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/* Brief History of Wind Energy */
==Working Principle of Wind Turbine ==
Wind is air in motion. It is a form of solar energy. Solar radiation heats every part of the Earth’s surface unevenly due to irregularities and rotation of earth. The flow of wind patterns are modified by the earth's terrain, bodies of water, and vegetative cover. When air moves, causing wind, it has kinetic energy. The kinetic energy of wind can be captured by a wind turbine and converted to other forms of energy such as electricity or mechanical power.
[[Image:windprinciplewindenergy windprinciple1.png|center|550px|thumb|Fig 3 '''[http://www.atlantissolar.com/wind_story.html Wind turbine principle]''']]
Sources:[http://windeis.anl.gov/guide/basics/index.cfm Wind Energy Basics],[http://www1.eere.energy.gov/windandhydro/wind_how.html#inside How Wind Turbines Work]
{|border="2" cellspacing="0" cellpadding="4" width="100%"
| align = "center" bgcolor = "#83caff4F81BD"|<font color="#FFFFFF">'''Horizontal axis wind turbines'''</font>| align = "center" bgcolor = "#83caff4F81BD"|<font color="#FFFFFF">'''Vertical axis wind turbines'''</font>
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* It is mounted on top of a tower ,requires huge towers leads to complex in operation, maintenance and high initial costs.
* It operates only with upstream or down stream wind directions.
* It can be constructed in off-shores.
* It produces large amount of electricity with high efficiency.
* These are easy to build and maintain, safer, easier to transport and they can be mounted close to the ground.
* These can handle much turbulence in wind than horizontal wind turbines.
* It operates with any direction of wind
* Production of electricity is less due to low wind speeds near to ground
|-|[[Image:Horizontal.jpg|center|thumb|Fig 4(a)'''[http://www.windturbinesnow.com/horizontalaxis-windturbines.htm Horizontal axis wind turbine]''']]|[[Image:vertical.jpg|center|thumb|Fig 4(b)'''[http://www.solarpowerwindenergy.org/2009/12/25/types-of-wind-turbines/ Vertical axis wind turbine]''']]|-
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=Horizontal Axis Wind Turbines=
[[Image:HWAT1.PNG|right|131px|thumb|Fig]]
{|border="2" cellspacing="0" cellpadding="4" width="100%"
| align = "center" bgcolor = "#83caff4F81BD"| | align = "center" bgcolor = "#83caff4F81BD"|<font color="#FFFFFF">'''Fixed speed generating systems'''</font>| align = "center" bgcolor = "#83caff4F81BD"|<font color="#FFFFFF">'''Variable speed generating systems'''</font>| align = "center" bgcolor = "#83caff4F81BD"|<font color="#FFFFFF">'''Doubly fed induction generator'''</font>
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|bgcolor = "#DCE6F1"| Machines|bgcolor = "#DCE6F1"| SQIG|bgcolor = "#DCE6F1"| PMSG/WRSG/WRIG|bgcolor = "#DCE6F1"| DFIG
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|bgcolor = "#DCE6F1"| Drawbacks|bgcolor = "#DCE6F1"| <nowiki>* </nowiki>No control on real and reactive power
<nowiki>* Less optimum power extraction capability</nowiki>
<nowiki>* High mechanical stress on turbine mechanical components</nowiki>
|bgcolor = "#DCE6F1"| <nowiki>* Additional cost of power electronics</nowiki>
<nowiki>* Limited fault ride through capability</nowiki>
|bgcolor = "#DCE6F1"| <nowiki>* Regular maintenance of slip ring and gearbox</nowiki>
<nowiki>* Limited fault ride-through capability</nowiki>
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|align = "center" bgcolor = "#83caff4F81BD"|<font color="#FFFFFF">'''Control System'''</font>|align = "center" bgcolor = "#83caff4F81BD"|<font color="#FFFFFF">'''Pitch contol'''</font>|align = "center" bgcolor = "#83caff4F81BD"|<font color="#FFFFFF">'''Yaw control'''</font>|align = "center" bgcolor = "#83caff4F81BD"|<font color="#FFFFFF">'''Stall control'''</font>|align = "center" bgcolor = "#83caff4F81BD"|<font color="#FFFFFF">'''Generator torque control'''</font>
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|rowspan="2" align = "center" bgcolor = "#83caffDCE6F1"|'''Description'''|-valign="top' bgcolor = "#DCE6F1"| A method of controlling the speed of a wind turbine by varying the orientation, or pitch, of the blades, and thereby altering its aerodynamics and efficiency.
