Answer each questionin a paragraph in 12hr
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 p w M C v A P3 2 1 Mechanical power captured by the blade: ρ ‐air density [kg/m 3] A‐swept area [m 2] v w ‐wind speed [m/sec] C p ‐power coefficient of the blade Direction of rotation [W] 1. Wind Turbine Components Turbine Blades 7 Mechanical power P T extracted from the wind kinetic power P w is: p w p w M C v A C P P 3 2 1 W C p = power coefficient of blades. Maximum value is __________.
Practical values are between ________ and _________.
ρ= air density (kg/m 3). 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/m 3.
A = rotor swept area (m 2) = Ê ˜ € Û r T = blade radius (m) v w = 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/m 3, r T = 43.36 m, v w = 12 m/s, and C p = 0.48.
Calculate P T. Solution:
p w T C v A P 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 v w (m/s) Rated power P M Cut-in Ra ted 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,stall Full 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 pitch Strong wind flow ( vw > rated)F w,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 C e C C C C C C i 7 5 2 4 3 2 1 6 = Tip speed ratio (TSR) T = Pitch angle (degrees) 7 1 C C = Tu rb i n e constants = Intermittent TSR i p w M C A P 3 2 1 [W] Tu rb i n e Mechanical Power:
Power Coefficient: 3. Modeling of Wind Turbines Tip Speed Ratio (TSR) 27 wT M T vr ω M – mechanical speed of the turbine (blades) rT –radius of the turbine rotor (blade length) v w –wind speed Tλ p w M C v A P3 2 1 M pP C Rated R attack of angle R Relationship between the Power Coefficientand Tip Speed Ratio Blade tip speed 3. Modeling of Wind Turbines Optimal Tip Speed Ratio (OTSR) 28 R wT R MR wT R M opt T vr nvr , ,, , , ) 60 / 2 ( Optimal tip speed ratio (for variable speed operation): 02 46 8 0 0.1 0.2 0.3 0.4 1012 14 16 C pmax Cp Rated R Tλ λT,opt = Tu rb i n e speed in rpm M n = Rated turbine speed in rpm R M n , = Tu rb i n e mechanical speed (rad/sec) M = Rated turbine speed (rad/sec) R M, = Rated wind speed (m/s) R w v , 3. Modeling of Wind Turbines C p versus TSR 29 01 0 0.1 0.2 0.3 0.4 max , p C o0 o5 o 10 p C opt T, T C p versus TSR with Pitch Angleβas 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 C p versus TSR 30 0 0. 1 0. 2 0. 3 0. 4 max , p C o0 p C 0 2 4 6 8 10 T opt T, 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. C p 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 . 01 1 3 T i Inter mittent Tip Speed Ratio ) (N.m gb MM m m mr P P T The generator mechanical input torque i λ 3. Modeling of Wind Turbines Gear Ratio and Mechanical Speeds 32 Gear ratio R MR m gb nn r , , = Rated generator speed (rpm) R m n , ) rad/sec ( , Tw opt T M rv Tu rb i n e mechanical speed for variable speed operation = Rated turbine speed (rpm) R M n , Generator mechanical speed ) rad/sec ( gb M mr for fixed speed operation: the turbine speed is almost fixed by the generator ) rad/sec ( ,R M M 3. Modeling of Wind Turbines Example 1 33 Given: Wind turbine parameters Parameter Value Rated turbine mechanical output power, P M,R 2.3339 MW Rated generator mech input torque, T m,R 14740 N.m Air density, ρ 1.225 Kg.m 3 Tu rb i n e rotor radius, rT 46.5 m Rated turbine speed, n M,R 16 rpm Rated wind speed, v w, R 12 m/s Pitch angle, β 0° (zero degree at the rated output) Tu rb i n e constants, [C 1 C 2 C 3 C 4 C 5 C 6 C 7][0.7029, 116.055, 0.4, 0, 8.6614, 21.5, 0.00684] Rated generator output power, P s,R 2.3 MW Rated generator speed, n m,R 1512 rpm Wind speed 12 m/s 3. Modeling of Wind Turbines Example 1 34 Optimal TSR of wind turbine: Solution: 4926 . 6 125 . 46 ) 60 / 2 ( 16 ) 60 / 2 ( , , , R wT R M opt T vr n Intermittent TSR of wind turbine: 4019 . 81 1 0035 . 0 0 4926 . 61 1 035 . 0 08 . 01 1 3 T i 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 . 0 7 5 2 4 3 2 1 6 T C i p C e C C C C C C i The mechanical speed of turbine: rad/sec 6755 . 1 5 . 4612 4926 . 6 , Tw opt T Mrv The gear ratio: 5 . 94 16 1512 , , R MR m gb nn r 3. Modeling of Wind Turbines Example 1 36 Solution (Continued) The turbine output mechanical power:
The generator mechanical input torque: W 10 3339 . 2 3246 . 0 12 5 . 46 225 . 1 2 1 2 1 6 3 2 3 p w M C Av P N.m 14740 5 . 94 6755 . 110 3339 . 2 6 gb MM mr 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, P M,R 3.0 MW Rated generator mech input torque, T m,R 1273 kN.m Air density, ρ 1.225 Kg.m 3 Tu rb i n e rotor radius, rT 43.3553 m Rated turbine speed, n M,R 22.5 rpm Rated wind speed, v w, R 12 m/s Pitch angle, β 0° (zero degree at the rated output) Tu rb i n e constants, [C 1 C 2 C 3 C 4 C 5 C 6 C 7][0.3915, 116, 0.4, 0, 0.5, 21, 0.0192] Rated generator output power, P s,R 2.964 MW Rated generator speed, n m,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 P M – mechanical power of wind turbine ω M – 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 Tu rb i n e /ge n e rato r operates at the rated speed (1pu). 4. Maximum Power Point Tracking Turbine Power-Speed Characteristics 41 3) ( M M P 3 M M P With MPPT, M M M T P From 2 M M T we have Tu rb i n e (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. •w m *(reference) is provided according to wind speed. •Requires WT parameters •Ve r y widely used in WECS. 4. Maximum Power Point Tracking MPPT 2: WT Power Curves (WTPC)-Based Control 44 Key Points: •Wind speed is measured. •P s*(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. •P s*(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.
