An Isolated Single-Stage Four-Quadrant Inverter With Energy Storage Capacitor

In this paper, a single-stage full-bridge inverter with energy storage capacitor is proposed. The high-frequency transformer is used to achieve boosting voltage and electrical isolation. The energy storage capacitor is introduced in the secondary side and the stored energy is fed back into the bus capacitor through the body diode when energy is fed back reversely. Accordingly when energy flows forward, the energy stored in the bus capacitor is released to reach the energy balance of bus capacitor in each power frequency cycle, and thereby achieve the four-quadrant operation of inverter. Thus, problems of energy being fed back into the DC bus directly and increasing complexity of circuit are avoided. When the inverter is connected to the grid, the bus capacitor can be disconnected from the circuit and a single-phase single-stage grid-connected inverter is achieved. The operating principle and control strategy of the topology are analyzed in detail and the feasibility is proved by experiments.