Double fed wind turbines (DFIG) have become mainstream models due to their excellent performance and economic benefits. However, the series capacitor compensation technology adopted to improve transmission efficiency can lead to sub-synchronous oscillations (SSO) due to resonance with grid parameters, threatening the stability of the power system and the safe operation of wind turbine units. In order to solve this problem, an in-depth analysis of the SSO characteristics of doubly fed wind farms is conducted, and the typical wind farm at China Hebei Guyuan is equivalent to two far and near wind farms, an equivalent impedance model considering the DFIG converter control link and PLL accuracy is established; Then, the impedance analysis method in the frequency domain is used to analyze the effects of wind speed, line series compensation, wind farm capacity, and PI control parameters of DFIG converter on system stability, it is found that the SSO stability of the wind farm is inversely proportional to the RSC current inner loop PI ratio coefficient and series compensation, and directly proportional to wind speed and the ratio of far and near wind farm capacity; Finally, the time-domain simulation analysis method is used on MATLAB/Simulink software to further verify the correctness and accuracy of the impedance analysis results. The research conclusion of this paper is of great significance for understanding the dynamic characteristics of wind power generation systems and designing effective SSO suppression strategies. Based on the analysis of SSO characteristics, the proposed linear active disturbance rejection control (LADRC) for SSO suppression strategy can effectively suppress SSO.