Studies On Optimal Control Of Power System Restoration After Blackout

Several large scale blackouts happened in recent years. Both domestic and abroad researchers tell us that ensuring the security and the stable operation of power systems is becoming more and more difficult. The power system restoration with high efficiency can reduce the recovery time and the loss. The objective of power system restoration is to restore the load as soon as possible. And the successful start-up of generators is the precondition of load restoration and the basis of power system restoration. Based on current researches, a detail study on unit start-up, recovery path and load recovery has been carried out in this thesis.Firstly, the fuzzy AHP(Analytic Hierarchy Process) method was used to determined units start-up sequence after blockout. Factors of unit has been considered as the evaluation index. The proposed method by optimizing the sequence of units could improve the efficiency of the unit start-up.When the starting order of units was determined, the power supply to the target unit from the black-start unit is required. Because of the security issue of power system restoration, the weight of recovery path was restored. In order to avoid violating the constraints of power system restoration, the depth search algorithm was used to control the scale of solution, and Dijkstra algorithm is adopted to find the lowest charging capacitor of recovery path to suppress the self-excitation of generator and system overvoltage.Then, the problem of the load recovery, which is the last stage of the power system restoration, was studied. The load recovery is a complex problem. A general model is proposed for calculating the maximum restorable load amount. Frequency deviation is calculated by the average system frequency model or an estimation formula. With this algorithm, the maximal restorable loads at one of the stages of load restoration can be calculated. The proposed approach to determine the sequence of load restoration can make a balance between the quick recovery of the important loads and minimization of the outage cost.Lastly, case studies demonstrate that the proposed method and strategies of each stages of power system restoration can deal with emergency blackouts effectively. The methods and strategies, which improves the availability and feasibility of restoration schemes. The solving algorithm is effective to reduce the cost of blockout and also can improve the efficiency of power system restoration.