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Burak Ozpineci

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Office:
E-mail:
vog.lnro@karub
Phone: 865-946-1329
Fax: 865-946-1262
Address: Oak Ridge National Laboratory
PO Box 2008 MS6472
Oak Ridge, TN 37831-6472


Biography

Dr. Burak Ozpineci is the group leader of the of the Power Electronics and Electric Machinery Research Group at the Oak Ridge National Laboratory. He received a M.S. and Ph.D. from The University of Tennessee in electrical engineering in 1998 and 2002, respectively, and his B.S. degree from the Orta Dogu Technical University, Ankara, Turkey. He joined the Post-Masters Program with the Power Electronics and Electric Machinery Research Group at the Oak Ridge National Laboratory in 2001 and became a full time staff member at the PEEMRG in 2002. Dr. Ozpineci is the Chair of the IEEE PELS Rectifiers and Inverters Technical Committee and was Transactions Review Chairman of the IEEE Industry Applications Society Industrial Power Converter Committee, and He also has a Joint Faculty Associate Professor position with The University of Tennessee. His research interests include system-level impact of SiC power devices, multilevel inverters, power converters for distributed energy resources and hybrid electric vehicles, and intelligent control applications for power converters.

Publications

Last updated May 19, 2020.

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Journal Papers
Title
Year
  • 2020

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    In this study, a method for impedance characterisation of DC-link capacitors based on transient pulse analysis is proposed. The fundamentals of the concept are presented and design considerations are discussed. The functionality of the proposed approach is supported by SPICE simulation with two different commercial capacitors from different manufacturers and validated with experimental results. Experimental results for equivalent series resistance, equivalent series inductance (ESL) and capacitance estimation are presented for commercial DC-link capacitors and compared with component analyser results. The simulation and experimental results show that the proposed method is a promising candidate for capacitance and ESL estimation of capacitors in EV traction systems.

  • Emre Gurpinar; Shajjad Chowdhury; Burak Ozpineci; Wei Fan
    IEEE Transactions on Power Electronics
    2020

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    Emerging wide–bandgap (WBG) semiconductor devices like silicon carbide (SiC) metal–oxide semiconductor fieldeffect transistors (MOSFETs) and gallium nitride (GaN) high electron mobility transistors (HEMTs) can handle high power in reduced semiconductor areas better than conventional Sibased devices due to superior material properties. With increased power loss density in a WBG–based converter and reduced die size in power modules, thermal management of power devices must be optimized for high performance in SiC MOSFET and GaN HEMT based power modules. This paper presents a graphite-embedded insulated metal substrate designed for WBG power modules. Theoretical thermal performance analysis of graphite-embedded metal cores is presented, with design details for IMS with embedded graphite to replace direct-bonded copper substrate. The proposed IMS is compared with an aluminum nitride-based direct-bonded copper substrate using finite-element thermal analysis for steady-state and transient thermal performance. The solutions' thermal performances are compared under different coolant temperature and thermal loading conditions, and the proposed substrate's electrical performance is validated with static and dynamic characterization. Using graphite-embedded substrates, junction-to-case thermal resistance of SiC MOSFETs can be reduced up to 17%, and device current density can be increased 10%, regardless of the thermal management strategy used to cool the substrate. Reduced transient thermal impedance of up to 40% of dies due to increased heat capacity is validated in transient thermal simulations and experiments. The half-bridge power module's electrical performance is evaluated for on-state resistance, switching performance, and switching loss at three junction temperature conditions. The proposed substrate solution has minimal impact on conduction and switching performance of SiC MOSFETs. This paper is accompanied by three video files demonstrating temperature across DBC and IMSwTPG substrates during cool down period.

  • Zhiqiang Wang; Madhu Chinthavali; Steven L. Campbell; Tong Wu; Burak Ozpineci
    IEEE Transactions on Industry Applications
    2019

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    This article presents a systematic power stage design approach for a high-power density air-cooled inverter, which involves the utilization of emerging 1.7 kV silicon carbide (SiC) mosfet bare die engineering samples, heatsinks optimized with genetic algorithm, and built using three-dimensional printing technology and integrated power modules with a novel packaging structure. The developed air-cooled inverter assembly is mainly composed of the SiC mosfet phase leg modules with split high-side and low-side switch submodules, which are attached to two separate heatsinks for increased heat dissipation area and reduced thermal resistance. The heatsink is designed using a co-simulation environment with finite element analysis in COMSOL and genetic algorithm in MATLAB. The primary design procedure, including bare die device characterization, loss calculation, thermal evaluation, and power module development, is elaborated. The proposed design approach is verified and validated through experiments at each stage of development. The experimental results show that the inverter California Energy Commission efficiency is 98.4%, and a power density of 75 W/in3 is achieved with a sufficient junction temperature margin for semiconductor long-term reliability.

  • Tong Wu; Zhiqiang Wang; Burak Ozpineci; Madhu Chinthavali; Steven Campbell
    IEEE Transactions on Power Electronics
    2019

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    Heatsink design is critical for power density and reliability enhancement of power semiconductor modules. In this letter, an automated design and optimization methodology for air-cooled heatsinks are proposed based on genetic algorithm and finite element analysis. While the genetic algorithm generates a population of candidates with complex heatsink cross-section geometry in each iteration, finite element analysis is used to evaluate the fitness function of individual heatsink, i.e., junction temperature of semiconductor devices. With the rule of “survival of the fittest,” the proposed methodology eventually converges to an optimum heatsink design with the lowest device junction temperature. The optimized heatsink is fabricated through three-dimensional printing technology for thermal performance evaluation. Simulation and experimental evaluations have been conducted based on a 50-kW three-phase air-cooled inverter with the fabricated heatsinks. The comparative evaluation results show that the optimized heatsink is superior over a customized solution by 27% less in size and 6% lower in junction temperature.

  • Xu She; Alex Q. Huang; Óscar Lucía; Burak Ozpineci
    IEEE Transactions on Industrial Electronics
    2017

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    Silicon carbide (SiC) power devices have been investigated extensively in the past two decades, and there are many devices commercially available now. Owing to the intrinsic material advantages of SiC over silicon (Si), SiC power devices can operate at higher voltage, higher switching frequency, and higher temperature. This paper reviews the technology progress of SiC power devices and their emerging applications. The design challenges and future trends are summarized at the end of the paper.

  • Bailu Xiao; Lijun Hang; Jun Mei; Cameron Riley; Leon M. Tolbert; Burak Ozpineci
    IEEE Transactions on Industry Applications
    2015

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    This paper presents a modular cascaded H-bridge multilevel photovoltaic (PV) inverter for single- or three-phase grid-connected applications. The modular cascaded multilevel topology helps to improve the efficiency and flexibility of PV systems. To realize better utilization of PV modules and maximize the solar energy extraction, a distributed maximum power point tracking control scheme is applied to both single- and three-phase multilevel inverters, which allows independent control of each dc-link voltage. For three-phase grid-connected applications, PV mismatches may introduce unbalanced supplied power, leading to unbalanced grid current. To solve this issue, a control scheme with modulation compensation is also proposed. An experimental three-phase seven-level cascaded H-bridge inverter has been built utilizing nine H-bridge modules (three modules per phase). Each H-bridge module is connected to a 185-W solar panel. Simulation and experimental results are presented to verify the feasibility of the proposed approach.

  • Lakshmi Reddy GopiReddy; Leon M. Tolbert; Burak Ozpineci; João O. P. Pinto
    IEEE Transactions on Industry Applications
    2015

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    Rainflow algorithms are one of the popular counting methods used in fatigue and failure analysis in conjunction with semiconductor lifetime estimation models. However, the rainflow algorithm used in power semiconductor reliability does not consider the time-dependent mean temperature calculation. The equivalent temperature calculation proposed by Nagode et al. is applied to semiconductor lifetime estimation in this paper. A month-long arc furnace load profile is used as a test profile to estimate temperatures in insulated-gate bipolar transistors (IGBTs) in a STATCOM for reactive compensation of load. The degradation in the life of the IGBT power device is predicted based on time-dependent temperature calculation.

  • Lakshmi Reddy GopiReddy; Leon M. Tolbert; Burak Ozpineci
    IEEE Transactions on Power Electronics
    2015

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    Reliability of power converters and lifetime prediction has been a major topic of research in the last few decades, especially for traction applications. The main failures in high power semiconductors are caused by thermomechanical fatigue. Power cycling and temperature cycling are the two most common thermal acceleration tests used in assessing reliability. The objective of this paper is to study the various power cycling tests found in the literature and to develop generalized steps in planning application specific power cycling tests. A comparison of different tests based on the failures, duration, test circuits, and monitored electrical parameters is presented.

  • Aleksandar Dimitrovski; Zhi Li; Burak Ozpineci
    IEEE Transactions on Power Delivery
    2015

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    The concept of the magnetic amplifier, a common electromagnetic device in electronic applications in the past, has seldom been used in power systems. The magnetic amplifier-based power-flow controller (MAPFC), an innovative low-cost device that adopts the idea of the magnetic amplifier for power-flow control applications, is introduced in this paper. The uniqueness of MAPFC is in the use of the magnetization of the ferromagnetic core, shared by an ac and a dc winding, as the medium to control the ac winding reactance inserted in series with the transmission line to be controlled. Large power flow in the line can be regulated by the small dc input to the dc winding. A project on the R&D of an MAPFC has been funded by the U.S. Department of Energy (DOE) and conducted by the Oak Ridge National Laboratory (ORNL), the University of Tennessee-Knoxville, and Waukesha Electric Systems, Inc. since early 2012. Findings from the project are presented along with some results obtained in a laboratory environment.

  • Mithat C. Kisacikoglu; Burak Ozpineci; Leon M. Tolbert
    IEEE Transactions on Power Electronics
    2013

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    This paper presents a summary of the available single-phase ac-dc topologies used for EV/PHEV, level-1 and -2 on-board charging and for providing reactive power support to the utility grid. It presents the design motives of single-phase on-board chargers in detail and makes a classification of the chargers based on their future vehicle-to-grid usage. The pros and cons of each different ac-dc topology are discussed to shed light on their suitability for reactive power support. This paper also presents and analyzes the differences between charging-only operation and capacitive reactive power operation that results in increased demand from the dc-link capacitor (more charge/discharge cycles and increased second harmonic ripple current). Moreover, battery state of charge is spared from losses during reactive power operation, but converter output power must be limited below its rated power rating to have the same stress on the dc-link capacitor.

  • Faete Filho; Helder Zandonadi Maia; Tiago H. A. Mateus; Burak Ozpineci; Leon M. Tolbert; João O. P. Pinto
    IEEE Transactions on Industrial Electronics
    2013

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    A new approach for modulation of an 11-level cascade multilevel inverter using selective harmonic elimination is presented in this paper. The dc sources feeding the multilevel inverter are considered to be varying in time, and the switching angles are adapted to the dc source variation. This method uses genetic algorithms to obtain switching angles offline for different dc source values. Then, artificial neural networks are used to determine the switching angles that correspond to the real-time values of the dc sources for each phase. This implies that each one of the dc sources of this topology can have different values at any time, but the output fundamental voltage will stay constant and the harmonic content will still meet the specifications. The modulating switching angles are updated at each cycle of the output fundamental voltage. This paper gives details on the method in addition to simulation and experimental results.

