HERIC-Based Cascaded H-Bridge Inverter for Leakage Current Suppression in PV Systems

Leakage current can flow through the transformerless photovoltaic (PV) systems because of no galvanic isolation. This undesirable current results in more losses, electromagnetic interferences, and total harmonic distortion. This article presents a hardware-based method to suppress the leakage current in transformerless cascaded H-bridge (CHB) based PV systems. The proposed scheme uses high-efficient and reliable inverter concept in CHB converters for the first time. Using this idea and proper utilization of ac-side filters leads to leakage current suppression in individual cells and, thus, the whole system. In contrast to the most existing solutions, the proposed technique can be easily extended to CHB inverters with an arbitrary number of voltage levels. Moreover, this solution is applicable in the system's conditions with unequal parasitic capacitances and unequal dc-link voltages of H-bridge cells. The validity of the proposed solution is verified by several simulations in the PSCAD/EMTDC environment. Then, the experimental results on a five-level CHB inverter are presented to confirm the theoretical and simulation results.