The Bifurcation Analysis On Dynamic Voltage Stability Of Wind Power System

With the continuous development of wind power technique, the influence area of wind power integration on power system are gradually enlarged. No matter the size of installed capacity of wind driving power, which kind of wind turbine technology is used, the wind power integration can transform the original power flow distribution of system, transmission power of lines and so on .It is because that the randomness and uncertainty of wind energy, the reative characteristics of induction motor, lackness of voltage control and measures, etc. Owing to the voltage stability was usually considered is the problem of loading capacity in system, and the load models are the main dynamic element which have great effect on voltage stability in power system.The bifurcation process of Generator power angle with the reactive load is analyzed in five kinds of the static and dynamic load models by the bifurcation theory.The simulation results show that the choice of load models is implications for the way of instability system.It is certain significance to use the appropriate load model in dynamic stability analysis for the power system.It also should consider the dynamic load models to establish dynamic models of power system, then select the appropriate method to dynamic analyze for wind power access system.Presently bifurcation theory is currently limited to single-parameter bifurcation analysis, and stability of power system is the complex dynamic characteristics which shows by interaction of many independent parameters, so only consider the function of a certain control parameter would cover up the mechanism of voltage instability. In wind power system, the power injection of wind power and reactive load as two important parameters have influence on voltage stability and the influence can not be completely decoupled. Selecting power injection of wind power and reactive load for bifurcation parameters to carry on two-parameter bifurcation analysis can more clearer obtain the influence degree of each parameter on the dynamic voltage stability, comparing with respectively selecting power injection of wind power and reactive load for bifurcation parameters to carry on single-parameter bifurcation analysis. In order to obtain the impact which the power injection of wind farm parameter and reactive load parameter respectively and comprehensively on dynamic voltage stability in wind power. For a typical power system, using induction generator based wind farm and doubly-fed generator based wind farm, adding dynamic load model, two kinds of wind power dynamic models are analyzed with single-parameter bifurcation and two-parameter bifurcation. The process indicate that the method by two-parameter bifurcation is superior to that by single-parameter in revealing the influences of system-parameters on voltage stability of wind power system .The results imply that overweight reactive load would enormously reduce system stability margin when power injection continuous increasing, in both of two wind power system under the same structure and parameters; when power injection keeps constant, the variation of reactive load would not affect system stability; the system can reach to the highest efficient operation if avoid the situation that overweight reactive load with power injection continuous increasing by adjusting power injection and reactive load; the stability of doubly-fed generator based wind power system is much better than induction generator based wind power system, and doubly-fed generator based wind power system can obtain much more accurately system stability margin.