Research On Voltage Stability Of Load Characteristics Based On Bifurcation Theory

Along with the development of economy and society, types of loads are growing quickly. Because the load may cause the voltage instability problem, severe cases can lead to voltage collapse. The traditional analysis method carried on under the static environment. The dynamic part of system is ignored. Bifurcation theory as an efficitet tools to inquire into the stability of a nonlinear power system surmount of the limitations consider dynamic and static separation. It is better to make a discussion on the mechanism of structural stability.Firstly, thesis used the bifurcation theory and the extension algorithm to analysis influence of load on voltage stability under consideration of static load characteristics, first class of dynamic Walve load, power recovery characteristic of second kinds of dynamic load and the combination of dynamic and static based on single parameter. Secondly, on the basis to active power and reactive power as bifurcation control double parameters it has been searched two-dimensional bifurcation point. Bifurcation curve included the Bogdanov-Takens(BT), Generalized Hopf(GH), Zero Hopf(ZH) and double Hopf(HH) bifurcation. This dissertation studied the problem of the instability of different voltage caused by these bifurcations. Static Var Compensator(SVC) can improve the voltage stability. The influence of SVC voltage gain and time constant on the two-dimensional bifurcation boundaries and bifurcation point is analyzed by simulation. Two-dimensional bifurcation contributed to a more comprehensive reveal the load evocable by the essence of voltage instability.The single parameter bifurcation analysed of impact load characteristics of good identification points out that the bus voltage will occur in Saddle Node Bifurcation(SNB). The stability of the system with high voltage level and the voltage within a small range oscillation, voltage can not reach the limit operation point. Two-dimensional bifurcation boundaries show that reactive power disturbance easily caused the voltage instability in the impact load. Active power disturbance voltage can cause voltage oscillation.It is point out that different control parameters influence the voltage stability in different ways.The purpose of two-dimensional bifurcation study pointed out that the voltage has different instability modes in GH, BT, ZH and HH point. The voltage gain of the SVC expand two-dimensional boundary, the time constant to improve numerical bifurcation point. The impact load has a great influence on the small stability region. Two-dimensional bifurcation analysis method has great significance for the influence of different components on the voltage stability.