphase inverters. The impact of these four modulation schemes on the CMV and DMI is comprehensively compared across varying modulation indices. The DFI model shows that while AZSPWM has the lowest CMV around the switching frequency, it has increased sideband CMV. However, it still yields the best total CMV reduction overall. An SiC inverter is built to experimentally validate the analytical model with a range of switching frequencies of 10-40 kHz. In this system, a high-resolution field-programmable gate array (FPGA) is used to implement the control algorithm and assess the impact of control bandwidth on CMV and DMI.

The modulation strategies of dual active bridge (DAB) including single phase-shift (SPS), dual phase-shift (DPS), and triple phase-shift (TPS) have been proposed to optimize the efficiency, eliminate the reactive power, and release the current stress. While the previous literature focuses on the accurate loss model in steady states or small-signal analysis for dynamic response, the common-mode (CM) model has been largely ignored. The main contribution of this article then is to propose an analytical CM model for DAB, which considers the CM parasitic capacitors including those of grounded heatsink and transformer windings. Based on such model, the CM performance is compared among different modulation strategies. The impact of two H-bridge on the input and output CM voltage has been addressed. A prototype based on SiC devices is used to verify the proposed analytical mode under SPS, DPS, and TPS. It is found that while TPS improves the light-load efficiency it introduces the worst CM noise. Influence of the ZVS current setting on the CM performance is also discussed.

Zero-voltage-switching (ZVS) has been widely applied in widebandgap devices based on high-switching-frequency converters, for instance, dual-active-bridge isolated dc-dc converter, which consists of two H-bridges. To secure ZVS for all eight switches, previous literature mostly focuses on half-bridge to analyze switching transitions, which, however, is rather incomplete due to ignoring the impact of modulation strategies and cannot fulfill all circumstances. In this letter, the whole H-bridge is used as a unit to analyze the ZVS transient process, addressing the ZVS setting in different modulation strategies. The minimal initial inductor energy to complete the ZVS process is also quantified, which in return can reduce the transformer current, thereby enhancing the efficiency. Furthermore, the accurate ZVS transition time is derived incorporating with the nonlinearity of switch output capacitance, which can be further used to set the dead-band time. An H-bridge prototype with SiC devices is built up to verify the theory proposed in this letter.

An auxiliary power module in electric vehicles is a dc/dc converter bridging the high-voltage propulsion battery with a low-voltage auxiliary system. In the coming era of connected and autonomous vehicles, the power rating of such dc/dc converters is expected to surge from 2.5 to 6 kW. In addition, there is the challenge of a wide operating voltage range, e.g., 250-450 V required by the high-voltage propulsion battery and 10-16 V at the low-voltage auxiliary battery. To meet these voltage and power challenges, this article proposes a two-stage bidirectional design, i.e., interleaved buck + dc transformer (DCX) that offers full voltage range coverage, 3.5 kW rated power, and peak power of >6 kW. Experimental results indicated >96% efficiency, owing to the zero-switching loss of DCX. Furthermore, the precharge mode that charges the input dc-bus capacitor with the low-voltage battery is accomplished using the inner phase shift control of the DCX stage. DC-bias blocking capacitors on the low-voltage side are replaced with a simple, unique dc-bias detection circuit that samples and eliminates the dc-current offset of the transformer. Simulation and test results confirm that the proposed method effectively detects and eliminates the dc-bias current.

Dual-active-bridge (DAB) circuit is an excellent candidate for a high-efficiency, high-power density, and bidirectional electric vehicle charger. Unlike resonant circuits employing auxiliary inductors and capacitors, DAB minimizes the usage of passive components. The challenge, however, lies in the difficulty of securing zero-voltage switching (ZVS), particularly at light-to-medium load when using the conventional single-phase-shift (SPS) control. This is of utmost importance not only for the sake of the efficiency, but also for minimizing the switch-bridge crosstalk caused by the hard switching-on, thereby enhancing the system reliability. Although dual-phase-shift (DPS) and triple-phase-shift (TPS) can be the answer, they do introduce side effects such as larger switching-off current. This article systematically integrates SPS, DPS, and TPS to maximize full-power ZVS range for both steady state and transient operations in EV chargers. This article plots ZVS boundaries over the full power range, categorizes all operations into nine modes, and proposes a smooth transition method among all operation modes. Dead band is also incorporated in the ZVS boundary setting. Experimental results on a SiC-based charger validate the effectiveness of this method of widening ZVS range for output voltage of 200-450 Vdc and power of 0-20 kW, achieving smooth transitions among various operation modes, and suppressing the switch crosstalk, thereby securing high charger reliability.

Wide-bandgap (WBG) devices are considered to be a better alternative to silicon switches to realize high-efficiency and high-power-density power electronics converters, such as electric vehicle (EV) onboard chargers. The two major challenges of GaN devices are their relatively high cost (~5 times compared to Si) and much smaller footprint than Si, which though is preferred in the high-power-density application is preferred but brings thermal challenges. Much like SiC is paralleled with Si, and GaN could be paralleled with Si to resolve these challenges. In this article, gallium nitride (GaN) high-electron-mobility transistors (HEMTs) are paralleled to various Si MOSFETs. Two different triggering approaches are considered: one adds a time delay between gate signals and the other uses a pulse triggering technique. Both methods ensure that the GaN endures the switching loss, while the Si switches conduct the majority of the current, thereby maximizing the advantages of both types of switches. To follow is a comprehensive study of the critical transient processes, such as the gate cross talking between Si and GaN, current commutation in the dead band, voltage spikes during the turn-off caused by parasitics, the thermal performance, and the cost analysis. Demonstrated success testing this approach at 400 V/80 A provides evidence that this is a possible approach in the onboard EV battery charger applications. The success of testing under 400 V/80 A makes it possible to an onboard EV battery charger.

The depletion of fossil fuels, the increase of energy demands, and the concerns over climate change are the major driving forces for the development of renewable energy such as solar and wind. However, the intermittency of renewable energy has hindered the deployment of large-scale intermittent renewable energy, which therefore has necessitated the development of advanced large-scale energy storage technologies [item 1) in the Appendix]. The use of large-scale energy storage can effectively improve the efficiency of energy resource utilization and increase the use of variable renewable resources, energy access, and end-use sector electrification [items 2) and 3) in the Appendix]. Over the years, considerable research has been conducted on many types of energy, such as thermal energy, mechanical energy, electrical energy, and chemical energy, using different types of systems such as phase change materials, batteries, supercapacitors, fuel cells, and compressed air, which are applicable to various types of applications, such as heat and power generation and electrical/hybrid transportation [items 4) and 5) in the Appendix].

Considering the fact that electric vehicle battery charging based on the current charging station is time-consuming, the charging technology needs to improve in order to increase charging speed, which could reduce range anxiety and benefit the user experience of electric vehicle (EV). For this reason, a 1 MW battery charging station is presented in this paper to eliminate the drawbacks of utilizing the normal 480 VAC as the system input to supply the 1 MW power, such as the low power density caused by the large volume of the 60 Hz transformer and the low efficiency caused by the high current. The proposed system utilizes the grid input of single-phase 8 kVAC and is capable of charging two electric vehicles with 500 kW each, at the same time. Therefore, this paper details how high-voltage SiC power modules are the key enabler technology, as well as the selection of a resonant-type input-series, output-parallel circuitry candidate to secure high power density and efficiency, while intelligently dealing with the transient processes, e.g., pre-charging process and power balancing among modules, and considering the impact on the grid, are both of importance.

For any voltage above 600-V dc, it is usually recommended to use 900-1200-V SiC MOSFETs instead of GaN high-electron-mobility transistors (HEMTs), given presently commercial GaN HEMTs have the maximum voltage rating up to 650 V. This paper is an attempt of employing 650-V E-mode GaN HEMTs to build a three-level bidirectional dc/dc converter, with the input as an 800-V battery, the output as the ~400-V dc grid, and half of the switches working at the hard-switching mode. The active-balancing control instead of using clamping diodes in the conventional neutral-point clamping topology is adopted, aiming at higher efficiency. Simulation based on the double-pulse test results shows that such a design strategy with GaN has a better efficiency over the conventional 1200-V SiC MOSFETbased buck/boost converter. Two bottom-cooled GaN HEMTs are in parallel to enhance the power capability and efficiency, which require the special focus on the parasitic parameters. The effects of parasitics, especially the stray inductance in the current commutating loop and the gate drive loop during switching transitions, have been comprehensively analyzed in this paper. Experimental results under 800-V bus voltage are presented to verify the proposed solution.

As a new application area of electric vehicles, vehicle to home (V2H) recently becomes one of the most attractive research areas. In this paper, a three-phase four-wire inverter using four half-bridge legs is adopted to realize the V2H functionality. Such three-phase inverter acts as the grid-side ac/dc part of the battery charger. In order to deal with the imbalanced load, an independently controlled neutral module has been adopted to form the neutral line and provide the path for the zero-sequence current, together with split dc-bus capacitors. Each phase employs the independent sinusoidal pulse width modulation control with the virtual resistor paralleled with the load, namely, notch-filter-incorporated capacitor voltage feedback control, which damps harmonics around the resonant frequency at various load conditions. In addition, this paper quantifies the load imbalance versus the dc-link voltage oscillation and provides the guidance for the selection of the dc-link capacitance. Finally, a 10-kW three-phase four-wire inverter working at the V2H mode is built and tested, with the three-phase imbalanced load imposed to validate the proposed design and control strategy.

Though wide bandgap devices are believed to be promising candidates for next-generation high-efficiency and high-power-density power electronic converters, two major challenges remain, high cost (more than twice of Si) and less options (the maximum power rating for GaN is only 650 V/60 A). From the device level, paralleling GaN with Si can inherit merits of both GaN devices (superior switching performance) and Si devices (affordable with high-current capability). In this paper, first, GaN HEMTs are paralleled to a TO-247 Si MOSFET to form a high-current switching cell for a 6.6-kW electric vehicle (EV) charging module. A time delay is added between the switch gate signals to make GaN endure the switching loss and Si conduct majority of the static current. Critical dynamic behaviors, such as the current overshoot to the GaN, current distribution during the dead time, and voltage spike during the turn off caused by parasitics, are comprehensively discussed. From the system level, series connecting the input and paralleling output of multiple such modules yield a sub-MW EV charging station. Once one phase drops, the related phase can act as the active filter, while other two phases still work to charge the battery.

