Grid-connected isolated PV microinverters: a review

Galvanic isolation in grid-connected photovoltaic (PV) microinverters is a very important feature concerning power quality and safety issues. However, high-frequency transformers and high switching losses degrade the efficiency of the isolated types of microinverters. Recently, several isolated topologies were proposed to increase the efficiency and lifetime of PV converters. This paper presents a comprehensive review of the most recent isolated topologies of PV microinverters. These topologies are categorized into two groups in terms of their power processing stages: 1) single-stage microinverter and 2) multi-stage microinverter. Various topologies are presented, compared, and scrutinized in terms of the power losses at different stages, control techniques, position of the decoupling capacitor, and cost analysis. Recommendations are provided to improve the existing topologies and select the suitable control techniques to obtain a clear picture of the framework for next-generation isolated PV microinverters.