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JOURNAL OF ENERGY TECHNOLOGY
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VOLUME 3 / Issue 3
RevijaJournalofEnergyTechnology(JET)jeindeksiranavnaslednjihbazah:INSPEC,CambridgeScientific Abstracts: Abstracts in New Technologies and Engineering (CSA ANTE), ProQuest'sTechnologyResearchDatabase.The JournalofEnergyTechnology (JET) is indexedandabstracted in the followingdatabases:INSPEC
,CambridgeScientificAbstracts:Abstracts inNewTechnologiesandEngineering (CSA
ANTE),ProQuest'sTechnologyResearchDatabase.
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Uredniki/COEDITORS
JurijAVSEC
GorazdHREN
MilanMAR
I
IztokPOTR
JanezUSENIK
JoeVORIJoePIHLER
Urednikiodbor/EDITORIALBOARD
Prof.dr.JurijAVSEC,
UniverzavMariboru,Slovenija/UniversityofMaribor,Slovenia
Prof.ddr.DenisONLAGI,
UniverzavMariboru,Slovenija/UniversityofMaribor,Slovenia
Prof.dr.AntonJEZERNIK,
Fakultetazaindustrijskiineniring,Slovenija/Facultyofindustrialengineering,SloveniaProf.dr.RomanKLASINC,
TechnischeUniversittGraz,Avstrija/GrazUniversityOfTechnology,Austriar.IvanAleksanderKODELI
InstitutJoefStefan,Slovenija/JoefStefanInstitute,SloveniaProf.dr.JurijKROPE,
UniverzavMariboru,Slovenija/UniversityofMaribor,Slovenia
Prof.dr.AlfredLEIPERTZ,
UniversittErlangen,Nemija/UniversityofErlangen,Germany
Prof.dr.BranimirMATIJAEVI,SveuiliteuZagrebu,Hrvaka/UniversityofZagreb,CroatiaProf.dr.MatejMENCINGER,
UniverzavMariboru,Slovenija/UniversityofMaribor,Slovenia
Prof.dr.GregNATERER,
UniversityofOntario,Kanada/UniversityofOntario,Canada
Prof.dr.EnrikoNOBILE,
UniversitdegliStudidiTrieste,Italia/UniversityofTrieste,ItalyProf.dr.IztokPOTR,
UniverzavMariboru,Slovenija/UniversityofMaribor,Slovenia
Prof.dr.AndrejPREDIN,UniverzavMariboru,Slovenija/UniversityofMaribor,Slovenia
Prof.dr.AleksandarSALJNIKOV,
UniverzaBeograd,Srbija/UniversityofBeograd,SerbiaProf.dr.BraneIROK,
UniverzavLjubljani,Slovenija/UniversityofLjubljana,Slovenia
Doc.dr.AndrejTRKOV,
InstitutJoefStefan,Slovenija/JoefStefanInstitute,SloveniaProf.ddr.JanezUSENIK,
UniverzavMariboru,Slovenija/UniversityofMaribor,Slovenia
Prof.dr.JoeVORI,UniverzavMariboru,Slovenija/UniversityofMaribor,Slovenia
Doc.Dr.PeterVIRTI,
UniverzavMariboru,Slovenija/UniversityofMaribor,Slovenia
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Prof.dr.KoichiWATANABE,KEIOUniversity,Japonska/KEIOUniversity,JapanDoc.dr.TomaAGAR,UniverzavMariboru,Slovenija/UniversityofMaribor,SloveniaDoc.dr.FrancERDIN,UniverzavMariboru,Slovenija/UniversityofMaribor,Slovenia
Tehnikapodpora/TECHNICALSUPPORTTamaraBREKO,
SonjaNOVAK,
JankoOMERZU;
Izhajanjerevije/PUBLISHINGRevijaizhajatirikratletnovnakladi300izvodov.lankisodostopninaspletnistranirevije
www.fe.unimb.si/si/jet.html.
Thejournalispublishedfourtimesayear.Articlesareavailableatthejournalshomepage
www.fe.unimb.si/si/jet.html.
Lektoriranje/LANGUAGEEDITINGTerry
T.
JACKSON
Produkcija/PRODUCTIONVizualnekomunikacijecomTECd.o.o.
Oblikovanjerevijeinznakarevije/JOURNALANDLOGODESIGNAndrejPREDIN
RevijaJETjesofinanciranasstraniJavneagencijezaknjigoRepublikeSlovenije.
TheJournalofEnergyTechnologyiscofinancedbytheSlovenianBookAgency.
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AlternativnetehnologijehidroenergetikeVasuzavedanjaokoljskihproblemovgledeemisijvokolje,predvsemogljikovegadioksidain
drugih toplogrednih plinov, je vse bolj oitno, da predvsem korienje obnovljivihenergetskihvirovvodikzmanjanjutegaproblema.Korienjehidroenergetskegapotencialarekje enaod bolj sprejemljivihmonosti korienjaobnovljivih virov.V zadnjem asu sezavedamo,daimaposeganjevreke,kothidroenergetskevire,veliknegativenvplivnasam
renihabitat kakor tudinaokolje rek.Poznani soprimeri, kjer zaradinepravilnepriprave
renega korita anaerobno v vodi razpada biolokimaterial, katerega produkti sometan,ogljikov dioksid,oziroma veina toplogrednih plinov. Prav tako klasine zajezitve rek zelo
vplivajonaokolje,predvsem v smisludvigapodtalne vode, karjenanekaterih podrojih
sicer zaeleno, veinomapa ne.Da biohraniliokolje,je potreben drugaen, alternativni,pristopizkorianjahidroenergije, kipravilomaomogoanijienergetskiizplenvprimerjavisklasinim nainom korienja, vendar pa mnogo manj vpliva na okolje. Pri tem nainupraviloma koristimo samo dinamini del, torej tokovni ali kinetini del, energetskega
potenciala.Zataknoizkorianjerenegatokanepotrebujemovejihzajezitevreke,simerjetudivplivnaokoljebistvenomanji.Pritakojeposeganjevrenokoritoinbreinemanje,sajpotrebujemolesidranjevrenitokpostavljenihturbin.
RekaMuraje edina veja slovenska reka, kije v vseh teh letihostala v naravniobliki in
energetskoneizkoriena.Neposrednookoljerekejeobutljivo,sajjerekaprodonosna,karpomeni,dasednoinbreinerekespreminjajo.alsososedjeAvstrijci,rekovekratzajeziliinstemprekinilinaravnidotokprodaizAlpskegapodroja,kjerrekaizvira.Dnorekesev
slovenskem delu poglablja, ustvarjajo semrtvi kanali, imenovanimrtvice, v katerih so se
oblikovali edinstveni naravni biotopi. al poglabljanje reke vpliva tudi na upad gladinepodtalnevode,kijevnekaterihdelihPrekmurjaezaskrbljujo.
S podelitvijo dravne koncesijeDravskim elektrarnamMaribor, zaenergetsko izkorianjerekeMure, se odpira monost izgradnje verige hidroenergetskih central na rekiMuri. Vkoncesijije predvidenih 8 elektrarn odmejnega dela rekeMure zAvstrijo do Vereja.Vkoncesiji ocenjeni energetski potencial znaa 84 MW, letna proizvodnja pa 445,8 GWh.
Dolina reke v slovenskem delu je okrog 98 km. Povprena vodnatost reke Mure, oz.povprenipretokiznaajood170do240m
3/s.GledenacelotnoporaboelektrikevSloveniji,
kiznaapriblino12,9TWhzrastjookoli3%letno,bienergetskokorienjepotencialarekeMurepokrivalookrog3,5%slovenskeporabe.TrenutnovSlovenijishidroviripokrivamo3,7
TWh,karznaapriblino28,7%celotneporabe.
Civilnainiciativa,kisejeoblikovalazaradiohranitveokoljainrekeMure,nasprotujegradnji
klasinihzajeznihhidroelektrarn.Ocenjujejo,dabibila izgradnjajezov inpotrebnihzgradb
pregrobposegvokolje,kibitrajnovplivalnabiotoprekeMureinnjenoneposrednookolico.
MordajepravalternativnipristoppriizkorianjuhidropotencialovrekeMureprilonostza
ohranjanje
ob
utljivega
okolja
in
samooskrbo
regije
z
elektri
no
energijo.
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Alternativehydroenergytechnologies
Due to the awareness of environmental problems in the previous decade, mainly the
emissionsof carbondioxideandothergreenhousegases, it isbecomingevident that the
increasinguseofrenewableenergysourcesleadstoareductionofthisproblem.Theuseof
the hydroenergy potential of rivers is one of the acceptable possibilities for renewable
sources.However,recently ithasbeenconfirmedthataggressive interventiononriversfor
hydroenergyresourceshasahighlynegative impactontheriverhabitataswellasonthe
wider environment of rivers. Cases of incorrect preparation of flood areas are known in
whichanaerobicdecompositionofbiologicalmaterialproducedmethane,carbondioxide,
i.e.,most
greenhouse
gases.
The
traditional
river
dams
for
hydro
plants
influence
the
environmentseverely,especiallyintermsofrisinggroundwater,whichisdesirableinsome
areas but mostly not. In order to preserve the environment, a different, alternative,
approachisrequiredtoexploitthehydropower,whichgenerallyleadstolowerenergygain
comparedtoconventionalmethod,butwithlessenvironmentalimpact.Inthismanner,only
the dynamic part of the river, i.e., the flow or kinetic part, is used for energy. For such
exploitationofriverflow,wedonotneedalargecaptureoftheriver;consequently,there
is less influenceon the riverenvironment. Itdoesnotdemandmajor interventionon the
banksandriverbed;itrequiresonlytheanchoringofflowturbines.
TheMuraRiver is theonly Slovene river that remains in itsnatural formwith itsenergy
potential unused. The immediate environment of the river is sensitive, since the river
transports earthmaterial and consequently thebed andbanksof the river changesover
time.Unfortunately,inAustria,wheretheriverbegins,ithasbeendykedtheseveraltimes,
blockinganddisruptingthenaturalflowofgroundmaterialfromthespringalpinearea.Asa
result,thebottomoftheriver inSlovenia isdeepeningandcreatingdeadchannels,called
oxbowlakes,whereuniquenaturalhabitatshavedeveloped.Unfortunately,thedeepening
oftheriveralsolowersgroundwaterlevels,whichisinpartsofthePrekmurjeareaisalready
alarming.
