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 onverter 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, input line-to-line voltages of the proposed converter can be almost the same waveforms as a conventional 18-phase rectifier with 18 devices and three input transformers.
In this paper, circuit performances and input voltage waveforms are discussed, and the optimum parameters are determined. Effects of harmonic reductions can be clarified by theoretical results. Then, we suggest several adjusting methods of the output voltage. Characteristics of power factors and distortion factors in these methods are theoretically and experimentally investigated.