Difference between revisions of "Wind Turbine Technology"
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| − | + | [[Portal:Wind|► Back to Wind Portal]] | |
| − | + | = Overview = | |
| − | == | + | A wind turbine is a device that converts kinetic energy from the wind into electrical power<ref name="http://en.wikipedia.org/wiki/Wind_turbine">http://en.wikipedia.org/wiki/Wind_turbine</ref>.The role of wind turbines is to extract energy from wind and convert it to electrical energy. This extraction is subjected to certain limitations represented by Betz’s limit which is the maximum energy possible to convert kinetic energy into mechanical energy without any losses<ref name="J. F. Manwell, J. G. McGowan and A. L. Rogers. WIND ENERGY; Theory, Design and Application. United Kingdom : John Wiley & Sons Ltd, 2009">J. F. Manwell, J. G. McGowan and A. L. Rogers. WIND ENERGY; Theory, Design and Application. United Kingdom : John Wiley & Sons Ltd, 2009</ref>. |
| − | < | + | <br/> |
| − | == | + | == Basic Theory == |
An ideal wind turbine has a maximum power coefficient of 16/27.The theoretical limit cannot be exceeded and this caused by the aerodynamic losses due to conversion of angular momentum,tip and drag<ref>DESIGN AND POWER CHARACTERIZATION OF A SMALL WIND TURBINE MODEL IN PARTIAL LOAD REGION by Abdulkarim Abdulrazek</ref>. | An ideal wind turbine has a maximum power coefficient of 16/27.The theoretical limit cannot be exceeded and this caused by the aerodynamic losses due to conversion of angular momentum,tip and drag<ref>DESIGN AND POWER CHARACTERIZATION OF A SMALL WIND TURBINE MODEL IN PARTIAL LOAD REGION by Abdulkarim Abdulrazek</ref>. | ||
| − | [[File:Wind turbine limitation.png|left| | + | [[File:Wind turbine limitation.png|left|450px|Power coefficients of different rotors of different designs|alt=Power coefficients of different rotors of different designs]]<br/> |
Turbine Power output can can be expressed as follows: | Turbine Power output can can be expressed as follows: | ||
| − | + | P= ½ * ρ* A * v³* Cp | |
| − | where | + | where ρ is density of air, A is the area swept by rotor and v is the velocity of wind. |
| − | |||
| − | |||
The extracted power is then converted into electrical power and is defined as: | The extracted power is then converted into electrical power and is defined as: | ||
| Line 30: | Line 28: | ||
V is the voltage in V<br/> | V is the voltage in V<br/> | ||
| − | I is the current in A | + | I is the current in A |
| + | |||
| + | <br/> | ||
| + | |||
| + | Betz Theory is the maximum possible Cp=16/27 which means 59% efficiency is the best a conventional wind turbine can do in extracting power from the wind.<br/> | ||
| + | |||
| + | [[Wind Turbine Technology#toc|►Go to Top]] | ||
=== Aerodynamics<br/> === | === Aerodynamics<br/> === | ||
| − | [[File:Wind turbine blade aerodynamics.jpg|frame|center|180px|Aerodynamics of a wind turbine blade]]<ref>Weigel S., Poeller M. (2010) Wind Turbine Generators (WTGs) Physical Principals and Generator Concepts, Presentation prepared by DigSILENT GmbH for the Wind Energy and Development Dialogue 2010, retrieved 27.8.2011 [[http://www.gtz.de/de/dokumente/gtz2010-en-wedd-1-2-WTG-concepts.pdf]]</ref> | + | [[File:Wind turbine blade aerodynamics.jpg|frame|center|180px|Aerodynamics of a wind turbine blade]]<ref name="Weigel S., Poeller M. (2010) Wind Turbine Generators (WTGs) Physical Principals and Generator Concepts, Presentation prepared by DigSILENT GmbH for the Wind Energy and Development Dialogue 2010, retrieved 27.8.2011 [[http://www.gtz.de/de/dokumente/gtz2010-en-wedd-1-2-WTG-concepts.pdf]]">Weigel S., Poeller M. (2010) Wind Turbine Generators (WTGs) Physical Principals and Generator Concepts, Presentation prepared by DigSILENT GmbH for the Wind Energy and Development Dialogue 2010, retrieved 27.8.2011 [[http://www.gtz.de/de/dokumente/gtz2010-en-wedd-1-2-WTG-concepts.pdf]]</ref> [[Wind Turbine Technology#toc|►Go to Top]] |
