Two-stage transformerless dual-buck PV grid-connected inverters with high efficiency

A semi-two-stage common-ground-type transformerless dual-buck-based grid-connected inverter is proposed in this paper. The common-ground-type topology can eliminate common mode (CM) leakage current by connecting the negative terminal of the photovoltaic(PV) directly to the neutral point of the grid, which bypasses the PV array's stray capacitance. The dual-buck-based topology guarantees increased robustness since the dc-link cannot be short-circuited by a shoot-through event. The semi-two-stage topology features multi-level characteristic, which has a lower forward-voltage drop and smaller dv/dt. Compared with the conventional two-stage inverter, the proposed topology achieves higher efficiency and higher reliability. Experimental results of a 1.5kW prototype show that the proposed inverter is able to achieve high efficiency and low leakage currents.