Application of traction supply system for charging electric cars

  Ci a ion: Ba łomiejczyk, M.; Ja zebowicz, L.; H báˇc, R. Applica ion o T ac ion Supply Sys em o Cha ging Elec ic Ca s. Ene gies 2022,15, 1448. h ps:// doi.o g/10.3390/en15041448 Academic Edi o : Ma io Ma chesoni Recei ed: 31 Janua y 2022 Accep ed: 14 Feb ua y 2022 Published: 16 Feb ua y 2022 Publishe ’s No e: MDPI s ays neu al wi h ega d o ju isdic ional claims in published maps and ins i u ional a il- ia ions. Copy igh : © 2022 by he au ho s. Licensee MDPI, Basel, Swi ze land. This a icle is an open access a icle dis ibu ed unde he e ms and condi ions o he C ea i e Commons A ibu ion (CC BY) license (h ps:// c ea i ecommons.o g/licenses/by/ 4.0/). ene gies A icle Applica ion o T ac ion Supply Sys em o Cha ging Elec ic Ca s Mikołaj Ba łomiejczyk 1,*, Leszek Ja zebowicz 1and Roman H báˇc 2 1Facul y o Elec ical and Con ol Enginee ing, Gdansk Uni e si y o Technology, Na u owicza s . 11/12, 80-233 Gdansk, Poland; [email p o ec ed] 2Depa men o Elec ical Enginee ing (420), 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; [email p o ec ed] *Co espondence: [email p o ec ed] Abs ac : The de elopmen o elec omobili y in ol es he de elopmen o elec ic ca s cha ging in as uc u e. The inc ease o he numbe o cha ge s poses new demands o he AC powe g id, especially in ega d o i s capaci y o deli e ing high peak powe . As an al e na i e o he public AC powe g id, u ban elec i ied anspo a ion sys ems ( ams, olleybuses, and me o) can be used o supplying elec ic ca s cha ge s. The a icle discusses ou op ions o in eg a ing elec ic ca s cha ge s wi h a ac ion powe supply sys em. The op ion o connec ing he cha ge o he ac ion o e head supply line has been selec ed due o he spa ial a ailabili y o he powe sou ce and possibili y o use egene a i e b aking ene gy o cha ging. A se o c i e ia has been de eloped o analysing he capabili y o he ac ion supply sys em o eed elec ic ca s cha ge s. An exempla y easibili y analysis was ca ied ou o olleybus ac ion supply sys em in Gdynia, Poland. The impac o ins alling he cha ging s a ion on speci ic ac ion supply pa ame e s has been p edic ed using p esen -s a e eco dings o elec ical pa ame e s and assumed cha ging s a ion powe . The s udy shows ha e e y supply sec ion o he conside ed olleybus ac ion sys em has he capabili y o ins alling a as -cha ging s a ion, which p o ides oppo uni ies o expanding he cha ging s a ions ne wo k in Gdynia. Keywo ds: elec ic ca s; EV cha ging; elec omobili y; olleybuses; ac ion powe supply 1. In oduc ion The expansion o elec omobili y equi es he de elopmen o he elec ic powe dis ibu ion in as uc u e. In pa icula , i is essen ial o p o ide a dense ne wo k o elec ic ca s cha ging s a ions. This, in u n, leads o he inc eased demand o powe and ene gy d awn om he powe dis ibu ion sys em, which o en equi es subs an ial de elopmen o his sys em [ 1 ]. The use o mode n sma g id echnologies, such as Vehicle o G id (V2G) [ 2 , 3 ], can be ex emely use ul o his pu pose. Thanks o V2G echnologies, elec ic ehicles can ac as powe -balancing p osume s, suppo ing he powe sys em [4,5]. V2G echnologies a e usually associa ed wi h he comme cial AC powe g id [ 6 , 7 ]. Howe e , an elec ic ehicle may also be a p osume in he elec ic ac ion powe supply sys em o ailways, ams, o olleybuses. As he powe demand in ac ion supply sys ems a ies in a much wide ange han in comme cial sys ems [ 8 ], he demand o powe - balancing means is e en mo e signi ican [ 9 , 10 ]. The au ho s o [ 11 ] p oposed o use elec ic ehicles cha ging s a ions ins alled a he Kochi Me o Rail Sys em o suppo he supplying g id in e ms o load balancing, ha monic