Abstract: The vector control of doubly fed induction generations（DFIGs） depends on accurate information of the stator flux or terminal voltage. Dynamic of phase lock methods affects behavior of DFIGs and thus influences the power systems small signal stability. With increased penetration of wind power, this impact should be carefully evaluated. This paper investigates the influence of DFIG with Phase lock loop（PLL） and flux observer dynamics on low frequency oscillation by using an analytical approach based on eigenvalue analysis. It shows that different phase lock mechanism with different parameters varies the effects brought by DFIG with respect to power systems electromechanical modes. The forced small disturbance signal within PLL and flux observer could stimulate forced power oscillation of power systems. Results are verified by numerical simulations.