When a subsynchronous oscillation disturbance occurs in the power grid

the combined action of the phase-locked loop (PLL) and the converter control loop of the doubly-fed induction generator (DFIG) wind power system will induce multi-frequency subsynchronous oscillations

which will seriously affect the safe and stable operation of the DFIG wind power system. To address this issue

this paper proposes a multi-frequency subsynchronous oscillation suppression strategy for DFIG wind power systems based on the sparse Fourier transform algorithm. First

considering the phase disturbance of the PLL output

the generation mechanism of multi-frequency subsynchronous oscillations in the DFIG wind power system is deeply explored. Combined with the rotor converter control loop

the optimal introduction position of the notch filter is determined by comparing the suppression effects of connecting notch filters at different nodes of the loop. Next

a new observer capable of online identifying the state of subsynchronous oscillation variables is designed based on the sparse Fourier transform algorithm; its observation performance for subsynchronous oscillation signals is compared with that of the traditional observer. Then

a multi-frequency subsynchronous suppression strategy with adaptive parameters of parallel notch filters is proposed based on the online identification results. Finally

the effectiveness of the proposed suppression strategy in this paper is verified under various operating conditions by building a simulation model and an experimental platform.