elimina ion, and eac i e powe compensa ion. By simula ion and expe imen al s udy, i has been p o en ha cha ging s a ions connec ed o he s ep-down ans o me o a me o ac ion subs a ion can ac as an ancilla y se ice p o ide . Ene gies 2022,15, 1448. h ps://doi.o g/10.3390/en15041448 h ps://www.mdpi.com/jou nal/ene gies Ene gies 2022,15, 1448 2 o 13 The peak load limi a ion o he AC dis ibu ion ne wo k aises easonable conce ns in ega d o g id s abili y unde he load o elec ic ca cha ge s [ 12 ]. The mos commonly p oposed solu ion o his p oblem is in eg a ing he cha ge s wi h ene gy s o ages and pho o ol aic sys ems [ 13 ]. The i s la ens he powe demand o he cha ge , while he la e pa ially co e s his demand. Howe e , due o he equi ed a ings o hese de ices, hei cos is subs an ial. The e o e, an in e es ing solu ion o o e come he peak load limi a ion o he AC dis ibu ion g id is o supply pa o he cha ging s a ions om u ban ac ion powe supply sys ems. Such sys ems usually ha e a la ge peak powe ese e, which may be used o co e he powe demand o addi ional de ices [ 14 ]. As pa king lo s wi h elec ic ca cha ge s a e o en loca ed nea anspo a ion nodes, he in eg a ion o cha ge s wi h ac ion powe supply sys ems does no equi e long powe cables [5,12]. A cha ge supplied by he u ban ac ion powe supply sys ems may be connec ed o a powe subs a ion (as assumed in [ 11 ]) o o he DC ac ion o e head line. The second solu ion p o ides addi ional bene i s, such as he la ge spa ial a ailabili y o he o e head line. Mo eo e , a subs an ial pa o ac ion powe sys ems is equipped wi h ene gy s o age sys ems, which collec ene gy om he egene a i e b aking o he ehicles. Such s o age is usually connec ed o he DC pa o he sys em and—when me ged wi h elec ic ehicles cha ges—may po en ially c ea e a lexible sma g id sys em [8]. An in e es ing s udy o in eg a ing elec ic ehicle cha ge s has been epo ed in [ 13 ]. The au ho s conside ed supplying elec ic ehicle cha ge s om he 750 V DC ac ion o e head line o a public am in Edinbu gh, Sco land. The s udy discusses cha ging con ol s a egies, as well as ea hling and wide sys em p o ec ion equi emen s. Ano he s udy [ 15 ] analyses cha ging s a ions supplied om he olleybus DC ac ion o e head line in Solingen, Ge many. The au ho s p opose a mul i- ehicle-cha ging concep , which maximizes he cha ge poin s a ailabili y despi e powe limi a ions p esen on he sup- ply le el. This a icle includes an exempla y assessmen o he easibili y o using a olleybus powe sys em o supplying elec ic ca cha ging s a ions. Fou op ions o in eg a ing elec ic ca cha ge s wi h a ac ion powe supply sys em ha e been discussed. The op ion o connec ing he cha ge o he ac ion o e head supply line has been selec ed, as i p o ides pa icula ad an ages when compa ed o he supply om he public AC g id. The p esen s a e o olleybus ac ion powe supply in Gdynia has been e alua ed by he analysis o eco dings ca ied ou in ac ion subs a ions and ehicles. Nex , using he linea na u e o he sys em, he powe supply pa ame e s we e co ec ed acco ding o he assumed powe o he cha ging s a ions. Finally, he pa ame e s we e e alua ed in ega d o he p ope ope a ion o he sys em. The e alua ion shows ha he olleybus ac ion powe supply in Gdynia has subs an ial ese es and could be used o supply as cha ging s a ions. 2. Op ions o In eg a ing Cha ge s in o he T olleybus Powe Supply Sys em T olleybuses a e powe ed by an o e head dual-pole DC ac ion con ac line. The ac ion line is di ided in o supply sec ions (Figu e 1). Indi idual sec ions a e powe ed by supplying wi es (so-called eede s) om ac ion subs a ions. The ac ion subs a ions ans o m he AC powe in o DC and dec eases he ol age o