Burak Ozpineci
Office:  
Email: 
vog.lnro@karub 
Phone:  8659461329 
Fax:  8659461262 
Address:  Oak Ridge National Laboratory PO Box 2008 MS6472 Oak Ridge, TN 378316472 
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 PostMasters 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 systemlevel impact of SiC power devices, multilevel inverters, power converters for distributed energy resources and hybrid electric vehicles, and intelligent control applications for power converters.
Ongoing Research Projects
Publications
Journal Papers

IEEE Transactions on Industrial Electronics2017
arrow_drop_downSilicon 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.
[BibTeX] 
IEEE Transactions on Power Electronics2015
arrow_drop_downReliability 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.
[BibTeX] 
IEEE Transactions on Industry Applications2015
arrow_drop_downThis paper presents a modular cascaded Hbridge multilevel photovoltaic (PV) inverter for single or threephase gridconnected 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 threephase multilevel inverters, which allows independent control of each dclink voltage. For threephase gridconnected 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 threephase sevenlevel cascaded Hbridge inverter has been built utilizing nine Hbridge modules (three modules per phase). Each Hbridge module is connected to a 185W solar panel. Simulation and experimental results are presented to verify the feasibility of the proposed approach.
[BibTeX] 
IEEE Transactions on Power Delivery2015
arrow_drop_downThe concept of the magnetic amplifier, a common electromagnetic device in electronic applications in the past, has seldom been used in power systems. The magnetic amplifierbased powerflow controller (MAPFC), an innovative lowcost device that adopts the idea of the magnetic amplifier for powerflow 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 TennesseeKnoxville, and Waukesha Electric Systems, Inc. since early 2012. Findings from the project are presented along with some results obtained in a laboratory environment.
[BibTeX] 
IEEE Transactions on Industry Applications2015
arrow_drop_downRainflow 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 timedependent mean temperature calculation. The equivalent temperature calculation proposed by Nagode et al. is applied to semiconductor lifetime estimation in this paper. A monthlong arc furnace load profile is used as a test profile to estimate temperatures in insulatedgate 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 timedependent temperature calculation.
[BibTeX] 
IEEE Transactions on Power Electronics2013
arrow_drop_downThis paper presents a summary of the available singlephase acdc topologies used for EV/PHEV, level1 and 2 onboard charging and for providing reactive power support to the utility grid. It presents the design motives of singlephase onboard chargers in detail and makes a classification of the chargers based on their future vehicletogrid usage. The pros and cons of each different acdc topology are discussed to shed light on their suitability for reactive power support. This paper also presents and analyzes the differences between chargingonly operation and capacitive reactive power operation that results in increased demand from the dclink 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 dclink capacitor.
[BibTeX] 
IEEE Transactions on Industrial Electronics2013
arrow_drop_downA new approach for modulation of an 11level 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 realtime 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.
[BibTeX] 
IEEE Transactions on Industry Applications2011
arrow_drop_downThe application of silicon carbide (SiC) devices as battery interface, motor controller, etc., in a hybrid electric vehicle (HEV) will be beneficial due to their hightemperature capability, highpower 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 plugin HEV (PHEV), whose powertrain architecture is the same as that of the 2004 Toyota Prius HEV. The vehiclelevel 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.
[BibTeX] 
IEEE Spectrum2011
arrow_drop_downSilicon 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 siliconare 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 SiCbased 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.
[BibTeX] 
IEEE Transactions on Industry Applications2011
arrow_drop_downThis work approximates the selective harmonic elimination problem using artificial neural networks (ANNs) to generate the switching angles in an 11level fullbridge cascade inverter powered by five varying dc input sources. Each of the five full bridges of the cascade inverter was connected to a separate 195W solar panel. The angles were chosen such that the fundamental was kept constant and the loworder 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 (50/60Hz time window).
[BibTeX] 
IEEE Transactions on Industry Applications2009
arrow_drop_downSilicon 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 insulatedgate bipolar transistorSiC Schottky diode hybrid 55kW inverter by replacing the Si pn diodes in Semikron's automotive inverter with Cree's madetoorder 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 allSi inverter.
