Common-Mode Voltage Suppression Based on Insertion Indices Modification for Modular Multilevel Converters

Modular multilevel converter (MMC) is an attractive topology for high/medium voltage applications and motor drives applications because of its performance, modularity, and scalability. During operation, the MMC, which is composed of the voltages of several submodules (SMs), may be affected by a common mode voltage (CMV) generated by switching state changes. This causes increased electromagnetic interference (EMI) in the system as well as leakage current, which affects the converter's efficiency and durability. To suppress the CMV, this paper presents a method to eliminate the CMV for MMC modulated by nearest level modulation (NLM). The key approach is to modify the insertion indices before the modulation scheme to keep the equal inserted SMs between the upper and lower arm. The proposed method for eliminating CMV is simple to implement and suited for increasing the number of SMs in each arm. The simulation results show the effectiveness of the control scheme presented in PLECS software.