A novel capacitor voltage balancing method for distributed switching frequency in a modular multilevel converter

This paper proposes a novel capacitor voltage balancing method for a modular multilevel converter in order to make a switching frequency of sub-module converter evenly distributed, while maintaining the voltage balance within a desired range. Similar to the conventional, the proposed method is based on the sorting algorithm which is widely used due to its simple and effective implementation, but introduces double target bands, voltage deviation band and switching commutation band, to avoid unevenly increased switching commutation. Several simulation results are provided to verify the effectiveness of the proposed method.