Constant Speed Voltage Balancing Method for Modular Multilevel Converter Under Phase-Shifted Pulsewidth Modulation

Abstract

This paper proposes a novel voltage balancing method for Modular Multilevel Converter (MMC) under Phase- Shifted Carrier Pulsewidth Modulation (CPS-PWM). For the existing individual voltage balancing methods, an unsolved problem is that the active power transmission will greatly affect the balancing speed of MMC system. By utilizing the output current amplitude information, the effect of working condition on voltage balancing is canceled out in the proposed method. Compared with conventional voltage balancing methods, the proposed method possesses good dynamic performance under different working conditions even when the active power is extremely low. Simulation results are provided to validate the effectiveness of the proposed voltage balancing method.