Analysis Of Power System Cascading Failure Based On Percolation Theory And Risk Theory

The structure of power grid is becoming more and more complex and the area interconnectivity of power grid is gradually enhanced, which makes big blackout accident happen many times and brings great loss and influence to the national economy and the people’s life.Studying the fault occurrence and development process of cascading failure and predicting fault path has very important significance to prevention cascading failure. In this article, based on percolation theory and risk theory, the branch fault outage probability model and cascading outage path risk assessment model was establishment, which could effectively identify fragile branch and system vulnerable path, it has the important theory significance.This paper first briefly introduces the mathematical description and the connected model of the percolation theory, combined with the percolation theory and the power network, and expounds the rationality of the development process of the power system cascading failure using the percolation theory.This paper constructs a branch outage distribution factor, initial load rate and overload factor, then get the power transfer related factor between branches. Considering the protection hidden failure, get the branch hidden failure related factors, then two factors are comprehensive branch fault percolation probability, seepage degree of fault characterization to the other branch. Secondly, considering the branch real-time load rate and the rate of change of voltage on both ends of the branch node after the fault line disconnection, respectively established the branch load influence factor and voltage deviation factor, comprehensive real-time line health indicators. Thirdly, considering the impact of the electrical topology and the average load rate of the system after branch outage alone respectively established the electrical topology importance degree factor and the average load rate influence factor, comprehensive index of branch importance, characterization of branch vulnerability affects the system fully. Combining the above three indicators to construct the fault branch outage probability model to predict possible cascading failure development path.IEEE39 node system simulation results show that the built model can effectively identify fragile branch of normal operation system and predict even lock failure process at all levels of the fault branch.In order to carry out the comprehensive diagnosis and evaluation of the system, this paper studies the consequences of cascading failure path, constructs three sub consequences indexes which reflect the system vulnerability, including the maximum operating connectivity rate, cumulative load loss, voltage change accumulation severity. Then using entropy method calculate the objective weights of each index, got the comprehensive consequences index. Cascading fault path risk evaluation model was built based on probability and consequences of the path. The simulation results in the IEEE39 system show that this model can not only identify the failure probability of the path, but also to identify the probability is small, but the system fault hazard path, this algorithm has certain reference for cascading failure monitoring.