Published in IET Renewable Power Generation Received on 7th December 2007 Revised on 9th May 2008 doi: 10.1049/iet-rpg:20070117 ISSN 1752-1416 Power flow control and damping enhancement of a large wind farm using a superconducting magnetic energy storage unit S.-S. Chen 1 L. Wang 1 W.-J. Lee 2 Z. Chen 3 1 Department of Electrical Engineering, National Cheng Kung University, No. 1, University Road, Tainan 701, Taiwan, People’s Republic of China 2 Department of Electrical Engineering, University of Texas at Arlington (UTA), Arlington, TX 76019, USA 3 Institute of Energy Technology (IET), Aalborg University, Analog, Denmark E-mail: liwang@mail.ncku.edu.tw Abstract: A novel scheme using a superconducting magnetic energy storage (SMES) unit to perform both power flow control and damping enhancement of a large wind farm (WF) feeding to a utility grid is presented. The studied WF consisting of forty 2 MW wind induction generators (IGs) is simulated by an equivalent 80 MW IG. A damping controller of the SMES unit is designed based on the modal control theory to contribute proper damping characteristics to the studied WF under different wind speeds. A frequency-domain approach based on a linearised system model using eigen techniques and a time-domain scheme based on a nonlinear system model subject to disturbance conditions are both employed to validate the effectiveness of the proposed SMES unit with the designed SMES damping controller. It can be concluded from the simulated results that the proposed SMES unit combined with the designed damping controller is very effective in stabilising the studied large WF under various wind speeds. The inherent fluctuations of the injected active power of the WF to the power grid can also be effectively controlled by the proposed control scheme. Nomenclature General p differential operator with respect to t ( p ¼ d/dt ) v, i quantities of voltage and current R, X quantities of resistance and reactance C excitation capacitor bank v, u, H rotor speed, rotor angle and inertia of IG T m , T e mechanical torque and electric torque of IG R L , X L resistance and reactance of local load R T , X T resistance and reactance of transmission line D Hg damping coefficient between hub and IG K Hg stiffness coefficient between hub and IG m 1 , a C modulation index and phase angle of SMES unit V W wind speed V WB base wind speed V WG gust wind speed V WR ramp wind speed V WN noise wind speed WF wind farm Gen. generator RSC relative sensitivity coefficient Subscripts d, q d- and q-axis quantities s, r stator- and rotor-winding quantities of IG H, g quantities of hub and IG T, L quantities of transmission line and local load SM quantities of SMES unit grid grid side IET Renew. Power Gener., 2009, Vol. 3, No. 1, pp. 23–38 23 doi: 10.1049/iet-rpg:20070117 & The Institution of Engineering and Technology 2008 www.ietdl.org