65 results on '"Fred Wang"'
Search Results
2. Unifying the Transformer Current in Multiple Phase Modulation Without Current Spike During Load Transients
- Author
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Yu Yan, Hua Bai, Ruirui Chen, Leon M. Tolbert, and Fred Wang
- Subjects
Electrical and Electronic Engineering - Published
- 2022
3. Wide Bandgap Semiconductor-Based Power Electronics for Aviation
- Author
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Fei Fred Wang, Ruirui Chen, and Kaushik Rajashekara
- Subjects
Control and Systems Engineering ,Energy Engineering and Power Technology ,Electrical and Electronic Engineering - Published
- 2022
4. Power Electronics: A critical enabler of future hydrogen–electric systems for aviation
- Author
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Fei Fred Wang, Ruirui Chen, and Zhou Dong
- Subjects
Energy Engineering and Power Technology ,Electrical and Electronic Engineering - Published
- 2022
5. DC-Saturated Continuously Variable Series Reactors (CVSRs) for Power Flow Control in Power Transmission Systems
- Author
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Jingxin Wang, Sheng Zheng, Leon M. Tolbert, and Fred Wang
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Power transmission ,Transmission (telecommunications) ,Control theory ,Computer science ,Energy Engineering and Power Technology ,Output impedance ,Transmission system ,Electrical and Electronic Engineering ,Systems modeling ,Current source ,Power (physics) - Abstract
This paper proposes a novel continuously variable series reactor (CVSR) based on a dc current controller (DCC) to manage power flow in transmission systems. There are threefold major contributions. First, the three-dimensional electromagnetic interaction has been comprehensively analyzed to extend the understanding beyond the conventional 2D relationship. Second, a high-fidelity reluctance model of the CVSR with an improved DCC model is proposed and implemented. To overcome the fundamental concern for the system modeling, the DCC has been modeled as an ideal current source in parallel with an output impedance. The induced back-EMF can be precisely projected which provides critical design guidelines for the DCC. Third, inspired by the theoretical analysis and modeling, a reliable high power DCC converter is designed accordingly to interface with kV-level back-EMF and supply kA-level dc current for a 115 kV / 1500 A CVSR. Experiments are conducted in a practical transmission demonstration system. When the ac current in the transmission system varies from zero to 1500 A, experimental results show that the proposed CVSR can continuously regulate the reactance from 1.6 Ω to 5 Ω, validating the effectiveness of the proposed system design and modeling methodology.
- Published
- 2022
6. A Potential Issue of Using the MIMO Nyquist Criterion in Impedance-Based Stability Analysis
- Author
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Liang Qiao, Yaosuo Xue, Le Kong, and Fred Wang
- Subjects
Electrical and Electronic Engineering - Published
- 2022
7. Comprehensive Analysis and Improvement Methods of Noise Immunity of Desat Protection for High Voltage SiC MOSFETs With High DV/DT
- Author
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Xingxuan Huang, Shiqi Ji, Cheng Nie, Dingrui Li, Min Lin, Leon M. Tolbert, Fred Wang, and William Giewont
- Published
- 2022
8. Grid Strengthening IBR: An Inverter-Based Resource Enhanced by a Co-Located Synchronous Condenser for High Overcurrent Capability
- Author
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Haiguo Li, Cheng Nie, and Fei (fred) Wang
- Subjects
General Medicine - Published
- 2022
9. Real-Time Power Management for Microgrids With Dynamic Boundaries and Multiple Source Locations
- Author
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Chengwen Zhang, Yu Su, Dingrui Li, Lin Zhu, He Yin, Yiwei Ma, Ishita Ray, Fred Wang, Leon M. Tolbert, and Yilu Liu
- Subjects
General Computer Science ,General Engineering ,General Materials Science ,Electrical and Electronic Engineering - Published
- 2022
10. Instability Issue of Paralleled Dies in an SiC Power Module in Solid-State Circuit Breaker Applications
- Author
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Zhou Dong, Fei Fred Wang, Ren Ren, Leon M. Tolbert, and Wen Zhang
- Subjects
Physics ,Operating point ,Oscillation ,Control theory ,Power module ,Transconductance ,MOSFET ,Trajectory ,Electrical and Electronic Engineering ,Circuit breaker ,Voltage - Abstract
Paralleled dies in a power module could have instability issues during high current switching transients. The instability is caused by the differential-mode oscillation among paralleled MOSFETs. Conventional analyses of paralleled MOSFETs’ stability are normally limited to a single operating point, which ignores the influences of the switching trajectory and nonlinear device parameters on stability. This article reveals that the switching trajectory can significantly influence parallel stability. The analysis is improved by solving eigenvalues of state-space modeling system matrices of all operating points that the switching trajectory goes through considering nonlinear device parameters. Higher voltage and current stresses result in greater real parts of complex eigenvalues, which explains why the paralleled MOSFETs are more unstable with higher voltage and current stresses. To improve stability in solid-state circuit breaker applications, we propose a method to manipulate the switching trajectory to avoid the unstable region where the conventional hard switching trajectory normally goes through. Experimental results show that the turn- off current capability can be increased from ∼five times of rated current with the gate oscillation using the conventional turn- off trajectory to ∼ten times of rated current without the gate oscillation using the optimal turn- off trajectory.
- Published
- 2021
11. Design Optimization of Medium-Frequency Transformer for DAB Converters With DC Bias Capacity
- Author
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Siqi Li, Xiaohua Jiang, Pengfei Yao, Fred Wang, Peng Xue, and Sizhao Lu
- Subjects
Leakage inductance ,Materials science ,Energy Engineering and Power Technology ,Current source ,Converters ,Topology ,Inductor ,law.invention ,Inductance ,law ,Electromagnetic coil ,Electrical and Electronic Engineering ,Transformer ,DC bias - Abstract
Medium-frequency transformer (MFT) dc bias is critical for the safe operation of dual-active-bridge (DAB) converters. To analyze the dc bias, expressions of dc bias are derived for SiC MOSFET DAB converters. It shows that the dc bias is a current source in steady state; thus, a dc bias current capacity is defined and used as a design constraint in the optimization of MFT. The dc bias current capacity is related to core materials, geometric parameters, and flux density, which is analyzed with analytical expression. Optimization equations with geometric variables are derived, which can be solved theoretically or numerically for both interleaved winding (IW) and separated winding (SW) MFT without and/or with leakage inductance design. Based on the optimization equations, different MFT designs for a 150-kW SiC MOSFET DAB converter are compared on the aspects of core materials, winding structures, and without/with leakage inductance design. The combination of IW structure MFT with auxiliary phase shift inductors is chosen, and the assembled prototype is tested with the 150-kW DAB converter. The designed dc bias capacity, temperature rise, and efficiency are verified.
- Published
- 2021
12. Design Considerations for High-Voltage Insulated Gate Drive Power Supply for 10-kV SiC MOSFET Applied in Medium-Voltage Converter
- Author
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Xingxuan Huang, William Giewont, James Palmer, Leon M. Tolbert, Li Zhang, Fei Fred Wang, Shiqi Ji, and Shida Gu
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Materials science ,business.industry ,020208 electrical & electronic engineering ,Electrical engineering ,High voltage ,Hardware_PERFORMANCEANDRELIABILITY ,02 engineering and technology ,Capacitance ,law.invention ,Reliability (semiconductor) ,Control and Systems Engineering ,law ,Hardware_INTEGRATEDCIRCUITS ,0202 electrical engineering, electronic engineering, information engineering ,Gate driver ,Voltage regulation ,Electrical and Electronic Engineering ,business ,Transformer ,Voltage converter ,Voltage - Abstract
High-performance gate drive power supply (GDPS) plays a crucial role in ensuring the reliability and safety of the gate driver for power semiconductor devices. This article focuses on the design of a high-voltage-insulated GDPS for the 10-kV silicon carbide MOSFET in medium-voltage (MV) application. Design considerations, including insulation scheme, high-voltage-insulated transformer design, and load voltage regulation scheme, are proposed. In addition, the performance of the secondary-side-regulated (SSR) GDPS and that of the primary-side-regulated (PSR) GDPS are compared for several aspects, including interwinding capacitance, load voltage regulation rate, conversion efficiency, and hardware complexity. Finally, an SSR GDPS and a PSR GDPS, with an insulation voltage of 20 kV, are built in the lab. The test results demonstrate that the PSR GDPS is more preferable because of lower interwinding capacitance, lower load voltage regulation rate, higher conversion efficiency, and simpler control circuit.
