Microgrid planning considering the supply adequacy of critical loads under the uncertain formation of sub-microgrids

A microgrid can be partitioned into several autonomous sub-microgrids in case of multiple faults in natural disasters. How to guarantee the supply adequacy of critical loads in sub-microgrids is a problem that should be considered at the planning stage. This paper proposes a microgrid planning model considering the supply adequacy of critical loads under the uncertain formation of sub-microgrids. The proposed model minimizes the total cost during the project life, which includes the construction cost and operation cost for the candidate distributed energy resources (DERs). The supply adequacy of critical loads in sub-microgrids is taken into account in the model. As we only know the critical load areas, the locations of switches which divide the microgrid into sub-microgrids are unknown at the planning stage. Considering this uncertainty, the microgrid planning issue is finally formulated as a robust model against the worst formation of sub-microgrids. The developed model is tested on two systems: IEEE 33-bus and 123-bus distribution systems. Simulation indicates (1) the proposed method is more robust than deterministic strategy as critical load loss is intolerable in sub-microgrids; (2) the investment cost is the same with that of the deterministic case when the number of sub-microgrids is within two.