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1Automa ticGe nerati onCont rolofIslandedPowerDistr ibutio nSystemwithDispersedPowerSourcesQUDAIH,YaserandHIYAMA,TakashiDepartmentofComputerScienceandElectricalEngineeringofKumamotoUniversity39-1Kurokami2-chomeKumamoto860-8555,JapanAbstractIntendedislandingoftheelectricalpowerdistributionsystemrequireshightechniquesandbigcautiontocontrolthefrequencyoftheentiresyste m,wheretheupperelectri calsyst emthatisresponsi bleaboutholdin gthefrequency ,isabsen t.Inthepast, loadsheddingtechniquehasbeenutilizedtoimplementthisgoal.Thispapercomesafterapreviousjobofloadfollowingoperat ioncontro l,doneandcomplete dbeforeisolatin gthesystem.ThewellknownAutoma ticGenera tionContro l(AGC)ispresentedinthispapertomaintainthefrequencyoftheislandedsystem.Althoughenvironmentaldependentrenewableenergysour ces,suchasgrid-c onnec tedphotovolt aicsystems ,arepresentandspreadwithinthetarge tsystem,thefrequ encycanbecontrolledbythe tec hni que us edinthi spaper. Ene rgy Capaci tor System (ECS), which has fas tcha rgi nganddis cha rgi ngcapabilitiesplaysthemainroleofAGCactively,comparedwithagovernorsystem.Keywords:Isolatedpower distributionSystem,frequencycontr ol,automaticgenerationcontrol,energycapacitordevice,loadsshedding. 1INTRODUCTIONIt is obvi ous toevery rese arc he r inthefi el dof el ec tr ical energ ythatthehugeinterest andatten tiontothedistribut edge ne rations andthei r impact ontheel ec tr ical syst em, isgoingrapidlyduetothereasonofenvironmentalconcerns.However,thispaperisdealingwiththeperformanceoftheis ol at edpower di st ri bu ti onsystems, in th e pr esence of di sper se dpowe r sour ces. Mos t of thest udie scon si dered distr ibuti onsyst emasaninterc onnec tedsystem,whichhasbeen discu ssed inaprevio usjob[1].Fewothersdiscusse daboutisolatedorstandalonepow erdistributionsystems[2].In fac t, in te rest in is olate d power sy ste msis ra pi dl y incr ea si ng. Instandalone systemsthefr equencyisquite aff ect edbytheunbala nce dsituationbetween the loa dandthe gen era tion ,for exa mpl ewhenthe demandexc eedsthe generation,thefrequencytendstobedecreasedordroppedandconversely,whenthegenerationexceedsthedemandthefre que ncy ofthe sys temwi llbeinc rea sed .Someada pti veloadshed dingalgori thmshavebeen usedandperformed,inor der tosolvethepr obl emof fr eque ncydevi at ion intheisolatedpowersystems[3],[4].Howeverthesesmethodsarement ione dhe re just tobe compa re dwit hth e pr opos edme thod ology. Inthi spaperthe loa dshe ddi ngprocesshas bee nche cke dsimplybyadding and isolat ingsomeofthe fix edloa dcon nec tedtothe sys temwit hou tadopti nganyspec iala lgorith m.�� Thispa per is st udy ing theperformanc eof acompletelyis ol at edsy stem, wh ich cont ai ns phot ovol taicunits as arenewableenergyordispersedpowersource.Theun ba la nc edge ne ra tion-deman dsi tuat ionca us ed by the phot ovol taic unit s, whichis envi ron ment al lydependent powersources,inadditiontothevariableload,resultsinadisturbancein th efrequen cyof th esyste m.EnergyCapacitorSystem(ECS)isutilizedtosolvethisproblemviath e un iq ue chara cte risti cs of th is de vi ce, su ch asfast cha rgi ngand dis cha rgi ngcapabi lit ies [5]. Acoordin ati onsch eme bet wee ntheECSandadie sel uni tisusedtokeepthe cha rgi nganddischarg ingleve loftheECSinacer tain desi redleve l [6]. Furt he rmore theECScont rol acti oniscom paredwi ththeacti onof gov er nor, mo deledfor thispurposei.e.tocompareandchecktheefficiencyoftheECSinpe rformin gtha tacti on.2TARGETSYSTEMThe tar get sys teminthis paperisaring /loopdis tri but ion6.6k v,60Hzsyste m,whichisrec onf iguredint odiff ere ntradial sys temsand sameapp lic ati ons we reapplie donall reconfiguredcasesthatisappliedinsomespecialareas,likeair port sand oth erisolat edisl and s.The Ene rgyCap aci torSyst em(ECS), which hasfast char gi nganddi scha rgingca pa bi li ti es pl ay s th e ma inrole of AGCac ti vel y, by pro vi di ngthe ge ne rati onanddema ndbala nc econdit ion. FirstpageTemplateSecretariatusesonly.Donottypeinthisbox. The International Conference on Electrical Engineering 2008 No. O-018

