TURBINA DE VIENTO

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Simulation for Wind TurbineGeneratorsWith FAST andMATLAB-Simulink Modules

M. Singh, E. Muljadi, J. Jonkman,and V. GevorgianNational Renewable Energy Laboratory

I. Girsang and J. DhupiaNanyang Technological University

NREL is a national laborator of the !"S" #e$artment of Ener%&ffi'e of Ener% Effi'ien' ( Rene)able Ener%&$erated b the Allian'e for Sustainable Ener%* LL+

This report is available at no ost !rom the "ational #ene$able Energ%&aborator% '"#E&( at $$$.nrel.gov)publiations.

Te'hni'al Re$ort"#E&)T*+,D--+,./.,

0pril 1-/2

3ontrat "o. DE+0345+-6G7164-6
http://www.nrel.gov/publicationshttp://www.nrel.gov/publicationshttp://www.nrel.gov/publications


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Simulation for Wind TurbineGeneratorsWith FAST andMATLAB-Simulink Modules

M. Singh, E. Muljadi, J. Jonkman,and V. GevorgianNational Renewable Energy Laboratory

I. Girsang and J. DhupiaNanyang Technological University

*repared under Task "os. 8E//.-445 and 8E/2.49-/

NREL is a national laborator of the !"S" #e$artment of Ener%&ffi'e of Ener% Effi'ien' ( Rene)able Ener%&$erated b the Allian'e for Sustainable Ener%* LL+

This report is available at no ost !rom the "ational #ene$able Energ%&aborator% '"#E&( at $$$.nrel.gov)publiations.

"ational #ene$able Energ%&aborator%/-/4 Denver 8est *ark$a%Golden, 37 6-2-/4-4+1:+4--- ; $$$ .n rel.g o v

Te'hni'al Re$ort"#E&)T*+D--+/

0pril 1-/2

3ontrat "o. DE+0345+-6G7164-6
http://www.nrel.gov/publicationshttp://www.nrel.gov/publicationshttp://www.nrel.gov/http://www.nrel.gov/publicationshttp://www.nrel.gov/


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N&T,+E

This report $as prepared as an aount o! $ork sponsored b% an agen% o! the


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iii

Thisreport is available at no ost !rom the "ational #ene$able Energ% &aborator% '"#E&( at $$$.nrel.gov)publiations.

A'kno)led%mentsThis work was supported by the Energy Research Institute at Nanyang TechnologicalUniversity, Singapore. The authors would like to thank Dr. hanh Nguyen !or !ruit!ul

discussions about integrating the National Renewable Energy "aboratory#s $atigue,

%erodyna&ics, Structures, and Turbulence &odel with the e'ternal drivetrain &odel, especiallyas related to Section (.
http://www.nrel.gov/publicationshttp://www.nrel.gov/publications


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iv


List of A'ronms)%E co&puter*aided engineeringD$I+ doubly*!ed induction generator

$%ST $atigue, %erodyna&ics, Structures, and Turbulence

&odel+R) +earbo' Research )ollaborative

SS high*speed sha!t

I+-T insulated*gate bipolar transistor

"SS low*speed sha!t%T"%- atri' "aboratory

NRE" National Renewable Energy "aboratory

SD) stress da&per controller /ID) virtual inertia and da&ping control

0RI+ wound*rotor induction generator

0T+ wind turbine generator


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v


Abstra'tThis report presents the work done to develop generator and gearbo' &odels in the atri'"aboratory 1%T"%-2 environ&ent and couple the& to the National Renewable Energy

"aboratory#s $atigue, %erodyna&ics, Structures, and Turbulence 1$%ST2 progra&. The goal o!

this pro3ect was to inter!ace the superior aerodyna&ic and &echanical &odels o! $%ST to thee'cellent electrical generator &odels !ound in various Si&ulink libraries and applications. The

scope was li&ited to Type 4, Type 5, and Type 6 generators and !airly basic gear*train &odels.

The !inal product o! this work was a set o! coupled $%ST and %T"%- drivetrain &odels.

$uture work will include &odels o! Type 7 generators and &ore*advanced gear*train&odels with increased degrees o! !reedo&. %s described in this study, the developed

drivetrain &odel can be used in &any ways. $irst, the &odel can be si&ulated under di!!erent

wind and grid conditions to yield !urther insight into the drivetrain dyna&ics in ter&s o!predicting possible resonant e'citations. Second, the tool can be used to si&ulate and

understand transient loads and their couplings across the drivetrain co&ponents. Third, the

&odel can be used to design the various !le'ible co&ponents o! the drivetrain such thattrans&itted loads on the gearbo' can be reduced. Several case studies are presented as e'a&ples

o! the &any types o! studies that can be per!or&ed using this tool.


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vi


Table of +ontents ,ntrodu'tion""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""" . FAST #es'ri$tion """"""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""" // ,nterfa'in% FAST and MATLAB0Simulink"""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""" 1

6.4 Step*by*Step 8reparation ............................................................................................................. 9

6.5 $%ST $iles and Data Entry ......................................................................................................... :2 Wind Turbine Modelin% """"""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""

7.4 Type 4 0ind Turbine odel ..................................................................................................... 477.4.4 8ree'isting $%ST Type 4 Turbine odels 1Steady*State odel2 ................................ 47

7.4.5 Dyna&ic Induction achine odel ............................................................................. 5;

7.4.6 %ddition o! 8itch )ontroller ......................................................................................... 51 Dt>doubl e 3>-

Si gnal Spei !i ation/

1

Ca$ *osi ti on 'rad( and #ate'rad)s(

4

?l ade *i th 0ngl es'rad(

D>1 Dt>doubl e 3>-

Si gnal Spei !i ation1

90ST S9un emu

Bdotdot

/

/ Bdot / B

s s

7utData

S+9unti on

Bdot

B

Fi%ure 2" ,nside the )ind turbine blo'k of the FAST )ind turbine model in Simulink

44. Cn the !irst try, the si&ulation will not run because the Test01."st !ile has been set up to

use the %D%S preprocessor, which is not available in %T"%-BSi&ulink. The readerhas to open and &odi!y the Test01."st using a te't editor, such as Notepad. $ind the

!ollowing line near the top o! the page@


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6 %D%S8rep * %D%S preprocessor &ode P4@ Run $%ST, 5@ use $%ST as a preprocessor to create an

%D%S &odel, 6@ do bothQ 1switch2

and change it to@4 %D%S8rep * %D%S preprocessor &ode P4@ Run $%ST, 5@ use $%ST as a preprocessor to create

an %D%S &odel, 6@ do bothQ 1switch2

The reader &ay now save the !ile in the sa&e !older under a di!!erent na&e, !ore'a&ple, Test01A."st, and return to Step ( to repeat the instructions, e'cept load

Test01A."st instead o! Test01."st when pro&pted to in Step


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Fi%ure 1" Error dia%nosti' )hile runnin% Test01_SIG.mdl

3lok

Time

To 8orkspae

Gen speed $rt &SS '#*M( GenTrB, Ele*$r

Simple Induti on Generator

Gen. TorBue '"m( and *o$er '8(

7ut/

Ca$ 3ontrol ler

7ut/

Ca$ *osition 'rad( and #ate 'rad)s(

?lade *ith 0ngles 'rad(

7utData 7utData

*i th 3ontrol ler

90ST "onlinear 8ind Turbine

9n

!'u(

Selet &SS speed at entran e to gearbo = 'rpm(

Fi%ure 5" Test01_SIG.mdl in Simulink


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3lok

Time

To 8orkspae

3onstant1

S o pe S o pe /

Sel et &SS speed at entrane to gearbo= 'rpm (

-

0dd


Si mple Induti on Generator

Gen. TorBue '"m( and *o$er '8(

3onstant

2

S$i th

7ut/

Ca$ 3ontrol ler

7ut/

C a$ *osition 'rad( and #ate 'rad)s(


7utData

7utData

*i th 3ontrol ler

90ST "onl inear 8i nd Turbi ne #otTorB

&SSGagV=a

Fi%ure 6" Modified model )ith S)it'h* +onstant* and Add blo'ks

This error occurs because the Si&ple Induction +enerator &odel does not receive any input!or the !irst ti&e step 1i.e., no initial condition2. Thus, this error can be resolved by &odi!ying

the &odel to initialiKe an input to the generator &odel. )onsider the Test01_SIG.mdl &odelshown in $igure (. Drag and drop a )onstant and a Switch block !ro& the Commonly Used

Blocks directory and an %dd block !ro& the Math Operations directory in the Si&ulink

"ibrary -rowser. Using these blocks, &odi!y the &odel as shown in $igure A. The initialiKation

and Kero* addition ensure that an initial condition is de!ined to the generator &odel. Theti&e threshold value !or the switch is set to t&0.1 s. %lso, note the addition o! a signal De&u'

block 1!ro& the Signal Routing directory2. This allows the reader to e'tract and plot the desired

$%ST outputs.

