A Multilevel Transformerless Inverter Employing Ground Connection Between PV Negative Terminal and Grid Neutral Point

For the safe operation of transformerless grid connected photovoltaic (PV) inverters, the issue of common mode (CM) leakage current needs to be addressed carefully. In this paper, a novel multilevel transformerless inverter topology is proposed, which completely eliminates CM leakage current by connecting grid neutral point directly to the PV negative terminal, thereby bypassing the PV stray capacitance. It provides a low-cost solution consisting of only four power switches, two capacitors, and a single filter inductor. As compared to half-bridge topologies, with this inverter a minimum of 27% and maximum of 100% more output voltage is obtained for the same dc-link voltage. The proposed inverter is analyzed in detail and its switching pattern to generate multilevel output while maintaining the capacitor voltage is discussed. Simulations and experiments results confirm the feasibility and good performance of the proposed inverter.