Modulation Strategy for Minimization of Leakage Current in Grid-Connected PV Panels

This paper presents a switching strategy for the cascaded multilevel H bridge inverter of five levels to reduce the leakage current in the grid-connected transformerless PV system. Minimization of the leakage current in solar panels is vital in transformerless grid-connected PV panels. But due to the absence of transformers which provide galvanic isolation, CMV techniques are applied to reduce leakage currents from PV panel to ground. This current causes hazards to humans and large currents above 300mA may lead to fire hazards. The proposed switching strategy reduces the continuous transients at switches, hence avoiding high frequency switching. This switching technique requires only a single modified carrier wave for all 2m+1 levels of operation. The sinusoidal carrier waveform is modified as a humped sinusoidal waveform with to reduce switching losses. In this paper, the switching strategy with the modified sinusoidal carrier has been incorporated to PV fed five level multilevel inverters connected to the grid and its effectiveness has been validated.