A Seamless and Autonomous Mode Transfer Method of Grid-Connected Inverter with Critical Load

A grid-connected inverter with critical loads should be able to supply a stable voltage to critical loads at the instant of a mode change as well as during clearing time while detecting unintentional islanding. This paper proposes a mode transfer method for a grid connected inverter with the critical loads. The proposed method, which integrates grid-connected mode control loop and islanded mode control loop into one control block, provides autonomous and seamless mode transfer from the current control to voltage control. Therefore, the proposed schemes can supply a stable voltage to critical loads at the mode change instant as well as during the clearing time. To validate the proposed method, experimental results are provided.