=== Stall === | === Stall === | ||
| − | [[File:Wind turbine blade aerodynamics - stall control.jpg|frame|center|180px|Wind turbine blade aerodynamics - stall control]]<ref>Weigel S., Poeller M. (2010) Wind Turbine Generators (WTGs) Physical Principals and Generator Concepts, Presentation prepared by DigSILENT GmbH for the Wind Energy and Development Dialogue 2010, retrieved 27.8.2011 [[http://www.gtz.de/de/dokumente/gtz2010-en-wedd-1-2-WTG-concepts.pdf]]</ref> | + | [[File:Wind turbine blade aerodynamics - stall control.jpg|frame|center|180px|Wind turbine blade aerodynamics - stall control]]<ref name="Weigel S., Poeller M. (2010) Wind Turbine Generators (WTGs) Physical Principals and Generator Concepts, Presentation prepared by DigSILENT GmbH for the Wind Energy and Development Dialogue 2010, retrieved 27.8.2011 [[http://www.gtz.de/de/dokumente/gtz2010-en-wedd-1-2-WTG-concepts.pdf]]">Weigel S., Poeller M. (2010) Wind Turbine Generators (WTGs) Physical Principals and Generator Concepts, Presentation prepared by DigSILENT GmbH for the Wind Energy and Development Dialogue 2010, retrieved 27.8.2011 [[http://www.gtz.de/de/dokumente/gtz2010-en-wedd-1-2-WTG-concepts.pdf]]</ref> |
| − | <u>Stall Control</u> | + | <u>Stall Control:</u> |
| − | * | + | *Passive Stall |
| + | *Power of the wind turbine is limited by the aerodynamic characteristics of the turbine. | ||
| − | + | <u>Active Stall</u> | |
| − | |||
| − | |||
| − | |||
| − | |||
| − | Active Stall | ||
Power of the wind turbine is limited additionally by decreasing the pitch angle (increasing the inflow angle ). | Power of the wind turbine is limited additionally by decreasing the pitch angle (increasing the inflow angle ). | ||
| − | + | [[Wind Turbine Technology#toc|►Go to Top]] | |
=== Pitch<br/> === | === Pitch<br/> === | ||
| − | [[File:Wind turbine blade aerodynamics - pitching.jpg|frame|center|180px|Aerodynamics at a wind turbine blade during control through pitching]]<ref>Weigel S., Poeller M. (2010) Wind Turbine Generators (WTGs) Physical Principals and Generator Concepts, Presentation prepared by DigSILENT GmbH for the Wind Energy and Development Dialogue 2010, retrieved 27.8.2011 [[http://www.gtz.de/de/dokumente/gtz2010-en-wedd-1-2-WTG-concepts.pdf]]</ref> | + | [[File:Wind turbine blade aerodynamics - pitching.jpg|frame|center|180px|Aerodynamics at a wind turbine blade during control through pitching]]<ref name="Weigel S., Poeller M. (2010) Wind Turbine Generators (WTGs) Physical Principals and Generator Concepts, Presentation prepared by DigSILENT GmbH for the Wind Energy and Development Dialogue 2010, retrieved 27.8.2011 [[http://www.gtz.de/de/dokumente/gtz2010-en-wedd-1-2-WTG-concepts.pdf]]">Weigel S., Poeller M. (2010) Wind Turbine Generators (WTGs) Physical Principals and Generator Concepts, Presentation prepared by DigSILENT GmbH for the Wind Energy and Development Dialogue 2010, retrieved 27.8.2011 [[http://www.gtz.de/de/dokumente/gtz2010-en-wedd-1-2-WTG-concepts.pdf]]</ref> |
<u>Pitch Control:</u> | <u>Pitch Control:</u> | ||
*Power of the wind turbine is limited by increasing the pitch angle (decreasing the inflow angle <span class="texhtml">α</span>) | *Power of the wind turbine is limited by increasing the pitch angle (decreasing the inflow angle <span class="texhtml">α</span>) | ||
