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National Institute of Technology Rourkela

Rourkela-769008, Orissa

WIND AS A RENEWABLE SOURCE OF ENERGY

A project report submitted

in partial fulllment of the

requirements for the degree

of

Bachelor of Technology

In

ElectricalEngineering

B y

Ishan Patnaik(1050203!


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WIND AS A RENEWABLE SOURCE OF ENERGY

A project report submitted

in partial fulllment of the

requirements for

the degree of

Bachelor of Technology

In

ElectricalEngineering

B y

Ishan Patnaik(1050203!

Under the guidance of

PROF. S. RAUTA


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ACKNO!"#$"%"NT

I would like to express my gratitude towards all the people who have cotri!uted their precious

time ad e""ort to help me# $ithout whom it would ot have !ee possi!le "or me to uderstad

ad complete the pro%ect#

I would like to thak &ro" '#Rauta ad &ro"# '#(hosh, )epartmet o" *lectrical *gieerig, my

&ro%ect 'upervisor "or his guidace, support, motivatio ad ecouragemet through out the

period this work was carried out# +is readiess "or cosultatio at all times, his educative

commets, his cocer ad assistace eve with practical thigs have !ee ivalua!le#

$e are grate"ul to )r# #)#'u!udhi, Professor and Head , )ept# o" *lectrical *gieerig "or

providig ecessary "acilities i the departmet#

)ate ../0/09 I'+12 &1321I4 5.0008


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National Institute of Technology RourkelaRourkela-769008, Orissa

C"RTIFICAT"

3his is to certi"y that the &ro%ect etitled &IN# AS A R"N"A'!" SOURC" OF

"N"R$() su!mitted !y Ishan Patnaik has i partial "ul"illmet o" the reuiremets "or the

award o" 'achelor of Technology #egree i "lectrical "ngineering at National Institute of

Technology* Rourkela 5)eemed :iversity is a authetic work carried out !y him uder my

supervisio ad guidace#

&lace 2I3 Rourkela 5&ro"# '#Rauta)ate )epartmet o" *lectrical *gieerig

2I3 Rourkela


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1;42O$


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;hapter (eerator .-.7

#. 'ychroous (eerator

# 1sychroous (eerator

# 'uirrel ;age Iductio (eerator

#@ )ou!ly >ed Iductio (eerator

# &riciple o" a )ou!le >ed Iductio (eerator coected

to a wid tur!ie

;hapter @ &ower *lectroics 1pplicatios I $id *ergy ;oversio 'ystem .8-

@#. 'o"t 'tartig with 3hyristors

@# &$= I(3 Recti"ier 1d Iverter

@# $id (eeratio 'ystem )escriptio :sig &$= I(3 ;overters

@#@ '313;O=

;hapter (rid ;oectio Reuiremets -9

#. Reuiremets $id >arm ;oectios to the (rid

# Reactive &ower ;otrol

# &ower ;otrol ad >reuecy Rage

#@ &ower >actor ad Aoltage ;otrol

# Idirect (rid ;oectio o" $id 3ur!ies

#6 (eeratig 1lteratig ;urret 51; at Aaria!le >reuecy

#7 1dvatages o" Idirect (rid ;oectio Aaria!le 'peed

#8 )isadvatages o" Idirect (rid ;oectio

;hapter 6 'ta!ility 1alysis 0-@.

6#. =odels O" $id 3ur!ies

6# ;otrol strategy o" )>I( !ased wid tur!ies


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6# 'teady-'tate Aoltage 'ta!ility 1alysis

6#@ 3rasiet Aoltage 'ta!ility 1alysis

;hapter 7 ;oclusios @-@

Re"ereces @@


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!IST OF FI$UR"S

>ig#.#. +ori?otal axis wid tur!ie

>ig#.# Aertical axis wid tur!ie @

>ig#.# &arts o" a wid tur!ie

>ig#.#@ &ower coe""iciet vs tip speed ratio 7

>ig##. 'ychroous (eerator .@

>ig## ;age Rotor .6

>ig#@#. 1 voltage "ed dou!le &$= coverter wid geeratio system 0

>ig# #. Itercoectio o" the )ou!ly "ed iductio geerator to the grid @

>ig# # Idirect (rid coectio o" wid tur!ies ad the productio 6

o" "ixed "reuecy 1;

>ig# 6#. ;o"iguratio o" I( !ased wid tur!ies ad )>I(

!ased wid tur!ies ad itercoectio o" grid

>ig# 6# 'teady-state euivalet circuit o" dou!ly "ed iductio geerator

>ig# 6# 'teady-state euivalet circuit o" iductio geerator

>ig# 6#@ A';-&$= coverter co"iguratio @

>ig# 6# &-A curves o" wid "arms !ased o di""eret 6

wid tur!ie techology

>ig# 6#6 A-C curve o" wid "arm !ased o I( with o-load compesatio 7

>ig# 6#7 A-C curve o" wid "arm !ased o I( with "ull-load compesatio 8

>ig# 6#8 A-C curve o" )>I( !ased wid "arm 8


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!IST OF TA'!"S

3a!le .#;outries with istalled capacity 5x

3a!le 'tates with strog potetial 5potetial =$ /istalled =$ 5x

3a!le 6#. >ault ;ritical ;learig time o" I( !ased wid "arm 9

3a!le 6# >ault ;ritical ;learig time o" )>I( !ased wid "arm @0


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INTRO#UCTION

Rene+a,le "nergy Sources are those eergy sources which are ot destroyed whe their eergy

is haressed# +uma use o" reewa!le eergy reuires techologies that haress atural

pheomea, such as sulight, wid, waves, water "low, ad !iological processes such as

aaero!ic digestio, !iological hydroge productio ad geothermal heat# 1mogst the a!ove

metioed sources o" eergy there has !ee a lot o" developmet i the techology "or

haressig eergy "rom the wid#

$id is the motio o" air masses produced !y the irregular heatig o" the earthDs sur"ace !y su#

3hese di""ereces coseuetly create "orces that push air masses aroud "or !alacig the

glo!al temperature or, o a much smaller scale, the temperature !etwee lad ad sea or !etwee

moutais#

$id eergy is ot a costat source o" eergy# It varies cotiuously ad gives eergy i

sudde !ursts# 1!out 0E o" the etire eergy is give out i %ust .E o" the operatig time#

$id stregths vary ad thus caot guaratee cotiuous power# It is !est used i the cotext o" a system that has sigi"icat reserve capacity such as hydro, or reserve load, such as a

desaliatio plat, to mitigate the ecoomic e""ects o" resource varia!ility#

3he power extracted "rom the wid ca !e calculated !y the give "ormula

P-./01R 23+

2CP45*67

&w F extracted power "rom the wid,

GF air desity, 5approximately .# kg/m

at 0H

; at sea level

R F !lade radius 5i m, 5it varies !etwee @0-60 m

Aw F wid velocity 5m/s 5velocity ca !e cotrolled !etwee to 0 m/s


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;p F the power coe""iciet which is a "uctio o" !oth tip speed ratio 5, ad !lade pitch agle,

5J5deg#

&ower coe""iciet 5;p is de"ied as the ratio o" the output power produced to the power

availa!le i the wid#

'et8 !i9it:

2o wid tur!ie could covert more tha /;.2< o" the kietic eergy o" the wid ito

mechaical eergy turig a rotor# 3his is kow as the et?