  • Hui Zhang; Leon M. Tolbert; Burak Ozpineci
    IEEE Transactions on Industry Applications
    2011

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    The application of silicon carbide (SiC) devices as battery interface, motor controller, etc., in a hybrid electric vehicle (HEV) will be beneficial due to their high-temperature capability, high-power density, and high efficiency. Moreover, the light weight and small volume will affect the whole powertrain system in a HEV and, thus, the performance and cost. In this paper, the performance of HEVs is analyzed using the vehicle simulation software Powertrain System Analysis Toolkit (PSAT). Power loss models of a SiC inverter based on the test results of latest SiC devices are incorporated into PSAT powertrain models in order to study the impact of SiC devices on HEVs from a system standpoint and give a direct correlation between the inverter efficiency and weight and the vehicle's fuel economy. Two types of HEVs are considered. One is the 2004 Toyota Prius HEV, and the other is a plug-in HEV (PHEV), whose powertrain architecture is the same as that of the 2004 Toyota Prius HEV. The vehicle-level benefits from the introduction of SiC devices are demonstrated by simulations. Not only the power loss in the motor controller but also those in other components in the vehicle powertrain are reduced. As a result, the system efficiency is improved, and vehicles that incorporate SiC power electronics are predicted to consume less energy and have lower emissions and improved system compactness with a simplified thermal management system. For the PHEV, the benefits are even more distinct; in particular, the size of the battery bank can be reduced for optimum design.

  • Faete Filho; Leon M. Tolbert; Yue Cao; Burak Ozpineci
    IEEE Transactions on Industry Applications
    2011

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    This work approximates the selective harmonic elimination problem using artificial neural networks (ANNs) to generate the switching angles in an 11-level full-bridge cascade inverter powered by five varying dc input sources. Each of the five full bridges of the cascade inverter was connected to a separate 195-W solar panel. The angles were chosen such that the fundamental was kept constant and the low-order harmonics were minimized or eliminated. A nondeterministic method is used to solve the system for the angles and to obtain the data set for the ANN training. The method also provides a set of acceptable solutions in the space where solutions do not exist by analytical methods. The trained ANN is a suitable tool that brings a small generalization effect on the angles' precision and is able to perform in real time (50-/60-Hz time window).

  • Burak Ozpineci; Leon Tolbert
    IEEE Spectrum
    2011

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    Silicon has long been the semiconductor of choice for such power electronics. But soon this ubiquitous substance will have to share the spotlight. Devices made from silicon carbide (SiC)-a faster, tougher, and more efficient alternative to straight silicon-are beginning to take off. Simple SiC diodes have already started to supplant silicon devices in some applica tions. And over the last few years, they've been joined by the first commercially available SiC transistors, enabling anew range of SiC-based power electronics. What's more, SiC wafer manufacturers have steadily reduced the defects in the material while increasing the wafer size, thus driving down the prices of SiC devices. Last year, according to estimates made by wafer maker Cree, the global market for silicon car bide devices topped US $100 million for the first time.

  • Zhong Du; Burak Ozpineci; Leon M. Tolbert; John N. Chiasson
    IEEE Transactions on Industry Applications
    2009

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    This paper presents a cascaded H-bridge multilevel boost inverter for electric vehicle (EV) and hybrid EV (HEV) applications implemented without the use of inductors. Currently available power inverter systems for HEVs use a dc-dc boost converter to boost the battery voltage for a traditional three-phase inverter. The present HEV traction drive inverters have low power density, are expensive, and have low efficiency because they need a bulky inductor. A cascaded H-bridge multilevel boost inverter design for EV and HEV applications implemented without the use of inductors is proposed in this paper. Traditionally, each H-bridge needs a dc power supply. The proposed design uses a standard three-leg inverter (one leg for each phase) and an H-bridge in series with each inverter leg which uses a capacitor as the dc power source. A fundamental switching scheme is used to do modulation control and to produce a five-level phase voltage. Experiments show that the proposed dc-ac cascaded H-bridge multilevel boost inverter can output a boosted ac voltage without the use of inductors.

  • Burak Ozpineci; Madhu Sudhan Chinthavali; Leon M. Tolbert; Avinash S. Kashyap; H. Alan Mantooth
    IEEE Transactions on Industry Applications
    2009

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    Silicon carbide (SiC) power devices are expected to have an impact on power converter efficiency, weight, volume, and reliability. Currently, only SiC Schottky diodes are commercially available at relatively low current ratings. Oak Ridge National Laboratory has collaborated with Cree and Semikron to build a Si insulated-gate bipolar transistor-SiC Schottky diode hybrid 55-kW inverter by replacing the Si p-n diodes in Semikron's automotive inverter with Cree's made-to-order higher current SiC Schottky diodes. This paper presents the developed models of these diodes for circuit simulators, shows inverter test results, and compares the results with those of a similar all-Si inverter.

  • Zhong Du; Leon M. Tolbert; Burak Ozpineci; John N. Chiasson
    IEEE Transactions on Power Electronics
    2009

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    This paper presents a cascaded H-bridge multilevel inverter that can be implemented using only a single dc power source and capacitors. Standard cascaded multilevel inverters require n dc sources for 2n + 1 levels. Without requiring transformers, the scheme proposed here allows the use of a single dc power source (e.g., a battery or a fuel cell stack) with the remaining n-1 dc sources being capacitors, which is referred to as hybrid cascaded H-bridge multilevel inverter (HCMLI) in this paper. It is shown that the inverter can simultaneously maintain the dc voltage level of the capacitors and choose a fundamental frequency switching pattern to produce a nearly sinusoidal output. HCMLI using only a single dc source for each phase is promising for high-power motor drive applications as it significantly decreases the number of required dc power supplies, provides high-quality output power due to its high number of output levels, and results in high conversion efficiency and low thermal stress as it uses a fundamental frequency switching scheme. This paper mainly discusses control of seven-level HCMLI with fundamental frequency switching control and how its modulation index range can be extended using triplen harmonic compensation.

  • Zhong Du; Leon M. Tolbert; John N. Chiasson; Burak Ozpineci
    IEEE Transactions on Industrial Electronics
    2008

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    This paper presents a reduced switching-frequency active-harmonic-elimination method (RAHEM) to eliminate any number of specific order harmonics of multilevel converters. First, resultant theory is applied to transcendental equations to eliminate low-order harmonics and to determine switching angles for a fundamental frequency-switching scheme. Next, based on the number of harmonics to be eliminated, Newton climbing method is applied to transcendental equations to eliminate high-order harmonics and to determine switching angles for the fundamental frequency-switching scheme. Third, the magnitudes and phases of the residual lower order harmonics are computed, generated, and subtracted from the original voltage waveform to eliminate these low-order harmonics. Compared to the active-harmonic-elimination method (AHEM), which generates square waves to cancel high-order harmonics, RAHEM has lower switching frequency. The simulation results show that the method can effectively eliminate all the specific harmonics, and a low total harmonic distortion (THD) near sine wave is produced. An experimental 11-level H-bridge multilevel converter with a field-programmable gate-array controller is employed to experimentally validate the method. The experimental results show that RAHEM does effectively eliminate any number of specific harmonics, and the output voltage waveform has low switching frequency and low THD.

  • X. Yu; M.R. Starke; L.M. Tolbert; B. Ozpineci
    IET Electric Power Applications
    2007

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    Fuel cells are considered to be one of the most promising sources of distributed energy because of their high efficiency, low environmental impact and scalability. Unfortunately, multiple complications exist in fuel cell operation. Fuel cells cannot accept current in the reverse direction, do not perform well with ripple current, have a low output voltage that varies with age and current, respond sluggishly to step changes in load and are limited in overload capabilities. For these reasons, power converters are often necessary to boost and regulate the voltage as a means to provide a stiff applicable DC power source. Furthermore, the addition of an inverter allows for the conversion of DC power to AC for an utility interface or for the application of an AC motor. To help motivate the use of power conditioning for the fuel cell, a brief introduction of the different types, applications and typical electrical characteristics of fuel cells is presented. This is followed by an examination of the various topologies of DC-DC boost converters and inverters used for power conditioning of fuel cells. Several architectures to aggregate multiple fuel cells for high-voltage/high-power applications are also reviewed.

  • Jeremy B. Campbell; Leon M. Tolbert; Curt W. Ayers; Burak Ozpineci; Kirk T. Lowe
    IEEE Transactions on Industry Applications
    2007

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    This paper presents a two-phase cooling method using the R134a refrigerant to dissipate the heat energy (loss) generated by power electronics (PEs), such as those associated with rectifiers, converters, and inverters for a specific application in hybrid-electric vehicles. The cooling method involves submerging PE devices in an R134a bath, which limits the junction temperature of PE devices while conserving weight and volume of the heat sink without sacrificing equipment reliability. First, experimental tests that included an extended soak for more than 850 days were performed on a submerged insulated gate bipolar transistor (IGBT) and gate-controller card to study dielectric characteristics, deterioration effects, and heat-flux capabilities of R134a. Results from these tests illustrate that R134a has high dielectric characteristics and no deterioration of electrical components. Second, experimental tests that included a simultaneous operation with a mock automotive air-conditioner (A/C) system were performed on the same IGBT and gate-controller card. Data extrapolation from these tests determined that a typical automotive A/C system has more than sufficient cooling capacity to cool a typical 30-kW traction inverter. Last, a discussion and simulation of active cooling of the IGBT junction layer with the R134a refrigerant is given. This technique will drastically increase the forward current ratings and reliability of the PE device

  • B. Ozpineci; L.M. Tolbert; J.N. Chiasson
    IEEE Power Electronics Letters
    2005

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    In this letter, a genetic algorithm (GA) optimization technique is applied to determine the switching angles for a cascaded multilevel inverter which eliminates specified higher order harmonics while maintaining the required fundamental voltage. This technique can be applied to multilevel inverters with any number of levels. As an example, in this paper a seven-level inverter is considered, and the optimum switching angles are calculated offline to eliminate the fifth and seventh harmonics. These angles are then used in an experimental setup to validate the results.

  • B. Ozpineci; L.M. Tolbert
    IEEE Power Electronics Letters
    2003

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    The emergence of silicon carbide (SiC) based power semiconductor switches, with their superior features compared with silicon (Si) based switches, has resulted in substantial improvement in the performance of power electronics converter systems. These systems with SiC power devices have the qualities of being more compact, lighter, and more efficient; thus, they are ideal for high-voltage power electronics applications. In this study, commercial Si pn and SiC Schottky diodes are tested and characterized, their behavioral static and loss models are derived at different temperatures, and they are compared with respect to each other.

Conference Papers
Title
Year
  • Utkarsh D. Kavimandan; Veda P. Galigekere; Omer Onar; Burak Ozpineci; Satish M. Mahajan
    2020 IEEE Applied Power Electronics Conference and Exposition (APEC)
    2020

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    In practice, a dead-time is always provided between the complementary switching instances of the inverter phase-leg devices. At higher operating frequencies, the dead-time issues in wireless power transfer (WPT) systems become critical, especially as the power level increases. In certain operating conditions, the dead-time effect in wireless power transfer system affects the switching characteristics. Consequently, the switching losses in the power semiconductor devices increase and also impact the efficiency of the overall system. In this paper, a simple control scheme is proposed to eliminate the dead-time effect (or voltage polarity reversal) in the WPT inverter. The proposed control scheme monitors the inverter output voltage, and the switching frequency is auto-tuned to eliminate the undesired switching instances in the inverter voltage. The proposed control scheme is validated using the closed-loop simulations in PLECS, and the experimental results on a 5.6 kW WPT prototype are also presented. After eliminating the voltage-polarity-reversal at the inverter output, the inverter losses were reduced by ∼40%, and the overall system losses were reduced by ∼17%.