- Published
- 2021
13. High-Bandwidth Low-Inductance Current Shunt for Wide-Bandgap Devices Dynamic Characterization
- Author
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Neil Forcier, Brush Iv Edward Vernon, Wen Zhang, Zheyu Zhang, and Fred Wang
- Subjects
Materials science ,business.industry ,020208 electrical & electronic engineering ,Bandwidth (signal processing) ,Gallium nitride ,02 engineering and technology ,equipment and supplies ,law.invention ,Inductance ,chemistry.chemical_compound ,chemistry ,law ,Parasitic element ,0202 electrical engineering, electronic engineering, information engineering ,Waveform ,Optoelectronics ,Current sensor ,Electrical and Electronic Engineering ,Resistor ,Coaxial ,business - Abstract
High bandwidth sensors are required to measure the wide-bandgap devices’ transient behavior because of their fast switching speed. In addition to high bandwidth, the current sensor must introduce little extra parasitic inductance to the switching power loop. The analysis of conventional shunt resistors shows the key to high bandwidth is the coaxial structure and its parasitic inductance is proportional to its transient heat energy rating. By combining the structure of coaxial shunt resistor and alumina substrate surface mount thin film resistors, a novel surface mount coaxial shunt resistor is introduced. Experimental measurement verifies its capability of achieving very high bandwidth while introducing very low parasitic inductance. The design can achieve up to 2.23-GHz measurement bandwidth while keeping its parasitic inductance as low as 0.12 nH. Application in gallium nitride heterojunction-field-effect-transistors double pulse test shows it can faithfully capture the transient current waveform while introducing little interference to the switching behavior.
- Published
- 2021
14. Benefits of high-voltage SiC-based power electronics in medium-voltage power-distribution grids
- Author
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Fred Wang and Shiqi Ji
- Subjects
Materials science ,business.industry ,Electrical engineering ,Energy Engineering and Power Technology ,High voltage ,Power (physics) ,chemistry.chemical_compound ,chemistry ,Control and Systems Engineering ,Power electronics ,MOSFET ,Silicon carbide ,Power semiconductor device ,Microgrid ,Electrical and Electronic Engineering ,business ,Voltage - Abstract
Medium-voltage (MV) power electronics equipment has been increasingly applied in distribution grids, and high-voltage (HV) silicon carbide (SiC) power semiconductors have attracted considerable attention in recent years. This paper first overviews the development and status of HV SiC power semiconductors. Then, MV power-converter applications in distribution grids are summarized and the benefits of HV SiC in these applications are presented. Microgrids, including conventional and asynchronous microgrids, that can fully demonstrate the benefits of HV SiC power semiconductors are selected to investigate the benefits of HV SiC in detail, including converter-level benefits and system-level benefits. Finally, an asynchronous microgrid power-conditioning system (PCS) prototype using a 10 kV SiC MOSFET is presented.
- Published
- 2021
15. Modular Multilevel Converter (MMC) Modeling Considering Submodule Voltage Sensor Noise
- Author
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Leon M. Tolbert, James Palmer, Shiqi Ji, Fred Wang, and Xingxuan Huang
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Computer science ,business.industry ,020208 electrical & electronic engineering ,Topology (electrical circuits) ,02 engineering and technology ,Modular design ,Capacitance ,Noise (electronics) ,Power (physics) ,Switching time ,Duty cycle ,Voltage sensor ,0202 electrical engineering, electronic engineering, information engineering ,Electronic engineering ,Power semiconductor device ,Electrical and Electronic Engineering ,business - Abstract
The modular multilevel converter (MMC) is a popular topology in medium- and high-voltage applications, and many efforts have been spent on MMC modeling. However, the impact of submodule voltage sensor noise (SVSN), which becomes more severe due to increasing switching speed of power semiconductors and compact submodule design, has not been considered in conventional models. In this letter, the SVSN is introduced by coupling capacitances between the sensor and power stage in an MMC switching model. Furthermore, the SVSN impact is considered in an MMC average model based on derivation of the relationship between the SVSN and the duty cycle. The proposed MMC switching model and average model considering the SVSN are validated by comparing simulations with experimental results in an MMC prototype using 10-kV SiC MOSFETS.
- Published
- 2021
16. SiC and GaN Devices With Cryogenic Cooling
- Author
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Fei Fred Wang and Ruirui Chen
- Subjects
Wide bandgap device ,device characterization ,Materials science ,Physics::Instrumentation and Detectors ,business.industry ,Band gap ,GaN HEMT ,Astrophysics::Instrumentation and Methods for Astrophysics ,cryogenic temperature ,Gallium nitride ,Cryogenics ,Semiconductor device ,TK1-9971 ,Switching time ,Condensed Matter::Materials Science ,chemistry.chemical_compound ,chemistry ,cryogenically-cooled converter ,Power electronics ,Silicon carbide ,SiC MOSFET ,Optoelectronics ,Junction temperature ,Electrical engineering. Electronics. Nuclear engineering ,business - Abstract
This article presents the cryogenically cooled application for wide bandgap (WBG) semiconductor devices. Characteristics of silicon carbide (SiC) and gallium nitride (GaN) at cryogenic temperatures are illustrated. SiC MOSFETs exhibit increased on-state resistance and slower switching speed at cryogenic temperatures. However, cryogenic cooling provides low ambient temperature environment and thus enables the SiC converter to operate at lower junction temperature to achieve higher efficiency compared to room temperature cooling. A cryogenically cooled MW-level SiC inverter prototype is developed and demonstrated the feasibility of operating high-power SiC converter with cryogenic cooling. GaN HEMTs exhibit more than five times on-state resistance reduction and faster switching speed at cryogenic temperatures which makes GaN HEMTs an excellent candidate for cryogenic power electronics applications. The significantly reduced on-state resistance of GaN devices provides the possibility to operate them at a current level much higher than rated current at cryogenic temperatures. A GaN double pulse test (DPT) circuit is constructed and demonstrated that GaN HEMTs can operate at nearly four times of rated current at cryogenic temperatures. Challenges of utilizing WBG device with cryogenic cooling are discussed and summarized.
- Published
- 2021
17. Planned Islanding Algorithm Design Based on Multiple Sub-Microgrids With Dynamic Boundary
- Author
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Dingrui Li, Fred Wang, Yu Su, He Yin, Ishita Ray, Chengwen Zhang, Leon M. Tolbert, Yilu Liu, Lin Zhu, and Yiwei Ma
- Subjects
TK1001-1841 ,Distribution or transmission of electric power ,Computer science ,business.industry ,Planned islanding ,TK3001-3521 ,AC power ,Power (physics) ,microgrid ,Production of electric energy or power. Powerplants. Central stations ,Control theory ,Control system ,Distributed generation ,Islanding ,Algorithm design ,Microgrid ,business - Abstract
Planned islanding is one of the fundamental functions of microgrid (MG) controllers. However, existing planned islanding functions cannot be directly utilized in MGs that have the capability to have both dynamic boundary and multiple sub-MGs. To optimize the smart switch operation and distributed energy resource (DER) output power, a planned islanding algorithm is designed to minimize the battery energy storage systems’ power difference before and after a planned islanding. To verify the performance of the proposed algorithm, a hardware-in-the-loop (HIL) test has been conducted by implementing the algorithm in a general purpose MG controller system. The results demonstrate that the difference in active power before and after the planned islanding decreases significantly with the proposed algorithm.
