Control strategy for seamless transition from islanded to interconnected operation mode of microgrids

Microgrids can operate either interconnected to the utility grid or disconnected forming an island. The transition between these modes can cause transient overcurrents or power oscillations jeopardizing the equipment safety or the system stability. This paper proposes a local multi agent control method for a seamless transfer between the islanded and interconnected modes of operation with agents implemented into the microgrid central switch (MCS) and into the microsources inverters. The MCS agent supervises the grid status and controls the switch for the transition of the microgrid through the different operation modes, while it communicates locally with the inverter agents of the microsources. The inverter agents undertake the synchronization process in case of reconnecting and change the inverter control mode depending on the grid status. Simulation and experimental results are presented to show the performance and feasibility of the proposed strategy.