Push-Pull Based Grid-Tied Micro-Inverter for Photovoltaic Applications

This paper presents the design, modeling, and control of a solar photovoltaic (PV)-based two-stage grid-tied microinverter. The proposed system comprises an isolated high-gain DC-DC converter and a single-phase grid-tied inverter. The highgain converter is implemented using a quasi-switched boost, switched capacitor (qSB-SC) topology, and a push-pull circuit. The high-frequency transformer in this converter enhances gain. In addition, it provides isolation between the first-stage PV circuit and the grid connection, addressing safety concerns. The DCDC converter control is realized by implementing the maximum power point tracking (MPPT) algorithm combined with onecycle control (OCC). Synchronization with the grid is realized using an H-bridge inverter with an LCL filter in the second stage. The operation of a 250 W qSB-SC high-gain DC-DC converter is verified experimentally. The performance of the two-stage PV-based micro-inverter system with all control logic is validated through the MATLAB/Simulink tool, and its realtime applicability is confirmed using the OPAL-RT platform. The experimental and real-time validated results concur well with accepted IEEE/IEC standards. The proposed micro-inverter exhibits (i) maximum power extraction, (ii) galvanic isolation, (iii) high voltage gain, and (iv) grid synchronization.