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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
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.