Dynamic Response and Control of the Hywind Demo Floating Wind Turbine Classification: Internal 2011-03-14

The Hywind Concept Main particulars for HYWIND Demo Turbine power : 2.3 MW Turbine weight : 138 tons Draft hull : 100 m Nacelle height : 65 m Rotor diameter : 82.4 m Water depth : 150–700 m Displacement : 5300 t Mooring : 3 lines Diameter at water line: 6 m Diam. submerged body: 8,3 m Classification: Internal 2011-03-14

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 2011-03-14

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 2011-03-14

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 2011-03-14

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 2011-03-14

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 2011-03-14

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 2011-03-14

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 2011-03-14

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 2011-03-14

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 2011-03-14

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 2011-03-14

Thank you! Dynamic Response and Control of the Hywind Demo Floating Wind Turbine Bjørn Skaare Principal Researcher New Energy E-mail: bjoska@statoil.com, tel: +47 900 88 792 www.statoil.com Classification: Internal 2011-03-14