WIND TURBINE TOWER LOAD REDUCTION USING PASSIVE AND …sari-energy.org/oldsite/PageFiles/What_We_Do/... · WIND TURBINE TOWER LOAD REDUCTION USING PASSIVE AND SEMI-ACTIVE DAMPERS

WIND TURBINE TOWER LOAD REDUCTION USING PASSIVE AND SEMI-ACTIVE DAMPERS

Arturo Rodriguez Tsouroukdissian, PhD

ALSTOM Wind R&D Structural Department

Technical Leader Offshore Substructures

Technical Session: Innovative concepts and support structures for offshore

EWEA 2011Brussels, 16 March, 2011

WIND TURBINE TOWER LOAD REDUCTION USING PASSIVE AND SEMI-ACTIVE DAMPERS - 16/03/2011 - P 2

Agenda

• Brief Overview

• Damping devices

• Results

• Conclusions & Future Work

• Motivation


Agenda

• Brief Overview

• Damping devices

• Results


• Motivation


Modular

Pitch- VS

ALSTOM PURE TORQUE™

Yaw concept

• Over 1,600 wind turbines of different generations are in operation

• Concepts are coming from a track record in challenging sites

• A safe design is ensured by measurements and validated simulations

• Components fully tested

Proven and validated technology

Build on the experience of previous WT generations

Technology ECO 80 ECO 100


Product portfolio

ECO 100 platformECO 80 platform

Higher energy yield

Power: 3MW

Rotor Ø: 100, 110m

Status:

ECO100: series

ECO110: proto end ‘09

Higher reliability

Power: 1.67 & 2MW

Rotor Ø: 74, 80, 86m

Status:

ECO74/80: >1’200MW

ECO86: Proto 2010

Output MW

1

2

3

1.67

6.5 7.5 8.5

ECO 100 3MW

Site Average

Wind Speed m/s9.5 10.5

Class IClass IIClass III

ECO 74/80 1.67ECO 80/86 1.67

ECO 80 2MW

ECO 110 3MW


Differentiated and Competitive Products


A unique rotor support concept protecting the gearbox

from deflection loads

• The hub is resting on a large cast frame on two bearings, transferring all wind deflection loads

(red arrows) directly to the tower

• The shaft is connected to the front part of the hub and inserted inside the large casted frame,

transferring only the torque (green arrows) to the gearbox

ALSTOM PURE TORQUE™ concept

Transmitting pure torque to the gearbox for higher reliability



Agenda

• Brief Overview

• Damping devices

• Results


• Motivation

WIND TURBINE TOWER LOAD REDUCTION USING PASSIVE AND SEMI-ACTIVE DAMPERS - 16/03/2011 - P 8 P 8

Motivation for damping devices

• Next generation WT’s:

− Longer blades and taller tower

larger loads

need of integrated designs using structural control.

− Offshore WT’s

costly & difficult access in a rough environment.

• Structural damping lighter towers and substructures:− Decrease costs for material, manufacturing and transportation

− Fit to manufacturing, installation and transportation limits (weight and geometry)

− Increase Lifetime of whole turbine

Achieve significant decrease in cost

& reliable, competitive and economical efficient product


Integrated design of structures with embedded control systems

• State-of-the-practice:

− Tuned Mass Dampers (TMD’s):

− Multi Tuned Mass Dampers (MTMD’s):

− Active Mass Damper (AMD):

CHALLENGING !!!! huge mass, large space requirement, prohibitely costly, among many more.

Wide range of innovation available, so the end product is robust & reliable

Imaging changing some structural components!!!!


Agenda

• Brief Overview

• Damping devices

• Results


• Motivation


Technical description.Modal damping.

• The tower is a very stiff structure:

− Small drifts and interstory velocities.

− The system is non-classically damped modal properties require complex Eigenvalue analysis.

• Assumption #1: The mode shapes of the non-classically damped structure are identical to those of an undamped structure (ei. ξnc = ξud = 0.02).

− Non-classically damped structure is not a diagonal matrix due to the complex structure (soil-structure interaction + nacelle & rotor components).

• The frequency (ω), damping ratios (ξ) and mode shapes (Φ) depend on the [M], [K], and [C] matrices.

CT

References


Technical description.Magnification factor & effective damping.

•The amount of magnification of the damping force depends on the geometry.

•The device displacements are greater than the structural drift.

ufuD

DFfF

tutuCF oD sgn

The device displacement (uD) is proportional to a magnification factor (f) times the structural drift (u).

The force exerted by the damper (F) on the structure is proportional to the force along the axis of

the damper (FD) times a magnification factor (f).

Co is the damping coefficient and is the relative velocity between the ends

of the damper along its axis.

• Assumption #2: The joints can move up to +/-0.3º due to slippage distortion and inelastic action during testing.

• Assumption #3: the damper force is reduced by a relaxation time due to sliding at joints.