Source:[http://www.moog.com/markets/energy/wind-turbines/blade-pitch-control/ Blade Pitch Control]
|bgcolor = "#DCE6F1"| The rotation of horizontal axis wind turbine around its tower to orient the turbine in upwind or down wind direction.
Source:[http://zone.ni.com/devzone/cda/tut/p/id/8189 Wind Turbine Control Methods]
|bgcolor = "#DCE6F1"|Stall control works by increasing the angle at which the relative wind strikes the blades (angle of attack). As the wind speed increases drag force on the blade increase and lift force gets reduces, thus finally reduces the speed of turbine.A fully stalled turbine blade, when stopped, has the flat side of the blade facing directly into the wind. Compare with furling.
Source:[http://www.windmeup.org/2008/03/stall-control-basics.html Stall-control basics]
|bgcolor = "#DCE6F1"|As the aerodynamic torque control changes, rotor speed changes. it changes the output power frequency. A frequency converter is connected in between generator and the network to maintain generator power constant.
Source[[Media:windenergycontrol.pdf|Wind Energy Control]]
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|[[Image:pitch.jpg|thumb|center|175px|Fig 16(a) '''[http://zone.ni.com/devzone/cda/tut/p/id/8189 Pitch control]''']]
|[[Image:Yaw.jpg|thumb|center|175px|Fig 16(b) '''[http://zone.ni.com/devzone/cda/tut/p/id/8189 Yaw control]''']]
|allignalign='"center" | NA|allignalign='"center" | NA
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A majority of patents describing wind turbines or wind energy are classified in the following IPC classifications.
{|border="2" cellspacing="0" cellpadding="4" width="100%"
| align = "center" bgcolor = "#99ccff4F81BD"|<font color="#FFFFFF">'''S.NO'''</font>| align = "center" bgcolor = "#99ccff4F81BD"|<font color="#FFFFFF">'''IPC Classification'''</font>| align = "center" bgcolor = "#99ccff4F81BD"|<font color="#FFFFFF">'''Description'''</font>
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| align = "center" bgcolor = "#99ccffDCE6F1"|1| align = "center" bgcolor = "#DCE6F1"|[http://www.wipo.int/ipcpub/#refresh=page¬ion=scheme&version=20110101&symbol=F03D F03D]| WIND MOTORSbgcolor = "#DCE6F1"| Machines or engines for liquids; wind, spring, or weight motors; producing mechanical power or a reactive propulsive thrust / '''Wind motors'''
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| align = "center" bgcolor = "#99ccff"|2
| align = "center"|[http://www.wipo.int/ipcpub/#refresh=page¬ion=scheme&version=20110101&symbol=F16C F16C]
| SHAFTSEngineering elements or units; FLEXIBLE SHAFTSgeneral measures for producing and maintaining effective functioning of machines or installations; ELEMENTS OF CRANKSHAFT MECHANISMSthermal insulation in general/ '''Shafts; ROTARY BODIES OTHER THAN GEARING ELEMENTSflexible shafts; BEARINGSelements of crankshaft mechanisms; rotary bodies other than gearing elements; bearings'''
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| align = "center" bgcolor = "#99ccffDCE6F1"|3| align = "center" bgcolor = "#DCE6F1"|[http://www.wipo.int/ipcpub/#refresh=page¬ion=scheme&version=20110101&symbol=F16H F16H]| GEARINGbgcolor = "#DCE6F1"| Engineering elements or units; general measures for producing and maintaining effective functioning of machines or installations; thermal insulation in general / '''Gearing'''
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| align = "center" bgcolor = "#99ccff"|4
| align = "center"|[http://www.wipo.int/ipcpub/#refresh=page¬ion=scheme&version=20110101&symbol=F03B F03B]
