Single phase transformerless inverter topology with reduced leakage current for grid connected photovoltaic system

Abstract

Leakage current is the main concern of the grid connected transformerless photovoltaic (PV) inverters. Many single phase transformerless inverter topologies with reduced leakage current have been introduced in the past few years. These are mainly classified on the basis of leakage current reduction methods Galvanic isolation without- common mode voltage (CMV) clamping and with-CMV clamping. It has been shown that leakage current generation is highly dependent on CMV. CMV of the topologies without- CMV clamping oscillates and oscillation amplitude depends on switches’ junction capacitances and parasitic parameters of the topology. In order to eliminate the leakage current completely, CMV must be constant throughout the inverter operation. Moreover, inverter should also be capable to inject definite amount of reactive power into the grid, as demanded by the international regulations. In this study, reduced leakage current CMV clamped topology is proposed which can eliminate leakage current and capable of injecting reactive power into the grid. Total harmonic distortions (THD) of injected grid current at various solar irradiance levels are also analyzed. In order to verify the theoretical explanations, the proposed topologies are simulated in Matlab/Simulink environment. Finally, the simulated results are validated experimentally.