| − | + | [[Wind Turbine Technology#toc|►Go to Top]] | |
== Wind Turbine Operation<br/> == | == Wind Turbine Operation<br/> == | ||
| Line 72: | Line 72: | ||
*In case of large wind speeds: Power limited by aerodynamic profile. | *In case of large wind speeds: Power limited by aerodynamic profile. | ||
| − | + | [[Wind Turbine Technology#toc|►Go to Top]] | |
=== Operation of Variable Speed Wind-Turbines<br/> === | === Operation of Variable Speed Wind-Turbines<br/> === | ||
| Line 94: | Line 94: | ||
<br/> | <br/> | ||
| − | <ref>Weigel S., Poeller M. (2010) Wind Turbine Generators (WTGs) Physical Principals and Generator Concepts, Presentation prepared by DigSILENT GmbH for the Wind Energy and Development Dialogue 2010, retrieved 27.8.2011 [[http://www.gtz.de/de/dokumente/gtz2010-en-wedd-1-2-WTG-concepts.pdf]]</ref> | + | <ref name="Weigel S., Poeller M. (2010) Wind Turbine Generators (WTGs) Physical Principals and Generator Concepts, Presentation prepared by DigSILENT GmbH for the Wind Energy and Development Dialogue 2010, retrieved 27.8.2011 [[http://www.gtz.de/de/dokumente/gtz2010-en-wedd-1-2-WTG-concepts.pdf]]">Weigel S., Poeller M. (2010) Wind Turbine Generators (WTGs) Physical Principals and Generator Concepts, Presentation prepared by DigSILENT GmbH for the Wind Energy and Development Dialogue 2010, retrieved 27.8.2011 [[http://www.gtz.de/de/dokumente/gtz2010-en-wedd-1-2-WTG-concepts.pdf]]</ref> |
| + | |||
| + | [[Wind Turbine Technology#toc|►Go to Top]] | ||
== Generator Concepts<br/> == | == Generator Concepts<br/> == | ||
| − | [[File:Overview Wind generator concepts.jpg|frame|center|180px|Overview Wind generator concepts.jpg]]<ref>Weigel S., Poeller M. (2010) Wind Turbine Generators (WTGs) Physical Principals and Generator Concepts, Presentation prepared by DigSILENT GmbH for the Wind Energy and Development Dialogue 2010, retrieved 27.8.2011 [[http://www.gtz.de/de/dokumente/gtz2010-en-wedd-1-2-WTG-concepts.pdf]]</ref> | + | [[File:Overview Wind generator concepts.jpg|frame|center|180px|Overview Wind generator concepts.jpg]]<ref name="Weigel S., Poeller M. (2010) Wind Turbine Generators (WTGs) Physical Principals and Generator Concepts, Presentation prepared by DigSILENT GmbH for the Wind Energy and Development Dialogue 2010, retrieved 27.8.2011 [[http://www.gtz.de/de/dokumente/gtz2010-en-wedd-1-2-WTG-concepts.pdf]]">Weigel S., Poeller M. (2010) Wind Turbine Generators (WTGs) Physical Principals and Generator Concepts, Presentation prepared by DigSILENT GmbH for the Wind Energy and Development Dialogue 2010, retrieved 27.8.2011 [[http://www.gtz.de/de/dokumente/gtz2010-en-wedd-1-2-WTG-concepts.pdf]]</ref> |
| + | |||
| + | [[Wind Turbine Technology#toc|►Go to Top]] | ||
=== Fixed Speed Induction Generator<br/> === | === Fixed Speed Induction Generator<br/> === | ||
| − | [[File:Fixed speed induction generator.jpg|frame|center|180px|Fixed speed induction generator.jpg]]<ref>Weigel S., Poeller M. (2010) Wind Turbine Generators (WTGs) Physical Principals and Generator Concepts, Presentation prepared by DigSILENT GmbH for the Wind Energy and Development Dialogue 2010, retrieved 27.8.2011 [[http://www.gtz.de/de/dokumente/gtz2010-en-wedd-1-2-WTG-concepts.pdf]]</ref> | + | [[File:Fixed speed induction generator.jpg|frame|center|180px|Fixed speed induction generator.jpg]]<ref name="Weigel S., Poeller M. (2010) Wind Turbine Generators (WTGs) Physical Principals and Generator Concepts, Presentation prepared by DigSILENT GmbH for the Wind Energy and Development Dialogue 2010, retrieved 27.8.2011 [[http://www.gtz.de/de/dokumente/gtz2010-en-wedd-1-2-WTG-concepts.pdf]]">Weigel S., Poeller M. (2010) Wind Turbine Generators (WTGs) Physical Principals and Generator Concepts, Presentation prepared by DigSILENT GmbH for the Wind Energy and Development Dialogue 2010, retrieved 27.8.2011 [[http://www.gtz.de/de/dokumente/gtz2010-en-wedd-1-2-WTG-concepts.pdf]]</ref> |