WiththegrantingofgovernmentconcessionstoDravskeelektrarneMaribor(DravaHydro
electricalPower
Plants
Company)
for
energy
exploitation
of
the
Mura,
the
possibility
opens
for the building of a chain of hydro power stations. In the concessions are eight power
plants,fromtheAustrianbordertoVerej.Theenergypotentialisestimatedto84MW,with
annualproductionof445.8GWh.ThelengthoftheSlovenianpartoftheriverisaround98
km.TheaveragewatercapacityoftheMuraRiveroraverageflowrangesfrom170to240
m3/s.With theoverallconsumptionofelectricity in theSlovenia,approximately12.9TWh
withgrowthof3%annually, thepotentialenergyof the riverMuracoversabout3.5%of
Sloveneelectricpowerconsumption.Withitshydroresources,Sloveniacurrentlycovers3.7
TWh,representingapproximately28.7%oftotalconsumption.
CivilInitiative,locallyformedtopreservetheenvironmentandtheMura,isopposedtothe
constructionof
classic
hydroelectric
plants.
It
is
estimated
that
the
construction
of
dams
will
bedevastatingforthebiotopeanditsimmediatesurroundings.
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PerhapsanalternativeapproachtotheMuraRiverenergyexploitationisanopportunityfor
preservingasensitiveenvironmentaccompaniedwithregionalenergyselfsupply.
Krko,July
2010
Andrej
PREDIN
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Table of Contents /
Kazalo
Fuzzyapproachtooptimiseenergycapacitiesforpermanentandreliableelectricitysupply/
Mehkipristopprioptimiranjuenergijskezmogljivostizatrajno inzanesljivooskrbozelektrino
energijoJanezUsenik................................................................................................................................13
IsolatedbidirectionalDCDCconverter/
IzoliranidvosmerniDCDCpretvornik
FrancMihali,AlenkaHren.........................................................................................................27
CleancoaltechnologiesatVelenjecoalmine/
istepremogovnetehnologijenaPremogovnikuVelenjeSimonZavek,LudvikGolob,Janjaula.....................................................................................41
Energypolicy
for
production
resources/
Energetskapolitikazaproizvodnevire
DragoPapler,tefanBojnec........................................................................................................53
Experimentalanalysisofthermodynamicalsurgeatwaterpumpinlet/
Eksperimentalnaanalizatermodinaminihfluktuacijtokanavstopuvvodnorpalko
IgnacijoBilu,AndrejPredin......................................................................................................67
Instructionsforauthors..............................................................................................................75
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JETVolume3 (2010),p.p.1326
Issue3,August2010
http://www.fe.unimb.si/si/jet.html
FUZZY APPROACH TO OPTIMISE ENERGY
CAPACITIES FOR PERMANENT AND
RELIABLE ELECTRICITY SUPPLY
MEHKI PRISTOP PRI OPTIMIRANJU
ENERGIJSKE ZMOGLJIVOSTI ZA TRAJNO
IN ZANESLJIVO OSKRBO Z ELEKTRINOENERGIJO
JanezUsenik
Keywords:capacity,optimalprice,energy,deterministicdynamicmodel,fuzzylogic,fuzzymodel,estimation
Abstract
Planningoptimalcapacitiesandtechnologiesforsustainableandreliableelectricitysupplywith
specialattentiontoriskmanagementisbecomingincreasinglyimportant.FabijanandPredin[1]
dealtwiththismatterbyestimatingthepowersupplymarketinthenearfutureand,basedon
this estimation, they built a deterministic quasidynamic model for forming the price of
electricitysupply.
Theequation theyhavedeveloped iscorrectandapplicable.However, itsweakness is in the
usageofestimatedvaluesasexplicitprecisedata.
In thispaper,wewillpresentamorecurrentoptionofdesigningsuchamodel, inwhich the
fuzzylogicapproachisapplied.Theapplicationoffuzzylogicinthiscaseisentirelyreasonable,
sinceallthevaluesused inthemodelareonlyestimates,i.e.moreorlessreliablepredictions.
Therearemanyoptionsforbuildingafuzzymodel,butinthispaperonlythemostcompatible
with a given deterministic quasidynamic model will be shown. The direct comparison of
numerical results ispossible,which laterenablesbuildingaknowledgebase for theeffective
Corresponding author: Prof. Janez Usenik, PhD., University of Maribor, Faculty of Energy
Technology,Tel.:+38631751203,Fax:+38676202222,Mailingaddress:Hoevarjev trg1,
8270Krko,Slovenia,emailaddress:[email protected]
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applicationofaneuralnetwork in theprocessofalgorithm (built in the fuzzysystem/model)
learning.
Povzetek
Nartovanje optimalnih kapacitet in tehnologij za trajno in zanesljivo oskrbo z elektrino
energijo,pri emerjeposebnopozornostdanaobvladovanju tveganj,je v sedanjih asih vse
pomembneje,AvtorjaFabijan,Predin,1setemupomembnemuvpraanjuposvetitasstalia
ocenjevanja energetskega trga v kratkoroni bodonosti in na tej podlagi izgradita
deterministini kvazidinamini model oblikovanja cene elektrine energije. Formula, ki jo
izpeljeta,je korektna in uporabna, njenaibkostje v tem, da z zgolj ocenjenimi vrednostmi
operirakotzeksplicitniminatannimipodatki.
V tem lankuje predstavljena bolj aktualnamonost, da pri oblikovanju taknegamodela k
problemu pristopimo z uporabo mehke logike. Uporaba mehke logike je v tem primeruvsekakorsmiselna,sajsovsevrednosti,skaterimivmodeluoperiramo,zgoljocene,torejboljali
manj zanesljive napovedi. Razlinih monosti izgradnjemehkegamodelaje ve, v lankuje
predstavljena tista, ki v strukturi algoritma najbolj sledi danemu deterministinemu
kvazidinaminemumodelu.Razlogzatojedvojni:monajeneposrednaprimerjavanumerinih
rezultatov, kasneje pa je s tem omogoena izgradnja baze znanja za uinkovito uporabo
nevronskemreevpostopekuenjaalgoritma,vgrajenegavmehkisistem/model.
1 INTRODUCTION
Following the paper Fabijan, Predin, 1, an optimal energy source structure for electricity
productionistreatedbytheneedsforsatisfyingofsomeparameters,like
- longtermreliableelectricityenergysupply,
- systemsuitability,
- suitabilityofproductioncapability,
- suitabilityofelectricitygrid,
- marketsuitability,
- shorttermandreliablesupply.
From the pointof viewof the transmission system operator (TSO), theoptimal structureof
energy producing resources is treated by frequency control on the primary, secondary andtertiary(minute)controllevels.
Energy companies areexposed tobusiness risk,production riskand financial risk ingeneral.
Every kind of risk depends on many elements in the working of the energy system. The
obligation of the decisionmakers is determining how to control this system, but themain
challengeisthattheefficiencyofthesystemhastobeashighaspossibleunderallconstraints
inoperating.
All these risksgenerate costs,dependingondifferent technologiesand sourcesofproducing
andsellingelectricenergy.Ifweknowthesecosts,wecancalculatethepriceofelectricenergy
inadvance.
Risk is becoming an increasingly serious issue in all areas of society. The concept of risk
generallyimpliesanobjectivequantitativeestimateoftheprobabilityofaneventmeasuredby
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Fuzzyapproachtooptimiseenergycapacitiesforpermanentandreliableelectritysupply
itsfrequency.Inindustrialsystems,unreliabilityisusuallyidentifiedwiththeobjectiveelement
inrisk,Harris,[2].
2 DEFINING THE PROBLEM
Inthisarticle,weshallusethefollowingnotations:
i jc k priceofoneunitofelectricalenergyofsourceiattimepoint jk ,
i ju k quantityofproductionelectricalenergyinsourceiattimepoint jk ,
jw k weightofrigidityofthesourcesstructuresintimepoint jk ,
jp k interestratein%attimepoint jk ,
ji k rateofthecompoundinterest,where
100
j
j
p ki k (1.01)
jd k discountrate,where
1j
jj
i k
d k i k
(1.02)
jk basistermforcalculatingdiscountpresentvalue,where
11
1j j
j
k d ki k
(1.03)
, , 1,2,3, ,jk j J J n timedistanceinseparateyears(endofthetimeinterval/year),
i=1,2,3,.,msetofsources
Withrespect to theminimaof totalcosts,weobtainthe formulafor thecalculatedexpected
referencepriceofelectricenergy1
1 InFabijan,Predin, 1, the formula forcalculating theexpectedreferencepriceofelectricenergyexists inasimilar
form
,
,
,
1t
t vI t vt
t t v
t vt
uwc d c
w u
.Themininginaccordancewith(1.04)isthesame.
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1
11
1j
mk j i j
j i j j m j J i
i jjij
w k u k c d k c k
u kw k
(1.04)
In(1.04)expressions
1 2
1
, 1,2,3, ,j j
j n
nj
j
w k w k w k j n
w k w k w k w k
(1.05)
and
1 2
1
, 1,2,3, ,i j i j
i j m
j j m j i j
i
u k u k u k j n
u k u k u k u k
(1.06)
arenormalizedweightsofevery jw k and i ju k for , 1,2,3, ,jk j n and 1,2, ,i m ,i.e.
1jj J
w k ,
1
1m
i ji
u k .
Considering(1.03),(1.05)and(1.06),formula(1.04)hasthesimplestbutapplicableform
1
j
mk
j j i j i j
j J i
c w k k u k c k
(1.07)
Formula
(1.07)
represents
the
deterministic
quasidynamic
model,
depending
on
data
not
knowninexplicit,butonlyinestimatedform.
This estimation contains expert knowledge, so the experts have to take an active part in the
everypartofdecisionprocess.
Fromthispointofview,wecanwritetheformula(1.07)intheform:
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Fuzzyapproachtooptimiseenergycapacitiesforpermanentandreliableelectritysupply
1
2
1
1 1 1 1 1 1 2 1 2 1 1 1
2 2 1 2 1 2 2 2 2 2 2 2
1 1 2 2
j
n
mk
j j i j i j
j J i
k
m m
k
m m
k
n n n n n n m n m n
c w k k u k c k
w k k u k c k u k c k u k c k
w k k u k c k u k c k u k c k
w k k u k c k u k c k u k c k
1 21 1 1 2 2 2
nk k k
n n nc k k c k k c k k
AgraphicrepresentationisinFigure1.
Figure1:Dynamicprocessinformula(1.07)3 FUZZY MODEL
Everypredictionofeventsandespeciallytheirfuturevaluesisnotprecise;itdependsonmany
circumstances,moreorlessknowninadvance.Thequasidynamicdeterministicmodelgivenby
formula(1.07)
is
dependent
on
the
precision
of
data.
