ECE 356 September 10, 2015 Mitch Bradt, PE Electric Power Processing for Alterna6ve Energy Systems, Slide 1 Wind Turbine Generators: The Basics ECE 356—Electric Power Processing for Alternative Energy Systems
ECE 356 September 10, 2015 Mitch Bradt, PE Electric Power Processing for Alterna6ve Energy Systems, Slide 1
Wind Turbine Generators: The Basics
ECE 356—Electric Power Processing for Alternative Energy Systems
ECE 356 September 10, 2015 Mitch Bradt, PE Electric Power Processing for Alterna6ve Energy Systems, Slide 2
U.S. Wind Energy Poten;al
Copyright © 2008 3TIER, Inc. All Rights Reserved. For permission to reproduce or distribute: [email protected]
ECE 356 September 10, 2015 Mitch Bradt, PE Electric Power Processing for Alterna6ve Energy Systems, Slide 3
U.S. Wind Project Installa;ons Source: American Wind Energy Association U.S. Wind Industry Annual Market Report –
2014 Fourth Quarter
ECE 356 September 10, 2015 Mitch Bradt, PE Electric Power Processing for Alterna6ve Energy Systems, Slide 4
WTG: The Basics -‐-‐ Outline
Wind Turbine Generator Technology:
The Mechanical Side Wind Turbine Generator Technology:
The Electrical Side
ECE 356 September 10, 2015 Mitch Bradt, PE Electric Power Processing for Alterna6ve Energy Systems, Slide 5
Wind Turbine Generator Technology: The Mechanical Side
ECE 356 September 10, 2015 Mitch Bradt, PE Electric Power Processing for Alterna6ve Energy Systems, Slide 6
ECE 356 September 10, 2015 Mitch Bradt, PE Electric Power Processing for Alterna6ve Energy Systems, Slide 7
Wind Turbine Generator Technology: The Mechanical Side
ECE 356 September 10, 2015 Mitch Bradt, PE Electric Power Processing for Alterna6ve Energy Systems, Slide 8
LiC and Drag: Aerodynamic Forces
Wind attack point!
lift!
Pressure!
Vacuum!The air moving along the upper!surface of the blade travels faster !than air on the lower surface !
Reduced lift!Flow on upper and lower surface equal ⇒ no lift!
Wind attack point!
Reduced lift , Stall !Wind attack point!
drag!
ECE 356 September 10, 2015 Mitch Bradt, PE Electric Power Processing for Alterna6ve Energy Systems, Slide 9
The wind turbine seen from above:!
ECE 356 September 10, 2015 Mitch Bradt, PE Electric Power Processing for Alterna6ve Energy Systems, Slide 10
The wind turbine seen from above:!
View of the tip profile, the largest profile, the blade twist and blade root (circle)!
The wind direction will vary!
with the wind speed! variation!
!The wind force resulting from the rotor tip speed !!
The tip speed is specific for each WTG type and normally near 60 m/s!
Wind direction!
On the next slides !we will look at the blade tip position!
ROTOR PLANE!
ECE 356 September 10, 2015 Mitch Bradt, PE Electric Power Processing for Alterna6ve Energy Systems, Slide 11
Angle of AIack, alpha
CL
Wind speed12 m/s
60 m/s
Increased power
As wind speed increases, the rotor turning power becomes greater and the generator produces more electricity
The blade section will see the resulting wind direction only and it will create a lifting force (CL)
CL can be split into a rotor thrust force and a power direction
Blade tip speed 60 m/s
Wind speed 8 m/s Resulting wind direction
CL Rotor thrust Power
ECE 356 September 10, 2015 Mitch Bradt, PE Electric Power Processing for Alterna6ve Energy Systems, Slide 12
Wind !speed !16 m/s!
Tip speed 60 m/s! !The stall-mode is developed gradually throughout the blade!
Aerodynamic - Wind influence on the blade!
!!! !!
!The higher wind, the more stall!
!!
!!
Stall rotor- fixed position!
At high wind speed the lift force is lost due to stall!
CL!
Changing the Wind Speed Changes Wind Direction Relative to the Rotor Blade
ECE 356 September 10, 2015 Mitch Bradt, PE Electric Power Processing for Alterna6ve Energy Systems, Slide 13
Aerodynamic - Variable speed !
!!
Blade tip speed 80 m/s!
Wind speed 16 m/s!
CL!
Power!
Blade tip speed 70 m/s!
Wind speed 16 m/s!
CL!
Power!
ECE 356 September 10, 2015 Mitch Bradt, PE Electric Power Processing for Alterna6ve Energy Systems, Slide 14
Pitch regulation and blade position!
q The normal stop position is +90° !
m/s!
kW!
Wind!
l To control the rotor acceleration, the blades have variable blade position in order to carry out a smooth grid cut-in!
l Pitch turbines achieve variable speed compared to the fixed speed rotor of stall wind turbines!
