Performance evaluation of single-phase transfomer-less PV inverter topologies

Abstract

Double line frequency power decoupling with reduced capacitance and mitigation of leakage current are two of the major challenges of any grid-connected single phase photovoltaic (PV) inverter. This paper compares the performances of different topologies for single phase transformerless PV application in terms of the power decoupling capacitor requirement, the current ripple and total harmonic distortion (THD), efficiency performance, and leakage current. The topologies considered include a doubly grounded T-type dynamic dc-link (DDCL) inverter, a half-bridge voltage swing (HBVS) inverter, and conventional full-bridge (FB) inverter with three different modulation schemes (bipolar, hybrid, and unipolar). The leakage current arising from both parasitic capacitances of the PV module and the heat sink is considered in the present study which is essential for design of the electromagnetic interference (EMI) filters. The analysis are supported by experimental results from SiC-based 1 kW hardware prototypes operating at 120 V ac nominal output at a switching frequency of 100 kHz for each of the topology.