a sui able le el. The nominal DC ol age in a olleybus supply sys em, anges om 600 o 725 V. Due o ol age d ops a he eede s and a he o e head line, he idle ou pu ol age o subs a ions is se app oxima ely o 110% o he a ed alue, i.e., 660 V o 825 V [16]. Ene gies 2022,15, 1448 3 o 13 Figu e 1. Gene al scheme o olleybus powe supply sys em. The connec ion o ehicle cha ging s a ions and he u ban anspo ene gy sys em can be ca ied ou in di e en manne s, which is shown in Figu e 2. Figu e 2. Possibili ies o supplying elec ic ehicle cha ging s a ions om a ac ion powe sys em. The cha ging s a ion may be connec ed o he DC le el, i.e., di ec ly o he ac ion o e head line (op ion 1 in Figu e 3) o o he DC busba s in he subs a ion (op ion 2). Such solu ions allow he bes syne gy be ween he sys ems, mainly due o he possibili y o di ec ing he olleybuses egene a i e b aking ene gy o he cha ging s a ions. An addi ional ad an age o d awing he powe om he o e head con ac line (op ion 1) is he la ge spa ial accessibili y o he o e head ac ion line. The powe ha can be d awn om he o e head line by he cha ging s a ion depends on he dis ance om he ac ion subs a ion and he design o he ac ion ne wo k. Unde a ou able condi ions (close p oximi y o he subs a ion and la ge c oss-sec ion o he o e head line), i can be a he le el o 200–300 kW, bu in mos cases he a ailable powe is app oxima ely 50–100 kW. Supplying he cha ging s a ion om he DC pa o he ac ion powe sys em (bo h op ions 1 and 2) equi es he use o a DC/DC powe -elec onic con e e , which is no a ypical solu ion, hus subs an ially inc easing he cos s o he sys em. In u n, powe ing he cha ging s a ions om he AC ol age (op ions 3 and 4) uses s anda d solu ions, which makes i inexpensi e. Howe e , he AC ol age is a ailable only in ac ion subs a ions. A de ailed compa ison o all he op ions is included in Table 1. The exempla y elec ic ehicles cha ging sys em powe ed by he am o e head line has been launched in Obe hausen, Ge many (Figu e 3). I consis s o a DC/DC con e e (Figu e 4), h ee elec ic ca s cha ging s a ions and one elec ic bus cha ging s a ion. Ene gies 2022,15, 1448 4 o 13 Figu e 3. Cha ging s a ion o elec ic bus and elec ic ca s powe ed om he am o e head line in Obe hausen, Ge many. Table 1. Compa ison o he possibili ies o supplying elec ic ehicle cha ging s a ions om ac ion powe sys em. Op ion No. Supply Me hod Supply Vol age Ad an ages Disad an ages Op ion 1 Powe supply om o e head ac ion line 600 V DC (1) La ge spa ial a ailabili y o he powe sou ce; (2) Syne gy be ween ac ion powe supply and ehicle cha ge s. (1) Limi a ions ela ed o he cu en load capaci y o he ac ion ne wo k; (2) Vol age luc ua ions; (3) Possible powe ou ages; (4) De e io a ion o he powe supply pa ame e s o ehicles; (5) Necessi y o use a DC/DC con e e . Op ion 2 Powe supply om DC busba s o ac ion subs a ion 600 V DC (1) High powe a ailable; (2) Syne gy be ween ac ion powe supply and ehicle cha ge s. (1) Applicable only in he icini y o subs a ions; (2) Necessi y o use a DC/DC con e e . Op ion 3 Powe supply om he seconda y ci cui s o ec i ie ans o me s 525 V AC (1) High powe a ailable. (1) Applicable only in he icini y o subs a ions. Op ion 4 Powe supply om auxilia y ci cui s o ac ion subs a ions 400 V AC (1) Possibili y o using ypical cha ge s (wi hou ans o me s o powe con e e s). (1) Applicable only in he icini y o subs a ions; (2) Limi ed powe a ailable. Figu e 4. DC/DC con e e used o powe ing a cha ging poin o elec ic buses and ca s om a am o e head line in Obe hausen, Ge many. Ene gies 2022,15, 1448 5 o 13 3. Elec ic Ca s Cha ging S a ion in Gdynia, Poland In he ci y o Gdynia (Poland), a con e e s a ion ha allows he