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1�

� Automatic�Generation�Control�of�Islanded�Power�Distribution�System�

with�Dispersed�Power�Sources�

�QUDAIH,�Yaser�and�HIYAMA,�Takashi�

Department�of�Computer�Science�and�Electrical�Engineering�of�Kumamoto�University�

39-1�Kurokami�2-chome�

Kumamoto�860-8555,�Japan�

�Abstract�

�Intended�islanding�of�the�electrical�power�distribution�system�requires�high�techniques�and�big�caution�to�control�the�frequency�

of�the�entire�system,�where�the�upper�electrical�system�that�is�responsible�about�holding�the�frequency,�is�absent.�In�the�past,�load�shedding�technique�has�been�utilized�to�implement�this�goal.�This�paper�comes�after�a�previous�job�of�load�following�

operation�control,�done�and�completed�before�isolating�the�system.�The�well�known�Automatic�Generation�Control�(AGC)�is�

presented�in�this�paper�to�maintain�the�frequency�of�the�islanded�system.�Although�environmental�dependent�renewable�energy�

sources,�such�as�grid-connected�photovoltaic�systems,�are�present�and�spread�within�the�target�system,�the�frequency�can�be�controlled� by� the� technique� used� in� this� paper.� Energy� Capacitor� System� (ECS),� which� has� fast� charging�and� discharging�

capabilities�plays�the�main�role�of�AGC�actively,�compared�with�a�governor�system.�

�Keywords:�Isolated�power�distribution�System,�frequency�control,� �

automatic�generation�control,�energy�capacitor�device,�loads�shedding.�

�1�INTRODUCTION�

�It� is� obvious� to� every� researcher� in� the� field� of� electrical�

energy�that�the�huge�interest�and�attention�to�the�distributed�

generations� and� their� impact� on� the� electrical� system,� is�

going�rapidly�due�to�the�reason�of�environmental�concerns.�

However,�this�paper�is�dealing�with�the�performance�of�the�

isolated� power� distribution� systems,� in� the� presence� of�dispersed� power� sources.� Most� of� the� studies� considered�

distribution�system�as�an� interconnected�system,�which�has�

been�discussed� in�a�previous� job�[1].� Few�others�discussed�

about�isolated�or�stand�alone�power�distribution�systems�[2].� ��

In� fact,� interest� in� isolated� power� systems� is� rapidly�

increasing.� In� standalone� systems� the� frequency� is� quite�affected�by�the� unbalanced� situation� between� the� load� and�the� generation,� for� example�when� the� demand� exceeds� the�

generation,�the�frequency�tends�to�be�decreased�or�dropped�

and�conversely,�when�the�generation�exceeds�the�demand�the�

frequency� of� the� system� will� be� increased.� Some� adaptive�

load�shedding�algorithms�have�been�used�and�performed,�in�

order� to� solve� the� problem� of� frequency� deviation� in� the�

isolated�power�systems�[3],�[4].�However�theses�methods�are�

mentioned� here� just� to� be� compared� with� the� proposed�

methodology.� In� this� paper� the� load� shedding� process� has�

been� checked� simply� by� adding� and� isolating� some�of� the�

fixed� load� connected� to� the� system� without� adopting� any�

special�algorithm.� �

This� paper� is� studying� the� performance� of� a� completely�isolated� system,� which� contains� photovoltaic� units� as� a�

renewable� energy� or� dispersed� power� source.� The�

unbalanced� generation-demand� situation� caused� by� the�

photovoltaic� units,� which� is� environmentally� dependent�

power�sources,�in�addition�to�the�variable�load,�results�in�a�

disturbance� in� the� frequency� of� the� system.� Energy�Capacitor�System�(ECS)�is�utilized�to�solve�this�problem�via�

