Ruoyu Hou

Bio: Ruoyu Hou is an academic researcher from McMaster University. The author has contributed to research in topics: Gallium nitride & Battery charger. The author has an hindex of 11, co-authored 28 publications receiving 412 citations. Previous affiliations of Ruoyu Hou include Illinois Institute of Technology.

Current Status and Future Trends of GaN HEMTs in Electrified Transportation

Abstract: Gallium Nitride High Electron Mobility Transistors (GaN HEMTs) enable higher efficiency, higher power density, and smaller passive components resulting in lighter, smaller and more efficient electrical systems as opposed to conventional Silicon (Si) based devices. This paper investigates the detailed benefits of using GaN devices in transportation electrification applications. The material properties of GaN including the applications of GaN HEMTs at different switch ratings are presented. The challenges currently facing the transportation industry are introduced and possible solutions are presented. A detailed review of the use of GaN in the Electric Vehicle (EV) powertrain is discussed. The implementation of GaN devices in aircraft, ships, rail vehicles and heavy-duty vehicles is briefly covered. Future trends of GaN devices in terms of cost, voltage level, gate driver design, thermal management and packaging are investigated.

Applied Integrated Active Filter Auxiliary Power Module for Electrified Vehicles With Single-Phase Onboard Chargers

Abstract: In single-phase onboard chargers for electrified vehicles, second-order harmonic currents and corresponding ripple voltages exist on the dc bus. The low-frequency harmonic current is normally filtered using a bulk film capacitor or an additional active filter (AF) circuit. This presents an obstacle for improving the power density as well as reducing the cost. This paper proposes a simple and effective method that reduces the bulk capacitor in single-phase chargers and alleviates the low-frequency sinusoidal harmonic current in automotive applications. It applies the low-voltage (LV) battery charger auxiliary power module as an AF to filter the low-frequency harmonic currents in the high-voltage (HV) battery charger when the HV battery is charging. Hence, the integrated active filter auxiliary power module (AFAPM)-based dual-voltage charging system can achieve the AF function without extra power switches, heat sinks, and corresponding gate-drive circuits. In addition, the proposed AFAPM converter can obtain an almost unchanged switch rating to achieve 2.4-kW LV battery charging and 6.6-kW HV active filtering functions. Therefore, the proposed method can reduce the cost for the dual-voltage charging system in electrified vehicles. A 1.2-kW proof-of-concept prototype has also been built and experiments show promising results confirming the effectiveness of the proposed concept.

A Primary Full-Integrated Active Filter Auxiliary Power Module in Electrified Vehicles With Single-Phase Onboard Chargers

Abstract: In single-phase ac high-voltage (HV) battery chargers, as the input current is enforced to be varying sinusoidally in phase with the input voltage, the pulsating power at two times of the line frequency will be seen on the dc-link. Bulky capacitor bank or extra active filter (AF) circuits are needed to assimilate this harmonic current, which become a major barrier in terms of power density and cost. Sinusoidal charging method can be applied, while this might affect the charging efficiency and a deep study is still needed to further investigate on the impact to the Lithium-ion battery. An active filter auxiliary power module (AFAPM) based dual-mode dual-voltage charging system for vehicle application has been proposed. The AFAPM converter has two modes: the HV active filtering mode, in which the vehicle is connected to the grid and the converter assimilates the significant second-order harmonic current; and the low-voltage (LV) battery charging mode, in which the vehicle is running and the converter charges the LV battery from HV battery. However, a relay and inductors are still required in that converter to achieve the dual-mode operation. This paper proposes a primary full-integrated AFAPM for electrified vehicle applications with single-phase onboard chargers. The proposed AFAPM converter is composed of a two-phase bidirectional buck converter to work as an AF and a dual-active-bridge to operate as a LV battery charger auxiliary power module (APM). With the proposed converter, only an extra active energy storage capacitor is needed to achieve the active filtering. All the switches and inductors on the primary stage are shared between the AF and APM. Therefore, the use of a bulky capacitor bank or an additional AF circuit is avoided and, thus, the cost, size, and weight of the dual-voltage charging system in the electrified vehicle applications can be reduced. A 720-W prototype has been built to confirm the effectiveness of the proposed converter.

Parasitic capacitance Eqoss loss mechanism, calculation, and measurement in hard-switching for GaN HEMTs

Abstract: Gallium Nitride enhancement-mode high electron mobility transistors (GaN E-HEMTs) can achieve relatively high-efficiency and high-frequency in hard-switching mode. One particular reason is that GaN E-HEMTs obtain zero reverse-recovery loss and also a zero reverse-recovery period. For silicon (Si) MOSFETs, it has been a well-known issue that their Q rr is too big to switch the transistor in hard-switching mode. Researchers have made extensive efforts to calculate the reverse-recovery loss. However, few of them pay attention to the Q oss , as the Q rr dominates in the turn-on switching loss for Si MOSFETs. For GaN HEMTs, the absence of the Q rr makes the Q oss noticeable, although the value of the Q oss for GaN HEMTs is still the smallest among both Si and Silicon Carbide (SiC) MOSFETs. This paper focus on the Eqoss loss in GaN HEMTs. The Eqoss loss mechanism, detailed calculation and detailed measurement method for GaN HEMTs are provided. In addition, the theoretical results are verified by the double-pulse test at different junction temperatures and gate resistances.