- Published
- 2021
18. Evaluation on the Autoconfigured Multipulse AC/DC Rectifiers and Their Application in More Electric Aircrafts
- Author
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Jie Chen, Jiawei Chen, Fred Wang, Yuting Shen, Chunying Gong, and Han Bai
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Aviation ,business.industry ,Computer science ,020209 energy ,Power system harmonics ,020208 electrical & electronic engineering ,Energy Engineering and Power Technology ,Transportation ,02 engineering and technology ,Network topology ,law.invention ,Harmonic analysis ,Harmonic reduction ,Power rating ,law ,Automotive Engineering ,0202 electrical engineering, electronic engineering, information engineering ,Electronic engineering ,Power quality ,Electrical and Electronic Engineering ,business ,Transformer - Abstract
Multipulse ac/dc rectifiers (MPRs) are widely used in aviation applications due to their rugged structure, cost effective, and high-reliability features. In this article, an overview of the recent advances and trends on the MPR technology, mainly the autoconfigured transformer-based MPRs, and its application in more electric aircrafts is performed. This article covers system topologies, transformer configurations, passive and active harmonic reduction schemes, case study, practical selection and design guidelines, and applications. To fairly evaluate the performances of MPRs with different pulse numbers, necessary simulation studies are carried out under comparable conditions, including power rating, input and output specifications, and transformer configuration. Then, an 18-pulse asymmetric delta-polygon configured prototype is established based on the simulation evaluation and experimental verification is performed. It is expected that this article can provide a broad perspective on MPR technology, and, in particular, highlight the latest emerged technology that significantly promotes the performances of MPRs. More importantly, it is desired that the results obtained in this article can provide an effective selection guideline and design suggestion for researchers and engineers engaged in designing MPRs, especially for aviation applications.
- Published
- 2020
19. Flux Balancing Control of Ungapped Nanocrystalline Core-Based Transformer in Dual Active Bridge Converters
- Author
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Jiang Xiaohua, Fred Wang, Peng Xue, Shiqi Ji, and Pengfei Yao
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Materials science ,020208 electrical & electronic engineering ,Ampere balance ,02 engineering and technology ,Converters ,Magnetic flux ,Nanocrystalline material ,law.invention ,law ,Control theory ,0202 electrical engineering, electronic engineering, information engineering ,Electrical and Electronic Engineering ,Transformer ,Electrical conductor ,Power control ,DC bias - Abstract
Transformer flux dc bias is a critical issue, impacting the reliable operation of dual active bridge (DAB) converters especially when ungapped high permeability nanocrystalline core is used. Steady state current dc bias can easily saturate ungapped nanocrystalline transformers, and it is even more dangerous in transient conditions. A dc bias model is proposed to analyze steady state dc bias in different load conditions. The magnetizing current detection is necessary for closed-loop control of dc bias; conductors’ position is shown to impact sensor noise, and it is analyzed in detail. To deal with both steady state and transient dc bias, a unified flux balancing control (UFBC) is proposed introducing a predictive bias suppression (PBS) method with closed-loop flux balancing control (CFBC). With the proposed PBS, both primary/secondary current balance and flux balance can be achieved within one switching cycle using UFBC. Power characteristics and interaction between power control and flux balancing control of DAB converters are analyzed, and the CFBC needs to work in a low bandwidth due to sensor bandwidth limitation and interaction between power control and flux balancing control. The UFBC is verified on a 300-kW cascaded DAB converter prototype.
- Published
- 2020
20. Modeling and Mitigation of Multiloops Related Device Overvoltage in Three-Level Active Neutral Point Clamped Converter
- Author
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Handong Gui, Jiahao Niu, Benjamin J. Blalock, Ren Ren, Ruirui Chen, Fei Fred Wang, Benjamin B. Choi, Daniel Costinett, Leon M. Tolbert, Zheyu Zhang, and Bo Liu
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Materials science ,business.industry ,Busbar ,020208 electrical & electronic engineering ,Electrical engineering ,02 engineering and technology ,Converters ,Capacitance ,Clamping ,Inductance ,Switching time ,Overvoltage ,Modulation ,0202 electrical engineering, electronic engineering, information engineering ,Electrical and Electronic Engineering ,business - Abstract
This article establishes an analytical model for the device drain–source overvoltage related to the two loops in three-level active neutral point clamped (3L-ANPC) converters. Taking into account the nonlinear device output capacitance, two common modulation methods are investigated in detail. The results show that the line switching frequency device usually has higher overvoltage, and the switching speed of the high switching frequency device is not strongly influenced by the multiple loops. By keeping the nonactive clamping switch off , the effect of the nonlinear device output capacitance can be significantly mitigated, which helps reduce the overvoltage. Moreover, the loop inductance can be reduced with vertical loop layout and magnetic cancellation in the printed circuit board and busbar design. A 500-kVA 3L-ANPC converter using silicon carbide mosfet s was built and tested. The experimental results validate the overvoltage model of the two modulation methods as well as the busbar design. With the nonactive clamping switch off , the overvoltage of both the high and line switching frequency devices is significantly reduced, which helps achieve higher switching speed.
- Published
- 2020
21. Review of Power Electronics Components at Cryogenic Temperatures
- Author
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Daniel Costinett, Benjamin B. Choi, Handong Gui, Benjamin J. Blalock, Fei Fred Wang, Leon M. Tolbert, Zheyu Zhang, Ruirui Chen, and Jiahao Niu
- Subjects
Materials science ,Physics::Instrumentation and Detectors ,020208 electrical & electronic engineering ,02 engineering and technology ,Cryogenics ,Integrated circuit ,Engineering physics ,Article ,Computer Science::Other ,law.invention ,Condensed Matter::Materials Science ,chemistry.chemical_compound ,Printed circuit board ,Film capacitor ,chemistry ,law ,Power electronics ,visual_art ,Electronic component ,0202 electrical engineering, electronic engineering, information engineering ,Silicon carbide ,visual_art.visual_art_medium ,Electrical and Electronic Engineering ,Resistor - Abstract
In order to apply power electronics systems to applications such as superconducting systems under cryogenic temperatures, it is necessary to investigate the characteristics of different parts in the power electronics system. This article reviews the influence of cryogenic temperature on power semiconductor devices including Si and wide bandgap switches, integrated circuits, passive components, interconnection and dielectric materials, and some typical cryogenic converter systems. Also, the basic theories and principles are given to explain the trends for different aspects of cryogenically cooled converters. Based on the review, Si active power devices, bulk Complementary metal-oxide-semiconductor (CMOS) based integrated circuits, nanocrystalline and amorphous magnetic cores, NP0 ceramic and film capacitors, thin/metal film and wirewound resistors are the components suitable for cryogenic operation. Pb-rich PbSn solder or In solder, classic printed circuit boards material, most insulation papers and epoxy encapsulant are good interconnection and dielectric parts for cryogenic temperatures.
- Published
- 2020
22. Converter-Based Emulation of Battery Energy Storage Systems (BESS) for Grid Applications
- Author
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Jessica D. Boles, Denis Osipov, Jingxin Wang, Fred Wang, Yiwei Ma, and Leon M. Tolbert
- Subjects
Emulation ,Computer science ,business.industry ,Interface (computing) ,Testbed ,Battery (vacuum tube) ,Grid ,Industrial and Manufacturing Engineering ,Electric power system ,Control and Systems Engineering ,Power electronics ,Embedded system ,Electrical and Electronic Engineering ,business ,Voltage - Abstract
Battery energy storage systems (BESSs) tend to be too costly, restrictive, and require high maintenance for experimental use, but power system tests often need their representation. As a solution, we propose an all-in-one, reconfigurable BESS emulation tool for grid applications that only requires one three-phase voltage-source converter. This emulator provides chemistry-specific battery behavior like previous work, but it also includes the BESS's power electronics interface and control as well as automatic frequency and voltage support functions for the attached power system. Thus, it allows simple, plug-and-play BESS emulation for grid applications. This paper details the construction, verification, and use of the BESS emulator in an existing grid testbed and concludes that it provides an inexpensive, easy-to-use alternative to using real BESSs in power system experiments.
- Published
- 2019
23. A Single Gate Driver Based Solid-State Circuit Breaker Using Series Connected SiC MOSFETs
- Author
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Leon M. Tolbert, Xu Yang, Yu Ren, Yunqing Pei, Fred Wang, and Fan Zhang
- Subjects
Materials science ,business.industry ,020208 electrical & electronic engineering ,Topology (electrical circuits) ,Hardware_PERFORMANCEANDRELIABILITY ,02 engineering and technology ,Semiconductor device ,Hardware_GENERAL ,Logic gate ,MOSFET ,Hardware_INTEGRATEDCIRCUITS ,0202 electrical engineering, electronic engineering, information engineering ,Gate driver ,Optoelectronics ,Field-effect transistor ,Electrical and Electronic Engineering ,business ,Circuit breaker ,Hardware_LOGICDESIGN ,Diode - Abstract
Semiconductor devices based solid-state circuit breakers (SSCBs) are promising in the dc power distribution system as protective equipment for their ultrashort action time. This letter proposes a topology of SSCB using series connected silicon carbide (SiC) metal oxide semiconductor field effect transistors (mosfet s), which only requires a single isolated gate driver. The SSCB has very low cost and high reliability because it only has 13 components including passive components and diodes apart from two SiC mosfet s to achieve both balanced voltage distribution during short-circuit interruption duration and reliable positive gate voltage during on -state. The SSCB prototype is built and experimentally verified to interrupt 75 A short-circuit current under the dc-bus voltage of 1200 V within 1.5 μs.
