11 june 2009 american control conferencest. louis, mo control of wind turbines: past, present and...
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11 June 2009American Control Conference St. Louis, MO
Control of Wind Turbines: Past, Present and Future
Alan WrightJason Laks, Lucy Pao
11 June 2009American Control Conference St. Louis, MO
OUTLINE
• HAWT TURBINE OVERVIEW• BASIC TURBINE CONTROL
– TORQUE AND PITCH CONTROL LOOPS– BASIC TURBINE MODEL– PITCH ORIENTATION– POWER COEFFICIENT– REGIONS OF OPERATION– BASIC TORQUE/ PITCH CONTROLLER SIMULATION
• DESIGN TOOLS• ADVANCED CONTROL
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TURBINE OVERVIEW
Upwind HAWT Horizontal Axis Turbine Types
Fixed Speed Variable Speed
FIXED PITCH Low Power
VARIABLE PITCH
Utility Scale Turbines
½ MW and Larger
CART3
[figure courtesy of US Dept. of Energy]
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BASIC TURBINE CONTROL
Wind
w
wd
Speed Sensor
Pitch Motor
Rotor Speed
Pitch Angle
b
Load Torque
tc
we
Torque Controller
Pitch Controller
tbKb
Ka
ta
caeroJ
1
Power Converter
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OPERATIONAL CONTROLLER
Wind
w
wd
Rotor Speed
Pitch Angle
b
Load Torque
tc
we
Torque Controller
Pitch Controller
tbKb
Kata
BASIC TURBINE CONTROL
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TowerNacelle
Blade
Pitch Angle
b
RotorWind Direction
Blade
Direction
BASIC TURBINE CONTROL
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b
Wind Velocity: w
Relative Velocity
BASIC TURBINE CONTROL
Wind Direction
Blade
Direction
Blade Velocity:
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b“Thrust”
Relative Velocity
Lift
(torque)
BASIC TURBINE CONTROL
Wind Direction
Blade
Direction
Tip Speed Ratio:
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Pitch [deg]
TP
S,
CART3 Cp Level Curves
-4 -2 0 2 4 6 8
1
2
3
4
5
6
7
8
9
10
0
0.05
0.1
0.15
0.2
0.25
0.3
• Available Wind Power
• Power Harvested
• Region 2:
BASIC TURBINE CONTROL
1 2 3 4 5 6 7 8 9 100
0.01
0.02
0.03
0.04
0.05
0.06
0.07
0.08
0.09
0.1Normalized Torque Versus Tip Speed Ratio
l
Norm
alized
Torq
ue
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• Region 2: torque control at optimal (tc=ta*)• Region 3: regulate speed/power• Region 4: shut down (“cut out”)
BASIC TURBINE CONTROL
w(Rated Power)
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BASIC TURBINE CONTROL
• Cut-Out: Once wind speed > 28m/sec– Pitch is ramped up to near perpendicular– Torque is held constant until generator speed is < 200 rpm and then regulated with a 2nd
PID (no brake!)
• Regions 1 & 2: Generator speed < 1800 rpm– Pitch Held constant at b*
– Torque adjusted according to sqare law once generator speed is > 200 rpm
w
• Region 3: Generator speed > 1800 rpm– Torque is held constant at rated (~3500 KN-m)– Pitch is adjusted based on speed error using a PID controller .
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• PID Pitch Loop Response
BASIC TURBINE CONTROL
(HSSV = gen. speed)
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BASIC TURBINE CONTROL
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Wind Modeling System Simulation
PITCHff
PITCHlimit
PITCHsim
HSSVEsim
LSSVsim
WINDsim
OutData
extract w
f(u)
Yaw Controller
Out1
TransportDelay
To Workspace
TIMEsim
GENTQsim
SelectShaftMeasures
measurementsHSSVE
LSSV
Scope 2
Scope 1
Scope
PitchControl
CTRLsim
PitchActuator
actmodPitchSet*pi/180
WindSet
Pitch Limits
FeedForward
FFsim
FAST Nonlinear Wind Turbine
Gen. Torque (Nm ) and Power (W)
Yaw Position (rad) and Rate (rad/s)
Blade Pitch Angles (rad)
OutData
q_out
qdot_out
Electrical Power
667e3
Clock
TorqueController
LSSV Tq
w
Tg
PITCH_op (rad)
FAST Structural and aeroelastic
simulation of two and three bladed wind turbines
Dynamically linked with simulink TURBSIM
Generation of model-based wind fields for input to simulation
Simulink MathWorks integration engine
FAST/SIMULINKSIMULATION
DESIGN TOOLS
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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 Rotation
Drive-train Torsion
ADVANCED TURBINE CONTROL
Tower Flexible Modes(Fore-Aft, Side-Side)
Blade Flexible Modes(Flap & Edge)
Drive Train TorsionalCompliance
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Numerically Linearized Model
ADVANCED TURBINE CONTROL
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ADVANCED TURBINE CONTROL
• ADD FEEDBACK FROM INDIVIDUAL BLADES
• INSTRUMENT TOWER TO DETECT SWAY
• USE MIMO DESIGN TECHNIQUES
– INDIVIDUAL BLADE PITCH– INCORPORATE WIND
DISTURBANCE MODELS
TORQUECONTROL
TORQUECONTROL
TORQUECONTROLMIMO
CONTROLTURBINE
IndividualPitch
TorqueCommand
BladeMeasurements
GeneratorSpeed
TowerMeasurements
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TURBINE
DIST
DELAY
S
• LIDAR BASED FEEDFORWARD
– MEASURE WIND UPSTREAM
FROM TURBINE
– REAL TIME WIND SPEED
– PRE-VIEW OF WIND SPEED
CHANGES
ADVANCED TURBINE CONTROL
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ADVANCED TURBINE CONTROL
30 40 50 60 70 80 90 10041
42
43
44
45
46Low Speed Shaft Response
Sp
eed
[rp
m]
PID
FB
FBFFprev
30 40 50 60 70 80 90 100-300
-200
-100
0
100
200
300
400Blade Flap Bending Moment Response
Rm
[kN
-m]
Time [sec]
38 39 40 41 42 43 44 4541.5
42
42.5
38 39 40 41 42 43 44 45-100
0
100
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SUMMARY
• Operational controllers can be constructed using basic parallel torque and collective pitch controllers.
• There are public domain tools and modelling codes available so that you can get started relatively quickly.
• MIMO Control approaches can improve load mitigation with additional instrumentation on the turbine.
• Advanced wind measurement technologies hold the promise of great improvements in performance.
11 June 2009American Control Conference St. Louis, MO
THANK YOU
Control of Wind Turbines: Past, Present and Future
Jason Laks, Lucy Pao Alan Wright