the� unique� characteristics� of� this� device,� such� as� fast�

charging� and� discharging� capabilities� [5].� A� coordination�

scheme�between�the�ECS�and�a�diesel�unit� is�used�to�keep�the� charging�and�discharging�level�of�the�ECS� in�a� certain�

desired� level� [6].� Furthermore� the� ECS� control� action� is�

compared� with� the� action� of� governor,� modeled� for� this�purpose�i.e.�to�compare�and�check�the�efficiency�of�the�ECS�in�performing�that�action.� �

2�TARGET�SYSTEM�

The� target� system� in� this� paper� is� a� ring/loop� distribution�

6.6kv,� 60�Hz� system,�which� is� reconfigured� into� different�

radial� systems� and� same� applications� were� applied� on� all�

reconfigured�cases�that�is�applied�in�some�special�areas,�like�

airports� and� other� isolated� islands.� The� Energy� Capacitor�

System� (ECS),� which� has� fast� charging� and� discharging�

capabilities� plays� the� main� role� of� AGC� actively,� by�

providing� the� generation� and� demand� balance� condition.�

First�page�Template�

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No. O-018

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� 2�

Coordination� between� one� of� the� controllable� generation�

units,�which�is�diesel�generator�in�this�case,�and�between�the�ECS,�is�implemented�to�keep�the�ECS�system�in�the�desired�

charging� and� discharging� level.� Multi-Agent� System� and�

computer�networks� are� also�utilized�in� case� the� diesel� unit�

and� the� ECS� are� not�in� the� same�location,� to�complete�the�coordination� process.� In� order� to� take� into� account� many�

other� measures�such�as�economical�aspects� and� flexibility,�

several�locations�and� different�sizes�of�the�ECS� have�been�tested.� The� single� line� diagram� of� the� target� system� is�

illustrated�in�Figure�1.�

Photovoltaic� system� is� connected� at� every� node� of� the�described� system� [7],� in� the� form� of� grid� connected�

photovoltaic� system,� of� different� variable� outputs,� to�

represent�a�real�situation.�Figure�2�shows�the�total�output�of�

the�photovoltaic�generation�units�that�have�been�considered�only�at�the�AC�side�for�the�sake�of�simplicity.�The�variation�

of� power� output� from� the� photo� voltaic� units� is� the� main�fluctuation� caused� in� the� entire� system.� Another� changes�

caused� by� a� step� load� variation� is� also� added� to� cause� a�

sudden�increase� in�the�demand,�in�such�a�way� to�show� the�

response� of� the� ECS� and� the� control� efficiency,� Figure� 3�

shows�the�step�load�variation�added�to�the�system.�

�Figure�1.�Single�line�diagram�of�the�target�system�

0 20 40 60 80 100 120 140 160 1800

1000

2000

3000

       P       V       (       k       W

       )

�Figure�2.�Total�output�of�the�photovoltaic�generation�units�

0 20 40 60 80 100 120 140 160 180

0

500

1000

       P       l     o     a       d

       (       k       W

       )

�Figure�3.�Step�variable�load�

3�METHODOLOGIES�

Load� frequency� control� (LFC)� or� automatic� generation�

control� (AGC),� which� is� commonly� used� to� control� the�frequency�of�big�systems,�by�regulating�the�power�output�of�

electric�generators� within� a� prescribed�area,� in� response�to�

changes� in� system� frequency,� is� proposed� in� this� paper.�

Multi-Agent�based�AGC�has�been�also�tested�when�the�ECS�and� the� diesel� unit� are� not� in� the� same� location,� by�using�

computer�networks,�to�send�and�receive�information�between�

these�two�controllable�units.�In�this�paper�the�target�system�

and�the�control�strategy�have�been�modeled�and�simulated�in�Matlab/Simulink�environment,�where�the�application�on�the�

frequency�control�has�been�made�according�to�the�following�

scenarios:� � ��

3.1�Governing�system�

Governor�of� ideal� characteristics�has� been�modeled�for� the�purpose�of� frequency�control,� to�compare� its�function�with�

