Static Stability Index Of Power System And Study On The Coupling Relation Between Power Angle Stability And Voltage Stability

With the development of power system,the power network has become very complex.System instability will have a significant impact on the system network and social economy,so it is necessary to study the stability of power system.Voltage stability of load nodes and power angle stability of generator nodes affect the stability of power system.The complex coupling relationship between these two kinds of stability affects the stability of the whole power system.Therefore,the analysis of the coupling relationship between voltage stability and power angle stability is of great significance in the study of power system stability.For the power angle stability of the system,the relative synthesis equivalence method is studied to analyze the power angle stability of the complex system with the active power extremum of the injection system node.In power system,when the active power injected into the generator node reaches the limit value,the generator node reaches the limit state of power angle stability,thus defining the index to evaluate the power angle stability of the generator node.Based on the method of relative synthesis equivalence,the complex system is regarded as a single machine infinite bus system from the point of view of any generator node,and the static power angle stability evaluation index of generator is proposed.Based on this method,any complex system can be simplified to a single-machine infinite-bus system for distributed analysis of power angle stability.Its significance lies in: 1)the power angle stability of the system can be judged from any generator node of the system;2)in stable operation state,the power angle stability of each node can be ranked by comparing the magnitude of the power angle stability index.For system voltage stability,a transient impedance model with constant transient potential is established by simulating generator branches.The power angle stability evaluation index of generator nodes is further extended to load nodes,and a new index for evaluating the voltage stability of load nodes is proposed.The characteristics of the new voltage stability index based on the relative integrated equivalent are studied.Compared with the impedance mode margin voltage stability index,the new voltage stability index based on the relative integrated equivalent has better linearity,and can more accurately judge the voltage stability limit power of load nodes,or the new voltage stability index has better linear relationship with the limit power margin.The simulation results show that the new voltage stability index based on the relative comprehensive equivalent can accurately judge the static stability limit state of the system.Based on the proposed evaluation index of voltage stability and power angle stability,the coupling relationship between voltage stability and power angle stability of complex system isstudied by analyzing the influence of power change of load node on power angle stability of generator and the influence of power change of generator on voltage stability of load node.The simulation results show that the coupling relationship between power angle stability and voltage stability of power system is closely related to system structure,operation status and distribution characteristics of load and generator.1)The power angle stability of generator nodes farther away from the balance node is more easily affected by the system voltage stability,while the voltage stability of load nodes is more easily affected by the distance balance.The influence of the power angle stability of generator nodes with closer nodes;2)In the system with dispersed distribution of generator nodes,power angle stability plays a dominant role in the stable operation of the system,while in the system with centralized distribution of generator nodes and balanced nodes,voltage stability plays a dominant role in the stable operation of the system.3)When the influence of voltage stability on power angle stability is great,the influence of power angle stability on voltage stability is not necessarily great,and vice versa.It also proves that the conclusion that one of the two kinds of stability plays a dominant role in the stable operation of the system is correct.The research results of this paper reveal the relationship between voltage stability and power angle stability of power system,which has a certain practical guiding significance for improving the stability of power system.