Study Of The Dynamic Behavior And The Key Node Identification On Complex Power Networks

The study of nonlinear dynamics of power networks based on complex network theory has become a new direction of academic researches.By studying the characteristics of the network structure,it can help us to better understand the various dynamic behavior of the power grids and better explain the large-scale power outage in the power grids,thus we can take effective measures to the vulnerability of power grids to reduce the probability of cascading failures,which can maintain the power grids reliability operation.Considering the network topology structure and the network dynamic characteristics,this paper deeply studies several problems,such as the synchronization model of the power grids,the key nodes identification and the distributed power station connection modes.The specific research contents are as follows:1?According to the derivation of the model dynamic expression,we can compare the similarities and differences about the modeling method and the network dynamic behavior between the power grid models based on load equivalent:the EN model,the SM model and the two order Kuramoto-like model.It is found that load nodes are modeled as motor nodes in the SM model and the two order Kuramoto-like model,and the difference between the two models is that whether to ignore some of the actual characteristics of the power grids,such as the line impedance,the node voltage.When we ignore the partial actual characteristics of the power grid,the SM model is reduced to the two order Kuramoto-like model.When we are modeling the power grids using the EN model,the load node is equivalent to the constant impedance,so the dynamic equation is established only for the generator node.Meanwhile,the number of equations and calculation are less than that of the SM model.From the point of view of the network dynamics,when we use the same IEEE standard test system to study the synchronization characteristics,the simulation experiments show that the power grids using the EN model operate at standard frequencies and the power grids using the SM model operate at a certain frequency near the standard frequency.Although the dynamic behavior of modeling the power grids using the different models is different,these models can describe the frequency synchronization state when the power grid is in stable operation.2?In order to effectively identify the key nodes in the network,a comprehensive index of node importance recognition which considers the local and global characteristics of the network is proposed in this paper.The nodes in the weighted standard test system IEEE39 and IEEE118 are sorted according to their importance based on this index,and the ranking results are compared with those based on betweenness centrality method and the point weight method,meanwhile these important methods of node recognition are compared using structure-based network efficiency analysis and dynamics-based loss-of-synchronization diffusion time and synchronization capability,the results show that ranking of node importance based on the comprehensive index of this paper is more reasonable,which is superior to node recognition method based on betweenness centrality and the point weight.3?The distributed power stations are connected to the power grid through the load nodes of the original power grid.According to the average distance of each load node to all generator nodes in the original power grid,two kinds of distributed power plant connection modes are put forward,one way of which is that the new joining distributed power plants start from the load node of the minimum average distance to the original generator nodes,and the rest of distributed power plants are connected to load nodes according to the average distance value in ascending order,which is called A mode;the other is that the new joining distributed power plant start from the load of the maximum average distance from the original generator nodes,and other distributed power plants are connected to load nodes according to the average distance value in descending order,which is called B mode.From the grid statistical characteristics and synchronization dynamics point of view,it is found that the network nodes are more distributed and the synchronizability of the network is better when the distributed power plants are connected to the power grid using B mode.At the same time,the diffusion rate of the grid loss synchronous wave caused by the low power disturbance is slower with mode B used when the disturbed node is close to the power stations,which is beneficial to the stable control of the grid.This research has some guiding significance for improving the reliability operation of the power grid when the distributed power stations are connected to the grid.