Research On The Cascading Failures Blackouts In Power System Based On Complex Network Theory

In recent years, many people are concerning about frequent power blackouts. The efficiency of power system has been proven since large-scale interconnection within power grids has strengthened links various of grids. However, it has increased the uncertainty of the system's operation, made the disturbance of the power system spread to a wider area, and the local failures may spread rapidly to large regionals even the entire network. Blackouts are usually caused by a cascading failure, the study on the mechanism of the generation and dissemination of cascading failure, on which many domestic and foreign scholars and experts are focusing on, is of great significance. The traditional failure analysis methods have shown some limitations with the increasing grid size. Therefore, the complex network theory is applied to study cascading failures of large-scale interconnected power network, to explain the generation mechanism of blackouts, to establish failures models and propose measures to mitigate and prevent the blackouts in power system, has become a hot topic in the field and is of great scientific theory and practical significance.Cascading failures are analyzed based on the theory of complex networks in this thesis. The features of cascading failures are analyzed through modeling as well as the structure heterogeneity of complex power network. Specific work of this thesis is discussed as follows:Firstly, study discusses the background, significance and research status of the cascading failure of complex power system. Moreover, the basic concepts of complex network theory are introduced including basic structural parameters, characteristic path length, degree distribution, clustering coefficient and betweenness. Several basic topology models such as random network, regular network, small world network and scale-free networks as well as their features are outlined and described.Secondly, based on the existing DC power flow power system cascading failures, a cascading failure model base on AC power flow and considering the evolution of power network has been proposed. In the slow dynamic process, the network evolve in the time and space evolution model, the topology structure of the network after the evolution got by simulation, and the features of topology structure are analyzed as well. Moreover, the self-organized criticality of the blackout and the impact of different parameters on the blackout are analyzed. Thirdly, the concept of heterogeneity of power network structure is proposed. Moreover, heterogeneity of the power networks structure is analyzed based on the Lorenz curve and Gini coefficient. Comparing the heterogeneous of actual power network structure through the Lorenz curves and Gini coefficients, and also the average load loss under different Gini coefficient are compared to analyze the impact of heterogeneity of network structure on the cascading failure blackouts.In conclusion, the blackout model base on AC power flow and considering the evolution of power network has been proved though discussion is eligible for network cascading failures. Moreover, a new pathway is proposed to solve the network structure heterogeneity with the introduction of Lorenz curve and Gini coefficient.