- Published
- 2019
24. Converter-based reconfigurable real-time electrical system emulation platform
- Author
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Yiwei Ma, Fred Wang, Jingxin Wang, and Leon M. Tolbert
- Subjects
Emulation ,business.industry ,Computer science ,Testbed ,Energy Engineering and Power Technology ,Modular design ,Protection system ,Electric power system ,Control and Systems Engineering ,Embedded system ,Power electronics converters ,Electric power ,Electrical and Electronic Engineering ,business ,Software configuration management - Abstract
A Hardware Testbed(HTB) is developed for accurate and flexible emulation and testing of electrical power system and their control, measurement, and protection systems. In the HTB, modular and programmable power electronics converters are used to mimic the static and dynamic characteristics of electrical power components. This paper overviews the development, integration, and application of the HTB, covering emulation principle, hardware and software configuration, and example results of power system research using the HTB. The advantages of the HTB, compared with real-time digital simulation and downscaled hardware-based testing platform are discussed.
- Published
- 2018
25. Modular design method for motor drives
- Author
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Fred Wang, Dong Jiang, Rixin Lai, Zhihao Fang, and Puqi Ning
- Subjects
Computer science ,business.industry ,Process (computing) ,Energy Engineering and Power Technology ,ComputerApplications_COMPUTERSINOTHERSYSTEMS ,Topology (electrical circuits) ,Control engineering ,Insulated-gate bipolar transistor ,Modular design ,Electromagnetic interference ,Motor drive ,Control and Systems Engineering ,Control theory ,EMI ,Electrical and Electronic Engineering ,business - Abstract
This paper introduces the concept of modular design methodology for hardware design and development of motor drives. The modular design process is first introduced separating the hardware development into three parts: controller, mother board and phase-leg module. The control and circuit function can be decoupled from the phase-leg module development. The hardware update can be simplified with the phase-leg module development and verification. Two design examples are used to demonstrate this method: a DC-fed motor drive with Si IGBTs and an AC-fed motor drive with SiC devices. Design of DC-fed motor drive aims at developing the converter with customized IGBT package for high temperature. Experience with development of the converter with commercial IGBTs simplifies the process. As the AC-fed motor drive is a more complex topology using more advanced devices, the modular design method can simplify and improve the development especially for new packaged devices. Also, the modular design method can help to study the electromagnetic interference (EMI) issue for motor drives, which is presented with an extra design example.
- Published
- 2018
26. A Modulation Compensation Scheme to Reduce Input Current Distortion in GaN-Based High Switching Frequency Three-Phase Three-Level Vienna-Type Rectifiers
- Author
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Daniel Costinett, Edward A. Jones, Bo Liu, Fred Wang, Zheyu Zhang, and Ren Ren
- Subjects
010302 applied physics ,Engineering ,Total harmonic distortion ,business.industry ,020208 electrical & electronic engineering ,Electrical engineering ,02 engineering and technology ,Power factor ,01 natural sciences ,Rectifier ,Three-phase ,Distortion ,Harmonics ,0103 physical sciences ,Hardware_INTEGRATEDCIRCUITS ,0202 electrical engineering, electronic engineering, information engineering ,Electronic engineering ,Harmonic ,Electrical and Electronic Engineering ,business ,Pulse-width modulation - Abstract
Wide bandgap semiconductors are gradually being adopted in high power-density high efficiency applications, providing faster switching and lower loss, and at the same time imposing new challenges in control and hardware design. In this paper, a gallium nitride-based Vienna-type rectifier with SiC diodes is proposed to serve as the power factor correction stage in a high-density battery charger system targeting for aircraft applications with 800 Hz ac system and 600 V level dc link, where power quality is required according to DO160E standard. To meet the current harmonic requirement, PWM voltage distortion during the turn-off transient, is studied as the main harmonics contributor. The distortion mechanism caused by different junction capacitances of the switching devices is presented. A mitigation scheme considering the nonlinear voltage-dependent characteristics of these capacitances is proposed and then simplified from a pulse-based turn-off compensation method to a general modulation scheme. Simulation and experimental results with a 450 kHz Vienna-type rectifier demonstrate the performance of the proposed approach, showing a THD reduction from 10% to 3% with a relatively low-speed controller.
- Published
- 2018
27. Methodology for Wide Band-Gap Device Dynamic Characterization
- Author
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Zheyu Zhang, Fei Fred Wang, Ben Guo, Leon M. Tolbert, Benjamin J. Blalock, and Edward A. Jones
- Subjects
Computer science ,Ground ,020208 electrical & electronic engineering ,05 social sciences ,Wide-bandgap semiconductor ,02 engineering and technology ,Inductor ,Power module ,0202 electrical engineering, electronic engineering, information engineering ,Electronic engineering ,0501 psychology and cognitive sciences ,Power semiconductor device ,Electrical and Electronic Engineering ,050107 human factors ,Energy (signal processing) ,Voltage - Abstract
The double pulse test (DPT) is a widely accepted method to evaluate the dynamic behavior of power devices. Considering the high switching-speed capability of wide band-gap devices, the test results are very sensitive to the alignment of voltage and current (V-I) measurements. Also, because of the shoot-through current induced by Cdv/dt (i.e., cross-talk), the switching losses of the nonoperating switch device in a phase-leg must be considered in addition to the operating device. This paper summarizes the key issues of the DPT, including components and layout design, measurement considerations, grounding effects, and data processing. Additionally, a practical method is proposed for phase-leg switching loss evaluation by calculating the difference between the input energy supplied by a dc capacitor and the output energy stored in a load inductor. Based on a phase-leg power module built with 1200-V/50-A SiC MOSFETs, the test results show that this method can accurately evaluate the switching loss of both the upper and lower switches by detecting only one switching current and voltage, and it is immune to V-I timing misalignment errors.
- Published
- 2017
28. Intelligent Gate Drive for Fast Switching and Crosstalk Suppression of SiC Devices
- Author
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Benjamin J. Blalock, Zheyu Zhang, Daniel Costinett, Jeffery Dix, Fei Fred Wang, and Leon M. Tolbert
- Subjects
Computer science ,Hardware_PERFORMANCEANDRELIABILITY ,02 engineering and technology ,Integrated circuit ,law.invention ,Switching time ,Crosstalk ,law ,Power electronics ,Hardware_INTEGRATEDCIRCUITS ,0202 electrical engineering, electronic engineering, information engineering ,Electronic engineering ,0501 psychology and cognitive sciences ,Power semiconductor device ,Electrical and Electronic Engineering ,Electrical impedance ,050107 human factors ,Diode ,business.industry ,020208 electrical & electronic engineering ,05 social sciences ,Transistor ,Electrical engineering ,business ,AND gate ,Hardware_LOGICDESIGN ,Voltage - Abstract
This paper presents an intelligent gate drive for silicon carbide (SiC) devices to fully utilize their potential of high switching-speed capability in a phase-leg configuration. Based on the SiC device's intrinsic properties, a gate assist circuit consisting of two auxiliary transistors with two diodes is introduced to actively control gate voltages and gate loop impedances of both devices in a phase-leg configuration during different switching transients. Compared to conventional gate drives, the proposed circuit has the capability of accelerating the switching speed of the phase-leg power devices and suppressing the crosstalk to below device limits. Based on Wolfspeed 1200-V SiC MOSFETs, the test results demonstrate the effectiveness of this intelligent gate drive under varying operating conditions. More importantly, the proposed intelligent gate assist circuitry is embedded into a gate drive integrated circuit, offering a simple, compact, and reliable solution for end-users to maximize benefits of SiC devices in actual power electronics applications.