DFTheory


Damper Geometrical Configurations

Diagonal brace Chevron brace

Scissor jack Lower toggle

cosf

If θ = 37º, then f = 0.799 and

consequently ξD = 0.032 or 3.2%

damping

1ff = 1 and

consequently ξD = 0.05 or 5% damping

costan

f

If θ = 70º and ψ= 9º, then f = 2.16

and consequently

ξD = 0.23 or 23% damping

21

312

cossinsin

f

If θ1 = 32º, θ2 =

43º, and θ3 = 35ºthen f = 2.42 and

consequently ξD = 0.2935 or 29.35%

damping


Optimal Configuration: Upper-toggle bracing

•Highly efficient configuration that provides high damping.

31321

2 sincoscossin

fIf θ1 = 30º, θ2 = 50º, and θ3 = 40 then f = 2.792 and consequently ξD = 0.39 or 39% damping


Main characteristics

• The damper can be:

− Passive or active filled with a viscous fluid or − Controllable fluid damper filled with either magnetorheological fluid or electrorheological fluid.

• The damper may be:

− Dependent of the frequency (passive), current (semi-active), fluid pressure (active), and combined (hybrid).

• Advantages:

− They dissipate energy over a wide range of deformations and a broad range of frequencies.− They are velocity-dependent.− Easy manufacturability and assembly on-site.− Long-life or high-cycle resistance.

Polar arrangement to provide damping in all directions of the wind turbine due to: (i)

rotor movement, (ii) nacelle imbalances.


Geometrical integration (ECO100 t90m - hybrid)

Upper toggle bracing

Tower Base

Tower Top


Agenda

• Brief Overview

• Damping devices

• Results


• Motivation


Control Structure – Feedback Controller + ACTIVE, SEMIACTIVE & HYBRID TOWER DAMPING


Control scheme

• Semi-active, active, and hybrid control schemes.

• Acceleration and force feedback control.

− Robust.− Optimal.− Adaptive and/or predictive.

• Damper force depends on the tower frequency.

• Available sensors, DAC, and processors.

• Power supply from the wind turbine.

• Command signal depends on the device (ei. For MR damper = current).


Passive – Semi-active damping device


Tower Weight Reduction – Extreme Loads

Undamped and damped SF for ECO100 T90 steel Adjusted - 31.5t Steel -13.1%

0

0.5

1

1.5

2

2.5

3

3.5

4

0 20 40 60 80 100

Tower Height [m]

Safe

ty F

acto

r [-]

USF baseline

USF damped

0.0

0.5

1.0

1.5

2.0

2.5

3.0

3.5

4.0

4.5

0 20 40 60 80 100

Tower Height [m]

Safe

ty F

acto

r [-]

USF baseline

USF damped

Undamped and damped SF for ECO100 T90 hybrid Adjusted - 19.8t Hybrid -7.7%


Fatigue Calculation / DEL

Mxy

Tower Bottom

SN Slope Baseline Damped

Inverse abs. red.

3 22.8865 20.4642 -11%

5 23.4415 21.6052 -8%

9 27.558 25.5454 -7%

Hybrid 90m Tower Steel 90m Tower

All values:

- In MNm

- For 1E7 cycles

- 20 years lifetime

Mxy

Tower Bottom

SN Slope Baseline Damped

Inverse abs. red.

3 23.0334 19.9411 -13%

5 24.0013 21.6556 -10%

9 27.9451 25.6931 -8%

Increase Fatigue Safety Factors Tower:

- Hybrid 7.6% in average, 9% increase of the lowest

- Steel 11% in average, 12.5% increase of the lowest


Agenda

• Brief Overview

• Damping devices

• Results


• Motivation


Conclusions

• The impactsignificant tower load reduction, consequently the total tower cost may drop (… similar situation for an offshore support structure & tower).

• The advantages cutting edge technology applied to very high flexible towers and offshore substructures.

• The catch wind turbine towers and support structures account for a large stake in the total wind turbine cost


Future Work

Damper locationsTower base damper

location

Aerodynamic & Gravitational load

Hydrodynamic

load


Future Work

• Reduce elevated dynamic loads for water depths above 25m

• Increase fatigue life of transition piece connection

• Don’t discard Monopiles as a feasible and cheap substructure solution

− Cheap manufacturing− Cheap installation compared to its substructure counterparts

Consider as a feasible option the Monopile employing dampers

for water depths between 5m to 35m


Thank you for your attention!

www.power.alstom.com

Acknowledgements:T. Fischer, B. Kuhnle, M. Scheu (U. Stuttgart)C. Carcangiu, I. Pineda, M. Martin (Alstom Wind)


WT degrees-of-freedom

FLAP

WIS

E D

ISPL

ACEM

ENT

(OU

T-O

F-PL

ANE)

EDG

EWIS

E D

ISPL

ACEM

ENT

(IN

-PLA

NE)

Return


External loads

1. Steady:

1. Mass force: Gravity

2. Env. Influence: Thrust on the motor, sea current, temperature.

3. Operational status: Rotational speed

• Transient:

• Mass force: Breaking forces

• Env. Influence: Gusts.

