Ground Leakage Current Mitigation for Three-Phase Current Source Inverters

This paper presents a simple solution for ground leakage current mitigation applicable to transformerless three-phase Current Source Inverter (CSI). The proposed solution is addressed only for CSI topology with an additional seventh switch, in literature named CSI7 (or H7), in particular with the splitting of the DC input inductance. In this paper the solution is applied to grid-connected converters for string photovoltaic applications. The proposed approach is to provide an internal return path from the wye-connected capacitors of the output CL filter. Thanks to CSI7 topology and modulation technique, this additional return path is able to significantly reduce the ground leakage current without adversely affecting power conversion efficiency and THD. The performance of the proposed solution is assessed by numerical simulations in case of strings with a different number of PV modules. Simulation results and preliminary experimental validation show that the proposed solution is able to strongly reduce the ground leakage current.