Transformerless Active Isolation in Common-Ground Photovoltaic Microinverter Applications for Reduced Ground Leakage Currents

This paper presents two novel power converters that realize galvanic isolation by utilizing active transistor devices instead of conventional transformers. The power converters employ standard boost-buck and buck-boost topologies but isolate the ground connections on the source and load terminals using active semiconductor devices on the ground loop. These actively isolated converters are good candidates for common-ground photovoltaic (PV) applications where reduced common-mode (leakage) currents are required. A 350W boost-buck and 1kW buck-boost unipolar active isolated converter are built and experimental results show that active isolation can provide improved efficiency, higher power density, and lower cost compared to transformer-based solutions while maintaining the required low ground leakage currents specified in standards for these applications.