Suppressing leakage current for cascaded H-bridge converters in grid-tie renewable energy systems

Photovoltaic panels contain parasitic capacitance causing leakage currents in transformerless converters, which raises safety concerns and reduces system performance. This work presents a common-mode equivalent circuit for Cascaded H-Bridge (CHB) converters with symmetrical filter configuration. In this paper, we develop a novel modulation technique for CHB multilevel converter, which can suppress the leakage current. The simulation and experimental results for standard phase shifted pulse width modulation and novel leakage reduction pulse width modulation (LRPWM) are provided. It is found that LRPWM is more effective in suppressing leakage current and conforms VDE-0126-1-1 German leakage current standard.