An improved voltage balancing method of modular multilevel converters

In this paper, an improved voltage balancing method of modular multilevel converters (MMCs) is proposed. This method divides sub-modules in same arm into several groups which voltage balancing is based on. The voltage balancing between groups is based on the sorting result of group sub-module average voltage and the voltage balancing within group is based on the sorting result of sub-module voltages in group. The proposed method can save sorting time greatly compared with the conventional method. Simulation results on a MMC based three-phase inverter show validity of the proposed method.