  • Subhajyoti Mukherjee; Veda P. Galigekere; Omer Onar; Burak Ozpineci
    2020 IEEE Applied Power Electronics Conference and Exposition (APEC)
    2020

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    This paper presents the use of feedforward control to reduce the input side DC link capacitance of series-series compensated wireless power transfer (WPT) systems. Compared to conventional control schemes for WPT systems, the proposed feedforward-based approach achieves significant reduction in the DC link capacitor without any complicated voltage or current sensing requirements from the secondary side. This results in more compact hardware architecture. The proposed method shows minimal increase in the turn-on switching loss of the inverter. The switching loss is analyzed, and detailed results are presented relating the switching loss to the DC link capacitance and voltage ripple for proper tradeoff between losses and capacitor size. Simulation and experimental results presented validate the proposed scheme.

  • Erdem Asa; Jason Pries; Veda Galigekere; Subho Mukherjee; Omer C. Onar; Gui-Jia Su; Burak Ozpineci
    2020 IEEE Applied Power Electronics Conference and Exposition (APEC)
    2020

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    In this paper, a novel ac to ac wireless power transfer (WPT) system is introduced for electric vehicle (EV) charging applications to reduce cost and design complexity. The presented wireless power transfer concept achieves unity power factor (UPF) on the grid-side by using a hybrid frequency ac / ac converter without an additional converter stage and closed loop control compared to the conventional systems. Due to inherent merit of the proposed ac / ac converter, ac input with 60 Hz grid frequency can be directly transferred to the load by superimposing with high frequency switching signal through the wireless coils. To validate the theoretical analysis of the proposed WPT system, the experimental results of the proposed converter are provided for 650 W output power by using 6 inches air gap between the couplers with the input of 110 VRMS ac source. The system overall efficiency is measured 89 % achieving 0.99 power factor (PF) and 1.5 % current total harmonic distortion (THD).

  • Erdem Asa; Kerim Colak; Dariusz Czarkowski; Burak Ozpineci
    2020 IEEE Applied Power Electronics Conference and Exposition (APEC)
    2020

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    A high frequency AC link isolated three port semi-bridgeless resonant converter is analyzed for unmanned aerial vehicle (UAV) applications in this study. The proposed topology is established by replacing rectifier lover diodes with synchronous switches. A phase shifted pulse width modulation (PS-PWM) technique adjusts bi-directional power flow between ports. Proposed control technique provides high efficiency by reducing switching losses with zero voltage switching (ZVS) and zero current switching (ZCS) in a wide power range regulation. Compared to integrated PWM converters in a bi-directional mode, the proposed topology reduces the number of converter stages and allows centralized control at high operating frequency. Theoretical and experimental results demonstrate the feasibility and effectiveness of the proposed converter at a full power of 500 W in laboratory conditions.

  • Emre Gurpinar; Burak Ozpineci; John Preston Spires; Wei Fan
    2020 IEEE Applied Power Electronics Conference and Exposition (APEC)
    2020

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    Next generation power modules demand increased heat extraction capability along with reduced weight and volume. In this paper, thermally annealed pyrolytic graphite (TPG) is analyzed and compared with conventional materials used in power modules for thermal management. Fundamental properties of TPG are explained and compared with commonly used materials in power module heat spreaders and substrates. The encapsulated TPG based heat spreader is manufactured and compared with bulk copper in simulation and experimental based analysis. The results show that encapsulated TPG based heat spreader achieves more than 50% reduction in thermal resistance along with 48% reduction in weight in the heat spreader layer.

  • Utkarsh D. Kavimandan; Veda P. Galigekere; Burak Ozpineci; Omer Onar
    2019 IEEE Transportation Electrification Conference and Expo (ITEC)
    2019

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    In this paper, the effect of dead-time in a single phase wireless power transfer system (WPT) between the complementary switching pulses of the inverter leg is discussed in detail. The dead-time is always provided between the complementary switching pulses in the inverter leg to avoid the short-circuit of the input dc source. In WPT systems, high-frequency (HF) operation is desired to reduce the size of the passive components. As the frequency of operation increases, the dead-time effect becomes significant and must be addressed appropriately. This paper presents the analysis of the dead-time effect in the wireless power transfer system for an electric vehicle (EV) battery charging application. The operating waveforms for the given operating condition of the phase-shift angle and the power-factor are presented and the phenomenon of voltage polarity reversal (VPR) or notch is discussed. The effect of the notch on the fundamental component of the voltage is presented and the effect of the notch on the BMW i3 battery charging profile is evaluated. The theoretical analysis of the dead-time is verified using simulation results in PLECS.

  • Shajjad Chowdhury; Emre Gurpinar; Gui-Jia Su; Tsarafidy Raminosoa; Timothy A. Burress; Burak Ozpineci
    2019 IEEE Transportation Electrification Conference and Expo (ITEC)
    2019

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    The electric traction drive is the main consumer of the stored energy in an electric vehicle. Therefore, the drive system must perform with high efficiency to maximize the vehicle range for given battery capacity. Since the introduction of hybrid electric vehicles, various innovative traction drive technologies have been implemented in commercially available electric vehicles to increase efficiency and power density. It is expected that the power density and performance of the traction drive unit must improve significantly for future electric vehicles to increase the user space in the vehicle, extend the range and increase market adoption. US Department of Energy (DOE)has recently announced technical targets for light duty electric vehicles. DOE targets to reach a power density target of 33 kW/L for a 100 kW traction drive system by 2025. It is an increment by a factor of 5.5 in comparison to the state-of-the-art. This paper investigates the current trends in commercially available electric drives for light-duty automotive applications, identifies the challenges, and discusses innovative technologies to overcome the power density barrier.

  • Yongwan Park; Omer C. Onar; Burak Ozpineci
    2019 IEEE CyberPELS (CyberPELS)
    2019

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    Potential issues of front-end converters of wireless power transfer system modules for extreme fast charging are discussed and analyzed in this study in order to provide some recommendations to defend against attacks on electric vehicles and charging systems. Compared to conventional low-power charging systems, the impact of a cyber-attack might be more detrimental in high-power / fast charging systems since the fault energy levels would be inherently higher both on the grid- and vehicle- side converters. In order to analyze the potential issues that might be a result of cyber-attacks, the negative scenarios are reviewed in this study which include interfering with the grid-side controllers, establishing fake communications between the vehicles and the charging stations, and interfering with the battery management system functionalities. A 100-kW stationary wireless power transfer system with a series-series resonant compensation network is used as a representative system in the analysis. Potential damages and the fault energy levels for selected fault scenarios are investigated. The system is simulated to verify the analysis results. On the basis of the discussed worst-case study, a set of hardware design-level solutions are recommended in this study to provide cyber protection.

  • Andrew Foote; Omer C. Onar; Suman Debnath; Jason Pries; Veda Prakash Galigekere; Burak Ozpineci
    2019 IEEE Transportation Electrification Conference and Expo (ITEC)
    2019

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    Dynamic wireless power transfer (DWPT) has been proposed as a solution to power electric vehicles (EVs)on future electrified highways. However, there has been little consideration of how the coordination of electric connected and automated vehicles (CAVs) could impact DWPT system designs in future scenarios. In this paper, a DWPT system design is optimized for a future highway where CAVs travel in coordinated groups, with each CAV in the group powered by the same DWPT section. As the distribution of smaller light-duty vehicles (LDVs) and larger heavy-duty vehicles (HDVs) in each group is varied, the DWPT system power level, transmitter length, and the equivalent receiver loads are adjusted to minimize the infrastructure requirements and energy losses of the DWPT system. The outputs from this analysis are used to determine the optimal groupings of vehicles for a given DWPT system. The analysis suggests that CAV coordination could aid the deployment of DWPT systems and reduce the overall infrastructure and energy losses of DWPT systems.

  • Jared A. Baxter; Daniel A. Merced; Daniel J. Costinett; Leon M. Tolbert; Burak Ozpineci
    2018 IEEE Transportation Electrification Conference and Expo (ITEC)
    2018

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    Automated vehicles require sensors and computer processing that can perceive the surrounding environment and make real time decisions. These additional electrical loads expand the auxiliary load profile, therefore reducing the range of an automated electric vehicle compared to a standard electric vehicle. Furthermore, a fully automated vehicle must be fail-safe from sensor to vehicle control, thus demanding additional electrical loads due to redundancies in hardware throughout the vehicle. This paper presents a review of the sensors needed to make a vehicle automated, the power required for these additional auxiliary loads, and the necessary electrical architectures for increasing levels of robustness.

  • A. Foote; O. C. Onar; S. Debnath; M. Chinthavali; B. Ozpineci; D. E. Smith
    2018 IEEE Transportation Electrification Conference and Expo (ITEC)
    2018

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    Inductive power transfer has been proposed as a solution to power future automated and electrified highways. In this study, an interoperable wireless charging system is sized so that a light and a heavy-duty vehicle can travel at or near charge-sustaining mode at high speeds using an optimization approach. The conflicting objectives of minimizing the power ratings and the number of inverters, coupler materials, and overall system coverages result in a Pareto Front that is presented in this paper. It is found that a system using short transmitting couplers can ensure high efficiency power transfers to light-duty vehicles (LDVs) and still maintain charge-sustaining operation of heavy-duty vehicles (HDVs). The findings are contextualized by a brief discussion of other aspects relating to the implementation of this technology on roadways such as the impact of the cost of time and travel speeds.

  • Emre Gurpinar; Burak Ozpineci
    2018 IEEE Transportation Electrification Conference and Expo (ITEC)
    2018

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    Emerging wide-bandgap based power semiconductor devices are gaining popularity in power electronic systems for automotive applications with the aim of increased power density, reduced weight and increased efficiency. In this work, loss analysis and mapping of a segmented two-level inverter based on SiC MOSFETs are presented in order to identify the challenges in design of power electronics and electric machines for EV applications. The paper starts with description of the EV traction system that is chosen as the study case, followed by segmented inverter topology, power device selection and sizing. The theoretical switching, conduction and dead-time conduction loss analysis for the SiC MOSFETs in the segmented two-level inverter topology are presented under any given operating condition. The analysis is followed by loss mapping of the motor, inverter and overall EV traction system. The loss maps of the inverter and the motor show that each component has different thermal loading trends under given torque-speed characteristics. Therefore, various operating conditions have to be considered for the design of traction system components to ensure reliability and high performance, which are critical requirements for EV systems.

  • Emre Gurpinar; Randy Wiles; Burak Ozpineci; Tsarafidy Raminosoa; Feng Zhou; Yanghe Liu; Ercan M. Dede
    2018 IEEE Energy Conversion Congress and Exposition (ECCE)
    2018

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    Wide bandgap (WBG) power semiconductor devices, specifically silicon carbide (SiC) metal-oxide-semiconductor field-effect transistors (MOSFETs) have gained attention from electric vehicle (EV) system developers due to well-known superior properties in comparison to industry standard silicon (Si) based MOSFETs and insulated-gate bipolar transistors (IGBTs). In this work, a power module design based on SiC MOSFETs in a segmented two-level, three-phase inverter topology with 125 kW peak output power and 30 kHz switching frequency is presented. Three different SiC MOSFET die options are analyzed according to experimentally obtained operating conditions of a commercial EV traction system. Substrate design of the power module for multi-die layout, heat sink design, and integration of a segmented phase leg module are presented. Finite-element electrical and thermal analysis of the proposed system are presented and discussed.

