A Probabilistic Assessment Method Considering Instability Caused By Cascading Failures For Power System Transient Stability

With the increasing scale of power system, the enhancing relationship of regional grids and the deepening of the electricity market, the power system is running closer to its limits. For the heavily loaded grids, the instability probability caused by cascading failures can’t be ignored. Therefore the traditional probabilistic assessment method based on the N-1criterion can’t comprehensively reflect the security situation of the power system which is running close to its limits.Firstly, an improved probabilistic insecurity measurement based on dynamic security region is proposed in this paper, which contains a discrete probability distribution of the fault location and a failure probability model under different weather conditions, and then the probabilistic assessment methodological framework is established which concludes reclosing probabilistic model and cascading failures.Secondly, an improved model of cascading failures is proposed. It combines the advantages of the OPA model and the pattern search method. Not only DC optimal power flow theory, but also the overload protection probability tripping model is taken into account in the process of the cascading failures path search, this can better simulate the impact of the various uncertain factors on cascading failures.Finally, a probabilistic assessment method considering instability caused by cascading failures for power system transient stability and an algorithm of the corresponding probabilistic insecurity measurement is put forward in this paper. The impact of the load growth and expansion of transmission capacity on cascading failures probability and probabilistic insecurity measurement is validated by the simulation results on IEEE10-machine39-node svstem.