Photovoltaic Power System Leakage Current Reduction by Paralleled Inverters

This paper introduces the modulation method for paralleled inverters to reduce the leakage current through achieving zero Common-Mode (CM) voltage of the transformerless Photovoltaic (PV) grid-connected systems. PV arrays are tied to paralleled inverters, which are interconnected to the grid via coupling inductors. The reference Voltage Vector (VV) and the paralleled VV are combined based on VV in each inverter. Zero-CM voltage is attained by distributing the action time to each inverter. The proposed Pulse-Width Modulation (PWM) approach guarantees that the voltages for both inverters are in equilibrium during every switching cycle; the circulating current between the paralleled inverters is limited by a small value of coupling inductance. The PWM method has the benefit of reducing CM leakage current, and output current ripples. Simulation and experimental results of the proposed method are provided, validating its ability to eliminate CM voltage and suppress the CM leakage current.