use o a ac ion sys em o supply ecei e s wi h indus ial ol age o 400 V AC was launched in 2021 as a esul o he “E icienCE” p ojec [ 17 ]. The con e e links a olleybus o e head line o an elec ic ehicle cha ging hub. In o de o inc ease he eliabili y o he powe supply (e.g., in he e en o excessi e d ops o con e e inpu ol age) and o inc ease he lexibili y o accumula ion o olley- buses egene a i e b aking ene gy, he s a ion was equipped wi h a ba e y-based elec ic ene gy s o age. Fo his pu pose, a second-li e ac ion ba e y om a olleybus was used (Figu e 5). Figu e 5. DC/AC con e e o con e sion con e ing olleybus 600 V DC o e head line ol age in o a 400 V AC comme cial s anda d (ope a ing in Gdynia, Poland; he ba e y-based ene gy s o age is in he box placed on he loo ). The powe con e sion p ocess is spli in o wo s ages (Figu e 6). Fi s , he sys em uses he DC/DC con e e , which p o ides gal anic sepa a ion om he ac ion ne wo k ol age and egula es he ba e y cha ging cu en [ 18 ]. Nex , he DC/AC con e e deli e s he powe o he cha ging s a ion ia an addi ional ans o me used o insula ion pu poses. The cha ging s a ion is supplied by 3 × 400 V AC, which is a comme cial s anda d. Hence, a ypical as cha ge o elec ic ca s was used. Figu e 6. Gene al connec ion scheme o he cha ging s a ion and he olleybus powe supply line in Gdynia, Poland. 4. Feasibili y o Using T olleybus T ac ion Sys em o Supplying Cha ge s The solu ion o using a olleybus ac ion sys em o supply elec ic ehicle cha ge s, p esen ed in he p e ious sec ion, which has been a subjec o a ial ope a ion, p o es he echnological ma u i y o he equi ed equipmen . Howe e , he selec ion o a ge loca ions o simila solu ions equi es comp ehensi e analysis. Ene gies 2022,15, 1448 6 o 13 T ac ion powe supply sys ems a e ea u ed by high load a iabili y, which is a esul o a a iable numbe o ehicles wi hin he supply sec ion and hei a iable d i ing s a e [ 19 ]. The powe demand may suddenly change om la ge posi i e ( ew ehicles simul aneously accele a ing) o idle o e en nega i e ( egene a i e b aking) in a ew seconds. The a iable load causes la ge ol age luc ua ions in he o e head con ac line. Fo his eason, i equi es specialized ools o ene gy analyses. The analysis p esen ed in his sec ion uses da a eco ded om he olleybus ac- ion supply ne wo k in Gdynia. In addi ion, da a om olleybuses on-boa d eco de s we e used. In o de o de e mine he possibili ies o using he olleybus ne wo k o supply cha ging s a ions, an analysis o he load le el and ol age in o e head supply lines o he olleybus sys em was ca ied ou . Supplying he cha ging s a ion om he olleybus o e head line is associa ed wi h an inc ease in he o e head line load. The ollowing limi a ions o his inc ease should be conside ed a pa icula supply sec ions: •Maximal cu en load, •Maximal allowable ol age d op, •Maximal accep able ansmission losses. The abo e limi a ions a e summa ized in Table 2and discussed in he ollowing subsec ions. Table 2. C i e ia o e i ica ion o possibili y o use olleybus o e head line o supply elec ic ca s cha ging s a ions. C i e ion Desc ip ion Commen (I) Maximal load cu en - Fo he eede s ( ypically YAKY 630 cables), he maximum long- e m load cu en is 1000 A; - Fo he o e head wi e, he maximum long- e m load cu en o a single wi e is 420 A. The o e head con ac line consis s o wo pa allel-connec ed unways, he e o e he accep able con inuous load is 840 A. The maximal con inuous load o a powe sec ion canno exceed 840 A (II) Maximal ol age d ops The ollowing c i e ia can be de e mined in calcula ions and echnical analyses: - 2A: he minimal ins an aneous ol age in he o e head con ac line is 400 V; - 2B: he a e age alue o