Active synchronization control for microgrid reconnection after islanding

Microgrid (MG) islanding is considered as an effective measure to minimize power outage and therefore to maximize usage of renewable energy resources. One of the most challenging technical difficulties associated with islanding is out-of-phase reclosing caused by asynchronism of MG with the electric power system (EPS). In this paper, a novel control methodology is proposed to synchronize MG with the main power grid so that smooth transition from islanded mode to grid-tied mode can be guaranteed. Synchronization is achieved by eliminating the voltage phase angle difference across the circuit breaker/recloser at the point of common coupling (PCC). The proposed control employs synchrophasor measurements transmitted via Internet Protocol (IP) communications. A MG hardware testbed with multiple distributed generators and loads is built to validate the performance of the proposed method.