The　sub-synchronous　oscillations　(SSO)　caused　by　the　grid　integration　of　wind　power　have　seriously　threatened　the　safe　and　stable　operation　of　the　power　system.　Therefore,　the　suppression　schemes　of　SSO　have　attracted　extensive　attention　from　the　academic　and　industrial　communities.　However,　the　existing　SSO　suppression　methods　have　the　limitations　of　either　changing　dynamic　performance　of　the　direct　drive　permanent　magnet　synchronous　generators　(D-PMSG)　wind　farm,　complex　control　schemes,　or　high　control　cost.　To　address　these　problems,　a　novel　SSO　suppression　method　based　on　the　phase-locked　loop　(PLL)　additional　control　is　proposed　in　this　paper.　First,　impedance　sensitivity　and　the　poles　of　the　D-PMSG　wind　farm　system　are　studied,　the　decrease　of　PLL＇s　bandwidth　is　found　to　be　important　and　benefit　to　the　grid-integrated　stability.　Secondly,　a　suppression　scheme　with　additional　damping　at　the　PLL　is　proposed　to　indirectly　reduce　the　bandwidth　of　the　PLL　once　SSO　occurs.　Finally,　the　effectiveness　of　the　proposed　suppression　method　is　verified　in　time-domain　simulations　that　SSO　converges　only　in　1　second.　©　2021　IEEE.