In recent years, with the increasing capacity of grid-connected wind farms, the interaction between wind power generation systems and power systems has received more and more attention. In this paper, the influence of DC voltage control of the PMSG (Vdc control) on the electromechanical oscillation stability of 4-machine 2-area power system is studied from the perspective of Vdc control parameter stability region. Firstly, the linearized closed-loop interconnected model of the power system is established. Based on the established model, the modal analysis method is applied to calculate the DC voltage control parameter stability region of the PMSG. The results show that strong interaction between the PMSG and the system can be induced by the modal resonance which results in a large reduction of the area of the parameter stability region. Moreover, the correctness of the theoretical analysis is verified by nonlinear simulation.