Unidirectional duck DC-DC converter mode photovoltaic grid-connected inverters with high frequency link

A circuit configuration and circuit topological family of unidirectional buck dc-dc converter mode photovoltaic grid-connected inverters with high frequency link (HFL) are proposed in this paper. Its circuit configuration is composed of the photovoltaic (PV) array, the unidirectional isolated buck dc-dc converter and polarity reversal inverting bridge. The circuit topology, the maximum power point tracking (MPPT) methods, dual-loop PWM control strategy with the input voltage as outer loop and the output current as inner loop, and design criteria for the key circuit parameters are deeply investigated. Taking push-pull forward mode topology as an example, make the photovoltaic power generation experiment on the unidirectional buck dc-dc converter mode photovoltaic grid-connected inverter system with high frequency link. The simulation and experiment results have shown that this kind of inverter have the advantages such as high frequency (HF) electrical isolation, quasi single-stage power conversion, accurate MPPT, low voltage stress and ZVZCS of the power switches in the polarity reversal inverting bridge, high conversion efficiency, high quality grid-connected current etc.