All
numerical
values
in
the
future
are
not
precise;theyareonlyestimated.Ofcourse,wedonotknowthepriceofelectricalpowerten
yearsinthefuture.Inthistimeofglobalrecession,wedonotknowwithcertaintythepriceof
electrical power for one year in future, to say nothing of five or more years. However,
vagueness in prediction is appropriate for using fuzzy logic, Ross, [3]. We can a build fuzzy
system to calculate (better: to predict) the price of energy power with regard to request for
optimizingenergycapacitieswithapermanentandreliableelectricitysupply.
Analysis of our problem has assumed that the consequences of decisions are known with
certainty and are reversible. However, these assumptions are not factually correct for many
problems.Resourceusedecisionsconcernthefutureaswellaspresent,andthefuturecannot
beknownwithcertainty,Permanandall,[4].
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Resourcestocksaresubjecttomanystochasticeffects.Themethodsofdecisiontheorycouldbe
used to compute optimal management strategies in the presence of uncertainty. Dynamic
decisiontheory,which isobviouslyrequiredforresourcedecisions, ismathematicallydifficult.
Numerical
computation
of
optimal
policies
encounters
the
curse
of
dimensionality,
Levin
et
al.,
[5].
Inprinciple,everysystemcan bemodeled,analyzedandsolvedbymeansof fuzzy logic.
Due to the complexity of the given problem and the subjective decisions of customers,
which are better described with fuzzy reasoning, it is advisable to introduce a fuzzy
approach. Some basic solutions of the control problems using fuzzy reasoning were
presented inthe paperUsenik,Bogataj,[6].For someproblemsaboutthe controlofthe power supply system, we propose fuzzy reasoning. It is obvious that decision makers,
whensolvingeverydayproblems incontrolofsystems,operatewithfuzzy logic,Terano,
[7].
Ourproposed
fuzzy
model
will
be
based
on
these
assumptions,
whereby
the
usual
five
stepshavetobetaken:fuzzificationofthe inputand outputvariables,applicationofthe
fuzzy operator in the antecedent, implication from the antecedent to the consequent,
aggregationofthe consequentsacrossthe rules,and defuzzification.
3.1 Fuzzy System Structure
Thefuzzysystemstructure identifiesthefuzzy logic inferenceflowfromthe inputvariablesto
theoutputvariables.Thefuzzificationintheinputinterfacestranslatesanaloginputsintofuzzy
values.Thefuzzy inferencetakesplace inruleblockswhichcontainthe linguisticcontrolrules.
Theoutputs
of
these
rule
blocks
are
also
linguistic
variables.
The
defuzzification
in
the
output
interfacestranslatesthemintoanalogvariables,Usenik,J.[8],FuzzyTech,[9].
Thefollowingfigureshowsthewholestructureofthisfuzzysystem including input interfaces,
ruleblocksandoutputinterfaces.Theconnectinglinessymbolizethedataflow.
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Fuzzyapproachtooptimiseenergycapacitiesforpermanentandreliableelectritysupply
Figure2:StructureoftheFuzzyLogicSystem
3.2 Fuzzification
In the fuzzificationphase,wehave todefine fuzzysets for all fuzzyvariables (inputand
output) and define their membership functions. Linguistic variables are used to translate
realvaluesintolinguisticvalues.Thepossiblevaluesofalinguisticvariablearenotnumbersbut
socalledlinguisticterms.
For everyfuzzyset and for everyfuzzyvariable,wehavetocreatemembershipfunctions.
Linguistic variables have to be defined for all input, output and intermediate variables. The
membershipfunctionsaredefinedusingonlyafewdefinitionpoints.
For the inputfuzzyvariableN_PART1,theycouldbeasshowninFigure3.Onthe xaxis,we
measurethe variablenuclearpart_1giveninpercenteages(relativenumbers)from0to
50%,dependingonour data.On the yaxis,wemeasuremembership for everypossible
nuclearpart_1and for everyfuzzysetLOW,MEDIUMand HIGH.
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Figure3:InputfuzzyvariableN_PART1andtheirmembershipfunctions
The outputof the fuzzy variable PRICE couldbeas shown inFigure4.On the xaxis,we
measure the variablepricegiven inmoneyunits; in thisexample,euros from0 to60
EUR,dependingonourdata.On theyaxis,wemeasuremembership for everypossible
priceand foreveryfuzzyset LOW,MEDIUMandHIGH.
Figure4:OutputFuzzyvariablePRICEandtheirmembershipfunctions
The output of the fuzzy process can be the logical union of two or more fuzzy
membershipfunctionsdefinedinthe universeofdiscourseofthe outputvariable.
3.3 Rule Blocks
Theruleblockscontainthecontrolstrategyofafuzzylogicsystem.Eachruleblockconfinesall
rulesforthesamecontext.Acontext isdefinedbythesameinputandoutputvariablesofthe
rules.
The Ifpartof the rulesdescribes the situation forwhich the rulesaredesigned,while the
thenpartdescribestheresponseofthefuzzysysteminthissituation.Thedegreeofsupport
(DoS)isusedtoweigheachruleaccordingtoitsimportance.
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Theprocessingof therulesstartswithcalculating theifpart.Theoperator typeof therule
block determines which method is used. The generalization of the Boolean and is the
minimumoperatorandageneralizationoftheBooleanoristhemaximumoperator.
The computationof fuzzy rules is called fuzzy inference and consists of three steps: the
application of the fuzzy operator (and/or) in the antecedent, the implication from the
antecedent to the consequent and the aggregation of the consequentsacross the rules.
The first step determines the degree to which the complete if part of the rule is
satisfied.Inthisstep,weusuallyuse the operatorORfor the minimumand theoperator
AND for the maximum.The secondstepmakesuse ofthe supportofthe preconditionto
calculate the support of the consequence. Finally, the aggregation step determines the
maximumdegreeofsupportfor eachconsequence.
In our work, we applied FuzzyTech software. In accordance of this software tool, the
ruleswere
automatically
created.
Forexampleintheruleblock03,wehavesixrules:
1. if PRICE_T3isLOWandTIME3isLOW,thenPRICE3isLOW
2. if PRICE_T3isLOWandTIME3isHIGH,thenPRICE3isMEDIUM
3. if PRICE_T3isMEDIUMandTIME3isLOW,thenPRICE3isLOW
4. if PRICE_T3isMEDIUMandTIME3isHIGH,thenPRICE3isHIGH
5. if PRICE_T3isHIGHandTIME3isLOW,thenPRICE3isMEDIUM
6. if PRICE_T3isHIGHandTIME3isHIGH,thenPRICE3isHIGH
3.4 Defuzzification
Defuzzification is the conversion of a given fuzzy quantity toaprecise crisp quantity. In
literature, at least seven methods, Usenik [10], are common for defuzzifying: max
membership principle, centroid method, weighted average method, meanmax
membership,centreofsums,centreofthe largestarea,first(last)ofmaxima.
Differentmethodscanbeusedforthedefuzzification,resultingeither intothemostplausible
result or the best compromise. The best compromise is produced by the methods CoM
(Center of Maximum), CoA (Center of Area) and CoA BSUM, a version especially for efficient
VLSIimplementations.
The
most
plausible
result
is
produced
by
the
methods
MoM
(Mean
of
Maximum)andMoMBSUM,aversionespeciallyforefficientVLSI implementations,Ruspiniet
all.,[11],FuzzyTech,UsersManual,[9].
The resultfromthe evaluationoffuzzyrules isfuzzy.Defuzzification isthe conversionof
a given fuzzy quantity to a precise crisp quantity. The most frequently method used in
praxis is CoM defuzzification (the CenterofMaximum). As more than one output term
can be accepted as valid, the defuzzification method should be a compromise between
differentresults.The CoM methoddoesthisbycomputingthe crispoutputasaweighted
average of the term membership maxima, weighted by the inference results. CoM is a
kind
of
compromise
between
the
aggregated
results
of
different
terms
j
of
a
linguistic
outputvariableand isbasedonthemaximumYjofeachtermj.
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4 NUMERICAL EXAMPLE
4.1 Numerical example using deterministic approach
Asan
example
in
Fabijan,
Predin,
[1],
an
estimate
for
reference
price
in
Slovenia
is
done
with
regardtothenexttenyears.Thecontrollercalculateswiththreetimepoints:thefirst isnext
year,thesecondisforthenextthreeyearsandthethirdisfornexttenyears,i.e. 1,3,10j j
k
are 1 3,k k and 10k .
Bankinterestcouldbetakenasfixedforallthreetimepoints:
1 3 10 4%p k p k p k ,
1 3 10 0,04i k i k i k ,
1 3 100,04
0,038461,04
d k d k d k and
1 3 10 0 96154k k k , .
Fourtypesofelectricpowerplantsareconsidered:nuclearpowerplants,coalpowerplants,gas
powerplantsandhydropowerplants.ForEurope,wecanpredict:a)fornuclearpowerplants
theprice
of
35/MWh
in
the
first
time
point,
the
price
of
40/MWh
in
second
time
point
and
thepriceof50/MWhinthethirdtimepoint,b)forthermopowerplantsthepriceof45/MWh
inthefirsttimepoint,thepriceof50/MWhinsecondtimepointandthepriceof70/MWhin
thethirdtimepoint,c)forgaspowerplantsthepriceof60/MWh inthefirsttimepoint,the
priceof65/MWhinsecondtimepointandthepriceof85/MWhinthethirdtimepointandd)
forhydropowerplantsthepriceof35/MWh inthefirsttimepoint,thepriceof40/MWhin
second time point and the price of 60/MWh in the third time point. In our notations this
meansfollowingdata(ineuros):
a) fornuclearpowerplants i=1: 1 1 35c k , 1 3 40c k and 1 10 50c k ,
b) forthermopowerplantsi=2:
2 145c k ,
2 350c k and
2 1070c k ,
c) forgaspowerplants i=3: 3 1 60c k , 3 3 65c k and 3 10 85c k ,
d) forhydropowerplants i=4: 4 1 35c k , 4 3 40c k and 4 10 60c k .
FromtheOEDCdata,weassumethat inthefirsttimepointtheratiobetweennuclearpower
plantsversusthermalpowerplantsversusgaspowerplantsversushydropowerplantswillbe
23% : 39% : 25% : 13%. Following expression (1.05), this means 1 1 0,23u k , 2 1 0,39u k ,
3 1 0,25u k and 4 1 0,13u k .Inthesecondtimepoint,theratiobetweennuclearpowerplants
versusthermalpowerplantsversusgaspowerplantsversushydropowerplantswillbe20% :
38% : 30% : 12%. Following expression (1.05), this means 1 3 0,20u k , 2 3 0,38u k ,
3 3 0,30u k and 4 3 0,12u k .Inthethirdtimepoint,theratiobetweennuclearpowerplants
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versusthermalpowerplantsversusgaspowerplantsversushydropowerplantswillbe15%:
36% : 38% : 11%. Following expression (1.05), this means 1 10 0,15u k , 2 10 0,36u k ,
3 10 0,38u k and 4 10 0,11u k .
