Service Restoration for a Renewable-Powered Microgrid in Unscheduled Island Mode

This paper deals with the service restoration problem in renewable-powered microgrids that are driven islanded by an unscheduled breakdown from the main grid. The objective is to determine the maximum of the expected restorative loads by choosing the best arrangement of the power network configurations immediately from the beginning of the breakdown all the way to the end of the island mode. The intermittency nature of the renewable power, as well as the uncertainty of the duration of the breakdown pose new challenges to this classic optimization scheduling task. The proposed two scenario-splitting methods can be solved in a two-step solving procedure, in which a Lagrangian technique and dynamic programming are utilized to provide an analytical sub-optimal yet efficient solution to the original problem. Simulation results demonstrate that both methods can find solutions very close to optima effectively; the scheduling plan should be adjusted when the time evolves, especially when the renewable power generation takes a large portion in the power supply; and the energy storage system plays a significant role to reduce the risk of unreliability in the wind power forecasting, even with a small amount of capacity. Finally, the proposed approach can be applied to radially configured systems with other types of distributed generators.