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Two-stage single-phase photovoltaic grid-tied micro-inverter using soft-switching techniques

This paper presents a novel micro-inverter topology for a single-phase grid-connected photovoltaic (PV) system which is based on two stages. The first stage is forward-flyback DC-DC isolated high step-up converter for achieving high voltage gain and efficiency while the second stage is the soft switching full bridge inverter. The full-bridge DC/AC inverter is implemented with one leg operating in high frequency and the other operating in line frequency to reduce the switching losses. The control technique is based on a boundary conduction mode (BCM), where zero-voltage switching (ZVS) is achieved without using additional devices or magnetic components. The performance of proposed hybrid architecture is assessed using Power Simulation (P-SIM) software. The results indicate that overall micro-inverter efficiency of 95.5% is achieved. A 250W 220VAC single-phase prototype was built and experiments. The proposed soft switching control technique is easy to be implemented in a DSP and the inverter has increased power density, smaller size, and high reliability.