Improvements in voltage source PWM converter for induction motor drive system with chopper

Abstract

The purpose of the work in this paper is to improve the characteristics of the three-phase voltage source PWM converter. In this type of converter, the input current waveform is controlled by a PWM converter using an optimum fixed voltage modulation factor, where the input current waveform takes an optimum value. The input voltage of the inverter is adjusted by the chopper circuit. When the voltage modulation factor is extended to the over-modulation region in a three-phase voltage source PWM converter, the number of switching operations is much reduced, which is advantageous for larger capacities. With respect to the distortion factor of the input current in the PWM converter, the characteristics do not deteriorate, even in the over-modulation region at about a=1.6 to 1.8 or so. The results are discussed and shown to be applicable to a PWM converter/inverter system for induction motor drives.