Study On Influencing Factors Of Power System Voltage Stability

Modern power system is developing into the direction of large capacity and extra-high voltage. The enlargement of the electric network scale brings magnitude economy and society benefits, but at the same time the issue of power system stability becomes more severe.Rotor angle stability and voltage stability are the two aspects of the power system stability. Rotor angle stability is the capability of the generators of the electric network to keep synchronization.. The research of the rotor angle stability began earlier, which theory is complete, while the research on voltage stability began later, which began in the 70's of the last century. The reason of the voltage stability becoming an independent research subject is that many voltage instability events came forth without any evidence of rotor angle unstability . The voltage collapse appears suddenly , and the destruction sequent is huge. Now the research on the voltage stability is causing increasing attentions.First the paper analyzes the mechanism of the voltage stability. The physical essence of the power system stability issue is the power balance .The lack of reactive power is the reason of the voltage unstability. The required premise of the small disturbance stability is the existence of intersection point on the reactive-voltage characteristic curve of the electric source and the load, and related to the differential value of the reactive to the voltage. The large disturbance stability also depends on the rate of the reactive power between electric source and the load. The voltage stability is also regarded as load stability ,because the bad characteristic of the asynchronous motor is reckon as the main reason of the voltage unstability. There is another point which deems the limitation of the transmission line is the cause of the voltage unstability. The static power flow is based on this point to analyze the voltage stability ,and such methods less consider the characteristic of the load. Although there is limitation on this point , it is meaningful to understand the voltage stability from another point of view.The paper analyzes the characteristic of some reactive power like the synchronous generator ,static reactive compensator, shunt capacitor. In addition the paper analyzes the load characteristic with the asynchronous motor ,and the function of transmission line and the transformer in transmitting reactive power. The paper makes a study on the influencing factors on the small disturbance voltage stability and lager disturbance voltage stability . Based on the mathematics model of the power system components, the paper uses the software of SIMULINK in MATLAB to process dynamic time domain simulation .By the contrast of the simulation results, the paper analyze different kinds of reactive source in the aspects of different capability ,respond speed ,as well as different disturbance ,the length of the transmission line, load characteristic . The paper discuss the influencing factors of the voltage stability from the aspects of electric source , load ,the frame of the electric network. At last the paper put forward some strategies and measures to improve the power system stability ,which are worth of referring in power system programming and operation.