paper-22 sc-b4 2013 madeira bp02 final revised

8/11/2019 Paper-22 SC-B4 2013 Madeira BP02 Final Revised

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16 3ntroduction

The use of hi#h volta#e direct current .HVD0 technolo#y for transmission of hi#h amounts of ener#y

in the Bra9ilian po%er system $e#an in the middle of the :;1s %ith the operation of the transmission

system associated to 311M5 throu#h t%o $ipoles E!

Today the most important HVD transmission application in Bra9il is that related to the Rio Madeira

hydroelectric #eneration compleC' %hich is located in Rondonia state and comprises t%o $ul" po%er

plants( Santo Antonio .3?1 M50 and Firau .3G?1 M50! Due to severe environmental constraints' one

of the main characteristics of the Rio Madeira #eneration compleC is the run/of/river desi#n %ith very

small reservoirs!


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$6 S,stem Enineerin Studies and 4esin %s!ects o# Bi!ole $

$616 Basic Con#iuration

Bipole 2 employs a confi#uration %ith one converter per pole' each converter consistin# of a sin#le

t%elve/pulse thyristor $rid#e! Since the scheme is optimi9ed for po%er flo% direction from -orto

Velho to Arara&uara' the converter transformers and thyristor valves at the t%o ends are not identical!A harmonic filters are installed at $oth converter stations to limit the volta#e distortion levels to the

re&uired limits %hile providin# reactive po%er to compensate for the converter consumption 3EGE!

+n the D side' smoothin# reactors are connected to the HV and JV $uses to reduce the D current

ripple and limit incomin# li#htnin# overvolta#es! Harmonic filters are also provided on the D side to

prevent interference %ith open/%ire communication circuits ?E!

A sin#le/line dia#ram of Bipole 2 HVD transmission scheme is presented in 6i#ure !The "ey

components and su$/systems are sho%n in the fi#ure!

Fiure 1 7 Basic con#iuration o# Bi!ole $

$6$6 Main Scheme 'arameters

The scheme is desi#ned to transmit continuously full rated po%er of 3?1M5 from -orto Velho to

Arara&uara >E! Additionally' a 31 minute overload ratin# of G22> M5 .!33pu0 and a ? second

overload ratin# of G=>GM5 .!?pu0 are availa$le! To allo% for D current and D volta#e

measurement errors the e&uipment is desi#ned for a continuous overload ratin# of 3;2 M5! The

short/time overload capa$ility is important for some transmission contin#encies and to allo% the use

of D po%er modulation for system fre&uency sta$ili9ation after faults! The 31 minute overload ratin#

is only availa$le %ith the redundant coolin# system in service and %as specified to permit the outa#e

of one pole %ithout D po%er transmission reduction!

Althou#h the normal po%er flo% direction is from -orto Velho to Arara&uara' the HVD scheme is

also desi#ned to operate in reverse po%er' from Arara&uara to -orto Velho' %ith a limited po%er ratin#

of 2:G;M5' a 31 minute overload ratin# of 3:?2M5 and a ? second ratin# of GG?GM5!

Durin# conditions of %ea" insulation in the D line .or associated e&uipment0' the scheme is capa$le

to operate at a reduced D volta#e of =1K .G21 "V0! After three unsuccessful restart attempts from

D line faults' the affected pole s%itches to this mode automatically $efore performin# the last

attempt! The D volta#e order of the healthy pole is not affected! This feature is also used to force the

converters to operate under hi#h reactive po%er a$sorption conditions to provide an additional de#ree

of functionality to the A net%or"s' especially at li#ht load conditions! 5hen used for this purpose'

the operatin# mode is called Hi#h MVAr +peration and the D volta#e can $e set at any value

$et%een G21 "V and >11 "V! Under =1K D volta#e conditions the maCimum po%er transfer is222>M5!


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to operate at hi#h firin# an#les com$ined %ith an eCtended ran#e of the tap/chan#er is used for this

special mode of operation!