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Ta,le >.Countries +ith installed ca=acity

India?s %arket O@er@ie+ of ind "nergy

O@er@ie+

Idia has a vast supply o" reewa!le eergy resources# Idia has oe o" the worldDs largest

programs "or deploymet o" reewa!le eergy products ad systems ,700 =$ "rom reewa!le

eergy sources istalled#

Ta,le States +ith strong =otential: 4=otential % Binstalled %7


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The Proect

3he pro%ects are to istall two 0#8 =$ wid tur!ie i 4arataka, Idia# 3hese will geerate

reewa!le electricity, to displace "ossil "uel powered electricity "rom the grid# *ach tur!ie will

geerate eough electricity each year to power the euivalet o" 0 homes i the :4 K savig

.,00 toes o" ;O each per year#


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A'STRACT

3his report descri!es a!out he wid power ad its potetial that ca !e haressed i the "uture to

meet the curret eergy demad# $ith detailed descriptio o" the wid tur!ie ad the wid

geerator "ocus has !ee give o the itercoectio o" the geerators with the grid ad the

pro!lems associated with it# 3he use o" power electroics i the circuitry ad their applicatios

have also !ee emphasi?ed# I the ed a voltage sta!ility aalysis has !ee doe with respect to

various models o" the wid tur!ies to "id the !est way to clear "aults ad have optimum output#


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;+1&3*R .

IN# TUR'IN"S


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1 +ind tur,ine is a rotatig machie which coverts the kietic eergy i wid ito mechaical

eergy# I" the mechaical eergy is the coverted to electricity, the machie is called a +ind

generator, +ind tur,ine, +ind =o+er unit 4PU7, +ind energy con@erter 4"C7, or aeroD

generator#

$id tur!ies ca !e separated ito two types !ased !y the axis i which the tur!ie rotates#

3ur!ies that rotate aroud a hori?otal axis are more commo# Aertical-axis tur!ies are less

"reuetly used#

EORIONTA! AGIS IN# TUR'IN"S

Fig.>.> Eori8ontal aHis +ind tur,ine

+ori?otal-axis wid tur!ies 5+1$3 have the mai rotor sha"t ad electrical geerator at the

top o" a tower, ad must !e poited ito the wid# =ost have a gear!ox, which turs the slow

rotatio o" the !lades ito a uicker rotatio that is more suita!le to drive a electrical geerator#

'ice a tower produces tur!ulece !ehid it, the tur!ie is usually poited upwid o" the tower#

3ur!ie !lades are made sti"" to prevet the !lades "rom !eig pushed ito the tower !y high

wids# 1dditioally, the !lades are placed a cosidera!le distace i "rot o" the tower ad are

sometimes tilted up a small amout#

)owwid machies have !ee !uilt, despite the pro!lem o" tur!ulece, !ecause they doMt eed

a additioal mechaism "or keepig them i lie with the wid, ad !ecause i high wids the


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!lades ca !e allowed to !ed which reduces their swept area ad thus their wid resistace#

'ice cyclic 5that is repetitive tur!ulece may lead to "atigue "ailures most +1$3s are upwid

machies#

EAT ad@antages

N Aaria!le !lade pitch, which gives the tur!ie !lades the optimum agle o" attack#

1llowig the agle o" attack to !e remotely ad%usted gives greater cotrol, so the tur!ie

collects the maximum amout o" wid eergy "or the time o" day ad seaso#

N 3he tall tower !ase allows access to stroger wid i sites with wid shear# I some wid

shear sites, every te meters up, the wid speed ca icrease !y 0E ad the power

output !y @E#

N +igh e""iciecy, sice the !lades always move perpedicularly to the wid, receivig

power through the whole rotatio# I cotrast, all vertical axis wid tur!ies, ad most

proposed air!ore wid tur!ie desigs, ivolve various types o" reciprocatig actios,

reuirig air"oil sur"aces to !acktrack agaist the wid "or part o" the cycle# acktrackig

agaist the wid leads to iheretly lower e""iciecy#

EAT disad@antages

N 3he tall towers ad !lades up to 90 meters log are di""icult to trasport# 3rasportatio

ca ow cost 0E o" euipmet costs#

N 3all +1$3s are di""icult to istall, eedig very tall ad expesive craes ad skilled

operators#

N =assive tower costructio is reuired to support the heavy !lades, gear!ox, ad

geerator#N Re"lectios "rom tall +1$3s may a""ect side lo!es o" radar istallatios creatig sigal

clutter, although "ilterig ca suppress it#

N )owwid variats su""er "rom "atigue ad structural "ailure caused !y tur!ulece whe

a !lade passes through the towerMs wid shadow 5"or this reaso, the ma%ority o" +1$3s

use a upwid desig, with the rotor "acig the wid i "rot o" the tower#

N +1$3s reuire a additioal yaw cotrol mechaism to tur the !lades toward the wid#


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3ertical aHis ind Tur,ines

Fig.>. 3ertical aHis +ind tur,ine

3erticalDaHis +ind tur,ines 5or A1$3s have the mai rotor sha"t arraged vertically# 4ey

advatages o" this arragemet are that the tur!ie does ot eed to !e poited ito the wid to

!e e""ective# 3his is a advatage o sites where the wid directio is highly varia!le# A1$3s

ca utili?e wids "rom varyig directios#

$ith a vertical axis, the geerator ad gear!ox ca !e placed ear the groud, so the tower

doesMt eed to support it, ad it is more accessi!le "or maiteace# )raw!acks are that some

desigs produce pulsatig torue# )rag may !e created whe the !lade rotates ito the wid#

3AT ad@antages

N 1 massive tower structure is less "reuetly used, as A1$3s are more "reuetly

mouted with the lower !earig mouted ear the groud#

N )esigs without yaw mechaisms are possi!le with "ixed pitch rotor desigs#

N 1 A1$3 ca !e located earer the groud, makig it easier to maitai the movig

parts#

N A1$3s have lower wid startup speeds tha +1$3s# 3ypically, they start creatig

electricity at 6 =#+# 5.0 km/h#

N A1$3s may have a lower oise sigature#


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3AT disad@antages

N

=ost A1$3s produce eergy at oly 0E o" the e""iciecy o" +1$3s i large part

!ecause o" the additioal drag that they have as their !lades rotate ito the wid#

N $hile A1$3sM parts are located o the groud, they are also located uder the weight o"

the structure a!ove it, which ca make chagig out parts early impossi!le without

dismatlig the structure i" ot desiged properly#

N +avig rotors located close to the groud where wid speeds are lower due to wid shear,

A1$3s may ot produce as much eergy at a give site as a +1$3 with the same

"ootprit or height#

N ecause A1$3s are ot commoly deployed due maily to the serious disadvatages

metioed a!ove, they appear ovel to those ot "amiliar with the wid idustry# 3his has

o"te made them the su!%ect o" wild claims ad ivestmet scams over the last 0 years#

ind Tur,ine $lossary

Fig.>.2 Parts of a +ind tur,ine

Ane9o9eter: =easures the wid speed ad trasmits wid speed data to the cotroller#


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'lades: =ost tur!ies have either two or three !lades# $id !lowig over the !lades causes the