Compared with grid to vehicle (G2V) and vehicle to grid (V2G) modes, electric vehicle (EV) battery chargers are more vulnerable to power quality problems at the autonomous mode, i.e., creating its own electric grid during the grid blackout while facing unbalanced and nonlinear loads. Active damping is another common challenge given most charger equip LC filters at grid-end voltage-source inverters (VSIs). In this article, an output-voltage control with harmonic compensation plus virtual impedance term is proposed to achieve high power quality and necessary damping, respectively. The physical meaning of the virtual impedance is further explained, and the voltage loop with PI plus multiresonant terms is analyzed in depth. More importantly, the analytical solutions and procedures to design such controllers considering the time delays are proposed. Finally, simulation results and experimental data on an EV battery charger prototype using SiC devices, which is made of one VSI and one isolated dc/dc converter, validate the effectiveness of the proposed design methodology.

A high-frequency injection (HFI) sensorless control for interior permanent magnet synchronous motors with enhanced precision and widened speed range is proposed in this paper. The injection frequency reaches up to 2 kHz under a 50~100 kHz silicon carbide (SiC)-based three-phase inverter. In addition to the high switching frequency, the field-programmable gate array (FPGA) is utilized to achieve high control bandwidth (>200 kHz) when implementing the field-oriented control algorithm. The benefits of high switching frequency and high control bandwidth in senseless controls are explained theoretically, i.e., leaving enough room for the injection frequency by using SiC while tuning down the noise-to-signal ratio by using the FPGA. Experimental results verified that such manners improved the position estimation and lifted the injection frequency effectively, which further allows us to widen the motor speed range under the HFI sensorless control from 0 to 500 r/min with the conventional Si+DSP design to 0~1200 r/min with the proposed SiC+FPGA.

As two exemplary candidates of wide-bandgap devices, SiC MOSFETs and GaN HEMTs are regarded as successors of Si devices in medium-to-high-voltage (>1200 V) and low-voltage (<;650 V) domains, respectively, thanks to their excellent switching performance and thermal capability. With the introduction of 650 V SiC MOSFETs and GaN HEMTs, the two technologies are in direct competition in <;650 V domains, such as Level 2 battery chargers for electric vehicles (EVs). This study applies 650 V SiC and GaN to two 240 VAC/7.2 kW EV battery chargers, respectively, aiming to provide a head-to-head comparison of these two devices in terms of overall efficiency, power density, thermal performance, and cost. The charger essentially is an indirect matrix converter with a dual-active-bridge stage handling the power factor correction and power delivery simultaneously. These two chargers utilise the same control strategy, varying the phase-shift and switching frequency to cover the wide input range (80-260 VAC) and wide output range (200 V-450 VDC). Experimental results indicated that at the same efficiency level, the GaN charger is smaller, more efficient and cheaper, while the SiC charger has a better thermal performance.

An ac/dc + dual-active-bridge (DAB) circuit was found as one solution for the high-efficiency and high-power-density electric vehicle charger. One control option is to let ac/dc part only convert the grid voltage to a double-line-frequency folded sine wave, yielding near-zero switching loss of the ac/dc part and leaving the DAB stage to control both power factor and power delivery. Such a zero-to-peak input voltage and wide-range output voltage can obstruct the zero-voltage switching (ZVS) for the DAB stage, which is a must for high-efficiency applications even with SiC devices. While the conventional single-phase shift loses ZVS at light load, and the variable-switching-frequency dual phase shift (DPS) creates the grid-current distortion at the light load, this paper employs multiple-phase-shifts (MPS) control, which essentially is a fixed-switching-frequency triple-phase-shift (TPS) control at light-load conditions and jumping to DPS at medium- and heavy-load conditions. While the TPS control will sacrifice the system efficiency by introducing the circulating current, a multiobjective optimization is employed to optimize the current stress and efficiency simultaneously, using the database of the double-pulse-test result. Experimental results on a SiC-based charger validated the effectiveness of the proposed control algorithm, that is: 1) high efficiency(>97%) at heavy load (7.2 kW); 2) smooth sinusoidal current without bumps at zero-crossing points from the whole-load range; and 3) the smooth transition between the heavy load and light load.

In this paper, an enhancement-mode GaN highelectron mobility transistor (HEMT)-based 7.2-kW single-phase charger was built. Connecting three such single-phase modules to the three-phase grid, respectively, generates a three-phase ~22-kW charger with the> 97% efficiency and > 3.3 - kW/L power density, superior to present Si-device-based chargers. In addition to GaN HEMTs with fast-switching transitions yielding high efficiency, the proposed charger employs the dc/dc stage to control the power factor and power delivery simultaneously, yielding little dc-bus capacitance and thereby high power density. To secure the soft switching for all switches within full voltage and power ranges, a variable switching frequency control with dual phase shifts was adopted at high power, and a triple phase shift was employed to improve the power factor at low power. Both control strategies accommodated the wide input range (80-260 VAC) and output range (200-450 VDC). A closed-loop control for the three-phase charger was realized to minimize the output current ripple and balance the power among three single-phase modules. Experimental results validated this design.

Wide-bandgap (WBG) devices such as SiC and GaN switches are regarded as next-generation power semiconductors, due to their superior performance over conventional Si devices, for instance, a low switching loss and high thermal conductivity. Its bottleneck, however, is the high cost, which is critical for renewable energy and automotive industries. This study adopts SWISS AC/DC rectifier topology for the three-phase 380-480 VAC along with an isolated DC/DC converter, indicating such topology can maximise the advantages of Si (low conduction loss) and SiC (high switching loss), altogether thereby yielding the high performance and low cost. A novel space-vector pulse width modulation (SVPWM) was proposed to control such a current-source power factor correction, where only two SiC devices were adopted for the DC-bus voltage control. The closed-loop control of the grid current is realised for the unity power factor. Such topology further allows the DC-bus voltage to be varied with the output voltage, thereby minimising the system loss. A final prototype was built to charge a 48 V battery at 11 kW. Experimental results validated the effectiveness of such battery charger design.

Compared to conventional electrical-vehicle(EV) on-board chargers utilizing a front-end Power-Factor-Correction(PFC) + an isolated DC/DC converter, which limits the wall-to-battery efficiency to ~94%, a new control strategy using variable switching frequency(VSF) and variable phase shifts frees the PFC stage thereby getting rid of the DC link capacitor and further increasing the system efficiency and power density. The challenge is to secure zero-voltage-switching (ZVS) turn-on for all switches within the full-power range. In this paper a novel VSF single-dual-phase-shift(SDPS) control strategy is proposed, which consists of three control freedoms, i.e., two phase shifts and one variable switching frequency to secure ZVS and achieve PFC simultaneously. ZVS boundaries are pictured and compared among single-phase-shift(SPS), dual-phase-shift(DPS) and the proposed single-dual-phase-shift(SDPS) control. Simulation results and experimental validation through a level-2 EV on-board charger indicate that by using the proposed SDPS control, both ZVS and PFC are secured not only for the heavy load but also for the light load, without sacrificing the system efficiency.

An ac/dc + dual active bridge (DAB) circuit was found as one solution for the high-efficiency and high-power-density electric vehicle charger. One control option is to let the ac/dc part only convert the grid voltage to a double-line-frequency folded sine wave and let the DAB stage handle both the power factor (PF) and power delivery. While conventional single-phase-shift tends to lose zero-voltage switching (ZVS) at light load and the variable-switching-frequency dual-phase-shift (DPS) sacrifices the light-load performance, this letter proposes a multiple-phase-shift control, which allows for a fixed-switching-frequency triple-phase-shift (TPS) control at the light load to enhance the grid power quality. At medium- and heavy-load conditions, a phase-shift jump from TPS to DPS is performed to reduce the circulating current and improve efficiency. The proposed control strategy secures ZVS, realizes unity PF accurately and minimizes the control complexity. Experimental results on a SiC-based 7.2-kW charger validated its effectiveness and the smooth transition between the heavy load and light load.

An indirect matrix converter is employed directly converting the grid ac to the battery voltage, with the dual-active-bridge taking care of the power factor correction and power delivery simultaneously. Such circuit is regarded as one candidate of the high-efficiency and high-power-density electric vehicle onboard chargers, if the double-frequency current ripple to the battery is tolerated. Instead of optimizing the overall charger, this paper is focused on adopting variable switching frequency with multiple phase shifts to accommodate the wide input range (80-260 Vac) and output range (200 V-450 Vdc). In addition to the phase shift between the transformer primary-side and secondary-side voltage, one extra phase shift is added to the primary-side H-bridge when the instantaneous input voltage is higher than the reflected output, otherwise, to the secondary side. The goal is to secure zero-voltage-switching for all switches at all voltage range. Such control strategy is further optimized incorporating with the switch parasitic capacitance and deadband settings. To further enhance the charger performance, GaN HEMTs are equipped to the on-board charger aiming at higher efficiency and higher power density than Si devices. Experimental results indicated that such charger with proposed control strategy embraces the peak efficiency of >97% at 7.2 kW and a power density of ~4 kW/L.

Wide-bandgap devices, such as silicon-carbide metal-oxide-semiconductor field-effect transistors (MOSFETs) and gallium-nitride high electron mobility transistors (HEMTs), exhibit an excellent figure of merits compared to conventional silicon devices. Challenges of applying such fast switches include accurate extraction and optimization of parasitics especially when 6high-efficiency operation, all of which require the comprehensive understanding of such switch especially its interaction with peripheral circuits. Particularly for the enhancement-mode GaN HEMTs without the intrinsic body diode, when reverse conducting, its high voltage drop causes a high dead-time loss, which has rarely a concern in silicon devices. This paper focuses on 650V/30~60A enhancement-mode GaN HEMTs provided by GaN Systems, analytically models its switching behaviors, summarizes the impact of parasitics and dead time, and applies it in two DC/DC converters. Systematic design rules are generated not only for soft switching but also for hard switching applications.

Wide-bandgap (WBG) devices such as Gallium-Nitride (GaN) High Electron Mobility Transistors (HEMTs) have become popular in the power electronics industry as they offer a lower switching loss, higher thermal capability and higher power density than conventional silicon devices. As an attempt of applying WBG devices to the wireless charging technology, this paper adopts two different types of normally-off GaN HEMTs. One adopts the cascode structure provided by Transphorm Inc, operated under 800kHz to charge a battery pack on an electric scooter at 48 V/500W, with the air gap between the transceiver and receiver of ~10cm. The other is enhancement-mode GaN HEMTs provided by GaN Systems Inc, operated at ~6MHz to use one transceiver to charge multiple cell phones @~20W. Both of these chargers have no magnetic cores to reduce the cost and weight. Experimental results show both types of GaN HEMTs significantly increased the charging efficiency over conventional Si devices. Challenges of applying such fast-transition devices are discussed, e.g., common-source inductance and the gate-drive-loop parasitic.

