Technical aspects of common-mode leakage current suppression in pv-generation systems

Currently in many countries much attention is paid to the power generation systems using renewable energy sources. However there is much less research is being carried out on transformerless structures and multilevel converter topologies. This paper intends to reveal some essential features of a grid-tied PV-generation system based on multilevel converter and without transformer. In particular, common-mode leakage current, a well-known problem of such systems, has some peculiarities if a multilevel converter is used. It is shown, that the common-mode voltage is the main reason of the leakage currents in single-phase and three-phase systems. The paper explores possible solutions to reduce or entirely suppress these currents and compares different known solutions. A solution for multilevel system is proposed and verified by simulation.