Abstract: Renewable energy power sources, represented by wind power generations, deliver clean energy to load centers via long-distance AC transmission lines. The dynamic interaction between grid-side converters and phase-locked loops may lead to wide-frequency oscillation instability for grid-connected direct-drive wind turbines in extremely weak grid. To improve the stability of wide-frequency oscillations of permanent magnet synchronous generators in extremely weak grid, in this paper we firstly derive a full-order block diagram model of grid-connected PMSG considering the time scales of DC voltage and AC current control. Subsequently, the principle of parameter tuning of grid-side converter and phase-locked loop vector control system in extremely weak grid conditions is proposed, considering the time scales of DC voltage and AC current. As a result, the grid-connected PMSG can always maintain stable operation under the condition that the short-circuit ratio exceeds 1. Finally, the effectiveness of the proposed control parameter tuning method is verified through eigenvalue analysis and nonlinear simulation with an exampled single grid-connected PMSG system.