It is expected that wide-bandgap devices like silicon-carbide MOSFETs and gallium-nitride HEMTs could replace Si devices in power electronics converters to reach higher system efficiency. This paper adopts the conventional half-bridge LLC topology to realize a 10-kW all-SiC bidirectional charger used in electric vehicles. Though it is a well-known topology for the unidirectional charger, it has not been comprehensively explored for the bidirectional energy flow yet. A double-pulse-test (DPT) platform is utilized to provide accurate power losses. A state-space model is built to obtain accurate switching current waveforms, which is eventually combined with the DPT results to accurately predict the system efficiency. Based on this model, to further enhance the system efficiency, the dc-bus voltage is varied with LLC dc/dc converter running at the resonant frequency through the whole power range. Experimental results validated that the proposed approach could realize the bidirectional power flow. By varying the dc-bus voltage, the V2G and G2V modes reach ~96 % wall-to-battery efficiency.

The switching frequency is one of the most important control parameters of the dc/ac inverter. In most motor drives for transportation, it is set as a constant value at some specific torque or speed. The variable switching frequency pulse width modulation (VSFPWM), which changes the switching frequency cycle to cycle based on a current ripple prediction method, has been proposed in previous literatures and realized in resistance- inductance (RL) loads and induction motors (IMs). It proves effective to increase the overall system efficiency and improve electromagnetic interference (EMI) performance. However, the previous current ripple prediction method encounters difficulty in dealing with more complex motors, e.g., interior permanent magnet (IPM) motors, which is widely used in electric vehicles. As a result, the benefits of VSFPWM cannot be fully utilized for IPM drive systems. This paper proposed a new current ripple prediction method using the d-q transformation instead of the conventional Thevenin equivalent circuit method and successfully implemented VSFPWM to IPM drives. Simulation and experiments on a 400-V IPM test bench validated the effectiveness of the method, which will vary the switching frequency from cycle to cycle in order to 1) restrain the three-phase current ripples; 2) increase the overall system efficiency; and 3) enhance the system electromagnetic capability (EMC).

This paper proposes the design of a 2.5-kW 400/12 V high-efficiency isolated dc/dc converter for electric vehicles. The designed system accommodates the wide-range input voltage (450 V-220 VDC) and output voltage (16 V-6 VDC). An LLC halfbridge topology is adopted as the primary side of the dc/dc converter. For the secondary side, a novel synchronous rectification control (SRC) strategy is developed to switch metal oxide semiconductor field effect transistors (MOSFETs) through accurately tracking the target switching moments. Experimental results were carried out to charge the on-board 12-V battery and validate the proposed control algorithm. The maximum system efficiency is 93.2%. System power loss is also itemized.

This paper presents an open-loop control strategy, dubbed the Hijacker algorithm, which governs startup from standstill, low-speed operation in open-loop, the transition to closed-loop, and sensorless motor control. The goal of the Hijacker is to eliminate the torque ripple encountered by a sudden switch from the open to closed loop operation, providing a smooth transition between the two control mechanisms and reliable operation over the motor's entire speed range without the use, or added cost of speed/position sensors. Implementation of the Hijacker exhibits extreme simplicity, so as not to add heavy computational loads on the processor. The algorithm, along with its development and justification, is then validated through both simulation and the test bench using a 1.4-kW/4500 rpm brushless dc motor.

A 12-V motor drive system using an onboard battery is promising in vehicle applications, e.g., to rotate an air pump to adjust its air delivery to the burner, thereby providing autonomous exhaust temperature control for the conventional diesel engine vehicle. The 12-V/1-kW motor drive system proposed in this paper consists of a series-resonant LLC MOSFET full-bridge converter, which provides high-efficiency power transfer by implementing zero voltage switching and boosts the dc bus to ~300 V, and an insulated-gate bipolar transistor inverter, which provides the high-side phase currents to a 1-kW/6000-r/min brushless dc motor (BLDC). This design secures the high efficiency, low cost, and low volume. Meanwhile, with the variable output voltage of this dc/dc converter, this paper realizes a commutation torque-ripple reduction method, which will minimize the mechanical vibration. Experimental results on this prototype system demonstrate that: 1) the LLC dc/dc part efficiency is 97.6% with 92% of the inverter efficiency; and 2) the motor commutation torque ripple is reduced close to zero.

This study proposes a design and development of a wireless power transfer system to charge the battery in electric vehicles. A parallel-parallel topology is adopted to realise 10-15 cm-distance power transfer using the resonance theory. Finite-element method is used to extract the coil parameters. The advantages of the proposed design compared with the previous similar research are (i) low operational frequency (42 kHz) which avoids the electromagnetic interference to the on-board automotive electronics equipment and (ii) low electric stress to the semi-conductor switches through using zero-voltage-switching technique. A 2 kW prototype to charge 200 V battery was built to experimentally verify the theoretical analysis. The overall system efficiency is ~86%.

Presents corrections to the above titled paper (ibid., vol. 23, no. 6, pp. 2905-2914, Nov. 2008).

This paper proposed an enhanced dc preexcitation for a variable-voltage variable-frequency-controlled induction motor drive system. Voltage vectors were adjusted according to the reactive component of the motor current, which promptly established the effective value of the motor flux linkage at the preexcitation stage and restrained its trajectory strictly as a round circle all through the starting process. The enhanced dc preexcitation control led to more negligible flux-linkage distortion, less torque vibration, and significantly smaller inrush current. Experiments on a 380-VAC/315-kW adjustable speed drive system validated the effectiveness of the proposed method.

With the development of plug-in hybrid electric vehicles (PHEVs), power electronics plays an increasingly important role in electric power train systems. The economic and reliable design of these power electronic systems, e.g., dc/ac inverter and battery charger, will be the inward search to popularize electric vehicles. As an extension of system-level safe operational areas (SSOAs) proposed in our previous literature, this paper details the criteria and mathematical models of SSOA for a battery charger and a three-phase two-level dc/ac inverter. Operational areas were established based on the SSOA. Thermal characteristics of the semiconductor devices, operational modes, and load characteristics were enclosed to enhance the mathematical models. Experiments on a 5-kW charger and a 55-kW/380-VAC inverter validated the effectiveness of SSOA.

Three different control algorithms, traditional single-phase-shift control, dual-phase-shift control (DPSC), and model-based phase-shift control (MPSC), are implemented in a hardware setup and compared for a full-bridge-based isolated bidirectional dc-dc converter. The differences among their dynamic performance and steady-state operations are quantitatively analyzed. Experimental results showed good agreement with theoretical analysis. MPSC showed the best dynamic performance, while DPSC can eliminate reactive power under light-load conditions.

Various short-timescale transients exist in power electronic converters, particularly in high-voltage and high-power systems. The timescales of these transients are from nanoseconds to microseconds, including a switching transition of power semiconductor devices, commutating processes, and drive signal transmissions. These transient processes directly affect the performance and reliability of power electronic systems. Therefore, it is necessary to study these short-timescale processes. Based on two high-power prototype power converters, a 6000-V/1250-kW three-level adjustable-speed drive and a 10-kW/600-V DC-DC converter, this paper studies the various abnormal behaviors of the converters that occurred during the operation of these converters. Dead bands and accumulated switching errors are also investigated. A combined microscopic pulsed power and macroscopic control strategy was proposed for the design of power electronic converters. Three new concepts for power electronic converters are introduced and validated in this paper: (1) sneak pulse; (2) energy dead band; and (3) transient commutating topology.

This paper proposes a novel dual-phase-shift (DPS) control strategy for a dual-active-bridge isolated bidirectional DC-DC converter. The proposed DPS control consists of a phase shift between the primary and secondary voltages of the isolation transformer, and a phase shift between the gate signals of the diagonal switches of each H-bridge. Simulation on a 600-V/5-kW prototype shows that the DPS control has excellent dynamic and static performance compared to the traditional phase-shift control (single phase shift). In this paper, the concept of ldquoreactive powerrdquo is defined, and the corresponding equations are derived for isolated bidirectional DC-DC converters. It is shown that the reactive power in traditional phase-shift control is inherent, and is the main factor contributing to large peak current and large system loss. The DPS control can eliminate reactive power in isolated bidirectional DC-DC converters. In addition, the DPS control can decrease the peak inrush current and steady-state current, improve system efficiency, increase system power capability (by 33%), and minimize the output capacitance as compared to the traditional phase-shift control. The soft-switching range and the influence of short-time-scale factors, such as deadband and system-level safe operation area, are also discussed in detail. Under certain operation conditions, deadband compensation can be implemented easily in the DPS control without a current sensor.

This paper discusses the short-time-scale transient processes in an isolated bidirectional dc-dc converter with phase-shift control. The deadband effect on the steady-state and transient commutating process are analyzed. The current variations caused by phase-shift errors at the boundary conditions are simulated and validated through experiments. The concept of ldquoenergy deadbandrdquo is introduced to describe those specific transients where no energy flows from source to load or load to source. A set of strategies are proposed to increase the system robustness. Simulation and experiments on a 200-V/400-V, 6-kW DC-DC converter prototype validated these strategies.

The feature of the integrated gate-commutated thyristors (IGCTs) makes them have excellent performance in high-voltage high-current field. The high integration of drives and devices makes it very convenient to use them. In order to examine the dynamic characters of switch devices in high-power three-level inverter, an experimental test for IGCTs and diodes equipped in inverter is proposed and described in detail. The characteristics of switch devices are compared and evaluated experimentally. The relation between the devices' switching behavior and the other elements in the inverter, such as the inverter's structure, the topology position of devices, the stray inductances in commutating loops, etc., are analyzed. Moreover, the busbar structure is improved, and the key pulsewidth-modulation parameter of the inverter is determined. Finally, the advantages of the experiment are summarized in the conclusion.

Integrated gate commutated thyristors (IGCTs) are commonly used for high-voltage three-level pulsewidth-modulation-controlled voltage-source inverters. IGCTs are utilized in series connection when the output voltage is greater than the maximum rated voltage. Special measure must be taken to ensure the safety and reliable operation of the inverters, and to equalize the voltages across the IGCT modules, such as the dynamic voltage-balancing circuit using an snubber circuit. Based on the IGCT functional model, this paper presents an optimization design procedure of a high-voltage-balancing circuit for a 6-kV/1250-kW inverter. A tradeoff is made between the voltage imbalance, maximum turn-on current, endurance, and losses. Simulation and experiments validate the feasibility of this procedure. In addition, the specific transient processes in the three-level topology with voltage-balancing circuit are simulated, and their inner mechanisms are analyzed.

The 10-kV SiC device imposes high insulation requirements on the corresponding power stage design. As the voltage stress and clearance distance increases, achieving a compact design of the converter will be challenging. In this paper, a compact power stage design is realized by adopting a new heatsink configuration. With the new heatsink configuration, a field shaping structure is proposed to suppress concentrated electric field close to the edges, so that the clearance between heatsinks can be reduced. Simulation and experimental tests have validated the design. The proposed design has been tested up to 6250 V/10 A, and the gate drive and bus-bar design are also discussed in this paper.

