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Wind Turbines Technology. Cataldo Pignatale Product Support Manager Vestas Italia S.r.l. Desire-Net Project. Session Contents. - PowerPoint PPT Presentation
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Wind Turbines Technology
Cataldo Pignatale
Product Support ManagerVestas Italia S.r.l.
Desire-Net Project
2
Session Contents
• Aim: at the end of this session participants will have an overview of the wind turbine generators technologies developed over the years and implemented on the modern wind turbines
• Duration: 35-40min
3
Agenda
• Wind turbines characteristics• Control of power• Type of generators• Connection to grid• Control systems• Grid integration of wind trubines• Construction technologies of a modern wind turbine
4
Wind turbines characteristics
5
Wind Turbine Generator
Definition: Machine capable to convert the kinetic energy of a wind tube into electrical energy.
“Betz' law’’’: less than 16/27 (or 59%) of the kinetic energy in the wind can be converted to mechanical energy using a wind turbine. (Betz' law was first formulated by the German Physicist Albert Betz in 1919)
6
Main parts of a modern wind turbine
Nacelle
Foundation
Blade
Hub
Tower
7
• Rotor axis: horizontal, vertical;• Alignment to the wind: upwind, downwind;• Alignment to the wind: active (forced) or passive
(free) yawing system;• Number of blades: even, odd; 3, 2, 1;• Control of power: pitch, stall, active stall, yaw;• Rotation transmission: with or without gearbox;• Type of generator: synchronous, asynchronous;• Grid connection: direct, indirect;
Horizontal axis rotor Vertical axis rotor
Wind Turbines Characteristics
Upwind turbine Downwind turbineActive yaw mechanism Free yaw mechanism2 blades 1 blade3 blades Pitch controlWith gerabox Without gearbox
8
Control of power
9
Control of powerReducing the power at high windspeed
• Reducing the lift and over speeding called Pitch variable speed
• Reducing the lift by generating stall
Flow on upper and lower surface equal no lift
Wind attack point
Wind attack point
At high wind the power is reduced by pitching the blades. This can be done in two ways.
10
Control of powerPitching
Low wind High wind Stop
Pitch variable speed and optislip
Active stall
Passive stall
11
Control of powerWind Power and Power Curves
m/s
Power
‘A’ is area ‘v’ is velocity (wind speed)‘’ is air density ‘Cp’ power coefficient
Wind power
Max Power = ½ · A · v3 · · Cp
Rated power
Pitch variable speed
Active stall
Passive stall
12
Control of powerIso-power map wind speed and pitch angle
― Pitch control
0 kW
500 kW
1000 kW
1500 kW
2000 kW
2500 kW
Win
d s
pe
ed m
/s
5
25
15
10
20
-10 0 +10 +20 +30
Pitch angle (deg)-20
72 m rotor 2MW turbine
― Stall control
13
Control of powerPitching mechanism
Pinion
Blade turning gear
Battery bank
Electrical
Hydraulic
14
Type of generators
15
Type of generator
Synchronous Asynchronous
16
Type of generatorFixed speed asynchronous generator
50 Hz
60 x frequencynumber of pole pairs
rpm =
Rotational speed6-poled stator
rpm1000
+ kW (generator)
- kW(motor)
17
Type of generator Variable speed asynchronous generators
50 Hz
AC
DC AC
DC
Stator field = 1000 rpm
Rotor mechanically = 1100 rpm
18
Connection to the grid
19
Connection to grid Direct
Grid frequency AC
PCC
Grid frequency AC
20
Connection to gridIndirect
Variable frequency AC
(e.g. from synchronous generator)DC
Irregular switched AC Grid frequency AC
Rectifier Inverter PCC
21
Control systems
22
