Topologies and modulation methods in leakage current suppression for PV grid-tied inverters

Abstract

Photovoltaic (PV) inverters are widely discussed as solar energy became commonly used as a renewable energy source. Transformerless grid-tied inverters are often chose for their low cost and low energy loss. Since the existence of stray capacitance between PV cells and conducting surface causes a changing common-mode voltage (CMV) which would arise leakage current and thus pollute the output current quality to the grid and endanger human safety, novel topologies and modulation strategies are proposed to save the problem for transformerless inverters. In this paper, different methods to suppress the leakage current will be analysed. The theoretical analysis of CMV and leakage current generation by single-phase inverter is presented. Based on the basic principle of leakage current suppression topologies proposed to eliminate the leakage current are introduced. The effects of some well-known modulation methods on CMV controlling have been compared, and novel methods dealing with three-phase harmonic management are presented.