HPF-LADRC for DFIG-based wind farm to mitigate subsynchronous control interaction

Abstract

• The HPF-LADRC is introduced to replace the traditional PI controller on the wind turbine's rotor side converter. Firstly, the estimate and feedback of the system's subsynchronous oscillations are implemented using linear extended state observer (LESO) in the LADRC. • An HPF is added to the linear state error feedback (LSEF) in the LADRC to mitigate low-frequency oscillation. • Time-domain simulations and impedance model-based analysis are performed to validate the proposed suppression technique for SSCI under different wind speeds, compensated levels, and the number of in-service DFIGs. Doubly-fed induction generator (DFIG)-based wind farms interact with series capacitors in transmission lines, leading to sub-synchronous control interaction (SSCI). The SSCI's oscillation frequency is affected by the system's operating conditions. Therefore, this paper proposes the linear active disturbance rejection control (LADRC) based on the high-pass filter (HPF) to mitigate SSCI under various conditions. The HPF-LADRC is introduced to replace the traditional PI controller on the wind turbine's rotor side converter. Firstly, the estimate and feedback of the system's subsynchronous oscillations are implemented using linear extended state observer (LESO) in the LADRC. Then, an HPF is added to the linear state error feedback (LSEF) in the LADRC to mitigate low-frequency oscillation. Finally, time-domain simulations and impedance model-based analysis are performed to validate the proposed suppression technique for SSCI under different wind speeds, compensated levels, and the number of in-service DFIGs. The results demonstrate that the proposed HPF-LADRC increases the system's low-frequency band dampness and enhances its disturbance resistance.