Leakage Current Analysis of Grid-Connected Transformerless Photovoltaic Energy Systems

Transformerless inverters are now receiving increased attention in grid-connected solar photovoltaic (PV) systems due to requirements for high power density, efficiency, reliability, and affordability. However, the fluctuation of common-mode voltage between the PV neutral and grid results in leakage current being produced through the stray capacitance between the PV array and the ground. Furthermore, the transformerless inverters experience dc current injection and safety issues, and are prone to system degradation due to a lack of galvanic isolation between the inverter and the grid. This paper aims to provide a comparative analysis of the leakage current mitigation/elimination methods with a focus on proactive measures in the form of inverter topology modifications and/or modulation techniques in transformerless PV systems. The leakage current of each inverter topology is assessed holistically through simulation studies in MATLAB/Simulink software. Finally, the merits and demerits of each transformerless inverter topology with the developed modulation scheme are summarized.