Research On Key Nodes And Lines Recognition Method For Complex Power Grid

In recent years,frequent large-scale blackouts have caused huge economic losses to the human society and further seriously threaten the stability of the operation of society.Given that,the reliability of the operation of the power grid has become the focus of academy research.Blackouts are mostly caused by single failure,such as line overload,component failures,communication system failures and so on.The aforesaid items are vulnerable to a certain extent.Any failure of such will decrease the stability of the power grid.Additionally,any disturbance to such items will likely cause cascading failures.Therefore,strengthening the protection of important nodes and lines will benefit the improvement of the robustness of power grid operation and reduce the probability of major blackouts.The thesis primarily focuses on the recognition of the importance of grid nodes and line.This thesis also intends to improve the security of operation and ensure the safety of operation regarding the power grid.Firstly,the thesis proposes a multi-dimensional grid importance calculation model based on the risk utility entropy.Such model calculates the importance of the nodes from multiple dimensions,such as grid statistical characteristics,grid vulnerability and importance of power communication network nodes.To avoid the subjectivity of selecting weights,the calculation of the importance of the nodes is proceeded through the method as a combination of both subjective and objective weights in order to improve the accuracy of the identification results.At the same time,the risk entropy weight is also introduced into the abovementioned object weight in order to make the calculation results of nodes importance reflect the impact of nodes failure on the reliability of power grid.The simulation results of IEEE39-bus network show that the importance of nodes calculated in this thesis will decline the serious network disconnection and transmission ratio.This result proves the accuracy of the aforesaid methodology adopted by this thesis.Regarding the issues of single evaluation angle and weak adaptability to the changes of network operation modes,a multi-dimensional identification model of vulnerable lines based on DS evidence theory is proposed in this thesis.This model reflects the multi-dimensional index set indicating the vulnerability of the established line from the perspective of topology connection,active transmission and voltage stability.Based on such,this thesis proposes an index weight calculation method adapting to the network operation state,and uses the improved DS method to combine multiple indicators further obtain the comprehensive evaluation values of lines vulnerability in multi-dimension.The simulation results show that the failure of the important lines calculated in the thesis will lead a rapid decline in the transmission ratio of the network,which proves the validity of the aforesaid methodology adopted by this thesis.The thesis also proposes a hierarchical identification method for key components in order to solve the problem that most identification methods can only give ranking results,which will negatively affect the operator's hierarchical protection and targeted protection.Considering the way of network operation,such proposed method can accurately locate the important grades of the evaluated nodes and lines based on the previous calculation of importation regarding nodes and lines.The simulation results verify the rationality of this proposed method.