A novel fuzzy based transformer less PV inverter for reactive power control in grid connected PV system

Abstract

With worldwide increasing demand for electric energy, there has been a great interest in exploring photovoltaic (PV) sources. In recent years, there have been quite a few new transformerless PV inverters topologies, which eliminate the traditional line frequency transformers to achieve lower cost and higher efficiency, and maintain reduced leakage current as well. However, one of the technical difficulties of the transformerless inverter is the safety issue of leakage current. The leakage current through the stray capacitors between the PV array and the ground is harmful because of unstable common mode voltage and absence of galvanic isolation. This leakage current that flows between the parasitic capacitance of PV array and the grid has to be eliminated, may otherwise leads to major safety problems. In addition, according to the international regulations, transformerless inverter should be capable of handling a certain amount of reactive power. Here, a newly proposed transformerless inverter for grid tied PV system can eliminate the threat of leakage current. The proposed topology also has the ability to inject reactive power into the utility grid. Fuzzy logic controller and PR controller is used to ensure high quality injected current to the grid. Detailed analysis of proposed transformerless inverter with operation modes of common mode, leakage current analysis and reactive power control capability in MATLAB simulation model are presented.