A proposed methodology for mollification of subsynchronous oscillation in DFIG-based wind farm

High levels of series compensation in transmission lines, particularly those integrated with wind farms, exacerbate the risk of sub-synchronous oscillation (SSO), a phenomenon detrimental to system stability. Gate-controlled series capacitor (GCSC) is one of the used means to mitigate the SSO and enhance power transfer capability. In the previous studies, the combined proportional-integral controller with supplementary damping controller was an effective approach for controlling the GCSC and mitigating the SSO. In this paper, the ability to cascade a proportional-resonant controller with a PI controller for damping the SSO is investigated. The proposed method's performance is evaluated through extensive time-domain simulations using the modified IEEE First benchmark model. The simulations incorporate a diverse range of wind speeds, compensation levels, as well as sub-synchronous control interactions. Furthermore, a comparative analysis with recent SSO damping techniques is conducted to assess the strategy's performance under varying operating conditions. The comparative results overwhelmingly demonstrate the superiority and effectiveness of the proposed strategy in alleviating SSO, especially at low wind speeds and high compensation levels.