A num$er of circuit confi#urations are provided(

Bipolar .-3 on J3 and -G on JG0

Monopolar %ith #round return .-3,J3 or -G,JG out of service0

Monopolar %ith metallic return .Leutral of -3 on JG or Leutral of -G on J30

-aralleled converters .-,,-3 and,or -2,,-G0

-aralleled transmission lines .J,,J3 and,or J2,,JG0

rossed line .-3 on J or -G on J20

-aralleled neutral $us onto a sin#le #round electrode

The necessary s%itches .not sho%n in 6i#ure 0 and interloc"s to implement all the re&uired

confi#urations are provided! These confi#urations can $e com$ined %ith a ran#e of operatin# modes

such as reduced volta#e operation' reverse po%er operation and various overload conditions!

The main circuit calculations for e&uipment ratin# and operation characteristics %ere performed usin#

the AJST+Ms in/house soft%are pac"a#e +LAD .onverter omputer Aided Desi#n0! The full

ran#e of system fre&uency and A volta#e %ere considered in the calculations! The follo%in#

important &uantities %ere determined $y these calculations(

The reactances of the converter transformers in connection %ith the valve stress re&uirementsN

The commutation volta#e as function of the D current for the various operation modes and

the rated po%er and volta#e of the converter transformersN

The ran#e and step si9e of the JT of the converter transformersN

Active and reactive po%er on the A $us as function of D currentN

ontrol an#les ran#es!

$66 2h,ristor 8al9es

Bipole 2 %ill $e e&uipped %ith the HG11 Series thyristor valve' %hich is the latest ran#e of thyristor

valves for HVD converter applications developed $y AJST+M =E!


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The total num$er of thyristor levels considerin# $oth stations is 3;>G .::2 at -orto Velho and ;=2 at

Arara&uara0!

Fiure $ 7 :: 9al9e module housin t;o 9al9e sections Fiure 7 4ou-le9al9e structure

$66 Con9erter 2rans#ormers

Sin#le/phase t%o/%indin# converter transformers are used in $oth converter stations of Bipole 2! *ach

pole consists of > transformer units' 3 of them connected as Y/Y in a three/phase $an" and three of

them connected as Y/in a three/phase $an"! There is one spare unit of each type per station! The A.line0 side of the transformers is connected $y outdoor oil,air $ushin#s %hile the D .valve0 side is

connected $y indoor $ushin#s' directly into the valve hall! The coolin# is provided $y G C 33K .33K

redundancy0 oil,air $last coolers mounted on the tan" structure! The transformers are e&uipped %ith

%ide ran#e on/load tap/chan#ers .+JT0 located in the neutral of the A/side %indin#s!

A summary of the main data of the converter transformers at $oth stations are #iven in Ta$le ! A

photo#raph of a YY transformer unit for Arara&uara station at the factory is sho%n in 6i#ure G!

2a-le 1 7 Main data o# con9erter trans#ormers

Fiure 7 %rara


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Bipole 2 corresponds to =1? MVAr! At Arara&uara the reactive po%er $alance is entirely covered $y

the e&uipment %ithin the station!

Different approaches have $een used for each of the t%o terminals re#ardin# the consideration of

measurement errors and e&uipment tolerances! At the -orto Velho side' %orst/case errors' tolerances

and %orst/case steady/state D volta#e and firin# an#le %ithin the normal ran#e for tap/chan#er

action have $een used! Besides' maCimum D side resistance has also $een specified! At Arara&uaraside' measurement errors have not $een considered! Ho%ever' transformer reactance tolerance'

minimum D side resistance and %orst/case D volta#e %ithin the normal ran#e have $een used!

The maCimum si9e of an individual su$/$an" %as defined to comply %ith the specified maCimum

volta#e chan#e after s%itchin# of ?K for the lo%est short/circuit level at the A $us! Besides' the su$/

$an" si9es %ere specified so there is no ris" for self/eCcitation under any eCpected operatin# condition!

MVAr %as necessary! 6i#ure ?

sho%s the physical arran#ement of the reactive compensation elements! 6i#ure >and6i#ure = sho%

the reactive po%er eCchan#e %ith the A net%or" for the specified assumptions for -orto Velho and

Arara&uara' respectively!

