An Improved Phase-Shifted PWM for a Five-Level Hybrid-Clamped Converter With Optimized THD

Five-level hybrid-clamped converter is a newly proposed topology, which is suitable for medium-voltage high-power conversions without switches directly connected in series. Phase shifted pulsewidth modulation (PWM) or (PSPWM) is commonly used to control this converter. However, the line voltages of PSPWM include many zones in which the synthetic voltage jumps two voltage levels continuously, which will deteriorate the harmonic performance and increase the current ripples. This article presents an improved PSPWM method for the hybrid five-level converter, which can imitate the effect of phase disposition PWM and improve the quality of the line voltage and current. A decoupled capacitor voltage balancing control is also implemented based on this modulation method. Simulation and experimental results are presented to demonstrate the feasibility of this method.