Answer each questionin a paragraph in 12hr
Kfupm1413
EE 499-002 WIND POWER #2 WECS FUNDAMENTALS
Dr. Venkata Yaramasu Assistant Professor of Electrical Engineering Director of Advanced Motors, Power Electronics, and Renewable Energy (AMPERE) Laboratory School of Informatics, Computing, and Cyber Systems (SICCS) Northern Arizona University Phone: +1-928-523-6092 E-Mail: [email protected]
Office Hours: MoWeFr 12.30-1.30 p.m. in #69-210 By appointment in #90-112
Lecture: MoWe 11.30 a.m. to 12.20 p.m. in #69-224 Lab: Friday 11.30 a.m. to 2.00 p.m. in #69-234
Slides Credit: Dr. Bin Wu, Ryerson University, Canada.
Spring 2017 Ultrasonic Anemometer (Clipperwind)
Topics
2
1. Wind Turbine Components
2. Wind Turbine Aerodynamics
3. Modeling of Turbines
4. Maximum Power Point Tracking (MPPT)
1. Wind Turbine Components Fixed Speed Turbine Components
3
Photo courtesy: Bosch Rexroth AG
1. Wind Turbine Components Variable Speed Turbine Components
4
Mechanical Components (Tower, Blades, Nacelle, Rotor Hub, Gearbox,
Pitch Drives, Yaw Drives, Brakes)
Electrical Components (Generator, Converter, Transformer, Cables)
Control Systems
Photo courtesy: Bosch Rexroth AG
1. Wind Turbine Components WT Components in Motion
5
https://www.youtube.com/watch?v=W7ZHB9VS2b8
1. Wind Turbine Components Turbine Blades
6
pwM CvAP 3
2 1
Mechanical power captured by the blade:
ρ ‐ air density [kg/m3] A ‐ swept area [m2] vw ‐ wind speed [m/sec] Cp ‐ power coefficient of the blade
Direction of rotation
[W]
1. Wind Turbine Components Turbine Blades
7
Mechanical power PT extracted from the wind kinetic power Pw is:
pwpwM CvACPP 3
2 1 W
Cp = power coefficient of blades. Maximum value is __________.
Practical values are between ________ and _________.
ρ = air density (kg/m3). Air density is a function of altitude,
temperature, and humidity. At sea level and at 15◦C,
air has a typical density of 1.225 kg/m3.
A = rotor swept area (m2) =
rT = blade radius (m)
vw = wind-speed velocity (m/s).
1. Wind Turbine Components Turbine Blades
8
Question: How to capture more power from the wind?
Answer:
1. 2.
3. 4.
Example: ρ = 1.225 kg/m3, rT = 43.36 m, vw = 12 m/s, and Cp = 0.48.
Calculate PT.
Solution: pwT CvAP 3
2 1 W
Question: Can a 3MW WT be used to generate 4MW power
during high wind speed?
Answer:
1. Wind Turbine Components Turbine Blades
9
Question: What are the typical values for cut-in, rated and cut-out speeds?
Answer:
Question: Why PT curve is flat from rated to cut-out wind speed?
Answer:
1. Wind Turbine Components Pitch Drives
10
Photo courtesy: Bosch Rexroth AG
Pitch drives
Question: What is the purpose of pitch control ?
Answer:
Question: What are other power regulation methods ?
Answer:
1. Wind Turbine Components Pitch Drives
11
https://www.youtube.com/watch?v=TMbt3ca0XXg
1. Wind Turbine Components Yaw Drive
12
Yaw gear and bearing
Yaw motor drives
Tower conector ring
Yaw motor drives
Nacelle frame
Planetary gear
Yaw brakes Photo courtesy: Nordex
Purpose of yaw drive:
To turn the turbine rotor (blades) into the wind
1. Wind Turbine Components Gearbox
13
Photo courtesy: GE
Drivetrain Technologies
Purpose:
To adapt the low speed of the WT rotor to the high speed of the generator.
1. Wind Turbine Components Mechanical Brakes
14
Photo courtesy: HANNING & KAHL
Question: Why the mechanical brake is mounted on the high-speed shaft ?
Answer:
1. Wind Turbine Components Wind Sensor (Anemometer)
15
Question: What are different types of anemometers ?
Answer:
Photo courtesy: Clipperwind
1. Wind Turbine Components Wind Generators
16
Question: What is the oldest type of wind generator ?
Answer:
1. Wind Turbine Components Wind Generators
17
SCIG Photo courtesy: ABB Photo courtesy: ABB
Photo courtesy: Wikov
Photo courtesy: ABB
DFIG PMSG Low Pole
WRSG
Photo courtesy: Enercon
WRSG High Pole
Photo courtesy: Windtec-AMSC
HTS-SG
1. Wind Turbine Components Wind Generators
18
1. Wind Turbine Components Other
19
Other major components in WT are:
Power converter (low voltage and medium voltage)
Power transformer
Power cables
Mechanical control systems
Electrical control systems (digital control systems)
Question: Calculate line current of 5 MW WT with 690 V and 3000 V?