[BibTeX] 
IEEE Transactions on Power Electronics2009
arrow_drop_downThis paper presents a cascaded Hbridge 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 n1 dc sources being capacitors, which is referred to as hybrid cascaded Hbridge 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 highpower motor drive applications as it significantly decreases the number of required dc power supplies, provides highquality 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 sevenlevel HCMLI with fundamental frequency switching control and how its modulation index range can be extended using triplen harmonic compensation.
[BibTeX] 
IEEE Transactions on Industry Applications2009
arrow_drop_downThis paper presents a cascaded Hbridge 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 dcdc boost converter to boost the battery voltage for a traditional threephase 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 Hbridge multilevel boost inverter design for EV and HEV applications implemented without the use of inductors is proposed in this paper. Traditionally, each Hbridge needs a dc power supply. The proposed design uses a standard threeleg inverter (one leg for each phase) and an Hbridge 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 fivelevel phase voltage. Experiments show that the proposed dcac cascaded Hbridge multilevel boost inverter can output a boosted ac voltage without the use of inductors.
[BibTeX] 
IEEE Transactions on Industrial Electronics2008
arrow_drop_downThis paper presents a reduced switchingfrequency activeharmonicelimination method (RAHEM) to eliminate any number of specific order harmonics of multilevel converters. First, resultant theory is applied to transcendental equations to eliminate loworder harmonics and to determine switching angles for a fundamental frequencyswitching scheme. Next, based on the number of harmonics to be eliminated, Newton climbing method is applied to transcendental equations to eliminate highorder harmonics and to determine switching angles for the fundamental frequencyswitching 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 loworder harmonics. Compared to the activeharmonicelimination method (AHEM), which generates square waves to cancel highorder 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 11level Hbridge multilevel converter with a fieldprogrammable gatearray 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.
[BibTeX] 
IET Electric Power Applications2007
arrow_drop_downFuel 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 DCDC boost converters and inverters used for power conditioning of fuel cells. Several architectures to aggregate multiple fuel cells for highvoltage/highpower applications are also reviewed.
[BibTeX] 
IEEE Transactions on Industry Applications2007
arrow_drop_downThis paper presents a twophase 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 hybridelectric 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 gatecontroller card to study dielectric characteristics, deterioration effects, and heatflux 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 airconditioner (A/C) system were performed on the same IGBT and gatecontroller card. Data extrapolation from these tests determined that a typical automotive A/C system has more than sufficient cooling capacity to cool a typical 30kW 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
[BibTeX] 
IEEE Power Electronics Letters2005
arrow_drop_downIn 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 sevenlevel 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.
[BibTeX] 
IEEE Power Electronics Letters2003
arrow_drop_downThe 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 highvoltage 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.
[BibTeX]
Conference Papers

2018 IEEE Transportation Electrification Conference and Expo (ITEC)2018
arrow_drop_downEmerging widebandgap 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 twolevel 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 deadtime conduction loss analysis for the SiC MOSFETs in the segmented twolevel 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 torquespeed 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.
[BibTeX] 
2018 IEEE Transportation Electrification Conference and Expo (ITEC)2018
arrow_drop_downAutomated 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 failsafe 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.
[BibTeX] 
2018 IEEE Transportation Electrification Conference and Expo (ITEC)2018
arrow_drop_downThis 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 Sibased 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.
[BibTeX] 
2018 IEEE Transportation Electrification Conference and Expo (ITEC)2018
arrow_drop_downInductive 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 heavyduty vehicle can travel at or near chargesustaining 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 lightduty vehicles (LDVs) and still maintain chargesustaining operation of heavyduty 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.
[BibTeX] 
2018 IEEE Applied Power Electronics Conference and Exposition (APEC)2018
arrow_drop_downThe traditional heatsink design technologies for forced aircooling 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 liquidcooled 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 aircooled module assembly has a SiC MOSFET phase leg module with split highside and lowside switches and a gate driver with crosstalk and short circuit protection functions. The heatsink design was modeled using a cosimulation 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 50kW load. The experimental results show that the CEC efficiency is 98.4 %. In addition to the efficiency, a power density of 75 W/in^{3} was also achieved.
[BibTeX] 
2017 IEEE Transportation Electrification Conference and Expo (ITEC)2017
arrow_drop_downEnhancing 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 aircooled 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 aircooled heat sink are also included in the paper.
[BibTeX] 
2017 IEEE 26th International Symposium on Industrial Electronics (ISIE)2017
arrow_drop_downConventional 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%.
