Extreme production conditions of photovoltaic power plant operated in distribution grid

POWER ENGINEERING AND ELECTRICAL ENGINEERING VOLUME: 12 |NUMBER: 3 |2014 |SEPTEMBER Ex eme P oduc ion Condi ions o Pho o ol aic Powe Plan Ope a ed in Dis ibu ion G id Ma in SMOCEK, Zdenek HRADILEK Depa men o Elec ical Powe Enginee ing, Facul y o Elec ical Enginee ing and Compu e Science, VSB-Technical Uni e si y o Os a a, 17.lis opadu 15/2172, 708 33 Os a a-Po uba, Czech Republic ma in.smo[email p o ec ed], [email p o ec ed] Abs ac . Pho o ol aic powe plan s a e sou ces o elec ical ene gy ha a e e y dependen on wea he condi ions. This pape in e es s in desc ip ion o s ochas ic p oduc ion o powe in pho o ol aic powe plan s and subsequen ly i s impac on he dis ibu ion powe g id. S ochas ic p oduc ion o powe om hese sou ces is conside able and ha dly p edic able. The aim o his su ey is o assess he in luence o pho o ol aic powe plan s ope a ion on he daily load diag am wi h ega d o ou pu change di e ence o ac i e powe a he ele an subs a ion. E alua ion is based on eal- ime synch onous da a measu ing bo h on-si e pho o- ol aic powe plan ope a ion and on-si e elec ic powe line ou pu om he subs a ion. This measu emen is used o sugges ion o a gene al calcula ion me hodol- ogy o he assessmen o he di e ence o ac i e powe a a pa icula node o he g id unde a ious powe changes om he pho o ol aic powe plan . S a is i- cal me hods ha e been employed o p ocess a me hodol- ogy in o de es ablish ex eme condi ions o p oduc ion powe o pho o ol aic powe plan . Keywo ds Calcula ion me hodology, pho o ol aic powe plan , eal measu emen , s a is ical me hods, s ochas ic e ec . 1. In oduc ion Dependence ope a ion o bo h pho o ol aic powe and wind powe plan is conside able on me eo ological con- di ions [3], [4]. This pape con ains a desc ip ion o he assessmen ocused on he issues o calcula ion me hod- ology. Mos s udies deal wi h he p edic ion o powe as [6], bu he pu pose o his me hodology is o de- e mine di e ences in ac i e powe induced by ope a- ion o pho o ol aic powe plan s (PVP). The su ey is based on ac ual long- e m moni o ing o a speci ic powe plan . The da a a ailable has been ob ained by measu emen a he PVP ope a ion si e as well as he poin o elec ic powe ou pu om subs a ion plan , whe e he PVP is connec ed. Bo h measu emen s we e conduc ed on synch onised basis. The e alua ion o PVP p oduc ion is conduc ed by means o se e al indi idual asks ha can be spli in o wo s ages. The i s s age de e mines me hodology o se -up o ex eme h esholds o p oduc ion gene - a ed by he PVP and he second s age conce ns ana- lysis o he impac o hese ex eme h eshold alues on he magni ude o ac i e powe lows a he place o measu emen wi hin subs a ion plan . The eached esul s om he analysis o PVP a e use o es ablish a me hodical calcula ion model o conside he impac o s ochas ic p oduc ion o ac i e powe in he PVP on he dis ibu ion g id a a ious nominal alues o peak powe wi hin a ious ime in e als h oughou he yea . The ope a o s o such g ids conside he s ochas ic na u e o he powe supplied undesi able. Such con- di ions esul in highe demand o ese e capaci y in e ms o Ancilla y Se ices o ensu e he equi ed bal- ance be ween immedia e p oduc ion and consump ion o elec ic powe . Po en ial changes o powe low ep- esen jus ano he nega i e consequence. Tha a ec s he p ope unc ioning o means o g id p o ec ion. The e a e also p oblems wi h keeping he equi ed s a- ble ope a ing g id pa ame e s. This calcula ion model is es ablished wi h espec o he po en ial impac on p ese ing he magni ude o capaci y Ancilla y Se - ices [5]. 