A Synchronizing Strategy for Seamless Interconnection of an Isolated Microgrid

Distributed Energy Resources (DERs) are gradually becoming dominant sources of generation in modern power systems. From a system resilience perspective, the distributed nature of such resources helps in forming islanded microgrids during grid contingencies. Therefore, a robust synchronization mechanism is needed to synchronize the autonomous islanded microgrid to the utility grid. As grid forming inverters (GFM) help in establishing the voltage and frequency of an islanded system, it is necessary that a strategy is developed to follow the utility grid’s voltage magnitude and phase during reconnection after contingency events. In this paper, a synchronization strategy is developed which translates the operation of a GFM from a master mode to a slave mode without requiring any change in power production philosophy. The proposed method does not require alteration of existing control strategy, thus preserving the true characteristics of a GFM system. The technique is validated in the modified IEEE 9-bus system and the EMTDC/PSCAD simulation results demonstrate the seamless transition effect of the proposed strategy.