Multilevel Common-Ground Transformerless Inverter for Photovoltaic Applications

Transformerless inverters have attracted great attention since they became a compact and economic solution for photovoltaic (PV) generation systems. On the other hand, the common-mode (CM) leakage current issue needs to be addressed in order to meet safety requirements. This article proposes a new multilevel common-ground inverter for transformerless systems. The leakage current is eliminated by the electric connection between the grid neutral point and the PV negative terminal. Furthermore, the operation modes of the proposed inverter, as well as the design guidelines, are analyzed in detail. In addition, a feedforward modulation strategy to decouple the output variables from the voltage-capacitor oscillations is proposed. Experimental results are presented to verify the performance and practicability of the proposed inverter in grid-connected operation.