Two-stage optimization method for network reconfiguration and load recovery during power system restoration

Network reconfiguration and load recovery (NRLR) during power system restoration is a complex mixed-integer nonlinear programming (MINP) problem, which is difficult to be solved efficiently. To address this problem, this paper proposes a two-stage optimization method for NRLR. The first stage, based on the DC power flow considering frequency characteristics, focuses on the integer variables and provides the optimal plan for transmission line charging and load pick-ups. Then in the second stage, an expanded AC optimal power flow with frequency constraints and load ZIP model is established to minimize the restoration duration of the plan generated by the first stage. The comprehensive restoration plan can be obtained through the iterative optimization process. Case study is undertaken on a 10-machine 39-bus system. Simulation results reveal that the restoration plans obtained from the proposed method are highly efficient, while the computation time satisfies the requirement of online application.