| + | |||
| + | Only fix speed operation possible (stall control required)<br/>• Reactive power compensation required<br/>• No reactive power control capability. Additional devices required:<br/>– TSCs (Thyristor switched capacitors)<br/>– STATCOMs<br/>• Risk of dynamic voltage collapse<br/>GTZ Expert Workshop 2010: Grid and System Integration of Wind Energy, 22/23.11.2010, Berlin/Germany<br/>y g p<br/>– > Typically, wind generators based on induction generators are asked to<br/>disconnect in case of voltage dips<br/> | ||
| − | + | [[Wind Turbine Technology#toc|►Go to Top]] | |
=== Induction Generator with Variable Rotor Resistance<br/> === | === Induction Generator with Variable Rotor Resistance<br/> === | ||
| − | [[File:Induction Generator with Variable Rotor Resistance.jpg|frame|center|180px|Induction Generator with Variable Rotor Resistance.jpg]]<ref>Weigel S., Poeller M. (2010) Wind Turbine Generators (WTGs) Physical Principals and Generator Concepts, Presentation prepared by DigSILENT GmbH for the Wind Energy and Development Dialogue 2010, retrieved 27.8.2011 [[http://www.gtz.de/de/dokumente/gtz2010-en-wedd-1-2-WTG-concepts.pdf]]</ref> | + | [[File:Induction Generator with Variable Rotor Resistance.jpg|frame|center|180px|Induction Generator with Variable Rotor Resistance.jpg]]<ref name="Weigel S., Poeller M. (2010) Wind Turbine Generators (WTGs) Physical Principals and Generator Concepts, Presentation prepared by DigSILENT GmbH for the Wind Energy and Development Dialogue 2010, retrieved 27.8.2011 [[http://www.gtz.de/de/dokumente/gtz2010-en-wedd-1-2-WTG-concepts.pdf]]">Weigel S., Poeller M. (2010) Wind Turbine Generators (WTGs) Physical Principals and Generator Concepts, Presentation prepared by DigSILENT GmbH for the Wind Energy and Development Dialogue 2010, retrieved 27.8.2011 [[http://www.gtz.de/de/dokumente/gtz2010-en-wedd-1-2-WTG-concepts.pdf]]</ref> |
Simple concept for variable speed operation.<br/>• Reactive power compensation required.<br/>• No reactive power control capability. Additional devices required:<br/>– TSCs (Thyristor switched capacitors)<br/>– STATCOMs<br/>• Limited LVRT capability. Dynamic voltage collapse problems have to<br/>GTZ Expert Workshop 2010: Grid and System Integration of Wind Energy, 22/23.11.2010, Berlin/Germany<br/>be mitigated by:<br/>– Fast increase of rotor resistance during faults<br/>– Additional reactive power compensation devices (typically TSCs) | Simple concept for variable speed operation.<br/>• Reactive power compensation required.<br/>• No reactive power control capability. Additional devices required:<br/>– TSCs (Thyristor switched capacitors)<br/>– STATCOMs<br/>• Limited LVRT capability. Dynamic voltage collapse problems have to<br/>GTZ Expert Workshop 2010: Grid and System Integration of Wind Energy, 22/23.11.2010, Berlin/Germany<br/>be mitigated by:<br/>– Fast increase of rotor resistance during faults<br/>– Additional reactive power compensation devices (typically TSCs) | ||
| − | + | [[Wind Turbine Technology#toc|►Go to Top]] | |
=== Doubly-Fed Induction Generator<br/> === | === Doubly-Fed Induction Generator<br/> === | ||
