1. 29-4-2015 Delft University of Technology Aeroelastic Modeling and Comparison of Advanced Active Flap Control Concepts for Load Reduction on the Upwind 5MW Wind Turbine Thanasis Barlas and Gijs van Kuik

2. 2 Active flap control concepts | xx Outline Introduction The model Control concepts Decentralized Individual Flap Control Centralized Individual Flap Control Decentralized Multiple Flap Control Results Conclusions

3. 3 Active flap control concepts | xx Introduction Actively controlled local aerodynamic surfaces (like flaps) can offer: -Load alleviation -Performance increase -Stability Proof-of-concept with various simulations and wind tunnel experiments already (DUWIND, Risø, NREL, Sandia, NTUA) Integrated design of control schemes limited Modern aeroelastic tools not sufficient Research campaign on evaluation of design options needed (IEA expert meeting Sandia 2008) “Smart Rotor” research

4. 4 Active flap control concepts | xx The model DU_SWAMP Modular structure in Matlab © Simulink © BEM-based with additions Hybrid Multi-Body structural modeling Virtually unlimited DOF Unsteady aerodynamics for flaps (or anything else…) Virtually any control concept can be implemented. modular aero-servo-elastic code

5. 5 Active flap control concepts | xx The model Unsteady BEM (d. inflow, turb. wake state, losses…) Tabulated Cl,Cd,Cm (quasi-steady version) Unsteady linearized aerodynamics for airfoils with control devices (unsteady version) Essential wind inputs (w. shear, t. shadow, 3d turbulence) rotor aerodynamics

6. 6 Active flap control concepts | xx The model Unsteady aerodynamics for airfoils with flaps Thin airfoils – thin flaps Indicial response in state-space form (based on Leishman) Gives unsteady aerodynamic responses to arbitrary motion, wind inputs and controls airfoil aerodynamics (+control surfaces) Cl time

7. 7 Active flap control concepts | xx The model Hybrid Multi-Body representation Superelements (blades, tower) More efficient than normal MBS 40-60 DOF structural dynamics superelement

8. 8 Active flap control concepts | xx The model Generator torque (on filtered HSS speed – 4 regions) Collective pitch (on filtered HSS speed – gain sceduling) Based on NREL’s work (Jonkman, Namic) baseline controllers

9. 9 Active flap control concepts | xx The model Upwind (NREL) 5MW Reference Wind Turbine simulated wind turbine characteristics

10. 10 Active flap control concepts | xx Control concepts One big flap per blade (20%R) 10%c flaps Max flap angles ±10deg. Max flap rate 40deg/s definitions individual flap centralizeddecentralized multiple flaps feedbackfeed-forward Three flaps per blade (total 20%R) 10%c flaps Max flap angles ±10deg. Max flap rate 40deg/s

11. 11 Active flap control concepts | xx Control concepts Traditional SISO linear controller design Numerical perturbation linearization of the non- linear plant in Simulink © Normal PID tuning algorithms Controller design procedure

12. 12 Active flap control concepts | xx Control concepts 3 fully decoupled SISO loops PID controllers on root flapwise moment Gains tuned based on 3 linearized s-s models Linear models show periodicity (LTP) decentralized individual flap control

13. 13 Active flap control concepts | xx Control concepts Tilt-Yaw control similar to IPC 2 fully decoupled SISO loops 3 rd loop added for collective flap angle PID controllers on rotor yaw and tilt moments Gains tuned based on 3 linearized s-s models Linear models still show periodicity (LTP) ! centralized individual flap control van Engelen, van der Hooft 2005

14. 14 Active flap control concepts | xx Control concepts centralized individual flap control flaps activity

15. 15 Active flap control concepts | xx Control concepts 9 fully decoupled SISO loops PID controllers on local flapwise deflections Gains tuned based on 9 linearized s-s models Coupling between loops decentralized multiple flap control (feedback)

16. 16 Active flap control concepts | xx Control concepts decentralized multiple flap control (feedback) flaps activity

17. 17 Active flap control concepts | xx Control concepts 9 fully decoupled SISO loops Model-based controllers on local inflow (V, alpha) Coupling between loops decentralized multiple flap control (feed- forward on inflow)

18. 18 Active flap control concepts | xx Results decentralized individual flap control

19. 19 Active flap control concepts | xx Results centralized individual flap control

20. 20 Active flap control concepts | xx Results decentralized multiple flap control (feedback)

21. 21 Active flap control concepts | xx Results Concept comparison % reduction control scheme IFC IFC-Coleman MFC average wind speed8 mps11.4 mps18 mps8 mps11.4 mps18 mps8 mps11.4 mps18 mps flap root moment std 15.4110.2317.329.265.787.9219.3216.3522.41 flap tip deflection std 9.265.5410.218.012.611.9131.0120.5434.52 FA tower root moment std 4.313.675.013.478.991.4717.2515.5618.33 FA tower top deflection std 3.983.024.134.499.240.9715.9313.2116.02 Mean generator power -0.89-0.53-0.45-1.22-0.32-0.14-0.88-0.61-0.54 Pitch angle std -9.2710.03-10.5712.25-8.3210.16

22. 22 Active flap control concepts | xx Conclusions The newly developed model provides great flexibility for advanced distributed control design and evaluation Multiple flap control schemes provide more detailed load reduction than a single flap Not considerable energy losses – No particular effort in improvement Pitch activity can be reduced Inflow feed-forward concept should include aeroelastic response feedback loops Future MIMO feedback control (+ff) Look into actuator dynamics

23. 23 Active flap control concepts | xx Questions? Thank you for your attention