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Main Wind Systems
Module 4: Wind Turbines and Systems
On‐Shore
Mohamed A. El‐Sharkawi
Department of Electrical Engineering
University of Washington
University of Washington
Seattle, WA 98195
http://SmartEnergyLab.com
Email: [email protected]
Off‐Shore
ff h
4.1
© Mohamed A. El-Sharkawi, University of Washington
Key Parts of Wind Turbine
Gear box
Power Flow
Blade Power
Pblade
High speed shaft
Rotating blades
Mechanical Power
Wind Power
Pm
Pwind
gear
Housing
Low speed shaft
4.2
© Mohamed A. El-Sharkawi, University of Washington
Generator and converter
Yaw
Gear Power
Pgear
G
Electric Power
Pe
Tower
© Mohamed A. El-Sharkawi, University of Washington
4.3
© Mohamed A. El-Sharkawi, University of Washington
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Power Flow
Wind Power
Captured
Captured power from Wind
Pwind
Pblade
Input to Input
to
gearbox
Pgear
Example
Tehachapi is a desert city in California with an elevation of about 350 m, and is known for its extensive wind farms. Input to Input
to Output power
Output power
generator
P
Losses in Losses in rotating gearbox
blades and rotor mechanism
Coefficient of Performance
e
Pm
1. Compute the power density of the wind when the air temperature is 30oC and the speed of the wind is 5 m/s 2. A wind turbine at the site has three rotating blades; each is 60 m in length Compute the power captured by
each is 60 m in length. Compute the power captured by the blades assuming the coefficient of performance is 30%
Losses in generator
© Mohamed A. El-Sharkawi, University of Washington
4.5
© Mohamed A. El-Sharkawi, University of Washington
Solution of part 1
4.6
Example
 350
353
 
e 29.3( 30 273) 1.12 kg/m
g 3
30  273

Compute the total efficiency if the Coefficient of performance is 30%, the efficiency of the rotating f
i 30% th ffi i
f th
t ti
blade and rotor mechanism is 90%, the efficiency of the gearbox is 95% and the efficiency of the generator is 70%
1
1
 w3  1.12 * 53  70.0 W/m
2
2
Pwind  A    r 2    * 60 2 * 70  792 kW
Solution
  C p blade  gear  generator  0.3 * 0.9 * 0.95 * 0.7 18 %
Pblade  Pwind * C p  792 * 0.3  237.6 kW
© Mohamed A. El-Sharkawi, University of Washington
4.7
© Mohamed A. El-Sharkawi, University of Washington
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1.5 MW Turbine
4.9
© Mohamed A. El-Sharkawi, University of Washington
Rapid Growth of Wind Turbine Size
Basic Wind Turbine Specifications (2MW)
Rotor Diameter = 80 meters
Swept Area = 5,026 m2
Blade Rotation 15 5 16 5 rpm
Blade Rotation = 15.5‐16.5 rpm
Generator Voltage = 690 Volts
Capacity = 1,800‐2,000 kW
Nacelle (housing) Weight = 77 tons
Rotor Weight = 41 tons
Tower Weight = 105 tons
Tower Weight = 105 tons
Total Weight = 223 tons
2500
2000
2000
1500
kW
1500
1000
750
500
500
300
0
50
1980
4.10
© Mohamed A. El-Sharkawi, University of Washington
100
1984
1992
© Mohamed A. El-Sharkawi, University of Washington
1995
1998
2004
2006
4.11
© Mohamed A. El-Sharkawi, University of Washington
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GE 3.6MW
© Mohamed A. El-Sharkawi, University of Washington
Typical Blade length
4.13
Blade length (m)
27
27‐33
33‐40
Power Rating (kW)
225
300
500
40‐44
44‐48
48‐54
54‐64
64‐72
72‐80
600
750
1000
1500
2000
2500
© Mohamed A. El-Sharkawi, University of Washington
Can We Exceed 100m?
4.14
VESTAS 1.8MW
• Wind speed increases with height above ground
• 100m diameter can produce 3‐5MW
• Can we go higher than 100m?
– Introduces transportation constraints in most highways
• Max trailer dimension is 4.1m (H) X 2.6m (W)
– Requires large cranes that are not readily available
– Produces a new set of technical and environmental problems (impact on grid, wake, etc.)
