Research On The Recognization Of The Critical Nodes And Critical Lines In Power Systems

At present,the scale of power system in China is still expanding.The further complication of network structure is unavoidable,which makes the system face severe security problems.It is of great significance to identify the critical nodes and critical lines of the power system by a reasonable method,which can detect potential risks and safeguard social interests in time.This paper will focus on the identification of critical nodes and lines of power system,and propose a new identification method.The specific research contents of this paper include the following aspects:(1)In this paper,a comprehensive identification model of critical nodes is proposed,which is established from two systems of grid-network topology and running state.(2)In grid-network topology of identification model of critical nodes,Laplace matrix is proposed,which is based on DC power flow.Based on Laplace matrix,nodal coupling index which can measure the global connectivity tightness of a node is established,and the scale-free properties of the power system are verified.Besides,the theory of node entropy is introduced to measure local connection of nodes,and the types of nodes is considered in this index.(3)In running state of identification model of critical nodes,Theil ent ropy is introduced and nodal power fluctuation Theil entropy is defined.In this index,the lines are classified according to the load rate of the line,and the fluctuation of power flow of the system is measured by the nodal power fluctuation Theil entrop y.Besides,in the light of the State Council Decree No.599,the load is increasingly important.A key index is defined,which is measure the system load loss after the failure of node.The power flow betweenness is used to measure the occupancy of the power flow to the node under normal operation of the system.The factors such as node voltage level and site scale are used to correct the results of the power flow betweenness.(4)On the critical lines,a fast calculation method of flow transfer is given in this paper based on Laplace matrix.The method is easy to calculate the transfer power flow and determine the influence area of transfer power flow when the line is disconnected.The calculation methods of inproved transfer power flow entropy and the sensitivity entropy of load impact are given.Improved transfer power flow transfer entropy index to effectively characterize the uniformity of transfer power flow according to the distribution of line capacity.The sensitivity entropy of the load impact sensitivity can be used to effectively evaluate the sensitivity of the line to each node load.(5)The analytic hierarchy process and entropy weight method are used to analyze the main and objective weights of each sub-index,and the error introduced by the single weight is reduced as much as possible.Finally,The simulation verification of IEEE 39-bus system is done,which shows that the validity of the method presented in this paper.