Topology Review and Derivation Methodology of Single-Phase Transformerless Photovoltaic Inverters for Leakage Current Suppression

Single-phase voltage source transformerless inverters have been developed for many years and have been successful commercial applications in the distributed photovoltaic (PV) grid-connected systems. Moreover, many advanced industrial topologies and recent innovations have been published in the last few years. The objective of this paper is to classify and review these recent contributions to establish the present state of the art and trends of the transformerless inverters. This can provide a comprehensive and insightful overview of this technology. First, the generation mechanism of leakage current is investigated to divide the transformerless inverters into asymmetrical inductor-based and symmetrical inductor-based groups. Then, the concepts of dc-based and ac-based decoupling networks are proposed to not only cover the published symmetrical inductor-based topologies but also offer an innovative strategy to derive advanced inverters. Furthermore, the transformation principle between the dc-based and ac-based topologies is explored to make a clear picture on the general law and framework for the recent advances and future trend in this area. Finally, a family of clamped highly efficient and reliable inverter concept transformerless inverters is derived and tested to offer some excellent candidates for next-generation high-efficiency and cost-effective PV grid-tie inverters.