Novel H6 Transformerless Inverter for Grid Connected Photovoltaic System to Reduce the Conduction Loss and Enhance Efficiency

Presence of a transformer in a grid connected photovoltaic system provides galvanic isolation between the photovoltaic panels and the grid. However, it increases the overall cost, makes the circuit bulky and reduces the efficiency of the system. Hence, transformerless inverters have gained significant importance owing to its low cost, light weight and increased efficiency. However, due to the absence of the transformer, there is no galvanic isolation between photovoltaic panels and the grid and there is always a threat of flow of leakage current. In this research paper, an elaborate analysis of H4, H5 and H6 transformerless inverter is carried out. DC side decoupled circuits are studied to eliminate the leakage current. Their performances are compared based on the simulations carried out in MATLAB/SIMULINK software. A novel H6 inverter is proposed by introducing an additional switch in H5 topology. A direct current path is provided in H5 topology during one of the active modes, so that current flows through few switches thereby reducing the conduction losses. Common mode voltage remains constant in the proposed H6 inverter and hence the leakage current is eliminated. The proposed H6 inverter can thus be a promising topology to eliminate leakage current and reduce conduction loss in the transformerless grid connected photovoltaic system.