/". FAST Files and #ata Entr

So&e te't editing is necessary to set up the $%ST*%T"%-BSi&ulink inter!ace. 8rogra&s such

as Notepad and 0ordpad are su!!icient !or these tasks. The reader should associate the!ollowing !iles@

."st !iles@ These are $%ST input !iles that contain the turbine &ain para&eters that are

to be loaded by the Simsetup.m !ile. any ."st !iles 1Test01."st through Test1'."st2are provided in the C:FASTCertTest !older !or di!!erent turbines under a varietyo! operating conditions. Editing these !iles is necessary to change the turbine data,control &ethods, si&ulation conditions, step ti&es, and outputs.

.ipt !iles@ These are aerodyna&ic data !iles de!ined under the %erodyn section o! ."st !ile.

These !iles call the blade air!oil and wind !iles 1.(nd !iles2.

.(nd !iles@ These !iles contain the wind pro!iles@ speed, direction, etc.

Editing ."st !iles was discussed above. The only editing e&ployed !or .ipt !iles is to change the

na&e o! the .(nd !ile that the .ipt !ile calls. These !iles can be !ound in the

C:FASTCertTest)ind !older, which contains &ultiple .(nd !iles !or di!!erent turbine types.

The Test01."st !ile &odels the %0T*5A, a two*bladed downwind turbine. The contents o!S*r1+_,0.(nd, a wind !ile associated with Test01."st, are presented below@

0ind !ile !or sheared 4< &Bs wind with 6;*degree

direction.

Ti&e 0ind 0ind /ert. oriK. /ert. "in/ +ust


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Speed Dir Speed Shear Shear Shear Speed;.; 45.; 6;.; ;.; ;.; ;.5 ;.; ;.;

;.4 45.; 6;.; ;.; ;.; ;.5 ;.; ;.;:::.: 45.; 6;.; ;.; ;.; ;.5 ;.; ;.;

$or si&plicity and !uture testing o! controllers, we reco&&end editing this !ile to include a step

change in the wind speed !ro& 45 &Bs to 49 &Bs at ti&e t&10 s. $or now, all gust and shearco&ponents can be re&oved, and wind direction can be assu&ed to be perpendicular to the

plane o! rotation o! the turbine. The !ile can be saved as a new !ile, S*r1+_,0%.(nd, and theTest01_A-.ipt !ile can be &odi!ied to call the &odi!ied !ile rather than S*r1+_,0.(nd. The !ile

should look as shown below@

0ind with step change at t J 4; s !ro& 45 &Bs to 49&Bs. Ti&e 0ind 0ind /ert. oriK. /ert. "in/ +ust

Speed Dir Speed Shear Shear Shear Speed;.; 45.; ;.; ;.; ;.; ;.; ;.; ;.;

:.: 45.; ;.; ;.; ;.; ;.; ;.; ;.;

4;.; 49.; ;.; ;.; ;.; ;.; ;.; ;.;:::.: 49.; ;.; ;.; ;.; ;.; ;.; ;.;

%t this stage, the reader should be co&!ortable working with $%ST and %T"%-BSi&ulink

and should be con!ident about &aking changes to the &odel and $%ST input !iles. The reader

should consult the FAST Users Guide i! additional in!or&ation is re?uired. The ne't section!ocuses on creating realistic induction generator &odels instead o! using the ones e&ployed by

$%ST.


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2 Wind Turbine Modelin%0ind turbines are co&ple' electro&echanical devices interacting with a changing environ&ent.odelers o! wind turbines typically concentrate on the details o! subsyste&s or aspects o! a

turbine that they are interested in while using si&plistic representations o! other subsyste&s. In

particular, aerodyna&ic &odelers o! wind turbines tend to oversi&pli!y a turbine#s electricalsyste&sL likewise, electrical &odelers ignore or oversi&pli!y turbine aerodyna&ics. These

approaches &ay lead to inaccurate and unrealistic &odels. $or e'a&ple, tor?ue pulsations

caused by the tower shadow e!!ect observed in downwind turbines &ay i&pact electrical

syste&s, but &ost electrical &odels do not account !or this e!!ect. This user#s guide is intended!or those interested in developing holistic wind turbine &odels that include detailed

aerodyna&ics and structural, &echanical, and electrical syste&s using the $%ST code

developed by NRE" inter!aced with the popular %T"%-BSi&ulink plat!or&.

-ecause $%ST#s in*built !unctionality accurately represents wind turbine aerodyna&ics andstructures 1see theFAST Users Guide2, this guide concentrates on &odeling electrical syste&s in

%T"%-BSi&ulink and on how to inter!ace these electrical syste& &odels with the $%ST

code. This guide will be particularly use!ul !or non>electrical engineers looking to evaluateturbine per!or&ance with a realistic generator &odel. It is assu&ed that the reader is !a&iliarwith the %T"%-BSi&ulink environ&ent and is capable o! so&e si&ple progra&&ing. In the

!ollowing subsection, classi!ication o! wind turbine technology is presented !ro& an electrical

engineering point o! view.

%ccording to di!!erences in generation technology, wind turbines have been classi!ied into !ourbasic types@

Type 4@ $i'ed*speed wind turbines

Type 5@ /ariable*slip wind turbines

Type 6@ Doubly*!ed induction generator 1D$I+2 wind turbines

Type 7@ $ull*converter wind turbines

$i'ed*speed wind turbines 1popularly known as the Danish concept2 are the &ost basic utility*

scale wind turbines in operation. They operate with very little variation in turbine rotor speedand e&ploy s?uirrel*cage induction &achines directly connected to the grid. E'ternal reactive

power support is necessary to co&pensate !or the reactive power consu&ed by the induction

&achine. -ecause o! the li&ited speed range in which these turbines operate, they are proneto tor?ue spikes that &ay da&age the &echanical subsyste&s within a turbine and cause

transients in the electrical circuitry. These turbines &ay e&ploy stall regulation, active stall

regulation, or blade pitch regulation to regulate power at high wind speeds. Despite being

relatively robust and reliable, there are signi!icant disadvantages o! this technology, na&ely thatenergy capture !ro& the wind is subopti&al and reactive power co&pensation is re?uired. %n

e'a&ple o! a popular !i'ed*speed wind turbine is the NE+ icon N(7B49;; turbine, rated at

4.9 0. % sche&atic !or a !i'ed*speed wind turbine is shown in $igure


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-rive

Train%0&irrel

Cage 12

Pa'3$o&nte'Transfor$er

To gri'

Fi%ure 4" Fi=ed-s$eed )ind turbine s'hemati'

/ariable*speed wind turbines 1the broad category into which the other three do&inant

technologies !all2 are designed to operate at a wide range o! rotor speeds. These turbines usually

e&ploy blade pitching !or power regulation. Speed and power controls allow these turbines toe'tract &ore energy !ro& a given wind regi&e than !i'ed*speed turbines can. /ariable*slip

turbines e&ploy wound*rotor induction &achines that allow access to both the stator and

the rotor o! the &achine. The rotor circuit o! the &achine is connected to an alternating current

1%)2Bdirect current 1D)2 converter and a !i'ed resistance. The converter is switched tocontrol the e!!ective resistance in the rotor circuit o! the &achine to allow a wide range o!

operating slip 1speed2 variation 1up to 4;2. owever, power is lost as heat in the

e'ternal rotor circuit resistance. % controller &ay be e&ployed to vary the e!!ective e'ternalrotor resistance !or opti&al power e'traction. Reactive power co&pensation is still

re?uired. /estas CptiSlip turbines, such as the /estas /(( 14.(9 02, were the &ost

success!ul turbines to e&ploy this technology. % sche&atic !or this technology is shown in$igure :.