2. A ea o a Measu ed G id The da a was ob ained by measu emen bo h a PVP ope a ion and on he ele an powe line ou pu o he subs a ion plan , whe e his PVP is connec ed [1]. c 2014 ADVANCES IN ELECTRICAL AND ELECTRONIC ENGINEERING 185 POWER ENGINEERING AND ELECTRICAL ENGINEERING VOLUME: 12 |NUMBER: 3 |2014 |SEPTEMBER 2.1. Da abase o Measu ed Da a 1) Pho o ol aic Powe Plan The peak ou pu o his PVP is 1.1 MWp. The mea- su emen was conduc ed on he low ol age side on a con inuous basis o one yea . Accu a ely ha was om 30.6.2010 ill 29.6.2011. The da a was eco ded wi h ime s ep se a one-minu e inc emen s. 2) Ou pu Subs a ion Plan The measu emen a he powe line ou pu was con- duc ed on he high ol age end and an wi hin a ious ime pe iods om 26.7.2010 ill 23.6.2011. Same as o PVP, he measu emen was pe o med a one-minu e inc emen s. The measu emen p ocess p oduced many ope a ing alues and pa ame e s. This su ey deals wi h he analysis o he ac i e powe Po e ime pa h . Pe cen age e alua ion and mu ual compa ison o da a measu ed on PVP and a he subs a ion poin ha e been illus a ed in Fig. 1. Columns in cha s ep- esen indi idual mon hs. The las column shows an a e age o all mon hs moni o ed. In o al, he e a e 98 % o he da a om PVE and 64 % o he da a om he subs a ion, whe e: •p - pe cen a ailabilily, •x-axis - indi idual mon hs, •su - a e age sum o indi idual mon hs. Fig. 1: Pe cen age compa ison o da a measu ed [1]. 2.2. Ne wo k Topology The ne wo k opology has a loop sys em, ye i is ope- a ed in he adial sys em. When his measu emen was conduc ed, he PVP was he only elec ic powe sou ce wi h signi ican ou pu on a gi en powe line, whe e: •PVP - pho o ol aic powe plan , •SS - sec ion swi ch (disconnec ed), •110/22 kV - subs a ion plan 110/22 kV. Fig. 2: Measu e g id opology [1]. The i s measu emen was pe o med a he ou going eede om he subs a ion 110/22 kV using he side o lowe ol age le el o 22 kV. The second measu emen was done a he connec ion poin o he pho o ol aic plan o he g id a he ol age le el o 0.4 kV. Bo h measu emen s we e conduc ed in a synch onous man- ne . Poin s o measu emen a e lagged ed in Fig. 2. 3. Ancilla y Se ices The T ansmission G id Code (GC), pa II, as amended by e ision 14 duly app o ed by he Ene gy Regula- o y O ice on 1.1.2014 in Czech Republic, de ines he ma e s ele an o he u ilisa ion o GC wi h espec o Ancilla y Se ices. The documen con ains me ho- dology o de e mina ion o summa y con ol backups o SS o he powe g id in Czech Republic. One o he p e equisi es o de e mina ion o summa y con- ol backups o SS is he so-called de ia ion ODOZE( ). This is a pa ame e o es ablish he inc emen o bal- ancing de ia ion caused by p oduc ion om newly in- s alled enewable esou ces o elec ic powe . As s a ed he e (1), his inc emen is de ined by he sum o he inc ease gene a ed by ope a ion o wind ODV E( )and pho o ol aic ODF V E( )powe plan s. The de ia ion ODOZE( )is hen used o de e mine olumes o SS e- qui ed o he subsequen pe iod, based on exis ing in- o ma ion om p epa a ions o he ope a ion, e.g.: ODOZE( )=ODV E( )+ODF V E( ).