[BibTeX] 
2017 IEEE Transportation Electrification Conference and Expo (ITEC)2017
arrow_drop_downIn this paper, the effects of the resonant network characteristic and control variables on the dclink 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 dclink capacitance needed can be obtained to keep the dclink voltage ripple within a desired limit for a wide load range. A comparison between the conventional seriesprimary resonant networks in terms of the dclink capacitance needs is presented as well as simulation results to validate the derived equation.
[BibTeX] 
2016 IEEE Applied Power Electronics Conference and Exposition (APEC)2016
arrow_drop_downIn this paper, a genetic algorithm (GA) based approach is discussed for designing heat sinks based on total heat generation and dissipation for a prespecified 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.
[BibTeX] 
2016 International Symposium on 3D Power Electronics Integration and Manufacturing (3DPEIM)2016
arrow_drop_downThe thermal response of a liquidcooled, 3Dprinted aluminum heat sink is compared to that for a conventionallymanufactured aluminum 6061 heat sink of identical geometry. Differences in thermal response were observed; however, the employed 3Dprinted 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 3Dprinting can be exploited for heat exchangers with a simple and additional processing step.
[BibTeX] 
2016 IEEE Power and Energy Society General Meeting (PESGM)2016
arrow_drop_downTransmission 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 online robot design presents its own set of challenges. This paper proposes a touchfree 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 lineenclosing 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.
[BibTeX] 
2016 IEEE PELS Workshop on Emerging Technologies: Wireless Power Transfer (WoW)2016
arrow_drop_downDynamic 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 lightduty 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.
[BibTeX] 
2014 IEEE Workshop on Wide Bandgap Power Devices and Applications2014
arrow_drop_downWith efforts to reduce the cost, size, and thermal management systems for the power electronics drivetrain in hybrid electric vehicles (HEVs) and plugin 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 10kW 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.
[BibTeX] 
2014 IEEE Applied Power Electronics Conference and Exposition  APEC 20142014
arrow_drop_downLifetime estimation of power semiconductors for various applications has gained technical importance. The main failures in high power semiconductors are caused by thermomechanical 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.
[BibTeX] 
2014 IEEE Applied Power Electronics Conference and Exposition  APEC 20142014
arrow_drop_downRainflow 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.
[BibTeX] 
2014 IEEE Workshop on Wide Bandgap Power Devices and Applications2014
arrow_drop_downNormallyoff GaNonSi heterojunction fieldeffect transistors (HFETs) have been developed with up to 650 V blocking capability, fast switching, and low conduction losses in commercial devices. The natively depletionmode device can be modified to be normallyoff using a variety of techniques. For a power electronics engineer accustomed to Sibased converter design, there is inherent benefit to understanding the unique characteristics and challenges that distinguish GaN HFETs from Si MOSFETs. Dynamic R_{dson} selfcommutated 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 nearcommercial GaN HFETs, to prepare engineers with Sibased power electronics experience to effectively design GaNbased converters.
[BibTeX] 
2013 TwentyEighth Annual IEEE Applied Power Electronics Conference and Exposition (APEC)2013
arrow_drop_downA threephase modular cascaded Hbridge multilevel inverter for a gridconnected 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 dclink voltage. PV mismatches may introduce unbalanced power supplied to the threephase system. To solve this issue, a control scheme with modulation compensation is proposed. The threephase modular cascaded multilevel inverter prototype has been built. Each Hbridge is connected to a 185 W solar panel. Simulation and experimental results are presented to validate the proposed ideas.
[BibTeX] 
2013 IEEE Energy Conversion Congress and Exposition2013
arrow_drop_downAcac matrix converters and cycloconverters require bidirectional switches, which are typically formed by two antiparallel thyristors or a twoswitch (IGBT/MOSFETs) twodiode 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 normallyon SiC JFETs in antiseries with no antiparallel diodes.
[BibTeX] 
IECON 2012  38th Annual Conference on IEEE Industrial Electronics Society2012
arrow_drop_downRainflow 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 fourpoint 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 fourpoint algorithm but considering point comparison than range comparison is also presented. A comparison between the performances of the common rainflow algorithms [610], 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 5minute data load profiles available, the lifetime is estimated to be at 3.4 years.