Answer:
2. Wind Turbine Aerodynamics Power Characteristics
20
vw (m/s)
Rated power
PM
Cut-in Rated Cut-out
Theoretical power curve
Min. power
Parking mode
Parking mode
Operating region
Practical power curve
Stall or pitch control
Generator control
Q: What are the typical values for cut‐in, rated and cut‐out speeds? A:
2. Wind Turbine Aerodynamics Passive Stall Control
21
Simplest method among the group: no need for motor drives and electronic control
The rotor blades are firmly fixed (bolted) to the rotor hub at a fixed angle
At higher wind speeds, the turbulence created on rotor surface causes airfoils to
lose lift force, thereby output power decreases
As wind speed increases above the rated value, output power decreases gradually,
thus leading to low conversion efficiency
Used in low-power to medium-power WTs
2. Wind Turbine Aerodynamics Active Stall Control
22
Stalling angle of attack
Strong wind flow (vw > rated)
Fw,stallFull stall Fw,rated
Rated wind flow
Rated angle of attack
(a) At rated wind speed (b) Above rated wind speed
R S
Advanced version of passive stall control with adjustable rotor blades
At higher wind speeds, output power is reduced by moving (pitching) the blades
into the wind, thus causing turbulence (stall mechanism) over the blades
Improves wind energy conversion efficiency at low wind speeds
Ensures that output power does not exceed the rated value during high-wind-speed
conditions
Used in medium-power to high-power WTs.
2. Wind Turbine Aerodynamics Stall Comparison
23
Active stall is more efficient than the passive stall method.
2. Wind Turbine Aerodynamics Pitch Control
24
Full pitchStrong wind flow
(vw > rated)
Fw,pitch
Pitched angle of attack P
Fw,rated
Rated wind flow
Rated angle of attack R
(a) at rated wind speed (b) Above rated wind speed
Rotor blades are adjustable similar to active stall turbines
Pitch control mechanism is assisted by an electronic controller and motor (or hydraulic) drives
During high wind speeds, the rotor blades turn along the longitudinal axis (pitching) such that
angle of attack of the blades is reduced
Active stall method turns the blades “into wind” to create a stall mechanism, whereas pitch
control turns the blades “out of wind”
Provides faster control actions than the passive stall and active stall controls
Used in modern high-power WTs
2. Wind Turbine Aerodynamics Full Stall and Full Pitch
25
Full stall
Photo courtesy: accionsustentable.cl
Full pitch
3. Modeling of Wind Turbines Power Coefficient of WT
26
T
C
i p CeCCC
C CC i
75 2
43 2
1
6
= Tip speed ratio (TSR)T
= Pitch angle (degrees)
71 CC = Turbine constants
= Intermittent TSR i
pwM CvAP 3
2 1 [W]Turbine Mechanical Power:
Power Coefficient:
3. Modeling of Wind Turbines Tip Speed Ratio (TSR)
27
w
TM T v
r ωM – mechanical speed of the turbine (blades)
rT – radius of the turbine rotor (blade length) vw – wind speed
Tλ
pwM CvAP 3
2 1
Mp PC
Rated R
attack of angle R
Relationship between the Power Coefficient and Tip Speed Ratio
Blade tip speed
3. Modeling of Wind Turbines Optimal Tip Speed Ratio (OTSR)
28
Rw
TRM
Rw
TRM optT
v rn
v r
,
,
,
, ,
)60/2(
Optimal tip speed ratio (for variable speed operation):
0 2 4 6 8 0
0.1
0.2
0.3
0.4
10 12 14 16
Cpmax Cp
Rated R
Tλ
λT,opt
= Turbine speed in rpm Mn
= Rated turbine speed in rpm RMn ,
= Turbine mechanical speed (rad/sec) M
= Rated turbine speed (rad/sec) RM ,
= Rated wind speed (m/s) Rwv ,
3. Modeling of Wind Turbines Cp versus TSR
29
0 1
0
0.1
0.2
0.3
0.4 max,pC
o0
o5
o10
pC
optT , T
Cp versus TSR with Pitch Angle β as a Parameter
Pitch angle β: The pitch angle is defined as zero (β= 0) when a turbine operates at the rated conditions with the optimal TSR.
3. Modeling of Wind Turbines Cp versus TSR
30
0
0.1
0.2
0.3
0.4 max,pC
o0
pC
0 2 4 6 8 10 T
optT ,
0.1
0
0.2
0.3
The pitch angle is kept at zero when the wind speed is below its rated value such that the turbine can harvest the maximum power from the wind.