-rive

Train

4o&n'3

Rotor

12

%tator

Pa'3$o&nte'5er

To gri'

Rotor

Controls

Fi%ure 8" >ariable-sli$ )ind turbine s'hemati'

D$I+ turbines re&edy the proble& o! power loss in the rotor circuit by e&ploying a back*

to* back %)BD)B%) converter in the rotor circuit to recover the slip power. $lu'*vector controlo! rotor currents allows decoupled real and reactive output power as well as &a'i&iKed wind

power e'traction and lowered &echanical stresses. %lso, these turbines usually e&ploy blade

pitching !or power regulation. -ecause the converter handles only the power in the rotorcircuit, it does not need to be rated at the &achine#s !ull output power. The disadvantages o!


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this technology=


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na&ely, higher cost and co&ple'ity=are o!!set by the ability to e'tract &ore energy !ro&a given wind regi&e than the preceding technologies. The +eneral Electric 4.9*0 turbine is

an e'a&ple o! a success!ul D$I+ i&ple&entationL &ore than 49,;;; have been installed. %

sche&atic !or this technology is shown in $igure 4;.

-rive

Train

4o&n'3

Rotor

12

%tator

Pa'3$o&nte' 5er

Rotor

Controls

Fi%ure 7" #F,G )ind turbine s'hemati'

In !ull*converter turbines, a back*to*back %)BD)B%) converter is the only power !low path

!ro& a wind turbine to the grid. Thus, there is no direct connection to the grid, and the converter

has to be rated to handle the entire output power. These turbines usually e&ploy high*pole*count, per&anent &agnet, synchronous generators to allow low*speed operation, thus

allowing the eli&ination o! the gearbo' to increase reliability. Nonetheless, using induction

generators is also possible. %lso, !ull*converter turbines o!!er independent real and reactivepower control, and they typically e&ploy blade pitching !or power regulation. % sche&atic !or

this technology is shown in $igure 44. %lthough these turbines are relatively e'pensive, the

increased reliability and si&plicity o! the control sche&e vis**vis D$I+ turbines are attractive

!eatures, especially in o!!shore installations where &aintenance is costly. Enercon &anu!acturesturbines based on this technology, such as the popular E


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C! the !our types o! turbines, this docu&ent !ocuses on Type 4 and 5 turbines because theyshow the &ost coupling between &echanical and electrical syste&s. The ne't section describes

the &odeling o! Type 4 turbines.

2" T$e Wind Turbine Model

Type 4 wind turbines are the least co&ple' utility*scale turbines. They consist o! a rotor 1bladesand hub2 coupled to a s?uirrel*cage induction generator through a gearbo'. The gearbo' and

generator are situated within the nacelle o! the turbine at the top o! the tower. The stator o! theinduction generator is connected to the grid through a step*up trans!or&er. % shunt capacitor

bank is typically added to provide reactive power support. Electrical controls are

typically &ini&al, though &echanical controls such as yaw control and blade pitchcontrol &ay be e&ployed. %n e'a&ple &odel provided in $%ST, Test01_SIG.mdl, is a Type 4

turbine &odels. This section covers &odi!ications to Test01_SIG.mdl to i&prove the e'isting

induction generator &odel, which inade?uately represents the generator#s dyna&ics. The

!ollowing subsections evaluate the de!iciencies o! the e'isting &odels, identi!y an alternate&odel, and discuss the i&ple&entation o! the &odel in Si&ulink. It also discusses the

develop&ent o! a blade pitch angle controller to co&plete the Type 4 &odel. Vaw control willbe addressed in the !uture.

Fi%ure ." Subsstems for a T$e turbine model

4.1.1 Preexisting FAST Type 1 Turbine odels !Ste"dy#St"te odel$

Type 4 turbines &ay be represented as a co&bination o! subsyste&s. The !ra&ework shown in

$igure 45 is typically used !or &odeling purposes. $or our purposes, $%ST per!or&s all the

!unctions o! the aerodyna&ic and &echanical blocks, with so&e additional !unctionality notshown in $igure 45. 0e chose $%ST because o! its great !idelity to real*world turbine

aeroelastic characteristics.

$%ST inherently provides induction generator &odels. Two para&eters in the ."st input !ile

govern $%ST#s choice o! the generator &odel@ /S)ontrl and +enodel. The para&eter

/S)ontrl deter&ines i! tor?ue is actively controlled 1i.e., whether a turbine is !i'ed*speed orvariable*speed2. I! /S)ontrl is set to ;, the turbine is assu&ed to be one o! !i'ed speed.


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$%ST


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Tor

Bue

Table "


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R! 5! 5)

.C

7LLf

5$R)6s

Fi%ure 1" ,ndu'tion ma'hine sin%le-$hase e?ui3alent 'ir'uit

Table ." S+ontrl @ 7* GenModel @ .;

TE39reB f This is the line !reBuen% o! the eletrial grid. This value must be greater than - andshould be - 'Europe( or 5- '


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own variable*speed generator &odel in $CRTR%N. Neither o! these options was applicable.Setting /S)ontrl J 6 allows input !ro& Si&ulink, which is desired. This setting is to be used to

run the e'a&ple &odel Test01_SIG.mdl. 0hen /S)ontrl is no longer Kero, the

+enodel para&eter is ignored by $%ST and the tor?ue input to the $%ST turbine &odel &ust

co&e !ro& elsewhereL in our case that was Si&ulink. %lthough a nonKero value o!

/S)ontrl i&plied variable*speed operation, we could still &odel a !i'ed*speed turbine. $igure (shows the &odel Test01_SIG.mdl. The top le!t shows a subsyste& block labeled Si&ple

Induction +enerator. This block received a speed input !ro& $%ST and delivered tor?ue powervectors as output. The &odel inside this block was i&ple&ented the sa&e linear tor?ue

calculation as in $igure 49, solved using Si&ulink blocks instead o! $CRTR%N. Double*

clicking on the subsyste& block opened a new window o! its internal co&ponents, as shown in$igure 49. The low*speed sha!t 1"SS2 speed in rp& was converted to the high*speed sha!t 1SS2

speed 2 at the generator in radiansBsec using the gearbo' ratio, de!ined in the ."st !ile.

Synchronous speed value SI+WSySp

2S was then subtracted !ro& the SS speed. The resulting di!!erence ( ) was&ultiplied

by the tor?ue*speed slope 1SI+WSlop2, which, !ro& $igure 47, can be written as

. The

resulting output tor?ue was =

. This output tor?ue was li&ited to a &a'i&u&

value speci!ied by the pullout tor?ue SI+W8CRt. The output tor?ue was &ultiplied by speed

2and e!!iciency 3 to give output power 1i.e., = 2. The tor?ue and power were

&ultiple'ed

into a 5

4 vector as a $%ST input because this is the way it &ust be delivered. Note thatthere

was a &inor error in the e'a&ple !ile Test01_SIG.mdl. The e!!iciency was speci!ied in percent

rather than per unit, hence the output power !ro& the &odel was 4;; ti&es larger than the actualoutput in watts. Thus, we divided the power results by a !actor o! 4;; be!ore plotting. It appears

that $%ST does not use the power value, so this ano&aly did not a!!ect the si&ulation results.

