A Nine-Level Grid-Connected Photovoltaic Inverter Based on Cascaded Full-Bridge with Flying Capacitor

This paper proposes a nine-level PWM grid-connected photovoltaic inverter for single-phase applications. The basic structure relies on two cascaded full-bridges supplied with different voltage levels. A flying capacitor provides the power supply for the lower voltage full-bridge. In order to increase the efficiency and keep the ground leakage current under control, a specific PWM strategy was developed and an additional leakage current reduction circuit was added to the basic structure of the cascaded full-bridge. Moreover, the regulation of the flying capacitor voltage is taken into account. Simulations and experimental results confirm the good performance of the proposed solution. © 2012 IEEE.