- Published
- 2017
29. Virtual Synchronous Generator Control of Full Converter Wind Turbines With Short-Term Energy Storage
- Author
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Liu Yang, Yiwei Ma, Fei Fred Wang, Wenchao Cao, and Leon M. Tolbert
- Subjects
Engineering ,Wind power ,business.industry ,020209 energy ,020208 electrical & electronic engineering ,Energy balance ,ComputerApplications_COMPUTERSINOTHERSYSTEMS ,02 engineering and technology ,Turbine ,Energy storage ,Power optimizer ,Control and Systems Engineering ,Power Balance ,Control theory ,0202 electrical engineering, electronic engineering, information engineering ,Electrical and Electronic Engineering ,Dispatchable generation ,business ,Voltage - Abstract
One way to incorporate the increasing amount of wind penetration is to control wind turbines to emulate the behavior of conventional synchronous generators. However, the energy balance is the main issue for the wind turbines to be truly dispatchable by the power system operator such as the generators. This paper presents a comprehensive virtual generator control method for the full converter wind turbine, with a minute-level energy storage in the dc link as the energy buffer. The voltage closed-loop virtual synchronous generator control of the wind turbine allows it to work under both grid-connected and stand-alone condition. Power balance of the wind turbine system is achieved by controlling the rotor speed of the turbine according to the loading condition. With the proposed control, the wind turbine system can enhance the dynamic response, and can be dispatched and regulated by the system operator. The sizing design of the short term energy storage is also discussed in this paper. Experimental results are presented to demonstrate the feasibility and effectiveness of the proposed control method.
- Published
- 2017
30. Model-Based Dead Time Optimization for Voltage-Source Converters Utilizing Silicon Carbide Semiconductors
- Author
-
Zheyu Zhang, Leon M. Tolbert, Benjamin J. Blalock, Fred Wang, Haifeng Lu, and Daniel Costinett
- Subjects
business.industry ,Buck converter ,Computer science ,020208 electrical & electronic engineering ,05 social sciences ,Electrical engineering ,02 engineering and technology ,Converters ,Dead time ,Inductor ,Thermal conduction ,Flyback diode ,Reliability (semiconductor) ,Semiconductor ,0202 electrical engineering, electronic engineering, information engineering ,Power quality ,0501 psychology and cognitive sciences ,Voltage source ,Electrical and Electronic Engineering ,business ,Sensitivity (electronics) ,050107 human factors - Abstract
Dead time significantly affects the reliability, power quality, and efficiency of voltage-source converters. For silicon carbide (SiC) devices, considering the high sensitivity of turn-off time to the operating conditions (> 5× difference between light load and full load) and characteristics of inductive loads (> 2× difference between motor load and inductor), as well as large additional energy loss induced by the freewheeling diode conduction during the superfluous dead time (∼15% of the switching loss), then the traditional fixed dead time setting becomes inappropriate. This paper introduces an approach to adaptively regulate the dead time considering the current operating condition and load characteristics via synthesizing online monitored turn-off switching parameters in the microcontroller with an embedded preset optimization model. Based on a buck converter built with 1200-V SiC MOSFETs, the experimental results show that the proposed method is able to ensure reliability and reduce power loss by 12% at full load and 18.2% at light load (8% of the full load in this case study).
- Published
- 2017
31. Sequence-Impedance-Based Harmonic Stability Analysis and Controller Parameter Design of Three-Phase Inverter-Based Multibus AC Power Systems
- Author
-
Fred Wang, Wenchao Cao, and Yiwei Ma
- Subjects
020209 energy ,020208 electrical & electronic engineering ,Multibus ,02 engineering and technology ,Stability (probability) ,Harmonic analysis ,Control theory ,Nyquist stability criterion ,0202 electrical engineering, electronic engineering, information engineering ,Harmonic ,Inverter ,Electrical and Electronic Engineering ,Electrical impedance ,Mathematics - Abstract
Three-phase inverter-based multibus ac power systems could suffer from the harmonic instability issue. The existing impedance-based stability analysis method using the Nyquist stability criterion once requires the calculation of right-half-plane (RHP) poles of impedance ratios, which would result in a heavy computation burden for complicated systems. In order to analyze the harmonic stability of multibus ac systems consisting of both voltage-controlled and current-controlled inverters without the need for RHP pole calculation, this paper proposes two sequence-impedance-based harmonic stability analysis methods. Based on the summary of all major connection types including mesh, the proposed Method 1 can analyze the harmonic stability of multibus ac systems by adding the components one by one from nodes in the lowest level to areas in the highest system level, and accordingly, applying the stability criteria multiple times in succession. The proposed Method 2 is a generalized extension of the impedance-sum-type criterion to be used for the harmonic stability analysis of any multibus ac systems based on Cauchy's theorem. The inverter controller parameters can be designed in the forms of stability regions in the parameter space, by repetitively applying the proposed harmonic stability analysis methods. Experimental results of inverter-based multibus ac systems validate the effectiveness of the proposed harmonic stability analysis methods and parameter design approach.
- Published
- 2017
32. Steady-State Modeling of Modular Multilevel Converter Under Unbalanced Grid Conditions
- Author
-
Zhiqiang Wang, Bo Liu, Leon M. Tolbert, Xiaojie Shi, Yalong Li, and Fred Wang
- Subjects
Engineering ,Steady state (electronics) ,business.industry ,020209 energy ,020208 electrical & electronic engineering ,Ripple ,02 engineering and technology ,Fault (power engineering) ,Capacitance ,law.invention ,Capacitor ,Control theory ,law ,0202 electrical engineering, electronic engineering, information engineering ,Inverter ,Electrical and Electronic Engineering ,business ,Electrical impedance ,Voltage - Abstract
This paper presents a steady-state model of MMC for the second-order phase voltage ripple prediction under unbalanced conditions, taking the impact of negative-sequence current control into account. From the steady-state model, a circular relationship is found among current and voltage quantities, which can be used to evaluate the magnitudes and initial phase angles of different circulating current components. Moreover, in order to calculate the circulating current in a point-to-point MMC-based HVdc system under unbalanced grid conditions, the derivation of equivalent dc impedance of an MMC is discussed as well. According to the dc impedance model, an MMC inverter can be represented as a series connected R–L–C branch, with its equivalent resistance and capacitance directly related to the circulating current control parameters. Experimental results from a scaled-down three-phase MMC system under an emulated single-line-to-ground fault are provided to support the theoretical analysis and derived model. This new models provides an insight into the impact of different control schemes on the fault characteristics and improves the understanding of the operation of MMC under unbalanced conditions.
- Published
- 2017
33. Overview of high voltage sic power semiconductor devices: development and application
- Author
-
Shiqi Ji, Fred Wang, and Zheyu Zhang
- Subjects
chemistry.chemical_compound ,Materials science ,chemistry ,Converter design ,Silicon carbide ,High voltage ,General Medicine ,Semiconductor device ,Engineering physics ,Power (physics) - Abstract
Research on high voltage (HV) silicon carbide (SiC) power semiconductor devices has attracted much attention in recent years. This paper overviews the development and status of HV SiC devices. Meanwhile, benefits of HV SiC devices are presented. The technologies and challenges for HV SiC device application in converter design are discussed. The state-of-the-art applications of HV SiC devices are also reviewed.
- Published
- 2017
34. Development, Demonstration, and Control of a Testbed for Multiterminal HVDC System
- Author
-
Leon M. Tolbert, Fred Wang, Bo Liu, Wanjun Lei, Xiaojie Shi, and Yalong Li
- Subjects
Engineering ,business.industry ,020209 energy ,020208 electrical & electronic engineering ,Testbed ,Direct current ,Electrical engineering ,02 engineering and technology ,Line (electrical engineering) ,Power (physics) ,Electric power system ,Transmission line ,0202 electrical engineering, electronic engineering, information engineering ,HVDC converter station ,Electronic engineering ,Electrical and Electronic Engineering ,business ,Circuit breaker - Abstract
This paper presents the development of a scaled four-terminal high-voltage direct current (HVDC) testbed, including hardware structure, communication architecture, and different control schemes. The developed testbed is capable of emulating typical operation scenarios including system start-up, power variation, line contingency, and converter station failure. Some unique scenarios are also developed and demonstrated, such as online control mode transition and station re-commission. In particular, a dc line current control is proposed, through the regulation of a converter station at one terminal. By controlling a dc line current to zero, the transmission line can be opened by using relatively low-cost HVDC disconnects with low current interrupting capability, instead of the more expensive dc circuit breaker. Utilizing the dc line current control, an automatic line current limiting scheme is developed. When a dc line is overloaded, the line current control will be automatically activated to regulate current within the allowable maximum value.