| − | [[File:Doubly-fed induction generator.jpg|frame|center|180px|Doubly-fed induction generator.jpg]]<ref>Weigel S., Poeller M. (2010) Wind Turbine Generators (WTGs) Physical Principals and Generator Concepts, Presentation prepared by DigSILENT GmbH for the Wind Energy and Development Dialogue 2010, retrieved 27.8.2011 [[http://www.gtz.de/de/dokumente/gtz2010-en-wedd-1-2-WTG-concepts.pdf]]</ref>[[File:Doubly fed induction generatorf Power flow over- and subsyncronous speed.jpg|frame|center|180px|Doubly fed induction generatorf Power flow over- and subsyncronous speed.jpg]]<ref>Weigel S., Poeller M. (2010) Wind Turbine Generators (WTGs) Physical Principals and Generator Concepts, Presentation prepared by DigSILENT GmbH for the Wind Energy and Development Dialogue 2010, retrieved 27.8.2011 [[http://www.gtz.de/de/dokumente/gtz2010-en-wedd-1-2-WTG-concepts.pdf]]</ref> | + | [[File:Doubly-fed induction generator.jpg|frame|center|180px|Doubly-fed induction generator.jpg]]<ref name="Weigel S., Poeller M. (2010) Wind Turbine Generators (WTGs) Physical Principals and Generator Concepts, Presentation prepared by DigSILENT GmbH for the Wind Energy and Development Dialogue 2010, retrieved 27.8.2011 [[http://www.gtz.de/de/dokumente/gtz2010-en-wedd-1-2-WTG-concepts.pdf]]">Weigel S., Poeller M. (2010) Wind Turbine Generators (WTGs) Physical Principals and Generator Concepts, Presentation prepared by DigSILENT GmbH for the Wind Energy and Development Dialogue 2010, retrieved 27.8.2011 [[http://www.gtz.de/de/dokumente/gtz2010-en-wedd-1-2-WTG-concepts.pdf]]</ref>[[File:Doubly fed induction generatorf Power flow over- and subsyncronous speed.jpg|frame|center|180px|Doubly fed induction generatorf Power flow over- and subsyncronous speed.jpg]]<ref name="Weigel S., Poeller M. (2010) Wind Turbine Generators (WTGs) Physical Principals and Generator Concepts, Presentation prepared by DigSILENT GmbH for the Wind Energy and Development Dialogue 2010, retrieved 27.8.2011 [[http://www.gtz.de/de/dokumente/gtz2010-en-wedd-1-2-WTG-concepts.pdf]]">Weigel S., Poeller M. (2010) Wind Turbine Generators (WTGs) Physical Principals and Generator Concepts, Presentation prepared by DigSILENT GmbH for the Wind Energy and Development Dialogue 2010, retrieved 27.8.2011 [[http://www.gtz.de/de/dokumente/gtz2010-en-wedd-1-2-WTG-concepts.pdf]]</ref> [[Wind Turbine Technology#toc|►Go to Top]] |
=== Generator with Fully Rated Converter === | === Generator with Fully Rated Converter === | ||
| − | [[File:Generator with Fully Rated Converter Kopie.jpg|frame|center|180px|Generator with Fully Rated Converter Kopie.jpg]]<ref>Weigel S., Poeller M. (2010) Wind Turbine Generators (WTGs) Physical Principals and Generator Concepts, Presentation prepared by DigSILENT GmbH for the Wind Energy and Development Dialogue 2010, retrieved 27.8.2011 [[http://www.gtz.de/de/dokumente/gtz2010-en-wedd-1-2-WTG-concepts.pdf]]</ref> | + | [[File:Generator with Fully Rated Converter Kopie.jpg|frame|center|180px|Generator with Fully Rated Converter Kopie.jpg]]<ref name="Weigel S., Poeller M. (2010) Wind Turbine Generators (WTGs) Physical Principals and Generator Concepts, Presentation prepared by DigSILENT GmbH for the Wind Energy and Development Dialogue 2010, retrieved 27.8.2011 [[http://www.gtz.de/de/dokumente/gtz2010-en-wedd-1-2-WTG-concepts.pdf]]">Weigel S., Poeller M. (2010) Wind Turbine Generators (WTGs) Physical Principals and Generator Concepts, Presentation prepared by DigSILENT GmbH for the Wind Energy and Development Dialogue 2010, retrieved 27.8.2011 [[http://www.gtz.de/de/dokumente/gtz2010-en-wedd-1-2-WTG-concepts.pdf]]</ref> [[Wind Turbine Technology#toc|►Go to Top]] |
=== Generator with Fully Rated Converter and Direct Drive<br/> === | === Generator with Fully Rated Converter and Direct Drive<br/> === | ||
