The Analysis Of Voltage Stability Of Power System Containing DFIG Based On Bifurcation

With the depletion of resources and the deterioration of the global environment, the new energy’s market represented by wind power is gradually increasing. As wind speed has the characteristic of randomness and the wind generator’s characteristic is different from the synchronous generator’s. Wind power will affect the voltage stability of power system when it connected to power grid.The shortage of reactive power is the main reason of leading voltage instability.The active power produced by wind generator is increased with the rise of wind speed,which lead to voltage instability, if power system has not enough reactive power. Using bifurcation theory, this paper analyzes the impacts of two different models of DFIG on voltage stability and propose an improved DFIG’s model, on this basis, design a controller which can clear Hopf point.The main contents are summarized as:1) To a typical WSCC three machines-nine points power system, continuation method is used to track the balance flow of power system connected or not connected by DFIG, and the bifurcation points are searched by calculating the eigenvalues of system state matrix point by point based on bifurcation theory.2) Different DFIG’s model have different impacts on voltage stability margin. The balance flow of grid connected static state DFIG and dynamic DFIG, the influence of the two DFIG’s model on voltage stability are analysised. About dynamic model, propose a means to process DFIG’s rotor value, that is, the value is replaced by steady-state model value of DFIG, and analyzed its simulation result compared to fixed rotor value. The improved DFIG model was verified by an example above though time-domain simulation.3) SVC can improve voltage amplitude of power system, but at the same time, power system may occur new bifurcation point, it will lower the voltage stability margin. The impact of different SVC model on voltage stability were analysised. A novel SVC model based on washout filter control technology was proposed, this model can control Hopf bifurcation occurred in wind power system, it can not only improve the voltage amplitude of power system, but also clear the Hopf bifurcation point, expand the voltage stability margin. Finally, the novel SVC model was verified by an example above though time-domain simulation...