Of course, 1 1 2 1 3 1 4 1 1u k u k u k u k , 1 3 2 3 3 3 4 3 1u k u k u k u k and
1 10 2 10 3 10 4 10 1u k u k u k u k .
Thesourcestructureischangedslowlyandthereforeincreasestheinfluenceoffirstyearand
decreasesalllatertimesintheratio50%:30%:20%infirst,secondandthirdtimepoint,
respectively.Following(1.04),wehave 1 0,5w k , 3 0,3w k and 10 0,2w k ;
1 3 10 1w k w k w k .
YEAR INTER.RATE PRICENUCL PRICECOAL PRICEGAS PRICEHYDRO WEIGHTNUCL WEIGHTCOAL WEIGHTGAS WEIGHTHYDRO WEIGHTOFTIME
1 4 35 45 60 35 0.23 0.39 0.25 0.13 0.5
3 4 40 50 65 40 0.20 0.38 0.3 0.12 0.3
10 4 50 70 85 60 0.15 0.36 0.38 0.11 0.2
1.0Table1:Datafornumericalexample
Fromformula(1.07)weobtain:
1
3
10
1
1 1 1 1 1 1 2 1 2 1 3 1 3 1 4 1 4 1
3 3 1 3 1 3 2 3 2 3 3 3 3 3 4 3 4 3
10 10 1 10 1 10 2 10
j
mk
j j i j i j
j J i
k
k
k
c w k k u k c k
w k k u k c k u k c k u k c k u k c k
w k k u k c k u k c k u k c k u k c k
w k k u k c k u k c 2 10 3 10 3 10 4 10 4 10k u k c k u k c k
Thenumericalresultis:
1
3
10
0,5 1,04 0,23 35 0,39 45 0,25 60 0,13 35
0,3 1,04 0,20 40 0,38 50 0,30 65 0,12 40
0,2 1,04 0,15 50 0,36 70 0,38 85 0,11 60 45,06
c
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On the basis of all predictions data and formula (1.07) for the deterministic quasidynamic
model,weobtainedtheestimatedreferencepriceofelectricenergyinthismomentinthevalue
of45.06/MWh.
4.2 Numerical example using fuzzy approach
Usingthefuzzyapproachforthisdeterministicquasidynamicmodel,withequaldatawegeta
final price of c=45.00 EUR. This result is very good and is based on the suitable form of
membershipfunctionsinthefuzzyvariablesandonsuitableruleblocks(ifthenrules).
Theerrorissmall:just0.13%fordatafromTable1.
InTable2,wecanseetheresultininteractivedebugmodeofsoftwareFuzzyTech,ver.3.55.
Table2:Resultofinteractivedebugmode
5 CONCLUSION
Thefuzzyapproach isverysuccessfulwithrealproblems,especially incasesofambiguityand
imprecise data. Predicting the prices of electrical energy for some years in advance is not
explicit;thisaveryappropriatesubjectforfuzzylogicthinking.Allpredictionsforthefutureare
just estimates, more or less good, depending on thequantity of the relevant data, but very
sensitive for every change of variable conditions in the prediction system. The electricity
market, both in Europe and in Slovenia, depends on many variables; good and precise
prediction
of
them
is
nearly
impossible.
A
fuzzy
system
is,
at
its
core,
founded
on
vagueness,
inaccuracy, approximation and with this suitable for description events in the future by the
methodofcommonsense.
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Requiringprecision inengineeringmodelsandproducts translates to requiringhighcostand
long leadtimes inproductionanddevelopment.Forothersystems,expense isproportionalto
precision:moreprecisionentailshighercost.Whenconsideringtheuseoffuzzylogicforagiven
problem,
an
engineer
or
scientist
should
ponder
the
need
for
exploiting
the
tolerance
for
imprecision,Ross,[3].
Intheprocessofbuildingthefuzzysystem,wehadtoincludesomequalifiedexpertsandmake
an expert model. The expert system has separate domainspecific knowledge and problem
solving methodology and includes the concepts of the knowledge base and the inference
engine.Theexpertsystemshouldthinkthewaythehumanexpertdoes,Zimmermann,[12].
However, itcanbe said that fuzzyapproach ishighlyefficient for theoptimizationofenergy
capacitieswithcriterialfunctionofpermanentandreliableelectricitysupply. InSection2,the
developedfuzzymodelforestimatingthepriceofelectricalenergyforthecomingyearsworks
quitewellintheambiguousconditionsoftheenergymarket.Buildingafuzzymodelisjustone
stepin
the
creation
of
the
relevant
system;
the
robustness
and
the
quality
of
algorithm
depend
onmanyexamples.Forthisreason,theusageofneurallearningisrequired;thisisthenextstep
infutureresearchformakingtherelevantexpertsystem.
References
[1] Fabijan, D., Predin, A.: Optimal energy capacities and technologies for permanent andreliable electricity supply, considering risk control, JET Journal of Energy Technology,
Volume2(2009),p.p.6984.
[2]Harris,
J.:
Fuzzy
Logic
Applications
in
Engineering
Science,
Published
by
Springer,
P.O.
Box
17,
3300AADordrecht,TheNetherlands,2006.
[3] Ross, J.T.: Fuzzy Logicwith EngineeringApplications, 2nd ed., JohnWiley Sons Ltd, TheAtrium,SouthernGate,Chichester,WestSussexPO198SQ,England,2004,reprinted2005,
2007.
[4] Perman, R., Ma Y., McGilvray, J., Common M.: Natural Resource and EnvironmentalEconomics,PearsonEducationLimited,EdinburghGate,Harlow,EssexCM202JE,England,
1999.
[5]Levin,S.A.,Hallam,T.G.,Gross,L.,J.:AppliedMathematicalEcology,SpringerVerlagBerlinHeidelberg
New
York,
1989.
[6]Usenik, J.,Bogataj,M.:Afuzzysetapproachfora locationinventorymodel.Transp.plan.technol.,2005,vol.28,no.6,pp.447464.
[7]Terano,T.,Asai,K.,Sugeno,M.:FuzzySystemsTheoryanditsAplicactions,AcademicPress,Inc.,SanDiego,London,1992.
[8]Usenik, J.:FuzzyApproach inprocessofmultipleattributedecisionmaking, JET JournalofEnergyTechnology,Volume1(2009),p.p.4358.
[9]FuzzyTech,Usersmanual,2000,INFORMGmbH,InformSoftwareCorporation.[10]Usenik,J.:Mathematicalmodelofthepowersupplysystemcontrol,JETJournalofEnergy
Technology,Volume2(2009),p.p.1734.
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[11] Ruspini, E. H., Bonissone, P. P., Pedrycz, W. (Editors in Chief): Handbook of FuzzyComputation,InstituteofPhysicsPublishing,BristolandPhiladelphia,1998.
[12] Zimmermann, H. J.: Fuzzy set theory and its applications, 4th ed., Kluwer AcademicalPublishers,
Norwell,
Massachusetts,
2001.
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JETVolume3(2010),p.p.2740
Issue3,August2010
http://www.fe.unimb.si/si/jet.html
ISOLATED BI-DIRECTIONAL DC-DC
CONVERTER
IZOLIRANI DVOSMERNI DC-DC
PRETVORNIK
FrancMihaliandAlenkaHren
1
Keywords:Switchedmodepowersupply,BidirectionalDCDCconvertercircuit,PulseWidth
Modulation(PWM)
Abstract
This paper presents principles of operation and safe startup procedures for an isolated bi
directionalDCDCconverterinbuckandboostmodes.Thisconverterhasbeendevelopedasa
partofamultifunctional4kWpowersupplysystemthatusesahighDClinkvoltage(450V).The
isolated bidirectional DCDC converter can charge 28 V batteries and supply auxiliary low
voltageDC loads.Additionally,the isolatedbidirectionalconvertercanalsodrawpower from
the batteries or from a trucks driven alternator to maintain the high voltage DClink.
Modulationstrategiesandstartupproceduresof thisconverterhavebeenvalidatedbyusing
the Matlab SymPowerSystems Toolboxes and, finally, they have been also experimentally
verified.
Correspondingauthor:Assoc.Prof.FrancMihali,Tel.:+38622207331,Fax:+38622207315,
Mailingaddress:UniversityofMaribor,FacultyofElectricalEngineeringandComputerScience,
Smetanova17,2000Maribor,SLOVENIA,Emailaddress:[email protected] Mailing address: University of Maribor, Faculty of Electrical Engineering and Computer
Science,Smetanova17,2000Maribor,SLOVENIA,Emailaddress:[email protected]
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Povzetek
VprispevkustapredstavljenaprincipdelovanjainvarenzagonizoliranegadvosmernegaDCDC
pretvornikavdelovnemreimunavzdol innavzgor.Tapretvornikjebilrazvitkotsestavnidel
vefunkcionalneganapajalnegasistemamoido4kWzvisokonapetostnoenosmernozbiralko
(450 V). Izolirani dvosmerni pretvornik lahko polni 28V baterije in napaja zunanje nizko
napetostneenosmerneporabnike.eve,tapretvornik lahkorpaenergijo izzunanjihbaterijali iz alternatorja tovornega vozila in tako napaja visoko napetostno enosmerno zbiralko.
Modulacijski principi in zagonske procedure pretvornika so bili najprej razviti in preverjeni s
pomojoraunalnikegaprogramaMatlabSymPowerSystemsinnatoeksperimentalnopotrjeni.
1 INTRODUCTION
Isolatedbi
directional
DC
DC
converters
are
commonly
used
in
electronic
equipment
such
as
uninterruptible power supplies (UPS), electric vehicles and as frontend converters for
distributedpowersystemapplications,amongothers. Inallapplications, thekey featuresare
thesafetyofthesystemoperationandoperationatthehighestpossibleefficiency.Nowmore
thanever,wehavetofacetheproblemsofenergysupply,sincetheconsumptionofoilfuelsis
continuallyrisingandtheirpricesareunstable.Therefore,thismustbethechallengeforallRD
centresthroughouttheworld:todevelopmodernandnewpowersupplysystemsoperatingat
thehighestpossibleefficiencies[1],[2].
Ablockdiagramofthemultifunctionalpowersupplysystem(wherethedieselenginesupplying
theDClinkcanbereplacedwithanyalternativeenergysources,e.g.,solar,wind,fuelcellsetc.)
isshowninFigure1.
Figure1:Blockdiagramofthemultifunctionalpowersupplysystem.
