A Robust UDE-Based 2DOF Controller for Mitigating Sub-Synchronous Control Interaction in Wind Power Plants.

Sustaining large amount of power flow in the wind power plant, series capacitors are incorporated with the transmission line system which can cause subsynchronous control interaction (SSCI) in the doubly-fed induction generator (DFIG). This SSCI effect can lead to system instability. To damp SSCI in DFIG, several traditional controllers are involved but it leads to poor damping response. To solve this issues, a new controller based on the uncertainty and disturbance estimator and two degree of freedom (UDE-2DOF) controller is proposed. The proposed controller gives the controlled output based on the input control signal like reference and actual value of the d-q axis rotor current. With this evaluation, the proposed controller damp out the SSCI in a series-compensated DFIG. Then, the effectiveness of the proposed control scheme is verified in the MATLAB platform. Both eigenvalue analysis and time-domain simulations are carried out for analyzing the system stability and SSCI damping. The results indicate that the proposed method can mitigate the SSCI within 2.5 sec. Furthermore, the variation in wind speed and the level of series compensation plays an important role on the overall system's stability especially at low wind speed (7 m/sec) and high compensation level under 45%. [ABSTRACT FROM AUTHOR]