[BibTeX] 
2012 IEEE International Electric Vehicle Conference2012
arrow_drop_downWireless power transfer has been a popular topic of recent research. Most research has been done to address the limitations of coiltocoil 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.
[BibTeX] 
Proceedings of The 7th International Power Electronics and Motion Control Conference2012
arrow_drop_downThe work developed here proposes a methodology for calculating switching angles for varying DC sources in a multilevel cascaded Hbridges 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.
[BibTeX] 
2012 TwentySeventh Annual IEEE Applied Power Electronics Conference and Exposition (APEC)2012
arrow_drop_downWith 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.
[BibTeX] 
2011 TwentySixth Annual IEEE Applied Power Electronics Conference and Exposition (APEC)2011
arrow_drop_downVehicle 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 nonisolated bidirectional EV/PHEV charger capable of V2G reactive power compensation is presented.
[BibTeX] 
2011 IEEE Energy Conversion Congress and Exposition2011
arrow_drop_downMost 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.
[BibTeX] 
2011 IEEE Energy Conversion Congress and Exposition2011
arrow_drop_downThis work presents an approach to determine the input voltage value of each cell in a cascade Hbridge 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 sevenlevel cascade multilevel inverter operating under a RLC load.
[BibTeX] 
8th International Conference on Power Electronics  ECCE Asia2011
arrow_drop_downMore battery powered electric vehicles (EVs) and plugin 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 onboard 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).
[BibTeX] 
IEEE PES T&D 20102010
arrow_drop_downRenewable energy sources and plugin 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.
[BibTeX] 
2010 IEEE Energy Conversion Congress and Exposition2010
arrow_drop_downElectric vehicles (EVs) and plugin 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 dclink capacitor and the battery.
[BibTeX] 
2010 IEEE Energy Conversion Congress and Exposition2010
arrow_drop_downIn this paper a comparison of performance of an hybrid electric vehicle with an allsilicon (Si), hybrid (Si and SiC), and an allSilicon 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.
[BibTeX] 
2010 TwentyFifth Annual IEEE Applied Power Electronics Conference and Exposition (APEC)2010
arrow_drop_downPlugin 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), onboard, 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 dclink capacitor is evaluated when a PHEV battery is under charging operation. Finally, the impact of providing these services on the batteries is also explained.
[BibTeX] 
2010 IEEE Energy Conversion Congress and Exposition2010
arrow_drop_downThis work approximates the selective harmonic elimination problem using Artificial Neural Networks (ANN) to generate the switching angles in an 11level 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 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 shows to be a suitable tool that brings a small generalization effect on the angles' precision.
[BibTeX] 
The 2010 International Power Electronics Conference  ECCE ASIA 2010
arrow_drop_downWith efforts to reduce the cost, size, and thermal management systems for the power electronics drivetrain in hybrid electric vehicles (HEVs) and plugin 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.
[BibTeX] 
Proceedings of the 48h IEEE Conference on Decision and Control (CDC) held jointly with 2009 28th Chinese Control Conference2009
arrow_drop_downA cascade multilevel inverter consisting of a standard 3leg inverter supplied by a DC source and three full Hbridges each supplied by a capacitor is considered for use as a motor drive. The capacitor Hbridges 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 3leg 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 highfrequency PWM approaches. As is well known, the programmed PWM switching times are computed assuming the drive is in sinusoidal steadystate, that is, the derived switching angles achieve the fundamental while rejecting specified harmonics if the voltage waveforms are in sinusoidal steadystate. 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.
[BibTeX] 
2009 Brazilian Power Electronics Conference2009
arrow_drop_downThis 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 allSiC inverter using SiC JFETs and Schottky diodes are demonstrated.
[BibTeX] 
2009 IEEE Energy Conversion Congress and Exposition2009
arrow_drop_downIn hybrid electric vehicles (HEV), a batterypowered threephase 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 currentsource 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.
[BibTeX] 
2008 TwentyThird Annual IEEE Applied Power Electronics Conference and Exposition2008
arrow_drop_downThis paper presents a fundamental frequency modulated multilevel inverter scheme for use with a threephase standalone photovoltaic (PV) system. The system consists of four series connected PV arrays, a fivelevel diodeclamped multilevel inverter (DCMLI) generating fundamental modulation staircase threephase output voltages, and a threephase induction motor as the load. In order to validate the proposed concept, simulation studies and experimental measurements, done using a smallscale laboratory prototype, are also presented. The results show the feasibility of the fundamental switching application in three phase standalone PV power systems.
