Vulnerability Assessment Of Transmission System Cascading Failures Based On Risk Theory

With the rapid development and progress of national economy and power industry technology,the influences of social and economic caused by power system faults are growing.It has become one of the most concern all over the world,which is ensure the safe and normal operation of power system.Traditional security evaluation methods of power system develop further in order to adapt to the complexity and randomicity of power system,and vulnerability assessment method arises at the historic moment in order to reflect the system security state more effectively.Due to the particularity of the grid structure,certain key components failed,which may be further developed into cascading failures,even cause blackout accidents.To avoid blackouts accident,and to reduce the loss caused by cascading failure,a kind of vulnerability assessment method of transmission system cascading failures based on complex network theory and risk theory was put forward.This method can identify and analyze the vulnerable components of power system and evaluate the risk of power system cascading blackouts failures,even for further study on the method of risk mitigation and evade.It has an important practical significance to providetheoretical basis for grid operation and planning personnel.Fragile sources of power system ferreting method based on complex network theory was proposed.Based on complex network theory,the network structure importance,line function importantance,and comprehensive line importance factors were defined,by comprehensively considering three factors:line betweenness,actual trend and probability of lines shut down,to describe the vulnerable degree of line and fragility source of the transmission system,which laid a foundation for identification of system vulnerability fastly.The transmission system cascading failures search model based on fragile sources of system ferreting method was proposed.Fragile sources of transmission system as initial fault sources of cascading failures,it designed the search process of transmission system cascading failures based on transmission system components and network model;a kind of cascading failures combination events probability algorithm based on binary tree was put forward to determine transmission system combination events probability,and to raise the search efficiency of cascading failures of system.Quantitative evaluation index of cascading failure consequences is put forward,quantitative assess by the loss caused by cascading failure,rationality of network structure and weak links of the system,to provide the system quantitative risk indexs of cascading failures vulnerability for power grid planning and scheduling operation personnel,to provide references for planning and scheduling of power grid.And the effectiveness of the algorithmis validated by the IEEE-RTS 79 test system.The results show that the vulnerability assessment method of cascading failures based on the risk theory could find weak links of system and the hidden troubles of cascading failures more effectively,which can highly improve the identification accuracy,efficiency and verified the effectiveness of the vulnerability assessment method mentioned above in this paper.