Advanced Controls Research

1. Advanced Controls Research Alan D. Wright Lee Fingersh Maureen Hand Jason Jonkman Gunjit Bir 2006 Wind Program Peer Review May 10, 2006

2. Objectives • Create design methodology for advanced controls: • regulate rotor-speed and/or maximize energy extraction. • stabilize important flexible modes of the turbine to reduce dynamic loads and response. • Develop control design and modeling tools. • Develop controls field testing capability.

3. Nacelle Yaw Generator Torque Blade Pitch Control Actions Commercial Turbine Control

4. What else can we do? Improve energy capture Active rather than passive rotor control Negative inertia - Use of shaft torque to cancel rotor inertia Adaptive control Active pitch following Optimal torque control Reduce loads Load feedback Independent pitch control Periodic gains Active tower / blade / drive-train damping Advanced sensors Look-ahead controls

5. Adaptive control0.3% - 5% energy capture increase

6. Control of Flexible Modes

7. State Feedback Control • Regulate rotor-speed in the presence of wind-speed disturbances and stabilize turbine modes. • Stabilize flexible modes through full state feedback. • Use state estimation to provide the controller with needed states (including wind-speed). • Represent wind disturbance with extra states. Controller accounts for fluctuating wind speeds and shears. • Multiple input/multiple output, single control loop

8. State-Space Linear Model • Linear time-periodic model Turbine measurements Tower & blade strain gauges LSS torque Yaw, teeter, LSS angles Pitch angles where Structural DOFs & rates Up to 9 measurements Pitch actuator states Wind disturbance State matrices periodic over each rotation Up to 17 states

9. Process/Tools DesignSimulate Linear Model FAST DAC ADAMS LQR Simulink Field test CART CART-3 Industry Modify Analyze data Make changes Iterate

10. Field Tested Collective Pitch Controller15% - 50% reduction in Shaft Torque fatigue loads

11. CART Test Results – Pitch Control Region 2 Region 3 Normalized to Baseline Controller Performance • Significant reduction in most measured loads (30-70%)

12. z z V V h h hub hub Fluctuating wind component Uniform wind component Disturbance Model

13. Simulated Control With New Independent Pitch/DAC Must measure either tip-deflection or flap-bending moments on each blade

14. Use of Lidar Measured Wind-speed • Simulated single lidar hub-mounted on CART • Conical scan achieved through rotor rotation

15. Simulated Results

16. Measured Tower Load Reduction Using Generator Torque Control (CART) No control Control

17. Conclusions Must move away from using old control schemes with multiple loops Advanced Controls show great potential for meeting multiple control objectives Stabilizing turbine structure Enhancing energy capture Mitigating dynamic loads Will be critical for large flexible machines as well as offshore turbines with many flexible modes 17

18. Plans - Future Work • Complete development of control design tools for industry. • Continue advanced controls development and testing. • Develop new field testing capability on a large flexible turbine – partner with industry. • Implement and test controls on commercial turbines.

19. CART-3 – 3-bladed hub testing Supplement to the 2-bladed CART Advanced controls integration Designed for testing modern controls Loads Deflection Advanced sensors

20. Opportunities Partner with industry to implement controls on large turbines. Develop controls test-bed/floating platform simulator.

21. Questions and comments