Research On Stability Evaluation And Countermeasures Of Hebei Southern Power Grid Under The Condition Of UHV Multi Drop

Our country is actively developing AC 1000kV and DC 800kV UHV project,its purpose is to strengthen the connection between the various power grids.Withthe contact line between the provinces has been strengthened,the transmission capacity of provincial section mainly depends on the thermal stability limit,which can not make full use of the transmission capacity of the lines.In the vicinity of UHV point,the current collection or delivery will be more concentrated,resulting in uneven distribution of power flow in each provincial cross section.When the double circuit with heavy loads takes place N-1 failure,power flow will transfer to another line of the smae channel.As a result,this line will be overloaded and if not timely treatment,the possible cascading failures will lead to unestimated risks and losses for the system operation.In this paper,aiming to the safety and stability problem of Hebei Southern network.the dynamic simulation of the southern Hebei network is carried out and the countermeasure is investigated.Firstly,this paper studies the modeling methods of dynamic components in the whole process of dynamic stability simulation.Based on the study of the medium and long term dynamic process of Hebei south network,generator over excitation limit model with a model parameters test,on load tap change model and elay protection and automatic safety device model are established.Then,based on the established dynamic model of the whole process,5 failures include in South Hebei 500kV line and transformer N-1 fault,South Hebei 500kV line N-2 fauit,Hebei South Network out zone fault are simulated in order to analyze the whole dynamic process with system disturbance.In view of the safety and stability problem of Hebei Southern Network under the condition of multi UHV point,this paper studies control effect of SVG in the middle and long term dynamic simulation.Finally,,this paper studies the basic principle and control method of UPFC,and a allocation method aiming to improving the heat stability margin and transmission capacity the maximum transmission capacity of lines is proposed,and the simulation verifies the correctness and effectiveness of the method proposed in this paper.