(1) This s a emen , desc ibed equa ion (1), implies ha he e ec o ins alled capaci y o pho o ol aic powe plan s has a ce ain impac on he calcula ion o SS. Aim o his su ey is o assess i and how much he PVP p oduc ion has in luence o o al calcula ion o SS wi h espec o indi idual mon hs. The simila app oach o e alua ion is also desc ibed in [7]. c 2014 ADVANCES IN ELECTRICAL AND ELECTRONIC ENGINEERING 186 POWER ENGINEERING AND ELECTRICAL ENGINEERING VOLUME: 12 |NUMBER: 3 |2014 |SEPTEMBER 4. Ex eme Condi ions The consis ency and comp ehensibili y o his a icle a e suppo ed by he esul s om own su ey o de- ine a me hodology o de e mina ion o ex eme p o- duc ion condi ions o pho o ol aic powe plan . These ma e s we e p esen ed in de ail a he con e ence [2]. Essen ial esul s will be desc ibed. 4.1. Pho o ol aic Powe Plan Figu e 3 shows h ee cu es as a sample o analyzed da a in his pape . Indi idual cu es co espond as ollows: •p oducend powe om PVP (g een), •powe lowing h ough he subs a ion (blue), •loads (black). Fig. 3: Sample o examined da a. The powe di e ence o PVP has a nega i e impac on immedia e powe balance be ween p oduc ion and con- sump ion wi hin he powe g id. Fo his eason, he analysis o ex eme h esholds is necessa y. Based on ac o s desc ibed in [2], one-minu e ou pu se ies was con e ed in o i e-minu e inc emen s. De o ma ion o he da a in o ma ion wi h espec o u he p ocess- ing and e alua ion a ge is negligible. As an example, u he s eps desc ibed in his a icle analyse da a in Ap il 2011. Figu e 4 shows ex eme a eas o PVP p oduc ion ( he g een cu e om Fig. 3. The h esholds o hese ex eme condi ions a e de ined by wo eg ession poly- nomial Eq. (2) and Eq. (3), which o m he op and bo om en elope cu es o s ochas ic changes in he p oduced powe . The equa ions a e as ollows: PF V Emax =−5700,51 + 63525,7·T ime −246642 ·T ime2+ 400745 ·T ime3(2) −279206 ·T ime4+ 66861,7·T ime5, PF V Emin = 4554,05 −68932,4·T ime +414328 ·T ime2−1,25591 ·106·T ime3(3) +2,0145 ·106·T ime4−1,62904 ·106·T ime5 +523013 ·T ime6. De e mina ion o hese ex eme condi ions was con- duc ed based on s a is ical me hods ha u ilize he el- e an equency ca ego ies using he so-called S u ges ule. This is a ule o op imal de e mina ion o e- quency ca ego ies. Nex s ep is o e alua e daily load Fig. 4: Ex eme condi ions o PVP. diag am. Co ela ion ields o daily load diag am ( he black cu e om Fig. 3) can be subjec o eg ession analysis applied o enable de e mina ion o di e en ial powe h esholds o loads. I is desc ibed in Fig. 5. Ex- eme h eshold condi ions, Eq. (4) and Eq. (5), ha e been de e mined using 95 % p edic ion le els. Fo mo e in o ma ion on his issue e e o [2]. The equa ions a e as ollows: Fig. 5: Ex eme condi ions o daily diag am. P e ious analyses ha e p oduced he ex eme di e - ence o ou pu gene a ed by PVP and de e mina ion o h esholds o daily load diag am. Ex eme condi ions ha migh occu a he subs a ion plan ou le co e- spond wi h he sum o ex eme condi ions bo h PVP c 2014 ADVANCES IN ELECTRICAL AND ELECTRONIC ENGINEERING 187 POWER ENGINEERING AND ELECTRICAL ENGINEERING VOLUME: 12 |NUMBER: 3 |2014 |SEPTEMBER POBDmax(M W ) = 2,13445 + 0,000174187 ·T ime −4,6908 ·10−8·T ime2+ 4,32657 ·10−12 ·T ime3 −1,78877 ·10−16 ·T ime4+ 3,85326 ·10−21 ·T ime5−4,49778 ·10−26 ·T ime6(4) +2,69318 ·10−31 ·T ime7−6,46948 ·10−37 ·T ime8, POBDmin(M W )=1,45615 + 0.000176551 ·T ime −4,72509 ·10−8·T ime2+ 4,35116 ·10−12 ·T ime3 −1,79852 ·10−16 ·T ime4+ 3,87564 ·10−21 ·T ime5−4,52732 ·10−26 ·T ime6(5) +2,71398 ·10−31 ·T ime7−6,52996 ·10−37 ·T ime8. and he daily load diag am. They ha e been de ined as ollows: 1) Maximum Ex eme Condi ions: ma ching he maximum ex eme condi ion ha may occu . I is equal o he di e ence be ween he max- imum ex eme o DLD (uppe p edic ion le el 95 %) and he minimum ex eme o PVP: PROZ(max)=POBD(max)−PF V E(min)(MW ).(6) 2) Minimum Ex eme Condi ions: ma ching he minimum ex eme condi ions ha may occu . I is equal o he di e ence be ween he min- imum ex eme o DLD (lowe p edic ion le el 95 %) and he maximum ex eme o PVP: PROZ(min)=POBD(min)−PF V E(max)(MW ).