Multilevel single-phase rectifier~inverter with cascaded connection of two three-arm converters

The paper proposes a multilevel single-phase rectifier-inverter with the cascaded connection of two three-arm converters. A semisinusoidal PWM switching technique is developed to form a five-level switching pattern on the rectifier side and the inverter side simultaneously. The DC-link voltages of two converters are regulated with one voltage controller. Balance of two DC-link voltages is controlled with a feed-forward adjustment of the PWM control signal. Multiple-loop controller design of the system is presented. The feed-forward-plus-feedback control technique is employed for regulating both the rectifier current and the inverter voltage. A 2 kVA/220 V/60 Hz prototype system is set up and its control circuit is realised based on Matlab real-time control. Effectiveness of the proposed circuits is confirmed with some experimental results