Capacitor Voltage Balancing Algorithm with Redundant Level Modulation for a Five Level Converter with Reduced Device Count

A new five-level multilevel converter topology with a reduced device count has been brought up for medium-voltage inverter applications. However, as an inherent issue of this simplified topology, the voltage balancing of flying capacitors is challenging. Conventional approach utilizing redundant switching states cannot achieve the balancing under a unity power factor and high modulation indexes. This paper proposes a novel voltage balancing algorithm to solve this issue, which is based on Redundant Level Modulation (RLM). The proposed algorithm is verified by simulation and experiment. This novel voltage balancing scheme overcomes the limitations of the conventional approach and enables this topology to operate at high power factors and high modulation indexes.