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Difference between revisions of "Wind Turbine Technology"

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== Wind turbine control concepts<br>  ==
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[[Portal:Wind|► Back to Wind Portal]]
  
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=== Aerodynamics<br>  ===
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= Overview =
  
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[[Image:Wind turbine blade aerodynamics.jpg|frame|center|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>  
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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>.
  
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=== Stall  ===
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<br/>
  
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[[Image:Wind turbine blade aerodynamics - stall control.jpg|frame|center|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>
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== Basic Theory ==
  
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Stall Control:<br>– Passive Stall:<br>Power of the wind turbine is limited by the aerodynamic characteristics<br>of the turbine.<br>– Active stall:<br>Power of the wind turbine is limited additionally by decreasing the pitch<br>angle (increasing the inflow angle ).<br>
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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>.
  
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=== Pitch<br> ===
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[[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/>
  
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[[Image:Wind turbine blade aerodynamics - pitching.jpg|frame|center|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>
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Turbine Power output can can be expressed as follows:
  
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Pitch Control:<br>– Power of the wind turbine is limited by increasing the pitch angle<br>(decreasing the inflow angle <math>\alpha</math>)<br>
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P= ½ * ρ* A * v³* Cp
  
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== Wind turbine operation<br>  ==
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where ρ is density of air, A is the area swept by rotor and v is the velocity of wind.
  
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=== Operation of Fix Speed Wind Turbine (passive stall)<br>  ===
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The extracted power is then converted into electrical power and is defined as:
  
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• Start up (with open breaker) if wind speed &gt; cut-in wind speed<br>• Close breaker<br>• Operation at constant blade angle over the whole wind speed range<br>• In case of large wind speeds: Power limited by aerodynamic profile.<br>
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P=VI
  
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<br>  
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where P is the electrical power in watt<br/>
  
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=== Operation of Variable Speed Wind-Turbines<br> ===
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V is the voltage in V<br/>
  
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Start up (with open breaker) if wind speed &gt; cut-in wi
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I is the current in A
  
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[[Image:Typical power curves of wind turbines.jpg|frame|right|Typical power curves of wind turbines.jpg]]
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<br/>
  
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nd speed<br>• Close breaker<br>  
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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/>
  
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<br>
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[[Wind Turbine Technology#toc|►Go to Top]]
  
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<br>  
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=== Aerodynamics<br/> ===
  
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• Below rated wind-speed<br>– Maximum power coefficient (Max. Power Tracking)<br>  
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[[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]]
  
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<br>
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=== Stall ===
  
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<br>  
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[[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>
  
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– Evt: Speed Limitation<br>• Above rated wind-speed:<br>– P=Pr<br>ated (Limited by power electronics converter)<br>– Pitching
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<u>Stall Control:</u>
 +
*Passive Stall
 +
*Power of the wind turbine is limited by the aerodynamic characteristics of the turbine.
  
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• Advantages of variable speed operation:<br>– Lower cut-in wind speeds<br>– Higher efficiency, especially at low wind speeds<br>– Lower power variations (compared to fixed speed turbines)<br>• Disadvantage: More expensive!<br>  
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<u>Active Stall</u>
  
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<br>
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Power of the wind turbine is limited additionally by decreasing the pitch angle (increasing the inflow angle ).
  
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<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><br>
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[[Wind Turbine Technology#toc|►Go to Top]]
  
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== Generator concepts<br> ==
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=== Pitch<br/> ===
  
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[[Image:Overview Wind generator concepts.jpg|frame|center|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>  
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[[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>
  
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=== Fixed Speed Induction Generator<br> ===
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<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>)
  
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[[Image:Fixed speed induction generator.jpg|frame|center|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>
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[[Wind Turbine Technology#toc|►Go to Top]]
  
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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>– &gt; Typically, wind generators based on induction generators are asked to<br>disconnect in case of voltage dips<br>  
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== Wind Turbine Operation<br/> ==
  
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=== Induction Generator with Variable Rotor Resistance<br> ===
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=== Operation of Fix Speed Wind Turbine (Passive Stall)<br/> ===
  
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[[Image:Induction Generator with Variable Rotor Resistance.jpg|frame|center|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>
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*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.
  
