Research On Fast Screening Of Double Contingencies In Power System And Control Strategy

With the increasingly economic development and social progress, the interconnected degree of grid will continue to increase, and the scale will expand unceasingly, which also increases the requirement to power supply reliability. Interconnection of grid increases the power supply reliability, which also expands the influence of the fault and increases the operation risk of power system. In recent years, the power system suffered from more and more unsafe accidents, whose consequence is increasing serous, mounting pressure to the safe operating of the power system. The static security analysis of power system has become one of the most important part of the stability analysis of the power system, which needs to search the weak operation point of the power system and screen high-risk contingency scenarios under the safe condition, and then make prevention control strategy according to the contingencies. When the grid is in dangerous operation state after the contingency, to prevent the further expanding of the influence region and cascading failure, etc., serious consequence, emergency control strategy should be made to retain the grid to the safe operation scope.This paper studies the fast screening algorithm of double contingencies in power system and control strategy based on the perspective of power system steady operation.The N-1 test has been done to ensure the single fault will not affect the safe operation of the grid when the grid is planned and put into operation. Hence, this paper puts forward a new fast screening method of double pre-contingencies, and combine the fault probability to form the list of high-risk failure scenarios. First, the failure-affecting domain(FID) is computed based on the network topology and the Power Transfer Distribution Factor. Then, the initial failure set is formed based on the overlapping of FID, and the fault severity index is calculated. Finally, according to the fault probability and the severity index, the risk index is calculated, based on which the fault is ranked, which provide important reference for the subsequent analysis.The optimization algorithm of the preventive control is introduced, and the multi-contingency joint optimization model based on the risk is built on the basic of the improvement of the existing preventive control model. The model proposed in this paper classifies the preventive contingencies and take the most representative contingency as the critical preventive contingency. Then it is only needed to consider the critical preventive contingencies to get the comprehensive preventive control strategy considering all the preventive contingencies, which solves the harmonious and unified of the preventive co ntrol strategy of each preventive contingency and greatly reduces the calculation scale.Emergency control strategy is taken when the grid is in dangerous operation state, aiming to retain the grid to safe operation state with the fastest speed.A load-shedding model based on the power flow tracing is discussed in this paper for the emergency correction control of the grid. This model is improved on the basic of the existing model, and the determination method of the generator/load busses to be adjusted the determination of adjustment amount is improved to retain the system to the safe operation state with faster adjustment speed and fewer adjustment measures based on the premise of a possible narrow influence scope.