jet - volume 3 - issue 3 - august 2010 - za internet

8/3/2019 Jet - Volume 3 - Issue 3 - August 2010 - Za Internet

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JET

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,


Prof.dr.AntonJEZERNIK,

Fakultetazaindustrijskiineniring,Slovenija/Facultyofindustrialengineering,SloveniaProf.dr.RomanKLASINC,

TechnischeUniversittGraz,Avstrija/GrazUniversityOfTechnology,Austriar.IvanAleksanderKODELI

InstitutJoefStefan,Slovenija/JoefStefanInstitute,SloveniaProf.dr.JurijKROPE,


Prof.dr.AlfredLEIPERTZ,

UniversittErlangen,Nemija/UniversityofErlangen,Germany

Prof.dr.BranimirMATIJAEVI,SveuiliteuZagrebu,Hrvaka/UniversityofZagreb,CroatiaProf.dr.MatejMENCINGER,


Prof.dr.GregNATERER,

UniversityofOntario,Kanada/UniversityofOntario,Canada

Prof.dr.EnrikoNOBILE,

UniversitdegliStudidiTrieste,Italia/UniversityofTrieste,ItalyProf.dr.IztokPOTR,


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,


Prof.dr.JoeVORI,UniverzavMariboru,Slovenija/UniversityofMaribor,Slovenia

Doc.Dr.PeterVIRTI,



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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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JanezUsenik JETVol.3(2010) Issue3

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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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



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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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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22 JET


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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JET 2

JETVolume3(2010),p.p.2740

Issue3,August2010


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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2 JET

FrancMihaliandAlenkaHren JETVol.3(2010) Issue3

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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JET 2

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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(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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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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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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JET


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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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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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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FrancMihaliandAlenkaHren JETVol.3(2010)

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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[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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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,

Email

address:

[email protected]


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2 JET

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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CleancoaltechnologiesatCoalmineVelenje

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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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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Cleancoaltechnologies atCoalmineVelenje

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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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

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[13]S.Zavek,J.ula,2009.Razplinjevanje lignitavPremogovnikuVelenje,PP,september2009,Velenje,Slovenija.


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Issue3,August2010


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,

Email

address:[email protected]:UniversityofPrimorska,FacultyofManagement,Cankarjeva5,SI6104Koper

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