Analysis and Suppression of Leakage Current in Cascaded-Multilevel-Inverter-Based PV Systems

The transformerless cascaded multilevel inverter (CMI) is considered to be a promising topology alternative for low-cost and high-efficiency photovoltaic (PV) systems. However, the leakage current issue resulted from the parasitic capacitors between the PV panels and the earth remains a challenging in designing a reliable CMI-based PV system. In this paper, the leakage current paths in PV CMI are analyzed and the unique features are discussed. Two filter-based suppression solutions are then presented to tackle the leakage current issue in different PV CMI applications. Simplified leakage current analytical models are derived to study the suppression mechanisms and design the suppression filters. Study cases are demonstrated for each of the solutions with filter design example, simulation and experimental verifications.