A three-phase voltage-source neutral-point-clamped converter with divided capacitors

Abstract

A new method for reducing harmonics involved in ac line currents of a three‐phase voltage‐source converter is proposed. It is applied to the conventional neutral‐point‐clamped inverter. By dividing a smoothing capacitor into four elements and adding four auxiliary switching devices, the input line‐to‐line voltages of the proposed converter can be made to have almost the same waveforms as a conventional 18‐phase rectifier with 18 devices and three input transformers. In this paper, circuit performance and input voltage waveforms are discussed, and the optimum parameters are determined. Effects of harmonic reductions can be clarified by theoretical results. We suggest several output voltage adjustment methods. Characteristics of power factors and distortion factors in these methods are theoretically and experimentally investigated. © 1997 Scripta Technica, Inc. Electr Eng Jpn, 121(2): 72–82, 1997