Single-phase common mode transformer-less soft-switching grid-connected inverter with eliminated leakage current

In this paper, a single-phase single-stage soft-switching transformer-less grid-tied common mode inverter is proposed, which is useful for injection of power from the photovoltaic (PV) panels to the grid. One of the output ports of the PV panel in the proposed topology can be connected directly to the neutral point of the grid to eliminate the leakage current. The proposed topology has buck-boost ability, besides soft switching capability to have a proper efficiency. Furthermore, the proposed converter can operate in unity power factor, therefore the proposed converter has most of the features needed for a PV inverter. A full analysis of the converter is done. Also, a suitable switching algorithm for correct operation of the converter is presented. Moreover, the design technique for the passive elements of the topology is demonstrated. The voltage gain of the converter is calculated. The leakage current of the proposed inverter due to the low- and high-frequency voltage ripple of the PV panel has been discussed. Simulation results in PSCAD EMTDC plus experimental results from a laboratory prototype are added to substantiate the theoretical results. Eventually, a comprehensive comparison study is presented to compare the proposed topology with the most similar converters.