Research On Influence Of Long-Term Model And Required Parameters On Voltage Stability And Corresponding Countermeasures

With the completion of the national power grid interconnection and power channel, it can achieve efficient allocation of resources, improve the power support among regions. But the power grid load center of gravity increasing voltage stability problem will become more serious. Depending on the time scale voltage stability can be divided into transient voltage stability and long-term voltage stability, transient voltage stability time domain typically range from a few seconds to tens of seconds, medium and long term voltage stability range generally lasted more than a few minutes, mainly influenced by the dynamic characteristics of long-term model. Only fully consider the long-term model and description of the dynamic characteristics of the system components in different periods, the voltage stability problem can be revealed after a large disturbance occurrence and a new equilibrium point can be obtained. This paper analyzes the operation principle and operation strategies are long-term model, and actual grid data model and study the effects of long-term parameters on the dynamic process, and it gives a reasonable control measures for long-term voltage stability.Firstly, the research statuses about the action principles and operation strategy of the main medium and long term models, such as boiler model, On-Load Tap Changer (OLTC), excitation limiter model, low voltage capacitor/low voltage reactor automatic cutting and automatic generation control (AGC).Secondly, the fast medium and long-term modeling tool is developed based on the C language. The tool is based on BPA trend, stable data reading system of generators and transformers node, and in accordance with the requirements specified by the user to establish a boiler model, excitation limiter model and On-Load Tap Changer network-wide data. The influence of single medium model (boilermodel, excitation limiter model, OLTC model and AGC model)on dynamic process is analyzed adopting the actual power grid data. The necessity of the medium and long term model is analyzed qualitatively. The impact of the model parameters for the medium and long term models on the simulation results are analyzed quantitatively.Finally, a coordinated control method based on the on-load voltage regulating transformer and low voltage capacitor/low voltage reactor automatically cutting is demonstrated. The method is for the voltage restored to its predetermined value during the dynamic recovery process after a large disturbance untill a new equilibrium point for the power grid based on the existing reactive power compensation device. To achieve coordinated action of the two models,when fully operational substation low-voltage capacitor and LV Reactors entire anterior resection allowed OLTC action, or to lock OLTC, and through some practical examples grid validity of the coordinated control strategy.