Cascading Failure Critical Components Identification Model Based On Heterogeneity Of Complex Power Grid

The development of new energy resources and further interconnection of power grid have resulted in a more complicated grid structure and a more flexible operation mode. Thus local disturbances can spread at a higher speed in a larger scale, threatening the stability and security of the power grid. In recent years, several cascading failures have taken place worldwide. Most of these failures were triggered by critical components single fault, and then developed through multi-faults in chains, eventually led to mass load loss or even blackout of power. Taking all these into consideration, it is very necessary to identify those critical components in cascading failure for more targeted supervise and control. With the deepening of the research on power grid cascading failure, more attention has been paid to heterogeneity, the heterogeneity of power grid structure and power flow distribution make the power grid present different response to cascading failures. Against the above background, researches on cascading failure critical components identification model based on heterogeneity of complex power grid are presented in this paper. The major works are summarized as follows:Explore the heterogeneity characteristics exhibited in network structure and operation of complex power grid, and the concept of heterogeneity characteristics of complex power grid is proposed. Based on the concept of Gini coefficient in economics and entropy theory in thermodynamic, heterogeneity index for network structure and power flow distribution were proposed.The impact of complex power grid heterogeneity characteristics on cascading failures was in-depth studied. Aiming at the shortages of existing cascading failure simulation model, considering new energy and load fluctuations, relay protection devices hidden failures, a new self-organized criticality simulation model based on cascading failure process is established. The impact of complex power grid heterogeneity characteristics on self-organized criticality and cascading failures were simulated in detail, and the impact mechanism were revealed.Based on the heterogeneity of flow betweenness, a cascading failure critical line identification model is established. A new concept of flow betweenness of power transmission line is proposed as a criterion for cascading failure critical line identification in a power system. This new concept can adapt to the variation of power flow distribution under different operation modes. It can also quantify the contribution and effects of transmission line on the whole grid power transfer with a more comprehensible physical background. Based on the heterogeneity of flow betweenness, a cascading failure critical line identification model is established for identifying the critical lines in the self-organized critical state of power system.Based on the heterogeneity of power grid structure, a cascading failure critical node identification model is established. A new concept of electrical node degree of power grid node is proposed to characterize the status of nodes in a power grid, so that the "degree" of nodes is more in line with comprehensible physical background. A cascading failure critical node identification model is established based on the heterogeneity of electrical node degree, which convert the nodes optimization problem into a problem about multi-objective optimization on the overall performance of a power grid, and then the niche PSO algorithm is proposed to solve it.A comprehensive risk assessment of cascading failures critical components method based on fuzzy comprehensive evaluation model is proposed. By taking full account of the uncertainty effects in the process of cascading failures propagation sequence and the influence association, the occurrence probability of cascading failures caused by critical components is calculated. A fuzzy comprehensive evaluation model for cascading failures is established which uses severity indexes to assess the severity of critical components from structural characteristics and operation characteristics of power system. At last, it assesses and grades the risk of cascading failures critical components combine with the occurrence probability and severity, which will provide the basis for cascading failure early warning and supervisory control.