Sub-Synchronous Oscillation Suppression Strategy with Additional Air-Gap Magnetic Chains

The application of series capacitor compensation technology often triggers the phenomenon of sub-synchronous control interaction (SSCI) in doubly-fed wind farms, and since the traditional strategy has the problems of poor control performance, low economy, and cumbersome and complex structure, this paper proposes an additional air-gap magnetic chain suppression strategy to improve the positive damping of the system and inhibit the oscillation dispersion. The method utilizes the SOGI structure to extract the subsynchronous oscillatory components in the stator current and rotor current of the doubly-fed wind turbine generator (DFIG), and then utilizes a quasi-resonant controller to carry out closed-loop control of the subsynchronous air-gap magnetic chain so as to achieve the purpose of suppressing the SSCI. Finally, this paper builds a time-domain simulation model of doubly-fed wind farm based on MATLAB/SIMULINK to verify the feasibility of the additional air-gap magnetic chain suppression strategy of sub-synchronous oscillation. The results demonstrate that the additional air-gap magnetic chain suppression strategy can improve the positive damping of the system under different wind speeds and series compensation degrees, thus suppressing the dispersion of subsynchronous oscillations in doubly-fed wind farms.