In response to SSO (subsynchronous oscillation) issue resulting from the connection of large-scale direct-drive wind turbines to a weak AC grid via power electronic devices, an improved LADRC (linear active disturbance rejection control) suppression strategy was proposed. Initially, the harmonic linearization approach was employed to construct a sequence impedance model for the grid-connected direct-drive wind power system. This model encompasses the DC voltage outer loop, DC capacitor voltage, and PLL(phase-locked loop) components. Based on this established model, the Nyquist stability criterion in the frequency domain was utilized to analyze the scenarios where system instability is induced by the variations in the control parameters of the DC voltage outer loop, the PLL, and the current inner loop, along with the alterations in the grid short-circuit ratio parameters. Subsequently, with the aim of further strengthening the system's capability to suppress subsynchronous oscillations and enhancing its anti-interference performance, a differential element and a quasi-proportional resonant element were incorporated into the traditional LADRC model. Consequently, an improved active disturbance rejection controller model was put forward. Finally, the verification outcomes from both frequency-domain analysis and time-domain simulation demonstrate that, in comparison with the traditional LADRC technique, the proposed strategy exhibits enhanced robustness and anti-interference capabilities.