To run the si&ulation, please !ollow the steps prescribed in Section 6 !or Test01_SIG.mdl, using

the &odi!ied wind !ile S*r1+_,0%.(nd, which has a step change in the wind speed.


Simple Indution Generator


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Fi%ure 5" Tor?ue 'al'ulation from s$eed* im$lemented in Simulink


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Fi%ure 6" E=am$le of a MATLAB s'o$e out$ut durin% run time


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TorBue'"m(

HSSSpeed'rad)s(

*o$er'8(

1--

1---

/--

/---

--

-- 1 2 5 6 /- /1 /2 /5 /6 1-

time's(

/1

/16

/1:

/15

- 1 2 5 6 /- /1 /2 /5 /6 1-time's(

= /-

4

1

/

-- 1 2 5 6 /- /1 /2 /5 /6 1-

time's(

Fi%ure 4" Tor?ue* s$eed* and out$ut $o)er from Test01_SIG.mdl )ith a ste$ 'han%e in the )inds$eed

The results showed that a signi!icant step change in wind speed, !ro& 45 &Bs to 49 &Bs, causeda very s&all 1less than 42 change in the SS speed 1!ro& 45< radBs to 45


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these &odels in this docu&ent. The reader should download all !iles in the online repositoryto the C:FASTCertTest !older, which is the %T"%- working directory. 0e reco&&end that

the reader beco&es !a&iliar with these &odels, using Cng#s book as a re!erence. 0e used the

induction &otor &odel in the S1.mdl !ile, shown in $igure 4:. This &achine &odel will later be

con!igured as a generator &odel.

/1-piomegat

3lok

psiBs

iBs

Mu=

Mu=

Sope

%

To 8orkspae

Initialie

and plot

m/

Vmos'u/J( vag

Ka=i s

psiBrTerm

9n

vbg

vBs Tem

*rodut

ias

Vmos'u/+1pi )4(

9n/

Vmos'u/L1pi )4(

9n1

vg

ab1Bds

vds

v-s

*rodut/

psids

ids

$r)$b

Tmeh

#otor

Bds1ab

ibs

is

Sum

Induti on Mahine Simulation

in Stati onar% #e!erene 9rame

Da=is

psidrTerm/

NeroseB

i-s

Fi%ure 8" ,ndu'tion ma'hine model S1.mdl

%s shown on the le!t o! $igure 4:, three voltage signals were generated, which took the !or&

o! =

((((((((((((((( + ). The signals were ti&e*shi!ted by 45;Y !ro& each other, with 4

taking the

values o! ;Y, *45;Y, and Z45;Y !or phases a, 5, and / respectively. The three*phase voltageswere

then trans!or&ed into two orthogonal vectors 1d*a'is and 6*a'is2 and a D) co&ponent 1;*a'is2

using the d6; trans!or&ation, also known as 8ark#s trans!or&ation, the details o! which can be

!ound in Analsis o" le/tri/ a/*iner by 8.). rause 1c+raw*ill 4::


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38/78

Cnce co&!ortable with S1.mdl, the reader can proceed to inter!acing this &achine &odel with$%ST. The steps !or this inter!acing are as !ollows@

4. Cpen the Si&ulink &odels Test01_SIG.mdl and S1.mdl. $ro& the Ports &

Subsystems directory o! the Si&ulink library browser, input a Subsyste& block to the

Test01_SIG.mdl.

5. Double*click on the newly added Subsyste&s block. The newly opened windowwill show an input port directly connected to an output port. Delete the connection

between the two. )opy input 4 and paste it back in. This will provide the second input

port 1i.e., input 52. In this e'a&ple, input 4 is !or the clock signal and input 5 is !or thespeed signal !ro& $%ST. odi!y the input and output port labels accordingly by double*

clicking the labels. )lose the subsyste& window. In the &ain Si&ulink window, double*

click the subsyste& label and enter a label o! choice, !or e'a&ple Induction achine

odel, as shown in $igure 5;.

6. Delete the Si&ple Induction +enerator block !ro& the Test01_SIG.mdl.

7. In the &ain Si&ulink window, connect the Induction achine odel#s input 4 to the)lock signal and input 5 to the speed signal "SS+ag/'a !ro& $%ST. )onnect

the Induction achine odel#s output to the $%ST +en. Tor?ue 1N&2 and 8ower 102input. The &odel should appear as shown in $igure 4(.

3lok

Time

To 8orkspae3onstant1

-

Sel et &SS speed at entrane to gearbo= 'rpm (

3lok input

0ddGen TorBue '"m( and *o$er '8( Gen. TorBue '"m( and *o$er '8(

3onstant

2S$i th

&SS Speed input 'rpm(

Induti on Mahi ne ModelCa$ *osition 'rad( and #ate ' rad )s ( 7ut Da ta 7utData

7ut/

Ca$ 3ontrol ler

7ut/

*ith 3ontrol ler


90ST "onl inear 8ind Turbine

#otTorB

&SSGagV=a

Fi%ure .7" Modified Test01_SIG.mdl sho)in% the Sim$le ,ndu'tion Generator blo'k re$la'ed)ith the ,ndu'tion Ma'hine Model blo'k

Double*click on the subsyste&. )opy all the blocks !ro& S1.mdl into the

Induction achine odel in Test01_SIG.mdl. Inside this subsyste&, delete the

initialiKation )lock blocks. )onnect the input 4 to the input o! the o&ega[t +ain block

and to the white block labeled u'.

9. $ro& the Si&ulink "ibrary browser, drag and drop into the subsyste& !our +ain blocksand a 8roduct block !ro& the Math Operations directory, a signal Ter&inator block

!ro& the Sinks directory, and a u' block !ro& the Signal Routing directory. These

blocks are shown in $igure 54.


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/

Gain *rodut Terminator

Fi%ure ." Blo'ks for the subsstem :Gain*


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input


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o! the newly added u' block and to one o! the inputs o! the 8roduct block. )onnect theper unit speed output to the input o! the o&ega[t5 +ain block to get speed in radians

per second. )onnect the output o! this block to the re&aining input o! the 8roduct block

so that the product o! tor?ue and speed gives the output power. )onnect the output o! this

block to the lower input o! the u' block. )onnect the output o! the u' block to the

output port 4 o! the subsyste&. The output is now con!igured.:. Ensure that the &odel is initialiKed with the correct data. Cpen p1*p.m and !ind

the !ollowing state&ents@


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8ara&eters o! &achine used in 8ro3ects 4 and 6 o! )hapter (

Sb J A9;L rating in /%

8rated J A9;L output power in 0

/rated J 5;;L rated line to line voltage in /

p! J ;.


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Analsis o" le/tri/ a/*iner by 8. ). rause, with slight adaptation to represent the59;*k0, (*pole &achine e&ployed in the %0T*5A turbine@

Sb J 5AAAAA.AAAL rating in /%

8rated J 59;;;;L output power in 0

/rated J 56;;L rated line to line voltage in /

p! J ;.:L

Irated J SbB1s?rt162[/rated[p!2L rated r&s current

8 J (L nu&ber o!poles

!rated J (;L rated !re?uency in ,K

wb J 5[pi[!ratedL base electrical !re?uency

we J wbL

wb& J 5[wbB8L base &echanical !re?uency

Tb J SbBwb&L base tor?ue

\b J /rated[/ratedBSbL base i&pedance in oh&s

/& J /rated[s?rt15B62L &agnitude o! phase voltage

/b J /&L base voltage

T!actor J 16[82B17[wb2L !actor !or tor?ue e'pression

rs J ;.5(5L stator wdg resistance in oh&s

'ls J (.:7e*6[wbL stator leakage reactance in oh&s

'ls J 4.5;(L

'plr J 'lsL rotor leakage reactance

'& J 4(6.A6e*6[wbL stator &agnetiKing reactance

'& J 97.;5L

rpr J ;.4


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45/78


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Fi%ure ./" +han%e in +< 'ur3es )ith 'han%e in $it'h an%le :beta;

There is a nonlinear relationship between the blade pitch angle and rotor power coe!!icient, andany controller design &ust take this into account. -lade pitch angle actuators &ust also be able

to contend with dyna&ic tor?ues acting on the turbine blades while pitching the&. 0e

i&ple&ented a si&ple pitch controller in Si&ulink that uses power and speed inputs to set an

appropriate blade pitch angle.