Cp versus TSR – Optimal tip speed ratio
3. Modeling of Wind Turbines Intermittent Tip Speed Ratio
31
)(N.m M
M M
P T
The output mechanical torque of the wind turbine
1 035.0
08.0 11
3
Ti
Intermittent Tip Speed Ratio
)(N.m gbM
M
m
m m r
PP T
The generator mechanical input torque
iλ
3. Modeling of Wind Turbines Gear Ratio and Mechanical Speeds
32
Gear ratio
RM
Rm gb n
n r
,
, = Rated generator speed (rpm) Rmn ,
)rad/sec( ,
T
woptT M r
v
Turbine mechanical speed
for variable speed operation
= Rated turbine speed (rpm) RMn ,
Generator mechanical speed )rad/sec(gbMm r
for fixed speed operation: the turbine speed is almost fixed by the generator
)rad/sec(,RMM
3. Modeling of Wind Turbines Example 1
33
Given: Wind turbine parameters
Parameter Value Rated turbine mechanical output power, PM,R 2.3339 MW Rated generator mech input torque, Tm,R 14740 N.m Air density, ρ 1.225 Kg.m3
Turbine rotor radius, rT 46.5 m Rated turbine speed, nM,R 16 rpm Rated wind speed, vw,R 12 m/s Pitch angle, β 0° (zero degree at the rated output)
Turbine constants, [C1 C2 C3 C4 C5 C6 C7] [0.7029, 116.055, 0.4, 0, 8.6614, 21.5, 0.00684]
Rated generator output power, Ps,R 2.3 MW Rated generator speed, nm,R 1512 rpm Wind speed 12 m/s
3. Modeling of Wind Turbines Example 1
34
Optimal TSR of wind turbine: Solution:
4926.6 12
5.46)60/2(16)60/2(
,
, ,
Rw
TRM optT v
rn
Intermittent TSR of wind turbine:
4019.8 1
10 035.0
04926.6 1
1 035.0
08.0 11
3
Ti 4019.8 i
Find: • The optimal and intermittent tip speed ratio, • The power coefficient of wind turbine, • The mechanical speed of turbine and gear ratio, and • The turbine output power and generator mechanical input torque.
3. Modeling of Wind Turbines Example 1
35
Solution (Continued)
The power coefficient of wind turbine:
3246.075 2
43 2
1
6
T
C
i p CeCCC
C CC i
The mechanical speed of turbine:
rad/sec6755.1 5.46
124926.6,
T
woptT M r
v
The gear ratio:
5.94 16
1512
,
,
RM
Rm gb n
n r
3. Modeling of Wind Turbines Example 1
36
Solution (Continued)
The turbine output mechanical power:
The generator mechanical input torque:
W103339.23246.0125.46225.1 2 1
2 1 6323 pwM CAvP
N.m14740 5.946755.1
103339.2 6
gbM
M m r
P T
(rated)
(rated)
3. Modeling of Wind Turbines Example 2
37
Given: Wind turbine parameters for DD PMSG
Parameter Value Rated turbine mechanical output power, PM,R 3.0 MW Rated generator mech input torque, Tm,R 1273 kN.m Air density, ρ 1.225 Kg.m3
Turbine rotor radius, rT 43.3553 m Rated turbine speed, nM,R 22.5 rpm Rated wind speed, vw,R 12 m/s Pitch angle, β 0° (zero degree at the rated output)
Turbine constants, [C1 C2 C3 C4 C5 C6 C7] [0.3915, 116, 0.4, 0, 0.5, 21, 0.0192]
Rated generator output power, Ps,R 2.964 MW Rated generator speed, nm,R 22.5 rpm Wind speed Above 12 m/s
3. Modeling of Wind Turbines Example 2: Effect of Pitch Angle on Power Output
38
4. Maximum Power Point Tracking Turbine Power-Speed Characteristics
39
PM – mechanical power of wind turbine ωM – mechanical speed of wind turbine
For a given wind turbine, the curves are fixed at a given wind speed.
4. Maximum Power Point Tracking Fixed Speed WT
40
Turbine/generator operates at the rated speed (1pu).
4. Maximum Power Point Tracking Turbine Power-Speed Characteristics
41
3)( MMP
3 MMP With MPPT,
MMM TP From
2 MMT we have
Turbine (generator) speed is adjusted such that it operates at the maximum power point.
4. Maximum Power Point Tracking Comparison of Fixed-Speed and Variable-Speed WTs
42
For a given wind speed (lower than the rated), the variable speed operation produces more power.
Note: Wind turbines operate below the rated speed most of the time.
4. Maximum Power Point Tracking MPPT 1: Optimal TSR (OTSR) Control
43
Key Points:
• Wind speed is measured.
• wm* (reference) is
provided according to wind
speed.
• Requires WT parameters
• Very widely used in WECS.
4. Maximum Power Point Tracking MPPT 2: WT Power Curves (WTPC)-Based Control
44
Key Points:
• Wind speed is measured. • Ps* (reference) is provided according to wind speed.
4. Maximum Power Point Tracking MPPT 3: Optimal Torque (OT) Control
45
4. Maximum Power Point Tracking MPPT 4: Power Signal Feedback (PSF) Control
46
Key Points:
• Rotor speed is measured. • Ps* (reference) is provided according to rotor speed.
4. Maximum Power Point Tracking Comparison of MPPT Control Techniques
47
OTSR is very widely used in WT industry.