.a0 .$0

Fiure . 7 &eacti9e !o;er com!ensation arranement> (a) 'orto 8elho? (-) %rara


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$6@6 %C Filter 4esin

A harmonic filters are specified at $oth converter stations to maintain the harmonic distortion levels

%ithin the specified limits' prevent interference %ith near$y communication systems and to provide

the necessary reactive po%er to compensate for the converter consumption 3E!

A simple solution consistin# of four $road/$and H-2,2G dou$le/tuned filters .G C 31? MVAr0 plus

t%o shunt capacitors .2 C 3> MVAr0 %as adopted at Arara&uara' since this is a relatively stron#

system %ith reasona$ly %ell/damped A net%or" harmonic impedance! There %as no need for lo%er

order filterin#! At -orto Velho' a more compleC filter confi#uration %as used due to the very lo%

dampin# of the A net%or"! This net%or" consists only of #enerators' step/up transformers and

connectin# lines %ith no local load! The total num$er of machines can vary over a %ide ran#e' %ith

different connection confi#urations' #ivin# a %ide ran#e of possi$le net%or" harmonic impedance! (a) 'orto 8elho? (-) %rara


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of 2K and the effect of pre/eCistin# harmonics in the net%or" .$ac"#round harmonics0! The pre/

eCistin# harmonics %ere considered as harmonic volta#e sources directly connected to the filter $uses!

$6A6 4C Filter 4esin and Smoothin &eactor

Air/cored air/cooled smoothin# reactors are used' split

into three units! The maor part is installed on the neutralside in t%o units of ?1mH each' %hile one ?mH unit is

placed on the hi#h volta#e side of the converter to limit

possi$le incomin# li#htnin# overvolta#es! This non/

conventional arran#ement %as chosen for reasons of

economy and insulation co/ordination and had a maor

impact on the D filter desi#n and inductive co/

ordination! D harmonic filters connected at the hi#h/

volta#e and neutral $uses have $een provided on $oth

converter stations to limit the interference %ith

telecommunication circuits to accepta$le levels ?E!


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The co/ordination $et%een the po%er and communication studies confirmed the


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performance' volta#e and fre&uency control on the A net%or" and dampin# of lo%/fre&uency

oscillation are the main focus of the study! A num$er of tests are studied' includin# step responses'

transformer and filter s%itchin#' converter $loc"in# and A,D system faults to demonstrate the

performance of the HVD scheme under various system conditions!

Three types of studies are performed( fundamental fre&uency dynamic performance .transient

sta$ility0' -SAD dynamic performance and real/time di#ital simulation .RTDS0 dynamicperformance!

6undamental 6re&uency Dynamic -erformance Study

This study %as performed usin# full A net%or" representation and a detailed fundamental fre&uency

dynamic model of the HVD controls for Bipole 2 ;E!Typical models of ABB controls for Bipole

and Bac"/to/Bac" %ere used!

-SAD Dynamic -erformance Study


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o$served durin# the fault period .for non/$olted faults0 and durin# the first cycles after fault

clearin#' de#radin# the commutation mar#in! The amma 4ic" function %as then introduced

to eCtend the commutation mar#in and thus minimi9e the ris" of commutation failures durin#

recovery!

S%itch the volta#e order to :1K after faults ) This strate#y %as introduced to improve the

sta$ility of inverter control after recovery from faults! 5hen D volta#e collapses .e!#! faultson $oth terminals0 the D volta#e order is suddenly chan#ed from 11K to :1K! The ramp/up

to the ori#inal value is performed very slo%ly at a rate of 1!12pu,s so the volta#e order is

maintained at a$out :1K for the %hole period of fault and recovery! This is done to maintain

the inverter in D volta#e control %ith a lo%er reference value .rather than s%itchin# to

constant M


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B11"V Associado [s Usinas do Rio Madeira *studos da ompensaIo de-ot\ncia Reativa das *sta]es onversoras do Bipolo 2O .in -ortu#uese0' -roceedin#s of ZZ

paper-22 sc-b4 2013 madeira bp02 final revised

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