Vulnerability Assessment Combining Korder Structure Entropy And Interval Electrical Betweenness For Power Grid With Wind Power

With the large-scale development and utilization of clean energy such as wind energy as well as the growing complexity of the power grid structure,there have been many domestic and foreign large-scale wind-power off-grid blackout accidents in recent years.It brings new challenges to the safe and stable operation assessment of the power system.Due to the volatility,randomness and uncertainty of wind-power,windpower integration can change the power grid structure characteristics and cause the great change of the power flow distribution at the same time,which improves the difficulty of the vulnerability assessment of the power system.As a result,in order to assess the vulnerability of power grids accurately,the effect of wind power integration on the system topology and the power flow distribution as well as the impact scale of nodes of the power grid vulnerable node group and the vulnerability of power grids from the locality to globality of the system is assessed comprehensively in the paper.To describe the wind power volatility and its impact on power grid vulnerability,the method of identifying the vulnerable components of wind-power grids based on the interval electrical betweenness is proposed to identify the vulnerable lines and nodes of power grids so as to further determine the central node of the vulnerable node group of power grids.The interval number is adopted to describe about the fluctuation of wind-power output and establish the vulnerability index of the interval electrical betweenness.The vulnerability index of the interval electrical betweenness is sorted on the basis of the ranking method of the interval number of the possibility degree.Through the simulation analysis of IEEE-39 and IEEE-118 node systems,the results show that the method can be adopted to identify the vulnerable lines and nodes accurately and quickly and verify the validity and rationality of the method.Considering the influence scale of vulnerable nodes in power grids,the method of identifying vulnerable nodes of wind-power grids based on the K-order structural entropy is proposed.The K-order structure entropy model is built to describe the network structure distribution and the minimum K-order structure entropy of the system to represent the highly unbalanced network structure is calculated.Then,the K-value is determined as the influence scale range and the nodes with high node degree and high interval electrical betweenness are taken as the center nodes to identify the vulnerable node group of power grid.The simulation results of IEEE-30 and IEEE-39 node systems show that the vulnerable node group can clearly reflect other neighbor nodes affected by the central node of the vulnerable node group to some extent,which plays a great role in the prevention of large-scale cascading faults of power grid.In order to assess the balance of each node group in wind-power grids comprehensively and accurately,an assessment method of the node group equilibrium based on the interval electrical betweenness entropy is proposed from the perspective of power flow distribution.The average interval electrical betweenness distribution rate is taken as the weight to build the interval electrical betweenness entropy index of wind-power grid connection.Through simulation analysis,it is showed that it is possible to describe about the distribution equilibrium characteristics of node power and line power flow of each vulnerable node group of power grids effectively through this index.Compared with the vulnerable node group centered on the low interval electrical betweenness node,the vulnerable node group centered on the high interval electrical betweenness node is endowed with the more uneven distribution equilibrium of node power and line power flow.The risk probability of cascading failures of power grids is higher and the vulnerability of power grids is more prominent.Meanwhile,it is verified that the scientificity and accuracy of the proposed identification method for vulnerable node groups in wind-power grid based on the combination of K-order structure entropy and interval electrical betweenness.