| − | [[File:Generator with Fully Rated Converter and direct drive.jpg|frame|center|180px|Generator with Fully Rated Converter and direct drive.jpg]]<ref>Weigel S., Poeller M. (2010) Wind Turbine Generators (WTGs) Physical Principals and Generator Concepts, Presentation prepared by DigSILENT GmbH for the Wind Energy and Development Dialogue 2010, retrieved 27.8.2011 [[http://www.gtz.de/de/dokumente/gtz2010-en-wedd-1-2-WTG-concepts.pdf]]</ref> | + | [[File:Generator with Fully Rated Converter and direct drive.jpg|frame|center|180px|Generator with Fully Rated Converter and direct drive.jpg]]<ref name="Weigel S., Poeller M. (2010) Wind Turbine Generators (WTGs) Physical Principals and Generator Concepts, Presentation prepared by DigSILENT GmbH for the Wind Energy and Development Dialogue 2010, retrieved 27.8.2011 [[http://www.gtz.de/de/dokumente/gtz2010-en-wedd-1-2-WTG-concepts.pdf]]">Weigel S., Poeller M. (2010) Wind Turbine Generators (WTGs) Physical Principals and Generator Concepts, Presentation prepared by DigSILENT GmbH for the Wind Energy and Development Dialogue 2010, retrieved 27.8.2011 [[http://www.gtz.de/de/dokumente/gtz2010-en-wedd-1-2-WTG-concepts.pdf]]</ref> |
| + | |||
| + | [[Wind Turbine Technology#toc|►Go to Top]] | ||
=== Directly Coupled Synchronous Generator with Variable Gear Box<br/> === | === Directly Coupled Synchronous Generator with Variable Gear Box<br/> === | ||
| − | [[File:Directly Coupled Synchronous Generator with Variable Gear Box.jpg|frame|center|180px|Directly Coupled Synchronous Generator with Variable Gear Box.jpg]]<ref>Weigel S., Poeller M. (2010) Wind Turbine Generators (WTGs) Physical Principals and Generator Concepts, Presentation prepared by DigSILENT GmbH for the Wind Energy and Development Dialogue 2010, retrieved 27.8.2011 [[http://www.gtz.de/de/dokumente/gtz2010-en-wedd-1-2-WTG-concepts.pdf]]</ref> | + | [[File:Directly Coupled Synchronous Generator with Variable Gear Box.jpg|frame|center|180px|Directly Coupled Synchronous Generator with Variable Gear Box.jpg]]<ref name="Weigel S., Poeller M. (2010) Wind Turbine Generators (WTGs) Physical Principals and Generator Concepts, Presentation prepared by DigSILENT GmbH for the Wind Energy and Development Dialogue 2010, retrieved 27.8.2011 [[http://www.gtz.de/de/dokumente/gtz2010-en-wedd-1-2-WTG-concepts.pdf]]">Weigel S., Poeller M. (2010) Wind Turbine Generators (WTGs) Physical Principals and Generator Concepts, Presentation prepared by DigSILENT GmbH for the Wind Energy and Development Dialogue 2010, retrieved 27.8.2011 [[http://www.gtz.de/de/dokumente/gtz2010-en-wedd-1-2-WTG-concepts.pdf]]</ref> |
| + | |||
| + | [[Wind Turbine Technology#toc|►Go to Top]] | ||
| + | |||
| + | == Further Information == | ||
| + | |||
| + | *[[Small-Scale Wind|Small scale wind turbine]]<br/> | ||
| + | *[[Steffturbine - Hydropower Turbine|Steffturbine - Hydropower Turbine]]<br/> | ||
| + | |||
| + | [[Wind Turbine Technology#toc|►Go to Top]] | ||
== References == | == References == | ||
<references /> | <references /> | ||
| − | |||
| − | |||
[[Category:Wind]] | [[Category:Wind]] | ||
Latest revision as of 14:46, 8 October 2014
Overview
A wind turbine is a device that converts kinetic energy from the wind into electrical power[1].The role of wind turbines is to extract energy from wind and convert it to electrical energy. This extraction is subjected to certain limitations represented by Betz’s limit which is the maximum energy possible to convert kinetic energy into mechanical energy without any losses[2].
Basic Theory
An ideal wind turbine has a maximum power coefficient of 16/27.The theoretical limit cannot be exceeded and this caused by the aerodynamic losses due to conversion of angular momentum,tip and drag[3].
