Carrier Phase Shift Modulation for Reducing the Common Mode Voltage in a Two-Level Three-Phase Inverter

Due to the ever increasing use of Variable Frequency Drives (VFDs) which involves fast switching converters, focus on reducing the Common Mode Voltage (CMV) is picking up pace. Moreover, the application of SiC power electronics switches, which can switch at much higher switching frequencies than conventionel IGBTs, has refocused the attention on converter redesign to mitigate EMI/EMC issues. The reduction in CMV is necessary to limit the Common Mode Currents (CMC) which in turn reduces the inverter induced bearing currents and shaft voltage. This paper introduces a new scheme, which modulates the shift in the carrier wave for eliminating the highest peaks in CMV. Design, analysis, and simulations have been performed and will be discussed here in details. This new method is compared with the conventional PWM methods and to other similar methods for reducing CMV.