!lades to li"t ad rotate#

'rake: 1 disc !rake which ca !e applied mechaically, electrically, or hydraulically to stop the

rotor i emergecies#

Controller: 3he cotroller starts up the machie at wid speeds o" a!out 8 to .6 miles per hour

5mph ad shuts o"" the machie at a!out 6 mph# 3ur!ies caot operate at wid speeds a!ove

a!out 6 mph !ecause their geerators could overheat#

$ear ,oH: (ears coect the low-speed sha"t to the high-speed sha"t ad icrease the rotatioal

speeds "rom a!out 0 to 60 rotatios per miute 5rpm to a!out .00 to .00 rpm, the rotatioal

speed reuired !y most geerators to produce electricity# 3he gear !ox is a costly 5ad heavy

part o" the wid tur!ie ad egieers are explorig direct-drive geerators that operate at

lower rotatioal speeds ad doMt eed gear !oxes#

$enerator: :sually a o""-the-shel" iductio geerator that produces 60-cycle 1; electricity#

EighDs=eed shaft: )rives the geerator#


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To+er: 3owers are made "rom tu!ular steel 5show here or steel lattice# ecause wid speed

icreases with height, taller towers ea!le tur!ies to capture more eergy ad geerate more

electricity#

ind direction: 3his is a upwid tur!ie, so-called !ecause it operates "acig ito the wid#

Other tur!ies are desiged to ru dowwid, "acig away "rom the wid#

ind @ane: =easures wid directio ad commuicates with the yaw drive to oriet the tur!ie

properly with respect to the wid#

(a+ dri@e: :pwid tur!ies "ace ito the widP the yaw drive is used to keep the rotor "acig

ito the wid as the wid directio chages# )owwid tur!ies doMt reuire a yaw drive, the

wid !lows the rotor dowwid#

(a+ 9otor: &owers the yaw drive#

3he "ollowig is a graph !etwee &ower ;oe""iciet 5;& vs 3ip 'peed Ratio 5

Fig.>. Po+er coefficient @s ti= s=eed ratio


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$id tur!ies typically have two degrees o" "reedom to optimi?e power geeratio#

.# The ability to change their yaw or compass orientation !y turig 5usig motors the

etire acelle uit so the rotor is poited directly ito the wid#

3his process is cotrolled !y wid directio i"ormatio "rom ear!y wid vaes which

are located to miimi?e the e""ect due to wake tur!ulece "rom the wid tur!ies#

# The pitch of the blades which ca !e chaged to keep a ear-costat rotatio rate uder

varyig wid speeds, where the rotatio rate is chose to optimi?e the power-geeratio

e""iciecy o" the tur!ie# 1other purpose o" !oth the !lade pitch cotrol ad yaw

=echaisms is to act as a !rake uder extremely strog wid coditio#

CutD in s=eed: 3he lowest wid speed at which a wid tur!ie !egis producig usa!le

power is called cut-i speed# It is a!out 29Bs#

CutDout s=eed: 3he highest wid speed at which a wid tur!ie stops producig power

is called cut-out speed# It is a!out 2.9Bs#


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;+1&3*R

CONTRO!!"RS


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Po+er control

1 wid tur!ie is desiged to produce a maximum o" power at wide spectrum o" wid speeds#

3he wid tur!ies have three modes o" operatio

N elow rated wid speed operatio

N 1roud rated wid speed operatio

N 1!ove rated wid speed operatio

I" the rated wid speed is exceeded the power has to !e limited# 3here are various ways to

achieve this#

Stall

'tallig works !y icreasig the agle at which the relative wid strikes the !lades 5agle o"

attack, ad it reduces the iduced drag 5drag associated with li"t# 'tallig is simple !ecause it

ca !e made to happe passively 5it icreases automatically whe the wids speed up, !ut it

icreases the cross-sectio o" the !lade "ace-o to the wid, ad thus the ordiary drag# 1 "ully

stalled tur!ie !lade, whe stopped, has the "lat side o" the !lade "acig directly ito the wid#

1 "ixed-speed +1$3 iheretly icreases its agle o" attack at higher wid speed as the !lades

speed up# 1 atural strategy, the, is to allow the !lade to stall whe the wid speed icreases#

3his techiue was success"ully used o may early +1$3s# +owever, o some o" these !lade

sets, it was o!served that the degree o" !lade pitch teded to icrease audi!le oise levels#

Pitch control

>urlig works !y decreasig the agle o" attack, which reduces the iduced drag "rom the li"t o"

the rotor, as well as the cross-sectio# Oe ma%or pro!lem i desigig wid tur!ies is gettig

the !lades to stall or "url uickly eough should a gust o" wid cause sudde acceleratio# 1

"ully "urled tur!ie !lade, whe stopped, has the edge o" the !lade "acig ito the wid#

'tadard moder tur!ies all pitch the !lades i high wids# 'ice pitchig reuires actig

agaist the torue o the !lade, it reuires some "orm o" pitch agle cotrol# =ay tur!ies use


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hydraulic systems# 3hese systems are usually sprig loaded, so that i" hydraulic power "ails, the

!lades automatically "url# Other tur!ies use a electric servomotor "or every rotor !lade# 3hey

have a small !attery-reserve i case o" a electric-grid !reakdow# 'mall wid tur!ies 5uder

0 k$ with varia!le-pitchig geerally use systems operated !y cetri"ugal "orce, either !y

"lyweights or geometric desig, ad employ o electric or hydraulic cotrols#

Other controls

(a+ing

=oder large wid tur!ies are typically actively cotrolled to "ace the wid directio measured

!y a wid vae situated o the !ack o" the acelle# y miimi?ig the yaw agle 5the

misaligmet !etwee wid ad tur!ie poitig directio, the power output is maximi?ed ad

o-symmetrical loads miimi?ed# +owever, sice the wid directio varies uickly the tur!ie

will ot strictly "ollow the directio ad will have a small yaw agle o average# 3he power

output losses ca simpli"ied !e approximated to "all with cos5yaw agle#

"lectrical ,raking

rakig o" a small wid tur!ie ca also !e doe !y dumpig eergy "rom the geerator ito a

resistor !ak, covertig the kietic eergy o" the tur!ie rotatio ito heat# 3his method is

use"ul i" the kietic load o the geerator is suddely reduced or is too small to keep the tur!ie

speed withi its allowed limit#

;yclically !rakig causes the !lades to slow dow, which icreases the stallig e""ect, reducig

the e""iciecy o" the !lades# 3his way, the tur!ieMs rotatio ca !e kept at a sa"e speed i "aster

wids while maitaiig 5omial power output# 3his method is usually ot applied o large

grid-coected wid tur!ies#

%echanical ,raking

1 mechaical drum !rake or disk !rake is used to hold the tur!ie at rest "or maiteace# 'uch

!rakes are usually applied oly a"ter !lade "urlig ad electromagetic !rakig have reduced the


