Sub-synchronous resonance (SSR) may be caused by the interaction between wind turbine series compensation transmission system and control of doubly-fed induction generator (DFIG), which is called sub-synchronous control interaction (SSCI). To analyze this phenomenon and provide corresponding suppression measures, the relation between SSR circuit and control of DFIG is explored deeply, and two strategies are proposed, including the detailed design methods. Furthermore, the paper analyzes the restrained effects on SSR by using additional damping control with different filters. Eventually, the discussed strategies have been verified through Matlab/Simulink, which provides a theoretical support to solve the SSR caused by SSCI in the wind farm.