[BibTeX] 
Comparison of fundamental frequency and PWM methods applied on a hybrid cascaded multilevel inverter2008 34th Annual Conference of IEEE Industrial Electronics2008
arrow_drop_downThis 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 3leg inverter (one leg for each phase) and Hbridge in series with each inverter leg. It can use only a single DC power source to supply a standard 3leg inverter along with three full Hbridges 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.
[BibTeX] 
2008 51st Midwest Symposium on Circuits and Systems2008
arrow_drop_downA hybrid multilevel inverter model based on PSIM and MATLAB/SIMULINK is presented in this paper. It consists of a standard 3leg inverter (one leg for each phase) and Hbridge in series with each inverter leg. The inverter can be used in hybrid electric vehicles (HEV) and electric vehicles (EV). The cosimulation 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 5level hybrid inverter is tested, which is controlled by multilevel carrierbased PWM signals. The simulation yields a good estimation for the test results of the inverter.
[BibTeX] 
2008 IEEE Power Electronics Specialists Conference2008
arrow_drop_downA hybrid cascaded multilevel inverter with PWM method is presented in this paper. It consists of a standard 3leg inverter (one leg for each phase) and Hbridge in series with each inverter leg. It can use only a single DC power source to supply a standard 3leg inverter along with three full Hbridges supplied by capacitors. Multilevel carrier based PWM method is used to produce a fivelevel 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.
[BibTeX] 
2008 IEEE Power and Energy Society General Meeting  Conversion and Delivery of Electrical Energy in the 21st Century2008
arrow_drop_downMany 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.
[BibTeX] 
2008 IEEE/PES Transmission and Distribution Conference and Exposition2008
arrow_drop_downEnvironmentally 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 everincreasing 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.
[BibTeX] 
2008 IEEE Power Electronics Specialists Conference2008
arrow_drop_downA new approach for selective harmonic elimination in a 7level 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 realtime 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.
[BibTeX] 
2008 IEEE Industry Applications Society Annual Meeting2008
arrow_drop_downThe application of SiC devices (as battery interface, motor controller, etc.) in a hybrid electric vehicle (HEV) will benefit from their hightemperature capability, highpower density, and high efficiency. Moreover, the light weight and small volume will affect the whole power train system in a HEV, and thus performance and cost. In this work, the performance of HEVs is analyzed using PSAT (powertrain system analysis tool, vehicle simulation software). Power loss models of a SiC inverter are incorporated into PSAT powertrain models in order to study the impact of SiC devices on HEVs. Two types of HEVs are considered. One is the 2004 Toyota Prius HEV, the other is a plugin HEV (PHEV), whose powertrain architecture is the same as that of the 2004 Toyota Prius HEV. The vehiclelevel benefits from the introduction of the 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 the vehicles consume less energy and emit less harmful gases. It also makes it possible to improve the system compactness with simplified thermal management system. For the PHEV, the benefits are more distinct. Especially, the size of battery bank can be reduced for optimum design.
[BibTeX] 
2007 IEEE International Electric Machines & Drives Conference2007
arrow_drop_downSensors 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 faultfree 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 offset 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.
[BibTeX] 
2007 IEEE Power Electronics Specialists Conference2007
arrow_drop_downThis paper presents a modulation extension control algorithm for hybrid cascaded Hbridge multilevel converters. The hybrid cascaded Hbridge 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 7level 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 Hbridge multilevel converters.
[BibTeX] 
2007 IEEE International Electric Machines & Drives Conference2007
arrow_drop_downA 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 threephase PM drive using only a single DC voltage source. The input of a standard threeleg inverter is connected to the DC source and the output of each leg is fed through an Hbridge (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 Hbridges 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 threeleg inverter.
[BibTeX] 
APEC 07  TwentySecond Annual IEEE Applied Power Electronics Conference and Exposition2007
arrow_drop_downThe interest here is in using a single DC power source to construct a 3phase 5level cascade multilevel inverter to be used as a drive for a PM traction motor. The 5level inverter consists of a standard 3leg inverter (one leg for each phase) and an Hbridge 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 3leg inverter by itself.