  • Tong Wu; Burak Ozpineci
    2018 IEEE Transportation Electrification Conference and Expo (ITEC)
    2018

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    This paper focuses on understanding the thermal impacts of using discrete power devices and limitations of applying conventional thermal design methods. Empirically, a thermal system is designed based on selecting a heat sink with the required thermal resistance from the manufacturer datasheet. This method, as an approximate estimation, has been proven effective as a rough design of Si-based power module. However, wide bandgap (WBG) bare dies bring additional thermal design concerns that have been overlooked. The benefits of WBG devices, such as smaller chip sizes and higher power ratings, on the other hand, lead to thermal concentration issues. Detailed analyses and impacts of the thermal concentration are presented in this paper. A more accurate model involving Finite Element Analysis (FEA) and Genetic Algorithm optimization is also proposed for a more accurate thermal design.

  • Madhu Chinthavali; Zhiqiang Jack Wang; Steven Campbell; Tong Wu; Burak Ozpineci
    2018 IEEE Applied Power Electronics Conference and Exposition (APEC)
    2018

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    The traditional heatsink design technologies for forced air-cooling and power semiconductors with low junction temperatures have constrained the converters to be designed with massive heatsinks. The low power losses of WBG device technology and higher junction temperature operation over a wide operating range of power have not been fully utilized with liquid-cooled systems. The other major limitation has also been the traditional power module packaging “stack” approach with baseplate. This paper presents a novel power stage design which involves 1.7 kV silicon carbide (SiC) MOSFETs, a heatsink design with Genetic Algorithm (GA) and built using 3D printing technology, and a novel integrated modular power module for high power density. The air-cooled module assembly has a SiC MOSFET phase leg module with split high-side and low-side switches and a gate driver with cross-talk and short circuit protection functions. The heatsink design was modeled using a co-simulation environment with finite element analysis software and GA in MATLAB and COMSOL. The proposed concepts were verified and validated through experiments at each stage of development. The power stage was evaluated at 800V, 900 V, and 1kV for 20 kHz switching frequency and 50-kW load. The experimental results show that the CEC efficiency is 98.4 %. In addition to the efficiency, a power density of 75 W/in3 was also achieved.

  • Marcio Kimpara; Pedro Ribeiro Luiz; E.B. Silva; João O. P. Pinto; Darizon A. de Andrade; Babak Fahimi; Burak Ozpineci; Morgan Kiani
    2017 IEEE 26th International Symposium on Industrial Electronics (ISIE)
    2017

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    Conventional drives for switched reluctance motors (SRMs) consists in supplying DC current pulses sequentially in each stator phase according to rotor position. This square current excitation produces a pulsating torque that limits the SRM applications. This paper aims to improve the torque profile of a 8/6 SRM applying an optimized current excitation obtained using the Field Reconstruction Method (FRM). First, the SRM is modeled in a Finite Element (FE) software as a FRM requirement and further the FRM model replaces the FE model in a interactive optimization routine. Simulation results shown that shaping the excitation current appropriately, the torque ripple can be reduced in approximately 80%.

  • Nomar S. González-Santini; Burak Ozpineci; Madhu Chinthavali; Fang Zheng Peng
    2017 IEEE Transportation Electrification Conference and Expo (ITEC)
    2017

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    In this paper, the effects of the resonant network characteristic and control variables on the dc-link capacitor of a wireless charger are investigated for electric vehicles, by deriving an analytical expression for the capacitance in terms of the resonant network parameters and system control variables. With this equation, the minimum dc-link capacitance needed can be obtained to keep the dc-link voltage ripple within a desired limit for a wide load range. A comparison between the conventional series-primary resonant networks in terms of the dc-link capacitance needs is presented as well as simulation results to validate the derived equation.

  • Tong Wu; Burak Ozpineci; Madhu Chinthavali; Zhiqiang Wang; Suman Debnath; Steven Campbell
    2017 IEEE Transportation Electrification Conference and Expo (ITEC)
    2017

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    Enhancing power density and reliability of power electronics is extremely important in power electronics applications. One of the key challenges in the design process is to design the optimum heat sink. In this paper, an algorithm is proposed to design air-cooled heat sinks using genetic algorithm (GA) and finite element analysis (FEA) simulations. While the GA generates a population of candidate heat sinks in each iteration, FEA simulations are used to evaluate the fitness function of each. The fitness function considered in this paper is the maximum junction temperature of the semiconductor devices. With an approach that prefers “survival of the fittest”, a heat sink providing better performance than the conventional heat sinks is obtained. The simulation and experimental evaluations of the optimized air-cooled heat sink are also included in the paper.

  • Jessica D. Boles; Burak Ozpineci; Leon M. Tolbert; Timothy A. Burress; Curt W. Ayers; Jared A. Baxter
    2016 IEEE Power and Energy Society General Meeting (PESGM)
    2016

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    Transmission line inspection becomes increasingly more important as power system infrastructure ages because proactively identifying line maintenance needs is crucial for minimizing outages. Utilizing robots to conduct such inspections is both safer for humans and less costly in terms of labor, but finding an appropriate on-line robot design presents its own set of challenges. This paper proposes a touch-free transmission line inspection system in which an unmanned aerial vehicle (UAV) conducts all inspection activities and, while doing so, charges from the line via inductive power transmission. Two coil designs are presented and tested for this charging application - one with an air core and one with a line-enclosing core clamp. Finally, the benefits and challenges associated with each design are discussed, along with the general practicality of inductive charging via transmission lines for UAV applications.

  • Tong Wu; Burak Ozpineci; Curtis Ayers
    2016 IEEE Applied Power Electronics Conference and Exposition (APEC)
    2016

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    In this paper, a genetic algorithm- (GA-) based approach is discussed for designing heat sinks based on total heat generation and dissipation for a pre-specified size and shape. This approach combines random iteration processes and genetic algorithms with finite element analysis (FEA) to design the optimized heat sink. With an approach that prefers “survival of the fittest”, a more powerful heat sink can be designed which can cool power electronics more efficiently. Some of the resulting designs can only be 3D printed due to their complexity. In addition to describing the methodology, this paper also includes comparisons of different cases to evaluate the performance of the newly designed heat sink compared to commercially available heat sinks.

  • Tong Wu; Andrew A. Wereszczak; Hsin Wang; Burak Ozpineci; Curt W. Ayers
    2016 International Symposium on 3D Power Electronics Integration and Manufacturing (3D-PEIM)
    2016

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    The thermal response of a liquid-cooled, 3D-printed aluminum heat sink is compared to that for a conventionally-manufactured aluminum 6061 heat sink of identical geometry. Differences in thermal response were observed; however, the employed 3D-printed aluminum composition could be annealed to produce equivalent thermal characteristics to that of Al 6061. The achievement of that thermal equivalency indicates that the attractive attributes of 3D-printing can be exploited for heat exchangers with a simple and additional processing step.

  • Andrew Foote; Burak Ozpineci; Madhu Chinthavali; Jan-Mou Li
    2016 IEEE PELS Workshop on Emerging Technologies: Wireless Power Transfer (WoW)
    2016

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    Dynamic wireless charging is a possible cure for the range limitations seen in electric vehicles (EVs) once implemented in highways or city streets. The contribution of this paper is the use of experimental data to show that the expected energy gain from a dynamic wireless power transfer (WPT) system is largely a function of average speed, which allows the power level and number of coils per mile of a dynamic WPT system to be sized for the sustained operation of an EV. First, data from dynamometer testing is used to determine the instantaneous energy requirements of a light-duty EV. Then, experimental data is applied to determine the theoretical energy gained by passing over a coil as a function of velocity and power level. Related simulations are performed to explore possible methods of placing WPT coils within roadways with comparisons to the constant velocity case. Analyses with these cases demonstrate what system ratings are needed to meet the energy requirements of the EV and what effect longitudinal alignment has on WPT. The simulations are also used to determine onboard energy storage requirements for each driving cycle.

  • Lakshmi GopiReddy; Leon M. Tolbert; Burak Ozpineci; João O. P. Pinto
    2014 IEEE Applied Power Electronics Conference and Exposition - APEC 2014
    2014

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    Rainflow algorithms are one of the best counting methods used in fatigue and failure analysis popularly used in semiconductor lifetime estimation models. However, the rainflow algorithm used in power semiconductor reliability does not consider the time dependent mean temperature calculation. The equivalent temperature calculation proposed by Nagode et al is applied to semiconductor lifetime estimation for the first time in this paper. A month long arc furnace load profile is used as a test profile to estimate temperatures in IGBT in a STATCOM for reactive compensation of load. The degradation in the life of the IGBT power device is predicted based on time dependent temperature calculation.

  • Lakshmi Gopi Reddy; Leon M. Tolbert; Burak Ozpineci
    2014 IEEE Applied Power Electronics Conference and Exposition - APEC 2014
    2014

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    Lifetime estimation of power semiconductors for various applications has gained technical importance. The main failures in high power semiconductors are caused by thermo-mechanical fatigue, mainly in solder and wirebonds, due to different coefficients of thermal expansions of the various packaging materials. Most of the lifetime models do not take all the operating parameters into account. There is a need to develop a generalized lifetime model specific to failure mechanisms that account for all of the operating parameters in an application. This paper presents finite element based stress simulations for varying operating parameters (current, temperature, etc.) for a fixed dimension wire.

  • Edward A. Jones; Fred Wang; Burak Ozpineci
    2014 IEEE Workshop on Wide Bandgap Power Devices and Applications
    2014

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    Normally-off GaN-on-Si heterojunction field-effect transistors (HFETs) have been developed with up to 650 V blocking capability, fast switching, and low conduction losses in commercial devices. The natively depletion-mode device can be modified to be normally-off using a variety of techniques. For a power electronics engineer accustomed to Si-based converter design, there is inherent benefit to understanding the unique characteristics and challenges that distinguish GaN HFETs from Si MOSFETs. Dynamic Rds-on self-commutated reverse conduction, gate voltage and current requirements, and the effects of very fast switching are explained from an applications perspective. This paper reviews available literature on commercial and near-commercial GaN HFETs, to prepare engineers with Si-based power electronics experience to effectively design GaN-based converters.

  • A. Dimitrovski; Z. Li; B. Ozpineci
    2014 IEEE PES T&D Conference and Exposition
    2014

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    The study of the saturable-core reactor (SCR) can be traced back to 1900's. Although commonly used in electronic circuit applications, SCR has seldom been used in power system applications. In recent years, power engineers have raised interest in exploring applications of SCR in power systems. The SCR is low-cost and durable. Its nature of using the magnetic field as control medium makes it more familiar and, perhaps, more easily accepted by power utilities. In this paper, the basic concept of SCR and some existing or potential applications of SCR in power systems are introduced. A project on the R&D of a SCR-based power flow controller has been funded by the U.S. Department of Energy (DOE) and conducted by the Oak Ridge National Laboratory (ORNL), the University of Tennessee-Knoxville, and Waukesha Electric Systems, Inc. since early 2012. Some technical details of the project are presented and some preliminary results are highlighted.

  • Madhu Chinthavali; Curt Ayers; Steven Campbell; Randy Wiles; Burak Ozpineci
    2014 IEEE Workshop on Wide Bandgap Power Devices and Applications
    2014

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    With efforts to reduce the cost, size, and thermal management systems for the power electronics drivetrain in hybrid electric vehicles (HEVs) and plug-in hybrid electric vehicles (PHEVs), wide band gap semiconductors including silicon carbide (SiC) have been identified as possibly being a partial solution. This paper focuses on the development of a 10-kW all SiC inverter using a high power density, integrated printed metal power module with integrated cooling using additive manufacturing techniques. This is the first ever heat sink printed for a power electronics application. About 50% of the inverter was built using additive manufacturing techniques.