(7) These cu es Eq. (6) and Eq. (7) a e po ayed in Fig. 6. They demons a e he maximum ex eme con- di ions ha may occu o a ele an ou le o he g id a he ou going eede om he subs a ion. In o de o Fig. 6: Subs a ion ou le ex eme condi ions. con ol o de eloped me hodology, he measu ed da a o lowing powe a he poin o he subs a ion ( he blue cu e om Fig. 3) a e plo ed in calcula ed compe en h esholds o cu es desc ibing he minimum and max- imum ex eme powe (desc ibed in Fig. 5) which could occu a he ou le om he subs a ion plan . This si ua ion shows Fig. 7. All he da a and e alua ion me hodology we e conside ed wi h he eliabili y le el o 95 %. This pa icula case conce ns 95.54 % o alues si ua ed wi hin he de ined ou pu ex eme condi ions. This ac jus i ies he co ec ness o he p ocess. Fig. 7: Con ol o adjus men o powe ou pu di e ence esh- olds. 5. Sugges ed Me hodical Models 5.1. Assessmen Me hodology The p ocess o assessmen me hodology is desc ibed by he block diag am in Fig. 8. The diag am is di ided in o h ee e ical and h ee ho izon al sec ions. Ve - ical columns a e sepa a ed by a dashed ec o , and ho izon al lines a e highligh ed by blue backg ound. c 2014 ADVANCES IN ELECTRICAL AND ELECTRONIC ENGINEERING 188 POWER ENGINEERING AND ELECTRICAL ENGINEERING VOLUME: 12 |NUMBER: 3 |2014 |SEPTEMBER 1) Ve ical Sec ions The i s column ep esen s measu ed da a undamen- al o he es ablishmen o his me hodology. The second column p o ides a desc ip ion o sug- ges ed calcula ion me hodology. The i s s ep equi ed p ocessing o da a, o he so-called Pos -P ocessing (block P.-P ocess.). The nex s ep was o enume a e ex eme condi ions o powe ou pu o pho o ol aic powe plan s (block Ex . PVP), ex eme condi ions o he daily load diag am (Ex . DLD) and ex eme condi ions a he ou going eede om he subs a ion (Ex . SUB). De e mina ion o Ex . SUB i s ly e- qui ed ob aining he da a wi hou impac o p oduc- ion om he PVP. This da a ep esen s so-called he ow da a (only loads) o daily load diag am (block DLD). The ow da a was de e mined by sub ac ion o he immedia e ou pu da a du ing ope a ion o PVP om he immedia e ou pu da a measu ed a he sub- s a ion. This sub ac ion is subjec o accu a e syn- ch onising (block Synch.) o bo h se s o da a mea- su ed. Subsequen ly, ex eme condi ions o DLD we e e alua ed. Sui able sum o Ex . DLD and Ex . PVP can help wi h assessmen o ex eme condi ions occu - ing a he subs a ion (block SUM Ex .). The las column con ains di e ences o ac i e powe o he PVP (block P di . P P) and he da a measu ed a ou going eede om he subs a ion (block P di . SUB and P di . DLD). 2) Ho izon al Sec ions As p e iously men ioned, he diag am is also di ided in o h ee ho izon al lines. The i s line comp ises blocks linked by means o ed a ows. These desc ibe he s eps o assessmen o powe di e ences on he PVP i sel only. This indica- o does no include he impac o daily load diag am. This assessmen is hen used o de e mine he model si ua ions o indi idual mon hs wi h u he po en ial o lexible al e a ions acco ding o he panel ype al- eady known and i s nominal peak powe . This s ep is he mos impo an and di icul o all e alua ion. The las ho izon al line con ains blocks linked wi h g een a ows. The da a measu ed a subs a ion in- cludes he impac o PVP ope a ion oo. De e mina- ion o he di e ence o ac i e powe in his manne is co ec , al hough dedica ed only. I canno be ap- plied o ano he model si ua ion in a b oade sense, being limi ed o hese speci ic da a measu ed a his pa icula subs a ion and he ele an PVP. These issues do