| MACHINES OR ENGINES FOR LIQUIDS Machines or engines for liquids; wind, spring, or weight motors; producing mechanical power or a reactive propulsive thrust / '''Machines or engines for liquids'''
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|align = "center" bgcolor = "#99ccffDCE6F1"|5|align = "center" bgcolor = "#DCE6F1"|[http://www.wipo.int/ipcpub/#refresh=symbol¬ion=scheme&version=20110101&symbol=H02K H02K]|DYNAMObgcolor = "#DCE6F1"|Generation, conversion, or distribution of electric power / '''Dynamo-ELECTRIC MACHINESelectric machines'''
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| align = "center" bgcolor = "#99ccff"|6
| align = "center"|[http://www.wipo.int/ipcpub/#&refresh=page¬ion=scheme&version=20110101&symbol=H02P H02P]
| CONTROL OR REGULATION OF ELECTRIC MOTORSGeneration, GENERATORSconversion, OR DYNAMOor distribution of electric power / '''Control or regulation of electric motors, generators, or dynamo-ELECTRIC CONVERTERSelectric converters; CONTROLLING TRANSFORMERScontrolling transformers, REACTORS OR CHOKE COILSreactors or choke coils'''
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| align = "center" bgcolor = "#99ccffDCE6F1"|7| align = "center" bgcolor = "#DCE6F1"|[http://www.wipo.int/ipcpub/#refresh=page¬ion=scheme&version=20110101&symbol=H02M H02M]| APPARATUS FOR CONVERSION BETWEEN AC AND ACbgcolor = "#DCE6F1"|Generation, conversion, or distribution of electric power / '''Apparatus for conversion between ac and ac, BETWEEN AC AND DCbetween ac and dc, OR BETWEEN DC AND DCor between dc and dc, AND FOR USE WITH MAINS OR SIMILAR POWER SUPPLY SYSTEMSand for use with mains or similar power supply systems; CONVERSION OF DC OR AC INPUT POWER INTO SURGE OUTPUT POWERconversion of dc or ac input power into surge output power; CONTROL OR REGULATIONcontrol or regulation'''
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| align = "center" bgcolor = "#99ccff"|8
| align = "center"|[http://www.wipo.int/ipcpub/#refresh=page¬ion=scheme&version=20110101&symbol=H02J H02J]
| CIRCUIT ARRANGEMENTS OR SYSTEMS FOR SUPPLYING OR DISTRIBUTING ELECTRIC POWERGeneration, conversion, or distribution of electric power / '''Circuit arrangements or systems for supplying or distributing electric power; SYSTEMS FOR STORING ELECTRIC ENERGYsystems for storing electric energy'''
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| align = "center" bgcolor = "#99ccffDCE6F1"|9| align = "center" bgcolor = "#DCE6F1"|[http://www.wipo.int/ipcpub/#refresh=page¬ion=scheme&version=20110101&symbol=G06F G06F]| ELECTRIC DIGITAL DATA PROCESSINGbgcolor = "#DCE6F1"| Computing; calculating; counting /'''Electric digital data processing'''
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| align = "center" bgcolor = "#99ccff"|10
| align = "center"|[http://www.wipo.int/ipcpub/#refresh=page¬ion=scheme&version=20110101&symbol=G05F G05F]
| SYSTEMS FOR REGULATING ELECTRIC OR MAGNETIC VARIABLESControlling; regulating / '''Systems for regulating electric or magnetic variables'''
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| align = "center" bgcolor = "#99ccffDCE6F1"|11| align = "center" bgcolor = "#DCE6F1"|[http://www.wipo.int/ipcpub/#refresh=page¬ion=scheme&version=20110101&symbol=H02H H02H]| EMERGENCY PROTECTIVE CIRCUIT ARRANGEMENTS bgcolor = "#DCE6F1"| Generation, conversion, or distribution of electric power / '''Emergency protective circuit arrangements'''
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