Design of a damping controller for a SMES unit to suppress tie-line active-power fluctuations of a large-scale wind farm

This paper designs a damping controller for a superconducting magnetic energy-storage (SMES) unit to simultaneously achieve stability improvement and suppress tieline active-power variations of a large-scale wind farm (WF) subject to wind-speed fluctuations. A complete system model based on a synchronously rotating reference frame for the studied WF combined with the SMES unit is properly derived and established. The proposed control scheme of the SMES unit is by means of adjusting phase angle of a bi-directional power converter using tie-line active-power deviation as a feedback signal. The performance of the studied WF combined with the SMES unit joined with the designed PID damping controller is demonstrated using calculated operating conditions, eigenvalue analysis, and time-domain nonlinear-model simulations. It can be concluded from the simulation results that the proposed PID SMES damping controller can effectively suppress tie-line activepower fluctuations and render proper damping characteristics to enhance stability of the studied WF under various wind-speed disturbances.