Control of the Modular Multi-Level Converter for minimized cell capacitance

The Modular Multi-Level Converter (M2C) is an emerging multi-level topology for medium-voltage inverters. The drawback of this topology is the high expense on capacitors in the inverter cells. This paper describes a method to minimize the required cell capacitance for a given point of operation (modulation index, displacement factor) by means of injecting harmonics into the circulating current. The required cell capacitance is significantly reduced by the proposed method.