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Applications
of
the
GPTR
Contents
TheGPTRinanAutomaticTestEquipmentorSimulationenvironment..................................2
How
the
GPTR
changes
values
for
voltages
and
currents?
.......................................................
4
WhytheGPTRincludesaGridAnalyzer?..................................................................................4
UseofGPTRforcheckingGridAnalyzers..................................................................................5
HowtocontroltheGPTR?.........................................................................................................6
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TheGPTRinanAutomaticTestEquipmentorSimulation
environment
TheGPTRisalaboratoryprogramable3phasegridgeneratorwhereyoucancontrolthe
frequency(common),theamplitude
ofeachphaseandthephaseangleofeachphase(2nd
and3rd
respecttothefirst).Atthesametimeitprovides3currentgenerators,synchronous
withthevoltagegeneratorsforeachphase,intherangeof0to5amps,whereyoucan
controltheamplitudeofeachcurrentgeneratorandthephaseanglerespecttothefirst
voltagegenerator.Thepurposeofthese3currentgeneratorscanbebetterunderstood
consideringtheapplicationsoftheGPTR.
OriginallytheGPTRwasdevelopedforthecreationofareal3phasegridwhoseparameters
couldeasily
be
changed
through
programming.
Consider
asimplified
connection
of
agenerator
ormotororconvertertothegrid,asinnextfigure.
R
S
T
Generator
Or
Motor
Electromechanicaloperational
devices
(Contactors,switches,protection
relays,etc)
ElectronicControlDevices
(PLCs,embeddedcomputers,etc)
GRID
Thatdiagram,typically,canbesplittedasinnextfigure.
Fig2Realenvironment
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WhereanElectronicControlpartreceivesthestatusoftheelementsinthepowerwires
(contactors,IGBTs,etc),andgeneratesignalstocontrolthem,whilemonitoringtheoverall
installationthroughmeasuringthevoltagesineachphaseofthegridaswellasthecurrent
flowingthroughthepowerwires.
Thatschematicappliestoanymoderninstallationgoverningamotororageneratorora
powerconverter.Havingthisinmind,nextfigureshowswheretheGPTRfitsin.
ElectronicControl
(PLCs,embeddedcomputers,etc)
Status
lines
Control
lines
Voltages
Currents
Fig3Test,debuggingandvalidationenvironment
TypicallytheElectronicControl,whetherimplementedusingaPLC,anembeddedcomputer,
wiredlogic,etc,performssophisticateddecisionsbasedofalgorithmsembeddedonit.Actual
testsofthesealgorithmscanbequitecumbersomeattimes,aswellaselectricaltestingofthe
signalsgoingoutofthisControl.Ontopofthat,theseinstallationsaretypicallyhighpowerand
highvoltage,sotheactualtestsinarealsituationisfurthercomplicatedduetohuman
securityissues,flexibilityinthesettingofspecifictestsituations,etc.
ThesignalsenteringtheElectronicControlcorrespondingtothegridvoltageshavelow
consumption(just
for
measuring),
sometimes
using
step
down
transformers
(in
medium
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voltageinstallations).Thecurrentsflowingthrougheachphasearenormallystepdownto1A
or5Arangeusingcurrenttransformers.
Soasolutionforthetestingofalgorithmsanditsparameters,aswellasforfunctionaltestof
theElectronicControlintheseinstallationscanbeimplementedwithatestjigsimilartothe
describedintheformerfigure,wheretheactualgridisreplacedbytheGPTR.Thissolutionhas
anumberofadvantages:
1.
Itisverysavedenvironment,asallthelineswithhighvoltageareprotectedbytripping
circuitsforhighcurrents.
2.
Itisveryeasytoproduceconditionsandsequencesofconditionsdifficulttogenerate
otherwise.
Intherealcase,thecurrentsinthepowerlinesaresuppliedbythegridandcorrespondto
theresponseoftheconnectedpowerdevice(generator,motor,etc):i.e.,foragivenvoltage
thecurrentinthatlinewilldependsonthecharacteristicsofthegenerator,motor,etc.
Instead,withtheGPTRthecurrentsactuallysuppliedtotheElectronicControlarecontrolled
independentlyofthevoltagesandareseparatedofthem,whatmeansthattheGPTRcan
presenttotheElectronicControlanarbitraryloadorgeneration(fourquadrants).
HowtheGPTRchangesvaluesforvoltagesandcurrents?
Thereare
two
key
concepts
to
remember:
a)
Allchangesareproducedwhenthecorrespondinglinecross0V.Thisistominimize
thetransienteffectsofswitchinginthetransformerassociatedtoeachgeneratorin
theGPTR.
b)
Thereisaslopeofchangeparameterspecificforeachgenerator,bothrisingand
falling.
Similarlywhenthesetvalueislowerthantheactual,thesamealgorithmisused,butusingthe
valuesoftheslopeofdownchangeparameter.
WhytheGPTRincludesaGridAnalyzer?
Tobeabletocalibratethevaluesofthegeneratorsatanymoment,aftersettingthese
values.Seenextfigurethatshowsadetailedblockdiagram.
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Fig4GPTRblockdiagram
CalibrationoftheGPTRgeneratorsisdonewiththecommandCalibrationatanymoment.In
practiceyoushouldexecutethiscommandonlywhentherehasbeenachangeintheloadof
anygenerator,eithervoltageorcurrent.
UseofGPTRforcheckingGridAnalyzers
OneapplicationfortheGPTRisthecalibrationorcheckingofcalibrationofanexternalGrid
Analyzer.(Seenextfigure).
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GridAnalyzer
Under
Test
HowtocontroltheGPTR?
Thisisdonebyprogramming(thereisnomanualbuttonsintheGPTR),throughASCII
commandsthataresenttotheGPTRviaaRS485line.
Toeasethatprogramming,theGPTRissuppliedwithaVisualBasiccompatibleDLL,hence
usablewithanyVBAprogrammingenvironment,suchasExcel.AlsoincludedisanExcel
Workbook,withthesourcecode,thatcanconstitutesaverygoodstartingpointforthe
developmentof
aATE
(Automatic
Test
Equipment)
that
use
the
GPTR
and,
potentially,
any
othercontrollingsoftwareforthecontrolofadditionalhardwarethatmaybeneeded.Youcan
downloadthisExcelWorkBookdocumentationhere(http://www.acm
sl.com/ingenieria/instrumentation/3phasegridsubsystems/gptr3phasegridgeneratorand
loadsimulator/ExcelGPTR_Commandv1.pdf).NextfigureshowsthestartingUIforthis
application.
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ThisExcel
application
computes
and
presents
additional
information
about
powers,
power
factors,statusofthecommunicationschannelandstatusoftheloadsconnectedtotheGPTR.
I.e.ifacurrentgeneratorisdisconnectedfromitsload,thecorrespondingcellinthe
worksheetwillchangecolor.
Ofcourse,theusercanuseallthecomputingandstoragecapabilitiesofExceltodevelop:
Specificsequencesforeachgenerator (voltageorcurrent)
Graphicalrepresentationoftheresultsofthosesequences.
Storageof
test
patterns
and
their
results
for
further
study.