[BibTeX] 
2007 IEEE Industry Applications Annual Meeting2007
arrow_drop_downThis 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 3phase 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 Hbridge multilevel boost inverter for EV and HEV applications is proposed in this paper. Traditionally, each Hbridge needs a DC power supply. The proposed inductorless cascaded Hbridge multilevel boost inverter uses a standard 3leg inverter (one leg for each phase) and an Hbridge 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 5level phase voltage. Experiments show that the proposed inductorless DCAC cascaded Hbridge multilevel boost inverter can output a boosted AC voltage.
[BibTeX] 
2007 IEEE International Electric Machines & Drives Conference2007
arrow_drop_downThe ability of cascaded Hbridge multilevel inverter drives (MLID) to operate under faulty condition including AIbased 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.
[BibTeX] 
TwentyFirst Annual IEEE Applied Power Electronics Conference and Exposition, 2006. APEC '06.2006
arrow_drop_downSilicon 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 IGBTSiC Schottky diode hybrid 55kW inverter by replacing the Si pn diodes in Semikron's automotive inverter with Cree's madetoorder 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 allSi inverter.
[BibTeX] 
TwentyFirst Annual IEEE Applied Power Electronics Conference and Exposition, 2006. APEC '06.2006
arrow_drop_downA 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 n1 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.
[BibTeX] 
2006 37th IEEE Power Electronics Specialists Conference2006
arrow_drop_downThis paper presents a hybrid cascaded Hbridge multilevel motor drive control scheme for electric/hybrid electric vehicles where each phase of a threephase cascaded multilevel converter can be implemented using only a single DC source and capacitors for the other DC sources. Traditionally, each phase of a threephase 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 7level equal step output voltage switching control can simultaneously maintain the balance of DC voltage levels of the capacitors, eliminate specified low order nontriplen harmonics, and produce a nearly sinusoidal threephase 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.
[BibTeX] 
Conference Record of the 2006 IEEE Industry Applications Conference FortyFirst IAS Annual Meeting2006
arrow_drop_downThe purpose of this work is to provide validated models to estimate the performance of a SiCbased 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 SiCbased converter. (2) With the same thermal limit, large savings in system weight and volume combined with a high efficiency were found in the SiCbased converter
[BibTeX] 
2006 IEEE Workshops on Computers in Power Electronics2006
arrow_drop_downMost 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 systemlevel 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
[BibTeX] 
Twentieth Annual IEEE Applied Power Electronics Conference and Exposition, 2005. APEC 2005.2005
arrow_drop_downThis paper presents a twophase 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 hybridelectric 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 gatecontroller 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 airconditioner (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
[BibTeX] 
Fourtieth IAS Annual Meeting. Conference Record of the 2005 Industry Applications Conference, 2005.2005
arrow_drop_downThis 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 allSiC inverter. In addition to the simulations, experimental tests have also been conducted on SiC VJFETs and Schottky diodes for parameter extraction.
[BibTeX] 
Twentieth Annual IEEE Applied Power Electronics Conference and Exposition, 2005. APEC 2005.2005
arrow_drop_downSilicon carbide (SiC) unipolar devices have much higher breakdown voltages because of the ten times greater electric field strength of SiC compared with silicon (Si). 4HSiC unipolar devices have higher switching speeds due to the higher bulk mobility of 4HSiC 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
[BibTeX] 
2005 IEEE Vehicle Power and Propulsion Conference2005
arrow_drop_downSilicon 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 IGBTSiC Schottky diode hybrid 55 kW inverter by replacing the Si pn diodes in Semikron's automotive inverter with Cree's madetoorder higher current SiC Schottky diodes. This paper shows the results obtained from testing this inverter and compares it to a similar allSi inverter.
[BibTeX] 
IEEE International Conference on Electric Machines and Drives, 2005.2005
arrow_drop_downAxialgap 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
[BibTeX] 
Applied Power Electronics Conference and Exposition, 2004. APEC '04. Nineteenth Annual IEEE2004
arrow_drop_downStatic characteristics of fuel cells show more than a 30% difference in the output voltage between noload to fullload 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 DCDC 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.
[BibTeX] 
Conference Record of the 2004 IEEE Industry Applications Conference, 2004. 39th IAS Annual Meeting.2004
arrow_drop_downMultilevel 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 noload to fullload conditions. This paper first describes standard fuel cell power electronics interfaces, then reviews a few of the multi input systems and explores additional configurations.
