Voltage Balancing Control Strategy of MMC Based on Flying Capacitor Sub-module

A voltage control strategy for flying capacitor sub-module (FCSM) based modular multilevel converter (MMC) was proposed to solve the problem of voltage balancing. Operation principles of MMC and FCSM were analyzed and modulation scheme of the system was determined. The modulation signals were adjusted according to energy sharing and voltage balancing scheme, thus realizing the tracking regulation of the sub-modules' capacitor voltage, and the dynamic voltage characteristic of all the capacitors applied in the system were ensured. Simulation results based on PSCAD/EMTDC show that the proposed control strategy can realize the voltage balancing of FCSM, improving the stability of the DC voltage.