The present disclosure is directed to a system and method for stabilizing sub-synchronous interaction (SSI) of a wind turbine generator connected to a power grid. More specifically, the method includes measuring an alternating-current (a-c) quantity of the power grid. Another step includes converting the a-c quantity to a d-q quantity and providing the d-q quantity to a d-q control loop within the controller. Another step includes altering, with a symmetric control component, a transfer function of the d-q control loop. The method also includes generating at least one d-q reference signal for the wind turbine generator based on the altered transfer function so as to achieve symmetric control of the generator. A further step includes generating a control signal for the generator based, at least in part, on the at least one d-q reference signal. The method also includes operating the generator based on the control signal.