  • Bailu Xiao; Lijun Hang; Cameron Riley; Leon M. Tolbert; Burak Ozpineci
    2013 Twenty-Eighth Annual IEEE Applied Power Electronics Conference and Exposition (APEC)
    2013

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    A three-phase modular cascaded H-bridge multilevel inverter for a grid-connected photovoltaic (PV) system is presented in this paper. To maximize the solar energy extraction of each PV string, an individual maximum power point tracking (MPPT) control scheme is applied, which allows the independent control of each dc-link voltage. PV mismatches may introduce unbalanced power supplied to the three-phase system. To solve this issue, a control scheme with modulation compensation is proposed. The three-phase modular cascaded multilevel inverter prototype has been built. Each H-bridge is connected to a 185 W solar panel. Simulation and experimental results are presented to validate the proposed ideas.

  • M. Saadeh; Madhu S. Chinthavali; Burak Ozpineci; H. A. Mantooth
    2013 IEEE Energy Conversion Congress and Exposition
    2013

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    Ac-ac matrix converters and cycloconverters require bi-directional switches, which are typically formed by two antiparallel thyristors or a two-switch (IGBT/MOSFETs) two-diode configuration. As silicon carbide (SiC) and gallium nitride (GaN) devices become more available, it is possible to have higher voltage FETs with low conduction and switching losses and reverse conduction capability, which allows the elimination of the diodes in a bidirectional switch. This paper will investigate a bidirectional switch formation that is formed by using two normally-on SiC JFETs in anti-series with no anti-parallel diodes.

  • Lakshmi Gopi Reddy; Leon M. Tolbert; Burak Ozpineci; Yan Xu; D. Tom Rizy
    2012 Twenty-Seventh Annual IEEE Applied Power Electronics Conference and Exposition (APEC)
    2012

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    With smart grid integration, there is a need to characterize reliability of a power system by including reliability of power semiconductors in grid related applications. In this paper, the reliability of IGBTs in a STATCOM application is presented for two different applications, power factor correction and harmonic elimination. The STATCOM model is developed in EMTP, and analytical equations for average conduction losses in an IGBT and a diode are derived and compared with experimental data. A commonly used reliability model is used to predict reliability of IGBT.

  • Lakshmi GopiReddy; Leon M. Tolbert; Burak Ozpineci
    IECON 2012 - 38th Annual Conference on IEEE Industrial Electronics Society
    2012

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    Rainflow algorithms are one of the best counting methods used in fatigue and failure analysis [17]. There have been many approaches to the rainflow algorithm, some proposing modifications. Graphical Rainflow Method (GRM) was proposed recently with a claim of faster execution times [10]. However, the steps of the graphical method of rainflow algorithm, when implemented, do not generate the same output as the four-point or ASTM standard algorithm. A modified graphical method is presented and discussed in this paper to overcome the shortcomings of graphical rainflow algorithm. A fast rainflow algorithm based on four-point algorithm but considering point comparison than range comparison is also presented. A comparison between the performances of the common rainflow algorithms [6-10], including the proposed methods, in terms of execution time, memory used, and efficiency, complexity, and load sequences is presented. Finally, the rainflow algorithm is applied to temperature data of an IGBT in assessing the lifetime of a STATCOM operating for power factor correction of the load. From 5-minute data load profiles available, the lifetime is estimated to be at 3.4 years.

  • Faete J. T. Filho; Leon M. Tolbert; Burak Ozpineci
    Proceedings of The 7th International Power Electronics and Motion Control Conference
    2012

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    The work developed here proposes a methodology for calculating switching angles for varying DC sources in a multilevel cascaded H-bridges converter. In this approach the required fundamental is achieved, the lower harmonics are minimized, and the system can be implemented in real time with low memory requirements. Genetic algorithm (GA) is the stochastic search method to find the solution for the set of equations where the input voltages are the known variables and the switching angles are the unknown variables. With the dataset generated by GA, an artificial neural network (ANN) is trained to store the solutions without excessive memory storage requirements. This trained ANN then senses the voltage of each cell and produces the switching angles in order to regulate the fundamental at 120 V and eliminate or minimize the low order harmonics while operating in real time.

  • Michael Pickelsimer; Leon Tolbert; Burak Ozpineci; John M. Miller
    2012 IEEE International Electric Vehicle Conference
    2012

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    Wireless power transfer has been a popular topic of recent research. Most research has been done to address the limitations of coil-to-coil efficiency. However, little has been done to address the problem associated with the low input power factor with which the systems operate. This paper details the steps taken to analyze a wireless power transfer system from the view of the power grid under a variety of loading conditions with and without power factor correction.

  • Mithat C. Kisacikoglu; Burak Ozpineci; Leon M. Tolbert; Fred Wang
    2011 Twenty-Sixth Annual IEEE Applied Power Electronics Conference and Exposition (APEC)
    2011

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    Vehicle to grid (V2G) power transfer has been under research for more than a decade because of the large energy reserve of an electric vehicle battery and the potential of thousands of these connected to the grid. In this study a complete analysis of the front end inverter of a non-isolated bidirectional EV/PHEV charger capable of V2G reactive power compensation is presented.

  • Lakshmi GopiReddy; Leon M. Tolbert; Burak Ozpineci; Yan Xu; Tom Rizy
    2011 IEEE Energy Conversion Congress and Exposition
    2011

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    Most of the failures in IGBTs are caused by thermal fatigue. Hence, the thermal analysis of IGBTs for each particular application is an important step in determining their lifetime. In this paper, the thermal analysis of a STATCOM is presented for two different applications, power factor correction and harmonic elimination. The STATCOM model is developed in EMTP for the above mentioned functions. The analytical equations for average conduction losses in an IGBT and a diode are derived. The electrothermal model is used to estimate the temperature of the IGBT. A comparative analysis of the thermal stresses on the IGBT with various parameters such as power factor, harmonic frequency, and harmonic amplitude is presented as a basis for future reliability testing of IGBTs in FACTS applications.

  • Mithat C. Kisacikoglu; Burak Ozpineci; Leon M. Tolbert
    8th International Conference on Power Electronics - ECCE Asia
    2011

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    More battery powered electric vehicles (EVs) and plug-in hybrid electric vehicles (PHEVs) will be introduced to the market in 2011 and beyond. PHEVs/EVs potentially have the capability to fulfill the energy storage needs of the electric grid by supplying ancillary services such as reactive power compensation, voltage regulation, and peak shaving since they carry an on-board battery charger. However, to allow bidirectional power transfer, the PHEV battery charger should be designed to manage such reactive power capability. This study shows how bidirectional four quadrant operation affects the design stage of a conventional unidirectional charger and the operation of the battery pack. Mainly, the subjects that are discussed are the following: required topology updates, dc link capacitor (voltage and current), ac inductor (current), rectifier (power loss), and battery pack (voltage and current).

  • Faete Filho; Leon Tolbert; Burak Ozpineci
    2011 IEEE Energy Conversion Congress and Exposition
    2011

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    This work presents an approach to determine the input voltage value of each cell in a cascade H-bridge multilevel inverter using a sensor at the output of the inverter to eliminate all the dc voltage sensors measuring the individual source voltages. The input voltages can be equal or unequal. The MOSFET device datasheet, the ambient temperature, and the modulation strategy are utilized to estimate the switch voltage drop to compensate for the measurement. The output voltage is then processed by a DSP unit that uses the signals that command the switches to estimate the voltage at each cell. Simulation and experimental results are shown for a seven-level cascade multilevel inverter operating under a RLC load.

  • Mithat C. Kisacikoglu; Burak Ozpineci; Leon M. Tolbert
    2010 IEEE Energy Conversion Congress and Exposition
    2010

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    Electric vehicles (EVs) and plug-in hybrid electric vehicles (PHEVs) are becoming a part of the electric grid day by day. Chargers for these vehicles have the ability to make this interaction better for the consumer and for the grid. Vehicle to grid (V2G) power transfer has been under research for more than a decade because of the large energy reserve of an electric vehicle battery and the potential of thousands of these connected to the grid. Rather than discharging the vehicle batteries, reactive power compensation in particular is beneficial for both consumers and for the utility. However, certain adverse effects or requirements of reactive power transfer should be defined before a design stage. To understand the dynamics of this operation, this study investigates the effect of reactive power transfer on the charger system components, especially on the dc-link capacitor and the battery.

  • Faete Filho; Leon M. Tolbert; Yue Cao; Burak Ozpineci
    2010 IEEE Energy Conversion Congress and Exposition
    2010

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    This work approximates the selective harmonic elimination problem using Artificial Neural Networks (ANN) to generate the switching angles in an 11-level full bridge cascade inverter powered by five varying DC input sources. Five 195 W solar panels were used as the DC source for each full bridge. The angles were chosen such that the fundamental was kept constant and the low order harmonics were minimized or eliminated. A non-deterministic method is used to solve the system for the angles and to obtain the data set for the ANN training. The method also provides a set of acceptable solutions in the space where solutions do not exist by analytical methods. The trained ANN shows to be a suitable tool that brings a small generalization effect on the angles' precision.

  • M. Chinthavali; L. M. Tolbert; H. Zhang; J. H. Han; F. Barlow; B. Ozpineci
    The 2010 International Power Electronics Conference - ECCE ASIA -
    2010

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    With efforts to reduce the cost, size, and thermal management systems for the power electronics drivetrain in hybrid electric vehicles (HEVs) and plug-in hybrid electric vehicles (PHEVs), wide band gap semiconductors including silicon carbide (SiC) have been identified as possibly being a partial solution. Research on SiC power electronics has shown their higher efficiency compared to Si power electronics due to significantly lower conduction and switching losses. This paper focuses on the development of a high power module based on SiC JFETs and Schottky diodes. Characterization of a single device, a module developed using the same device, and finally an inverter built using the modules is presented. When tested at moderate load levels compared to the inverter rating, an efficiency of 98.2% was achieved by the initial prototype.

  • Mithat C. Kisacikoglu; Burak Ozpineci; Leon M. Tolbert
    2010 Twenty-Fifth Annual IEEE Applied Power Electronics Conference and Exposition (APEC)
    2010

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    Plug-in hybrid electric vehicles (PHEVs) potentially have the capability to fulfill the energy storage needs of the electric grid by supplying ancillary services such as reactive power compensation, voltage regulation, and peak shaving. However, in order to allow bidirectional power transfer, the PHEV battery charger should be designed to manage such capability. While many different battery chargers have been available since the inception of the first electric vehicles (EVs), on-board, conductive chargers with bidirectional power transfer capability have recently drawn attention due to their inherent advantages in charging accessibility, ease of use, and efficiency. In this paper, a reactive power compensation case study using just the inverter dc-link capacitor is evaluated when a PHEV battery is under charging operation. Finally, the impact of providing these services on the batteries is also explained.

  • Renewable energy sources and plug-in hybrid electric vehicles (PHEVs) are becoming very popular in research areas, as well as in the market. The aim of this paper is to demonstrate how a solar powered building interacts with energy storage and how it can be used to power a PHEV and to support the grid with peak shaving, load shifting, and reducing annual energy usage. A net zero energy house (ZEH5) is selected as the base house for this experiment. Oak Ridge National Laboratory (ORNL) is developing simulation models and energy management scenarios using the actual solar production and residential energy usage data, and a PHEV. The system interaction with the grid is evaluated after getting all the data from PHEV charging, photovoltaic (PV) power production, and residential load.

  • M. Chinthavali; P. Otaduy; B. Ozpineci
    2010 IEEE Energy Conversion Congress and Exposition
    2010

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    In this paper a comparison of performance of an hybrid electric vehicle with an all-silicon (Si), hybrid (Si and SiC), and an all-Silicon Carbide (SiC) inverters simulated for the standard US06 driving cycle is presented. The system model includes a motor/generator model, a boost converter model, and an inverter loss model developed using actual measured data. The drive train simulation results will provide an insight to the impact of SiC devices on overall system efficiency gains compared to Si devices over the drive cycle at different operating conditions.