© Mohamed A. El-Sharkawi, University of Washington
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© Mohamed A. El-Sharkawi, University of Washington
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Off‐Shore Wind System
© Mohamed A. El-Sharkawi, University of Washington
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© Mohamed A. El-Sharkawi, University of Washington
4.18
Two Blades Turbines
Runs at fast speed to improve Cp
Advantages:
g
• Gearbox ratio is reduced
• Blades easier to assembled on ground
Disadvantages:
• For the same wind speed, the two‐blade system captures less power then the three‐blade system
• Creates gyroscopic imbalances (bending moment due to tower wind shade)
• Higher speed means more noise
• Higher rate of bird collisions
© Mohamed A. El-Sharkawi, University of Washington
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© Mohamed A. El-Sharkawi, University of Washington
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Bending Moments (2‐blade)
Bending Moments (3‐blade)
• When one blade is at the top, it is Wind Force
receiving the maximum force of the wind
• The bottom blade is in the shadow of the tower; thus receiving less Wind Force
force
• The forces are not balanced at hub
– Torque on the hub is pulsating, thus stressing the hub gears © Mohamed A. El-Sharkawi, University of Washington
• The bottom blade in the shadow of the tower receives less than the maximum force
• The other two blades are not in the vertical position, so they also receive less than
they also receive less than the maximum force
• The forces are almost balanced at the hub 4.21
Why not 5 or 7 Blades?
Three‐Blade Turbine
• More expensive
• Increase wind wall effect
Increase wind wall effect
Advantages:
– Slow rotation
– three blades capture more energy than two blades for the same wind speed
– Gyroscopic forces are better balanced
– More aesthetic, less noise, fewer bird collisions
– Reduction of wind speed in front of the blades, thus reducing the amount of energy that can be captured by the blade
Disadvantages:
– Slower rotation increases gearbox costs
– Rotor cannot fully assembled on the ground
© Mohamed A. El-Sharkawi, University of Washington
4.22
© Mohamed A. El-Sharkawi, University of Washington
4.23
© Mohamed A. El-Sharkawi, University of Washington
Wind Force
Wind Force
4.24
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• Most turbines operate at wind speed of 12 – 30 mph
• Pitch Control – To maximize Cp
– Reduce Cp when wind speed produces power higher than the rating of the turbine
– Regulate the output power of the turbine as part of grid control action
• Yaw Control
– To align the rotor to face the wind
• Feathering
– To lock the blades at high wind speeds (>50mph)
4.25
© Mohamed A. El-Sharkawi, University of Washington
Typical Power‐Speed Characteristics
Power
Pitch, Yaw and Feather Control
Wind power
Output Power
Rated
Power
Ramp down
Ramp up
Rated speed
Cut‐in speed
Wind Speed
4.26
© Mohamed A. El-Sharkawi, University of Washington
Wind Turbine Performance
Typical On‐Shore System
Vestas V80 Power Curve
Grid Connection
Point
2000
1800
1600
HV‐GSU
Point
Farm Collection
Point
Trunk Line
1400
Power kW
Cut‐out speed
WPS
1200
1000
800
600
Grid
400
200
GSU
xfm
f
Wind Power
System
0
0
10
20
30
40
50
60
Windspeed MPH
© Mohamed A. El-Sharkawi, University of Washington
HV‐GSU: High Voltage side of Generation Step‐Up transformer
4.27
© Mohamed A. El-Sharkawi, University of Washington
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Typical Off‐Shore System
Grid Connection
Point
HV‐GSU
Point
Farm Collection
Point
Trunk Cable
Marine Cable
WPS
GSU
xfm
f
Grid
Off‐Shore
Wind Power
System
© Mohamed A. El-Sharkawi, University of Washington
4.29
© Mohamed A. El-Sharkawi, University of Washington
Offshore Wind Energy
Offshore Wind Energy
•
•
•
•
•
• A good match between generation and d
demand
d
– 28 states in the USA have costal lines
– These states consumes 78% of the national electric energy
• 900 MW offshore capacity installed in Europe
p y
p
• 10 offshore system, 2.4GW capacity are considered in the USA
© Mohamed A. El-Sharkawi, University of Washington
4.30
4.31
Normally between 2‐5MW
80‐126m in blade length
Transportation restriction is less than on‐shore systems
Mostly in relatively shallow water (up to 30m)
Marine cables are used to connect the systems to the shore stations
– Cable capacitance is much higher than that for overhead lines
– This may result in leading
Thi
lt i l di power factor at the shore f t
t th h
station
– Inductive compensation may be needed to prevent the overvoltage at the shore station
© Mohamed A. El-Sharkawi, University of Washington
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Challenges to Offshore Systems
• Prediction of the dynamic forces and motions acting on off shore turbines are needed
acting on off‐shore turbines are needed
• Offshore winds are much more difficult to characterize than winds over land
• Marine life
• High cost of installation
– Transportation, construction, foundations, anchors, and moorings
• High cost of maintenance
• Technology is limited for deep waters