- Published
- 2017
35. A Line Impedance Conditioner for Saturation Mitigation of Zigzag Transformer in Hybrid AC/DC Transmission System Considering Line Unbalances
- Author
-
Bo Liu, Yalong Li, Xiaojie Shi, Fei Fred Wang, and Leon M. Tolbert
- Subjects
Engineering ,Zigzag transformer ,business.industry ,020209 energy ,Quarter-wave impedance transformer ,02 engineering and technology ,Transmission system ,law.invention ,Unbalanced line ,law ,Transmission line ,Hybrid system ,0202 electrical engineering, electronic engineering, information engineering ,Electronic engineering ,Maximum power transfer theorem ,Electrical and Electronic Engineering ,business ,Transformer - Abstract
Hybrid ac/dc transmission extends the power transfer capacity of existing long ac lines closer to their thermal limit, by superposing the dc current onto three-phase ac lines through a zigzag transformer. However, this transformer could suffer saturation under unbalanced line impedance conditions. This paper introduces the concept of hybrid line impedance conditioner (HLIC) as a cost-effective approach to compensate for the line unbalance and therefore avoid saturation. The topology and operation principle are presented. The two-level control strategy is described, which enables autonomous adaptive regulation without the need of system-level control. Design and implementation are also analyzed, including dc-link capacitance as one of the key line conditioner components, HLIC installation, and protection under fault conditions. The cost study on this HLIC-based hybrid system is also performed to reveal the benefits of the solution. Simulation results and experimental results based on a down-scaled prototype are provided to verify the feasibility of the proposed approach.
- Published
- 2017
36. Load-Dependent Soft-Switching Method of Half-Bridge Current Doubler for High-Voltage Point-of-Load Converter in Data Center Power Supplies
- Author
-
Fred Wang, Benjamin J. Blalock, Yutian Cui, Leon M. Tolbert, Fei Yang, and Daniel Costinett
- Subjects
Engineering ,business.industry ,Controller (computing) ,020208 electrical & electronic engineering ,Electrical engineering ,High voltage ,Topology (electrical circuits) ,02 engineering and technology ,Sense (electronics) ,Converters ,Inductor ,Constant power circuit ,Power (physics) ,0202 electrical engineering, electronic engineering, information engineering ,Electronic engineering ,020201 artificial intelligence & image processing ,Electrical and Electronic Engineering ,business - Abstract
With the increased cloud computing and digital information storage, the energy requirement of data centers keeps increasing. A high-voltage point of load (HV POL) with an input series output parallel structure is proposed to convert 400 to 1 VDC within a single stage to increase the power conversion efficiency. The symmetrical controlled half-bridge current doubler is selected as the converter topology in the HV POL. A load-dependent soft-switching method has been proposed with an auxiliary circuit that includes inductor, diode, and MOSFETs so that the hard-switching issue of typical symmetrical controlled half-bridge converters is resolved. The operation principles of the proposed soft-switching half-bridge current doubler have been analyzed in detail. Then, the necessity of adjusting the timing with the loading in the proposed method is analyzed based on losses, and a controller is designed to realize the load-dependent operation. A lossless RCD current sensing method is used to sense the output inductor current value in the proposed load-dependent operation. Experimental efficiency of a hardware prototype is provided to show that the proposed method can increase the converter's efficiency in both heavy- and light-load conditions.
- Published
- 2017
37. Circulating Current Suppressing Control’s Impact on Arm Inductance Selection for Modular Multilevel Converter
- Author
-
Fred Wang, Edward A. Jones, and Yalong Li
- Subjects
Physics ,Short circuit fault ,business.industry ,020209 energy ,020208 electrical & electronic engineering ,Electrical engineering ,Energy Engineering and Power Technology ,02 engineering and technology ,Modular design ,Inductor ,Inductance ,Control theory ,Limit (music) ,0202 electrical engineering, electronic engineering, information engineering ,Harmonic ,Circulating current ,Electrical and Electronic Engineering ,Current (fluid) ,business - Abstract
Arm inductor in a modular multilevel converter (MMC) is used to limit the circulating current and dc short circuit fault current. The circulating current in MMC is dominated by second-order harmonic, which can be largely reduced with circulating current suppressing control. By analyzing the mechanism of the circulating current suppressing control, it is found that the circulating current at switching frequency becomes the main harmonic when suppression control is implemented. Unlike the second-order harmonic that circulates only within the three phases, switching frequency harmonic also flows through the dc side and may further cause high-frequency dc voltage harmonic. This paper develops the theoretical relationship between the arm inductance and switching frequency circulating current, which can be used to guide the arm inductance selection. The experimental results with a downscaled MMC prototype verify the existence of the switching frequency circulating current and its relationship with arm inductance.
- Published
- 2017
38. Three-Phase Power Converter-Based Real-Time Synchronous Generator Emulation
- Author
-
Jingxin Wang, Yiwei Ma, Kevin Tomsovic, Xiaohu Zhang, Liu Yang, Fei Fred Wang, Leon M. Tolbert, and Jing Wang
- Subjects
Emulation ,Engineering ,business.industry ,020208 electrical & electronic engineering ,05 social sciences ,02 engineering and technology ,Permanent magnet synchronous generator ,Electric power system ,Three-phase ,Control theory ,Approximation error ,0202 electrical engineering, electronic engineering, information engineering ,0501 psychology and cognitive sciences ,Voltage source ,Microgrid ,Electrical and Electronic Engineering ,business ,050107 human factors ,Voltage - Abstract
This paper develops a synchronous generator emulator by using a three-phase voltage source converter for transmission level power system testing. Different interface algorithms are compared, and the voltage type ideal transformer model is selected considering accuracy and stability. At the same time, closed-loop voltage control with current feed-forward is proposed to decrease the emulation error. The emulation is then verified through two different ways. First, the output waveforms of the emulator in experiments are compared with the simulation under the same condition. Second, a transfer function perturbation-based error model is obtained and redefined as the relative error for the amplitude and phase between the emulated and the target system over the frequency range of interest. The major cause of the error is investigated through a quantitative analysis of the error with varying parameters.
- Published
- 2017
39. Investigation of Gallium Nitride Devices in High-Frequency LLC Resonant Converters
- Author
-
Fred Wang, Leon M. Tolbert, Weimin Zhang, Benjamin J. Blalock, and Daniel Costinett
- Subjects
010302 applied physics ,Materials science ,business.industry ,020208 electrical & electronic engineering ,Electrical engineering ,Gallium nitride ,02 engineering and technology ,Converters ,01 natural sciences ,Capacitance ,Finite element method ,Power (physics) ,Switching time ,chemistry.chemical_compound ,chemistry ,Electromagnetic coil ,0103 physical sciences ,0202 electrical engineering, electronic engineering, information engineering ,Electrical and Electronic Engineering ,business ,Ultrashort pulse - Abstract
Newly emerged gallium nitride (GaN) devices feature ultrafast switching speed and low on-state resistance that potentially provide significant improvements for power converters. This paper investigates the benefits of GaN devices in an LLC resonant converter and quantitatively evaluates GaN devices’ capabilities to improve converter efficiency. First, the relationship of device and converter design parameters to the device loss is established based on an analytical model of LLC resonant converter operating at the resonance. Due to the low effective output capacitance of GaN devices, the GaN-based design demonstrates about 50% device loss reduction compared with the Si-based design. Second, a new perspective on the extra transformer winding loss due to the asymmetrical primary-side and secondary-side current is proposed. The device and design parameters are tied to the winding loss based on the winding loss model in the finite element analysis (FEA) simulation. Compared with the Si-based design, the winding loss is reduced by 18% in the GaN-based design. Finally, in order to verify the GaN device benefits experimentally, 400- to 12-V, 300-W, 1-MHz GaN-based and Si-based LLC resonant converter prototypes are built and tested. One percent efficiency improvement, which is 24.8% loss reduction, is achieved in the GaN-based converter.
