Leakage current evaluation of a single-phase transformerless PV inverter connected to the grid

For low-power grid connected applications a single phase converter can be used. In PV applications it is possible to remove the transformer in the inverter in order to reduce losses, costs and size. Galvanic connection of the grid an the DC sources in transformerless systems can introduce addition leakage currents due to the earth parasitic capacitance. This currents increase conducted and radiated electromagnetic emissions, harmonics injected in the utility grid and losses. Amplitude and spectrum of leakage current depends on the converter topology, on the switching strategy and on the resonant circuit formed by the ground capacitance, the converter, the AC filter and the grid. In this paper, the leakage current in a 1.5 kW PV installation is measured under different conditions and used to build simulation model. The installation includes a string of sixteen PV panel, a full bridge inverter and a LCL filter. This model allows studying the influence of the harmonics injected by the inverter on the leakage current.