Leakage current analysis of single-phase transformer-less grid-connected PV inverters

Abstract

Transformer-less string PV inverter is getting more and more widely utilized due to its higher efficiency, smaller volume and weight. However, without the galvanic isolation, the leakage current limitation and operation safety became the key issues of transformer-less inverters. This paper simplifies the leakage current generation circuit model and presents a leakage current estimation method both in real time and frequency domain. It shows that the leakage current is related to the circuit stray parameters, output filter and common mode voltage. Furthermore, with the proposed analysis method, the leakage current generation of H-bridge with different modulation methods and HERIC inverter are discussed individually. At last, the presented method has been verified via simulation.