Low Leakage Current Transformerless Three-Phase Photovoltaic Inverter

In a transformerless inversion system, the suppression of common mode leakage current is one of the most important issues concerned. Several single phase full bridge PV inverters have been proposed to eliminate the leakage current. However, in the three phase applications of the PV inverters, few attentions have been paid on the improvement of leakage current from a topological point of view. This paper focuses on the reduction of common mode voltage in three phase transformerless inverter. Firstly, the common mode characteristic of the three phase inverter is analyzed. Then, a kind of novel three phase topology is proposed to suppress the common mode voltage. Also, the NPC circuit can be added to the novel topology in order to further reduce the common mode voltage. The novel topology has the advantages of fewer device cost and lower conduction losses compared to the traditional three phase NPC topologies. Finally, the simulation and experimental results illustrated the theoretical findings.