  • Madhu Chinthavali; Hui Zhang; Leon M. Tolbert; Burak Ozpineci
    2009 Brazilian Power Electronics Conference
    2009

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    This paper presents a study of silicon carbide (SiC) technology which includes device characterization and modeling, inverter simulation, and test results for several prototype inverters. The static and dynamic characteristics of discrete devices and half bridge modules are presented. Test results of a 55 kW hybrid inverter with SiC Schottky diodes and an 18 kW all-SiC inverter using SiC JFETs and Schottky diodes are demonstrated.

  • John N. Chiasson; Zhong Du; Burak Özpineci; Leon M. Tolbert
    Proceedings of the 48h IEEE Conference on Decision and Control (CDC) held jointly with 2009 28th Chinese Control Conference
    2009

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    A cascade multilevel inverter consisting of a standard 3-leg inverter supplied by a DC source and three full H-bridges each supplied by a capacitor is considered for use as a motor drive. The capacitor H-bridges can only supply reactive voltage to the motor while the standard three leg inverter can supply both reactive and active voltage. A switching control algorithm is presented that shows this inverter topology can be used as an AC drive achieving considerable performance advantages (e.g., higher motor speed) compared to using a standard 3-leg inverter while at the same time regulating the capacitor voltages. The converter controller is a fundamental frequency switching controller based on programmed PWM to achieve higher efficiency (less power losses in the switches) compared to high-frequency PWM approaches. As is well known, the programmed PWM switching times are computed assuming the drive is in sinusoidal steady-state, that is, the derived switching angles achieve the fundamental while rejecting specified harmonics if the voltage waveforms are in sinusoidal steady-state. Here it shown that the switching commands to the converter can be implemented in a smooth fashion for voltage waveform commands whose frequency and amplitudes are continuously varying.

  • Shengnan Li; Burak Ozpineci; Leon M. Tolbert
    2009 IEEE Energy Conversion Congress and Exposition
    2009

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    In hybrid electric vehicles (HEV), a battery-powered three-phase inverter is used to drive the traction motor. Due to the switching behavior of this inverter, significant harmonic currents are present on the DC side of the inverter. Traditionally, a bulky capacitor is used to filter these harmonics. In this paper, an active filtering method is evaluated to substitute for the DC bus capacitor. The active power filter (APF), composed of power electronic switches and an inductor, works as a current-source inverter. The operation principle of the proposed method is described and implemented in Matlab/Simulink. The method has been proposed before but the practical feasibility of this method has not been evaluated. In this paper, several crucial design parameters in association with the filtering effect, such as voltage band and the values of the inductor and the smoothing capacitor are identified, and the dependence of system performance on these parameters is illustrated. Finally, the underlying problems for practical implementation are discussed.

  • E. Ozdemir; S. Ozdemir; L. M. Tolbert; B. Ozpineci
    2008 Twenty-Third Annual IEEE Applied Power Electronics Conference and Exposition
    2008

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    This paper presents a fundamental frequency modulated multilevel inverter scheme for use with a three-phase stand-alone photovoltaic (PV) system. The system consists of four series connected PV arrays, a five-level diode-clamped multilevel inverter (DCMLI) generating fundamental modulation staircase three-phase output voltages, and a three-phase induction motor as the load. In order to validate the proposed concept, simulation studies and experimental measurements, done using a small-scale laboratory prototype, are also presented. The results show the feasibility of the fundamental switching application in three- phase stand-alone PV power systems.

  • Haiwen Liu; Leon M. Tolbert; Burak Ozpineci; Zhong Du
    2008 51st Midwest Symposium on Circuits and Systems
    2008

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    A hybrid multilevel inverter model based on PSIM and MATLAB/SIMULINK is presented in this paper. It consists of a standard 3-leg inverter (one leg for each phase) and H-bridge in series with each inverter leg. The inverter can be used in hybrid electric vehicles (HEV) and electric vehicles (EV). The co-simulation model is employed in order to take full advantage of different power electronics simulation software. Specifically, the main circuit model is developed using PSIM, and the control model is developed using MATLAB/SIMULINK. An experimental 5-level hybrid inverter is tested, which is controlled by multilevel carrier-based PWM signals. The simulation yields a good estimation for the test results of the inverter.

  • F. J. T. Filho; T. H. A. Mateus; H. Z. Maia; B. Ozpineci; J. O. P. Pinto; L. M. Tolbert
    2008 IEEE Power Electronics Specialists Conference
    2008

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    A new approach for selective harmonic elimination in a 7-level cascaded multilevel inverter with separate DC sources will be presented. As opposed to previous research in this area, the DC sources feeding the multilevel inverter are considered to be varying in time. This method uses genetic algorithms to obtain switching angles offline for different DC source values and uses neural networks to determine the switching angles that correspond to the real-time values of the DC sources. This implies that each one of the DC sources of this topology can have different values at any time but the output fundamental voltage will stay constant and the harmonic will still meet the specifications. The paper gives details on the approach used, together with simulation and experimental results.

  • Michael Starke; Leon M. Tolbert; Burak Ozpineci
    2008 IEEE/PES Transmission and Distribution Conference and Exposition
    2008

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    Environmentally friendly technologies such as photovoltaics and fuel cells are DC sources. In the current power infrastructure, this necessitates converting the power supplied by these devices into AC for transmission and distribution which adds losses and complexity. The amount of DC loads in our buildings is ever-increasing with computers, monitors, and other electronics entering our workplaces and homes. This forces another conversion of the AC power to DC, adding further losses and complexity. This paper proposes the use of a DC distribution system. In this study, an equivalent AC and DC distribution system are compared in terms of efficiency.

  • Michael Starke; Fangxing Li; Leon M. Tolbert; Burak Ozpineci
    2008 IEEE Power and Energy Society General Meeting - Conversion and Delivery of Electrical Energy in the 21st Century
    2008

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    Many studies comparing AC and DC systems have focused on efficiency, stability, and controllability, but have not compared the maximum transfer capability. In this paper, the maximum transfer capability of an AC system and two DC systems, one with two lines and another with three, is determined through the continuation power flow method and compared. The results reveal that significant gains can be achieved by moving to a DC system with three lines.

  • Haiwen Liu; Leon M. Tolbert; Surin Khomfoi; Burak Ozpineci; Zhong Du
    2008 IEEE Power Electronics Specialists Conference
    2008

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    A hybrid cascaded multilevel inverter with PWM method is presented in this paper. It consists of a standard 3-leg inverter (one leg for each phase) and H-bridge in series with each inverter leg. It can use only a single DC power source to supply a standard 3-leg inverter along with three full H-bridges supplied by capacitors. Multilevel carrier- based PWM method is used to produce a five-level phase voltage. The inverter can be used in hybrid electric vehicles (HEV) and electric vehicles (EV). A simulation model based on PSIM and MATLAB/SIMULINK is developed. An experimental 5 kW prototype inverter is built and tested. The results experimentally validate the proposed PWM hybrid cascaded multilevel inverter.

  • Haiwen Liu; Leon M. Tolbert; Burak Ozpineci; Zhong Du
    2008 34th Annual Conference of IEEE Industrial Electronics
    2008

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    This paper presents a hybrid cascaded multilevel inverter for electric vehicles (EV) / hybrid electric vehicles (HEV) and utility interface applications. The inverter consists of a standard 3-leg inverter (one leg for each phase) and H-bridge in series with each inverter leg. It can use only a single DC power source to supply a standard 3-leg inverter along with three full H-bridges supplied by capacitors or batteries. Both fundamental frequency and high switching frequency PWM methods are used for the hybrid multilevel inverter. An experimental 5 kW prototype inverter is built and tested. The above two switching control methods are validated and compared experimentally.

  • John Chiasson; Burak Ozpineci; Zhong Du; Leon M. Tolbert
    2007 IEEE International Electric Machines & Drives Conference
    2007

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    A cascade multilevel inverter is a power electronic device built to synthesize a desired AC voltage from several levels of DC voltages. Such inverters have been the subject of research in the last several years, where the DC levels were considered to be identical in that all of them were either batteries, solar cells, etc. Similar to previous results in the literature, the work here shows how a cascade multilevel inverter can be used to obtain a voltage boost at higher speeds for a three-phase PM drive using only a single DC voltage source. The input of a standard three-leg inverter is connected to the DC source and the output of each leg is fed through an H-bridge (which is supplied by a capacitor) to form a cascade multilevel inverter. A fundamental switching scheme is used, which achieves the fundamental in the output voltage while eliminating the fifth harmonic. A new contribution in this paper is the development of explicit conditions in terms of the power factor and modulation index for which the capacitor voltage of the H-bridges can be regulated while simultaneously maintaining the aforementioned output voltage. This is then used for a PM motor drive showing the machine can attain higher speeds due to the higher output voltage of the multilevel inverter compared to using just a three-leg inverter.

  • John N. Chiasson; Burak Ozpineci; Leon M. Tolbert
    APEC 07 - Twenty-Second Annual IEEE Applied Power Electronics Conference and Exposition
    2007

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    The interest here is in using a single DC power source to construct a 3-phase 5-level cascade multilevel inverter to be used as a drive for a PM traction motor. The 5-level inverter consists of a standard 3-leg inverter (one leg for each phase) and an H-bridge in series with each inverter leg, which use a capacitor as a DC source. It is shown that one can simultaneously maintain the regulation of the capacitor voltage while achieving an output voltage waveform which is 25% higher than that obtained using a standard 3-leg inverter by itself.

  • Zhong Du; Burak Ozpineci; Leon M. Tolbert; John N. Chiasson
    2007 IEEE Industry Applications Annual Meeting
    2007

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    This paper presents an inductorless cascaded H- bridge multilevel boost inverter for EV and HEV applications. Currently available power inverter systems for HEVs use a DC- DC boost converter to boost the battery voltage for a traditional 3-phase inverter. The present HEV traction drive inverters have low power density, are expensive, and have low efficiency because they need a bulky inductor. An inductorless cascaded H-bridge multilevel boost inverter for EV and HEV applications is proposed in this paper. Traditionally, each H-bridge needs a DC power supply. The proposed inductorless cascaded H-bridge multilevel boost inverter uses a standard 3-leg inverter (one leg for each phase) and an H-bridge in series with each inverter leg which uses a capacitor as the DC power source. Fundamental switching scheme is used to do modulation control and to produce a 5-level phase voltage. Experiments show that the proposed inductorless DC-AC cascaded H-bridge multilevel boost inverter can output a boosted AC voltage.

  • Zhong Du; Burak Ozpineci; Leon M. Tolbert
    2007 IEEE Power Electronics Specialists Conference
    2007

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    This paper presents a modulation extension control algorithm for hybrid cascaded H-bridge multilevel converters. The hybrid cascaded H-bridge multilevel motor drive using only a single DC source for each phase is promising for high power motor drive applications since it can greatly decrease the number of required DC power supplies, has high quality output power due to its high number of output levels, and has high conversion efficiency and low thermal stress by using fundamental frequency switching scheme. But one disadvantage of the 7-level fundamental frequency switching scheme is that its modulation index range is too narrow when capacitor's voltage balance is maintained. The proposed modulation extension control algorithm can greatly increase capacitors' charging time and decrease the capacitors' discharging time by injecting triplen harmonics to extend the modulation index range of the hybrid cascaded H-bridge multilevel converters.

