The wide access of new energy power electronic equipment, in which wind power systems are typical, causes significant changes in traditional power grid. In this paper, based on the single-infeed infinite power system, the relation between voltage stability and the power transmission characteristics is discussed through mathematical derivation under per unit system, and the influence of the power grid strength on voltage stability is illustrated. Then, the characteristics of power limit trajectory of P-I curve under the condition of variable reactance are studied. Finally, based on these characteristics, the switch control method of DFIG model in MATLAB/Simulink is proposed, and the results shows that the voltage stability of the system is improved.

voltage stability;power grid strength;power limit trajectory;Doubly Fed Induction Generator(DFIG);switch control method