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tur!ie speed, as the mechaical !rakes would wear uickly i" used to stop the tur!ie "rom "ull

speed# 3here ca also !e a stick !rake#


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;+1&3*R

$"N"RATOR


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1 geerator is a device which coverts mechaical eergy ito electrical eergy# $id

geerators have traditioally !ee wid tur!ies, i#e# a propeller attached to a electric geerator

attached to appropriate electroics to attach it to the electrical grid#

(eerators ca !e classi"ied !roadly ito two categories

a 'ychroous (eerators

! 1sychroous (eerators

3he !asis o" this categori?atio is the speed at which the geerators are ru# 'ychroous

geerators are ru at sychroous speed 5.00 rpm "or a @ pole machie at 0+? "reuecy

while asychroous geerators ru at a speed more tha the sychroous speed#

S(NCERONOUS $"N"RATOR

'ychroous geerators are dou!ly "ed machies which geerate electricity !y the priciple

whe the magetic "ield aroud a coductor chages, a curret is iduced i the coductor#

3ypically, a rotatig maget called the rotor turs withi a statioary set o" coductors woud i

coils o a iro core, called the stator# 3he "ield cuts across the coductors, geeratig a

electrical curret, as the mechaical iput causes the rotor to tur#

Fig.2.> Synchronous $enerator

3he rotatig magetic "ield iduces a 1; voltage i the stator widigs# O"te there are three

sets o" stator widigs, physically o""set so that the rotatig magetic "ield produces three phase

currets, displaced !y oe-third o" a period with respect to each other#


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3he rotor magetic "ield may !e produced !y iductio !y permaet magets 5i very small

machies, or !y a rotor widig eergi?ed with direct curret through slip rigs ad !rushes#

3he rotor magetic "ield may eve !e provided !y statioary "ield widig, with movig poles i

the rotor# 1utomotive alterators ivaria!ly use a rotor widig, which allows cotrol o" the

alterator geerated voltage !y varyig the curret i the rotor "ield widig# &ermaet maget

machies avoid the loss due to mageti?ig curret i the rotor, !ut are restricted i si?e, owig

to the cost o" the maget material# 'ice the permaet maget "ield is costat, the termial

voltage varies directly with the speed o" the geerator#

AS(NCERONOUS $"N"RATOR

1sychroous geerators or Iductio geerators are sigly excited a#c# machie# Its stator

widig is directly coected to the ac source whereas its rotor widig receives its eergy "rom

stator !y meas o" iductio# alaced currets produce costat amplitude rotatig mm" wave#

3he stator produced mm" ad rotor produced mm" wave, !oth rotate i the air gap i the same

directio at sychroous speed# 3hese two mm" s com!ie to give the resultat air-gap "lux

desity wave o" costat amplitude ad rotatig at sychroous speed# 3his "lux iduces currets

i the rotor ad a electromagetic torue is produced which rotates the rotor#

1sychroous geerators are mostly used as wid tur!ies as they ca !e operated at varia!le

speed ulike sychroous geerator# 3wo kids o" asychroous geerators are used amely

a 'uirrel cage iductio geerator 5';I(

! )ou!ly "ed iductio geerator 5)>I(

SJUIRR"! CA$" IN#UCTION $"N"RATOR

1 suirrel cage rotor is the rotatig part# I overall shape it is a cylider mouted o a sha"t#

Iterally it cotais logitudial coductive !ars 5usually made o" alumium or copper set ito

grooves ad coected together at !oth eds !y shortig rigs "ormig a cage-like shape# 3he

core o" the rotor is !uilt o" a stack o" iro lamiatios#


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1

Fig.2. Cage Rotor

3he "ield widigs i the stator o" a iductio motor set up a rotatig magetic "ield aroud the

rotor# 3he relative motio !etwee this "ield ad the rotatio o" the rotor iduces electric curret

i the coductive !ars# I tur these currets legthwise i the coductors react with the

magetic "ield o" the motor to produce "orce actig at a taget to the rotor, resultig i torue to

tur the sha"t# I e""ect the rotor is carried aroud with the magetic "ield !ut at a slightly slower

rate o" rotatio# 3he di""erece i speed is called slip ad icreases with load#

#OU'!( F"# IN#UCTION $"N"RATOR

#FI$ is )ou!le >ed Iductio (eerator, a geeratig priciple widely used i wid tur!ies# It

is !ased o a iductio geerator with a multiphase woud rotor ad a multiphase sliprig

assem!ly with !rushes "or access to the rotor widigs#

Princi=le of a #ou,le Fed Induction $enerator connected to a +ind tur,ine

3he priciple o" the )>I( is that rotor widigs are coected to the grid via sliprigs ad !ack-

to-!ack voltage source coverter that cotrols !oth the rotor ad the grid currets# 3hus rotor

"reuecy ca "reely di""er "rom the grid "reuecy 50 or 60 +?# y cotrollig the rotor

currets !y the coverter it is possi!le to ad%ust the active ad reactive power "ed to the grid "rom

the stator idepedetly o" the geerators turig speed# 3he cotrol priciple used is either the

two-axis curret vector cotrol or direct torue cotrol 5)3;# )3; has tured out to have !etter

sta!ility tha curret vector cotrol especially whe high reactive currets are reuired "rom the

geerator


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3he dou!ly-"ed geerator rotors are typically woud with "rom to times the um!er o" turs

o" the stator# 3his meas that the rotor voltages will !e higher ad currets respectively lower#

3hus i the typical Q 0 E operatioal speed rage aroud the sychroous speed the rated

curret o" the coverter is accordigly lower leadig to a low cost o" the coverter# 3he

draw!ack is that cotrolled operatio outside the operatioal speed rage is impossi!le !ecause

o" the higher tha rated rotor voltage# >urther, the voltage trasiets due to the grid distur!aces

5three- ad two-phase voltage dips, especially will also !e magi"ied# I order to prevet high

rotor voltages - ad high currets resultig "rom these voltages - "rom destroyig the I(3s ad

diodes o" the coverter a protectio circuit 5called crow!ar is used#

3he crow!ar will short-circuit the rotor widigs through a small resistace whe excessive

currets or voltages are detected# I order to !e a!le to cotiue the operatio as uickly as

possi!le a active crow!ar has to !e used# 3he active crow!ar ca remove the rotor short i a

cotrolled way ad thus the rotor side coverter ca !e started oly a"ter 0-60 ms "rom the start

o" the grid distur!ace# 3hus it is possi!le to geerate reactive curret to the grid durig the rest

o" the voltage dip ad i this way help the grid to recover "rom the "ault#

1s a summary, a dou!ly "ed iductio machie is a woud-rotor dou!ly-"ed electric machie adhas several advatages over a covetioal iductio machie i wid power applicatios#

>irstly, as the rotor circuit is cotrolled !y a power electroics coverter, the iductio geerator

is a!le to !oth import ad export reactive power# 3his has importat coseueces "or power

system sta!ility ad allows the machie to support the grid durig severe voltage distur!aces

