Ground leakage current elimination in a transformerless unipolar modulation based single phase grid-connected photovoltaic system

Unipolar sinusoidal pulse width modulation (SPWM) full-bridge inverter poses advantages such as higher dc voltage utilization, smaller current ripple in the filter inductor, and higher processing efficiency. However, unipolar SPWM full-bridge inverter causes time varying common-mode voltage. The variable common-mode voltage excites leakage current through the parasitic capacitance between the PV array and the ground, which restricts its application in transformerless grid-connected photovoltaic (PV) inverter. In order to solve this problem, an optimized full-bridge topology is proposed in this paper. The topology uses an additional branch to be clamped the potential of the freewheeling path to the half of the input voltage in the freewheeling period, which guarantees no variable common-mode voltage in the unipolar SPWM full-bridge inverter. The proposed topology poses advantages such as higher efficiency, simple switching, and topological simplicity as compared to existing topologies. The proposed topology has been verified in MATLAB/Simulink environment with satisfactory results.