Topology Review of Transformer-Less Single-Phase Common-Ground Converters: Inverters

Transformer-less inverters are increasingly employed in distributed photovoltaic (PV) power generation systems due to the absence of transformers, leading to higher power density, efficiency, and reduced costs. However, the common-mode (CM) voltage and the parasitic capacitance between the PV panel and the ground generate CM leakage current, which can cause issues such as safety hazards, electromagnetic interference (EMI), and additional losses. The transformer-less single-phase common-ground (TLSPCG) inverter topology, where the dc-side terminal is connected to the ac-side terminal, is regarded as an effective method to mitigate leakage current. This article first classifies the recent TLSPCG inverter topologies, describes the working principle of topologies, extracts the deductive relationship between similar topologies, and summarizes the topology derivation methods. Then, the TLSPCG inverter topologies are systematically compared and analyzed in terms of structure, research status, performance, cost, and application. This article also presents a TLSPCG inverter topology selection and a process for components, along with a discussion on hardware structure design. Finally, key technologies of TLSPCG inverters are summarized, and a case is used to examine the impact of high-frequency (HF) switching technology on the performance and cost of TLSPCG inverters.