no also deal wi h a case, when he di e ence o ac i e powe would change wi h he con- s uc ion o a new PVP wi hin he pa icula loca ion. The second line p o es i sel as an op imal solu ion, and i is linked o blocks using blue a ows. We need o ealize ha ex eme condi ions o powe a he sub- s a ion occu due o ex eme condi ions on bo h he PVP as well as a daily load diag am. As men ioned p e iously, he da a measu ed a ou going eede om he subs a ion mus be educed by sub ac ing he da a pe aining o powe p oduced by he PVP. This s age al eady enables o de e mine he ex eme condi ions o daily load diag am as well as PVP o any ypes o panels wi h a ying peak powe igu es. Model si ua ions o ex eme condi ions o PVP may also be use ul o a ious model o simula ion p ocesses, whe e he change o load diag am is al eady an ici- pa ed. 5.2. Calcula ion Model The sugges ed assessmen me hodology can be used o se up a calcula ion model. The calcula ion model con ains blocks linked wi h ed a ows. The main ad an age o he e y assessmen o ex- eme s a es o PVP and DLD has been desc ibed abo e. This idea has been also ans e ed in o he cal- cula ion model. Ano he i e u able ad an age b ough by analysis o such sepa a ed da a is a mo e accu a e ma hema ical desc ip ion. I has o be ealized ha he DLD and PVP p oduc ion cu es di e g ea ly in na u e ha is also one o he easons, why examin- ing ei he ex eme sepa a ely is mo e con enien be- o e calcula ion o model si ua ion o ex eme condi- ions o PVP (block PVP) equi es knowledge o he panel ype and hei nominal peak powe igu es. Fu - he equi emen s o be me include he p econdi ion assuming s a ic posi ion o he panel in o de o maxi- mize p o i (inclina ion a app ox. 38◦wi h espec o he ho izon al plane and sou hwa ds o ien a ion). The ed a ow in Fig. 8 ep esen s he in eg a ion o model ex eme condi ions o PVP in o he calcula ion p ocess and he poin o assessmen . The poin o assessmen (block 110/22), which is o be used o assessmen o he powe di e ence, mus be iden i ied wi h he na- u e o powe load - he daily load diag am. These load cu es a e usually moni o ed by dis ibu o s a ce ain i al poin s. Da a o igina ing om a ious model o simula ion p ocesses can be also used. 5.3. Annual Ex eme Condi ions o PVP Maximum ex eme condi ions o p oduc ion a e de- sc ibed in Fig. 9 and Fig. 10. Figu e 9 co e s mon hs wi hin he pe iod om Decembe ill June, i.e. he pe iods o win e and summe sols ice. One can no- c 2014 ADVANCES IN ELECTRICAL AND ELECTRONIC ENGINEERING 189 POWER ENGINEERING AND ELECTRICAL ENGINEERING VOLUME: 12 |NUMBER: 3 |2014 |SEPTEMBER Fig. 8: Block diag am o assessmen me hodology. ice ha he dispe sion o p oduc ion ime is ex ended p opo ionally o he inc easing du a ion o sunshine wi hin pa icula mon hs, and he ampli ude is ising wi h inc easing in ensi y o sola adia ion. The maxi- mum occu s in May a he ha du ing he summe sol- s ice, as migh be expec ed. This case he e o e leads o he es ablishmen o an op imal a io be ween he in ensi y o sola adia ion and a e age empe a u e du ing he pa icula mon h (p e ious mon hs indica e lack o sola adia ion and he subsequen mon hs b ing highe ambien empe a u e wi h a nega i e impac on panel e iciency). Figu e 10 shows maximum cu es Fig. 9: Ex eme condi ions o PVP, Decembe o June. om July ill Decembe , i.e. be ween he summe and win e sols ice. Fig. 10: Ex eme condi ions o PVP, July o Decembe . 