5low voltage ride through,


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;+1&3*R @

PO"R "!"CTRONICS

APP!ICATIONS IN

IN# "N"R$( CON3"RSION

S(ST"%


35/60

1

Soft Starting +ith Thyristors

I" you switched a large wid tur!ie o to the grid with a ormal switch, the eigh!ours would

see a !rowout 5!ecause o" the curret reuired to mageti?e the geerator "ollowed !y a power

peak due to the geerator curret surgig ito the grid#

1other upleasat side e""ect o" usig a hard switch would !e to put a lot o" extra wear o the

gear!ox, sice the cut-i o" the geerator would work as i" you all o" a sudde slammed o the

mechaical !rake o" the tur!ie# 3o prevet this situatio, moder wid tur!ies are soft

starting, i#e# they coect ad discoect gradually to the grid usig thyristors, a type o"

semicoductor cotiuous switches which may !e cotrolled electroically# 3hyristors waste

a!out . to per cet o" the eergy ruig through them# =oder wid tur!ies are there"ore

ormally euipped with a so called ,y=ass s+itch, i#e# a mechaical switch which is activated

a"ter the tur!ie has !ee so"t started# I this way the amout o" eergy wasted will !e

miimi?ed#

P% I$'T R"CTIFI"R AN# IN3"RT"R

1 device that coverts dc power ito ac power at desired output voltage ad "reuecy is called

a Iverter#

Aoltage 'ource Iverter is oe i which the dc source has small or egligi!le impedace# I

other words, a voltage source iverter has a sti"" voltage source at its iput termials#

1; loads may reuire costat or ad%usta!le voltage at their iput termials# $he such loads

are "ed !y iverters, it is essetial that output voltage o" the iverters is so cotrolled as to "ul"ill

the reuiremets o" the ac loads#

&$= cotrol is a method to cotrol the output voltage that is widely i applicatio# I this

method, a "ixed dc iput voltage is give to the iverter ad a cotrolled ac output voltage is

o!taied !y ad%ustig the o ad o"" periods o" the iverter compoets#

3he advatages possessed !y &$= techiue are as uder


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i# 3he output voltage cotrol with this method ca !e o!taied without ay additioal

compoets#

ii# $ith this method, lower order harmoics ca !e elimiated or miimi?ed alog with its

output voltage cotrol# 1s the higher order harmoics ca !e "iltered easily, the "ilterig

reuiremets are miimi?ed#

3he insulated gate ,i=olar transistor or I$'T is a three-termial power semicoductor device,

oted "or high e""iciecy ad "ast switchig# 'ice it is desiged to rapidly tur o ad o"",

ampli"iers that use it o"te sythesi?e complex wave"orms with pulse width modulatio ad low-

pass "ilters.

IN# $"N"RATION S(ST"% #"SCRIPTION USIN$ P% I$'T

CON3"RT"RS

Fig..> A @oltage fed dou,le P% con@erter +ind generation syste9

Con@erter Syste9

3he voltage-"ed coverter scheme used i this system is show# 1 vertical 5or hori?otal wid

tur!ie is coupled to the sha"t o" a suirrel cage iductio geerator through a speedup gear ratio


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5ot show# 3he varia!le "reuecy varia!le voltage power "rom the geerator is recti"ied !y a

&$= I(3 5isulated gate !ipolar trasistor recti"ier# 3he recti"ier also supplies the excitatio

eed o" the machie# 3he iverter topology is idetical to that o" the recti"ier, ad it supplies the

geerated power at 60 +? to the utility grid#

STATCO%

1 STATCO% or 'tatic 'ychroous ;ompesator is a regulatig device used o alteratig

curret electricity trasmissio etworks# It is !ased o a power electroics voltage-source

coverter ad ca act as either a source or sik o" reactive 1; power to a electricity etwork# I"

coected to a source o" power it ca also provide active 1; power#

1 STATCO% works !y re!uildig the icomig voltage wave"orm !y switchig !ack ad "orth

"rom reactive to capacitive load# I" it is reactive, it will supply reactive 1; power# I" it is

capacitive, it will a!sor! reactive 1; power# 3his is how it acts as a source/sik#

Uses

:sually a '313;O= is istalled to support electricity etworks that have a poor power "actor

ad o"te poor voltage regulatio# 3here are a um!er o" other uses "or '313;O= devices

icludig, wid eergy voltage sta!ilisatio, ad harmoic "ilterig# +owever, the most commo

use is "or voltage sta!ility#

'ackDtoD,ack @oltage source con@ertor is used i dou!ly "ed iductio geerator which

cotrols the grid ad rotor currets# y cotrollig the rotor currets !y the coverter it is

possi!le to ad%ust the active ad reactive power "ed to the grid "rom the stator idepedetly o"

the geerators turig speed# Rotor circuit is cotrolled !y a power electroics coverter, the

iductio geerator is a!le to !oth import ad export reactive power

'aliet advatages o" the coverter system iclude the "ollowig

N


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N 3he cage type iductio machie is extremely rugged, relia!le, ecoomical, ad

uiversally popular#

N =achie curret is siusoidalLo harmoic copper loss#

N Recti"ier ca geerate programma!le excitatio "or the machie#

N ;otiuous power geeratio "rom ?ero to highest tur!ie speed is possi!le#

N &ower ca "low i either directio permittig the geerator to ru as a motor "or start-up

5reuired "or vertical tur!ie# 'imilarly, regeerative !rakig ca uickly stop the

tur!ie#

N 1utoomous operatio o" the system is possi!le with either a start-up capacitor or with a

!attery o the dc lik#

N *xtremely "ast trasiet respose is possi!le#

N =ultiple geerators or multiple systems ca !e operated i parallel#

N 3he iverter ca !e operated as a A1R/harmoic compesator whe spare capacity is

availa!le#

;osiderig all the a!ove advatages, ad with the preset tred o" decreasig coverter ad

cotrol cost, this type o" coversio system has the potetial to !e uiversally accepted i the"uture# O" course, i recet years, so"t-switched resoat lik ad resoat pole topologies have

!ee proposed, !ut additioal research ad developmet are eeded to !rig them to the

marketplace#


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;+1&3*R 0

$RI# CONN"CTION

R"JUIR"%"NTS


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Fig./.> Interconnection of the #ou,ly fed induction generator to the grid

Reuire9ents ind Far9 Connections to the $rid

I" wid "arms would !e istalled solely to maximi?e eergy output, they would have ma%or

limitatios i terms o"

.# &ower ;otrol ad >reuecy Rage#

# &ower >actor ad Aoltage ;otrol

# 3rasiet >ault ehavior, Aoltage Operatig Rage

3hese are the three mai issues that ew grid codes must address "or wid "arm coectio# 3he

most worryig pro!lem that wid "arms must "ace is a voltage dip i the grid# 3he e""ects o"

trasiet "aults may propagate over very large geographical areas ad the discoectio o" wid

"arms uder "ault coditios could pose a serious threat to etwork security ad security o"

supply !ecause a great amout o" wid power could !e discoected simultaeously#

Reacti@e Po+er Control

Aoltage ad curret are typically measured .8 times per alteratig curret cycle, 5i#e# 0 x .8

times per secod or 60 x .8 times per secod, depedig o the electrical grid "reuecy# O

this !asis, a so called )'& processor calculates the sta!ility o" the grid "reuecy ad the active


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2

ad reactive power o" the tur!ie# 53he reactive power compoet is !asically a uestio o"

whether the voltage ad the curret are i phase or ot#

3he term power uality re"ers to the voltage sta!ility, "reuecy sta!ility, ad the a!sece o"

various "orms o" electrical oise 5e#g# "licker or harmoic distortio o the electrical grid# =ore

