1. 11 June 2009 American Control ConferenceSt. Louis, MO Control of Wind Turbines: Past, Present and Future

2. 11 June 2009 American Control ConferenceSt. Louis, MO OUTLINE HAWT TURBINE OVERVIEW BASIC TURBINE CONTROL – TORQUE AND PITCH CONTROL LOOPS – BASIC TURBINE MODEL – PITCH ORIENTATION – POWER COEFFICIENT – REGIONS OF OPERATION – BASIC TORQUE/ PITCH CONTROLLER SIMULATION DESIGN TOOLS ADVANCED CONTROL

3. American Control Conference, 11 June 2009 Laks, Pao & Wright 3 TURBINE OVERVIEW Upwind HAWT Horizontal Axis Turbine Types Fixed SpeedVariable Speed FIXED PITCHLow Power VARIABLE PITCH Utility Scale Turbines ½ MW and Larger CART3 [figure courtesy of US Dept. of Energy]

4. American Control Conference, 11 June 2009 Laks, Pao & Wright 4 BASIC TURBINE CONTROL Wind w d Speed Sensor Pitch Motor Rotor Speed Pitch Angle Load Torque c e Torque Controller Pitch Controller K KaKa a Power Converter

5. American Control Conference, 11 June 2009 Laks, Pao & Wright 5 OPERATIONAL CONTROLLER Wind w d Rotor Speed Pitch Angle Load Torque c e Torque Controller Pitch Controller K KaKa a BASIC TURBINE CONTROL

6. American Control Conference, 11 June 2009 Laks, Pao & Wright 6 Tower Nacelle Blade Pitch Angle Rotor Wind Direction Blade Direction BASIC TURBINE CONTROL

7. American Control Conference, 11 June 2009 Laks, Pao & Wright 7 Wind Velocity: w Relative Velocity BASIC TURBINE CONTROL Wind Direction Blade Direction Blade Velocity:

8. American Control Conference, 11 June 2009 Laks, Pao & Wright 8 Thrust Relative Velocity Lift (torque) BASIC TURBINE CONTROL Wind Direction Blade Direction Tip Speed Ratio:

9. American Control Conference, 11 June 2009 Laks, Pao & Wright 9 Available Wind Power Power Harvested Region 2: BASIC TURBINE CONTROL 12345678910 0 0.01 0.02 0.03 0.04 0.05 0.06 0.07 0.08 0.09 0.1 Normalized Torque Versus Tip Speed Ratio Normalized Torque

10. American Control Conference, 11 June 2009 Laks, Pao & Wright 10 Region 2: torque control at optimal ( c = a* ) Region 3: regulate speed/power Region 4: shut down (cut out) BASIC TURBINE CONTROL (Rated Power)

11. American Control Conference, 11 June 2009 Laks, Pao & Wright 11 BASIC TURBINE CONTROL Cut-Out: Once wind speed > 28m/sec – Pitch is ramped up to near perpendicular – Torque is held constant until generator speed is < 200 rpm and then regulated with a 2 nd PID (no brake!) Regions 1 & 2: Generator speed < 1800 rpm – Pitch Held constant at * – Torque adjusted according to sqare law once generator speed is > 200 rpm w Region 3: Generator speed > 1800 rpm – Torque is held constant at rated (~3500 KN-m) – Pitch is adjusted based on speed error using a PID controller.

12. American Control Conference, 11 June 2009 Laks, Pao & Wright 12 PID Pitch Loop Response BASIC TURBINE CONTROL (HSSV = gen. speed)

13. American Control Conference, 11 June 2009 Laks, Pao & Wright 13 BASIC TURBINE CONTROL

14. American Control Conference, 11 June 2009 Laks, Pao & Wright 14 Wind Modeling System Simulation FAST Structural and aeroelastic simulation of two and three bladed wind turbines Dynamically linked with simulink TURBSIM Generation of model-based wind fields for input to simulation Simulink MathWorks integration engine DESIGN TOOLS

15. American Control Conference, 11 June 2009 Laks, Pao & Wright 15 ADVANCED TURBINE CONTROL Tower Flexible Modes (Fore-Aft, Side-Side) Blade Flexible Modes (Flap & Edge) Drive Train Torsional Compliance

16. American Control Conference, 11 June 2009 Laks, Pao & Wright 16 Numerically Linearized Model ADVANCED TURBINE CONTROL

17. American Control Conference, 11 June 2009 Laks, Pao & Wright 17 ADVANCED TURBINE CONTROL ADD FEEDBACK FROM INDIVIDUAL BLADES INSTRUMENT TOWER TO DETECT SWAY USE MIMO DESIGN TECHNIQUES – INDIVIDUAL BLADE PITCH – INCORPORATE WIND DISTURBANCE MODELS TORQUE CONTROL TORQUE CONTROL TORQUE CONTROL TORQUE CONTROL TORQUE CONTROL TORQUE CONTROL MIMO CONTROL MIMO CONTROL TURBINE Individual Pitch Torque Command Blade Measurements Generator Speed Tower Measurements

18. American Control Conference, 11 June 2009 Laks, Pao & Wright 18 TURBINE DIST DELAY LIDAR BASED FEEDFORWARD – MEASURE WIND UPSTREAM FROM TURBINE – REAL TIME WIND SPEED – PRE-VIEW OF WIND SPEED CHANGES ADVANCED TURBINE CONTROL

19. American Control Conference, 11 June 2009 Laks, Pao & Wright 19 ADVANCED TURBINE CONTROL 30405060708090100 41 42 43 44 45 46 Low Speed Shaft Response Speed [rpm] PID FB FBFFprev 30405060708090100 -300 -200 -100 0 100 200 300 400 Blade Flap Bending Moment Response Rm [kN-m] Time [sec] 3839404142434445 41.5 42 42.5 3839404142434445 -100 0 100

20. American Control Conference, 11 June 2009 Laks, Pao & Wright 20 SUMMARY Operational controllers can be constructed using basic parallel torque and collective pitch controllers. There are public domain tools and modelling codes available so that you can get started relatively quickly. MIMO Control approaches can improve load mitigation with additional instrumentation on the turbine. Advanced wind measurement technologies hold the promise of great improvements in performance.

21. 11 June 2009 American Control ConferenceSt. Louis, MO Control of Wind Turbines: Past, Present and Future