The $%ST block in Si&ulink allows users to develop their own pitch controllers, which providethe pitch angle co&&and to $%ST through the speci!ied input port, as shown in $igure 57. %n


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3lok

Time

To 8orkspae3onstant1

-

Sel et &SS speed at entrane to gearbo= 'rpm(

3lok input


3onstant

2 S$ith


Induti on Mahine Model

Ca$ *osition 'rad( and #ate ' rad)s( 7utData 7utData

Dumm% pith ontroller

blok 'inputs eroes(

7ut/

Ca$ 3ontrol ler

7ut/

*i th 3ontrol ler


90ST "onlinear 8ind Turbine

90ST blok pith angle inputs '/ input

time+series reBuired per blade(

#otTorB

&SSGagV=a

Fi%ure .2"


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Fi%ure .5"


50/78

TorBu

e'"m(

HSSSpeed'rad)s(

*o$er'8(

3l ok

T i me

T o 8orkspae3onstant1

-

Sel et &SS speed at entrane to gearbo= 'rpm(

3lok input


3onstant

2S$i th


Induti on Mahi ne ModelCa$ *osition 'rad( and #ate ' rad) s( 7ut Dat a 7utData

+O+

T ermi nator7ut/

Ca$ 3ontrol l er

In/7ut/


90ST "onl i near 8i nd T urbine

#otTorB

&SSGagV=a

G?#ati opi )4- In1

*i th 3ontrol l er

Fi%ure .6" +onne'tions in the main Simulink )indo)

1,--

1---

/,--

/---

,--

-

- 1 2 5 6 /- /1 /2 /5 /6 1-

time's(

/1.

/16

/1:

/15

- 1 2 5 6 /- /1 /2 /5 /6 1-

time's(,

= /-4

1

/

-- 1 2 5 6 /- /1 /2 /5 /6 1-

time's(

Fi%ure .4" Results )ith $it'h 'ontroller enabled

Now, with the pitch controller i&ple&ented, run the si&ulation in a si&ilar !ashion, as be!ore. %

scope should be connected to the 8itch )ontroller#s output. %!ter the si&ulation, the

results should agree with those shown in $igure 5


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Fi%ure /7" T$e turbine Sim


53/78

diode bridge recti!ier. 0hen the I+-T is in the on state, it shorts the rotor circuit, reducinge'ternal rotor resistance to near Kero. 0hen it is in the o!! state, the e'ternal resistance is not

bypassed and !or&s a part o! the rotor circuit. -y varying the duty cycle o! the I+-T switching,

the e!!ective rotor resistance o! the &achine can be varied. The e!!ective rotor resistance is

a value between Kero and the !i'ed value o! the e'ternal resistor. The higher the duty cycle, the

lower the e!!ective e'ternal resistance is. % detailed e'planation o! the e!!ects o!e'ternal resistance on the tor?ue*slip characteristics o! the wound*rotor induction &achine,

and a controller to change e'ternal resistance, are described in the !ollowing subsection.

8ound+rotor indution

generator

Step+up trans!ormer

#otor iruit4+phase diode

bridge

IG?T

Grid bus

E=ternal

resistor

%pee' Slip

ontroller

P42

p&lses

Power

#eative po$er

ompensation

Fi%ure /"


54/78

R4 ]4

]&

]5 R5s

Re'ts

Fi%ure /." ,ndu'tion ma'hine e?ui3alent 'ir'uit )ith e=ternal resistor $resent

Fi%ure //" E=am$le tor?ue-s$eed 'ur3es )ith different 3alues of e=ternal rotor resistan'e Re=t

:e=$ressed $er unit of internal rotor resistan'e R.;

% variable resistor is present in each phase because the e?uivalent circuit represents each

phase o! a balanced three*phase circuit. % desired tor?ue value can thus be achieved at &any

di!!erent speeds by varying the e'ternal rotor resistance, as shown in $igure 66. The &odeldescribed here lu&ps the two resistances $5 and $ext into one co&bined rotor resistance $rotor.

0e did not e'plicitly &odel the power electronics or resistances, but rather calculated a

value o! the resistance and input this value into the &odel.

4.%.% Implement"tion

In our i&ple&entation, we atte&pted to deliver constant e!!ective rotor resistance, thusconstant

tor?ue, within a given range o! rotational speed. This &ay be e'pressed by the e?uation 2 =

2+ =

. The e'ternal resistance value was chosen such that, whatever the new value o!

slip was, the e!!ective rotor circuit resistance re&ained the sa&e. The user will need to&akeso&e &odi!ications to input a rotor resistance value to the induction &achine &odel. These

&odi!ications involve replacing all constant rotor resistance values rpr 1see Simsetup%.m2 with

variable input. )onsider the diagra& o! the induction &achine &odel shown in $igure 4: 1i.e.,within the Induction achine odel subsyste&2. Note the subsyste&s labeled Fa'is


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and


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Da'is. Double*click the Da'is subsyste&. The contents o! the subsyste& are shown in $igure

67.

/

outpsi ds

/

i nvds

Mu= $b'u1JL'rs)=l s('u/J+

u4J(( 9n

/

s

psi ds

psi ds Mu=

Mu=2

'u/+u1()=l s

9n2

i ds1

outi ds

Mu=

Mu= =M'u/)=l sLu1)=plr(

psi Bm

1

i n'$r)$b(psi BrQ

Mu=

Mu=/

$b'+u1 L'rpr)=pl r('u4J+

u/J(( 9n1

/

s

psi drQ

psi drQ

Mu=4

Mu=

Mu=1

9n4

'u/+u1()=pl r

9n

i drQ

2

outpsi drQ

4

outi drQ

Fi%ure /2" &ri%inal 'ontents of #a=is subsstem

/

outpsi ds

/

invds

Mu = $b 'u 1 JL'rs) =ls('u/J+

u4J(( 9n

/

s

psi ds

psi ds Mu=

Mu=2

'u/J+u1J()=l s

9n2

ids1

outi ds

Mu=

Mu= =M 'u/)=l sLu1J)=plr(psi Bm

1

in'$r)$b(psiBrQ

Mu=

Mu=/

$b'+u1 L'u2J)=plr('u4J+u/J((

9n1

/

s

psi drQ

psi drQ

Mu=4

Mu=

Mu=1

9n4

'u/J+u1J()=pl r

9n

idrQ

2

outpsi drQ

4

outi drQ

4

#otor#es

Fi%ure /1" Modified 'ontents of #a=is subsstem

Note that the e'pression o! F/n+ block, !ollowing the ux1 block, &akes use o! the constant

rpr. Each o! the &ultiple'ed signals is represented by uG4H, uG5H, and uG6H. % !ourth signal,

uG7H, needs to be added to replace the rpr. To do this, double*click on the ux1 block andchange the nu&ber o! inputs !ro& three to !our. % !ourth input port will appear. )opy the input

port 5 and paste it back in. It will create the input port 6. odi!y the label o! the input port 6 to

RotorRes. )onnect this input port to the !ourth input o! ux1. Double*click the F/n+ block

and replace the string rpr with u G7H. The &odi!ied diagra& is shown in $igure 69. %nidentical process &ust be !ollowed with the Fa'is subsyste&, as shown in $igure 6( and

$igure 6A.


