A Branch Power Flow Based Voltage Stability Index And Its Application

With several widespread system blackouts resulting from voltage collapse throughout the world in recent years, researchers has pay more and more attention to the problem of voltage stability. A lot of research had been done by Domestic and foreign scholars, but many problems of voltage stability are still no consensus was reached. Thus it is imperative to study the problem.Based on the summarization of previous work, this dissertation conducts a further study on voltage stability. The dissertation points out the focus of the study of voltage stability, analyzes some voltage stability indices that have been used or been proposed by recently, and points out the benefits and disadvantages of these indices. After that, the dissertation proposed a new voltage stability index LSI(Line Stability Index) based on branch power flow. It is proposed by using the discriminant of the quadratic of voltage. The index can be calculated easily and fleetly. It avoids to calculate the big matrixes and complicated iterative. The value of LSI is between 0 and 1. The distance between LSI and 1 denotes the margin of voltage stability. It not only can indicate the unstable bus but also can indicate the weakest line of the system. That is the advantage compares to other bus indices.Some research work on contingency screening and ranking is carried out. The voltage stability index presented in this thesis is utilized as the influence indicator of contingency to system voltage stability. We take the voltage indices as the samples under after-contingency situation. An improved fuzzy k-means algorithm is used to make clustering analysis of the samples, and contingency screening and ranking are obtained according to the hazard rating to the system.The dissertation analyzes preventive control of voltage stability, especially research load shedding control. Because voltage stability index LSI can indicate the information of branches and buses, it is benefit to judge the stability of the power system and select the buses that would be shed. Because of that, the dissertation proposed a load shedding control scheme based on LSI.IEEE stander test systems are used to test the theory that proposed in the dissertation. The results show the availability of them.