• Up to 7-8 m/s winds,! the pitch is set to 0°!
ECE 356 September 10, 2015 Mitch Bradt, PE Electric Power Processing for Alterna6ve Energy Systems, Slide 15
Genera;ng LiC …
ECE 356 September 10, 2015 Mitch Bradt, PE Electric Power Processing for Alterna6ve Energy Systems, Slide 16
…and then Torque
R
Rotational Speed ω Tip Speed ω⋅R
ECE 356 September 10, 2015 Mitch Bradt, PE Electric Power Processing for Alterna6ve Energy Systems, Slide 17
Betz’s Elemental Momentum Theory
q Given that and
2
21 vmE ⋅= Avm ⋅⋅= ρ
ρ — air density
v — air speed
A— swept area of blades
q Then.. AvEPWind ⋅⋅== 3
21ρ
q We can state that the Power a turbine can extract is:
!"
#$%
& ⋅⋅⋅= AvCP PTurbine3
21ρ
q Betz showed through conservation of momentum that the maximum Power Coefficient (CP) happens when the downstream speed is slowed to 1/3 of the incident speed
593.02716
, ==BetzPC
ECE 356 September 10, 2015 Mitch Bradt, PE Electric Power Processing for Alterna6ve Energy Systems, Slide 18
Real Power Coefficients
q It turns out that energy is lost due: • Finite number of Blades • Wake Rotation • Airfoil Drag
Tip Speed Ratio
WindVR⋅=ωλ
ECE 356 September 10, 2015 Mitch Bradt, PE Electric Power Processing for Alterna6ve Energy Systems, Slide 19
Wind Turbine Generator Technology: The Electrical Side
ECE 356 September 10, 2015 Mitch Bradt, PE Electric Power Processing for Alterna6ve Energy Systems, Slide 20
Power Systems
ECE 356 September 10, 2015 Mitch Bradt, PE Electric Power Processing for Alterna6ve Energy Systems, Slide 21
AC Systems • Power system voltages and currents are AC, and have the form
where in N. America.
• Instantaneous power
• Manipulating where
Real component
Imaginary component
ECE 356 September 10, 2015 Mitch Bradt, PE Electric Power Processing for Alterna6ve Energy Systems, Slide 22
Instantaneous Power V and I in phase I lags V by 30 deg
P=0.5, Q=0.0 P=0.433, Q=0.25
ECE 356 September 10, 2015 Mitch Bradt, PE Electric Power Processing for Alterna6ve Energy Systems, Slide 23
Apparent (complex) Power l Using phasors to find P and Q.
– Apparent power: Volt-Amps “VA” – Power factor: = P/S =
Active power Watts
Reactive power Volt-Amps Reactive “VARs”
(where * means complex conjugate)
ECE 356 September 10, 2015 Mitch Bradt, PE Electric Power Processing for Alterna6ve Energy Systems, Slide 24
Ac;ve (real) and Reac;ve (imaginary) Power l Active power – frequency.
– System frequency is governed (approximately) by
§ System frequency, § Total mechanical power, § Total electrical power,
– If exceeds , the power system will slow down. – If exceeds , the power system will speed up. – Governors on generators regulate system frequency by controlling the
mechanical power. l Reactive power – voltage.
– Not as simple as frequency dynamics. – General principle:
§ Injecting reactive power into the system raises (local) voltages. § Absorbing reactive power from the system lowers (local) voltages.
§ Total system inertia, § Total system damping,
ECE 356 September 10, 2015 Mitch Bradt, PE Electric Power Processing for Alterna6ve Energy Systems, Slide 25
Basic 3φ Machine Types
If
N
S
a-
a+
b-
c+ b+
c-
ω
Wound Rotor Synchronous:
a-
a+
b-
c+ b+
c- N
S
a-
a+
b+
b-
c+
c-
Permanent Magnet Synch. Induction
ω
Characteristic Wound Rotor Synch Perm Magnet Synch Induction Rotor Speed (Elec.): Synchronous with ω Asynchronous (slip) Rotor Field Excitation: Varies-—field winding Fixed—PM Varies by Induction Power Range: kW-GW W-kW W-MW Reactive Power: Source or Sink ≅0 Sink Conventionally used: Almost all Generation “new kid on the block” Most Industrial Motors Used in WTG: Some, not many Increasing in WTG First turbines
Only type 4 Types 1, 2, 3
ECE 356 September 10, 2015 Mitch Bradt, PE Electric Power Processing for Alterna6ve Energy Systems, Slide 26
Basic Synchronous Machines
If
N
S
A-
A+
B-
C+ B+
C-
ω
q Sinusoidally Distributed Balanced 3φ Stator Windings
Stator Windings (Distributed)
Rotor Winding (Distributed)
Wound Rotor
l The Rotor Field Winding is Energized with DC Current If.