To dissipate heat effectively, a sufficient cooling system is required for a five-level MMC (Modular Multilevel Converter) based on 10 kV, 100 A power modules. However, achieving efficient heat dissipation necessitates a large cooling system, which in turn reduces the overall power density of the converter. Additionally, ensuring proper insulation between the high voltage switching devices and cooling components poses another challenge. This paper addresses these issues by presenting a detailed numerical design procedure for liquid cooling and selecting appropriate coolant with high dielectric strength. Air cooling with specific clearance and creepage distances is also presented. These two types of cooling methods are compared in terms of thermal performance, size, cost and installation effort. The effectiveness of the design is validated through experimental measurements.

This paper presents the design of a megawatts (MW) level modular multilevel converter (MMC) phase-leg for 13.8 kV medium voltage (MV) grid based on Wolfspeed 10 kV SiC MOSFET XHV-9 half bridge module. Compared with the 10 kV SiC single die discrete device, the 10 kV SiC multi-die module has higher di/dt, higher dv/dt (for loss reduction), and more stringent protection requirement, posing new challenges on the MW-level MV power converter design based on this 10 kV SiC module. Detailed MMC submodule and system design to address these challenges are presented. A protection strategy for this 10 kV SiC MOSFET power module is proposed, which can detect the short circuit within 200 ns and effectively limit short circuit current to within 200 A for short circuit fault at 6 kV dc voltage. Hardware is built and experimental results of the MMC submodule test at 6 kV dc voltage, MMC phase-leg test at 12 kV dc voltage, and 8-level converter test up to 23 kV are demonstrated and verify the effectiveness of the presented design.

This paper presents the switching cell design for medium voltage (MV) flying capacitor converter (FCC) with emerging 10 kV SiC MOSFET using a 5-level FCC for the 13.8 kV MV grid as an example. The design of flying capacitors and decoupling capacitors to achieve compact size, loop inductance minimization, high voltage insulation, and good scalability is discussed. The flying capacitor switching cell double pulse test (FCC-DPT) concept is proposed for switching evaluation. With detailed switching loop characterization and analysis, the switching speed of this 10 kV 20 A SiC MOSFET discrete device is pushed to exceed 100 V/ns. Hardware of the 5L-FCC phaseleg is built and continuous power test experimental results up to 23 kV dc voltage are demonstrated.

As the enabler of the direct current (DC) power distribution system, DC solid-state circuit breaker (DC-SSCB) has been extensively studied at the breaker-level (e.g., topology, energy absorption circuit, gate driver, and control) with limited system-level considerations, which is also crucial. This paper provides an all-in-one solution with integrated circuitries as the fault detector, actuator for semiconductor’s operating status regulation, and coordinated control to seamlessly transition from one mode to another (e.g., normal mode, precaution mode, i2t mode, and interruption mode). This allows the developed SSCB to limit system fault current not exceeding short-circuit current rating (SCCR) and take different responses under different fault cases. First, two improved fault detection circuits are introduced to better serve the SSCB application. Second, four operation modes are proposed for SSCB to realize system-friendly functions. Third, by leveraging four different operation modes, a control strategy is demonstrated to take different actions based on different fault cases. Finally, the feasibility and the effectiveness of the proposed system-friendly 200V/10A SSCB is validated with experimental results.

Gallium Nitride (GaN) high electron mobility transistors (HEMTs) are superior for cryogenically cooled solid-state circuit breakers (SSCBs) in future aircraft applications owing to their low on-resistance and high saturation current. However, during the high current turn-off, it is found that potential voltage and current ringing could happen to damage the device. In this paper, the turn-off failure mechanism of 650V/ 150A GaN bare dies are analyzed, which could be due to the instability of paralleled switching cells in one GaN bare die. A solution is proposed to use an RC snubber to reduce the overlap of $v_{ds}$ and $i_{d}$ in the turn-off process to avoid the unstable region where the hard-switching trajectory goes through. Experiments are conducted to verify the effectiveness of the proposed solution. With the reduced overlap between $v_{ds}$ and $i_{d}$, the GaN HEMT successfully turns off the 550 A objective current.

Operating power converters at cryogenic temperature (<-153°C) can improve efficiency and power density. However, the reliable operation of power converters depends on satisfactory performance of all critical components at cryogenic temperature. While most of the critical components have been studied at cryogenic temperatures, some electronic components necessary for electrical isolation in signal circuits of a medium voltage power converter are yet to be evaluated extensively. This work studies the cryogenic performance of isolated auxiliary power supplies (APS), digital isolators, fiber optics, and isolation amplifiers to identify the well-performing candidates and to investigate the possible reason of failures at cryogenic temperatures. It is observed that some isolated APS with high isolation voltage and isolation amplifiers can work satisfactorily at cryogenic temperatures. The digital isolators are found to be more suitable for cryogenic operation than fiber optic links, even though the latter has better noise immunity.

To increase the current interrupting capability for the DC solid-state circuit breaker (DC-SSCB), power semiconductors need to possess a higher pulse current. Moreover, for the power electronics protection system, it is also important to enable the system with a fault current limitation capability. Accordingly, this paper aims to design an intelligent gate drive for DC-SSCB, which can operate in cryogenic conditions to increase interrupting capability of the SSCB. Meanwhile, the proposed intelligent gate drive also enables the SSCB to operate in the current limitation mode to limit the overcurrent in the aviation system. The current limitation mode can help the aviation system limit the inrush current during startup and realize fault ride-through for the healthy part when the fault occurs. Finally, test results based on a 200V/150A SSCB with the current limitation mode prototype verify the proposed intelligent gate drive design for SSCB with cryogenic cooling.

The significant on-resistance reduction, the faster switching speed, and the capability of being operated at a higher current at cryogenic temperature make Gallium Nitride (GaN) High Electron Mobility Transistors (HEMTs) attractive to cryogenically cooled power electronics applications. Moreover, the positive temperature coefficient of on-resistance makes GaN HEMTs suitable for the parallel operation. In this article, the design of a solid-state circuit breaker (SSCB) with two 650V/150A GaN HEMTs in parallel is presented. The designed SSCB circuit is tested at cryogenic temperature (<-153°C). -The results demonstrate the capability of the SSCB module with paralleled GaN-HEMTs to interrupt high current (1000A) at cryogenic temperature.

The efficient electrical detection and manipulation of antiferromagnetic moments is challenging. We show that the spin current and antiferromagnetic moments in the topological insulator/antiferromagnetic insulator bilayer (Bi,Sb)2Te3/α-Fe2O3 can be controlled via topological surface states. The spin current can control the moment rotation in the antiferromagnetic insulator by means of a giant spin-orbit torque (SOT) generated by the topological surface states, where the switching is detected by the magnetoresistance signal at the interface, named as Rashba-Edelstein magnetoresistance (RE-MR). The required threshold switching current density is 3.5 × 106 A cm−2 at room temperature, which is one order of magnitude smaller than that required in heavy-metal/antiferromagnetic insulator systems, exhibiting the potential for ultralow energy consumption. Notably, the topological surface states of (Bi,Sb)2Te3 can be modulated by applying a gate voltage, giving rise to electrically controllable RE-MR and SOT switching. Consequently, when the Fermi-level location of (Bi,Sb)2Te3 is tailored by electric fields, the signal of RE-MR is enhanced and the threshold switching current density is further decreased.

As the counterparts of alternators, the auxiliary power modules (APM) in electric vehicles (EVs) play an irreplaceable role in bridging the high-voltage (HV) propulsion system and low-voltage (LV) auxiliary system. With the increasing demands on fast charging, the HV propulsion system is seeing an involution from 400 V system to 800 V system. To adapt to the trends, the APM also faces the challenge of accepting a wider input voltage range, particularly in EVs with a reconfigurable battery pack. This paper proposed a reconfigurable current-fed dual active bridges (CFDAB) based converter which accepts an ultra-wide-range input from 180V to 900V and an output from 6V to 16V to cover both 400 V and 800 V systems. Topology, operation principles, and simple control to minimize the switching loss are discussed in the paper. A >3 kW prototype with a peak efficiency of 97% was built and tested, which successfully validated the proposed topology and control.

Integrated chargers have gained an increasing interest in the electric vehicle (EV) industry. Existing solutions such as the integrated onboard charger (OBC) and auxiliary power module (APM) save the cost and the size, however, it only provides limited functions and hard to be integrated with the future wireless power transfer (WPT) technology. This paper proposed a multi-function magnetic coupler-based integrated charger that provides bidirectional OBC, WPT charging, and APM functions in a single system. In addition to the multi-port converter topology, a multi-winding WPT charging pad is repurposed serving as the main transformer in the OBC and APM modes as well. The paper briefs the system topology, explains various charging modes, and details the magnetic coupler design. Furthermore, a prototype was constructed and successfully delivered 6.6kW in OBC mode, 3.3kW in V2L mode, 6.6kW in WPT mode, and 800W in APM mode, which validates the proposed design.

This paper, to the best knowledge of the authors, for the first time reports the packaging of a 100kW three-level active neutral point clamped (3L-ANPC) phase leg power module for electric vehicle (EV) traction inverter applications using 650V/150A e-mode gallium nitride high-electron-mobility transistors (GaN HEMTs). Compared with two-level (2L) half bridge power module, the main challenges of packaging a 3L-ANPC phase leg power module are high number of switches (6 switches vs 2 switches) and multiple commutation loops (1 commutation loop vs 4 commutation loops). In addition, there are four switches involved in the two long commutation loops. Those parasitic loop inductances must be minimized simultaneously. Those challenges are addressed by meticulous packaging of the power module, featuring low power loop inductances, double-sided cooled power module, low junction-to-coolant thermal resistance, symmetrical layout for the two parallel dies of each switch and mechanical robustness, etc. The simulated loop inductances are 1.92nH for the short loops and 5.21nH for the long loops, respectively; resulting in a 471V and 540V of turn-off voltage spikes in a double pulse test simulation at 400V/200A. The simulated junction-to-coolant thermal resistances are 0.37°C/W and 0.53°C/W for different switches, respectively.

To build an integrated battery charger with multiple functions for electric vehicles (EVs), the system normally has several stages, such as AC/DC power factor conversion (PFC) converter, isolated and/or non-isolated DC/DC converters. Therefore, it is important to implement the start-up and shutdown procedure by coordinating multi-stage converters to avoid potential large inrush current or over voltage. This paper firstly proposed a highly integrated multi-stage battery charger for electric vehicles that offers multiple functions, including on-board charger (OBC), vehicle-to-load (V2L), wireless power transfer (WPT), all using a 400V battery, and auxiliary power module (APM) for a 12V battery. The control methods for each function are introduced. Based on the system configuration and characteristics of different functions, comprehensive system-level start-up and shut-down schemes are proposed for practical operation scenarios of OBC, WPT and V2L. Finally, a 400VAC/800VDC/22kW prototype is built and the effectiveness of the proposed start-up and shut-down schemes is verified by experiments.