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/

outpsi Bs

/

invBs

Mu = $b 'u 1 JL'rs)=ls('u/J+

u4J(( 9n

/

s

psiBs

psiBs Mu=

Mu=2

'u/+u1()=l s

9n2

iBs1

outi Bs

Mu=

Mu= =M'u/)=l sLu1)=pl r(psiBm

1

in'$r)$b(psidrQ

Mu=

Mu=/

$b'u1 L'rpr)=pl r('u4J+u/J((

9n1

/

s

psiBrQ

psiBrQ

Mu=4

Mu=

Mu=1

9n4

'u/J+u1J()=plr

9n

iBrQ

2

outpsi BrQ

4

outi BrQ

Fi%ure /5" &ri%inal 'ontents of Ca=is subsstem

/

outpsiBs

/

invBs

Mu= $b'u1L'rs)=ls('u/+u4((

9n

/ s

psiBs

psiBs Mu=

Mu=2

'u/+u1()=ls

9n2

iBs1

outiBs

Mu=

Mu= =M'u/)=lsLu1)=plr(psiBm

1

in'$r)$b(psidrQ

Mu=

Mu=/

$b'u1 L'u2)=plr('u4+u/((

9n1

/ s

psiBrQ

psiBrQ

Mu=4

Mu=

Mu=1

9n4

'u/+u1()=plr

9n

iBrQ

2

outpsiBrQ

4

outiBrQ

4

#otor#es/

Fi%ure /6" Modified 'ontents of Ca=is subsstem

0ith these &odi!ications, the Da'is and Fa'is subsyste&s will each have an additional

input port !or the $rotor value. % controller needs to be developed to generate this resistancevalue. Double*click the Induction achine odel subsyste&. $ro& the Si&ulink "ibrary

-rowser, drag and drop a new Subsyste& block into this subsyste&. "abel this subsyste&

RotorRes)trl. Double*click the RotorRes)trl subsyste&. It will contain one input portconnected to one output port. Delete the connection between the&, copy input port 4, and paste

it back in to obtain the input port 5. "abel input 4 as SS Speed 1rp&2 and input 5 as 8ower

102. "abel output 4 as Rrotor. In the Induction achine odel subsyste&, connectthe output o! the RotorRes)trl subsyste& to the !ree inputs o! the Da'is and Fa'is

blocks. )onnect the input 5 o! the RotorRes)trl 1i.e., the power2 to the output power !ro&


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60/78

1

*o$er '8(

3onstant/

+3+

/+O+

0dd

Divide/

*I's(

*ID 3ontroller

3onstant4

-./6:

/

#rotor

HSS speed 'rpm(

3onstant1

+3+

pi)4-0dd/

Divide

+O+

#1)srated

0dd1Manual S$ith

Saturation

Fi%ure /8" Blo'ks and 'onne'tions )ithin the RotorRes+trl subsstem

In $igure 6:, the value o! )onstant4 1i.e., the re!erence power in 0atts2 was set to 556;;;Lwhereas the value o! )onstant5 1i.e., the &echanical synchronous speed in radBsec2 was set to

5[(;[piB6, because the !re?uency was (; K and there were three pole*pairs 1si' poles2. The

+ain block directly a!ter the speed input was set to piB6; to convert SS speed in rp& to

radBsec. The +ain block R5BsWrated was set to a value o! ;.4


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the value o! rotor resistance 1i.e., the output o! the RotorRes)trl subsyste&2. The si&ulation

can now be run.

4.%.) Type % Turbine odel ,esults

The si&ulation results are shown in $igure 74$igure 76. $igure 75 shows the value o!

rotor resistance in ^. %!ter the initial transient, the rotor resistance reached steady*state valueat the original value o! ;.4


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To

rBue'"m(

HSSSpeed'rad)s(

*o$er'8(

1--

1---

/--

/---- /- / 1- 1 4- 4 2-

time's(

/41

/4-

/16

/15- /- / 1- 1 4- 4 2-

time's(

= /-

4

1.

1

/.

- /- / 1- 1 4- 4 2-time's(

Fi%ure 2/" Results )ith $it'h and rotor resistan'e 'ontroller $resent

-ecause o! the da&ping e!!ect !ro& the rotor resistance controller on the tor?ue oscillations, theoutput power oscillations were also da&ped. %lso, the pitch controller output shows that the

oscillations were s&aller than those shown in $igure 5:. The speed variation was larger, with an

observed &a'i&u& speed variation 1i.e., slip2 o! appro'i&ately (. %llowing this speedvariation by changing the rotor resistance s&oothed the tor?ue and power wave!or&s. These

less*oscillatory conditions are &uch !riendlier to the &echanical and electrical co&ponents o! a

turbine. This is one o! the pri&ary reasons variable*speed turbines are pre!erred in the real world.

The i&ple&ented rotor resistance controller was proven e!!ective to &odi!y the Type 4 to Type 5turbine &odel.

Dyna&ic Type 5 wind turbine &odels have also been developed using the Si&8owerSyste&s

toolbo' in Si&ulink. Despite having less utility !or acade&ic purposes than the a!ore&entioned

&odel, because the &achine characteristics are hidden, these &odels are &ore use!ul !orengineers because they can be coupled with grid and other power syste& device &odels built in

Si&8owerSyste&s. The per!or&ance o! these &odels is identical to that o! the &odel described


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or other transients2 or unbalanced grid i&pedance. The &odel developed so !ar does not account

!or these !actors, but will do so in the !uture.

Fi%ure 21" T$e / )ind turbine 'onne'tion dia%ram

Type 6 0T+s 1as shown in $igure 792 are variable*speed wind turbines with D$I+s. % D$I+ is

operated in variable*speed &ode using a partial*siKe power converter connected to the rotor

winding o! the 0RI+. The stator winding o! the 0RI+ is connected to the grid at a !re?uency o!(; K. This turbine type is probably the &ost popular type available in the &arket, and it hasbeen deployed in large nu&bers. % 0T+ is nor&ally operated between 6; slip 1i.e.,subsynchronous speed2 and *6; slip 1i.e., supersynchronous speed2, and the converter istypically at appro'i&ately 6; o! rated output power. The power converter per!or&s a back*to*back %)BD)B%) conversion using two pulse*width &odulation>switched voltage*sourceinverters coupled with a D) link. % crowbar circuit is also provided as protection, to allow

shorting the rotor circuit, i! necessary.

% Type 6 0T+ has a tor?ue characteristic that is a ?uadratic !unction o! the rotational speed.Type 6 0T+s allow &a'i&al e'traction o! wind power because their output power can be

electronically controlled to !ollow the opti&al power curve. The opti&al power curve is a cube

!unction o! the rotational speed. I! the rotor speed e'ceeds its rated value, the pitch controller&ust be deployed to li&it the rotational speed at its rated speed. I! the pitch controller cannot

control the aerodyna&ic power o! a wind turbine, a 0T+ &ay e'perience a runaway event. Note

that the speed range o! a Type 6 0T+ is &uch larger than the speed range o! a Type 4 0T+Lthus, the kinetic energy stored in the rotating blades and other co&ponents within a wind turbine

is su!!iciently large, and the output o! the generator is not i&pacted as &uch by the wind

!luctuations and turbulence because so&e o! the energy is stored and restored in the kineticenergy o! the rotating &ass.

%T"%-BSi&ulink#s Si&8owerSyste&s toolbo' provides an e'a&ple phasor &odel o! a D$I+turbine with highly si&pli!ied &echanics. 0e &odi!ied this &odel and replaced the basic

aerodyna&ic and &echanical aspects with the $%ST Si&ulink block. % top*level view o! the

&odel is shown in $igure 7(. )onsidering that the Type 6 0T+ is presently the &ost popular


65/78

turbine installed globally, a &ore detailed description o! Si&8owerSyste&s# i&ple&entation o! a

Type 6 0T+ is given in %ppendi' -.

