Analysis of modular multilevel converter capacitor voltage balancing based on phase voltage redundant states

This study provides mathematical analysis for the pulse width modulation and capacitor voltage balancing of a three-level modular converter, using voltage phase redundant states. Simulation and experimentation validate the analysis presented and highlight the distinct features of the modulation and capacitor voltage balancing strategies used in terms of effective switching frequency per device, device current and voltage stresses compare to other methods in the literature. The study also presents a simple modulation strategy that can be used in conjunction with the presented capacitor voltage balancing strategy for modular multilevel converters with a large number of cells per arm.