Hengchun Mao

Bio: Hengchun Mao is an academic researcher from Bell Labs. The author has contributed to research in topics: Thyristor & Voltage source. The author has an hindex of 3, co-authored 3 publications receiving 384 citations.

Review of high-performance three-phase power-factor correction circuits

Abstract: This paper reviews progress in topology, control, and design aspects in three-phase power-factor correction (PFC) techniques. Different switching rectifier topologies are presented for various applications. Representative soft-switching schemes, including zero-voltage and zero-current switched pulsewidth modulated (PWM) techniques, are investigated. Merits and limitations of these techniques are discussed and illustrated by experimental results obtained on prototype converters. Control and input filter design issues are also discussed.

Improved zero-current transition converters for high power applications

Abstract: Existing zero-current transition (ZCT) converters do not solve main switch turn-on problems and require auxiliary switches to be turned off with high current and, therefore, are not suitable for high-power applications. Novel ZCT schemes proposed in this paper enable all main switches and auxiliary switches to be turned on and off under zero-current conditions. The zero-current switching at both turn-on and turn-off not only reduces switching losses significantly, but also eliminates the need for passive snubbers, due to the much reduced switch stress. The cost of the auxiliary switches can he reduced compared to the existing ZCT schemes, due to their zero-current turnoff. The proposed technology is well suited for DC-DC and three-phase converters with insulated gate bipolar transistors (IGBTs), MOS-controlled thyristors (MCTs), and gate-turnoff switches (GTOs). Theoretical analysis, computer simulation, and experimental results are presented to explain the proposed schemes.

Novel soft switched three-phase voltage source converters with reduced auxiliary switch stresses

Abstract: This paper proposes new three-phase ZVT topologies. With a split DC link, the auxiliary switch voltage rating is reduced to half DC-link voltage, so the conduction loss and switching loss in the auxiliary circuit are significantly reduced compared to previous ZVT circuit. With the ZVT circuit reducing main switch turn-on loss, the converter can be operated at high switching frequencies efficiently and reliably, achieving higher power density and better control performance. Simulation and experimental results are presented to verify the analysis.

Dynamically Reconfigurable Motor Technology for High Density and High Efficiency HEV Drives without Rare-Earth Materials

Abstract: Dynamically reconfigurable motor (DR Motor) technology is an integrated drive with fast and smooth adjustment of pole numbers of induction motors, to obtain a high torque at low speed without sacrificing efficiency and power rating at high speed. The DR motor is designed to generate torque efficiently at multiple harmonics corresponding to multiple pole numbers, and its magnetic circuit is decided by the highest-pole-count configuration for high torque density. A low-pole-count-configuration for normal operation achieves high efficiency and high power density across a wide speed range. FEA simulation shows close to 50% torque/power density improvements compared with state-of-the-art induction motors in electrical and hybrid traction drive applications.

A review of single-phase improved power quality AC-DC converters

Abstract: Solid-state switch-mode rectification converters have reached a matured level for improving power quality in terms of power-factor correction (PFC), reduced total harmonic distortion at input AC mains and precisely regulated DC output in buck, boost, buck-boost and multilevel modes with unidirectional and bidirectional power flow. This paper deals with a comprehensive review of improved power quality converters (IPQCs) configurations, control approaches, design features, selection of components, other related considerations, and their suitability and selection for specific applications. It is targeted to provide a wide spectrum on the status of IPQC technology to researchers, designers and application engineers working on switched-mode AC-DC converters. A classified list of more than 450 research publications on the state of art of IPQC is also given for a quick reference.

Multipulse AC–DC Converters for Improving Power Quality: A Review

Abstract: Three-phase multipulse AC-DC converters (MPC) are developed for improving power quality to reduce harmonics in AC mains and ripples in DC output. This paper deals with the multipulse AC-DC converter configurations, state of art, their performance, power quality aspects, components selection considerations, latest trends, future developments, and potential applications. It is targeted to provide broad perspective on multipulse converter technology to the researchers, engineers, and designers dealing with them. A classified list of more than 250 research publications on the subject is also given for quick reference.

State-of-the-art, single-phase, active power-factor-correction techniques for high-power applications - an overview

Abstract: A review of high-performance, state-of-the-art, active power-factor-correction (PFC) techniques for high-power, single-phase applications is presented. The merits and limitations of several PFC techniques that are used in today's network-server and telecom power supplies to maximize their conversion efficiencies are discussed. These techniques include various zero-voltage-switching and zero-current-switching, active-snubber approaches employed to reduce reverse-recovery-related switching losses, as well as techniques for the minimization of the conduction losses. Finally, the effect of recent advancements in semiconductor technology, primarily silicon-carbide technology, on the performance and design considerations of PFC converters is discussed.

Review of high-performance three-phase power-factor correction circuits

Abstract: This paper reviews progress in topology, control, and design aspects in three-phase power-factor correction (PFC) techniques. Different switching rectifier topologies are presented for various applications. Representative soft-switching schemes, including zero-voltage and zero-current switched pulsewidth modulated (PWM) techniques, are investigated. Merits and limitations of these techniques are discussed and illustrated by experimental results obtained on prototype converters. Control and input filter design issues are also discussed.

A Systematic Topology Evaluation Methodology for High-Density Three-Phase PWM AC-AC Converters

Abstract: This paper presents a systematic evaluation approach of three-phase pulsewidth-modulated (PWM) AC-AC converter topologies for high-density applications. All major components and subsystems in a converter are considered and the interdependence of all the constraints and design parameters is systematically studied. The key design parameters, including switching frequency, modulation scheme, and passive values, are selected by considering their impacts on loss, harmonics, electromagnetic interference (EMI), control dynamics and stability, and protection. The component selection criteria as well as the physical design procedures are developed from the high-density standpoint. The concept of using the same inductor for harmonic suppression and EMI filtering is introduced in the design. With the proposed methodology, four converter topologies, a back-to-back voltage source converter (BTB-VSC), a nonregenerative three-level boost (Vienna-type) rectifier plus voltage source inverter (NTR-VSI), a back-to-back current source converter (BTB-CSC), and a 12-switch matrix converter, are analyzed and compared for high specific power using SiC devices. The evaluation results show that with the conditions specified in this paper, BTB-VSC and NTR-VSI have considerably lower loss, resulting in higher specific power than BTB-CSC and the matrix converter. The proposed methodology can be applied to other topologies with different comparison metrics and can be a useful tool for high-density topology selection.