!roadly speakig, power compaies 5ad their customers pre"er a alteratig curret with a

ice siusoidal shape#

Po+er Control and Freuency Range

It must !e possi!le to limit the active power output "rom every operatig poit as a percetage o"

the omial power# >or power reductio a ramp rate o" at least .0E o" omial power per

miute must !e possi!le# I" power is ramped dow, this must ot imply discoectio o" sigle

tur!ies "rom the grid# I the wake o" loss o" grid voltage, power has to !e ramped up with a

gradiet o" ot more tha .0E o" omial power per miute# 3his ramp ca !e reali?ed i steps

5recoectio o" sigle wid tur!ies, i" the step si?e does ot exceed .0E o" omial power

per miute# 3he "reuecy rage wid tur!ies have to tolerate is a!out @7#-.# +?# 1ccordig

to the reuiremets o" (erma trasmissio grid operators, large wid "arms have to !e treated

i the "uture like covetioal power plats#

Po+er Factor and 3oltage Control

It has to !e possi!le to operate wid "arms with omial power o" less tha .00 =$ with power

"actor !etwee 0#9 laggig ad 0#9 leadig# 3he reuired power "actor values are always

applied at the grid coectio poit# $id "arms rated .00 =$ or more have to !e a!le to

operate at power "actor !etwee 0#9 laggig ad 0#9 leadig# 3he power "actor rage is

however limited depedig o the grid voltage to avoid leadig power


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Indirect $rid Connection of ind Tur,ines

Fig. /. Indirect $rid connection of +ind tur,ines and the =roduction of fiHed freuency AC

$enerating Alternating Current 4AC7 at 3aria,le FreKuency

=ost wid tur!ies ru at almost costat speed with direct grid coectio# $ith idirect grid

coectio, however, the wid tur!ie geerator rus i its ow, separate mii 1;-grid, as

illustrated i the graphic# 3his grid is cotrolled electroically 5usig a iverter, so that the

"reuecy o" the alteratig curret i the stator o" the geerator may !e varied# I this way it is

possi!le to ru the tur!ie at varia!le rotatioal speed# 3hus the tur!ie will geerate alteratig

curret at exactly the varia!le "reuecy applied to the stator#

3he geerator may !e either a sychroous geerator or a asychroous geerator, ad the

tur!ie may have a gear!ox, as i the image a!ove, or ru without a gear!ox i" the geerator has

may poles#

Con@ersion to #irect Current 4#C7

1; curret with a varia!le "reuecy caot !e hadled !y the pu!lic electrical grid# $e

there"ore start !y recti"yig it# 3he coversio "rom varia!le "reuecy 1; to ); ca !e doe

usig thyristors or large power trasistors#


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Con@ersion to FiHed Freuency AC

$e the covert the 5"luctuatig direct curret to a alteratig curret 5usig a iverter with

exactly the same "reuecy as the pu!lic electrical grid# 3his coversio to 1; i the iverter

ca also !e doe usig either thyristors or trasistors#

Filtering the AC

3he rectagular shaped waves ca !e smoothed out, however, usig appropriate iductaces adcapacitors, i a so-called 1; "ilter mechaism# 3he somewhat %agged appearace o" the voltage

does ot disappear completely#

Ad@antages of Indirect $rid Connection: 3aria,le S=eed

3he advatage o" idirect grid coectio is that it is possi!le to ru the wid tur!ie at varia!le

speed# 3he primary advatage is that gusts o" wid ca !e allowed to make the rotor tur "aster,

thus storig part o" the excess eergy as rotatioal eergy util the gust is over# O!viously, this

reuires a itelliget cotrol strategy, sice we have to !e a!le to di""eretiate !etwee gusts

ad higher wid speed i geeral# 3hus it is possi!le to reduce the peak torue 5reducig wear o

the gear!ox ad geerator, ad we may also reduce the "atigue loads o the tower ad rotor

!lades#

3he secodary advatage is that with power electroics oe may cotrol reactive power 5i#e# the

phase shi"tig o" curret relative to voltage i the 1; grid, so as to improve the power uality i

the electrical grid# 3his may !e use"ul, particularly i" a tur!ie is ruig o a weak electrical

grid#

3heoretically, varia!le speed may also give a slight advatage i terms o" aual productio,

sice it is possi!le to ru the machie at a optimal rotatioal speed, depedig o the wid

speed# >rom a ecoomic poit o" view that advatage is so small, however, that it is hardly

worth metioig#


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#isad@antages of Indirect $rid Connection

3he !asic disadvatage o" idirect grid coectio is cost# 1s we %ust leared, the tur!ie will

eed a recti"ier ad two iverters, oe to cotrol the stator curret, ad aother to geerate the

output curret# &resetly, it seems that the cost o" power electroics exceeds the gais to !e made

i !uildig lighter tur!ies, !ut that may chage as the cost o" power electroics decreases#


45/60

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wid geeratio systems# Aery recetly, a dou!le sided pulse width modulated 5&$= coverter

system has !ee proposed to overcome some o" the a!ove pro!lems# 3his descri!es a A'$3

system with a suirrel cage iductio geerator ad a dou!le-sided &$= coverter where "u??y

logic cotrol has !ee used extesively to maximi?e the power output ad ehace system

per"ormace# 1ll the cotrol algorithms have !ee validated !y simulatio study ad system

per"ormace has !ee evaluated i detail# 1 experimetal study with a #-k$-la!oratory drive

system is i progress# It will evetually !e trasitioed ito a 00-k$ prototype geeratio

system#


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;+1&3*R 6

STA'I!IT( ANA!(SIS


47/60

3

$id power peetratio will icrease rapidly !ecause o" the a!udat wid resources i various

areas ad the govermet policy impetus# +owever, the power system security ad sta!ility may

!e a""ected due to the higher wid power peetratio# ecause ma%ority o" the wid "arms with

higher istalled capacity iteds to !e coected ito the trasmissio etwork o" 0kA voltage

level, their impacts are !ecomig more widespread# I the grid impact studies o" wid power

itegratio, voltage sta!ility is the mostly cocered pro!lem that will a""ect the operatio ad

security o" wid "arms ad power grid#

I the grid impact studies o" wid power itegratio, the voltage sta!ility issue is a key pro!lem

!ecause a large proportio o" wid "arms are !ased o "ixed speed wid tur!ies euipped with

simple induction generator 4I$7. Iductio geerators cosume reactive power ad !ehave

similar to iductio motors i the duratio o" system cotigecy, which will deteriorate the

local grid voltage sta!ility# 1lso varia!le speed wid tur!ies euipped with dou,ly fed

induction generator 4#FI$7 are !ecomig more widely used "or its advaced reactive power

ad voltage cotrol capa!ility# )>I( make use o" power electroic coverters ad are thus a!le

to regulate their ow reactive power, so as to operate at a give power "actor, or to cotrol grid

voltageP ut !ecause o" the limited capacity o" the &$= coverter, the voltage cotrol capa!ility

o" )>I( caMt catch up with that o" the sychroous geerator# $he the voltage cotrol

reuiremet is !eyod the capa!ility o" the )>I(, the voltage sta!ility o" the grid is also

a""ected#

%O#"!S OF IN# TUR'IN"S

$id tur!ies model !ased o di""eret geerator techologies such as simple iductio

geerator or dou!ly "ed iductio geerator with idetical rated power 5.#=$ are preseted#