[BibTeX] 
2004 IEEE 35th Annual Power Electronics Specialists Conference (IEEE Cat. No.04CH37551)2004
arrow_drop_downIn this paper, a genetic algorithm (GA) optimization technique is applied to multilevel inverter to determine optimum switching angles for cascaded multilevel inverters for eliminating some 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 7level inverter is considered, and the optimum switching angles are calculated offline to eliminate the 5th and the 7th harmonics. Then, these angles are used in an experimental setup to validate the results.
[BibTeX] 
IEEE Power Engineering Society General Meeting, 2004.2004
arrow_drop_downThe 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 4HSiC 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.
[BibTeX] 
Conference Record of the 2004 IEEE Industry Applications Conference, 2004. 39th IAS Annual Meeting.2004
arrow_drop_downThe 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 4HSiC GTO thyristor and pn 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.
[BibTeX] 
Power Electronics in Transportation (IEEE Cat. No.04TH8756)2004
arrow_drop_downSilicon (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 °C to 175 °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 onstate resistance and the switching losses.
[BibTeX] 
2004 IEEE 35th Annual Power Electronics Specialists Conference (IEEE Cat. No.04CH37551)2004
arrow_drop_downStatic characteristics of fuel cells show more than a 30% difference in the output voltage between noload to fullload 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.
[BibTeX] 
Electric Machines and Drives Conference, 2003. IEMDC'03. IEEE International2003
arrow_drop_downIn this paper, a modular Simulink implementation of an induction machine model is described in a stepbystep 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 openloop constant V/Hz control and indirect vector control are given. Finally, the use of the model as an Induction generator is demonstrated.
[BibTeX] 
Industrial Electronics Society, 2003. IECON '03. The 29th Annual Conference of the IEEE2003
arrow_drop_downAccording to SECA program guidelines, solid oxide fuel cells (SOFC) are produced in the form of 310 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.
[BibTeX] 
2002 IEEE 33rd Annual IEEE Power Electronics Specialists Conference. Proceedings (Cat. No.02CH37289)2002
arrow_drop_downThe 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 highvoltage 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
[BibTeX] 
Proceedings IEEE 56th Vehicular Technology Conference2002
arrow_drop_downMaterials 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.
[BibTeX] 
Conference Record of the 2002 IEEE Industry Applications Conference. 37th IAS Annual Meeting (Cat. No.02CH37344)2002
arrow_drop_downMaterials 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 abovementioned interactive design, in this paper, the device parameters, which need to be improved in order to design better devices, are discussed.
[BibTeX] 
Industrial Electronics Society, 2001. IECON '01. The 27th Annual Conference of the IEEE2001
arrow_drop_downThe 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 highvoltage power electronics applications, including hybrid electric vehicle (HEV) traction drives. In this paper, the effect of SiCbased 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 threephase PWM inverter (TPPWMI). For more accurate results, device physics is taken into consideration to find the loss equations for the controllable switches
[BibTeX] 
2001 IEEE International Conference on Systems, Man and Cybernetics. eSystems and eMan for Cybernetics in Cyberspace (Cat.No.01CH37236)2001
arrow_drop_downAs 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, threestep, variable pulsewidth (PW) square wave voltage waveform. A genetic algorithm approach is used to determine the PW to optimize the output voltage harmonic content
[BibTeX] 
Industrial Electronics Society, 1998. IECON '98. Proceedings of the 24th Annual Conference of the IEEE1998
arrow_drop_downSoftswitched 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 softswitched DCAC converter for AC motor drive that operates on the principle of integral pulse modulation. A lightweight ultralow 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 softswitched 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 MCTPEBB (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 fourquadrant vectorcontrolled 5 hp induction motor drive using the link frequency of 20 kHz. A laboratory test of 5 hp drive is in progress
[BibTeX] 
Industrial Electronics Society, 1998. IECON '98. Proceedings of the 24th Annual Conference of the IEEE1998
arrow_drop_downHigh 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 performanceenhanced highfrequency nonresonant link power conversion system where the input DC is converted to high frequency (20 to 50 kHz range) singlephase AC, and then converted to variable frequency variable voltage threephase AC for driving an AC motor load. A lightweight ultralow 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 softswitched, 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 MCTPEBB (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
[BibTeX]