The parasitic capacitance of a power module baseplate provides a path for displacement current during the switching transient of the power module, which causes extra switching loss and EMI noise. It becomes an increasing concern especially for emerging 10 kV SiC MOSFET modules due to their high voltage and fast switching speed. This paper presents an in-depth analysis of 10 kV SiC MOSFET module baseplate parasitic capacitance impact on switching loss. The turn-on switching energy is divided into four parts, and the module baseplate parasitic capacitance impact on each part of the energy is analyzed. In addition to a constant capacitive energy (i.e., $\displaystyle \frac{1}{2}$ CV2), the module baseplate parasitic capacitance also introduces extra V-I overlap energy during voltage fall stage of the turn-on switching transient because it increases voltage fall time. This portion of loss is modeled and quantified. The module baseplate parasitic capacitance impact on switching loss is experimentally evaluated at 6 kV dc voltage and 0 to 50 A currents. This 10 kV SiC MOSFET module baseplate capacitance contributed loss is in the 5-10% range.

In this paper, a 50-kW 1-kV/6.25-kV medium voltage dual-active-bridge (DAB) transformer has been designed and tested. The shell-type transformer structure with stacked small cores is selected to integrate the leakage inductance and reduce the eddy current loss. Dry-type insulation with selective shielding is adopted and both winding-to-ground and winding turn-to-turn insulation are considered. The transformer geometry-based design procedure is discussed to achieve high efficiency and power density considering the effect of eddy current loss and insulation constraint. Tests up to the full voltage and power were performed and the DAB transformer achieved 99.66% full-load efficiency and 13.5 kW/L density for the transformer.

This paper presents temperature sensitive electrical parameters (TSEPs) selection for a 10 kV silicon carbide (SiC) MOSFET power module. Static parameters including ON-state resistance and threshold voltage are introduced. A double pulse test (DPT) platform is built to test the power module on a hotplate, and the switching transient behavior in a temperature range from 25℃ to 125℃ is analyzed in detail. Various parameters during turn on and turn off are measured and compared based on their temperature linearity and sensitivity. Load current and gate resistance impacts on measurement are discussed, as well as comparisons to low voltage SiC MOSFETs.

This paper presents a low cost Si IGBT circuit breaker for protection of the Wolfspeed 10 kV XHV-9 half bridge SiC MOSFET module. Based on the 10 kV SiC module short circuit (SC) protection requirement, both current limiting and desaturation protection are needed for this IGBT breaker. Voltages balancing for series-connected IGBTs and effective current limiting of this IGBT breaker during SC transient are discussed. Detailed modes transition between the 10 kV SiC module and the IGBT breaker during SC transient is analyzed. Demonstration of the 10 kV SiC module with the IGBT breaker SC test and continuous power test at 6 kV voltage are presented.

This paper presents a half-bridge submodule design based on a 10 kV SiC MOSFET XHV-9 power module. The design of the gate driver, isolated power supply, and busbar are presented. High voltage insulation capability, fast short circuit protection, and resilience to EMI of the designed submodule are demonstrated through continuous power tests at 6.5 kV, 57 A and through a short circuit test. This submodule verification facilitates the adoption of high-voltage SiC MOSFETs in medium-voltage (MV) converters, shedding light on highly efficient power conditioning systems (PCS) for grid applications.

A hybrid microgrid is an attractive concept that aims to deliver energy to local ac and dc loads, reducing the strain imposed on the electrical grid. A hybrid microgrid of a flexible manufacturing plant consists of dc and ac loads, and distributed energy resources interfaces with the distributed grid through a power conditioning system to enable grid support capabilities and control power flow. To evaluate the controller functions of the hybrid microgrid, an appropriate testing platform is required. In this paper, the plant is emulated via a converter-based hardware testbed. The developed hardware testbed serves as a realistic model of the flexible manufacturing plant to test the controls and different scenarios to address potential issues or challenges with the control strategies and algorithms before system deployment. In addition, the hardware testbed provides the opportunity to validate the system’s response under different operating conditions in a controlled environment, leading to a more robust and reliable system design.

A solid-state circuit breaker (SSCB) needs to have very high efficiency comparable to its mechanical counterpart, and GaN offers highest conduction loss reduction at cryogenic temperatures. So, cryogenic cooling of future EAP is leveraged to design a 750V/100A SSCB module with an efficiency target higher than 99.9% and high over-current capability. The cryogenically cooled SSCB module design is developed in this paper, including key components selection and module design considerations. Experimental results are provided to validate the capability of the designed SSCB module to interrupt 10x of rated current at cryogenic temperatures (<-153°C).

Solid state circuit breaker (SSCB) with high efficiency and high gravimetric power density is required for Electrified Aircraft Propulsion (EAP). A cryogenically cooled GaN device based SSCB module is developed for EAP system. The SSCB module is suitable for medium voltage direct current (MVDC) applications and is designed with low-weight modular cold plates. Each module is rated for 750V, 100A and achieves a power density of 329 kW/kg. The design of the SSCB module structure, thermal design, and insulation design are discussed. Experimental results of interrupting an over-current fault of ~10x of the rated current by the SSCB module is provided to validate its operation at cryogenic temperature.

This paper discusses the impact of parasitic inductances on the electromagnetic interference (EMI) performance at radiated frequency and provides a new concept for high-frequency wide bandgap (WBG) power module package design with integrated $\pi$-type common mode filter ($\pi$-CMF). The connection parasitic-inductances of a $\pi$-type CMF model are analyzed, and the parasitic inductances from the CMF to the CM noise source and to the heatsink are minimized to improve the CMF's EMI performance in the radiated frequency range. Therefore, placing the $\pi$-CMF closer to the power module (i.e. in-package CMF) provides a larger noise attenuation compared to placing it outside the module (i.e. external CMF). To verify the theoretical analysis, a half-bridge GaN power module with an in-package $\pi$-CMF is designed, and experiments are conducted by comparing the attenuated noise spectrums of a 70-V/1.75-A hard-switching buck converter built by the designed module with an external CMF and the power-module integrated CMF. According to the experiment results, up to $10\ \text{dB}\mu\mathrm{V}$ more attenuation is achieved by the in-package CMF than the external CMF, validating the analytical conclusion.

In this paper, an embedded GaN half-bridge power module with double-sided cooling, low inductance, low thermal resistance, on-package decoupling capacitors, localized common mode filter, and integrated gate drivers is proposed. The two GaN dies are embedded in a printed circuit board (PCB) with heat dissipation paths to a ceramic substrate from both sides of the devices to achieve double-sided cooling capability. Thermal and electrical performance are fully analyzed and optimized. A low-cost module assembly procedure is presented utilizing standard layer attaching process. Finally, a compact $\mathbf{2.7}\ \mathbf{cm} \times \mathbf{1.8}\ \mathbf{cm}$ half-bridge GaN power module is fabricated to verify both electrical and thermal performance through experiments. The switching performance of the power module is tested under 400 V/25 A double-pulse test that shows the power loop inductance is as low as 1.03 nH and the overshoot voltage of the switching waveform is less than 5% of the dc bus voltage. The thermal resistance is verified to be 0.32 K/W, and the fabricated power module is employed in a buck converter with 500 W output power at 600 kHz switching frequency.

With the development of the modulation strategies for dual-active-bridge (DAB) converters, single-phase-shift (SPS), dual-phase-shift (DPS) and triple-phase-shift (TPS) have been proposed aiming at the realization of zero-voltage-switching (ZVS) or elimination of the reactive power at different power and voltage. While the previous work mainly focuses on the steady-state operation or the small-signal model for one specific modulation strategy, the real practice requires modulation strategies to switch among SPS, DPS and TPS frequently during the load transients, which can cause a current spike and dc-bias current in the transformer. Therefore, a smooth transition among different modulations is necessary. This paper proposes a duty-cycle compensation method to eliminate such current spike and DC bias. The implementation of the proposed method in the control loop is also discussed. Finally, the experimental results are provided to validate the performance of the duty-cycle compensation method.

Evident in previous literature, in the motor drive system, the research on the analytical models for common-mode (CM) performance evaluation is inadequate but needed. Especially for the 3-level inverter system. The majority of work focuses on simulations and experiments. In this paper, an analytical model of CM voltage (CMV) in a 3-level inverter is presented based on Double Fourier Integral (DFI). The model could be extended to different 3-level modulation schemes such as conventional space vector PWM (CSVM), nearest three space vectors modulation (NTSVM), and reduced common-mode voltage modulation (RCMVM). The impact of these three modulation schemes on the CMV is comprehensively compared across varying modulation indices. An 800V/50kW 3L inverter will be built using off-the-shelf automotive-qualified 650V/60A GaN HEMTs from GaN Systems.

This paper focuses on the design of a 650 V/150 A gallium-nitride (GaN) power module. Direct bonded copper (DBC) is applied as the insulated thermal pad to dissipate the heat generated by the GaN dies, where ceramics is employed for the thermal pad insulation. Printed circuit board (PCB) on the top of the GaN dies integrates the auxiliary power supply, the gate drive circuits and the decoupling capacitors, which can help the parasitic inductance reduction in the gate drive loop and the power loop to reduce the overshoot voltage across gate to source and drain to source. The packaged module exhibits high-current capability (150 A), high-compactness (45*33*9.6 mm³) and excellent thermal impedance from junction to heatsink. Taking advantages of the integrated gate-drive circuit, the proposed power module has simpler interface for users compared to regular GaN HEMTs on the market, which only needs PWM signal and non-isolated power supply to drive. To verify the electrical performance and thermal performance presented above, both double pulse test (DPT) and thermal test are conducted. DPT at 450 V/150 A shows around 54 V voltage spike only, which makes the proposed module suitable for high-power EV on-board charger or motor drive inverters.

On-board charger (OBC) and auxiliary power module (APM) are two major power electronic units in electric vehicles (EVs). OBC is the interface between the grid and HV propulsion battery, and the APM is the bridge connecting the HV system and LV system inside the EV. To save the cost and shirk the size, this paper proposed a three-port current-fed triple-active bridge (CFTAB) converter to integrate OBC with APM both electrically and magnetically. Compared with state-of-art integration approaches, the proposed converter features a simple structure, free of function-select switches, and fewer transformer turns. With the corresponding power decoupling method developed, the proposed topology also allows charging HV battery and LV battery simultaneously. Due to the current-fed nature, there is no need for large output capacitors, and much lower current stress is exhibited. In addition, an integrated prototype for 11kW/250V~450V OBC plus 3.5kW/10V~16V APM is developed to prove the superiorities of the proposed integrated charger.

