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

Alleviation of Extreme Blade Load by Individual Blade Control during Normal Wind Turbine Operation. W. E. Leithead P , HAN YI F. University of Strathclyde Glasgow, UK. 17/04/2012. EWEA 2012. Outline. Active blade load reduction Blade pitch control Controller design Performance

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

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  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. Outline • Active blade load reduction • Blade pitch control • Controller design • Performance • Conclusion 17/04/2012 EWEA 2012

  3. Active Blade Load Reduction 17/04/2012 EWEA 2012

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

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

  6. 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 1W0, 2W0 rad/s • Reduction on blades, rotor, hub, • yaw,… • Rain-flow counting, etc EWEA 2012

  7. 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 1W0 rad/s, edge • mode • Single event over lifetime • Reductions on the blade stations • Projection onto various • directions on (My,Mx) plane EWEA 2012

  8. Blade Pitch Control EWEA 2012

  9. 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 Pitch Control Individual Blade Control EWEA 2012

  10. M1 reference inputs b1 blade moments M2 b2 central controller turbine dynamics M3 b3 rotor speed wg Individual Pitch Control • Coleman (d-q axes) transformation applied • Controller tuning depends on full wind turbine dynamics EWEA 2012

  11. 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

  12. actuator+blade+ rest of turbine dynamics reference input - measured moment controller + fictitious force estimation actuator+blade dynamics Individual Blade Control

  13. Individual Blade Control • Key features: • Blade dynamics decoupled from restof turbine dynamics • Local controllers unaffected by the central controller • Central controller design and operation unaffected by blade controllers • Controller design and tuning straightforward • Smooth start-up and shut-down of blade control loop • Great flexibility of choice of blade load to be regulated

  14. Controller Design EWEA 2012

  15. 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 1Wo • 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

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

  17. Performance Assessment • 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 and 14 • Simulation based on an example 3MW WT Bladed model

  18. Performance EWEA 2012

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

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

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

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

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

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

  25. Mxy Control • Mx control in low wind speeds • Mxy control in high wind speeds 17/04/2012 EWEA 2012

  26. Conclusion 17/04/2012 EWEA 2012

  27. 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

  28. Any Questions? Thank You. EWEA 2012

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