Common-Mode Voltage Reduction Scheme for MMC with Consideration of Dead Zone

Modular multilevel converter (MMC) has been widely used because of its superior performance. However, the rapid switching of power electronics devices will bring serious electromagnetic interference (EMI). In MMC system with the nearest level modulation (NLM), it is deduced that there is a common-mode voltage (CMV) whose amplitude is one third of the voltage of the capacitor of the sub-module (SM). In this paper, the vector modulation which is nearest to the zero-CMV vector (ZCMVV) in theory can greatly reduce the amplitude of the CMV. However, the dead zone in PWM can bring spikes in CMV and increase the CM EMI. By analyzing the switching state, the introduction of dead zone compensation (DZC) removes most of the peaking of the CMV. Experimental results have been provided to validate the effect of CM EMI mitigation in MMC after deadtime compensation.