Frequency-weighted MPC of Trailing Edge Flaps. Tests...

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Frequency-weighted MPC of Trailing Edge Flaps. Tests on a V27.

Damien Castaignet (Vestas Wind Systems A/S, Global Research)

Thomas Buhl (Risø DTU, National Laboratories for Sustainable Energy)

Niels K. Poulsen (Technical University of Denmark, DTU Informatics)

Jens Jakob Wedel-Heinen (Vestas Wind Systems A/S, Global Research)

[November 29th 2011, Wind Turbine Control Symposium, Ålborg]

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2011 Wind Turbine Control Symposium 2

Outline

• Trailing Edge Flaps

ￚ Background

ￚ Motivation

• Model Predictive Control

ￚ Design Model (Blade model)

ￚ Frequency weighted control

• Results

ￚ Simulations

ￚ Field tests

• Conclusions







Why use Trailing Edge Flaps?

Wind turbulence

Wind shear

Wake of another turbine

Tower shadow

Yaw misalignment

Wind slope

Loads in all parts of the

wind turbine







Why use Trailing Edge Flaps?

Today’s solution: Individual Pitch Control (IPC)

• Each blade can pitch individually

• Power control and load reduction

• But slow actuation due to the inertia of the blade (mass > 6 tons)

Trailing Edge Flaps (TEF)

• Controls the flow locally (more efficient)

• High actuation frequency

Up to 28% load reduction [1]

Up to 60% load reduction [2]

[1] Larsen, T. J., Madsen, H. A., and Thomsen, K., “Active load reduction using individual pitch, based on local blade flow measurements,” Wind Energy, Vol. 8, No. 1, 2005, pp. 67–80.

[2] Andersen, P. B., Gaunaa, M., Bak, C., and Buhl, T., “Deformable trailing edge flaps for modern megawatt wind turbine controllers using strain gauge sensors,” Wind Energy, Vol. 13, No. 2, 2010,

pp. 193–206.







Outline

•Trailing Edge Flaps

ￚ Background

ￚ Motivation




• Results

ￚ Simulations

ￚ Field tests

• Conclusions







System – V27

V27 Vestas turbine:

- located at Risø DTU

- 27 m diameter

- 225 kW nominal power

- 3 independent flaps on one blade

- extra sensors







A modal model is used: the blade is modelled by its first Nm mode shapes

Newton’s 2nd law is applied for each mode shape

Design Model – Blade Model

m

m

N

i

i

yiy

N

i

i

ziz

tutgtxu

tutgtxu

1

1

)()(),(

)()(),(

...),,,,,( VggFgKgCgM jjgigigig iiii








kmk

kk

kkkk

XCZ

CXY

GVBUAXX 1

flap moment

...),,,,( VggFgKgCgM jjgigigig iiii







MPC – a frequency problem

Time series and

PSD of the blade

root flap moment







MPC – Cost on the outputs

kk

kkkk

CXY

GVBUAXX 1

VUXY

V

V

V

CGGCA

CG

CGCAG

CG

U

U

U

CBBCA

CB

CBCAB

CB

X

CA

CA

CA

Y

Y

Y

d

N

N

N

NNN

0

1

1

0

1

1

1

0

1

0

2

2

1

0

0

00

0

0

00

)()(2

1RY'QRYΦ YY

System

Predicted outputs

Cost on the predicted outputs







Frequency weighted MPC – Cost on filtered outputs







ky

y

kyk

ky

y

ky

y

k

YDXCY

YBXAX

~1

VUXYYXY

Y

Y

Y

DBCBAC

D

DBC

D

X

AC

AC

C

Y

Y

Y

dy

y

y

Nyyyy

N

yy

y

yyy

y

y

N

yy

yy

y

N

00

2

1

2

0

1

2

1

and ~

0

0

00

~

~

~

cUgHUURY'QRYΦYY

''2

1)

~()

~(

2

1~~

Output filter

Predicted filtered outputs

Cost on the predicted filtered outputs

Frequency weighted MPC – Cost on filtered outputs







Frequency weighted MPC – Cost on zero-phase filtered outputs







MPC – Frequency weighted control – Cost on ZPF outputs

t=0

horizon measurements

time

cUgHUURY'QRYΦYY

''2

1...)

~()

~(

2

1~~







Outline

• Trailing Edge Flaps

ￚ Background

ￚ Motivation




• Results

ￚ Simulations

ￚ Field tests

• Conclusions







Simulation code – Flex5

Flex5, developed by DTU Mechanical

Engineering.

Blade Element Momentum (BEM) model

Blades and tower are flexible

Engineering models:

Tip correction

Dynamic wake

Dynamic stall model from Risø DTU [3]

Quadratic Program solver from the

university of Leuven, Belgium [4]

[3] P. B. Andersen, M. Gaunaa, C. Bak, and M. H. Hansen, “A dynamic stall model for airfoils with deformable trailing edges,” Wind Energy, vol. 12, no. 8, pp. 734–751, 2009.

[4] qpOASES homepage. [Online]. Available: http://www.kuleuven.be/optec/software/qpOASES






Simulations







Simulations – zero-phase filters







Field tests


• MPC with costs on zero-phase

filtered inputs and outputs

• Focus on the 1P and 2P loads

• No pitch position sensor

• Only one working trailing edge

flap

• 38 minute test including:

• 10 2-minute tests with active

trailing edge flaps

• 9 2-minute tests with fixed

trailing edge flaps






Field tests







Field tests


In average: 13.8% load reduction






Field tests – system identification


System identification from Thanasis Barlas, based on TU Delft work.







Conclusions

A model predictive control has been designed in order to alleviate blade root loads with

emphasize on given load frequencies.

Costs on zero-phase filtered inputs and output increase the performance of the MPC.

Field test showed load reduction: more tests needed to confirm the fatigue load reduction!

Acknowledgement: This work is part of the ATEF

project, which is partially funded by Danish

National Advanced Technology Foundation

(Højteknologifonden)

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Title slide images must always fit this size:

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Frequency-weighted MPC of Trailing Edge Flaps. Tests...

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