Minimization of leakage ground current in transformerless single-phase full-bridge photovoltaic inverters

Abstract

The market of PV systems is rapidly expanding during the last years and the transformerless DC/AC inverters are key components in this evolution. Despite its design and control simplicity, a transformerless full-bridge DC/AC inverter may exhibit a high leakage ground current, due to capacitive coupling between the solar panels and ground, which prohibits its employment in single-phase PV systems. Thus, multiple alternative transformerless PV inverter topologies have been developed in the past, which, however, comprise additional power devices and/or passive components. In this paper, a new modulation method is proposed for optimally controlling the power switches of transformerless single-phase full-bridge PV inverters, such that their leakage ground current is minimized. The design results demonstrate that by using the proposed technique, the leakage ground current of transformerless full-bridge inverters is reduced below the maximum limit imposed by the VDE 0126-1-1 standard, thus enabling their application in single-phase PV installations, instead of more complex PV inverter structures.