An isolatedbidirectionalDCDCconverter isthecombinedconfigurationofabatterycharging
circuitandDCDC convertercircuit. Itallowspower flow inbothdirections, i.e., towards the
batteryandfromthebattery,andhasawiderangeofapplicationsfromuninterruptedpower
supplies,batterycharginganddischarging systems,aerospaceapplications toauxiliarypower
supplies for hybrid electrical vehicles. Possible implementations of bidirectional converters
with fullbridge topologyusing resonance [4], soft switchingorhard switching [5]havebeen
reported in literature. Each implementation has disadvantages, including higher component
ratings,increasedcircuitcomplexity,lossofswitchingsignalsatlightloadsforsoftswitchcircuitetc. In thispaper, thebidirectional fullbridgeDCDCconverter topology (shown inFigure2),
usinghardswitchPWMwithemphasisonsafe startupprocedures inboostandbuckmode
operation,willbediscussed.
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IsolatedbidirectionalDCDCconverter
2 ISOLATED BI-DIRECTIONAL CONVERTER DESCRIPTION
BidirectionalDCDC converters are used to interconnect differentDC voltage buses and to
transfer
energy
between
them.
In
most
applications,
in
addition
to
the
wide
input
and
output
voltagerangeoperation,ahighvoltagetransferratioisalsorequired(e.g.,switchingfrequency
fS=25kHz,DClinkvoltageUDC=450V,batteryvoltageUBat=28Vandnominaloutputpower
Po=4kW). Insuchacase,adirectbidirectionalconverter isnotanappropriateoption,since
theconverterwouldbeoperatedwithasmalldutyratioinbuckmodeoperationoralargeduty
ratioinboostmodeoperation.Theserequirementscausehighcurrentripple;consequently,the
componentswithhigherratingshavetobechosenandtheefficiencyofthepowersystemwill
be low, due to the increase in the switching losses. Therefore, for such an application, an
isolatedbidirectionalconverterhas tobe implemented.Galvanic isolation isalsoneeded for
safety concerns and electromagnetic compatibility reasons. The use of such isolated bi
directionalDCDCconvertershasthepotentialtoimprovetheoverallefficiency,fueleconomy,
reliabilityandsafetyofthemultifunctionalpowersupplysystem.
2.1 Isolated DC-DC Buck Converter
LikeinadirectDCDCbuckconverter(showninFigure2),theoutputvoltageinanisolatedbuck
converterisalsocontrolledbythedutyratioD=ton/TS=ton.fS(dutyratioisalwaysintherange
0
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FrancMihaliandAlenkaHren JETVol.3(2010) Issue3
(a)
(b)
Figure3:(a)Thedrivingsignalsinbuckconverter.(b)Blockdiagramofthecontrolschemeforthebuckmodeofoperation.
TheparametersofbothPIcontrollershavebeendesignedbyusingRoot LocusMethod and
smallsignal CCM converter transfer functions [7]. The startup of the isolated DCDC buck
converterwithnoloadandfulltohalfloadoperationisshowninFigure4(a).
0 0.1 0.2 0.3 0.4 0.50
10
20
30
UBattery
[V]
Start-up + full load 50%
0 0.1 0.2 0.3 0.4 0.50
50
100
150
IBattery
[A]
0 0.1 0.2 0.3 0.4 0.50
1000
2000
3000
4000
PLoad
[W]
(a)
0.1 0.15 0.2 0.25 0.3 0.35 0.4 0.45 0.5 0.5525
26
27
28
29
30
UBattery[
V]
Output voltage - zoom
(b)
Figure4:(a)Startup,fulltohalfloadoperationandshutdownoftheisolatedbidirectionalDCDCconverterinbuckmode:outputvoltage(top),outputcurrent(middle)andoutputpower
(bottom).(b)Outputvoltageiswithinthe5%limits.Itisevidentthatwiththechosencontrolschemetheoutputvoltageremainswithinthe5%of
the28Vevenat the fullloadoperationat0.15 s (seeFigure4(b)).At50% load (from0.3s
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IsolatedbidirectionalDCDCconverter
0.4s), the results are even better, which confirms the efficiency of the cascade control
structure.Itisalsoevidentthat,whentheshutdownoftheconvertersoccursatfullload,the
outputvoltagedecreasesrapidlyandwithoutovervoltagespikes.
2.2 Isolated DC-DC Boost Converter
The same configuration (shown in Figure 2) can operate in the opposite direction, i.e., it can
boostthebatteryvoltagetoahighDClinkvoltagewhentheMOSFETsfullbridgeconverter is
drivenintheappropriatemanner,dependingonthedutyratioDandtransformersturnsration
as:
(1 )
Bat
DC
nUU
D (2)
Like
a
direct
boost
converter,
an
isolated
boost
converter
also
has
a
start
up
problem.
At
the
beginning, the bulk input capacitors are empty (UCo = 0V and UDC = 0V); if we start the
converter in boost mode, the control unit will put the maximum duty ratio to the MOSFETs
switches to keep pumping energy into the inductor Lk. Since the output voltage is zero, the
inductorcannotbedischarged;asaresult,the inductorwillbesaturatedandthecurrentwill
(theoretically)gotoinfinity.Ifoverloadconditionoccurs(orimmediateshutdown),onecannot
simplyturnoffalltheswitches,becausetheenergystoredintheinductorcannotgoanywhere,
anditwillgeneratehighvoltagespikes,whichdestroytheswitches.
Onepossible(and lowcost)solutionforsolvingproblemsatthestartupprocedureistousea
chargingresistor forthe inputcapacitorCo (RP),asshown inFigure2 (thesamecouldalsobe
appliedto
the
bulk
capacitor
CDC
at
the
high
voltage
terminals
through
an
adequate
charging
resistor). The charging currents are limited through the resistance, but when isolation is lost
therearecertainlossesandthecircuitisnotprotectedagainstoverloadandshutdownduring
theoperation.
At high power levels, output rectifiers (in our case D1D4 and D2D3) in continuouscurrent
mode(CCM)boostconvertershaveseverereverserecoveryproblemsduetothehighrectifier
forwardcurrentand the high output voltage.Asa result, the activeswitches encounter huge
turnon current spikes, which are not only responsible for high turnon loss but also cause
severeelectromagneticinterference(EMI)noise.Toreducetheswitchinglosses,theoperating
frequency of the CCMboost converter must be reduced. However, reducing the operating
frequency
is
not
a
good
solution
in
terms
of
power
density,
cost
and
efficiency.
An
effective
solution to alleviate rectifier reverserecovery problems is proposed in [8]. By using only one
additionalrectifierandcoupledwindingontheboostinductor,thecurrentthroughtheoriginal
rectifiercanbesteeredtoanewbranch.Withproperdesign,thecurrentthroughtheoriginal
rectifiercanbereducedtozerobeforetheboostswitchturnson.
A similar solution for the aforementioned problems during the startup procedure and shut
downprotection,inisolatedbidirectionalDCDCconverterrunninginboostmodeisshownin
Figure 2, where acouplingwinding is added to the inductor Lkand an additionaldiode DS1 is
connected to the output terminal. First, input capacitor Co must be charged through the
charging resistor Rp (with auxiliary contactor K
2 on). When the input capacitors voltage has
reachedthebatteryvoltage C Bat U U ,themaincontactorK1canbeturnedon.Nowthestartup
procedurecanbegin:thedrivingpulsesfortheMOSFETsareshowninFigure5(a)withtheduty
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ratiofrom0to50%forbothlegs(whenthestartingreferencevoltagereachesUStart,Ref=1)and
theoutputvoltageis:
2
Bat
DC
U
U nD
(3)
With thisscheme, theconvertercanoperate inflybackmodeduringstartup,and transfer
theenergystoredinthemaininductorLktothebulkcapacitorCDCattheDClinkcircuit.Asina
buck converter,whole system has inner, currentPIcontroller for theprimary current Ip and
outer,voltagePIcontrollerfortheDClinkvoltageUDC,asshowninFigure5(b).Theparameters
ofbothPIcontrollershavebeendesignedbyusingtheRootLocusMethod.ThedesignofthePI
current controller parameterswas performed using the transfer function that describes the
relationshipbetweentheinductorcurrentandthedutyratio.
(a)
(b)
Figure5:(a)Startupdrivingsignalsinboostconverter.(b)Blockdiagramofthecontrolschemeforboostmodeofoperation.
Now, theentiresystem is ready for investigation:PWMdrivingpulses foreachMOSFETs leg,
inductor voltage and output voltage of the boost converter (i.e., secondary voltage of the
transformer)areshowninFigure6(a).Itisevidentthattheinductorvoltageisbuildingupina
positivedirectionwhenM1andM4areconducting;thisvoltageisnegative,whenM2andM3are
active. As seen in Figure 6(a), the output voltage of theDCDC boost converter US (i.e. the
secondaryvoltageofthetransformer)isalternative;therefore,itcanbetransformeduptothe
highvoltageprimaryside,where it isrectified throughthebodydiodesD1 toD4ofthe IGBTs
fullbridge
converter.
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IsolatedbidirectionalDCDCconverter
0.08 0.08 0.08 0.08 0.08 0.0801 0.0801 0.0801 0.0801 0.08010
0.5
1
P
WMM1,PWMM3
Driving pulses: start-up
M1
M3
0.08 0.08 0.08 0.08 0.08 0.0801 0.0801 0.0801 0.0801 0.08010
0.5
1
PWMM2,PWMM4 M
2
M4
0.08 0.08 0.08 0.08 0.08 0.0801 0.0801 0.0801 0.0801 0.0801-20
-10
0
10
20
ULk,Us
[V]
Inductors voltage
ULk
Us
(a)
0 0.05 0.1 0.15 0.2 0.25 0.3 0.350
150
300
450
UDC-Linka
[V]
Start-up + min. load
0 0.05 0.1 0.15 0.2 0.25 0.3 0.350
50
100
150
200
IBat
[A]
0 0.05 0.1 0.15 0.2 0.25 0.3 0.350
1000
2000
3000
4000
5000
PIN,POUT
[W] P
IN
POUT
(b)
Figure6:(a)Startupoftheboostconverter:drivingpulsesineachMOSFETsleg,inductorvoltage
and
output
voltage
of
the
converter
(US).
(b)
Start
up
operation
with
minimal
load:
outputvoltage(top),inputcurrent(middle)andinputandoutputpower(bottom).
Duringthestartup(from0to0.2s),theHVDClinkvoltageincreaseslinearly(seeFigure6(b)),
even though the input current ILk isdiscontinuous (as shown in Figure7(a)).Notice that the
boost converter works in flyback mode only during the startup procedure. The coupling
windingandtheprotectiondiodeDS1donotoperateduringthenormalboostmode.Therefore,
theadditionalwindingonthemaininductorandappliedprotectiondiodecanbesmall.
