Research on Suppression Strategies for Multifrequency Subsynchronous Oscillations in DFIG‐Based Wind Power Generation Systems

ABSTRACT When a subsynchronous oscillation (SSO) disturbance occurs in the grid, the phase‐locked loop (PLL) and the converter control loops of doubly‐fed induction generator (DFIG)–based wind power generation systems interact with it. This interaction can excite multifrequency subsynchronous oscillations and threaten the safe and stable operation of the system. This paper proposes a suppression strategy for multifrequency SSO in DFIG‐based wind power generation systems. The strategy is based on the sparse Fourier transform (SFT) algorithm. First, we consider the phase perturbation introduced by the PLL and analyze the mechanism of multifrequency SSO in DFIG‐based wind power generation systems. Then, the rotor‐side converter (RSC) control loop is examined. The optimal insertion point of the notch filter is determined by comparing the damping performance at different connection nodes. Next, the sparsity of the sampled current signals in the frequency domain is verified. Based on this property, a new SFT‐based observer is designed to identify SSO‐related state variables online. Its observation performance is compared with that of conventional observers. Furthermore, a parallel multifrequency adaptive notch filter (PMFANF)–based suppression strategy is developed. It uses the online identification results of the proposed observer to attenuate multiple SSO components simultaneously. Finally, simulation studies and experiments on a DFIG‐based test platform are carried out to validate the effectiveness of the proposed suppression strategy.