Variable-Angle Voltage Balancing Control for Four-Level Converters

Capacitor voltage balancing issue of four-level converters has been a big challenge since they were born. Until now, there are several kinds of voltage balancing control methods, including model predictive control, virtual vector space vector pulse width modulation, overlapped carrier modulation, variable-carrier modulation, and variable-reference modulation. In this paper, a new method called variable-angle voltage balancing control is proposed. It realizes closed-loop control for the middle capacitor voltage based on regulating the phase shift angle of the reference modulation signals. Simulation studies have been carried out to verify the proposed variable-angle voltage balancing method for four-level converters.