A Novel Single Phase Grid Connected Transformer-Less Solar Micro-Inverter Topology With Power Decoupling Capability

Abstract

A novel transformer-less micro-inverter topology suitable for interfacing a 35 V, 220 W solar PV module to a single phase 220–230 V ac grid is proposed in this paper. It employs only six switches, out of which two switches operate at high frequency, three at line frequency and one switch at high frequency during the negative half cycle of the grid voltage. The micro-inverter is operated in discontinuous conduction mode of operation for all possible operating conditions to achieve high gain as well as negligible turn on losses for the high frequency switches. In this topology the negative terminal of the PV module is shorted with the grid neutral which makes the magnitude of the leakage current flow to be zero. The power decoupling between the dc and ac sides is inherent in this topology, and it is achieved without incorporating any active power decoupling circuit. Thin film capacitors are utilized to improve the reliability of the micro-inverter. The detailed analyses of the proposed micro-inverter are carried out. The effectiveness of the proposed scheme is verified by performing detailed simulation studies. A 220 W laboratory prototype of the proposed micro-inverter is fabricated, and detailed experimental studies are carried out to confirm the viability of the proposed scheme.