PELS 1999 Prize Paper Awards

An Active Circuit for Cancellation of Common-Mode Voltage Generated by a PWM Inverter

Satoshi Ogasawara (SM) is with the Department of Electrical Engineering, Okayama University, Okayama, Japan.

Hideki Ayano is with Hitachi, Ltd, Hitachi, Japan

Hirofumi Akagi (F) is with the Department of Electrical Engineering, Okayama University, Okayama, Japan.

Abstract: This paper proposes an active common-noise canceler (ACC) that is capable of eliminating the common-mode voltage produced by a pulsewidth modulation (PWM) inverter. An emitter follower using complementary transistors and a commonmode transformer are incorporated into the ACC, the design method of which is also presented in detail. Experiments using a prototype ACC, whose design and construction are discussed in this paper, verify its viability and effectiveness in eliminating common-mode voltage in a 3.7-kW induction motor drive using an insulated gate bipolar transistor (IGBT) inverter. Some experimental results show that the ACC makes significant contributions to reducing a ground current and a conducted electromagnetic interference (EMI). In addition, the ACC can prevent an electric shock on a nongrounded motor frame and can suppress motor shaft voltage.

Inductor Commutation Soft-Switched PWM Inverter Driven by Frequency-Modulated PWM Signal

Michihiko Nagao (M) is with the Energy Electronics Laboratory, Kumamoto Institute of Technology, Kumamoto, Japan.

Koosuke Harada (F) is with the Energy Electronics Laboratory, Kumamoto Institute of Technology, Kumamoto, Japan.

Abstract: This paper presents a novel technique using frequency modulation (FM) to improve the efficiency of an inductor commutation soft-switched pulse-width-modulation (PWM) inverter (ICSI). In ICSI, a circulating current for soft switching always flows through the switches of the inverter independent of the load and input signal. The circulating current significantly deteriorates the efficiency of ICS1. With the FM technique, the circulating current is effectively sup-pressed without sensing any current or voltage in the inverter. Efficiencies of ICSI and ICSI with FM (FM ICSI) are analyzed and verified experimentally. As a result, the efficiency of FM ICSI rises about 20%-40% compared with ICSI.

A Three-Phase Multilevel Converter for High-Power Induction Motors

Nikolaus P. Schibli is with the Swiss Federal Institute of Technology, Lausanne, Switzerland.

Tung Nguyen is with the Swiss Federal Institute of Technology, Lausanne, Switzerland.

Alfred C. Rufer is with the Swiss Federal Institute of Technology, Lausanne, Switzerland.

Abstract: A new converter topology for drives is presented in this paper - a three-phase multilevel converter with separately regulated dc power supplies. The dc voltages are provided by medium-frequency dc-dc converters. The applica-tions for the converter are especially high-power traction systems, where the volt-age applied to the induction motor is bigger than I kV. The motor current is of a very high quality, compared to a classical three-phase converter. This allows keep-ing the switching frequency low by using phase-shifted pulsewidth modulation (PWM) carriers. Different modulation methods have been developed and simulated. Experimental tests have been made on a 12-kW prototype.