the�function�of�the�ECS,�which�has�the�main�mission�in�the�

proposed�methodology.�Figure�4�shows�the�speed�deviation�

when�the�system�is�supported�by�the�governor�attached�to�the�diesel� unit� which� is� deriving� a� synchronous� generator,� as�

shown� in� Figure� 5.�The� graph� shows� the� speed� deviation�which�corresponds� to� the� frequency�of� the� system.� In� this�

case�the�ECS�is�out�of�service.�

0 20 40 60 80 100 120 140 160 180-0.1

-0.05

0

0.05

0.1

       d     w

�       (     r     a       d       /     s       )

time(s) �Figure�4.�Speed�deviation�controlled�by�governor�

Figure�5.�Matlab�representation�of�the�Synchronous�generator�and�the�governing�system�(GOV)�

3.2�ECS�system�

Energy� Capacitor� System� in� the� form� of� double� layer�capacitor� is�mostly� located� at�the� same�position�where� the�

controllable� diesel� generating� unit� is� placed.� The� balance�

between�the�generation�and�demand�is�provided�due�to�the�

fast� charging� and� discharging� characteristics� of� the� ECS.�The�coordination�controller� is�shown�in� Figure�6,�where�PI�

controller�is�used�for�the�purpose�of�supporting�the�ECS�that�

has�a�small�size,�and�in�order�to�keep�the�ECS�in�a�specific�

operating�range.�Figure�7�shows�the�simulation�result�when�the� system� is� supported� by� the� ECS� in� the� same� location�

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� 3�

with�the�diesel�unit.�In�the�mentioned�graph�at�point�(a)�the�

AGC�control�on�the�ECS�is�activated.�If�the�ECS�and�the�diesel�unit�are�not�in�the�same�location,�

the� coordination� process� cannot� be� hold� unless� a�

communication� process� is� provided� to� coordinate� between�

the�two�units.�Multi-Agent�system�scheme�has�been�utilized�here�as�explained�below.� � � �

�Figure�6.�Coordination�controller�between�the�ECS�and�the�

diesel�unit,�� Where�Et:�is�the�target�stored�energy�of�the�ECS�

� EECS:�is�the�stored�energy,� �

PECS:�is�the�ECS�power�output,� �

and�Pm:�is�the�control�signal�to�the�diesel�unit��

0 20 40 60 80 100 120 140 160 180-0.1

0

0.1

          d

       w

�          (       r       a

          d

          /       s

          )

time(s)a

�Figure�7.�Speed�deviation�controlled�by�the�ECS-Diesel�

coordination�controller�

3.1�Multi-Agent�based�AGC�

It�has�been�noticed�that�the�ECS�can�be�easily�placed�in�the�

same�location�of�the�completely�isolated�power�distribution�system,�but�in�some�cases�such�as�if�the�system�was�already�

connected�to�upper�system�as�in�[1],�so�the�ECS�cannot�be�

moved� to� another� position.� Multi-Agent� system� is� a�

computer� network� consists� of� several� personal� computers�

called� agents� are� responsible� about� sending� and� receiving�

data�among�each�others,�to�perform�the�control�strategy�and�

provide�the�coordination�scheme�between�some�elements�of�

the� system,� namely� the� ECS� and� the� Diesel� Generator,�

regardless� to� the� communication� time� delay� which� is�

neglected�in�this�case.�Those�agents�are�mainly�divided�into�

three�parts:�

� A)�Monitoring�agent�has�the�mission�of�measuring�the�data�required�from�one�part�of�the�system�and�supply�it�through�

the�computer�network�to�the�supervisor�agent.�

� B)� Supervisor� agent� plays� the� mission� of� coordination�

among�the�controllable�devices�in�the�system,�it�is�obviously�

provided�with�the�suitable�algorithm�and�control�strategy�in�

order�to�send�the�required�data�to�the�control�agent.�

C)�Control� agent� has� the� mission� of� applying� the� control�signal� via� sending� the� control� signal� to� the� desired�equipment,� which� is� the� diesel� generator� in� this� case� to� �

make� it�acts�according� to�the� control�value,� to�support� the�

Energy�Capacitor�System,�which�is�small�in�size�but�fast�in�

charging�and�discharging.�Analogue�to�digital�convertor�A/D�and� digital� to� analogue� converter� D/A,� including� digital�

signal� processing� board� DSP,� are� used� to� perform� the�

Multi-Agent�based�control�action.�Figure�8�shows�the�setting�of�the�Multi-Agent�in�the�system.�

