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Aeroelastic Stability and Control of Large Wind Turbines

Aeroelastic Stability and Control of Large Wind Turbines. STABCON. Part 1. Part 2. STABCON: Aero-Servo-Elasticity of wind turbines. PRVS and ASR turbines: NM80 prototype in Tjæreborg. Investigated topics for passive instability suppression. Effect of airfoil aerodynamics

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Aeroelastic Stability and Control of Large Wind Turbines

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  1. Aeroelastic Stability and Control of Large Wind Turbines STABCON

  2. Part 1 Part 2 STABCON: Aero-Servo-Elasticity of wind turbines

  3. PRVS and ASR turbines: NM80 prototype in Tjæreborg

  4. Investigated topics for passive instability suppression • Effect of airfoil aerodynamics • Smooth stall characteristics increases the damping • Effect of flapwise – edgewise frequency coincidence • Coincidence creates a flapwise – edgewise whirling coupling • Effect of flapwise – edgewise whirling coupling • Coupled whirling modes ”share” aeroelastic damping • Effect of torsional blade stiffness • Low torsional blade stiffness may lead to flutter • Can whirl flutter happen on a wind turbine? • Yes for extremely low tilt/yaw stiffness of nacelle support • Edgewise/torsion coupling for large flapwise deflections • Downwind flapwise bending may increase edgewise damping • Effect of yaw error on damping from wake • The destabilizing effect of dynamic inflow changes slightly by yaw errors • Effect of generator dynamics • Damping effects depend on generator type and control strategy

  5. Effect of edgewise/flapwise whirling coupling – PRVS

  6. Effect of edgewise/flapwise whirling coupling – ASR

  7. Effect of large flapwise deflection – PRVS downwind pre-bend upwind pre-bend

  8. Effect of large flapwise deflection – ASR downwind pre-bend upwind pre-bend

  9. Investigated topics for integrated aeroelastic control • Power/speed controller issues • Speed controller frequency placed away from aeroelatic frequencies • Active drivetrain damping by feedback to generator torque • Drivetrain loads reduced by up to 10 % • Active drivetrain damping reduces pitch activity • Active tower damping by feedback to collective pitch • Efficiency depend on the aeroelastic damping of the tower modes • Cyclic pitch for flapwise blade and tilt/yaw load reductions • Efficiency depend on the ratio of stochastic and deterministic loading • most relative efficiency for low turbulence • Too high feedback gains may lead to whirl-flutter-like instability • Are there conflicting objectives of combined controllers? • No, if there is a sufficient frequency separation of control actions

  10. Cyclic pitch actions reduce flapwise blade loads

  11. Cyclic pitch actions reduce tilt/yaw shaft and tower loads

  12. Cyclic pitch actions affect the damping of tower modes

  13. Active tower damping and cyclic pitch can be combined

  14. Guidelines available from www.risoe.dk R-1575 R-1577

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