Single-stage AC module with series power decoupling capability for connecting PV to a single-phase power grid.

In single-phase grid-connected photovoltaic inverters, the input power is constant during the grid period, whereas the output power oscillates at double-line frequency. Therefore, electrolytic capacitors are widely used to handle the input and output power differences. However, these capacitors have short lifetime which degrade the inverter reliability. This paper proposes a control strategy to turn a conventional four-switch flyback-based inverter to an inverter equipped with a series power decoupling circuit. Therefore, a long lifetime film capacitor can be used as the main energy storage. The modified inverter has an inherent snubber circuit, which can restore energy of the transformer leakage inductance and improves its overall efficiency. The control strategy can realise maximum power point tracking and inject a sinusoidal low total harmonic distortion current to the grid. A 100 W prototype inverter has been built to verify operation and feasibility of the proposed control strategy. [ABSTRACT FROM AUTHOR]