Discontinuous Space Vector Pulse Width Modulation for Six Switch Converter with Independent Control of Phase Voltages and Switching Device Stress Alleviation

Abstract

Along with high efficiency at increased operating frequencies, high power density has become a critical consideration in many applications of power electronic converters. High power density is more readily obtained by reduce components counts in the power electronic converters. The six-switch converter is one of such converters with reduced component count. With this converter however, there are issues of interdependence of phase voltages, unbalance and increased stresses on the switching devices and DC bus voltage underutilization. This paper presents a discontinuous PWM method that addresses these issues and thereby makes the reduction in switch count without the need to overdesign the switching device rating. An algorithm is presented that ensures independent control of phase voltages. With the aid of three zero vector partitioning parameters, voltages are injected to the reference signals that alleviates the unbalance in the switching stresses of the devices. Moreover, the zero vector partitioning parameters are also used for discontinuous PWM generation. The linear region DC bus voltage utilization is improved with the method. The case of over modulation of the converter is also explored. The over modulation scheme is obtained by the determination of a reference voltage location parameter.