Performance analysis of different transformer-less inverter topologies for grid-connected PV systems

Abstract

Transformerless Photovoltaic (PV) inverters are gaining popularity compared to their transformer-based counterparts. They are more efficient, cost-effective, and smaller in volume. Despite this, parasitic capacitance causes the common mode current to flow between the PV array and the grid. In addition to losses, leakage current increases electromagnetic interference (EMI) and poses issues to the protection system. Transformerless inverters should therefore be so designed that the leakage current is minimized. Common mode voltage changes (VCM) causes the leakage current. There are a number of PV inverter topologies that have been designed to minimize these variations. This paper discusses H4, H5 and HERIC single-phase PV inverter topologies. Circuit simulations have been used for analysis. HERIC Topology is best one of these since it reduces the leakage current with lowest power loss due to ac bypass instead of usual dc side decoupling. It is a type of resonant converter that operates at high frequencies to achieve efficient power conversion. In this work comparison has been made between topologies for their effectiveness in reducing leakage current. Moreover, its variation with load has been studied, a perspective missed in other studies.