The D$I+ 1light blue2 block &odel was previously supplied with a tor?ue input, but because

$%ST handles all the calculations !or the two*&ass 1generator and turbine2 sha!t &odel, thegenerator can be provided directly with a speed input instead. 0ithin the generator block, the

two*&ass sha!t sub*&odel was bypassed. This generator &odel does not include a crowbar or

D) chopper. % pitch control subsyste& not present in the original &odel was added as well,

based on the one designed !or the previous turbine &odels. So&e results !ro& this &odel areprovided in Section (, in which this &odel was also used to test the e!!icacy o! stress da&ping

controllers.

Fi%ure 25" T$e / )ind turbine model usin% Sim


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Fi%ure 26" T$e 2 )ind turbine 'onne'tion dia%ram

%T"%-BSi&ulink#s Si&8owerSyste&s toolbo' currently provides an e'a&ple &odel !or a

!ull*converter turbine, shown in $igure 7


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Fi%ure 28" T$e 2 turbine model usin% Sim


68/78


69/78

generally based on &a'i&iKing the energy production 1unscheduled operation2. Nonetheless, a

0T+ is controllable, although its controllability is only in one direction=curtail&ent 1i.e., it can

only generate less than the available aerodyna&ic power by a co&bination o! pitch and generatorcontrols2. %n e'ceptional case is when the turbine is de*rated, in which case it can be controlled

upward as well as downward. % 0T+ output is also predictable. 0ind variability can be

esti&ated based on wind !orecasting.

In a conventional power plant, synchronous generators are directly connected to the grid. The

electro&agnetic !lu' generated by the stator winding rotates synchronously according to the!re?uency o! the grid. There is a direct correlation between the !re?uency and voltage o! the grid

and the &echanical rotor o! the generator, which is &echanically and tightly synchroniKed to the

grid. %ny oscillation in the electrical power syste& on the grid is translated directly to theoscillation o! the generator rotor, sha!t, gearbo', and the pri&e &over. Thus, a sudden change in

the grid will have a direct i&pact on the &echanical co&ponents o! the generator and the pri&e

&over.

%ll !our 0T+ types 1i.e., !i'ed*speed, variable*slip, variable*speed, and !ull*converter2 are

nonsynchronous. This is the di!!erence between wind and conventional generators. % 0T+ hasnonsynchronous characteristics. Thus, any electrical events on the trans&ission lines will have

so&e da&ping be!ore being trans&itted to the &echanical co&ponents o! the turbines. % wind

turbine has a better &echanical co&pliance and &echanical coupling between the pri&e &overand the generator. Thus, any power spikes developed in the generator as a result o! abnor&al

events in the trans&ission line do not have to be translated directly to &echanical stresses.

Instead, they &ay be bu!!ered by a nonsynchronously*rotating 0T+, in which case so&e o! theelectrical power spikes will be converted to kinetic energy o! the generator 1and the turbine

blades2 and the e'pected da&aged can be signi!icantly reduced.

Type 6 and Type 7 0T+s operate in variable speed with a !lu'*oriented controller via power

converter. Thus, the rotor does not have to rotate synchronously with the stator !lu' created bythe grid rotating at the grid !re?uency. %ny oscillations on the power syste& grid !re?uency &aybe co&pensated by the power converter control and thus can be prevented !ro& a!!ecting the

&echanical co&ponents o! a 0T+.

$ro& a power syste& perspective, a wind power plant is usually spread across a very large area

to opti&iKe the aerodyna&ic energy capture. Thus, there are diversities within a wind power

plant. % turbine located at one corner &ay be e'posed to a high wind speed, whereas a windturbine located at another corner &ay e'perience low wind speeds. %ny !luctuations at each wind

turbine can be signi!icantly di!!erent one !ro& another. Thus, the power !luctuation at the point

o! interconnection 1where the output o! all turbines &eet be!ore trans&itted to the trans&ission

lines2 will be a lot s&oother than the output !luctuations at an individual turbine. This s&oothinge!!ect is a result o! spatial diversity within a wind power plant. Cbviously, the s&ooth output

!luctuations will have a &ilder i&pact on a power syste& than i! there is no diversity within awind power plant.

%nother diversity !ound in a wind power plant is the length o! cables connecting individualturbines to the point o! interconnection. The di!!erence in the cable lengths and the diversity in

the wind resource &ake each wind turbine e'perience di!!erent voltage drops along the cables


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1!ro& the point o! interconnection to each individual turbine2. This is actually a bene!it !or the

power syste&. %s shown in G5


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Fi%ure 1" A sim$lified $o)er sstem 'onfi%uration often used in simulatin% fault ride-throu%h'a$abilit of a turbine

1". Ele'tri'al Abnormal E3ents

-.%.1 Grid#,el"ted /ents

%bnor&al events occurring on the grid a!!ect the per!or&ance and integrity o! wind turbines.Each turbine type has its own advantages and disadvantages when !acing such events. E'a&ples

o! abnor&al events related to generators and power converters include the !ollowing@

-alanced voltage events 1e?ual undervoltage or overvoltage in the three phases2

Unbalanced voltage event 1undervoltage or overvoltage in one or two phases2

$ault transients 1three phase>to*ground !aults, single or two*phase !aults, grounded or!loating2

/oltage dips 1direct online start*up o! large induction &otors, loss o! lines or generations2

8ower syste& oscillations 1inter*area, intra*area, sub*synchronous, etc.2

Switching transients 1capacitor switching, load switching, stuck breakers, tap changertrans!or&er2

%lthough not listed here, an additional e'a&ple de&onstrated in Section ( &ay also e'acerbate

the i&pact on a 0T+ !or di!!erent grid conditions 1sti!! versus weak, balanced versusunbalanced, undervoltage versus overvoltage, steady versus oscillating !re?uency2, di!!erent

levels and types o! reactive co&pensation 1active versus passive co&pensation2, di!!erent typesand the winding connections o! the trans!or&ers, and obviously di!!erent types o! 0T+s.

-.%.% Gener"tor "nd Poer +on/erter,el"ted /ents

%bnor&al events occurring in the generator and power converter also a!!ect the per!or&ance and

the integrity o! wind turbines. The types o! generators, power converters, and control syste&s


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a!!ect a wind turbine operation, and power syste& stability. E'a&ples o! abnor&al events related

to grids include the !ollowing@

Unbalanced i&pedance

Unbalanced phase windings,1e.g., because o! inter*turns shorts2

$ault transients 1three phase>to*ground !aults, single or two*phase !aults, grounded or!loating2

I&balance between input and output power !lowing through the D) bus because o! losso! lines

8ower*switching !ailures and the corresponding D) bus !luctuations

D) bus protection with dyna&ic braking, di!!erent types o! storage, capacitor !ailures

1"/ Me'hani'al and Aerodnami' Abnormal E3ents

%bnor&al events developed because o! the wind resource, &echanical vibrations o! the turbine

blades or other co&ponents, and turbine controls &ay i&pact the grid and a!!ect the per!or&ance

o! wind turbines. E'a&ples o! abnor&al events related to aerodyna&ic and &echanical

co&ponents include the !ollowing@

-lade pitch actuatorBcontrol sluggishness and unbalanced pitch control response

Runaway conditions resulting !ro& !ailure o! pitch actuatorBcontrol or brake &echanis&

Uncontrollable ra&ping, a sudden loss o! wind, and other e'tre&e aerodyna&ic inputperturbations

Severe wind turbulence

1"2 Wind Turbine Re?uirements

-.4.1 Grid Inter*"'e ,e2uirement

In the early develop&ent o! wind power, the level o! wind power penetration into the grid is very

low. $or an abnor&al condition on the grid 1under* or overvoltage, !re?uency dip, etc.2, a windturbine is allowed to be disconnected !ro& the grid to ensure that a wind turbine will not be

har&ed by the abnor&al grid condition. Early standards !or grid inter!ace re?uire&ents were

covered in the Institute o! Electrical and Electronics Engineers 497A, applicable !or generationsless than the 5;*0 power rating.

