Mitigation of Leakage-Ground Currents in Transformerless Grid-Tied Inverters via Virtual-Ground Connection

Abstract

This article studies the benefits of the virtual-ground (VG) connection for single-phase transformerless grid-tied inverters, which is used to mitigate the leakage-ground currents (LGCs) issue. This article also proposes common-mode and differential-mode models of single-phase inverters connected to the grid through an $LCL$ output filter, which are used as a theoretical support. It is shown that LGCs are simply common-mode currents (CMCs) circulating through the ground path, which represents a contribution in the development of an approach to find solutions in general scenarios. In most of the cases, these currents are produced by the existence of common-mode voltages (CMVs), which find a way through the ground path established after the stray capacitances in the terminals of, for instance, photovoltaic (PV) panels. To prove the advantages of the proposed interconnection and for analysis, the single-phase full-bridge version of a two-level conventional inverter, as well as a neutral-point-clamped (NPC) inverter, is considered for model derivation and experimental validation.