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0.19 0.19 0.19 0.19 0.1901 0.1901 0.1901 0.1901 0.1901 0.1901
-100
0
100
Up
[V]
Boost converter: start-up
0.19 0.19 0.19 0.19 0.1901 0.1901 0.1901 0.1901 0.1901 0.19010
20
40
UDS4
[V]
0.19 0.19 0.19 0.19 0.1901 0.1901 0.1901 0.1901 0.1901 0.19010
1
2
IDs1
[A]
0.19 0.19 0.19 0.19 0.1901 0.1901 0.1901 0.1901 0.1901 0.19010
4
8
1212
ILk
[A]
(a)
0.46 0.46 0.46 0.46 0.46 0.4601 0.4601 0.4601 0.4601 0.46010
0.5
1
PWMM1
Driving pulses in boost mode
0.46 0.46 0.46 0.46 0.46 0.4601 0.4601 0.4601 0.4601 0.46010
0.5
1
PWMM2
0.46 0.46 0.46 0.46 0.46 0.4601 0.4601 0.4601 0.4601 0.4601-20
-10
0
10
20
30
ULk
[V]
Inductors voltage
(b)
Figure7:(a)StartupoftheisolatedbidirectionalDCDCconverterinboostmode:primaryvoltage,UDSoftheM4,currentthroughtheprotectiondiodeDS1andmaininductorLk.(b)Normal
operationoftheisolatedbidirectionalDCDCconverterinboostmode:drivingsignalsandthe
inductor'svoltage.
TheoperationofthewholesystemintheboostmodeoperationcanbeobservedinFigure7(b).
Duringthenormalboostoperation,the inductorsvoltagewaveform isequaltotheULk=UBat
within the turnon time and then equal to the ULk=UBatUDC/nwithin the turnoff time.As
predicted,thewholesystem isoperatingstablyduringthestartupwithminimal load(i.e.,for
safety, there are always minimal load resistances Rp1 and Rp2 connected in parallel to the
capacitorsterminals;seeFigure2),aswellwithfullload(orhalfload).Furthermore,immediate
shutdownisnotdangerous(asshowninFigure8(a)andwithcloseexaminationoftheoutput
high
voltage
terminals
in
Figure
8(b)).
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IsolatedbidirectionalDCDCconverter
0.35 0.4 0.45 0.5 0.55 0.6 0.65 0.70
150
300
450
UDC-Linka
[V]
Full load 50% + shut-down
0.35 0.4 0.45 0.5 0.55 0.6 0.65 0.70
50
100
150
200
IBat
[A]
0.35 0.4 0.45 0.5 0.55 0.6 0.65 0.70
1000
2000
3000
4000
5000
PIN,POUT
[W]
PIN
POUT
(a)
0.35 0.4 0.45 0.5 0.55 0.6 0.65 0.7420
430
440
450
460
470
480
UDC-Link
[V]
Output voltage - zoo m
(b)
Figure8:(a)Steadystateoperationwithfull/halfload:outputvoltage(top),inputcurrent(middle)andinputandoutputpower(bottom).(b)Outputvoltageiswithinthe5%limits.
Whenovervoltage(orimmediateshutdown)occurs,alloftheMOSFETswitchescanbeturned
off because the energy stored in themain inductor can find itsway through theprotection
diodeDS1totheoutputcapacitorCDCwhere it isusedbythe load,asconfirmed inFigure9(a)
and(b),respectively.
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0 0.1 0.2 0.3 0.4 0.5 0.6 0.7
0
2
4
6
8
10
12
14
16
18
IDS1
[V]
Current through the protection diode
(a)
0 0.1 0.2 0.3 0.4 0.5 0.6 0.7-800
-700
-600
-500
-400
-300
-200
-100
0
UDS1
[V]
Protection diode voltage
(b)
Figure9:(a)CurrentthroughtheprotectiondiodeDS1duringstartupandatshutdown.(b)VoltageatprotectiondiodeDS1duringstartupandatshutdown.
Based on the resulting waveforms in Figure 9(a),(b) the current and voltage rate of the
protection diode DS1 can be chosen below 10A and 1000V, respectively. For other
characteristics,theswitchingspeedisveryimportant,whichleadstothedecisionthataShottky
diode should be used. The dissipation in this diode is limited,whichmeans that no special
coolingofthedeviceisrequired.
3 EXPERIMENTAL SETUP AND RESULTS
In order to verify all the published theoretical background and the simulation results in the
previoussection,
an
experimental
prototype
of
the
bi
directional
DC
DC
power
converter
proposedinFigure2wasbuiltandispresentedinFigure10.
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IsolatedbidirectionalDCDCconverter
Figure10:PrototypeofthebidirectionalDCDCconverter.
The simulation results, obtained by the exact model of the complete converter within the
Matlab Simulink (shown in Figure7(a)) and theexperimental results (Figure11) are in good
agreementduringthestartupoftheboostconverter.Thesystemwasalsotestedunderhigher
loadconditions; results for UDC=450Vand Po=1000Ware shown inFigure12. It isevident
thatthesystemisfunctioningstablyandwithinthepresumptionsgivenatthebeginningofthis
paper.Furtherinvestigations,measurementsandoptimizationsareinprogress.
Figure11:Experimentalresultsstartupoftheboostconverter:CH1:IDS1(1A/div),CH2:ILk(10A/div),CH3:UDS4(40V/div),CH4:Up(200V/div),timebase(10s/div).
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Issue3
Figure12:Experimentalresultssteadystateoftheboostconverter:CH1:ULk(40V/div),CH2:ILk(20A/div),CH3:UDS4(40V/div),CH4:Up(200V/div),timebase(10s/div).
4 CONCLUSION
Thenew
full
bridge
topology
of
the
isolated
bi
directional
DC
DC
converter
has
been
proposed
and its safe operation has been discussed. The drawbacks of the conventional converter
topologiesduring startup inbuckandboostmodesofoperationhavebeenpresented,and
solutions for safe startupshavebeenproposed.The solutionsarebasedon theadditionof
couplingwinding to the inductor and anextradiode connected to theoutput terminal. The
operationoftheproposednew topologyhasbeenverifiedbysimulationsandexperimentally
validated; the results are in good agreement. Based on this procedure, the building of the
prototypewasmucheasierwithfewerunexpectedobstaclesandproblems.
References[1] Tolbert, L.M., Peterson, W.A., Scudiere, M.B., White, C.P., Thesis, T.J., Andriulli, J.B.,
Ayers,C.W.,Farquharson,G.,Ott,G.W.,Seiber,L.E.: Electronicpower conversion system
foranadvancedmobilegeneratorset,IEEEIAS2001AnnualMeeting,Chicago,IL,pp.1763
1768,2001.
[2] Tolbert,L.M.,Peterson,W.A.,White,C.P.,Thesis,T.J.,Scudiere,M.B.:AbidirectionalDC
DC converter with minimum energy storage elements, IEEE IAS 2002 Annual Meeting,
Pittsburg,PA,pp.15721577,2002.
[3] Virti,P.,Piek,P.,tumberger,B.,Hadiselimovi,M.,Mari,T.:Axialfluxpermanent
magnet synchronous generators for wind turbine applications,Journal
of
Energy
Technology,vol.2,issue2,pp.6574,2009.
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IsolatedbidirectionalDCDCconverter
[4] Krismer,F.,Biela,J.,Kolar,J.W.:AcomparativeevaluationofisolatedbidirectionalDC/DC
converters with wide input and output voltage range, IEEE 40th Industry ApplicationsConference,2005,vol.1,pp.599606,2005.
[5] Garcia,O.,Flores,L.A.,Oliver,J.A.,Cobos,J.A.,Pea,J.:Bi
directional
DC/DC
converter
for
hybrid vehicles, IEEE36th
PowerElectronicsSpecialistsConference,2005,pp.18811886,
2005.
[6] Usenik, J.: Mathematical model of thepower supply system control, Journal of Energy
Technology,vol.2,issue3,pp.2946,2009.
[7] EriksonR.W.,Maksimovi,D.:FundamentalsofPowerElectronics,secondedition,Kluwer
AcademicPublishers,2001.
[8] Zhao,Q.,Tao,F.,Lee,F.C.,Xu,P.,Wei.,J.:Asimpleandeffectivemethodtoalleviatethe
rectifierreverserecoveryproblemincontinuouscurrentmodeboostconverters,IEEETrans.
PowerElectron.,
vol
16,
pp.
649658,
Sept.
2001.
Nomenclature
(Symbols) (Symbolmeaning)
D dutyratiofS switchingfrequencyn transformersturnsratioton turnontimeoftheswitchTS switchingperiodUBat batteryvoltageUDC DClinkvoltage
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JETVolume3(2010),p.p.4152
Issue3,August2010
www.fe.unimb.si/si/jet.html
CLEAN COAL TECHNOLOGIES AT
VELENJE COAL MINE
ISTE PREMOGOVNE TEHNOLOGIJE NAPREMOGOVNIKU VELENJE
SimonZavek,LudvikGolob,Janjaula
Keywords:coal,bestavailabletechnologies,energyefficiency,degasification,capture,transportandstorageofCO2,undergroundgasificationofcoal.
Abstract
The importance of coal is growing again after a rather long period in which it was notcompetitiveagainstoilandnaturalgasasanenergyresource.
Thereare importantreasonsforthis:priceperenergyunit,thedispersionofglobalresourcesand the relationbetweenglobal resourcesandconsumption.ThedevelopmentofCleanCoalTechnologies(CCT),friendliertoenvironment,keepscoalcompetitive.
Theintroductionandapplicationofnewandmodern,bestavailabletechnologies(BAT)enablekeepingasubstantialpartofpowersupplyincoalcombustionirrespectiveoftheincreasinguseofrenewableresourcesandincreasedenergyefficiency.
Infuture,
new
CCT
will
play
akey
role
in
assuring
sufficient
power
production
around
the
world
andintheEU.
AttheVelenjeCoalMine,weareawareoftheproblemsoccurringbecauseofgreenhousegasemissions.Therefore,we launchedaresearchprojectonCCT in2007.Thisproject istoapplythebestavailabletechnologiesthatshouldcontributetomorerationalcoalextraction,bettersafetyatworkandimprovedworkingconditions,aswellassolvingtheenvironmentalproblemsofcoalgases.
Correspondingauthor:SimonZavek,PhD.,CoalMineVelenje,Tel.:+38638996274,Fax:
+3863586
9131,
Mailing
address:
Partizanska
cesta
78,
SI
3320
Velenje,
address:
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SimonZavek,LudvikGolob,Janjaula JETVol.3(2010) Issue3
Thispaperpresentstheplansforthecleanerproduction,preparationandutilizationofcoal.In
the framework of power generation, these plans enable the conditions for the transfer of
knowledge,researchresultsandtechnologiesintoworkingpractice.