• Wind specific safety standards
Wind specific safety standards
– Foundations can act as artificial reefs
– fish population increases
– bird population increases
– bird collisions increases – offshore oil and gas standards
© Mohamed A. El-Sharkawi, University of Washington
Challenges to Off‐Shore Wind
4.33
© Mohamed A. El-Sharkawi, University of Washington
4.34
4.35
© Mohamed A. El-Sharkawi, University of Washington
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Challenges to Off‐Shore Wind
• Interference with – commercial shipping and fishing
– recreational boating. • Could affect maritime radar systems • Visual impacts for systems close to shores • Impacts of low frequency motion noise on I
t fl f
ti
i
mammals
© Mohamed A. El-Sharkawi, University of Washington
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Factors Affecting Wind Generation
Floating Technology
• Wind speed and length of wind season
– Most wind turbines operate at 4 ‐16 m/s
• Diameter of rotating blades
– The power captured is proportional to the square of the radius
• a 10% increase in the blade length will result in 21% increase in the captured power
• Efficiency of wind turbine components
© Mohamed A. El-Sharkawi, University of Washington
4.37
Factors Affecting Wind Generation
4.38
Factors Affecting Wind Generation
• Arrangement of the turbines (array effect)
• Pitch control
– With pitch control, the TSR
p
,
can be adjusted to j
produce power at a wide range of wind speeds. • Yaw Control – Most wind turbines are equipped with yaw mechanism to keep the blades facing into the wind as the wind direction changes
g
– Some turbines are designed to operate on downwind; these turbines don't need yaw mechanisms as the wind aligns these turbines. © Mohamed A. El-Sharkawi, University of Washington
© Mohamed A. El-Sharkawi, University of Washington
4.39
– the blades of the front turbines create wakes of turbulent wind that can reach the rare turbines
– efficiency is reduced when wind is turbulent. • Reliability and maintenance
– The cost of electricity generated by the wind farm is a function of • Capital cost, land use, maintenance, and contractual arrangement. – The early designs of wind turbines were high maintenance machines as well as cost ineffective systems. – Newer designs have reliability rate around 98 percent
© Mohamed A. El-Sharkawi, University of Washington
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Wind Turbine Technolgies
• Generator
Types of Wind Turbine Systems
– Asynchronous Generator (Induction Machine)
• Squirrel Cage Induction Generator (SCIG)
q
g
(
)
• Wound Rotor Induction generator (WRIG)
– Synchronous Generator (SG)
• Controls
–
–
–
–
–
–
–
–
© Mohamed A. El-Sharkawi, University of Washington
4.41
Types of WTG
4.42
© Mohamed A. El-Sharkawi, University of Washington
Type1: SCIG with Fixed Compensation
• Type 1: Squirrel cage induction generator directly coupled to the grid. May have pitch control
to the grid May have pitch control
• Type 2: Wound rotor induction machine with external rotor resistance control
• Type 3: Wound rotor Doubly‐fed induction generator (Voltage injected in the rotor winding)
• Type 4: Synchronous or induction generator, the stator is connected to the grid via power converter.
© Mohamed A. El-Sharkawi, University of Washington
No Control
Fixed VAR compensation
Internal voltage and var control
External flicker and reactive power controls
External flicker and reactive power controls
Pitch control
AGC participation
Stability and ride through fault control
… … …
4.43
Grid Connection
Point
HV‐GSU
Point
Trunk Line
Grid
Farm Collection
Point
SCIG
Gear Box
GSU
xfm
f
Fixed
Compensation
HV‐GSU: High Voltage side of Generation Step‐Up transformer
© Mohamed A. El-Sharkawi, University of Washington
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Type1: SCIG with Variable Compensation
Grid Connection
Point
HV‐GSU
Point
Farm Collection
Point
Farm Collection
P i t
Point
WRIG
SCIG
Trunk Line
Gear Box
Gear Box
GSU
xfm
f
Grid
Type 2: Wound Rotor IG
Variable
Compensation
HV‐GSU: High Voltage side of Generation Step‐Up transformer
4.45
© Mohamed A. El-Sharkawi, University of Washington
Type 3: Doubly Fed Induction Generator (DFIG)
Farm Collection
P i t
Point
4.46
© Mohamed A. El-Sharkawi, University of Washington
Type 3: DFIG with AGC
WRIG
Gear Box
WRIG
Farm Collection
Point
Gear Box
AC/DC + DC/AC
Pitch angle
Grid
Conditions
AC/DC + DC/AC
Commands
© Mohamed A. El-Sharkawi, University of Washington
4.47
Injected voltage
AGC
© Mohamed A. El-Sharkawi, University of Washington
Wind Conditions
4.48
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Performance Comparison
Type 4: SG with AGC
Type1 & 2
Type 3
Type 4
Voltage Control
Poor
Better
Best
Flicker Control
Poor
Better
Best
Low Voltage Ride-Through
Poor
Better
Best
Stability Control
Poor
Better
Best
AGC Control
Poor
Better
Best
AC/DC + DC/AC
Farm Collection
Point
Excitation
Pitch angle
Excitation control
Grid
Conditions
Commands
AGC
© Mohamed A. El-Sharkawi, University of Washington
Wind Conditions
4.49
© Mohamed A. El-Sharkawi, University of Washington
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