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 micro-inverter. The proposed system comprises an isolated high-gain DC-DC converter and a single-phase grid-tied inverter. The high-gain 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 DC-DC converter control is realized by implementing the maximum power point tracking (MPPT) algorithm combined with one-cycle 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 real-time 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.