An Optimized Capacitor Voltage Balancing Method for Modular Multilevel Converter

The problem of voltage balancing among the submodules (SM) in modular multilevel converter (MMC) urgently needs to be solved. This paper compares traditional voltage balancing method with the sorting method based on two maintaining factors in terms of voltage balancing effects and switching frequency. Upper limits of voltage difference are set in a gesture to combine these two methods, which can realize the balance between voltage balancing effects and switching frequency. The model of MMC with 20 submodules on each arm is realized by MATLAB/Simulink, and the improved method is verified. The simulation results demonstrate that the improved method is reasonable and effective. (paper)