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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 $$$.nrel.gov)publiations.
Te'hni'al Re$ort"#E&)T*+,D--+,./.,
0pril 1-/2
3ontrat "o. DE+0345+-6G7164-6
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Simulation for Wind TurbineGeneratorsWith FAST andMATLAB-Simulink Modules
M. Singh, E. Muljadi, J. Jonkman,and V. GevorgianNational Renewable Energy Laboratory
I. Girsang and J. DhupiaNanyang Technological University
*repared under Task "os. 8E//.-445 and 8E/2.49-/
NREL is a national laborator of the !"S" #e$artment of Ener%&ffi'e of Ener% Effi'ien' ( Rene)able Ener%&$erated b the Allian'e for Sustainable Ener%* LL+
This report is available at no ost !rom the "ational #ene$able Energ%&aborator% '"#E&( at $$$.nrel.gov)publiations.
"ational #ene$able Energ%&aborator%/-/4 Denver 8est *ark$a%Golden, 37 6-2-/4-4+1:+4--- ; $$$ .n rel.g o v
Te'hni'al Re$ort"#E&)T*+D--+/
0pril 1-/2
3ontrat "o. DE+0345+-6G7164-6
http://www.nrel.gov/publicationshttp://www.nrel.gov/publicationshttp://www.nrel.gov/http://www.nrel.gov/publicationshttp://www.nrel.gov/7/25/2019 TURBINA DE VIENTO
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N&T,+E
This report $as prepared as an aount o! $ork sponsored b% an agen% o! the
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iii
Thisreport is available at no ost !rom the "ational #ene$able Energ% &aborator% '"#E&( at $$$.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 $atigue,
%erodyna&ics, Structures, and Turbulence &odel with the e'ternal drivetrain &odel, especiallyas related to Section (.
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iv
Thisreport is available at no ost !rom the "ational #ene$able Energ% &aborator% '"#E&( at $$$.nrel.gov)publiations.
List of A'ronms)%E co&puter*aided engineeringD$I+ doubly*!ed induction generator
$%ST $atigue, %erodyna&ics, Structures, and Turbulence
&odel+R) +earbo' Research )ollaborative
SS high*speed sha!t
I+-T insulated*gate bipolar transistor
"SS low*speed sha!t%T"%- atri' "aboratory
NRE" National Renewable Energy "aboratory
SD) stress da&per controller /ID) virtual inertia and da&ping control
0RI+ wound*rotor induction generator
0T+ wind turbine generator
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v
Thisreport is available at no ost !rom the "ational #ene$able Energ% &aborator% '"#E&( at $$$.nrel.gov)publiations.
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. $irst, the &odel can be si&ulated under di!!erent
wind and grid conditions to yield !urther insight into the drivetrain dyna&ics in ter&s o!predicting possible resonant e'citations. Second, the tool can be used to si&ulate and
understand transient loads and their couplings across the drivetrain co&ponents. Third, the
&odel can be used to design the various !le'ible co&ponents o! the drivetrain such thattrans&itted loads on the gearbo' can be reduced. Several case studies are presented as e'a&ples
o! the &any types o! studies that can be per!or&ed using this tool.
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vi
Thisreport is available at no ost !rom the "ational #ene$able Energ% &aborator% '"#E&( at $$$.nrel.gov)publiations.
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
Gen speed $rt &SS '#*M( GenTrB, Ele*$r
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(
?lade *ith 0ngles 'rad(
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 ðods, 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.
Gen speed $rt &SS '#*M( GenTrB, Ele*$r
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! $igure 4:, three voltage signals were generated, which took the !or&
o! =
((((((((((((((( + ). The signals were ti&e*shi!ted by 45;Y !ro& each other, with 4
taking the
values o! ;Y, *45;Y, and Z45;Y !or phases a, 5, and / respectively. The three*phase voltageswere
then trans!or&ed into two orthogonal vectors 1d*a'is and 6*a'is2 and a D) co&ponent 1;*a'is2
using the d6; trans!or&ation, also known as 8ark#s trans!or&ation, the details o! which can be
!ound in Analsis o" le/tri/ a/*iner by 8.). rause 1c+raw*ill 4::
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Cnce co&!ortable with S1.mdl, the reader can proceed to inter!acing this &achine &odel with$%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
?lade *ith 0ngles 'rad(
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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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 $igure 57. %n
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3lok
Time
To 8orkspae3onstant1
-
Sel et &SS speed at entrane to gearbo= 'rpm(
3lok input
0ddGen TorBue '"m( and *o$er '8( Gen. TorBue '"m( and *o$er '8(
3onstant
2 S$ith
&SS Speed input 'rpm(
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
?lade *ith 0ngles 'rad(
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"
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TorBu
e'"m(
HSSSpeed'rad)s(
*o$er'8(
3l ok
T i me
T o 8orkspae3onstant1
-
Sel et &SS speed at entrane to gearbo= 'rpm(
3lok input
0ddGen TorBue '"m( and *o$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 Dat a 7utData
+O+
T ermi nator7ut/
Ca$ 3ontrol l er
In/7ut/
?lade *ith 0ngles 'rad(
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
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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 /"
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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&. $ro& the Si&ulink "ibrary
-rowser, drag and drop a new Subsyste& block into this subsyste&. "abel this subsyste&
RotorRes)trl. Double*click the RotorRes)trl subsyste&. It will contain one input portconnected to one output port. Delete the connection between the&, copy input port 4, and paste
it back in to obtain the input port 5. "abel input 4 as SS Speed 1rp&2 and input 5 as 8ower
102. "abel output 4 as Rrotor. In the Induction achine odel subsyste&, connectthe output o! the RotorRes)trl subsyste& to the !ree inputs o! the Da'is and Fa'is
blocks. )onnect the input 5 o! the RotorRes)trl 1i.e., the power2 to the output power !ro&
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1
*o$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 $igure 7(. )onsidering that the Type 6 0T+ is presently the &ost popular
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turbine installed globally, a &ore detailed description o! Si&8owerSyste&s# i&ple&entation o! a
Type 6 0T+ is given in %ppendi' -.
The D$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
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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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