  • Surin Khomfoi; Leon M. Tolbertt; Burak Ozpineci
    2007 IEEE International Electric Machines & Drives Conference
    2007

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    The ability of cascaded H-bridge multilevel inverter drives (MLID) to operate under faulty condition including AI-based fault diagnosis and reconfiguration system is proposed in this paper. Output phase voltages of a MLID can be used as valuable information to diagnose faults and their locations. It is difficult to diagnose a MLID system using a mathematical model because MLID systems consist of many switching devices and their system complexity has a nonlinear factor. Therefore, a neural network (NN) classification is applied to the fault diagnosis of a MLID system. Multilayer perceptron (MLP) networks are used to identify the type and location of occurring faults. The principal component analysis (PCA) is utilized in the feature extraction process to reduce the NN input size. A lower dimensional input space will also usually reduce the time necessary to train a NN, and the reduced noise may improve the mapping performance. The genetic algorithm (GA) is also applied to select the valuable principal components to train the NN. A reconfiguration technique is also proposed. The proposed system is validated with simulation and experimental results. The proposed fault diagnostic system requires about 6 cycles (~100 ms at 60 Hz) to clear an open circuit and about 9 cycles (~150 ms at 60 Hz) to clear a short circuit fault. The experiment and simulation results are in good agreement with each other, and the results show that the proposed system performs satisfactorily to detect the fault type, fault location, and reconfiguration.

  • L. Galotto; J. O. P. Pinto; B. Ozpineci; L. C. Leite; L. E. S. Borges
    2007 IEEE International Electric Machines & Drives Conference
    2007

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    Sensors are essential in feedback control systems, because the performance is dependent on the measurements. Fault in sensors may lead to intolerable degradation of performance and even to instability. Therefore, the high performance expected with vector control may not be achieved with fault in sensors. Several approaches related to fault tolerant motor control have already been proposed. However, most of them consider the sensors fault-free and work about faults in motors and actuators. Furthermore, the purpose of this work is not only sensor fault tolerance but also sensor fault compensation. In a standard fault tolerant approach, the fault would be detected and the sensor would be isolated. The faulted sensor may have an off-set or scaling error and could still be used if its error is compensated. In this paper, this is done with a mathematical solution based on kernel regression that can compensate the measurement error generating more accurate and reliable estimates. This technique is described and applied in motor drives. Simulated and experimental results are presented and discussed.

  • Zhong Du; L.M. Tolbert; J.N. Chiasson; B. Ozpineci
    Twenty-First Annual IEEE Applied Power Electronics Conference and Exposition, 2006. APEC '06.
    2006

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    A method is presented showing that a cascade multilevel inverter can be implemented using only a single DC power source and capacitors. A standard cascade multilevel inverter requires n DC sources for 2n + 1 levels. Without requiring transformers, the scheme proposed here allows the use of a single DC power source (e.g., a battery or a fuel cell stack) with the remaining n-1 DC sources being capacitors. It is shown that one can simultaneously maintain the DC voltage level of the capacitors and choose a fundamental frequency switching pattern to produce a nearly sinusoidal output.

  • Hui Zhang; Leon M. Tolbert; Burak Ozpineci; Madhu S. Chinthavali
    Conference Record of the 2006 IEEE Industry Applications Conference Forty-First IAS Annual Meeting
    2006

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    The purpose of this work is to provide validated models to estimate the performance of a SiC-based converter as a utility interface in battery systems. System design and modeling are described in detail. Simulations are done for both a SiC JFET converter and its Si counterpart based on the quality of tested devices. The simulation results indicate that in both charging and discharging modes, the SiC converter has a better performance compared to the Si one. (1) With the same heatsink size and ambient temperature, great advantages in efficiency and junction temperatures were found in the SiC-based converter. (2) With the same thermal limit, large savings in system weight and volume combined with a high efficiency were found in the SiC-based converter

  • B. Ozpineci; M.S. Chinthavali; L.M. Tolbert; A. Kashyap; H.A. Mantooth
    Twenty-First Annual IEEE Applied Power Electronics Conference and Exposition, 2006. APEC '06.
    2006

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    Silicon carbide (SiC) power devices are expected to have an impact on power converter efficiency, weight, volume, and reliability. Presently, only SiC Schottky diodes are commercially available at relatively low current ratings. Oak Ridge National Laboratory has collaborated with Cree and Semikron to build a Si IGBT-SiC Schottky diode hybrid 55kW inverter by replacing the Si pn diodes in Semikron's automotive inverter with Cree's made-to-order higher current SiC Schottky diodes. This paper presents the developed models of these diodes for circuit simulators, shows inverter test results, and compares the results to those of a similar all-Si inverter.

  • Hui Zhang; Leon M. Tolbert; Burak Ozpineci
    2006 IEEE Workshops on Computers in Power Electronics
    2006

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    Most of the present models of silicon carbide (SiC) Schottky diodes are not suitable for evaluating their performance from a system level. The models presented in this paper are specialized for system-level simulations. They are based on basic semiconductor theories and synthesis of some models in the literature. Theoretical and experimental characterization of SiC Schottky power diodes is also involved. The models describe both static and dynamic behaviors of SiC Schottky power diodes. Thermal effects are considered as well for a better evaluation of power losses evaluation and cooling system design. The models were also used to estimate the efficiencies of Si IGBT/SiC Schottky diode hybrid inverter. To validate the simulation, a Si IGBT/SiC Schottky diode hybrid inverter and a Si IGBT inverter were built and tested

  • Zhong Du; Leon M. Tolbert; John N. Chiasson; Burak Ozpineci; Hui Li; Alex Q. Huang
    2006 37th IEEE Power Electronics Specialists Conference
    2006

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    This paper presents a hybrid cascaded H-bridge multilevel motor drive control scheme for electric/hybrid electric vehicles where each phase of a three-phase cascaded multilevel converter can be implemented using only a single DC source and capacitors for the other DC sources. Traditionally, each phase of a three-phase cascaded multilevel converter requires n DC sources for 2n + 1 output voltage levels. In this paper, a scheme is proposed that allows the use of a single DC source as the first DC source with the remaining n − 1 DC sources being capacitors. It is shown that a simple 7-level equal step output voltage switching control can simultaneously maintain the balance of DC voltage levels of the capacitors, eliminate specified low order non-triplen harmonics, and produce a nearly sinusoidal three-phase output voltage. This scheme therefore provides the capability to produce higher voltages at higher speeds (where they are needed) with a low switching frequency method for motor drive application, which has inherent low switching losses and high conversion efficiency. This control scheme especially fits fuel cell electric vehicle motor drive applications and hybrid electric vehicle motor drive applications.

  • B. Ozpineci; M.S. Chinthavali; L.M. Tolbert
    2005 IEEE Vehicle Power and Propulsion Conference
    2005

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    Silicon carbide (SiC) power devices are expected to have an impact on power converter efficiency, weight, volume, and reliability. Presently, only SiC Schottky diodes are commercially available at relatively low current ratings. Oak Ridge National Laboratory has collaborated with Cree and Semikron to build a Si IGBT-SiC Schottky diode hybrid 55 kW inverter by replacing the Si pn diodes in Semikron's automotive inverter with Cree's made-to-order higher current SiC Schottky diodes. This paper shows the results obtained from testing this inverter and compares it to a similar all-Si inverter.

  • H. Zhang; L.M. Tolbert; B. Ozpineci; M.S. Chinthavali
    Fourtieth IAS Annual Meeting. Conference Record of the 2005 Industry Applications Conference, 2005.
    2005

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    This paper presents a set of models for a SiC VJFET inverter from device level to system level. The simulations for SiC and Si inverters indicated that the SiC inverter has a much lower junction temperature, much less power loss, significantly enhanced energy efficiency, and a dramatic reduction in heatsink size as compared with the Si inverter. This demonstrated the technical feasibility and benefits of the all-SiC inverter. In addition to the simulations, experimental tests have also been conducted on SiC VJFETs and Schottky diodes for parameter extraction.

  • M.S. Chinthavali; B. Ozpineci; L.M. Tolbert
    Twentieth Annual IEEE Applied Power Electronics Conference and Exposition, 2005. APEC 2005.
    2005

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    Silicon carbide (SiC) unipolar devices have much higher breakdown voltages because of the ten times greater electric field strength of SiC compared with silicon (Si). 4H-SiC unipolar devices have higher switching speeds due to the higher bulk mobility of 4H-SiC compared to other polytypes. Four commercially available SiC Schottky diodes at different voltage and current ratings, an experimental VJFET, and MOSFET samples have been tested to characterize their performance at different temperatures. Their forward characteristics and switching characteristics in a temperature range of -50degC to 175degC are presented. The results of the SiC Schottky diodes are compared with those of a Si pn diode with comparable ratings

  • J.B. Campbell; L.M. Tolbert; C.W. Ayers; B. Ozpineci
    Twentieth Annual IEEE Applied Power Electronics Conference and Exposition, 2005. APEC 2005.
    2005

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    This paper presents a two-phase cooling method using R134a refrigerant to dissipate the heat energy (loss) generated by power electronics (PE) such as those associated with rectifiers, converters, and inverters for a specific application in hybrid-electric vehicles (HEVs). The cooling method involves submerging PE devices in an R134a bath, which limits the junction temperature of PE devices while conserving weight and volume of the heat sink without sacrificing equipment reliability. First, experimental tests that included an extended soak for more than 300 days were performed on a submerged IGBT and gate-controller card to study dielectric characteristics, deterioration effects, and heat flux capability of R134a. Results from these tests illustrate that R134a has high dielectric characteristics, no deterioration on electrical components, and a heat flux of 114 W/cm 2 for the experimental configuration. Second, experimental tests that included simultaneous operation with a mock automotive air-conditioner (A/C) system were performed on the same IGBT and gate controller card. Data extrapolation from these tests determined that a typical automotive A/C system has more than sufficient cooling capacity to cool a typical 30 kW traction inverter. Last, a discussion and simulation of active cooling of the IGBT junction layer with R134a refrigerant is given. This technique will drastically increase the forward current ratings and reliability of the PE device

  • J.M. Bailey; B. Ozpineci; G.W. Ott; D.S. Daniel
    IEEE International Conference on Electric Machines and Drives, 2005.
    2005

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    Axial-gap permanent magnet synchronous motors (AGPMSM) with disc magnets have been presented as a viable candidate for high speed traction drive applications in electric or hybrid electric vehicles. In this paper, back emf equation for an AGPMSM is derived and it is overlapped with the measured back emf for verification purposes

  • M. Chinthavali; L.M. Tolbert; B. Ozpineci
    IEEE Power Engineering Society General Meeting, 2004.
    2004

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    The development of semiconductor devices is vital for the growth of power electronic systems. Modern technologies like voltage source converter (VSC) based HVDC transmission has been made possible with the advent of power semiconductor devices like GTO thyristors and their high power handling capability. Silicon carbide is the most advanced material among the available wide band gap semiconductors and most SiC devices are currently in the transition from research to manufacturing phase. This paper presents the modeling and design of a loss model for a 4H-SiC GTO thyristor device. The device loss model has been developed based on the device physics and device operation, and simulations have been conducted for various operating conditions. The loss model was integrated in the HVDC transmission system model to study the effects of the Si and SiC devices on the system. The paper focuses on the comparison of Si devices with SiC devices in terms of efficiency and cost savings for a HVDC transmission system.