- Published
- 2017
40. Variable Speed Drive Connected Motor Load Emulator for a Multi-Converter-Based Hardware Testbed System
- Author
-
Shuyao Wang, Fred Wang, Yiwei Ma, Leon M. Tolbert, and Jingxin Wang
- Subjects
Variable (computer science) ,business.industry ,Computer science ,Testbed ,Motor load ,business ,Computer hardware - Published
- 2021
41. Design and Implementation of a GaN-Based, 100-kHz, 102-W/in3Single-Phase Inverter
- Author
-
John F. Jansen, Reid Kress, Trento Bradford C, Daniel Costinett, Rick Langley, Chongwen Zhao, Ling Jiang, Bo Liu, Edward A. Jones, Zheyu Zhang, Leon M. Tolbert, and Fei Fred Wang
- Subjects
business.industry ,Computer science ,020209 energy ,020208 electrical & electronic engineering ,Electrical engineering ,Energy Engineering and Power Technology ,Gallium nitride ,02 engineering and technology ,Band-stop filter ,Network topology ,chemistry.chemical_compound ,chemistry ,Power electronics ,Thermal ,0202 electrical engineering, electronic engineering, information engineering ,Electronic engineering ,Inverter ,Electrical and Electronic Engineering ,business ,Decoupling (electronics) ,Power density - Abstract
High power density is a desirable feature of power electronics design, which prompts economic incentives for industrial applications. In this paper, a gallium nitride (GaN)-based 2-kVA single-phase inverter design was developed for the Google Little Box Challenge, which achieves a 102-W/in $^{3}$ power density. First, the static and dynamic temperature-dependent characteristics of multiple SiC and enhancement-mode GaN FETs are investigated and compared. Based on the device testing results, several topologies of the inverter stage and different power decoupling solutions are compared with respect to the device volume, efficiency, and thermal requirements. Moreover, some design approaches for magnetic devices and the implementation of gate drives for GaN devices are discussed in this paper, which enable a compact and robust system. Finally, a dc notch filter and a hard switching full-bridge converter are combined as the proposed design for the prototype. A 2-kVA prototype is demonstrated, which meets the volume, efficiency, and thermal requirements. The performance of the prototype is verified by the experimental results.
- Published
- 2016
42. Capacitor-Clamped, Three-level GaN-Based DC–DC Converter With Dual Voltage Outputs for Battery Charger Applications
- Author
-
Daniel Costinett, Zheyu Zhang, Bo Liu, Fei Fred Wang, Ren Ren, and Edward A. Jones
- Subjects
Forward converter ,Engineering ,business.industry ,Buck converter ,Flyback converter ,020209 energy ,020208 electrical & electronic engineering ,Ćuk converter ,Buck–boost converter ,Electrical engineering ,Energy Engineering and Power Technology ,02 engineering and technology ,law.invention ,Capacitor ,Battery charger ,law ,Boost converter ,0202 electrical engineering, electronic engineering, information engineering ,Electronic engineering ,Electrical and Electronic Engineering ,business - Abstract
Gallium nitride (GaN) heterojunction field-effect transistors are an enabling technology for high-density converter design. This paper proposes a three-level dc–dc converter with dual outputs based on enhancement-mode GaN devices, intended for use as a battery charger in aircraft applications. The charger can output either 28 or 270 V, selected with a jumper, to satisfy the two most common dc bus voltage requirements in airplanes. It operates as an LLC converter in the 28 V mode and as a buck converter in the 270 V mode. In both operation modes, the devices can realize zero voltage switching (ZVS). With the chosen modulation method, the converter can realize automatic voltage balancing of the flying capacitor and the frequency doubling function to act as an interleaved converter. For the LLC mode, the resonant frequency is twice the switching frequency of primary-side switches, and for the buck mode, the frequency of the output inductor current is also twice the switching frequency. This helps to reduce the size of magnetics while maintaining a low switching loss. Also, the converter utilizes a matrix transformer, with resonant parameters designed to reduce conduction loss and avoid ZVS failure. The operating principle of the converter is analyzed and then experimentally verified on a 1.5-kW prototype with 1 MHz resonant frequency.
- Published
- 2016
43. Review of Commercial GaN Power Devices and GaN-Based Converter Design Challenges
- Author
-
Fei Fred Wang, Edward A. Jones, and Daniel Costinett
- Subjects
010302 applied physics ,Commercial scale ,business.industry ,Computer science ,Converter design ,020208 electrical & electronic engineering ,Electrical engineering ,Energy Engineering and Power Technology ,Gallium nitride ,02 engineering and technology ,Converters ,01 natural sciences ,chemistry.chemical_compound ,Reliability (semiconductor) ,chemistry ,0103 physical sciences ,0202 electrical engineering, electronic engineering, information engineering ,Silicon carbide ,Gate driver ,Power semiconductor device ,Electrical and Electronic Engineering ,business - Abstract
Gallium nitride (GaN) power devices are an emerging technology that have only recently become available commercially. This new technology enables the design of converters at higher frequencies and efficiencies than those achievable with conventional Si devices. This paper reviews the characteristics and commercial status of both vertical and lateral GaN power devices, providing the background necessary to understand the significance of these recent developments. In addition, the challenges encountered in GaN-based converter design are considered, such as the consequences of faster switching on gate driver design and board layout. Other issues include the unique reverse conduction behavior, dynamic $R_{\mathrm {{ds}},\mathrm {{on}}}$ , breakdown mechanisms, thermal design, device availability, and reliability qualification. This review will help prepare the reader to effectively design GaN-based converters, as these devices become increasingly available on a commercial scale.
- Published
- 2016
44. The impact of voltage-balancing control on switching frequency of the modular multilevel converter
- Author
-
Fei Fred Wang, Yalong Li, and Edward A. Jones
- Subjects
Engineering ,business.industry ,020209 energy ,020208 electrical & electronic engineering ,Ripple ,Hardware_PERFORMANCEANDRELIABILITY ,02 engineering and technology ,Modular design ,Capacitance ,Power (physics) ,law.invention ,Threshold voltage ,Capacitor ,Hardware_GENERAL ,Control theory ,law ,Harmonics ,Hardware_INTEGRATEDCIRCUITS ,0202 electrical engineering, electronic engineering, information engineering ,Electrical and Electronic Engineering ,business ,Voltage - Abstract
Voltage-balancing control in a modular multilevel converter (MMC) impacts not only the voltage difference among submodule capacitors, but also the power device switching patterns. As a result, MMC possesses a nondeterministic switching pattern and its switching frequency is no longer an independent parameter. This paper theoretically investigates how voltage-balancing control influences the switching frequency in the MMC. Equations describing the relationship between the submodule capacitor unbalanced voltage and converter switching frequency are derived. Since unbalanced voltage also impacts the submodule capacitor ripple voltage and voltage/current harmonics, the design interaction between switching frequency and submodule capacitance, as well as the selection of unbalanced voltage are further investigated. Both simulation and experimental verifications are provided.
- Published
- 2016
45. Temperature-Dependent Short-Circuit Capability of Silicon Carbide Power MOSFETs
- Author
-
Xiaojie Shi, Leon M. Tolbert, Zhenxian Liang, Zhiqiang Wang, Benjamin J. Blalock, Daniel Costinett, and Fred Wang
- Subjects
010302 applied physics ,Materials science ,Thermal runaway ,business.industry ,020208 electrical & electronic engineering ,Electrical engineering ,02 engineering and technology ,01 natural sciences ,Capacitance ,chemistry.chemical_compound ,chemistry ,Gate oxide ,0103 physical sciences ,MOSFET ,0202 electrical engineering, electronic engineering, information engineering ,Silicon carbide ,Optoelectronics ,Electrical and Electronic Engineering ,Power MOSFET ,business ,Short circuit ,Voltage - Abstract
This paper presents a comprehensive short-circuit ruggedness evaluation and numerical investigation of up-to-date commercial silicon carbide (SiC) MOSFETs. The short-circuit capability of three types of commercial 1200-V SiC MOSFETs is tested under various conditions, with case temperatures from 25 to 200 °C and dc bus voltages from 400 to 750 V. It is found that the commercial SiC MOSFETs can withstand short-circuit current for only several microseconds with a dc bus voltage of 750 V and case temperature of 200 °C. The experimental short-circuit behaviors are compared, and analyzed through numerical thermal dynamic simulation. Specifically, an electrothermal model is built to estimate the device internal temperature distribution, considering the temperature-dependent thermal properties of SiC material. Based on the temperature information, a leakage current model is derived to calculate the main leakage current components (i.e., thermal, diffusion, and avalanche generation currents). Numerical results show that the short-circuit failure mechanisms of SiC MOSFETs can be thermal generation current induced thermal runaway or high-temperature-related gate oxide damage.