�Figure�8.�Multi-agent�setting�

The�configuration�of�the�Multi-Agent�system�is�shown�in�Figure�9.�

�Figure�9.�Multi-Agent�system�general�configuration�

Where�DG:�is�the�diesel�generator�

4�DETAILED�SIMULATION�RESULT�

More� results� obtained� by� digital� simulation� and� following�different� scenarios,� in� addition� to� the� numerical� results�

obtained� by� calculating� the� maximum,� minimum� and� the�

mean�speed�deviation,�as�shown�in�Table�1.�The�index�used�

to�evaluate�the�simulation�result�is�the�mean�speed�deviation,�

calculated� by�Matlab� and� using� equation� 1.� The� efficient�

usage� of� the� ECS� system� to� implement� the� AGC� for� a�

constant�frequency�is�shown�clearly.�Figures�10,�11�and�12,�

illustrate� the� simulation� results� for� defferent� cases,� where�

Pecs�is�the�output�power�of�the�ECS,�Eecs�is�the�stored�energy�

of� the� ECS,� Pdg� is� the� diesel� unit� power,� PV� is� the�photovoltaic�units�total�output�Pload�is�the�step�variable�load�

and�dω�is�the�speed�deviation.� �

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� 4�

The�arrow�at�point�(a)�in�Figure�11�indicates�the�time�when�

the�AGC�control�on�the�ECS�is�activated.��

� � � � � � � � � � � � �

(1)� � � � � � � � � � �

�Where�dω�is�the�speed�deviation�taken�at�the�diesel�generator�

side�and�N� is�the�number�of�the�taken�data.�As�a� result� the�

frequency�of�the�system�is�supposed�to�be�determined�by�the�frequency�of�the�diesel�generator�which�is�represented�by�the�

speed�deviation�in�this�paper.�

0 20 40 60 80 100 120 140 160 180-500

0

500

      P    e    c    s      (      k      W

      )

0 20 40 60 80 100 120 140 160 1800

1

2

3

      E    e    c    s      (      k      W

      h      )

0 20 40 60 80 100 120 140 160 180

2000

4000

      P      d    g      (      k      W

      )

0 20 40 60 80 100 120 140 160 1800

1000

2000

3000

      P      V

      (      k      W

      )

0 20 40 60 80 100 120 140 160 180

0

500

1000

      P      l    o    a      d      (      k      W

      )

0 20 40 60 80 100 120 140 160 180-1

0

1

2

      d    w�      (    r

    a      d      /    s      )

time(s)

�Figure�10.�Simulation�result�in�case�of�a�step�variable�load�

and�without�any�control�action�from�the�ECS�

0 20 40 60 80 100 120 140 160 180-1000

0

1000

      P    e    c    s      (      k      W

      )

0 20 40 60 80 100 120 140 160 1800

1

2

3

      E    e    c    s      (      k      W

      h      )

0 20 40 60 80 100 120 140 160 180

2000

4000

      P      d    g      (      k      W

      )

0 20 40 60 80 100 120 140 160 1800

1000

2000

3000

      P      V      (      k      W

      )

0 20 40 60 80 100 120 140 160 180

0

500

1000

      P      l    o    a      d      (      k      W

      )

0 20 40 60 80 100 120 140 160 180-0.1

0

0.1

      d    w�      (    r

    a      d      /    s      )

time(s)a �Figure�11.�Simulation�result�using�the�ECS-Diesel�

coordination�controller� �

0 20 40 60 80 100 120 140 160 180

-500

0

500

      P    e    c    s      (      k      W

      )

0 20 40 60 80 100 120 140 160 1800

1

2

3

      E    e

    c    s      (      k      W

      h      )

0 20 40 60 80 100 120 140 160 180

2000

4000

      P      d    g      (      k      W

      )

0 20 40 60 80 100 120 140 160 1800

1000

2000

3000

      P      V      (      k      W

      )

0 20 40 60 80 100 120 140 160 180

0

500

1000

      P      l    o    a      d      (      k      W

      )