Control systems Fixed speed
Get
rieb
e 1:
50
Parkingbrake
Rotorbearing
Bypasscontactor
Soft startequipment
WTGcontrol
Asynchronous generator
6 ... 33 kV, f = 50 Hz/6 ... 34,5 kV, f = 60 Hz
Step-uptransformer
HVswitchgear
ABB drawing Passive Stall
Gearbox
Generatorswitchgear
ACf = constantn = costant
23
Control systems Fixed speed
Get
rieb
e 1:
50
Parkingbrake
Rotorbearing
Bypasscontactor
Soft startequipment
WTGcontrol
Asynchronous generator
Step-uptransformer
HVswitchgear
ABB drawing Active Stall, Pitch Control
Gearbox
Generatorswitchgear
ACf = constantn = costant
Pitchdrive
6 ... 33 kV, f = 50 Hz/6 ... 34,5 kV, f = 60 Hz
24
Control systems Semi-variable speed
ABB drawing Variable slip, pitch control
Get
rieb
e 1:
50
Parkingbrake
Rotorbearing
Bypasscontactor
Soft startequipment
WTGcontrol
Asynchronous generator
Step-uptransformer
HVswitchgear
Gearbox
Generatorswitchgear
ACf = constantn = semi-variable
Pitchdrive
RCCunit
RCCcontrol
HEAT
6 ... 33 kV, f = 50 Hz/6 ... 34,5 kV, f = 60 Hz
25
Control systemVariable speed
ABB drawing Variable speed control DFIG (doubly fed induction generator)
Get
rieb
e 1:
50
Parkingbrake
Rotorbearing
WTGcontrol
Doubly-fedasynchronous
generator Step-uptransformer
HVswitchgear
Gearbox
Generatorswitchgear
ACf = constantn = variable
Pitchdrive
Generatorside
converter
Gridside
converter
Converter control
6 ... 33 kV, f = 50 Hz/6 ... 34,5 kV, f = 60 Hz
26
Control system Variable speed
ABB drawing Variable speed control with full scale converter
Get
rieb
e 1:
50
Parkingbrake
Rotorbearing
WTGcontrol
Step-uptransformer
HVswitchgear
Gearbox
Generatorswitchgear
ACf = variablen = variable
Pitchdrive
Converter control
6 ... 33 kV, f = 50 Hz/6 ... 34,5 kV, f = 60 Hz
Asynchronous or synchrounous generator
Converter
27
Control system Generator layout
Pitch/Stall/Active stall
Variable speed (DFIG)
1-2% slip
Stator Rotor
Grid
1-10 % slip
IGBT
Grid
Capacitor battery
Stator Rotor
Grid
Grid
DC
DC
Ac
dc Ac
dc
Stator Rotor
Semi-variable speed
Grid
Stator RotorDC
DC
Ac
dc Ac
dc
Variable speed, full scale converter
28
Grid integration of wind turbines
29
Grid integration of wind turbines Electric power path to consumers
Transformer station
Power station
Transformer station Consumer
Transformerstation
20,000V
400,000V
150,000V
20,000V
400/ 230 V
30
Grid integration of wind turbines Medium and high voltage components
Grid
G
Transformer
Main contactors
Generator
Switchgear
31
2
1
3
45
6
7
8
76
LEGENDA:1
PORTA DUE ANTE IN LAMIERA ZINCATA 120x215 cm.CON CHIUSURA A TRE PUNTI, BLOCCO AREL E RETE ANTINEVE
2
3 QUADRO DI BASSA TENSIONE AUSILIARI
GOLFARI DI SOLLEVAMENTOEPORTA DUE ANTE IN LAMIERA ZINCATA 120x215 cm.CON CHIUSURA A TRE PUNTI E RETE ANTINEVE
4
6
7TRASFORMATORE 900 kVA
MODULI MT
5
8
GRIGLIA ALTA IN VTR 120x50 cm. CON RETE ANTINEVE
CHIUSINO IN LAMIERA PER PASSAGGIO AL BASAMENTO
GRIGLIA BASSA IN VTR 120x50 cm. CON RETE ANTINEVE
2000
4500
5000
2290
3000
2500
2360
E
E
E
E
470
1670
0 2690
3890
470
16700
1850
650
0
50300 1650 745 595
200
50510
200
600
510200
780
800
780
380
600
680
600
100
1860
200
300
100
1
2
2
13
1316
17
20
1919
750
A
B
C
D
Grid integration of wind turbines Step-up transformer location
External housingInside tower housingNacelle housing
32
Grid integration of wind turbines Connection of wind turbines
33
Grid integration of wind turbines
The wind turbines operate as a part of an integrated power system with other production sources and consumers. Therefore there is a mutual influence between the wind turbines and the grid.