- Published
- 2016
46. A novel three-phase current source rectifier with delta-type input connection to reduce the device conduction loss
- Author
-
Eddy Aeloiza, Fei Fred Wang, and Ben Guo
- Subjects
Engineering ,business.industry ,020208 electrical & electronic engineering ,Electrical engineering ,Topology (electrical circuits) ,02 engineering and technology ,01 natural sciences ,Inrush current ,Precision rectifier ,010305 fluids & plasmas ,Rectifier ,Three-phase ,0103 physical sciences ,0202 electrical engineering, electronic engineering, information engineering ,Electronic engineering ,Metal rectifier ,Voltage source ,Electrical and Electronic Engineering ,business ,Voltage - Abstract
The three-phase current source rectifier (CSR) features a step-down ac–dc voltage conversion function, smaller ac filter size compared with the traditional two-level voltage source rectifier, and inrush current limiting capability. However, large conduction loss of semiconductor devices has limited the wide application of traditional CSRs. In this paper, a new CSR topology, delta-type current source rectifier (DCSR), is proposed to reduce the conduction loss. The proposed rectifier has delta-type connections on its ac input side and its dc-link current can be shared by multiple devices at a given time. This paper introduces the DCSR's operation principle, modulation scheme, and design method. Based on the analysis, the conduction loss can be reduced by up to 20% with the proposed topology. An 8-kW prototype is then built to experimentally verify the performance of the DCSR.
- Published
- 2016
47. Modulation scheme analysis for high-efficiency three-phase buck-type rectifier considering different device combinations
- Author
-
Eddy Aeloiza, Rolando Burgos, Fei Fred Wang, and Ben Guo
- Subjects
Engineering ,Superposition principle ,Rectifier ,Three-phase ,business.industry ,Control theory ,Modulation ,Commutation ,Electrical and Electronic Engineering ,business ,Flyback diode ,Inrush current ,Space vector modulation - Abstract
The three-phase buck-type rectifier features a step-down ac–dc conversion function, smaller filter size, inrush current limiting capability, and potential for high efficiency, where its switching loss is dependent on the modulation scheme and the specific semiconductors used. In this paper, three different device combinations are compared through experiments on their switching characteristics for the buck rectifier application. It is shown that the switching performance of two series-connected devices becomes worse than a single device due to the superposition of the nonideal semiconductor characteristics. Moreover, the switching loss in the commutation between two switches is usually higher than the one in the commutation between a switch and the freewheeling diode. Taking into consideration both types of commutations, the switching loss of the buck rectifier is then modeled and the analytical equations are derived for four space vector modulation schemes. According to the analysis, each modulation scheme has its own field for high-efficiency application. The most advantageous modulation scheme is identified in this paper for each of the device combinations investigated.
- Published
- 2015
48. A high temperature silicon carbide mosfet power module with integrated silicon-on-insulator-based gate drive
- Author
-
Benjamin J. Blalock, Xiaojie Shi, Leon M. Tolbert, Fred Wang, Zhiqiang Wang, Daniel Costinett, and Zhenxian Liang
- Subjects
Materials science ,business.industry ,Buck converter ,Electrical engineering ,Hardware_PERFORMANCEANDRELIABILITY ,Power module ,MOSFET ,Hardware_INTEGRATEDCIRCUITS ,Gate driver ,Optoelectronics ,Junction temperature ,Power semiconductor device ,Silicon bandgap temperature sensor ,Electrical and Electronic Engineering ,Power MOSFET ,business - Abstract
This paper presents a board-level integrated silicon carbide (SiC) mosfet power module for high temperature and high power density application. Specifically, a silicon-on-insulator (SOI)-based gate driver capable of operating at 200 °C ambient temperature is designed and fabricated. The sourcing and sinking current capability of the gate driver are tested under various ambient temperatures. Also, a 1200 V/100 A SiC mosfet phase-leg power module is developed utilizing high temperature packaging technologies. The static characteristics, switching performance, and short-circuit behavior of the fabricated power module are fully evaluated at different temperatures. Moreover, a buck converter prototype composed of the SOI gate driver and SiC power module is built for high temperature continuous operation. The converter is operated at different switching frequencies up to 100 kHz, with its junction temperature monitored by a thermosensitive electrical parameter and compared with thermal simulation results. The experimental results from the continuous operation demonstrate the high temperature capability of the power module at a junction temperature greater than 225 °C.
- Published
- 2015
49. Characteristic Investigation and Control of a Modular Multilevel Converter-Based HVDC System Under Single-Line-to-Ground Fault Conditions
- Author
-
Xiaojie Shi, Zhiqiang Wang, Bo Liu, Leon M. Tolbert, Yiqi Liu, and Fred Wang
- Subjects
Engineering ,Electric power system ,business.industry ,Control theory ,Automatic frequency control ,HVDC converter station ,Electronic engineering ,Equivalent circuit ,Transmission system ,Electrical and Electronic Engineering ,AC power ,business ,Fault (power engineering) - Abstract
This paper presents the analysis and control of a multilevel modular converter (MMC)-based HVDC transmission system under three possible single-line-to-ground fault conditions, with special focus on the investigation of their different fault characteristics. Considering positive-, negative-, and zero-sequence components in both arm voltages and currents, the generalized instantaneous power of a phase unit is derived theoretically according to the equivalent circuit model of the MMC under unbalanced conditions. Based on this model, a novel double-line frequency dc-voltage ripple suppression control is proposed. This controller, together with the negative- and zero-sequence current control, could enhance the overall fault-tolerant capability of the HVDC system without additional cost. To further improve the fault-tolerant capability, the operation performance of the HVDC system with and without single-phase switching is discussed and compared in detail. Simulation results from a three-phase MMC-HVDC system generated with MATLAB/Simulink are provided to support the theoretical analysis and proposed control schemes.
- Published
- 2015
50. Design and Performance Evaluation of Overcurrent Protection Schemes for Silicon Carbide (SiC) Power MOSFETs
- Author
-
Benjamin J. Blalock, Fred Wang, Xiaojie Shi, Yang Xue, Zhiqiang Wang, and Leon M. Tolbert
- Subjects
Engineering ,business.industry ,Electrical engineering ,Hardware_PERFORMANCEANDRELIABILITY ,Insulated-gate bipolar transistor ,Integrated circuit design ,Fault (power engineering) ,DC-BUS ,Overcurrent ,Control and Systems Engineering ,MOSFET ,Hardware_INTEGRATEDCIRCUITS ,Gate driver ,Electronic engineering ,Power semiconductor device ,Electrical and Electronic Engineering ,Power MOSFET ,business ,Circuit breaker - Abstract
Overcurrent protection of silicon carbide (SiC) metal-oxide-semiconductor field-effect transistors (MOSFETs) remains a challenge due to lack of practical knowledge. This paper presents three overcurrent protection methods to improve the reliability and overall cost of SiC MOSFET-based converters. First, a solid-state circuit breaker (SSCB) composed primarily by a Si IGBT and a commercial gate driver IC is connected in series with the dc bus to detect and clear overcurrent faults. Second, the desaturation technique using a sensing diode to detect the drain-source voltage under overcurrent faults is implemented as well. Third, a novel active overcurrent protection scheme through dynamic evaluation of fault current level is proposed. The design considerations and potential issues of the protection methods are described and analyzed in detail. A phase-leg configuration-based step-down converter is built to evaluate the performance of the protection schemes under various conditions, considering variation of fault type, decoupling capacitance, protection circuit parameters, etc. Finally, a comparison is made in terms of fault response time, temperature-dependent characteristics, and applications to help designers select a proper protection method.
- Published
- 2014
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