A Seven-Level Switched Capacitor Inverter Using Series/Parallel Conversion With Reduced Number Of Switches

This paper proposes a new seven-level inverter for PV-module-integrated single-phase inverters. The proposed circuit consists of an h-bridge inverter with a switched-capacitor step-up converter. The switched capacitor converter supplies a three-level voltage to the input terminal of the h-bridge inverter and thus the line-to-line voltage of the h-bridge inverter becomes 7 levels. This makes it possible to reduce the switching ripple in the ac current resulting in the reduction of the ac filter capacity. Also, level-and phase-shifted pulse-width modulation is applied to this inverter. This PWM method enables the reduction of the voltage ripple of the switched capacitors hence small capacitance. Finally, this paper confirms the validity of the proposed circuit and the PWM methods using an experimental system.