Advanced Controls ResearchAdvanced Controls ResearchAlan D. WrightAlan D. WrightLee FingershLee Fingersh

Maureen HandMaureen HandJason JonkmanJason Jonkman

Gunjit BirGunjit Bir

2006 Wind Program Peer Review2006 Wind Program Peer Review

May 10, 2006May 10, 2006

22006 Wind Program Peer Review

Create design methodology for advanced controls: – regulate rotor-speed and/or maximize energy

extraction.– stabilize important flexible modes of the turbine to

reduce dynamic loads and response.

Develop control design and modeling tools.

Develop controls field testing capability.

Objectives

32006 Wind Program Peer Review

Commercial Turbine Control

Generator Torque

Nacelle Yaw

Blade Pitch

Control Actions

Generator Speed

Generator Torque

Rotor Collective Pitch

Region 2

Region 3

Wind Disturbances

PID Pitch Controller

Drive-train Damper

T = kw^2

Nonlinear Turbine

42006 Wind Program Peer Review

What else can we do?

Improve energy capture– Active rather than

passive rotor control• Negative inertia - Use

of shaft torque to cancel rotor inertia

– Adaptive control– Active pitch following– Optimal torque

control

Reduce loads– Load feedback– Independent pitch

control– Periodic gains– Active tower / blade /

drive-train damping– Advanced sensors– Look-ahead controls

52006 Wind Program Peer Review

Adaptive control0.3% - 5% energy capture increase

0 50 100 150 200 250 300 3500.5

1.0

1.5

2.0

Nor

mal

ized

M (M

/M+ )

0 50 100 150 200 250 300 350

0.3

0.4

0.5

Frac

tiona

l Ave

rage

Pow

er

Time (hours)5 10 15 20

0

100

200

300

400

500

600

Grid

Pow

er (k

W)

Mean Equivalent Wind Speed (m/s)

Standard ControlAdaptive Control

Region 3Region 2

62006 Wind Program Peer Review

Control of Flexible Modes

Blade-2 Lag

Tower Side-Side

Rotor Rotation

(b) Frontview

Blade-1 Lag

Blade-1 Flap

Tower Fore-Aft

Rotor Teeter

(a) Sideview

Blade-2 Flap

Generator RotationDrive-train

Torsion

72006 Wind Program Peer Review

Regulate rotor-speed in the presence of wind-speed disturbances and stabilize turbine modes.– Stabilize flexible modes through full state feedback.

– Use state estimation to provide the controller with needed states (including wind-speed).

– Represent wind disturbance with extra states. Controller accounts for fluctuating wind speeds and shears.

Multiple input/multiple output, single control loop

State Feedback Control

82006 Wind Program Peer Review

State-Space Linear Model Linear time-periodic model

xtCy

utBxtAx

)(

)()(

w

qq

x

Structural DOFs & rates

Pitch actuator statesWind disturbance

com

gTu

Up to 17 states

y Turbine measurements

)( ),( ),( tCtBtA

State matrices periodic over each rotation

Up to 9 measurements

Tower & blade strain gaugesLSS torqueYaw, teeter, LSS anglesPitch angles

where

92006 Wind Program Peer Review

Process/Tools

Design SimulateLinear Model FAST

DAC ADAMSLQR Simulink

Field testCART

CART-3Industry

ModifyAnalyze dataMake changes

Iterate

OutData

Yaw Controller

Torque Controller

Pitch Controller

f(u)

Gen. Torque

Yaw Position

Blade Pitch

FAST Nonlinear Wind Turbine

102006 Wind Program Peer Review

Field Tested Collective Pitch Controller15% - 50% reduction in Shaft Torque fatigue loads

Measured Shaft Torque

60

80

100

120

140

160

180

200

0 5 10 15 20 25 30

Time (sec)

Low

-Spe

ed S

haft

Torq

ue

PI ControlState-space (FAST) controller

112006 Wind Program Peer Review

CART Test Results – Pitch Control

0.0

1.0

Meanshaft

pow er

Tow erfore-aftFDEL

Tow erside-side

FDEL

LSStorsionFDEL

Blade f lapFDEL

Coll. Pitch

Norm

alize

d to

Ba

selin

e Co

ntro

ller

Perfo

rman

ce

Significant reduction in most measured loads (30-70%)

Region 2 Region 3

0.0

1.0

RMSspeederror

Tow erfore-aftFDEL

Tow erside-side

FDEL

LSStorsionFDEL

Bladeflap FDEL

Coll. Pitch

Ind. Pitch

122006 Wind Program Peer Review

Disturbance Model

hz

hubV

hub( ) V (1 / )mV z z h

hotshmrV

hrmmVVrV hubhubhub

cos

4)1(),( 2

2

hz

hubV hub( ) V (1 / )mV z z h

hotshmrV

hrmmVVrV hubhubhub

cos

4)1(),( 2

2

Uniform wind component

Fluctuating wind component

132006 Wind Program Peer Review

Simulated Control With New Independent Pitch/DAC

0

0.1

0.2

0.3

0.4

0.5

0.6

0.7

43 44 45 46 47 48 49 50

Time (sec)

Bla

de 1

Fla

p D

efle

ctio

n (m

.)

Old DAC New DAC

Must measure either tip-deflection or flap-bending moments on each blade

142006 Wind Program Peer Review

Use of Lidar Measured Wind-speed

Simulated single lidar hub-mounted on CART

Conical scan achieved through rotor rotation

152006 Wind Program Peer Review

Simulated Results

 

Steady 18 m/s wind, power law exponent =

0.17

Steady 18 m/s wind, power law exponent =

0.3

  DAC DAC + LIDAR DAC DAC + LIDAR

Blade 1 RFB moment DEL (kNm) 53 51 83

64Turbulent 18 m/s wind,power law exponent =

0.17

Turbulent 18 m/s wind,power law exponent =

0.3

DAC DAC + LIDAR DAC DAC + LIDAR

Blade 1 RFB moment DEL (kNm) 295 263 310 278

162006 Wind Program Peer Review

No control Control

Measured Tower Load Reduction Using Generator Torque Control (CART)

172006 Wind Program Peer Review

Conclusions

17

Must move away from using old control schemes with multiple loops

Advanced Controls show great potential for meeting multiple control objectives– Stabilizing turbine structure– Enhancing energy capture– Mitigating dynamic loads

Will be critical for large flexible machines as well as offshore turbines with many flexible modes

182006 Wind Program Peer Review

Plans - Future Work Complete development of control design tools

for industry.

Continue advanced controls development and testing.

Develop new field testing capability on a large flexible turbine – partner with industry.

Implement and test controls on commercial turbines.

192006 Wind Program Peer Review

CART-3 – 3-bladed hub testing

Supplement to the 2-bladed CART

Advanced controls integration

Designed for testing modern controls– Loads– Deflection– Advanced sensors

202006 Wind Program Peer Review

Opportunities

Partner with industry to implement controls on large turbines.

Develop controls test-bed/floating platform simulator.

212006 Wind Program Peer Review

Questions and comments