Coupled Inductor-based Soft-switched Boost-Ćuk Converter for Microinverter Applications

In this study, a novel fully soft-switched high step-up dc-dc converter is proposed. The proposed converter comprises the integration of boost and Ćuk converters with the same input inductor and MOSFET, and series-connected output dc-link voltages. In this topology, the switch is turned on under zero current switching and low-voltage conditions since the converter works under discontinuous conduction mode due to small output Ćuk inductance. In addition, two coupled inductors are applied to create a similar voltage gain and soft switching conditions for all semiconductor elements. The first coupled inductor is placed in series with the Ćuk diode, which provides a balanced dc-link for wide load and input voltage variations and ZCS conditions for the Ćuk diode. The second coupled inductor forms a lossless passive snubber to provide a zero-voltage switching turn-off condition for the main switch. This lossless passive snubber provides a clamped circuit and reduces the turn-off slew rate of the switch voltage. This snubber circuit is simple with minimum elements, and the snubber capacitor discharges to the output while the switch is OFF. Moreover, the input current is ripple-free, which is appropriate for renewable energy systems integration. The experiments substantiate the effectiveness of the proposed converter.