Regarding itsdefinition,theconceptofCCT isverywide;however,theresearchprojectattheVelenje Coal Mine consists of three main technologies: Lignite Degasification; the Capture,
TransportandStorageofCO2;andUndergroundCoalGasification.
Accomplishing these,we intend to come closer togoalsofCleanCoalTechnologies, thereby
improvingtheefficiencyandenvironmentalacceptabilityofligniteproduction,preparationand
use.
Povzetek
Po dokaj dolgem obdobju, koje bil premog kot energent v primerjavi z nafto in zemeljskim
plinomnekonkureneninzaraditegamanjzanimiv,senjegovpomenvzadnjemasuspetvea.
Razlogovjeve,insicer:cenanaenotoenergije,razlinarazprenostglobalnihzaloginrazmerje
medsvetovnimizalogami inporabo.Prednostpredkonkurentomamuzagotavljarazvojnovih,
ekoloko bolj prijaznih tehnologij uporabe premoga, tako imenovanih istih premogovnih
tehnologij (Clean Coal Technologies). Zaradi uvajanja in uporabe novih modernih tehnologij
(BAT)bo, kljub veji rabiobnovljivih virov in vejienergetskiuinkovitosti,mogoeeprecej
asaohranjati znatendeleoskrbe zelektrinoenergijo izpremoga.Nove iste premogovne
tehnologijebodovbodoe igralekljunovlogoprizagotavljanjuzadostnihkoliinproizvedene
elektrineenergijetakoposvetukottudivEUindoma.
KersenaPremogovnikuVelenjezavedamoproblemov,kijihpredstavljajoemisijetoplogrednihplinov (TGP), smo e leta2007ustanovili razvojniprojekt, kije ciljno in razvojnonaravnan v
aplikacijo najboljih tehnologij, ki bodo prispevale k racionalizaciji procesa pridobivanja
premoga,zagotavljanjuvejevarnostiinhumanostiterreevanjuokoljskihproblemov.
Vprispevkusoobravnavaniinprikazaninartizapodrojeisteproizvodnje,predelaveinizrabe
premoga, ki v okviru proizvodnje elektrine energije zagotavljajo pogoje za prenos znanj,
rezultatovraziskavintehnologijvprakso.epravjepojemistepremogovnetehnologijeglede
na definicijo velikoiri, pa razvojni projekt na Premogovniku Velenje v tej fazi vsebuje tri
pomembneje sklope, in sicer: razplinjevanje lignita, zajem, transport in skladienje CO2 in
podzemnouplinjanjepremoga.Zrealizacijonavedenihsklopovsenameravamopribliaticiljem,
ki jih obsegajo iste premogovne tehnologije in so izboljanje uinkovitosti in okoljskesprejemljivostipridobivanjalignita,njegovepredelaveinizkorianja.
1 INTRODUCTION
Irrespectiveofgrowinguseofrenewableenergyresourcesandbetterenergyefficiency,oil,gas
andcoalwillrepresentasubstantialpart in thepowersupply for the foreseeable future.The
importanceofcoal isgrowingagainafterarather longperiod inwhich itwasnotcompetitive
againstoilandnaturalgasasanenergyresource.Therearesome importantreasons for this:
price per energy unit, the dispersion of global resources and the relation between globalresourcesand consumption.CleanCoalTechnologiesare friendlier toenvironmentand their
development also enables the coal consumption for future power generation. Coalbased
power generation represents more than 40% of global energy production, Kessels, [7]. The
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authorcitesmanyreasonsforthat.Amongthese,isthefactthatthecoalisoftenastate'sown
energyresource,therebyenablingenergysecurityand independence.Thenextreasonrelates
toglobalcoalproductionandconsumption (reaching6Gt),bearing inmind that,contrary to
other
primary
energy
resources,
coal
resources
are
abundant.
Kessels
notes
that
coal
resources
inAlaskareachover5Gt,i.e.,morethan40%ofcoalresourcesintheUSA.
Figure1showstheenergyproductionforecastto2030;itcanbeseenthatthecoal,inaddition
tonuclearpowerand renewable resources (togetherwithenergyefficiency), isplayingakey
roleinassuringsufficientpowerproduction,Tanaka,[9].Globalpowerdemandwillriseby45%
until2030,withtheaverageannualrise isestimatedat1.6%.Theshareofcoal isonethirdof
theentiregrowth.Thisforecastwasdesignedbeforetheeconomiccrisisandthereforedoesnot
reflectitseffects.
Figure1:Energyproductionforecasttill 2030(reference scenario, IEA [6]
2 CLEAN COAL TECHNOLOGIES
CleanCoalTechnologies(CCT)aretiedtotechnologicalprogress leadingtomoreefficientand
environmentally friendly coal consumption. The plan and explanation of Clean Coal
TechnologiesfollowtheDTI/IEA1999standard,DTI/IEA[2].AsseeninFig.2,theconceptisvery
wideandincludes:
a) Coalproduction,preparation,transportandcoalyard;
b) Unconventional coal production through Underground Coal Gasification (UCG) or
extractingmethane fromundergroundcoalseams, i.e.,CoalBedMethaneExtraction
(CBME);
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c) Power generation through combustion of pulverised coal, i.e., Pulverised Fuel
Combustion(PC);
d) Power generation through coal gasification, i.e., Integrated Gasification Combined
Cycle(IGCC);
e) Otherpossibleadvancedtechnologies,suchashybridcombinedcycles,heatengines,
fuelcells;
f) Industrial and domestic use of coal in steel production, cement industry, heating
plants;
g) Othertechnologiesthatturncoalintoenergy,suchasliquefactionorbriquetting;
h) Combustion remains use: fly ash, clinker, gasification remains, gas cleaning remains
(gypsum);
i)
otherclean
CCT
possibilities
including
co
combustion
of
natural
gas,
biomass,
co
generationandcapture,transportandstorageofCO2,i.e.,CarbonCaptureandStorage
(CCS).
Figure2:DiagramofCCT(adaptedaftermethodologyofDTI/EIA1999)
Theprocess
of
lignite
production
at
the
Velenje
Coal
Mine
includes
the
activities
of
coal
extraction, coal preparation, coal transport, coal yard (A), combustion remains use; in the
nearby thermalpowerplantTEotanj theprocessofpowergenerationwithpulverizedcoal
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CleancoaltechnologiesatCoalmineVelenje
combustion is mastered (C). According to the Clean Coal Technologies Project, we are
incorporatingsomeother fields, includingundergroundcoalgasificationpossibilitiesandcoal
bedmethane (B),powergeneration throughcoalgasification (D)additionalcleanpossibilities
(I).
3 DEVELOPMENT PROJECT CCT AT VELENJE COAL MINE
Accordingto longtermproductionplanof lignite inVelenjeCoalMine,projectedto2045and
presently assuring a 30% shareof Slovenia's power production,we decided to follow global
trends and founded aproject group to dealwith these problems at the end of 2007. Fig. 3
shows the Clean Coal Technologies project's three sections: Lignite Degasification, Capture,
TransportandStorageofCO2andUndergroundCoalGasification.
3.1 Lignite degasification
Lignitedegasification isobtainingmethane intheprocessof lignitedegasification.Asthecoal
gas of theVelenjemine containsmethane in addition toCO2,we plan to capture both and
therefore the part section of the project is referring also to activity I, i.e., other clean
possibilities(CO2captureandstorage).Regardingthefactthatdegasificationofthincoalseams
haslongbeenanunderstoodandpracticedprocedure,theVelenjeCoalMinewillfocusonthe
degasificationdevelopmentofaverythickcoalseam.Weplantodegasifytheexcavationpillars
beforecoalexcavationwiththelongwallmethod.
Oneof
the
goals
of
the
degasification
project
should
be
the
development
of
astatement
on
the
developmentandapplicationofthebesttechnologiesthatcontributetotherationalizationof
thecoalextractionprocess.Degasificationdiminishestheamountofgasattheactive longwall
face and positively affects production. Reduction of gas amounts in the excavation pillar
contributes tobettersafetyandworkingconditions,as the reducedgasconcentrationsallow
reduced air volumes and, in consequence, ventilation that is more rational and has fewer
problemswith coaldust. Theproject isdivided into the technological,and the research and
developmentparts. In the technologicalpart, theSlovenianprojectpartners inaconsortium.
Thedevelopmentpartoftheprojectisconstitutedinternationallyandregisteredforcofunding
withtheRFCS(ResearchFoundforCoalandSteel)fund.Bothprojectswilllastforthreeyears,
startingwith
the
developmental
part,
followed
by
the
project
itself.
Project
activities
will
consist
ofarevisionofbasiccoalseamandexcavationdata,fieldandlaboratoryresearchofimportant
coalseamcharacteristics, insitumeasurementsandanalysisof the longwall faceadvanceonstresses, gas pressure, gas permeability and gas diffusion. The project foresees monitoring
activities too.Common interpretationandnumericalmodellingof fieldand laboratory results
fordegasificationplanningandgasoutburstcontrolwillfollow.Theprojectwillconcludewitha
pilottestdrainingmeantasasystemforcontrolleddegasificationandcontrolofgasoutbursts
atcoalexcavationofverythickcoalseams.
Throughthecoordinationofresearchprojectssuchasgascomponenttracking,Velenje lignite
petrography, and the structuralmodel, and through doctoral study education, the research
resultsof
other
projects
are
also
incorporated
into
the
project.
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Figure3:SchemeofCleanCoalTechnologiesProject(Zavek,[12])
3.2 CO2 capture, transport and storage (CCS)
Ingeneral,theCO2gasfrompowerplantsand industrialunitsmustbecaptured,compressed
andtransportedtotheareaswheresufficientlydeepstorageispossible.TheCO2sourceiscoal,
gas, oil and biomass combustion. Themajor part of the CO2 results from power and heat
production,fromchemicalplants,steelandcementproduction.CCStechnologyrepresentsthe
key to safe fossil fueluse, and therefore remains a realoption for transitioningbeyond the
periodof
intensive
fossil
fuel
use,
Kessels,
[7].
Theknownfossilfuelresourcesintheworldcontainahugeamountofcarbonthatwillthreaten
theatmosphere.Thedescribedtechnologycanhelptorealizeplansfordiminished increaseof
CO2intheatmosphere.
Thesituationconsideringtheaverageefficiencyandemissionsperproducedenergyunit isas
follows:world28%(1110gCO2/kWh),EU36%(880gCO2/kWh).Today,thereachablePCorIGCC
TEtechnologiesarenearingtheefficiencyof42%andemissionsof740gCO2/kWh.