+/#/!/! 7oltage3Relate' Re0&ire$ent

%s wind power plants and the level o! wind power penetration increases, the generated output

power is considered signi!icant to the overall generation pools. %s such, the trans&ission

operator re?uires that a wind turbine stays connected under general disturbance. Thisre?uire&ent is re!lected in the $ederal Energy Regulatory )o&&ission Crder ((4 and ((4%, also

known as low*voltage ride*through and !ault ride*through capability. This re?uire&ent covers

both the voltage and !re?uency envelope that re?uires a wind turbine to stay connected to the

grid. -eyond or outside this envelope, the turbine is allowed to be disconnected !ro& the grid.


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!orti!ication o! turbine co&ponents. The electrical aspects can utiliKe several &odules available

in Si&ulink, such as Si&8owerSyste&.

-.4.% le'tri'"l +omponent ,e2uirement

Electrical co&ponent re?uire&ents are &ostly on voltage and current li&its. The voltage li&it is

related to the level o! dielectric and insulation necessary to withstand the electrical !ield i&posedon the&. The voltage blocking capability o! a co&ponent is speci!ied in the data sheet, and the

co&ponent &ust be protected !ro& operating beyond the allowable voltage range. The current

li&it is usually related to the a&ount o! current passing through the device without generating so&uch heat that it will degrade the dielectric and insulation o! the co&ponents. The electrical

co&ponents that !or& the linkages to convert and trans!er &echanical energy into electrical

energy to custo&ers &ust be care!ully designed to bear the loads and stresses o! the process.

The rise o! te&perature above a critical point 1speci!ied in the data sheet2 can be very da&aging

1irreversible degradation2 to the electrical insulation and &agnetic characteristics. There?uire&ents !or electric &achines 1rotating &achineries, trans!or&ers, inductors, etc.2 are

usually easier to &aintain because the technology, the siKe o! the &ass to store and conduct

ther&al losses to the a&bient air, the au'iliary e!!orts to dissipate the heats, and the!ilteringBscreen o! the dust are very well established. %lso, electric &achines can better tolerate

overloads 1overcurrent2 and overvoltage conditions. owever, the power electronic co&ponents

1I+-T, diodes, etc.2 are very sensitive to the te&perature because the electronic co&ponents arebased on p*n 3unction. The bottleneck in electrical co&ponents is &ostly dictated by the power

electronic design ratings 1voltage and current2.

-ecause &odern wind turbines &ust provide a good grid inter!ace, the i&pact o! providing !ault

ride*through capability and providing other ancillary services &ust be investigated to ensure that

these re?uire&ents will not shorten the li!espan o! the electrical co&ponents o! a turbine and tobetter understand how grid inter!ace re?uire&ents will drive the !uture design o! wind turbines.

-ecause re?uire&ents di!!er !ro& region to region, it is probable that the sa&e turbine types will

be built at di!!erent enhance&ents to keep the costs o! turbines as a!!ordable as possible.

-.4.) nergy#3"r/esting ,e2uirement

The &ain purpose o! wind generation is to harvest as &uch energy as possible as soon as thewind speed available increases above the cut*in wind speed. a'i&u& power point tracking is

generally i&ple&ented indirectly through passive &apping o! output power co&&anded to the

power converter to the rotational speed o! turbine rotor. -ecause the grid inter!ace re?uire&enta!!ects the reliability o! a power syste&, and electrical disturbances usually last !or a very short

ti&e, the grid inter!ace controller takes precedence over the &a'i&u& power point tracking

operation controller.

%s wind power penetration levels increase, there will be ti&es when the output o! a wind power

plant &ust be reduced to &aintain the reliability o! a power syste&. This is called curtail&ent,and it is a co&&on practice when the available trans&ission capacity o! the trans&ission lines is

e'ceeded. )urtail&ent is also needed when the output power o! a conventional generator !alls

short o! its &ini&u& because the wind power is high but the load connected to the grid is low.This condition o!ten occurs at nights. )urtail&ent &ight also be pro!itable when the cost o!

energy to operate as spinning reserves is su!!iciently higher than generating the output power at


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nor&al operation. The spinning reserve operations o! 0T+s have been discussed and published

in several papers G66H.

-ecause curtail&ent as a spinning reserve is not currently co&&on practice, the i&pact o! this

operation on the stresses and strains on &echanical and electrical co&ponents o! a wind turbineneeds to be investigated.

-.4.4 e'("ni'"l +omponent ,e2uirement

echanical co&ponents o! wind turbines are the &ain path to trans!er wind energy into electrical

energy. The &echanical link between the turbine rotor and generator are &ostly the blades, low*

speed sha!t, gearbo', yaw drives, and the generator high*speed sha!t. The &echanical linkagesare very rigid, and the conversion o! &echanical energy into electrical energy occurs via

electro&agnetic conversion at the air gap o! the generator.

%ll the a!ore&entioned re?uire&ents &ay i&pact the &echanical co&ponents linked together to

convert aerodyna&ic input power !ro& the wind into &echanical power into electrical output

power. The tools presented in this report will be able to si&ulate the i&pact on &echanicalco&ponents. ost o! the &echanical co&ponents are si&ulated in $%STL thus, the output data

representing the stresses and strains on each o! the sub*co&ponents &odeled in $%ST can be

e'ported, plotted, and co&pared to the base case. %n additional detailed gearbo' &odel built inSi&ulink can be readily asse&bled to replace the si&ple &odel available in $%ST. This &odel is

e'plained in %ppendi' %.

1"1 #esi%nin% +ontrols to Miti%ate ,m$a'ts

The overall energy !low diagra& o! wind power generation is illustrated in $igure 95. The input

energy is the kinetic energy stored in the wind. The wind drives the &echanical linkage that

converts wind energy into &echanical energy, and the electrical linkage converts &echanical

energy into use!ul electrical power !ro& a wind power plant to the energy consu&ers viatrans&ission and distribution lines.

Win

d

spee

d

Me c han ic a l

L i n k age

Electromechanical

Conversion

E l e c t r i c a l L i n k age

Aeromechanic

Conversion

Electric

Power

Fi%ure 1." A sim$lified dia%ram sho)in% 3arious linka%es and the $o)er flo) in a )ind $o)er$lant


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+/+//! ri' %i'e3Trans$ission Lines

any events &ay occur at the grid as results o! natural causes 1lightningL short circuits caused by

!alling trees or ani&alsL shorted, sagging lines caused by high winds, etc.2 or &an*&ade events1capacitor switching, loss o! lines during !ault clearing, loss o! generators, loss o! loads, etc.2.

These events &ay create overload currents, over* and under*voltages, or nor&alBunbalanced

voltages. ost severe events in trans&ission lines can be ?uickly re&oved by activating thecircuit breakers to &ini&iKe the a!!ected lines andBor custo&ers. owever, be!ore being cleared,the abnor&al event &ay be severe enough that it creates irreversible da&age on the turbine

co&ponents 1the gearbo', generator, power converters, etc.2, especially i! the event creates

tor?ue or voltage spikes. Cther, less*severe events, such as unbalanced voltage, &ay gounnoticed !or a longer duration than acceptable because they are undetected by the sensors and

relay protection is not triggered. These events &ay not cause instant !atal e!!ectsL however, i! le!t

uncorrected, the tor?ue pulsations and une?ual heating in the generator#s stator windings &aylead to catastrophic !ailures.

+/+// Point of 1nterconnection


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