This paper describes a novel strategy for microgrid operation and control, which enables a seamless transition from grid connected mode to islanded mode, and restoration of utility supply, without loss or disruption to loads sensitive to frequency or phase angle dynamics. A simulation study is conducted on a microgrid featuring inverter connected renewable generation, and power electronic interfaced loads. Therefore, the microgrid inherently has low inertia, which would subsequently affect the dynamic characteristics of the microgrid, in particular during mode transition. The microgrid is controlled by means of synchrophasor data to achieve synchronous island operation, enabling the microgrid to track the utility frequency and phase angle. The simulation includes synchrophasor acquisition and telecoms delays, allowing for detailed investigation of the microgrid dynamics under various mode transition scenarios, including the risk of commutation failure of the inverter sources. The proposed method is demonstrated to successfully maintain a microgrid in synchronism with the main utility grid after the transition to islanded mode without significant impact on various equipment connected to the microgrid. Thus, synchronous island operation of low inertia microgrids is feasible. This study also showed that utility supply could be seamlessly restored if the microgrid is operated as a synchronous island.

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