Indian Journal of Science and Technology

Abstract

Objectives: To make a comparative analysis of four transformerless topologies namely H5, H6, oH5 and H-Bridge Zero Voltage State Rectifier (HBZVR) in terms of leakage current and THD. Methods/Statistical Analysis: H5, H6, oH5 and HBZVR topologies have been simulated. Then these topologies are compared in terms of leakage current and THD. Based on the comparative analysis, the topology with less leakage current and THD has been chosen for photovoltaic interface. The interfacing circuit is simulated and realized as prototype to validate the results practically. Findings: It is found from the review that HBZVR topology has less leakage current and THD. This topology employs both galvanic isolation and Common Mode Voltage (CMV) clamping. It is found that the common mode voltage in HBZVR is almost eliminated. The conclusion derived from this paper may be helpful in selecting proper topology for PV interface. Application/ Improvements: Generally, in grid connected PV inverters, transformers provide galvanic isolation between the two electrical circuits, thus preventing the flow of leakage current between the stray capacitance of PV and ground. But, ransformers reduce the overall efficiency of the system, which lead to the development of transformerless PV system. Galvanic connection exists between the PV and grid in transformerless inverter, which leads to the presence of leakage current. So, to reduce leakage current, many topologies are introduced which employs either dc-decoupling or ac-decoupling to provide galvanic isolation. The HBZVR topology provides proper isolation for PV interface where the capacitance of the panel with respect to ground is large. 

Keywords: Comparison, Leakage Current, Isolation, Transformerless PV Inverters, THD