A CB-PWM Technique for Eliminating CMV in Multilevel Multiphase VSI

Abstract

A generalized Carrier-Based Pulse Width Modulation (CB-PWM) scheme is proposed here for the elimination of common-mode voltage (CMV) in a multilevel multiphase voltage source inverter (VSI). In this CB-PWM scheme, the switching function of x-level, q-phase VSI is obtained from the switching function of virtual y-level and (y+1) level, q-phase VSI, where y = (x+1)/2 when x is odd and y = x/2 when x is even. It is established here that the pole voltages of q-phase x-level VSI thus obtained generate zero CMV. The proposed CB-PWM technique is computationally less intensive and hence can be easily implemented in hardware. Extensive simulation and experimental results are presented to validate the proposed CMV elimination technique in 3-phase 7-level VSI, 5-phase 5-level VSI, and 6-phase 4-level VSI. A comparative study of the proposed PWM scheme with the existing technique shows the superiority of the proposed technique in eliminating CMV.