1s i >igure ., a simple co"iguratio o" di""eret types o" wid tur!ies cocept is show#


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#ou,ly fed induction generator 9odel

3he )>I( is a woud-rotor iductio geerator whose stator is directly coected to the grid, !ut

the three phase rotor widigs are coected through slip rigs to the grid via a partially rated

power electroics coverter# 1 typical co"iguratio o" a )>I( is show

Fig. L.> Configuration of I$ ,ased +ind tur,ines and #FI$ ,ased +ind tur,ines and interconnection of grid

3he )>I( ca !e regarded as a traditioal iductio geerator with a o?ero rotor voltage#

>or represetatio o" )>I( models i power system sta!ility studies, the stator "lux trasiets

are eglected i the voltage relatios#

3he power coverter i such wid tur!ies oly deals with slip power, there"ore the coverter

ratig ca !e kept "airly low, approximately 0E o" the total geerator power# 3he &$=

coverter iserted i the rotor circuit allows "or a "lexi!le ad "ast cotrol o" the geerator !y

modi"yig magitude ad phase agle o" the rotor voltage# 3he cotrolla!ility o" reactive power

help )>I( euipped wid tur!ies play a similar role to that o" sychroous geerators# :der

steady-state coditios, the "lux trasietMs items disappear#


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Fig. L. SteadyDstate eui@alent circuit of dou,ly fed induction generator

)urig ormal steady-state operatio the wid tur!ies or the wid "arm ca !e cosidered as a

&C ode or a &A ode depedig o the cotrol strategy that the wid "arm adopted #

'. Induction generator 9odel

3he rotor o" iductio geerator is a woud-rotor or a suirrel-cage rotor with a short circuit

widig ot coectig to a exteral voltage source# 3he steady-state euivalet circuit o" the

iductio geerator is give i >igure #

Fig. L.2 SteadyDstate eui@alent circuit of induction generator


50/60

3

>rom the euivalet circuit o" iductio geerator i >igure , the active power ad reactive

power expressio are easily derived#

C. Con@erter 9odel

3he coverter cosists o" two voltage source coverters coected !ack-to-!ack ad ea!les

varia!le speed operatio o" the wid tur!ies !y decouplig cotrol that cotrols the active

power ad reactive power o" the geerator separately# 3he rotor-side ad grid-side coverters are

usually set-up !y six-pulse !ridges illustrated i "igure @#

Fig. L. 3SCDP% con@erter configuration

Control strategy of #FI$ ,ased +ind tur,ines

)>I( make use o" power electroic coverters ad are thus a!le to regulate their ow reactive

power, so as to operate at a give power "actor, or to cotrol grid voltage# 3he rotor-side

coverter is cotrolled !y a two stage cotroller# 3he "irst stage cosists o" "ast curret


51/60

3

cotrollers regulatig the geerator rotor currets to re"erece values that are speci"ied !y a

slower power-cotroller which is the secod stage cotroller# 3here are two idepedet &I

cotrollers, oe "or the d-axis compoet, ad oe "or the -axis compoet# 3he output o" the

curret cotroller de"ies the pulse-width modulatio "actor &m i stator voltage orietatio#

Aoltage cotrol ca also !e reali?ed !y replacig the reactive power cotroller !y a voltage

cotroller de"iig the d-axis curret re"erece# :p to ow, this "eature o" the )>I( !ased wid

tur!ie is maily used to keep the geerator reactive power eutral# +owever, as wid power

peetratio i power systems is icreasig, it will pro!a!ly !e desira!le "or wid tur!ies to

provide voltage cotrol# 3he cotroller ca regulate either the voltage or the power "actor, !ut the

maximum possi!le reactive power productio is de"ied !y the coverter ratigs#

ST"A#(DSTAT" 3O!TA$" STA'I!IT( ANA!(SIS

I this sectio, the steady-state voltage sta!ility limit o" wid "arms !ased o di""eret wid

tur!ie techologies is assessed# 3hree cases are coducted case 5. wid tur!ies euipped

with o-load compesated iductio geeratorP case 5 wid tur!ies euipped with "ull-load

compesated iductio geeratorP case 5 wid tur!ies euipped with )>I( cotrollig the

&OI as a &C ode with C F O=Aar#

A. PD3 cur@e analysis of +indDfar9 +ith different generator

$id "arms !ased o di""eret types o" wid tur!ies are itercoected ito the trasmissio

grid# $he the active power output o" wid "arm is low, the &OI voltage does ot a""ected

sigi"icatly !ut whe wid power i%ects ito the &OI icreasig largely the the voltage

decreases "ast# 3he &-A curves o" the wid "arms as wid "arm active power output icreasig

are plotted i >igure 7#


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D

Fig. L./ PD3 cur@es of +ind far9s ,ased on different +ind tur,ine technology

It ca !e that the steady-state voltage sta!ility limits o" iductio geerator !ased wid "arm with

o-load compesatio is oly .=$# $he more real wid power i%ects ito the &OI tha

.=$, the voltage will collapse# $he the )>I( !ased wid "arm with costat power "actor

cotrol that cotrol the &OI as a &C !us with CF 0 =$, the steady-state voltage sta!ility limits

are icreased largely to @@=$# $he 0=$ real wid power i%ects ito the grid, the

voltage sta!ility margi ca !e accepta!le# It must !e oted that iductio geerator !ased wid

"arm with "ull-load compesatio ca ehace the voltage sta!ility limit, !ut ot very o!viouslyP

the "ull-load shut capacitor compesatio should ot !e put ito use i low wid power output

totally or else that will arise !us voltage higher tha accepta!le voltage level such as the curve

5# I actual operatio o" wid "arm with "ull-load compesatio, the shut capacitor should !e

switched o gradually alog with the active power output icreasig# )ue to the shut capacitors

compesatio, the voltage collapse value i case 5 eual to 0#9 pu is higher tha that i case

5. or case 5 eual to 0#8 pu# ecause the reactive power output o" shut capacitors is

proportioal to A as the grid voltage decreasig, the

capacitors caot provide the ratig reactive power# 3he shut capacitorMs reactive power

capa!ility is limited i case o" lower voltage ad caot improve the voltage sta!ility o" the

local grid "udametally#


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3

'. 3DJ cur@e analysis of +indDfar9 +ith different generator

A-C curve is a power"ul tool to aalysis the steady-state voltage sta!ility limits ad reactive

power margis o" the grid !y descri!ig the relatioship !etwee the !us voltage ad the i%ected

reactive power ito the same ode# It illustrates the reactive power distace "rom the ormal

operatio poit to the voltage collapse poit# I this studies, the A$C curves o" di""eret active

power output o" wid "arms !ased o di""eret types o" wid tur!ies are show i "igure 8 to

"igure .0# I the case o" iductio geerator !ased wid "arm with o-load compesatio, there

is a .=Aar reactive power margi whe the wid "arm active power output is 00=$P i the

case o" )>I( !ased wid "arm, there is a .=Aar reactive power margi whe the wid "armactive power output is @00=$# 3he accepta!le i%ected real wid power i case 5 dou!le tha

that i case 5. !ecause the )>I( !ased wid tur!ies ca provide the reactive power to keep a

costat power "actor o" the whole wid "arm ad reactive power exchage ?ero i the &OI# 3his

characteristic o" )>I( !ased wid "arms would ehace the voltage sta!ility o" the local grid

itegratig wid power# +igh demad o" reactive power is the ma%or characteristic o" large wid

