Tentative Study On Power System Cascading Contingency Prediction

In recent years, some big blackouts occurred in many countries around the world have brought tremendous damages. Such catastrophic events were usually caused by cascading tripping of some power system devices (cascading contingency). So, studies on the mechanism of cascading contingency and preventive approaches to avoid blackouts in power systems had become an important hot topic. In this thesis, we mainly focused on the mechanism of cascading contingency in power systems. Our target was to find effective method to predict the sequential contingencies in the power system collapse.We deeply explored some existed methods for cascading contingency analysis. Based on that, we presented one method to predict the sequential contingency set in the evaluation of power system collapse, which was based on the power flow analysis. This method could effectively consider the impacts of happened outages to the consequential contingencies so that it was better than the traditional N-1/N-m predicting methods. Based on static analysis, the calculation speed of this method was very fast. In the evaluation of power system blackouts, there usually existed a sequential contingency stage before cascading tripping beginning. At this stage, there was a large time delay (minutes or even hours) between two sequential contingencies so that the transient of the pre-contingency had annihilated and system had come back to the steady state. So we were able to apply static analysis method to the prediction of the sequential contingencies in this thesis. Some testing power systems, such as a ten-bus system and IEEE 118-bus system, were employed to validate the presented method. Results of the case study showed that the method was correct and usable.In this thesis, we also did some researches on the online contingency screening and ranking according to the requirement of the project"synthetic security region and its visualization of Henan power system". Some ranking algorithms were programmed, which could also be used to identify the first contingency in the sequential contingencies.Evaluation of power system consequential contingencies is a complex and nonlinear dynamic process. So, works of this thesis (based on static analysis method) is just a tentative study to this topic. In order to understand the mechanism of power system consequential contingencies and blackouts, more studies shall be done in the future.This thesis is partly provided by the Key Project of Chinese Ministry of Education (under grant 105047).