1. Dynamic Response and Control of the Hywind Demo Floating Wind Turbine
Classification: Internal

2. The Hywind Concept Main particulars for HYWIND Demo
Turbine power : MW
Turbine weight : tons
Draft hull : m
Nacelle height : m
Rotor diameter : m
Water depth : –700 m
Displacement : t
Mooring : lines
Diameter at water line: 6 m
Diam. submerged body: 8,3 m
Classification: Internal

3. Conventional Wind Turbine Control System
Steady state power coefficient surface and thrust force characteristics
Negative damping contribution from rotor thrust force above the rated wind speed
Classification: Internal

4. Conventional Wind Turbine Control System
Example of stable (solid line) and unstable (dashed line) behaviour of Hywind Demo with and without use of a stabilizing floater motion controller.
Hywind Demo was shut down after 250 seconds with use of the unstable conventional controller.
Classification: Internal

5. MEASUREMENTS: Sea airgap.
Sea current velocity and direction, and wave direction.
Heave and pitch motion.
Tower strains.
Wind speed measurement at the nacelle.
Nacelle yaw angle.
Power production.
Classification: Internal

6. Comparison Between Measurements and Simulations:
Small Wave Condition
Mean wind speed
13.6 m/s
Turbulence intensity
11.4 %
Significant wave height
2.1 m
Characteristic peak period
7.7 s
Tower Pitch Angle
Mean
[deg]
Std
Min
Max
Simulation
2.0
0.40
0.8
3.1
Measurement
0.31
1.1
3.7
Classification: Internal

7. Comparison Between Measurements and Simulations
Moderate Wave Condition
Mean wind speed
16.8 m/s
Turbulence intensity
10.2 %
Significant wave height
3.5 m
Characteristic peak period
9.8 s
Tower Pitch Angle
Mean
[deg]
Std
Min
Max
Simulation
1.6
0.47
0.0
3.1
Measurement
2.0
0.35
0.9
Classification: Internal

8. Measurements: Controller Comparison – Small Wave Condition
Wave and wind environment:
Wind Speed
Mean
[m/s]
Turb
[%]
Min
Max
Controller 1
13.6
9.3
8.0
18.9
Controller 2
13.7
8.4
8.6
17.2
Wave Elevation Hs
[m] Tp
[s]
Min
Max
Controller 1
2.2
7.5
-2.0
2.1
Controller 2
2.5
7.8
-2.3
Classification: Internal

9. Measurements: Controller Comparison – Small Wave Condition
Dynamic responses:
Tower Pitch Angle
Mean
[deg]
Std
[%]
Min
Max
Controller 1
-2.0
0.31
-3.7
-1.1
Controller 2
-2.2
0.47
-4.0
-0.7
Tower Strain
Std
[mum/m]
Min
Max
Controller 1
9.71
22.6
98.1
Controller 2
13.78
4.3
108.1
Classification: Internal

10. Measurements: Controller Comparison – Moderate Wave Condition
Wave and wind environment:
Wind Speed
Mean
[m/s]
Turb
[%]
Min
Max
Controller 1
16.8
9.6
11.5
22.0
Controller 2
17.2
8.7
23.1
Wave Elevation Hs
[m] Tp
[s]
Min
Max
Controller 1
3.8
9.5
-3.1
3.7
Controller 2
3.5
11.4
-2.7
3.0
Classification: Internal

11. Measurements: Controller Comparison – Moderate Wave Condition
Dynamic responses:
Tower Pitch Angle
Mean
[deg]
Std
Min
Max
Controller 1
-2.0
0.34
-3.1
-0.9
Controller 2
-2.1
0.42
-3.6
-0.8
Tower Strain
Std [mum/m]
Min
[mum/m]
Max
Controller 1
18.7
-16.1
120.2
Controller 2
18.5
-22.5
98.3
Classification: Internal

12. Conclusions
It is demonstrated that a stabilizing floater motion controller is required for a floating wind turbine.
Simulations and measurements are compared for wind speeds above rated wind speed. Good agreement is obtained in small as well as moderate sea states.
Two different stabilizing controllers are compared by full scale testing. A significant difference in the response at resonance is observed. This difference is important to the fatigue life of the tower.  
The range of variation of typical wind turbine parameters like rotor speed, blade pitch angle and active power production are similar to what is observed for fixed foundation wind turbines.
Classification: Internal

13. Thank you!
Dynamic Response and Control of the Hywind Demo Floating Wind Turbine
Bjørn Skaare
Principal Researcher New Energy
tel:
Classification: Internal