Review of Loss Distribution, Analysis, and Measurement Techniques for GaN HEMTs

Abstract: In recent years, there has been a trend for improved performance in semiconductor switches, allowing power electronic systems to achieve higher efficiency and higher power density. This desired improvement has led to the adoption of wide-bandgap devices-based switches due to the fact that silicon (Si) has been reaching its material limit. Si carbide and gallium nitride (GaN) offer faster switching speeds. Therefore, they require higher level measurement technologies to analyze them. In this article, the theoretical loss breakdown of a GaN-based power electronic system is presented including an analysis of its dynamic behavior. Several methods of measurement are presented to quantify the behavior of fast switching.

Wide Bandgap Devices in AC Electric Drives: Opportunities and Challenges

Abstract: Wide bandgap (WBG) device-based power electronics converters are more efficient and lightweight than silicon-based converters. WBG devices are an enabling technology for many motor drive applications and new classes of compact and efficient motors. This paper reviews the potential applications and advances enabled by WBG devices in ac motor drives. Industrial motor drive products using WBG devices are reviewed, and the benefits are highlighted. This paper also discusses the technical challenges, converter design considerations, and design tradeoffs in realizing the full potential of WBG devices in motor drives. There is a tradeoff between high switching frequency and other issues such as high dv/dt and electromagnetic interference. The problems of high common mode currents and bearing and insulation damage, which are caused by high dv/dt , and the reliability of WBG devices are discussed.

Constant power loads and their effects in DC distributed power systems: A review

Abstract: The penetration of dc distributed power systems is increasing rapidly in electric power grids and other isolated systems to cater demand for cheap, clean, high quality, and uninterrupted power demand of modern society. DC systems are more efficient and suite better to integrate some of the renewable energy sources, storage units, and dc loads. A dc distributed power system usually consists of large number of power electronic converters connected in cascad0ed configuration to satisfy the power quality and voltage magnitude requirements of the sources and loads. Tightly-regulated power converters in the aforementioned settings exhibit negative incremental impedance and behave as constant power loads (CPLs), and tend to destabilize their feeder systems and upstream converters. The presence of CPLs reduces effective damping of the system leading to instability of the whole system and present significant challenge in the system operation and control. In-depth knowledge of the instability effects of constant power loads (CPLs), available stabilizing techniques and stability analysis methods, is imperious to the young researchers, system designers, system integrators, and practicing engineers working in the field of dc power systems and emerging applications of dc power. This paper is intended to fill this gape by documenting present state of the art and research needs in one article. Modeling, behaviour and effects of typical CPL are discussed and a review of stability criteria used to study the stability of dc power systems are reviewed with their merits and limitations. Furthermore, available literature is reviewed to summarize the techniques to compensate the CPL effect. Finally, discussion and recent challenges in the dc distribution systems.

Comprehensive Topological Overview of Rolling Stock Architectures and Recent Trends in Electric Railway Traction Systems

Abstract: This paper reviews the modern electric propulsion architectures and configurations for railway traction, which are currently in practice. The development and advancement of power electronics and digital controllers led to the standardization of the insulated gate bipolar transistor (IGBT)-based converter fed induction motor drives. This paper summarizes the state-of-the-art technology of IGBT-based rolling stock in terms of both power and control. Control hierarchy of traction system and drive control techniques are explored. Special emphasis has been put on the technologies, which can improve energy efficiency as well as reliability to develop high-speed rails and metro trains in the near future in both urban and suburban areas. Specific attention is given to power electronic transformer technology-based traction drives and on-board energy storage systems. In addition, advances in traction drive technology and wide-bandgap power devices are addressed. Finally, major issues faced in rolling stock including the challenges for further improvement are highlighted.

800-V Electric Vehicle Powertrains: Review and Analysis of Benefits, Challenges, and Future Trends

Abstract: Two of the main challenges for electric vehicle (EV) adoption include limited range and long recharge times. Ultrafast charging can help to mitigate both these concerns. However, for typical 400-V battery EVs (BEVs), the charging rate is limited by the practical cable size required to carry the charging current. To reach ultrahigh charge rates of 350 or 400 kW, 800-V BEVs are a promising alternative. However, the design of an 800-V EV requires careful new considerations for all electrical systems. This article reviews the current state of 800-V vehicle powertrain electrical design and performs an analysis of benefits, challenges, and future trends regarding multiple vehicle powertrain components. Specifically, detailed benefits and challenges related to the battery, propulsion motor, inverter, auxiliary power unit, and on- and off-board chargers are discussed.

Circulating Current and ZVS-on of a Dual Active Bridge DC-DC Converter: A Review

Abstract: Dual active bridge (DAB) dc-dc converters have several attractive features including auto-adjust bidirectional power flow, wide voltage gain range, and zero voltage switching (ZVS)-on capability. Various applications based on DAB including solid-state transformer in power grids and traction, energy storage system, and electric vehicle on-board chargers have been proposed by academics. Nevertheless, industrial applications based on DABs are still seldom mainly due to the circulating current and loss of ZVS problems under certain load and voltage gain conditions. There is an intensive research effort underway to solve these problems recently. This paper presents the state-of-the-art view in the cause of circulating current and loss of ZVS and surveys the solutions to these problems.