(2-Pole Machines Depicted)
l The Field Bf Rotates Synchronously with the Rotor at speed ω:
– Induces Sinewave Voltages in Stator Windings
Bf
ECE 356 September 10, 2015 Mitch Bradt, PE Electric Power Processing for Alterna6ve Energy Systems, Slide 27
Basic Induc;on Machines
q Sinusoidally Distributed Balanced 3φ Stator Windings
q Rotor Speed is Generally Non-Synchronous: Rotor Can turn Faster (Generator) …
… or Slower (Motor) than Input Frequency
q Wound Rotors: • Rotor Windings brought out through Slip Rings: Allowing Speed/Torque Control
q “Squirrel-Cage” Rotors: • Rotor Windings are simple Shorted Bars cast into Rotor Laminations
• Low-Cost, Rugged è Commercial / Industrial Work-Horse FIRST WINDTURBINES
Wound Rotor Squirrel-Cage Rotor
a-
a+
b+
b-
c+
c-
ωr
ωωω rs −
=Slip:
ECE 356 September 10, 2015 Mitch Bradt, PE Electric Power Processing for Alterna6ve Energy Systems, Slide 28
Type 1 Wind Turbine
Fixed Speed -- limited control of slip (2-3%) and Real Power Consumes VARs
Gear Box IG Collector
Feeder
The rotor blades may be pitch-regulated to control power
Soft Starter Cap Bank
Examples: Vestas V-82, Mitsubishi MWT-1000 ** becoming less common
ECE 356 September 10, 2015 Mitch Bradt, PE Electric Power Processing for Alterna6ve Energy Systems, Slide 29
Real and Reac;ve Power
ECE 356 September 10, 2015 Mitch Bradt, PE Electric Power Processing for Alterna6ve Energy Systems, Slide 30
Type 2 Wind Turbine
Variable Speed -- More control of slip (up to 10%) Consumes VARs
Variable Rotor Resistance • Via slip rings with wound rotor IG • Placed on rotor as with OptiSlip®
Gear Box IG Collector
Feeder
Soft Starter Cap Bank
Examples: Vestas V-47, Suzlon S-64/88 no longer common—stepping stone to Type 3…
ECE 356 September 10, 2015 Mitch Bradt, PE Electric Power Processing for Alterna6ve Energy Systems, Slide 31
Real and Reac;ve Power with Rext
ECE 356 September 10, 2015 Mitch Bradt, PE Electric Power Processing for Alterna6ve Energy Systems, Slide 32
Type 3 Wind Turbine Variable Speed -- More control of slip (up to 50%) Can control VARs Partial Scale Converters Required (~30% of Machine)
Gear Box
Collector Feeder IG
IG Pstator
Protor
Pnet
Operation Below Synchronous Speed
IG Pstator
Protor
Pnet
Operation Above Synchronous Speed
Ex: GE 1.5, Acciona 1500, Vestas V90, Gamesa G80 ** State of the Art
REPower 5M (126 m dia.) Commissioned offshore. 5MW Output Based on Doubly Fed type machine
ECE 356 September 10, 2015 Mitch Bradt, PE Electric Power Processing for Alterna6ve Energy Systems, Slide 34
Type 4 Wind Turbine
Variable Speed -- Wide control of slip (up to 100%) Can control VARs Full Scale Converters Required (>100% of Machine)
Machine’s excitation can be controlled by machine side converter ⇒Can use any type of machine! Field Wound SG, PM-SG or even IG
Gear Box
IG/ SG
Collector Feeder
An opportunity to eliminate the gearbox exists Since “Wild AC” from generator can be conditioned to 60Hz grid
Ex: GE 2.5, Siemens 2.3, Clipper 2.5, Enercon E112 ** State of the Art
ECE 356 September 10, 2015 Mitch Bradt, PE Electric Power Processing for Alterna6ve Energy Systems, Slide 35
Areva Wind
Direct-Drive���PM Wind Turbines
q S;sldjfl;asjdf
l Many alternative wind turbine and PM machine configurations
l Machine ratings up to 8 MW
ABB
GE The Switch
ECE 356 September 10, 2015 Mitch Bradt, PE Electric Power Processing for Alterna6ve Energy Systems, Slide 36
Size of Modern Wind Generators
Manwell Fig 1.15
ECE 356 September 10, 2015 Mitch Bradt, PE Electric Power Processing for Alterna6ve Energy Systems, Slide 37
Factors Driving Recent Growth of Wind Power
• Fiber composites for constructing low cost blades.
• Improved operation and maintenance leading to increased availability.
• Economy of scale.
• Application of power electronics to allow variable blade speed and enhance efficiency and energy output.
• Decreasing cost of power electronics.
• Accumulated field experience improving the capacity factor (% of rated kWhr attained on annual basis)
(in addition to financial subsidies)
ECE 356 September 10, 2015 Mitch Bradt, PE Electric Power Processing for Alterna6ve Energy Systems, Slide 38
Thank You!
q Are there any Questions?
Mitch Bradt, PE [email protected]