−
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)<br>
+
[[Wind Turbine Technology#toc|►Go to Top]]
  
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=== Doubly-Fed Induction Generator<br> ===
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=== Operation of Variable Speed Wind-Turbines<br/> ===
  
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[[Image:Doubly-fed induction generator.jpg|frame|center|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>[[Image:Doubly fed induction generatorf Power flow over- and subsyncronous speed.jpg|frame|center|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>  
+
Start up (with open breaker) if wind speed > cut-in wi[[File:Typical power curves of wind turbines.jpg|frame|right|180px|Typical power curves of wind turbines.jpg]]nd speed<br/>• Close breaker
  
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=== Generator with Fully Rated Converter  ===
+
<br/>
  
−
[[Image:Generator with Fully Rated Converter Kopie.jpg|frame|center|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>  
+
<br/>
  
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=== Generator with fully rated converter and direct drive  ===
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• Below rated wind-speed<br/>– Maximum power coefficient (Max. Power Tracking)
  
−
<br>  
+
<br/>
  
−
[[Image:Generator with Fully Rated Converter and direct drive.jpg|frame|center|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>  
+
<br/>
  
−
=== Directly Coupled Synchronous Generator with Variable Gear Box<br> ===
+
– Evt: Speed Limitation<br/>• Above rated wind-speed:<br/>– P=Pr<br/>ated (Limited by power electronics converter)<br/>– Pitching
  
−
[[Image:Directly Coupled Synchronous Generator with Variable Gear Box.jpg|frame|center|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>  
+
• Advantages of variable speed operation:<br/>– Lower cut-in wind speeds<br/>– Higher efficiency, especially at low wind speeds<br/>– Lower power variations (compared to fixed speed turbines)<br/>• Disadvantage: More expensive!
 +
 
 +
<br/>
 +
 
 +
<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/> ==
 +
 
 +
[[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/> ===
 +
 
 +
[[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/> ===
 +
 
 +
[[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)
 +
 
 +
[[Wind Turbine Technology#toc|►Go to Top]]
 +
 
 +
=== Doubly-Fed Induction Generator<br/> ===
 +
 
 +
[[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 ===
 +
 
 +
[[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/> ===
 +
 
 +
[[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/> ===
 +
 
 +
[[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 />
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[[Portal:Wind]]
 
  
 
[[Category:Wind]]
 
[[Category:Wind]]

Latest revision as of 14:46, 8 October 2014

► Back to Wind Portal

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].

Power coefficients of different rotors of different designs


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.

►Go to Top

Aerodynamics

Aerodynamics of a wind turbine blade

[4] ►Go to Top

Stall

Wind turbine blade aerodynamics - stall control

[4]

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 ).

►Go to Top

Pitch

Aerodynamics at a wind turbine blade during control through pitching

[4]

Pitch Control:

  • Power of the wind turbine is limited by increasing the pitch angle (decreasing the inflow angle α)

►Go to Top

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.

►Go to Top

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!


[4]

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Generator Concepts

Overview Wind generator concepts.jpg

[4]

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Fixed Speed Induction Generator

Fixed speed induction generator.jpg

[4]

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

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Induction Generator with Variable Rotor Resistance

Induction Generator with Variable Rotor Resistance.jpg

[4]

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)

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Doubly-Fed Induction Generator

Doubly-fed induction generator.jpg

[4]

Doubly fed induction generatorf Power flow over- and subsyncronous speed.jpg

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Generator with Fully Rated Converter

Generator with Fully Rated Converter Kopie.jpg

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Generator with Fully Rated Converter and Direct Drive

Generator with Fully Rated Converter and direct drive.jpg

[4]

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Directly Coupled Synchronous Generator with Variable Gear Box

Directly Coupled Synchronous Generator with Variable Gear Box.jpg

[4]

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Further Information

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References

  1. ↑ http://en.wikipedia.org/wiki/Wind_turbine
  2. ↑ J. F. Manwell, J. G. McGowan and A. L. Rogers. WIND ENERGY; Theory, Design and Application. United Kingdom : John Wiley & Sons Ltd, 2009
  3. ↑ DESIGN AND POWER CHARACTERIZATION OF A SMALL WIND TURBINE MODEL IN PARTIAL LOAD REGION by Abdulkarim Abdulrazek
  4. ↑ 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]]
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