The invention discloses a broadband additional sub/super synchronous oscillation control method and control system. The method includes acquiring the total three-phase current ic on the fan side or the total three-phase current iL on the line side; filtering out the subsynchronous and supersynchronous harmonic components; compensating the phase delay, and/or performing at least one of phase offset and amplitude compensation; converting the current signal into the reference current ISVG of a stationary reactive power generator; calculating the additional control signal sent to the stationary reactive power generator according to the reference current ISVG and the reference value received by the stationary reactive power generator; and adjusting the additional control signal. The control method and control system are advantageous in that the total current of the fan side or the line side is acquired in real time, the additional control signal is calculated, and by controlling the stationary reactive power generator, the stationary reactive power generator is equivalent to the inductive impedance parallel to the bus at the sub/super synchronous frequency at which the resonance occurs to destroy the condition of the system resonance generation, thereby effectively suppressing the sub/super synchronous resonance of the system when the wind farm is connected.