As motor drive inverters continue to employ Silicon Carbide (SiC) and Gallium Nitride (GaN) devices for power density improvements, sensorless motor control strategies can be developed with field-programmable gate arrays (FPGA) to take advantage of high inverter switching frequencies. Through the FPGA’s parallel processing capabilities, a high control bandwidth sensorless control algorithm can be employed. Sensorless motor control offers cost reductions through the elimination of mechanical position sensors or more reliable electric drive systems by providing additional position and speed information of the electric motor. Back electromotive force (EMF) estimation or model-based methods used for motor control provide precise sensorless control at high speeds; however, they are unreliable at low speeds. High frequency injection (HFI) sensorless control demonstrates an improvement at low speeds through magnetic saliency tracking. In this work, a sinusoidal and square-wave high frequency injection sensorless control method is utilized to examine the impact an interior permanent magnet synchronous machine’s (IPMSM) fundamental frequency, injection frequency, and switching frequency have on the audible noise spectrum and electrical angle estimation. The audible noise and electrical angle estimation are evaluated at different injection voltages, injection frequencies, switching frequencies, and rotor speeds.

The increase in growth rate in the implementation of free fuel-based solar and wind energy can be seen across the globe in recent times. These systems are regulated and conditioned to work with the existing power grid. However, the 24/7 implementation of solar and wind energy systems is still questionable. Numerous research efforts are being conducted to penetrate these sources into the current power grid with maximum efficiency. Even with all the effort, the basic Alternating Current (AC) to Direct Current (DC) losses can only be minimized to a certain extent which is physically permissible. This paper emphasizes the importance of DC architecture in solar and wind energy implementation. It also focusses on providing an alternative point of view for a DC-based power network that has Photovoltaics (PV) and Lithium-ion Battery systems at its center along with Wind energy systems to supplement it. The two viewpoints of conversion loss minimization in working with the current AC infrastructure and complete end-to-end DC power network for niche applications like desalination, cement manufacturing, steel manufacturing, mining operations, etc. are discussed. The viability and cost-effectiveness of such an improved power network is emphasized.

Dual-active-bridge (DAB) circuit is an excellent candidate for a high-efficiency, high-power-density and bidirectional electric vehicle charger. Unlike other circuits employing resonant inductors and capacitors, DAB minimizes the usage of passive components. The challenge, however, lies in difficulty of securing zero voltage switching (ZVS) at light-to-medium load. This is utmost important not only to the efficiency but also eliminating the bridge-switch crosstalk during the hard switching-on thereby enhancing the system reliability. Systematically integrating SPS, dual-phase-shift (DPS) and triple-phase-shift (TPS) to secure full-load-range ZVS in EV chargers has not been seen and is the focus of this paper. This paper plots the ZVS boundary for the full-load range, categorizes all operations into eight modes and proposes a smooth transition among SPS, DPS and TPS for a 20kW EV battery charger. Experimental results on a SiC-based charger validated its effectiveness and the smooth transition for the output voltage of 200~450VDC and 0~20kW.

The past literature, when investigating the common-mode current vs. switching frequency and switching profile, usually evaluated through simulation and experiment while lacking analytical models and tools. Some PWM methods might reduce the common-mode voltage (CMV) at some frequency, however, cause the increasing at other frequency points. Such overall merits and performance between different PWM patterns can only be evaluated by analytical models. In this paper, the analytical model of various PWM schemes with respect to common-mode (CM) signals are derived by Double Fourier Integral (DFI) analysis, especially for the active-zero state PWM (AZSPWM), which was simulated in the past while without any analytical model being presented. Both mathematical analysis and experimental results showed that AZSPWM does not necessarily reduce CMV in an overall frequency spam due to the induced sideband harmonics when comparing to some other modulation schems, for example, the discountinuous PWM (DPWM). The analytical tool can help provide a guidance on choosing different modulation method to achieve a practical and efficient combination based on various scenarios in motor drive applications.

Auxiliary Power Module (APM) bridges the high voltage battery with the low voltage auxiliary battery in Electrical Vehicles (EV). This paper designed such APM for EV rated at 3.5kW with a peak power of >6kW, covering 250-400V input and 10-16V output. One key dynamic process lies in the pre-charge mode, i.e., charging the DC bus capacitor before the full operation. Another challenge lies in the DC bias current for the bridge based circuit. A novel and simply DC bias detection circuit is proposed to sense the unbalanced current in the transformer. Both simulation and test results verified that the proposed method can effectively detect and eliminate the DC bias in the transformer.

A 250V~450V/10~16V auxiliary power module (APM) is needed for electric vehicles to power the 12V load, such as on-board PbA battery, GPS and steering motor. With the era of connected and autonomous vehicles starting, the load of the 12V system is even higher given numbers of sensors and radars being equipped. In some cases, the 12V system needs to be able to provide 6kW instantaneous power, yielding >500A output current. This paper compared two design candidates, i.e., single-stage LLC design with a two-stage interleaved Buck + DCX design, aiming at 3.5kW rated power and 6kW peak power. Simulation results show the two-stage design is a more qualified candidate for this highpower application. Then a two-stage prototype was built and tested. Experimental results show ~96% efficiency with a power density of >2kW/L, thanks to the excellent switching performance of SiC MOSFETs and low switching stress by DCX.

Dual-Active-Bridge is good candidate in electric vehicle charger, owing to bidirectional power flow and excellent galvanic. To optimize efficiency of DAB converter, many modulation strategies are proposed, including single-phase-shift, dual-phase-shift, and triple-phase-shift. The different modulation strategies can focus on realization of Zero-Voltage-Switching, minimization of reactive power and suppression of current stress, which are all improvement of steady sate performance. When utilizing multiphase-shift modulation, the dynamic response is also important in real application. In this paper, the averaged small signal models of different modulations are proposed. The different magnitude and phase performance are also discussed. An example of PI controller is proposed when using multi-phase-shift. To verify the proposed calculation and design, a Simulink model is developed, which also consider the influence of digital control in MCU.

As the effort to maximize the potential of SiC devices, the Field Programmable Gate Array (FPGA) is utilized in this paper to achieve high control bandwidth (>200 kHz) when implementing the Field-oriented Control (FOC) algorithm. This can greatly enhance the high-frequency injection (HFI) sensorless control for Permanent Magnet Synchronous Motors (PMSMs) by widening the applicable speed range, for instance, increasing the injection frequency up to 2 kHz from the conventional 500Hz. To offset the cost, it is also validated that one FPGA can control two motors simultaneously.

With the development of power electronics, three-phase voltage source inverters(VSls) are widely used in industry application. In this paper a SiC device based EV battery charger consisting of dual active bridge(DAB) and three-phase four-wire VSI is built. In order to undertake the unbalanced load, an independently controlled neutral module(ICNM) has been adopted for the VSI control to form the neutral line and provide the path for the zero-sequence current. Split DC-bus capacitors with the fourth leg are equipped to the conventional VSI. Meanwhile, the control performance is improved by paralleling virtual resistors to the load, namely, notch-filter-incorporated capacitor voltage feedback control(NF-CVFC), which not only enhances the quality of the output voltage but also ensures the system stability. Finally, a 10kW prototype is built and tested. Experimental results verified the proposed control strategy and the practical feasibility.

Wide-Bandgap devices are believed to be promising candidates for the next-generation power electronics converter. However, the prohibitive cost and limited variety are still the main constrains before being widely used. One possible solution to mitigate these issues is hybrid switches, a combination of Si MOSFETs and WBG devices. To maximize merits of both GaN HEMT and Si MOSFET, this paper proposes a hybrid switch consisting of two GaN HEMTs and two Si MOSFETs. For such a design, a robust gate-drive loop is critical to secure the safe operation of all switches. As an instructive work, this paper presents a comprehensive analysis of the switching transient process and its impact on the gate-drive loop, practical tuning tips of gate-drive loop design are also given based on the simulation and experimental results. A 400V/ 80A full bridge prototype is developed to validate our design. Experimental result shows that, with enhanced gate-drive loop, we can continuously turn off 400V/80A@100kHz and 400V/40A@300kHz with only one GaN device paralleled to two commercial Si MOSFETs.

In order to reduce the resources utilization of Field Programmable Gate Array (FPGA) chip thereby using one FPGA to control multiple motors together, a novel time-division multiplexing (TDM) method is proposed in this paper. The field-oriented control (FOC) algorithm is developed using Xilinx system generator (XSG) in Matlab/Simulink environment. Due to the fast calculation speed of FPGA and the pipeline optimization technology, the execution time of FOC algorithm can reach <;2.5 μs and the switching frequency can be increased to >100 kHz. In order to verify the proposed TDM method, the dual-motor scenario is studied in this paper. Experimental results show that by adopting the proposed TDM method, the resource utilization of the FPGA chip can be further greatly reduced.

As two exemplary candidates of wide-bandgap devices, SiC MOSFETs and GaN HEMTs are regarded as successors of Si devices in medium-to-high-voltage (>1200V) and low-voltage (<;650V) domains, respectively, thanks to their excellent switching performance and thermal capability. With 650V SiC MOSFETs coming into being the direct competition of SiC and GaN in <;650V domains is inevitable, such as Level-2 battery chargers for electric vehicles. This paper applies 650V SiC and GaN to two 240VAC/7.2kW EV battery chargers, respectively, aiming to provide a head-to-head comparison of these two devices in terms of the efficiency, power density, thermal and cost, with the same control strategy of varying the phase-shift and switching frequency to cover the wide input range (80VAC~260VAC) and wide output range (200V~450VDC).

Wide-bandgap (WBG) devices are believed as the alternate of silicon switches for high-efficiency and high-power-density power electronics converters. While two major challenges of WBG devices remain as high cost (~5 times of Si) and less options (the maximum power rating for GaN is only 650V/60A), paralleling GaN with Si could be the potential solution to solve pains above. In this paper, two SMT GaN HEMTs are paralleled to a TO-247 Si MOSFET. A time delay is added between switch gate signals to make GaN endure the switching loss and Si conduct majority of the current, which maximizes advantages of both switches. The proposed design is found particularly useful for zero-voltage-switching applications. Critical dynamic behaviors such as the current overshoot to the GaN, current distribution during the dead time, and voltage spike during the turn-off caused by parasitics are comprehensively discussed. Its impact on the control performance and system loss is evaluated as well.

To filter the 120Hz output current ripple in our previously designed 7.2kW single-phase EV charger, this paper proposes to equip the charger with a buck-type active filter. 650V/60A enhancement mode GaN HEMTs provided by GaN Systems Inc are adopted to work at hard-switching mode. Experimental results indicated that four such switches could be paralleled to hard switch on/off ~240A, which is the key for the buck-type active filter. A model-based proportional-resonant controller is adopted to smooth the output current. Such control will enhance the dynamic response of the active filter, compared to the conventional PI controller. The experimental output current ripple and power loss analysis are given.

