A wide-gain quasi-Z-source switched capacitor multi-level voltage source inverter

Renewable energy such as wind power, photovoltaics require power inversion to generate stable AC voltage for connection to loads or the grid. As a core device in renewable energy power conversion systems, inverters are required to meet the application demands of high efficiency, high power density, and wide-range adjustable voltage gain. Traditional H-bridge inverter suffers from a high total harmonic distortion (THD) of the output AC voltage and no boosting capability. Recently the switched-capacitor multi-level inverter (SCMLI) excels in applications like renewable energy due to its high gain, self-balancing capabilities, low device voltage stress, and minimal output voltage harmonics. However existing SCMLIs are limited by their weak voltage modulation and high peak input pulse current. A novel quasi-Z-source single-phase SCMLI is proposed in this paper, offering a wide adjustable input voltage range, continuous and pulse-free input current, and scalability. Compared to similar topologies, the proposed topology requires fewer components and lower voltage stress, enabling direct conduction of the power switches in the output bridge arm of the quasi-Z-source circuit and supporting a wider input voltage range. Firstly, the working principle and parameter design method of the proposed topology are introduced. Based on this, the prototype system parameters are determined, and the correctness of the theoretical analysis is verified through simulation and experiments. The results indicate that the proposed topology can output high-quality seven-level AC with a wide input voltage range. The THD is as low as 23.8%, significantly lower than that of traditional two-level inverters, effectively improving the output power quality and reducing the size of the output filter.