PowerPoint Presentation

Alleviation of Extreme Blade Load by Individual Blade Control during Normal Wind Turbine OperationW. E. LeitheadP, HAN YIFUniversity of Strathclyde Glasgow, UK

17/04/2012EWEA 201217/04/2012EWEA 2012Active blade load reductionBlade pitch controlController designPerformanceConclusion

Outline17/04/2012EWEA 2012 Active Blade Load Reduction17/04/2012EWEA 2012 Spectra peaks in Mx,My Bending MomentActive Blade Load Reduction

17/04/2012EWEA 2012Load Reduction Fatigue Load Extreme LoadActive Blade Load Reduction

Control TaskPower RegulationSpeed Regulation17/04/2012EWEA 2012Load Reduction Fatigue Load Extreme Load Fatigue LoadActive Blade Load Reduction

Control TaskPower RegulationSpeed 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, etcLoad Reduction Fatigue Load Extreme Load17/04/2012EWEA 2012 Extreme LoadActive Blade Load Reduction

Control TaskPower RegulationSpeed Regulation Blade edgewise and flapwise BMs 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 17/04/2012EWEA 2012 Blade Pitch Control17/04/2012EWEA 2012Active blade load alleviation by pitch controlEach blade pitched individuallyOptionscyclic pitch controlindividual pitch controlindividual blade control

Blade Pitch ControlIndividual Pitch ControlIndividual Blade Control17/04/2012EWEA 2012centralcontrollerturbinedynamicsb1b2b3blade momentsM1M2M3wgrotor speedreference inputs Coleman (d-q axes) transformation applied Controller tuning depends on full wind turbine dynamicsIndividual Pitch Control17/04/2012EWEA 2012centralcontrollerturbinedynamicsb1b2b3M1M2M3wgrotor speedreference inputsactuator+ controlactuator+ controlactuator+ controlbd Each localised blade control systems operates in isolation Design of central controller and localised controllers are completely independentIndividual Blade Control

reference inputfictitious forceestimationcontrolleractuator+blade+rest of turbine dynamics-+measured momentactuator+blade dynamicsIndividual Blade ControlIndividual Blade ControlKey features: Blade dynamics decoupled from rest of turbine dynamics Local controllers unaffected by the central controllerCentral 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

17/04/2012EWEA 2012 Controller Design17/04/2012EWEA 2012 L1: Combination of Mx and MyDominant at low wind speeds near ratedKey component is blade edge mode L2: Combination of Mx and MyDominant at high wind speedsKey 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) planeExtreme Blade LoadsControl options Mx control Regulates blade edge spectral peak Acts on measured Mx My control Regulates 1Wo spectral peak Acts on measured My Mxy control Regulates blade edge spectral peak at low wind speed Regulates 1Wo spectral peak at high wind speed Acts on measuredController Design

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 modelPerformance Assessment17/04/2012EWEA 2012 Performance17/04/2012EWEA 2012 Pitch angles Power spectra densityMx Control

17/04/2012EWEA 2012 Power spectra densityMx Control

Pitch angles

17/04/2012EWEA 2012 Time trace Loads in (My,Mx) planeMx Control

17/04/2012EWEA 2012 Pitch angles Power spectra density

My Control

17/04/2012EWEA 2012 Time trace Loads in (My,Mx) planeMy Control

17/04/2012EWEA 2012Blade Mx controlBlade Section NO.L1L2L3L401-9.860.000.00-0.3206-11.160.000.00-0.3708-19.510.000.000.0010-28.700.000.000.0012-29.350.000.000.0014-19.000.000.000.0018-9.870.000.000.00Blade My controlBlade Section NO.L1L2L3L401-12.68-21.26-45.83+3.4806-1.71-17.29-41.30+3.7708-7.58-22.74-40.36+3.6710-7.72-26.73-39.15+5.9912-8.71-24.20-39.38+6.6214+5.78-21.98-35.73-0.4318+6.85-12.56-25.25+1.05Mx My Comparison17/04/2012EWEA 2012 Mx control in low wind speeds Mxy control in high wind speeds Blade Section NO.L1L2L3L401-10.18-22.69-18.23-1.1006-6.41-18.04-14.99-0.3208-23.02-22.79-13.34-0.2410-28.27-27.26-12.50+1.8312-29.05-27.93-14.81+0.4714-17.37-26.29-15.24-4.7718-12.99-10.84-10.73-0.93Mxy Control

17/04/2012EWEA 2012 Conclusion17/04/2012EWEA 2012 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 possibleConclusion17/04/2012EWEA 2012

Any Questions?Thank You.