0 20 40 60 80 100 120 140 160 180-0.1

0

0.1

      d    w�      (    r

    a      d      /    s      )

time(s)

� �Figure�12.�Simulation�result�where�only�Governor�is�

activated�for�AGC��

Table�1.�Speed�deviation�under�different�control�action� �

��

4�CONCLUSION�

The�proposed�methodology�of�automatic�generation�control,�by� utilizing� the� Energy� Capacitor� System,� supported� by�a�

diesel� unit,� is� efficient� to� control� the� frequency� of� the�

isolated�system.�Either�the�two�controllable�units�are�in�the�same� location� or� not� the� proposed� methodology� still� the�same�with�the�help�of�Multi-Agent�system.�

REFERENCES�

[1]�Yaser�Qudaih�and�Takashi�Hiyama,�“Reconfiguration�of�

Power� Distribution� System� Using� Multi� Agent� and�

Hierarchical� Based� Load� Following� Operation� with�

Energy� Capacitor� System,”� Proceeding� of� The� 8th�

international�power�engineering�conference�(IPEC2007),�

Singapore,�Dec.�3-7,�2007,�pp.�263-267.�

Second�page�and�after�Template�

Secretariat�uses�only.�Do�not�type�in�this�box. �

July 6-10, 2008, OKINAWA, JAPAN 

8/14/2019 Yaser_Qudaih2

http://slidepdf.com/reader/full/yaserqudaih2 5/5

� 5�

[2]� T.� Kato,� H� Kanamori,� Y.� Suzuoki� and� T.� Funbashi,� � � �

“Multi-Agent� Based� Control� and� Protection� of� Power�Distribution�System�-Protection�Scheme�with�Simplified�

Information� Utilization-,”� Proceeding� of� the� 13th�

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Application� to� Power� Systems,� Nov.� 6-10,� 2005,� pp.�49-54.� �

[3]�J.G.�Thompson�and�B.�Fox,�“Adaptive�load�shedding�for�

isolated�power�systems,”�Generation,�Transmission�and�distribution,� IEE,� Volume� 141,� Issue� 5,� Sep� 1994�

pp.491�–�496.�

[4]�Sodzawiczny,�G.�and�Sowa,�“Multicriterial�adaptive�load�

shedding� algorithm,”� Proceeding� of� International�Conference� on� Electric� Power� Engineering,� Budapest,�

Hungary,�1999,�PP.192.�

[5]� M.� Okamoto,� “A� basic� Study� on� Power� Storage�

Capacitor�Systems”,� Trans.� IEE�of� Japan,�Vol.�115-B,�No.5,�1995.�

[6]�Yaser�Qudaih�and�Takashi�Hiyama,�“Frequency�Control�for� Islanded� Power� Distribution� Systems,”� Proceeding�

of�the�1st�International�Student�Conference�on�Advanced�

Science� and� Technology� (ICAST),� Kumamoto,� Japan,�

March�13-14,�2008,�pp.165-166.�

[7]� Jukka� V.� Paatero� and� Peter� D.� Lund,� “Effects� of�

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pp.�216-234,�2007.�

Biographies� �

Yaser�Qudaih�He�received�his�BSc.�from�

University� of� Engineering� and�Technology� (UET),�Lahore,�Pakistan,�as�

an� electrical� engineer� in� the� year� 1996.�He� received� his� M.Eng.� degree� in�

electrical� engineering� from� Kumamoto�

University,�Japan�in�2008.�Currently�he�is�

a�Ph.D.�student�in�Kumamoto�University,�Japan.�

Hiyama�Takashi�He�received� his� B.�E.,�

M.� S.� and� Ph.� D.� degree� in� electrical�

engineering� from� Kyoto� University� in�

1969,�1971�and�1980,�respectively.�Since�1989,� he� has� been� a� professor� at� the�

Department� of� Computer� Science� and�Electrical� Engineering,� Kumamoto�

University,� Japan.� Currently� he� is� the� Dean� of� Graduate�School� of�Science�and�Technology�of� the�same�university.�

He�is�a�senior�member�of�IEEE,�a�member�of�IEE�of�Japan,�

and�Japan�Solar�Energy�Society.�

Second�page�and�after�Template�

Secretariat�uses�only.�Do�not�type�in�this�box. �

The International Conference on Electrical Engineering 2008