Present electric vehicles usually use 3.3kW or 6.6kW chargers. With three-phase 380VAC~480VAC available, it is possible for the charger to deliver much higher power, e.g., 20kW, which will expedite the battery charging speed. Meanwhile, wide-bandgap devices (WBG) like silicon carbide MOSFETs and gallium nitride HEMTs provide higher efficiency than Si devices, which potentially will increase the power density thereby fitting such a fast charger on board. This paper uses the conventional LLC topology to realize a 20kW all-SiC EV onboard charger. Two half-bridge LLC converters are series connected on the primary side and parallel connected on the secondary side to provide 20kW together. Matrix transformers are utilized to facilitate the system assembly. Experimental results validated that such design approach could realize 20kW and reach ~96% wall-to-battery efficiency.

It is expected that wide-bandgap devices like silicon carbide MOSFETs and gallium nitride HEMTs could replace Si devices in power electronics converters to reach higher system efficiency, e.g., a 3-phase 380VAC bidirectional battery charger for electric vehicles. This paper uses the conventional half-bridge LLC topology to build a 10kW all-SiC bidirectional charger. As a well-known topology for the unidirectional charger, it has not been comprehensively explored for the usage of the bidirectional energy flow, which falls into the scope of this paper. A double-pulse-test platform is utilized to provide the accurate power losses, which, combined with the state-space model deriving the accurate switching current waveforms eventually accurately, estimates the system efficiency. Based on this model, to further enhance the system efficiency the DC-bus voltage is varied while keeping the LLC DC/DC converter running at the resonant frequency through the whole power range. Experimental results validated our proposed approach that such topology could realize the bidirectional power flow with zero-voltage-switching turn on. With varying the DC-bus voltage, the V2G and G2V modes reach ~96% wall-to-battery efficiency.

At present time, the most common electrical vehicle (EV) chargers employ a two-stage design, i.e., a front-end AC/DC stage + an isolated DC/DC converter. In this paper, an isolated dual-active-bridge (DAB) based single-stage AC/DC converter was proposed, which has the power-factor-correction (PFC) and zero-voltage-switching (ZVS) functions over the full-load range. By reducing one power stage and eliminating the large DC link capacitor, a high efficiency and high power density are achieved. Such topology can be used as a modular building block to scale up to 50kW by serial connecting the input terminals and paralleling output terminals. A novel energy-balanced variable switching frequency control for such input-series-output-parallel (ISPO) modular designed is proposed. A single-phase d-q transformation is implemented to achieve zero steady-state error. Simulation analysis and experimental validation are presented.

Full-bridge power-factor-correction (PFC) front-end + dual-active-bridge (DAB) AC/DC topology is widely used in industry, e.g., electrical vehicle on-board charger. Such two-stage topology limits the system efficiency, and the bulky DC link bus capacitor makes the system power density relatively low. Compared to the two-stage design, the single-stage design, unfolding bridge + DAB, eliminates the bulky DC link bus capacitor and operates the front-end with only 60Hz switching frequency, thereby has the potential to increase the system power density and efficiency. A novel variable-switching-frequency and hybrid single-dual-phase-shift (VSF-SDPS) control strategy is proposed and analyzed for the DAB based single-stage topology. The proposed VSF-SDPF control consists of two phase shifts to guarantee Zero-Voltage-Switching (ZVS) over the full range of the AC line voltage, and frequency modulation to achieve boost PFC. The conventional front-end PFC is simplified to an unfolding bridge by changing DAB control strategy to achieve PFC and ZVS at the same time. Besides, a special ZVS boundary is utilized to solve the grid current distortion problem when the switching frequency saturated, which is especially severe at light load condition. Simulation results and experimental validation are presented under 50Vrms AC line voltage and 200V DC battery voltage test condition.

In this paper, wireless power transfer for mobile phones via coupled magnetic resonance with multiple transmitters (Txs) and / or receivers (Rxs) are investigated and tested. The system is able to charge cellphones with more than 3 W in a distance between 5 and 15 cm and also in different angles. The resonant frequency is 6MHz. For lower charging powers the distance between the Tx and Rx can go up to 20 cm. Additionally, the three-dimensional movement of the Rx and its effect to the charging power is tested, as self-rotation and rotation around the Tx coil. This achievement is significant to improve user experience of wireless charging for portable electronic devices.

This paper designed the gate driver circuits and optimized the PCB layout in a 7.2kW battery charger using paralleled GaN HEMTs. 650V/60A enhancement mode GaN HEMTs provided by GaN Systems Inc are adopted. To optimize the switching performance of paralleled GaN HEMTs with low loss and high reliability, effects of parasitic inductance and capacitance are modeled and analyzed. Through cancelling the flux in the commutation loop, the power-loop parasitic inductance is reduced to only 0.7nH, which significantly decreases the electrical stress in the switch turn-off process. A diverse-parameter gate driver design has been proposed to achieve the reliable switching off. The Finite-Element-Analysis and Spice simulation show our current design could effectively suppress the voltage overshoot and gate-drive ringing on HEMTs. Experiments were carried out on both double pulse test platform and the 7.2kW charger to verify the proposed design strategy.

In this paper, a soft switching DC-DC converter control strategy based on fixed boundary layer sliding mode control (FBLSMC) and switching frequency modulation is presented with application to an electric vehicle (EV) powered by a hybrid energy storage system (HESS). This strategy is aimed at improvement of transient performance, energy transfer efficiency and system robustness for the HESS By fully taking into account all PWM operating modes and the occurrence of system uncertainties, the state-space model of the studied DC-DC converter is newly established. The chattering-free FBLSMC scheme for current/voltage tracking is proposed to guarantee the systematic robustness. Meanwhile, in order to ensure soft switching operating effectiveness and accordingly high efficiency, an adaptive switching frequency modulation method is presented complying with the state equations and proposed principles. Finally, experimental results considering the transient response and driving cycle operation confirm the validity and application feasibility of the proposed strategy in the HESS powered electric vehicle.

In this paper, a novel topology of a non-isolated buck converter with zero-current-transition (ZCT) capabilities is presented. In order to realize ZCT condition, the auxiliary circuit consists of a coupled inductor, a capacitor and an auxiliary switch, which also operates with a ZCT condition. It should be noted that the coupled inductor is comprised of three inductors on the same ferrite core which plays an important role in different branches. Moreover, the coupled inductor plays an effective role in achieving soft-switching condition. The detailed operating analysis of the proposed converter is presented. Finally, a 720 W prototype is built to verify the theoretical principles. The switching waveforms are also measured to validate the proposed topology.

Full-bridge power-factor-correction (PFC) front-end + dual-active-bridge (DAB) AC/DC topology is widely used and its small-signal model has been studied in depth. Compared to the two-stage design, the single-stage design, unfolding bridge + DAB, is attracting more attention nowadays. By eliminating the bulky DC link bus capacitor and operating the front-end with only 60Hz switching frequency, the DAB based single-stage AC/DC converter has the potential to increase the system power density and efficiency. Different from the conventional constant-switching-frequency (CSF) DAB control, a novel variable-switching-frequency (VSF) DAB control is more suitable for the single-stage design due to the 0 to peak input voltage. A full-order state-space model is proposed in this paper to describing the VSF control. The influence of DC blocking capacitor is stressed because there is always a low frequency excitation of VSF control which is not existed with CSF control. The resonance of DC blocking capacitor and transformer leakage inductor is well described by the full-order state-space model. Simulation and experimental results verified the correctness of proposed DAB full-order state-space model.

Most of the present EV on-board chargers utilize a three-stage design, e.g., AC/DC rectifier, DC to high-frequency AC inverter, and AC to DC rectifier, which limits the wall-to-battery efficiency to ~94%. Instead of using the regular three-stage design, a matrix converter could directly convert grid AC to high-frequency AC thereby saves one stage and potentially increases the system efficiency, however, the control will be more complex and the high cost of building the back-to-back switches is inevitable. This paper adopts the 650V E-mode GaN HEMTs to build a level-2 on-board charger. The input voltage is 80~260VAC, the battery voltage is 200~500VDC and the rated power is 7.2kW with the bidirectional power-flow capability. Such design saves the bulky DC-bus capacitor. Variable switching frequency is combined with phase-shift control to realize the zero-voltage switching. An active filter is employed to choke the 120Hz output current ripple if needed. To further increase the system efficiency, four GaN HEMTs are paralleled to form one switching module. The overall system efficiency is >97% and the power density is 2.5kW/L with the active filter and 3.3kW/L without the active filter.

Instead of using 1200V SiC MOSFETs for the >600V applications, this paper utilized 650V E-mode GaN HEMTs to build a three-level DC/DC converter. The DC-bus voltage is 800V, the output voltage of 380V and the power is 2.5kW with the bidirectional power-flow capability. Simulation and experimental results show that such design strategy is superior to a single 1200V SiC MOSFET based DC/DC converter in terms of the switching and conduction performance. On the other hand, in order to better understand the performance of GaN HEMTs, hard-switching technology is used to fully test the switching behaviors. Two GaN HEMTs are in parallel to enhance the power capability, which requires the special focus on the parasitic parameters. The effects of parasitics especially the stray inductance in the commutation loop and the gate-drive loop during switching transitions have been comprehensively analyzed and discussed in this paper.

This paper presents a novel axial-flux microelectromechanical systems (MEMS) based micromotor with dual-rotor and 10mm diameter. The characteristics of MEMS micromotor are analyzed and modeled using a 3-D magnetic equivalent circuit (MEC) taking the leakage fluxes and fringing effect into account. Such methodology yields more accurate prediction of the flux distribution inside the machine, back electromotive force (EMF) waveform and the torque. The key point of the analytical model is to compute the magnetic flux density in the air gap generated by the permanent magnet. An accurate prediction method of the leakage fluxes based on an improved pigeon-inspired optimization (PIO) algorithm is proposed in this paper. The feasibility of the proposed method is validated by the 3-D finite element analysis (FEA). Finally, the method is applied to design and manufacture the micromotor.

In previous work, a novel design of a 2.5kW 400V-12V 93.2%-efficiency DC/DC converter with a triggering angle tracking synchronous rectifier was proposed for use in an electric vehicle to replace the electric alternator. This paper is focused on the further enhancement of the DC/DC converter to improve the system efficiency and wide-range input/output performance.

The Gallium nitride high electron mobility transistor (GaN HEMT) has become popular in the power electronics industry as it offers the possibility to reach lower switching loss and higher switching frequency compared to Si devices. This paper adopts a normally-off GaN HEMT in the wireless power transfer (WPT) system to charge a 48V battery pack on the E scooter. 178W power was delivered to the battery pack with 813 kHz switching. A simulation model of GaN HEMT is also built in LTspice to itemize the system loss. At the end some thoughts of improving the system efficiency were proposed.

