A Robust Capacitor Voltage Balancing Method for CPS-PWM-Based Modular Multilevel Converters Accommodating Wide Power Range

Capacitor voltage balancing is one of the most important issues for the safe, reliable, and economical operation of the modular multilevel converter (MMC). This article proposes a modified individual capacitor voltage balancing method for MMCs with phase-shifted carrier pulsewidth modulation (PWM) (CPS-PWM) to solve the problem of the poor dynamic performance that the conventional individual voltage balancing methods suffer at low output power. In the proposed method, the information of arm current is incorporated into the balancing algorithm to cancel out the coupling effect of the output power on balancing control. Compared with conventional balancing methods, the proposed method shows better robustness against varying output power and maintains a good dynamic performance in a wider power range. The complete modeling process and parameter design are presented and considered for system stability. The effectiveness of the proposed method is verified with both MATLAB/Simulink simulation and experimental results.