• Operational status: Breaking, grid instabilities

• Periodic:

• Mass force: Mass imbalance

• Env. Influence: Tower shadow, wind shear, etc.

• Operational status: Aerodynamic imbalances

• Stochastic – Random:

1. Mass force: ---

2. Env. Influence: Turbulence of wind, sea condition, earthquake.

3. Operational status: ---

Return


Global Eigenmodes - Tower

1st Tower transverse mode

1st Tower longitudinal mode

2nd Tower transverse mode

2nd Tower longitudinal mode

Return


Global Eigenmodes - Rotor

1st rotor leadwise (on plane) modes

1st rotor flapwise (out of plane) modes

Return


Technical description.Effective damping.

iii

jjrjjk

D m

fCT

2

22

4

T = the period of vibration of the kth mode the structure (either FA or StS for a wind turbine);

Cj is the damping coefficient of the damper j;

fj= magnification factor of damper j;

Wi= is the reactive weight on top of the damping system or at level i;

Φrj= is the relative modal displacement of the damper j of the kth vibration mode;

Φi= is the modal displacement on top of the damping system or at level i.

• Using the Linear Static Procedure (LSP) a velocity-dependent device in a structure may be analyzed.

k

jj

SD W

W

4

i

iik FW 21

222

rjjj CT

W

Work done by the device j in one

complete cycle of loading, where Cj is

the damping coefficient of the damper j

and δrj level is the relative displacement between the ends of the device.

Maximum strain energy in the structure, where δi level displacements

and Fi is the inertia force at the ith level.


Elevator Design Restriction


Tower Maximal Force


References

• [1] Ashour SA, Hanson RD (1987). Elastic seismic response of buildings with supplemental damping. Report No. UMCE 87-01, Department of Civil Engineering, University of Michigan, Ann Arbor, MI.

• [2] Baz, A. “Active Damping”, Encyclopedia of Vibration, pp. 351-364. San Diego: Academic Press, 2001.

• [3] Constantinou, M. C., Tsopelas, P., Hammel, W., and Sigaher, A. N (2001). Toggle-brace-damper seismic energy dissipation systems. Journal of Structural Engineering. 127(2): 105–112.

• [4] Gluck N, Reinhorn AM, Gluck J, Levy R (1996). Design of supplemental dampers for control of structures. Journal of Structural Engineering. 122(12):1394 –1399.

• [5] Hwang J-S, Huang Y-N, and Hung Y-H (2005). Analytical and Experimental Study of Toggle-Brace-Damper Systems. Journal of Structural Engineering. 131 (7): 1035-1043.

• [6] Milman MH, Chu CC (1994). Optimization methods for passive damper placement and tuning. Journal of Guidance, Control and Dynamics. 17(4):848–856.

• [7] Natke HG, Soong TT (1993). Topological structural optimization under dynamic loads. In Optimization of Structural Systems and Applications, Hernandez S, Brebbia CA (eds). Computational Mechanics Publications: Southampton.

• [8] Shukla AK, Datta TK (1999). Optimal use of viscoelastic dampers in building frames for seismic response. Journal of Structural Engineering. 125(4):401– 409.

• [9] Singh MP, Moreschi LM (2001). Optimal seismic response control with dampers. Earthquake Engineering and Structural Dynamics. 30:553–572.

• [10] Takewaki I (1997). Optimal damper placement for minimum transfer functions. Earthquake Engineering and Structural Dynamics. 26:1113–1124.

• [11] Takewaki I, Yoshitomi S, Uetani K, Tsuji M (1999). Non-monotonic optimal damper placement via steepest direction search. Earthquake Engineering and Structural Dynamics. 28:655–670.

• [12] Ungar, E. E. (2001) “Damping Materials”, Encyclopedia of Vibration, San Diego: Academic Press. 327-331

• [13] U.S. Patent 4644714 and 2004/0098930 A1

• [14] U.S. Patent Nos. 5870863 and 5934028, 1996

• [15] Wu B, Ou JP, Soong TT (1997). Optimal placement of energy dissipation devices for three-dimensional structures. Engineering Structures. 19:113–125.

• [16] Zhang RH, Soong TT (1992). Seismic design of viscoelastic dampers for structural applications. Journal of Structural Engineering. 118(5):1375 –1392.

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WIND TURBINE TOWER LOAD REDUCTION USING PASSIVE AND …sari-energy.org/oldsite/PageFiles/What_We_Do/... · WIND TURBINE TOWER LOAD REDUCTION USING PASSIVE AND SEMI-ACTIVE DAMPERS