6. Conclusion B ie ly speaking, his measu emen is used o sugges- ion o a gene al calcula ion me hodology o assess- men o di e ence o ac i e powe a a pa icula node o he g id unde a ious ic ional changes o powe om he pho o ol aic powe plan o he whole sola c 2014 ADVANCES IN ELECTRICAL AND ELECTRONIC ENGINEERING 190 POWER ENGINEERING AND ELECTRICAL ENGINEERING VOLUME: 12 |NUMBER: 3 |2014 |SEPTEMBER a m, o e en in case o expec ed changes o p edic ions in he daily load diag am. Compa ing maximum ex- emes o each mon h indica es signi ican di e ences. I is clea ha di e en pe iods du ing he yea ha e in luence o he assessmen o Ancilla y Se ices. Nex S eps o his s udy will ocus on he applica ion o his me hodology on a ull da abase and e alua ion he e- la ionship o each mon h o Ancilla y Se ices. Acknowledgmen This wo k was suppo ed by he Minis y o Educa- ion, You h and Spo s o he Czech Republic (No. SP2014/187) and by he p ojec ENET (Resea ch and De elopmen o Inno a ions Ope a ional P og ammes No. CZ.1.05/2.1.00/03.0069). Re e ences [1] VSB-TU Os a a, Depa men o Elec ical Powe Enginee ing. "Da a sou ce". VSB-TU Os a a 2013: unpublished. [2] SMOCEK, M. and Z. HRADILEK. Me hodology o E alua ion Ex eme Powe Condi ions o Pho- o ol aic Powe Plan s. In: 14 h In e na ional Sci- en i ic Con e ence on Elec ic Powe Enginee ing, EPE 2013. Kou y nad Desnou: VSB-Technical Uni e si y Os a a, 2013, pp. 20–23. ISBN 978- 80-248-2988-3. [3] HRADILEK, Z. and T. SUMBERA. Simula o o Powe Fo ecas ing Gained om Wind Powe Plan s. P zeglad Elek o echniczny. 2010, ol. 86, no. 8, pp. 196–199. ISSN 0033-2097. [4] HRADILEK, Z. and T. SUMBERA. Reliabili y and P edic ions o Powe Supplied by Wind Powe Plan s. In: In e na ional Con e ence on Renew- able Ene gies and Powe Quali y. Las Palmas de G an Cana ia: Uni e si y o La Co una, 2011, pp. 254–259. ISBN 978-84-614-7527-8. [5] PIOTROWSKI, P. Analiza s a ys y- czna danych do p ognozowania ul a- k o ko e minowego p odukcji ene gii elek ycznej w sys emach o owol aicznych. P zeglad Elek- o echniczny. 2014, ol. 90, no. 4, pp. 1–4. ISSN 0033-2097. [6] JIE, S., L. WEI-JEN, L. YONGQIAN, Y. YONG- PING and P. WANG. Fo ecas ing powe ou pu o pho o ol aic sys em based on wea he classi i- ca ion and suppo ec o machine. In: Indus y Applica ions Socie y Annual Mee ing (IAS). O - lando: IEEE, 2011, pp. 1–6. ISBN 978-1-4244- 9498-9. DOI: 10.1109/IAS.2011.6074294. [7] YONA, A., T. SENJYU, A. SABER, T. FUN- ABASHI, H. SEKINE and K. CHUL-HWAN. Applica ion o neu al ne wo k o 24-hou ahead gene a ing powe o ecas ing o PV sys em. In: Powe and Ene gy Socie y Gene al Mee - ing - Con e sion and Deli e y o Elec i- cal Ene gy in he 21s Cen u y. Pi sbu gh: IEEE 2008, pp. 1–6. ISBN 978-1-4244-1905-0. DOI: 10.1109/PES.2008.4596295. Abou Au ho s Ma in SMOCEK was bo n in H anice. In 2011 he g adua ed VSB-Technical Uni e si y o Os a a, Facul y o Elec ical Enginee ing and Compu e Sci- ence, elec ical powe enginee ing. Today he is Ph.D. s uden in he Depa men o Elec ical Powe Engi- nee ing, VSB-Technical Uni e si y o Os a a and he applies himsel o he issue o pho o ol aic powe plan . Zdenek HRADILEK was bo n in B no. A e g adua ion o college educa ion a Facul y o Elec ical Enginee ing and Compu e Science B no Uni e si y o Technology in 1962 he wo ked as a echnician in company Sou he n Mo a ian powe plan s in B no, han he wo ked as a majo powe -supply di ec o in Hea -supply Os a a and om 1966 un il now he is a he VSB-Technical Uni e si y Os a a. His scien i ic p epa a ion g adua ed by his candida e disse a ion de ending a he B no Uni e si y o Technology in 1972. He de ended his doc o al hesis a he Czech Technical Uni e si y in P ague in 1988 and was appoin ed as p o esso . c 2014 ADVANCES IN ELECTRICAL AND ELECTRONIC ENGINEERING 191