An Efficient Single-Sourced Asymmetrical Cascaded Multilevel Inverter with Reduced Leakage Current Suitable for Single-Stage PV Systems

초록

An isolated single sourced multi-output dc/dc converter with a high-frequency link was proposed before to feed different cells of the Asymmetrical Cascaded H-bridge inverter. One of the ACHB fundamental advantages is that the main H-bridge is commutated with fundamental frequency, passing the majority of the inverter power. However, the isolated DC/DC converter needs to be connected to the main voltage source with high-voltage/high-frequency switches, which limits the power capability and the efficiency. In this paper, a switching pattern based on nearest level modulation method is proposed to command all the power to be transferred through the main H-bridge. Therefore, the power circulates between the auxiliary H-bridges with no need for high voltage switches. As a result, the auxiliary converter is needed with only 5% of the power rating. This solution improves cost, size, and the efficiency. Furthermore, the architecture makes the inverter more suitable for high power, high voltage applications. The inverter switching strategy is based on programmable firing angles. The grid connected inverter main dc-link is controlled to achieve maximum power point tracking, while the isolated converter is controlled to regulate the auxiliary DC-links. The proposed topology was verified by simulation and experimental results through around 1.5-kW hardware prototype. IEEE

키워드