"arms that causes voltage pro!lems to power etworks# 3he larger the wid "arm, the more

severe this e""ect could !e# I" the etwork is ot a!le to meet the wid "arm reactive power

reuiremet, the wid power peetratio ito the power system should !e limited#

Fig. L.L 3DJ cur@e of +ind far9 ,ased on I$ +ith noDload co9=ensation


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Fig. L.M 3DJ cur@e of +ind far9 ,ased on I$ +ith fullDload co9=ensation

Fig. L. 3DJ cur@e of #FI$ ,ased +ind far9

TRANSI"NT 3O!TA$" STA'I!IT( ANA!(SIS

I the trasiet voltage sta!ility aalysis o" wid power itegratio, the voltage recovery issue o"

grid-coected wid tur!ies a"ter the clearace o" a exteral short-circuit "ault is a !asic topic#

I" the termial voltage o" the grid-coected wid tur!ies ca !e restored, the wid tur!ies ca

still !e coected ito the grid ad keep i service# I" the voltage caot !e restored, the wid

tur!ies eed to !e tripped or it will collapse the local grid voltage# >or trasiet voltage sta!ility

study i this paper, the three phase short-circuit "ault o the lie "rom !us to !us 6 is simulated


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at the simulatio time t F Is# 1"ter the "ault clearace, the trasmissio lie will !e tripped

simultaeously#

A. Transient @oltage sta,ility of I$ ,ased +indDfar9

I the case o" wid "arm with iductio geerator, the "ault critical clearig time is calculated

with the wid "arm istalled capacity icreasig# 3he simulatio results are show i ta!le .#

Ta,le L.> Fault Critical Clearing ti9e of I$ ,ased +ind far9

1log with the wid "arm istalled capacity icreasig, the "ault critical clearig time is reduced

sigi"icatly# $he the wid "arm istalled capacity is a!ove .0=$, the "ault critical clearig

time is reduced to 0 s# $hich meas eve i" the "ault clearig time is i"iite small, the iductio

geerator termial voltage caot !e restored !ecause the etwork is weakeed due to the tripped

lie# 3he trasmissio etwork should ot meet the reactive power demad o" the wid "arm

with high output ad the local loads so that the voltage collapse is occurred# $he the power

system relay protectio is cosidered, the lie with phase short-circuit "ault will !e tripped i 0#

Is#

It ca !e see that whe the wid "arm istalled capacity exceed .0 =$, the wid "armMs

voltage caot !e restored a"ter the "ault clearaceP the wid tur!ie geerator speed is

accelerated up to over-speedig# ecause wid tur!ies !ased o iductio geerator still eed

reactive power cosumptios durig the voltage recovery period ad the tripped lie weakes the

etwork co"iguratio, the local etwork trasiet voltage sta!ility will !e destroyed#


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'. Transient @oltage sta,ility of #FI$ ,ased +indDfar9

I the case o" wid "arm with dou!ly "ed iductio geerator, the "ault critical clearig time is

calculated with the wid "arm istalled capacity icreasig# 3he simulatio results are show i

ta!le #

Ta,le L. Fault Critical Clearing ti9e of #FI$ ,ased +ind far9

$he the wid "arm istalled capacity is lower tha 00=$, the "ault critical clearig time is

larger tha . sP the trasiet voltage sta!ility o" local grid is greatly larger tha i the case o"

iductio geerator# =ore wid power istalled capacity icreasigP the "ault critical clearig

time is also reduced demostratig that the trasiet voltage sta!ility is deteriorated# $he the

wid "arm istalled capacity reaches 00=$, the "ault critical clearig time is reduced to 0 s#

$he the power system relay protectio is cosidered, the lie with phase short-circuit "ault

will !e tripped i 0# Is# 3he wid tur!ies geerator termial voltage pro"ile# 3he wid tur!ies

protectio system doesMt !e take ito accout#

I all the study cases, the )>I( !ased wid tur!ies have a ,etter @oltage reco@ery

=erfor9ance tha the same ratig I( !ased wid tur!ies# )ue to the cotrol capa!ility to

regulate reactive power ad voltage, the )>I( wid tur!ies will mitigate the adverse a""ect o

voltage sta!ility o" the local trasmissio grid# *ve i" the wid "arm istalled capacity reaches

00=$, the cotrol system o" the )>I( also ca prevet the geerator speed "rom over-

speedig a"ter the "ault clearaceP !ut there is a im!alace !etwee the wid tur!ies

mechaical power ad electric power !ecause the low voltage "ollowig the "ault that limits the

wid "arm active power output, which results i the oscillatio o" the speed, power ad voltage


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o" the wid "arm# I actual operatio, it ca !e resolved !y trippig some wid tur!ies or !y

adoptig pitch cotrol to reduce the mechaical power o" the wid tur!ies#

3he "ollowig thigs ca !e cocluded "rom the studies doe a!ove

a# $id tur!ies euipped with simple iductio geerator are ot provided with reactive power

regulatio capa!ility# Aoltage sta!ility deterioratio is maily due to the large amout o" reactive

power a!sor!ed !y the wid tur!ie geerators durig the cotiuous operatio ad system

cotigecies#

!# $id tur!ies euipped with dou!ly "ed iductio geerator 5)>I( cotrolled !y the &$=

coverters are provided with reactive power regulatio capa!ilityP ca a!sor! or supply reactive

power durig ormal operatio# 3he adverse a""ect o local etwork voltage sta!ility is mitigated

so that more wid power istalled capacity ca !e icorporated ito the grid#

c# 3he trasiet voltage sta!ility characteristics o" wid tur!ies with )>I( are !etter tha wid

tur!ies with iductio geerator !ecause o" the voltage cotrol capa!ility o" the )>I( !ased

wid tur!iesP 3he )>I( !ased wid tur!ies have a !etter voltage recovery per"ormace tha

the I( !ased wid tur!ies with same ratig#


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;+1&3*R 7

CONC!USIONS


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CONC!USIONS

>rom the report we studied that wid has a lot o" potetial i it ad i" properly haressed the itca help solve the eergy crises i the world# 3he study o" wid tur!ie ad its characteristics

showed that how it ca !e properly desiged ad used to get the maximum output# 3he power

electroic circuitries have helped the cocept o" wid power a lot# $ithout them this cocept

would have !ee too expesive ad "ar "etched# $ith the thyristors ad coverters !eig used ot

oly the operatios have !ee smootheed !ut also the e""iciecy has !ee icreased to a great

extet# >rom the voltage sta!ility aalysis it was showed that how a dou!ly "ed iductio

geerator has superior characteristics tha a simple iductio geerator# 3his report also showed

the itegratio o" wid "arms with the trasmissio grid ad the pro!lems associated with it ad

the pro!a!le solutios that ca !e applied to solve them ad have a !etter per"ormace#


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R"F"R"NC"S

.# Bogig ;hi, Bahua

wind power.doc

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