  • M.S. Chinthavali; L.M. Tolbert; B. Ozpineci
    Conference Record of the 2004 IEEE Industry Applications Conference, 2004. 39th IAS Annual Meeting.
    2004

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    The increase in use of power electronics in transmission and distribution applications is the driving force for development of high power devices. Utility applications like FACTS and HVDC require cost effective and highly efficient converters with high power ratings. SiC power devices have some exceptional physical properties that make them highly reliable at high power, high temperature, and high frequencies. This paper presents the modeling of temperature dependent 4H-SiC GTO thyristor and p-n diode loss models. The conduction and switching losses of the devices for various operating conditions have been simulated and compared for SiC and Si devices. These loss models are integrated with an HVDC transmission system to study the effect of Si and SiC devices on the system in terms of system efficiency and system cost management.

  • B. Ozpineci; L.M. Tolbert; Zhong Du
    Conference Record of the 2004 IEEE Industry Applications Conference, 2004. 39th IAS Annual Meeting.
    2004

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    Multilevel converters have been used previously to integrate several fuel cell modules for higher power applications. Some previous publications have also shown improvements in fuel cell utilization by exploiting the static characteristics of fuel cells, which show more than a 30% difference in the output voltage between no-load to full-load conditions. This paper first describes standard fuel cell power electronics interfaces, then reviews a few of the multi input systems and explores additional configurations.

  • M.S. Chinthavali; B. Ozpineci; L.M. Tolbert
    Power Electronics in Transportation (IEEE Cat. No.04TH8756)
    2004

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    Silicon (Si) unipolar devices are limited in breakdown voltages because of the low electric field strength of the material. Silicon carbide (SiC) unipolar devices, on the other hand, have 10 times greater electric field strength and hence they have much higher breakdown voltages compared with Si. They also have low static and dynamic losses compared with Si devices. Four commercially available SiC Schottky diodes at different voltage and current ratings and an experimental SiC VJFET sample have been tested to characterize their performance at different temperatures. Their forward characteristics and switching characteristics in a temperature range of -50 /spl deg/C to 175 /spl deg/C are presented. The results for the SiC Schottky diodes are compared with the results for a Si pn diode with comparable ratings. The experimental data were analyzed to obtain the device performance parameters like the on-state resistance and the switching losses.

  • B. Ozpineci; L.M. Tolbert; G.-J. Su; Z. Du
    Nineteenth Annual IEEE Applied Power Electronics Conference and Exposition, 2004. APEC '04.
    2004

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    Static characteristics of fuel cells show more than a 30% difference in the output voltage between no-load to full-load conditions. This inevitable decrease, which is caused by internal losses, reduces the utilization factor of the fuel cells at low loads. Additionally, the converters fed by these fuel cells have to be derated to accommodate higher input voltages at low currents. To increase the utilization of fuel cells and to avoid derating of semiconductors, this paper proposes a level reduction control using a multilevel DC-DC converter. Level reduction is done by inhibiting a certain number of fuel cells when the load current decreases. The inhibited fuel cells can be used in other applications such as charging batteries to further increase their utilization and the efficiency of the system.

  • B. Ozpineci; L.M. Tolbert; Zhong Du
    2004 IEEE 35th Annual Power Electronics Specialists Conference (IEEE Cat. No.04CH37551)
    2004

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    Static characteristics of fuel cells show more than a 30% difference in the output voltage between no-load to full-load conditions. This inevitable decrease, which is caused by internal losses, reduces the utilization factor of the fuel cells at low loads. Additionally, the converters fed by these fuel cells have to be derated to accommodate higher input voltages at low currents. To increase the utilization of fuel cells and to avoid derating of semiconductors, this paper proposes a level reduction control using a multilevel inverter. Level reduction is done by inhibiting a certain number of fuel cells when the load current decreases. The inhibited fuel cells can be used in other applications such as charging batteries to further increase their utilization and the efficiency of the system.

  • B. Ozpineci; L.M. Tolbert
    IEEE International Electric Machines and Drives Conference, 2003. IEMDC'03.
    2003

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    In this paper, a modular Simulink implementation of an induction machine model is described in a step-by-step approach. With the modular system, each block solves one of the model equations; therefore, unlike black box models, all of the machine parameters are accessible for control and verification purposes. After the implementation, examples are given with the model used in different drive applications, such as open-loop constant V/Hz control and indirect vector control are given. Finally, the use of the model as an Induction generator is demonstrated.

  • B. Ozpineci; Zhong Du; L.M. Tolbert; D.J. Adams; D. Collins
    IECON'03. 29th Annual Conference of the IEEE Industrial Electronics Society (IEEE Cat. No.03CH37468)
    2003

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    According to SECA program guidelines, solid oxide fuel cells (SOFC) are produced in the form of 3-10 kW modules for residential use. In addition to residential use, these modules can also be used in apartment buildings, hospitals, etc., where a higher power rating would be required. For example, a hospital might require a 250 kW power supply. To provide this power using the SOFC modules, 25 of the 10 kW modules would be required. These modules can be integrated in different configurations to yield the necessary power. This paper shows five different approaches for integrating numerous SOFC modules and will evaluate and compare each one with respect to cost, control complexity, ease of modularity, and fault tolerance.

  • B. Ozpinecil; L.M. Tolbert; S.K. Islam
    Power Electronics in Transportation, 2002
    2002

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    The emergence of silicon carbide- (SiC-) based power semiconductor switches, with their superior features compared with silicon- (Si-) based switches, has resulted in substantial improvement in the performance of power electronics converter systems. These systems with SiC power devices have the qualities of being more compact, lighter, and more efficient; thus, they are ideal for high-voltage power electronics applications such as a hybrid electric vehicle (HEV) traction drive. More research is required to show the impact of SIC devices in power conversion systems. In this study, findings of SIC research at Oak Ridge National Laboratory (OWL), TN, USA, including SIC device design and system modeling studies, are discussed.

  • B. Ozpineci; L.M. Tolbert; S.K. Islam; F.Z. Peng
    2002 IEEE 33rd Annual IEEE Power Electronics Specialists Conference. Proceedings (Cat. No.02CH37289)
    2002

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    The emergence of silicon carbide- (SiC-) based power semiconductor switches, with their superior features compared with silicon- (Si-) based switches, has resulted in substantial improvement in the performance of power electronics converter systems. These systems with SiC power devices have the qualities of being more compact, lighter and more efficient; thus, they are ideal for high-voltage power electronics applications such as a hybrid electric vehicle (HEV) traction drive. More research is required to show the impact of SiC devices in power conversion systems. In this study, findings of SiC research at Oak Ridge National Laboratory (ORNL), including SiC device design and system modeling studies, are discussed.

  • B. Ozpineci; L.M. Tolbert; S.K. Islam; M. Hasanuzzaman
    Conference Record of the 2002 IEEE Industry Applications Conference. 37th IAS Annual Meeting (Cat. No.02CH37344)
    2002

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    Materials and device researchers build switching devices for the circuits researchers to use in their circuits, but they rarely know how and where the devices are going to be used. The circuits people, including power electronics researchers, take the devices as black boxes and use them in their circuits not knowing much about the inside of the devices. The best way to design optimum devices is an interactive design where people designing and building the devices have a close interaction with the people who use them. This study covers the circuit aspects of the SiC power device development. As a contribution to the above-mentioned interactive design, in this paper, the device parameters, which need to be improved in order to design better devices, are discussed.

  • B. Ozpineci; L.M. Tolbert; S.K. Islam; T.J. Theiss
    Proceedings IEEE 56th Vehicular Technology Conference
    2002

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    Materials and device researchers build switching devices for the circuit researchers to use in their circuits, but they rarely know how and where the devices are going to be used. The circuits people, including power electronics researchers, take the devices as black boxes and use them in their circuits not knowing much about the inside of the devices. The best way to design optimum devices is an interactive design where people designing and building the devices have a close interaction with the people who use them. This study covers the circuit aspects of the SiC power device development. As a contribution to the abovementioned interactive design, in this paper, the device parameters, which need to be improved in order to design better devices, are discussed.

  • B. Ozpineci; L.M. Tolbert; S.K. Islam; M. Hasanuzzaman
    IECON'01. 27th Annual Conference of the IEEE Industrial Electronics Society (Cat. No.37243)
    2001

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    The emergence of silicon carbide (SiC) based power semiconductor switches with their superior features compared with silicon (Si) based switches has resulted in substantial improvements in the performance of power electronics converter systems. These systems with SiC power devices are more compact, lighter, and more efficient, so they are ideal for high-voltage power electronics applications, including hybrid electric vehicle (HEV) traction drives. In this paper, the effect of SiC-based power devices on HEV traction drive losses are investigated. Reductions in heat sink size and device losses with the increase in the efficiency will be analyzed using an averaging model of a three-phase PWM inverter (TPPWMI). For more accurate results, device physics is taken into consideration to find the loss equations for the controllable switches.

  • B. Ozpineci; J.O.P. Pinto; L.M. Tolbert
    2001 IEEE International Conference on Systems, Man and Cybernetics. e-Systems and e-Man for Cybernetics in Cyberspace (Cat.No.01CH37236)
    2001

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    As the size and the cost of power semiconductor switches are decreasing, converter topologies with high device count are starting to draw more attention. One such type of converter is the high frequency AC (HFAC) link converters. A popular control method for these converters is pulse density modulation (PDM). The HFAC link voltage of the converter in this paper is a high frequency, three-step, variable pulse-width (PW) square wave voltage waveform. A genetic algorithm approach is used to determine the PW to optimize the output voltage harmonic content.

  • B. Ozpineci; B.K. Bose
    IECON '98. Proceedings of the 24th Annual Conference of the IEEE Industrial Electronics Society (Cat. No.98CH36200)
    1998

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    High frequency link power conversion techniques are receiving a lot of attention in the literature. As the size and cost of traditional converters are shrinking, we are seeing the emergence of high frequency link power conversion with all its characteristic advantages. The paper describes a performance-enhanced high-frequency nonresonant link power conversion system where the input DC is converted to high frequency (20 to 50 kHz range) single-phase AC, and then converted to variable frequency variable voltage three-phase AC for driving an AC motor load. A lightweight ultra-low leakage inductance transformer in the high frequency link provides the advantages of isolation, voltage level boost in the secondary, and auxiliary power supplies. The scheme is particularly attractive for electric vehicle type applications. All the switches are soft-switched, and there is no voltage or current penalty of the devices. Although the number of components are somewhat higher, there are overall advantages of improved efficiency, power density and reliability in the total system, particularly when used with MCT-PEBB (power electronic building block) based modules. The system was analyzed thoroughly, designed, control strategy was developed, modelled for simulation, and then performance was evaluated. An experimental laboratory drive with 30 hp induction motor is being built and evaluated.

  • Li Hui; B. Ozpineci; B.K. Bose
    IECON '98. Proceedings of the 24th Annual Conference of the IEEE Industrial Electronics Society (Cat. No.98CH36200)
    1998

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    Soft-switched high frequency link power conversion has a number of attractive features, and for this reason, it is a favorite topic of R&D in the literature. The paper describes a high frequency nonresonant link soft-switched DC-AC converter for AC motor drive that operates on the principle of integral pulse modulation. A light-weight ultra-low leakage inductance transformer in the high frequency link provides the advantages of isolation, voltage level boost in the secondary, and auxiliary power supplies. All the devices in the converter are ideally soft-switched by zero voltage switching. In spite of additional components compared to traditional converters, the scheme has the overall advantages of good efficiency, good power density and improved reliability in the total system particularly when used with MCT-PEBB (power electronics building block) based modules. A complete converter system has been analyzed, designed, control strategy has been developed, modeled for simulation study, and performance has been evaluated with a four-quadrant vector-controlled 5 hp induction motor drive using the link frequency of 20 kHz. A laboratory test of 5 hp drive is in progress.