A very important shorttermmeasure is to increase theefficiency. The goals for the further
technologicaldevelopmentuntil2020 areheading towards48% and665 gCO2/kWh,but the
essentialemissions
decrease,
which
is
expected
after
2020,
will
require
commercially
affordable
CCStechnologies(Tanaka,[9],afterVGB2007:efficiencyHHV.net,Topper,[10]).
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InEurope,morespecificallyinGermany,theplansforpilotanddemonstrationCCSprojectsare
readyandsomeofthemarealreadyrunning,Hll,[4].
Capture,transportandstorageofCO2areatVelenjeCoalMineplaced intothesecondpartof
theClean
Coal
Technologies
Project
complex.
Activities
coordinated
by
HSE
(Holding
of
SlovenianPowerPlants)areapartoftheprojectcalledImplementationoftheClimateEnergy
PackageinSlovenianThermalEnergy(ZETePO)withthegoalofreducingGHGemissionsinthe
postKyotoera(Fig.4).
Figure4:SchemeoftheZETePOproject
Besides thecoordinatorandproject leaderHSE, theSlovenian thermoenergycompaniesand
MOP (Ministry for Environment and Spatial Planning) and MG (Ministry for Economy) are
involved.The
ZETe
PO
project
is
divided
into
two
sub
projects:
the
first
includes
CCS
(Carbon
Capture and Storage) technologies and the second IGCC (Integrated Gasification Combined
Cycle) technologies. The first subproject is interesting for theVelenjeCoalMinebecauseof
geologicalCO2storage, implementationofEU legislationcoveringCCS, implementationofCCS
legislationinSloveniaandactivecooperationintheETPZEP.Theprojecthasbeenlaunchedand
is in thephaseof collecting tenders forproject tasks and applicationof cofundingof single
projects in different EU programmes. In recent years, the Velenje Coal Mine funded and
cooperated inCO2storageresearchwherethepossibilitiesofstorage ingeologicalformations
andprimarilythecoalseamwerestudied,Oreniketal.,[8].
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3.3 Underground coal gasification
The underground coal gasification, representing the third part of our project, is an
unconventional typeofcoalutilization. Ingeneral, theprocedure isquitesimple,asonly two
boreholes(or
two
wells)
are
needed
(Fig.
5).
Through
the
injection
well,
air
and
steam
are
broughtunderpressureintothecoalseamwherethecombustionbegins.Theproductionwellis
usedtoobtainthegas,calledsyntheticgasorsyngas.Themaincomponentsofsyngasare
hydrogen and carbon monoxide. The underground coal gasification (UCG) technology is very
complexanddemandingas themost successful tests in theworldhave shown.UCGneedsa
multidisciplinary approach of geology, hydrogeology, chemical engineering, chemistry and
thermodynamics.
The most interesting advantage of the UCG will be economic, because minor operative and
investmentcostsare foreseen.Thenextadvantageshouldbe theflexibleuseofsyngas.Even
the environmental view is considered advantageous, as most combustion products remain
underground,including
heavy
metals
SOx,
and
NOx,
Couch,
[1].
The
costs
for
CO2separationare
minor; there may be possibilities for carbon storage in the cavities or adjacent rocks. The
disadvantagesof theUCGare theoperational risksdue to the lackof tested largescaleUCG
trialsand the frequentproblems thathaveoccurredduring tests in theUSAandEurope.The
process can be uncertain considering environmental impacts and public acceptability. The
possible disadvantages may be the ground water pollution (contamination) and surface
subsidence.TheUCGproductcanbeused indifferentways:cogeneration,gas turbine, from
coaltoliquidsetc.
Figure 5:Sketch oftheundergroundcoalgasificationprocedure (UCG
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CleancoaltechnologiesatCoalmineVelenje
RegardingUCG,theVelenjeCoalMinehasa longerhistory. Inthe late1950s,astudyonUCG
possibilitiesinthelignitedepositsofformerYugoslaviawascompletedattheChemicalInstitute
inLjubljana(KemijskiintitutuBorisaKidria)Inthe1980s,somelaboratorytestingwasdoneon
smaller
samples
as
well
as
bigger
samples
of
Velenje
lignite,
Eberl,
[3].
In
2002,
a
feasibility
studyofUCG inVelenjeCoalMinewasnotentirely completed,but the finished component
partscomprisethepreliminarydepositevaluation,depositevaluationwithanalysisofexistent
data(generaldata,geology,hydrogeology),additionalresourcecharacterization,technological
difficultiesof theprocess,and technologicaldifficultiesofdepositpreparation.The studydid
notexaminetheissuesofprocessproductuse,environmentalsusceptibility,economyandfinal
evaluation.
ThroughthethirdsectionoftheCleanCoalTechnologiesProjectatVelenjeCoalMine,thetask
forcehasbeen revivedand the feasibility study continuedwith themissingparts. Important
factorsarediscussedincludeprocessproductuse(quantityandqualityoftheproduct,product
qualityoscillation,sizeoftheenergeticstructure,andenergeticuseoftheproduct),economyand finalevaluation. Incontinuation theactivitieswill run toprepare theproposalofproject
task for pilot UCG test in Velenje, to gain the concession for research of coal in Goriko
(Slovenia)andtoprepareaproposalofprojecttaskforpilotUCGtestinGoriko,Zavek,[12].
3.4 Conclusion
ThroughrealizationofthegoalsoftheCleanCoalTechnologiesProject,thewaytodevelopment
andapplicationofbestavailabletechnologiesispaved.Thiswillcontributetomorerationalcoal
extraction,bettersafetyatwork,betterworkingplaceconditionandsolvingtheenvironmental
problemsregardingcoalgases.
Inthe fieldsofcoalproductionandconventionalorunconventionalcoalutilization,theClean
Coal Technologies Project brings conditions for transfer of knowledge, research results and
technologies into practicalwork. Based on the realization of the research and development
phasesof the technologiesdiscussed,we can continue to follow innovation; the task force's
work isaimedattheacquisitionofnationalandEuropeanresearch fundsandtheopeningof
marketpossibilities.
References
[1] GRCouch,2009.Progresswithundergroundcoalgasification (UCG),IEACleanCoalCentre,London,2009.UK.
[2] DTI/IEA(1999).CleanerCoalTechnologies:Options.DepartmentofTradeandIndustry.
London, England (1999). International Energy Agency, Organisation for Economic
CooperationandDevelopment.Paris,France(1999).
[3] E. Eberl, 1986.Nova tehnologijapridobivanja inpredelavepremoga podzemeljskouplinjanje,Rudarskometalurkizbornik,Vol.33No.12,str.7388.
[4] A.Hll,2009.COORETEC:TheGermanR&DInitiativeforCleanCoalTechnologies,4thInternational Conference on Clean Coal Technologies CCT 2009, 1821 May 2009Dresden,Germany.
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[5] IEA(2007).Worldenergyoutlook2007:Chinaand India insights. InternationalEnergyAgency, Organization for Economic Cooperation and Development, Paris, France
(2007).
[6] IEA (2008).World energy outlook 2008:Global energy trends to 2030. InternationalEnergy Agency, Organization for Economic Cooperation and Development, Paris,
France(2008).
[7] J. Kessels,2009.Emission trading; incentiveorobstacle tofundingofcarboncaptureand storage demonstration projects, 4
th International Conference on Clean Coal
TechnologiesCCT2009,1821May2009Dresden,Germany.
[8] K. Orenik, B. Justin, Z Mazej, 2006. Monosti trajnega skladienja ogljikovegadioksida:poroilozaleto2005.Velenje:ERICo,februar2006.Slovenija.
[9] N. Tanaka, 2009. What Role for Coal in a Carbon Carbonconstrained World? 4thInternational Conference on Clean Coal Technologies CCT 2009, 1821 May 2009
Dresden,Germany.
[10] J.Topper,2009.IEACleanCoalCentreMembers,4thInternationalConferenceonCleanCoalTechnologiesCCT2009,1821May2009Dresden,Germany.
[11]A.Zapuek,ssod.,2009.tudijaomonostipodzemnegauplinjanjapremoga,3.faznoporoilo, IREET, Intitut za raziskave v energetiki, ekologiji in tehnologiji, d.o.o.,
september2009,
Ljubljana.
[12]S. Zavek, 2009. iste premogovne tehnologije na Premogovniku Velenje, 1.mednarodna konferenca:ENERGETIKA IN KLIMATSKE SPREMEMBE , 1.7.3.7.2009
Velenje,Slovenija.
[13]S.Zavek,J.ula,2009.Razplinjevanje lignitavPremogovnikuVelenje,PP,september2009,Velenje,Slovenija.
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JETVolume3(2010),p.p.5366
Issue3,August2010
http://www.fe.unimb.si/si/jet.html
ENERGY POLICY FOR PRODUCTION
RESOURCES
ENERGETSKA POLITIKA ZA PROIZVODNE
VIRE
DragoPapler,tefanBojnec
Keywords:competitiveness,efficiency,renewablesourcesofenergy,energypolicy,education,sustainabledevelopment,factoranalysis
Abstract
TheRepublicofSlovenia'smostrecentenergypolicy,withtheadoptionoftheclimateenergypackageandobligationsoftheEuropeanUnion,givesgreaterimportancetoalternativesourcesof energy and to climate change. How realistic it is to set an obligation for a 20% share ofrenewablesourcesofenergyintheprimarystructureofenergyby2020ortheevenhigher25%sharesetinSlovenia?
Surveys, using a written questionnaire, were conducted among the managers in the energysector, focusingoncompetitiveness in supply,efficientuseofenergyand sourcesofenergy.Withthisresearch,wehaveanalysedtheopinionsamongexpertsonthesequestions,andwecomparetheresultswiththeothersurveyedgroupsfromthesocialsciences,naturalsciences,
andelectrical
energy
education.
The
methods
of
the
analysis
used
are
descriptive
statistics
with
calculations of mean values, correlation analysis and multivariate factor analysis, which arebasedonthesurveydata. Intheresearch,we findassociationsbetweendifferent factorsandtheir impacts within the identified common factors. The comparisons of the results provideopportunities to derive implications on similarities and differences in the opinions betweendifferent professional groups and user structures. The average age of the managers in thesample in the energy sector was 39.4 years. The education structure is rather normallydistributed;theaverageamountofcompletededucationpermanageris16.0years.
Corresponding
author:
Drago
Papler,
MSc,
Tel.:
+386
4283
232,
Fax:
+386
4283
512,
address:[email protected]:UniversityofPrimorska,FacultyofManagement,Cankarjeva5,SI6104Koper
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