Novel scheme for Zero Voltage Switching of single stage photovoltaic micro-inverter

A novel Zero Voltage Switching (ZVS) approach to improve the efficiency of a single-stage grid connected flyback inverter is proposed in this paper. The proposed scheme eliminates the need for any additional auxiliary circuits to achieve soft-switching. ZVS of the primary switch is realized by allowing negative current from the grid-side through bidirectional switches placed on the secondary side of the transformer. The negative current discharges the MOSFET's output capacitor thereby allowing ZVS turn-on of the primary switch. Therefore, the switching losses of the bi-directional switches are negligible. In order to optimize the amount of reactive current required to achieve ZVS, a variable frequency control scheme is implemented over the line cycle. A 250W prototype was implemented to validate the proposed scheme. Experimental results confirm the feasibility and superior performance of the converter compared to the conventional flyback inverter.