Variable switching frequency PWM (VSFPWM) control has been adopted in the induction motor drive in recent work. Due to the position-related phase inductance, interior permanent magnet synchronous motors (IPMSM) have the difficulty to adopt VSFPWM. In contrast to using thevenin theory from previous work, this paper applies d-q transformation to IPMSM drives to predict the phase-current ripple and applies VSFPWM to control the current ripple of IPMSM. Simulation results validated the effectiveness of the theoretical analysis.

This paper adopted the variable switching frequency PWM (VSFPWM) control to the SPMSM and combined the VSFPWM with SVPWM and DPWM. A power loss model was built to quantitatively compare the system efficiency at CSF/VSF SVPWM and CSF/VSF DPWM. Simulation and experimental validations were pursued on a 5kW surfaced-mounted permanent synchronous motor (SPMSM) drive system.

This paper presents a method for the sensorless control in full speed range for an interior permanent-magnet synchronous motor (IPM). At standstill and very low speed region, high frequency (HF) injection technique is used to detect the rotor initial position. A hybrid observer is applied to realize a smooth transition from low to high speed. When the rotor speed goes up to a certain value where back EMF can provide adequate information, a back EMF observer will dominate. The hybrid observer is verified through simulation and experimental results using a three-phase 1-kW IPM motor drive.

This study proposes a design and development of Series-Series Compensated topology based (SSC) wireless power transfer system to charge the battery in light-duty electrified automobiles, e.g., electric scooters. An asymmetric resonant methodology is adopted by adjusting the secondary-side resonant capacitance to make the system resonate only at the secondary side, which is different from the prevalent symmetric resonant topology. The experimental data at 250W test matches the simulation result well, which improves the system efficiency.

This paper proposed a battery state of charge (SOC) estimation methodology utilizing the Extended Kalman Filter. First, Extended Kalman Filter for Li-ion battery SOC was mathematically designed. Next, simulation models were developed in MATLAB/Simulink, which indicated that the battery SOC estimation with Extended Kalman filter is much more accurate than that from Coulomb Counting method. This is coincident with the mathematical analysis. At the end, a test bench with Lithium-Ion batteries was set up to experimentally verify the theoretical analysis and simulation. Experimental results showed that the average SOC estimation error using Extended Kalman Filter is <;1%.

This paper proposes a design and development of a wireless power transfer system to charge the battery in the Plugin Hybrid Electric Vehicles. A Parallel-Parallel topology is adopted to realize 15 cm-distance power transfer using resonance theory. Finite Element Method is used to extract the coil parameters. The advantages of the proposed design compared to the previous similar research are 1) low operational frequency (42 kHz) to avoid the electromagnetic interference to on-board automotive electronics equipment, and 2) low electrical stress to the semiconductor switches through using zero-voltage-switching technique. A 2 kW prototype to charge 200 V battery was built to experimentally verify the theoretical analysis. The overall system efficiency is ~86%.

This paper proposes the design and development of a 2.5kW 400V→12V high-efficiency DC/DC converter with a wide input voltage range (450V~220VDC) and output voltage range (16V~6VDC). The designed DC/DC converter will be used in the electric vehicle as an electric alternator. An LLC half bridge topology is adopted as the primary side of the isolated DC/DC converter. For the secondary side, a novel rectification control strategy is developed to turn on/off the rectifier MOSFETs by actively tracking the exact triggering moments. A 2.5kW prototype to charge the on-board 12V battery was built to experimentally verify the theoretical analysis. The overall system efficiency was ~92% and the maximum is 93.2%.

For the conventional vehicle, an efficient and effective heat source that provides autonomous exhaust temperature control is of interest, and one solution is a diesel burner which needs to adjust its air delivery based on transient operating conditions through a three-phase motor drive system powered by a 12V lead-acid battery. The system proposed in this paper consists of a series-resonant LLC MOSFET full-bridge converter, which provides high-efficiency energy transfer through implementing Zero Voltage Switching, and an IGBT inverter which provides the high-side phase currents to a 1kW brushless DC motor. Experimental results on this prototype system demonstrate the LLC DC/DC part efficiency is 97.6% and the inverter efficiency is 92%.

Usually a high-efficiency Level 1~2 battery charger consists of an AC/DC (PFC) part and a DC/DC part, which in this paper is a CoolMOS based 97%-efficiency full-bridge LLC resonant DC/DC converter. Due to the existence of the output capacitance and high input voltage (usually 400VDC), the inrush current of the DC/DC converter in the starting process is inevitable, which requires an effective soft starting strategy. This paper proposed an effective soft starting strategy to gradually charge the output capacitor, decrease the inrush current and, more importantly, avoid the hard switching in the starting process, which is a must to the CoolMOS. The proposed starting strategy has been experimentally validated on a 10kW LLC resonant DC/DC converter.

Various charging algorithms are employed in commercialized battery chargers. This study was to undergo charging tests of four various chargers dedicated to 12-V lead-acid batteries. Our previous work on the Extended Kalman Filter based State-of-charge estimation in this comparison to make sure all batteries were charged/discharged to the same level. State-of-Health (SOH) is employed to determine the battery performance. The impact of the charging algorithms on the battery life time was evaluated. Experimental results show that the medium-speed charging when SOC is low with pulse charging at the high SOC keeps the longest life time of the battery.

Battery chargers of Plug-in Hybrid Electric Vehicles require high efficiency operation. An LLC resonant DC/DC converter is an excellent choice to reach the high efficiency with reduced current stress. In this paper, a CoolMOS based 10kW full-bridge LLC resonant DC/DC converter with >;97% efficiency is designed. CoolMOS model is utilized to analyze the system loss. Experimental results validate that this charger could charge the load at ~97% efficiency @10kW with output voltage varying from 250V to 400V. When output voltage is between 400V and 450V, the experimental efficiency remains above 95%.

Power factor correction controllers are widely used in the battery chargers of Plug-in Hybrid Electric Vehicle, connecting the grid with charging system to reach power factor equal to 1. Increasing the operational efficiency of the PFC is the inward search. This paper presents a three-phase full-bridge PFC circuit with >;97% efficiency at 10kW. Comparison of different control algorithms with corresponding power loss calculations is pursued to optimize the system design. Experiments on two 208VAC/10kW PFC prototypes equipped with either fast reverse recovery diode or Silicon Carbide Schottky Diode respectively validated the effectiveness of the design.

The battery is one of the most important energy storage components in EV/HEV. Failing to estimate the state of the charge accurately will bring the risk of overcharge or over discharge. The traditional Coulomb counting method will bring accumulated error over time, therefore high deviation occurs between the estimated and real state of charge. Different estimation strategies are compared in this paper, i.e., Coulomb counting method, open-circuit-voltage method and Kalman filter based state of charge estimation. Experimental results validate the effectiveness of Kalman filter during the on-line application.

Battery is a commonly used energy storage component of the ESS (energy storage system) widely applied in the development of the PHEVs (plug-in hybrid electric vehicles). With the different system configurations and parameters selection, battery will undertake the different electrical stress, e.g., loss and current ripple which are believed to pose the discount of its longevity. This paper addresses the electrical impact and power capability of the battery pack under different system configurations. Influence of the internal impedance of the battery and capacitor will be emphasized. Simulation and experiments validated that, the topology of boost converter followed by a three-phase inverter has the advantages compared to the traditional stand-alone inverter-fed motor drive system in suppressing the high-order current harmonics and elevating the power capability.

This paper extended the research on the system-level safe operation area (SSOA) of power electronic converters in our previous literatures, which proposed a comprehensive procedure of constructing SSOA, investigated the impact of the microscopic transient processes and macroscopic control algorithms, and pictured the SSOA of a battery charger for plug-in hybrid electric vehicles. The genetic algorithm is used to optimize the system parameters at the macroscopic level. More importantly, thermal characteristics of the MOSFETs and battery impedance are enclosed to enhance the system reliability and maximize the power capability. In the end, the SSOA for a SiC JFET based electric charger is also discussed.

The bidirectional DC-DC converter in a HEV is also some times called a power management converter, or an energy management converter, or boost DC-DC converter. This DC-DC converter is a high-power converter that links the high voltage battery (HV) at a lower voltage with the high voltage DC bus. The typical voltage of a battery pack is designed at 300 to 400V. The best operating voltage for a motor and inverter is around 600V. Therefore, this converter can be used to match the voltages of the battery system and the motor system. Other functions of this DC-DC converter include optimizing the operation of the powertrain system, reducing ripple current in the battery, and maintaining DC link voltage, hence, high power operation of the powertrain.

This paper presents an averaged model and a small-signal model of a bidirectional dual active bridge (DAB) DC-DC converter. Based on the proposed model, the stability and transient power flow in the system can be analyzed. A novel hybrid controller is proposed for the phase-shift based feed-back and feed-forward control of a 600V/10kW prototype. The hybrid controller can ease the difficulties of the parameter selection of a traditional PI. The effectiveness of the models and proposed hybrid controller are validated by simulations and experiments in both transient and steady state operations.

The integrated gate commutated thyristors (IGCTs) are commonly used for construction of high voltage three-level PWM controlled voltage source converter/inverters. When the output voltage is greater than the maximum rated voltage, IGCTs are connected in series. To ensure the safe and reliable operation of the converter/inverters, special measures are required to equalize the voltages across the IGCTs connected in series. An effective method for balancing voltages is to use resistors for static voltage balancing and RC snubber circuits for dynamic voltage balancing. However, most of the previous research work reported in the literature focused on the dynamic circuit design for converters of the BUCK topology. Trade off is made only between the performance of dynamic voltage balancing and the turn-on loss without any consideration of di/dt endurance and any procedural steps, which makes the design procedure not suitable for converters of the three-level topology. Based on a functional model of IGCTs, this paper presents a procedure for optimum design of the dynamic voltage balancing circuit for a 6 kV/1250 kW inverter. The specific transient processes in the three-level topology with dynamic snubber circuit are simulated and the mechanisms are analyzed, which is absent in the previous work.

The voltage increment in MV-ASD systems deteriorates the electromagnetic environment, therefore the communication system is facing a formidable challenge in the attempt to achieve the numerous real-time interactivities among those subsystems under such electromagnetic circumstance. This paper focuses on the real-time communication system for the MV-ASD systems, in which electromagnetic compatibility (EMC), real-time performance and system reliability are considered simultaneously. A novel fiber-CAN network is designed and implemented, which remarkably increases EMC compared to the conventional ones. The CAN system that serves in the multiprocessor control system for the MV-ASD system with the rated power of 1 MW is implemented. From the experiment results in the MV-ASD system with a 690 kW motor, it can be verified that the requests of timing performance and the reliability for the communication system are well accomplished

In a variable frequency and adjusting speed system with high power, the balance of neutral point is very important. This paper brings out a set of complete neutral point control strategies based on the improved space vector pulse width modulation (SVPWM) control strategy, and has obtained comparative perfect effects in practice.