Common Mode Leakage Current Analysis of 1ϕ Grid-Tied Transformer Less H-Bridge PV Inverter

Abstract

Grid-connected applications of renewable energy sources(solar energy) are increasing day by day. For these applications, transformers play an important role in facilitating galvanic isolation and suitable voltage ratio for interconnection between grid and inverter. However, the omitting of the transformers from the complete power conversion system becomes inevitable because of having large size/weight and cost. Hence transformerless inverters are replacing conventional inverters for grid-connected PV systems at a rapid pace. It has been observed that a transformerless grid-connected H bridge inverter established a common mode resonant circuit with the formation of parasitic capacitance between PV terminals and grounded frame and hence, consequently, leakage current induced in the system. In this paper, a mathematical model has been derived by using source transformation approach for the common-mode resonant circuit of H bridge grid-connected PV inverter, and further, it has been analyzed for both unipolar and bipolar modulation strategies. Finally, a 1kW grid-connected single-phase H bridge PV inverter has been simulated on Matlab and verified with satisfactory results.