The following issues have to be considered:1.Layout of grid-connecting infrastructure2.Power quality assessment 3.Electrical system stability issues
34
Grid integration of wind turbines Power quality assessment
Operation of wind turbine can be disturbed if following grid parameter are not within defined limits:•Voltage•Frequency•Voltage unbalance•Harmonics level
Wind turbine connection shall not reduce existing power quality on the grid
35
Grid integration of wind turbines Parameters relevant for correct operation of wind turbines
• Voltage limits: • Regime limits• Slow transient limits
• Frequency limits:• Normal operation limits• Admitted transient limits
• Voltage unbalance:• Admitted operational limits
• Harmonics level:• Recommended maximum value: As defined in EN 50160
36
Grid integration of wind turbines Possible negative impacts of WT to the power quality on electrical grid
Wind turbines can cause the following negative impact on the grid:•Stationary voltage increase•High in-rush current•Flicker•Harmonics and inter-harmonics
Generally, the wind turbines´ impact on the grid depends on:•Wind turbines characteristics•The grid characteristics at the connection point (PCC)
Strong grids can accept more wind turbine without negative consequences on power quality.Weak grids can accept limited number of wind turbines, or the grid has to be reinforced.
37
Grid integration of wind turbines Flicker
Flicker describes the effects of rapid voltage variations on electrical light. The flicker level can be measured with an instrument called flicker-meter.•Flicker during continuous operation•Flicker due to generator switching
Limits are defined at PCC and global effect has to be calculated as aggregated contribution of all the installed wind turbines.
Wind turbine´s performances concerning flicker emission are characterised by:•flicker coeficient cf
•flicker step factor kf
38
Grid integration of wind turbines Harmonics and inter-harmonics
Voltage deviations from the perfect sinus shaped 50 Hz curve result in harmonics.
Harmonics are not wanted on the grid because they cause increased losses and in serious cases it may lead to an overloading of the capacitors, trans-formers and electrical appliances as well as disturbances of communication systems and control equipment.
It is differed between:•Even harmonics e.g. 100, 200, 300… Hz•Odd harmonics e.g. 150, 250, 350,550 … Hz•Inter-armonics (50 multiplied with decimal numbers)e.g. 165 Hz, 2525 Hz etc.
39
Grid integration of wind turbines Standards and recommendations
All units that deliver electrical power to electrical system shall respect relevant power quality standards.
The most relevant documents for wind turbines are:•IEC 61400-21 standard:•“Power quality requirements for grid connected wind turbines”
•IEC 61400-3 standard:•“ EMC limits. Limitation of emissions of harmonic currents for equipment connected to medium and high voltage power supply systems”
•Local requirements
40
Grid integration of wind turbines System stability issue
Large wind farms can influence not only locally grid but also a large part of whole power supply system•Dynamic grid stability may be a limiting factor to the grid connection of large wind farms•Grid stability analyses are needed •Data for modeling or models of Wind Turbines may be requested
Each country can issue local grid code requirements that have to be duly considered in designing wind parks.Fulfilment of grid code requirements might require installation of additional equipments (capacitor banks, static VAR compensators, dynamic VAR compensators).
41
Coonstruction tecnologies of a modern wind turbine
42
Main parts of a modern wind turbine
Nacelle
Foundation
Blade
Hub
Tower
43
Onshore foundation
•Gravity concrete foundation
•Rock anchor foundation
44
Offshore foundation
•Monopile
•Tripod
•Gravity
•Floating
45
The tower
Tubular• Steel plates are rolled and welded• Flanges at each section• Shot blasted and coated with paint
Lattice• Bars are prepared in factory and
assembled on site• Bolted junctions• Hot galvanized steel
46
Blade concepts
• Supporting carbon spar and glass fiber airfoil shells
• Wood carbon strong shell technology
47
Supporting carbon spar concept
• The supporting spar with a rectangular section
• The airfoil shells with sandwich construction at the rear
48
Wood carbon concept
• Plywood and carbon rods are used where high strength is needed
• Balsa or foam is used where only stiffness is needed
49
Main components in the nacelle
Pitch systemGearbox
Hub
Hydraulic station
Main bearings/Main shaft
Yaw systemDisc brakeGenerator Coupling
Anemometer
50
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