Enhancement of Distribution System Restoration Capability in Single/Multiple Faults by Using Microgrids as a Resiliency Resource

Natural disasters such as hurricanes and major floods result in extensive interruptions and lack of service to end-use customers in electrical distribution systems. Robust systems immune to extreme abnormal events are uneconomical and hard to achieve, so, fast and reliable solutions to restore the service after major outages are preferable. Rerouting the supply to critical loads and deploying microgrids are common solutions. In this paper, a sophisticated solution based on a combination of reconfiguration and application of microgrids is proposed to enhance the restoration capability of the distribution system using spanning tree search strategy. The coordinated plan would maximally restore the critical loads by using microgrids as emergency sources even when utility power is unavailable. The objectives are minimizing the number of switching operations, total system losses and out-of-service loads. A heuristic approach is proposed to simplify the graph of the distribution network in order to reduce the computational complexity. Instead of removing all degree one/two vertices, a threshold for simplification is applied to avoid establishment of zones with high loads that could not be restored by microgrids. The proposed method is simulated on a four-feeder, 1069-bus unbalanced test system with four microgrids to demonstrate its effectiveness.