Turbine Power output can can be expressed as follows:
P= ½ * ρ* A * v³* Cp
where ρ is density of air, A is the area swept by rotor and v is the velocity of wind.
The extracted power is then converted into electrical power and is defined as:
P=VI
where P is the electrical power in watt
V is the voltage in V
I is the current in A
Betz Theory is the maximum possible Cp=16/27 which means 59% efficiency is the best a conventional wind turbine can do in extracting power from the wind.
Aerodynamics
Aerodynamics of a wind turbine blade
Stall
Wind turbine blade aerodynamics - stall control
Stall Control:
- Passive Stall
- Power of the wind turbine is limited by the aerodynamic characteristics of the turbine.
Active Stall
Power of the wind turbine is limited additionally by decreasing the pitch angle (increasing the inflow angle ).
Pitch
Aerodynamics at a wind turbine blade during control through pitching
Pitch Control:
- Power of the wind turbine is limited by increasing the pitch angle (decreasing the inflow angle α)
Wind Turbine Operation
Operation of Fix Speed Wind Turbine (Passive Stall)
- Start up (with open breaker) if wind speed > cut-in wind speed
- Close breaker
- Operation at constant blade angle over the whole wind speed range
- In case of large wind speeds: Power limited by aerodynamic profile.
Operation of Variable Speed Wind-Turbines
Start up (with open breaker) if wind speed > cut-in wi
Typical power curves of wind turbines.jpg
nd speed
• Close breaker
• Below rated wind-speed
– Maximum power coefficient (Max. Power Tracking)
– Evt: Speed Limitation
• Above rated wind-speed:
– P=Pr
ated (Limited by power electronics converter)
– Pitching
• Advantages of variable speed operation:
– Lower cut-in wind speeds
– Higher efficiency, especially at low wind speeds
– Lower power variations (compared to fixed speed turbines)
• Disadvantage: More expensive!
Generator Concepts
Overview Wind generator concepts.jpg
Fixed Speed Induction Generator
Fixed speed induction generator.jpg
Only fix speed operation possible (stall control required)
• Reactive power compensation required
• No reactive power control capability. Additional devices required:
– TSCs (Thyristor switched capacitors)
– STATCOMs
• Risk of dynamic voltage collapse
GTZ Expert Workshop 2010: Grid and System Integration of Wind Energy, 22/23.11.2010, Berlin/Germany
y g p
– > Typically, wind generators based on induction generators are asked to
disconnect in case of voltage dips
Induction Generator with Variable Rotor Resistance
Induction Generator with Variable Rotor Resistance.jpg
Simple concept for variable speed operation.
• Reactive power compensation required.
• No reactive power control capability. Additional devices required:
– TSCs (Thyristor switched capacitors)
– STATCOMs
• Limited LVRT capability. Dynamic voltage collapse problems have to
GTZ Expert Workshop 2010: Grid and System Integration of Wind Energy, 22/23.11.2010, Berlin/Germany
be mitigated by:
– Fast increase of rotor resistance during faults
– Additional reactive power compensation devices (typically TSCs)
Doubly-Fed Induction Generator
Doubly-fed induction generator.jpg
Doubly fed induction generatorf Power flow over- and subsyncronous speed.jpg
Generator with Fully Rated Converter
Generator with Fully Rated Converter Kopie.jpg
Generator with Fully Rated Converter and Direct Drive
Generator with Fully Rated Converter and direct drive.jpg
Directly Coupled Synchronous Generator with Variable Gear Box
Directly Coupled Synchronous Generator with Variable Gear Box.jpg
Further Information
References
- ↑ http://en.wikipedia.org/wiki/Wind_turbine
- ↑ J. F. Manwell, J. G. McGowan and A. L. Rogers. WIND ENERGY; Theory, Design and Application. United Kingdom : John Wiley & Sons Ltd, 2009
- ↑ DESIGN AND POWER CHARACTERIZATION OF A SMALL WIND TURBINE MODEL IN PARTIAL LOAD REGION by Abdulkarim Abdulrazek
- ↑ 4.00 4.01 4.02 4.03 4.04 4.05 4.06 4.07 4.08 4.09 4.10 4.11 Weigel S., Poeller M. (2010) Wind Turbine Generators (WTGs) Physical Principals and Generator Concepts, Presentation prepared by DigSILENT GmbH for the Wind Energy and Development Dialogue 2010, retrieved 27.8.2011 [[1]]
