Abstract: The interaction between the direct-drive wind turbines and the weak AC grid or flexible DC transmission system will easily lead to wideband oscillation events. It is generally believed that the interaction characteristics between direct-drive wind turbines and AC/DC power grids mainly depend on the grid-side converters, so the dynamics of the generator-side system of directdrive wind turbines are usually ignored. There have been some literatures discussing the influence of the generator-side system under traditional vector control on the grid-connected characteristics of direct-drive wind turbines, but there is a lack of relevant research on the generator-grid coupling characteristics for direct-drive wind turbines with different control strategies. In this paper, the generator-grid coupling characteristics of direct-drive wind turbines with four typical control strategies are compared. First, the detailed impedance models of direct-drive wind turbines with different control strategies are derived and verified. Then, based on the generator-grid coupling degree index, the generator-grid coupling characteristics of direct-drive wind turbines are compared and analyzed, and the influence of generator-side system dynamics on AC impedance characteristics and grid-connected stability of direct-drive wind turbines with different control strategies is obtained. Finally, the correctness of the theoretical analysis is verified by the case analysis of direct-drive wind turbines connecting to weak AC power grid.