Alleviation of Extreme Blade Load by Individual Blade Control during Normal Wind Turbine Operation

1. Alleviation of Extreme Blade Load by Individual Blade Control during Normal Wind Turbine Operation W. E. LeitheadP, HAN YIF University of Strathclyde Glasgow, UK 17/04/2012 EWEA 2012

2. Active Blade Load Reduction • Spectra peaks inMx,My Bending Moment EWEA 2012

3. Active Blade Load Reduction • Load Reduction • Fatigue Load • Extreme Load Control Task Power Regulation Speed Regulation EWEA 2012

4. Active Blade Load Reduction • Load Reduction • Fatigue Load • Extreme Load Control Task Power Regulation • Fatigue Load Speed Regulation • Blade root out-of-plane bending • moment • Aggregation of loads over lifetime • Spectra peaks at 1P, 2Prad/s • Reduction on blades, rotor, hub, • yaw,… • Rain-flow counting, etc EWEA 2012

5. Active Blade Load Reduction • Load Reduction • Fatigue Load • Extreme Load Control Task Power Regulation • Extreme Load Speed Regulation • Blade edgewise and flapwiseBMs • Spectral peaks at 1Prad/s, edge • mode • Single event over lifetime • Reductions on the blade stations • Partial projection onto various • directions on (My,Mx) plane EWEA 2012

6. Blade Pitch Control • Active blade load alleviation by pitch control • Each blade pitched individually • Options • cyclic pitch control • individual pitch control • individual blade control Individual Blade Control EWEA 2012

7. M1 b1 reference inputs rotor speed M2 bd turbine dynamics b2 actuator+ control actuator+ control actuator+ control wg M3 central controller b3 Individual Blade Control • Each localised blade control systems operates in isolation • Design of central controller and localised controllers are • completely independent EWEA 2012

8. Extreme Blade Loads • L1: Combination of Mxand My • Dominant at low wind speeds near rated • Key component is blade edge mode • L2: Combination of Mx and My • Dominant at high wind speeds • Key component is 1P • L3: Projection of (My,Mx) onto negative My • direction in (My,Mx) plane • L4: Projection of (My,Mx)onto positive Mx • direction in (My,Mx) plane 17/04/2012 EWEA 2012

9. Controller Design Control options • Mx control • Regulates blade edge spectral peak • Acts on measured Mx • My control • Regulates 1Pspectral peak • Acts on measured My • Mxy control • Regulates blade edge spectral peak at low wind speed • Regulates 1Pspectral peak at high wind speed • Acts on measured

10. Performance Assessment • Simulation based on an example 3MW WT Bladed model • Full operational envelope including extreme wind conditions, IEC 61400-1 • Extreme loads determined as the worst case from nine separate evaluation • Important blade sections: 06,08,10,12,14 and 18

11. Mx Control • Pitch angles • Power spectra density 17/04/2012 EWEA 2012

12. Mx Control • Pitch angles • Power spectra density 17/04/2012 EWEA 2012

13. Mx Control • Time trace • Loads in (My,Mx) plane 17/04/2012 EWEA 2012

14. My Control • Power spectra density • Pitch angles 17/04/2012 EWEA 2012

15. My Control • Time trace • Loads in (My,Mx) plane 17/04/2012 EWEA 2012

16. Mx My Comparison Blade Mx control Blade My control 17/04/2012 EWEA 2012

17. Mx My Comparison Blade Mx control Blade My control 17/04/2012 EWEA 2012

18. Mx My Comparison Blade Mx control Blade My control 17/04/2012 EWEA 2012

19. Mxy Control 17/04/2012 EWEA 2012

20. Conclusion • Active control of blade loads considered • IBC applied to alleviate extreme blade loads • Flexibility of IBC over choice of measured bending • moment exploited • A reduction of 20% to 30% in the most important • extreme loads is achieved for an example 3MW WT • Further refinement possible EWEA 2012

21. Any Questions? Thank You. EWEA 2012