A NOVEL UNITY POWER FACTOR INPUT STAGE WITH RESONANT DC LINK INVERTER FOR AC DRIVES

Abstract

This work describes a novel method in improving the input current total harmonic distortion as well as power factor of a three-phase resonant DC link inverter circuit. In this method, three bidirectional switches comprising MOSFET and four diodes are used across the three-phase supply and load. Also, resonant circuit with small inductor and capacitor is used to reduce the switching losses of the inverter. In a three-phase rectifier only two diodes conduct at any given time. As a result, the current in the third phase is zero. But in this method, the bidirectional switch corresponding to the third phase is turned ON. Once the input voltage crosses zero-voltage axes, the corresponding switch will be triggered. Each bidirectional switch receives a pulse of 30° in width following the zero-crossing point of corresponding phase voltage. The closing of bidirectional switches provides an alternate path for the input current to flow. The analysis and simulation of three phase rectifier with bi directional switches, experimental results of the inverter are also presented in this paper.