he ol age d op in he supply sys em (be ween he subs a ion and he mos dis an poin o he supply sec ion) should no exceed 150 V; - 2C: he allowed mean ol age d op a he olleybus cu en collec o is 99 V. The 2B c i e ion is simila o 2C, hus only 2A and 2C need o be conside ed (III) Accep able powe loses The e a e no clea c i e ia; howe e , i is commonly assumed ha ansmission losses in he o e head con ac line should no exceed 10% The ansmission losses should no exceed 10% 4.1. C i e ion I: Maximal Load Cu en The analysis was made wi h he assump ion ha he cha ging s a ions d aw a cons an powe o 44 kW (2 s a ions, 22 kW each). Such a powe was ecalcula ed in o he load cu en (app oxima ely, 80 A a he a ed ol age 600 V and 100 A upon a ol age d op o 400 V) and added o he cu en eco ded du ing olleybus powe sys em ope a ion. The esul s o he analysis o he cu en load on pa icula powe sec ions in he olleybus supply sys em o Gdynia a e p esen ed in Figu e 7. The analysis is based on eco dings ca ied ou du ing low ambien empe a u e pe iod, which ansla es o he highes powe demand ela ed o elec ic hea ing o he olleybuses [ 20 ]. The maximum alue o he load is app oxima ely 300 A, which p o ides a la ge ma gin when compa ed o he limi o 840 A. Hence, i is concluded ha he addi ional load would no esul in exceeding he maximal load cu en alue. Ene gies 2022,15, 1448 7 o 13 Figu e 7. Resul s o compu a ion o a e age load cu en o pa icula supply sec ions (assumed powe o he cha ging s a ion: 44 kW). 4.2. C i e ion II: Maximal Vol age D op In associa ion o c i e ion 2C, desc ibed in Table 2, Figu e 8p esen s he esul s o eco dings o he a e age use ul ol age on olleybus collec o s g ouped in o indi idual powe sec ions. The inpu da a we e ob ained om on-boa d olleybuses eco de s. Figu e 8. A e age ol ages a olleybuses cu en collec o s on pa icula supply sec ions (no cha ging s a ion). Wi h he excep ion o he “Ha ce ska” sec ion, which is p esen ly unde going mode n- iza ion, he ol age alues a e in he ange be ween 645 V and 685 V. The ou pu ol ages o he subs a ions a e se a he le el o 680–690 V. Hence, he a e age d op does no exceed 50 V, which p o ides a la ge ma gin o he pe mi ed alue o 99 V. The addi ional load ela ed o he cha ging s a ion o elec ic ca s would inc ease he ol age d ops p esen ed in Figu e 8. Due o he linea na u e o he elec ic ci cui s, he o al ol age d op may be calcula ed by means o supe posi ion, i.e., as a sum o p esen ol age d op and he d op ela ed o he cha ging s a ions. Ins an aneous d op ∆Ud op ela ed o he cha ging s a ions may be calcula ed as: ∆Ud op( )=Icha ( )·Rk, (1) Ene gies 2022,15, 1448 8 o 13 whe e: I cha is he cu en collec ed by he cha ging s a ions and R k is he sho ci cui esis ance o he o e head line a he poin o he cha ging s a ions’ loca ion. The ol age d op, ∆Ud op , was compu ed o he mos un a ou able condi ions. The loca ion o cha ging s a ions was assumed a he end o powe sec ion, which leads o he g ea es alue o esis ance R k . Mo eo e , he powe d awn by he cha ging s a ions was assumed cons an and equal o 44 kW, which ansla es in o I cha = 83 A. Assuming cons an Icha makes he ins an aneous ol age d op (1) equal o he a e age d op. Table 3lis s he sho ci cui esis ances and he inc ease in ol age d ops o pa icula powe sec ions. The compu ed alues o he ol age d op ange app oxima ely om 7 o 37 V, which is a below he 50-V ma gin de i ed om he eco dings (Figu e 8). Table 3. Sho ci cui esis ances and compu ed inc ease in ol age d ops o pa icula powe sec ions. Sec ion Maximal Sho Ci cui Resis ance [Ω] Inc ease ∆Ud op [V] in Vol age D op Rela ed o Cha ging S a ions Cisowa 0.19 15.8 Pocz a 0.09 7.5 Gazownia 0.36 30.0 Wiejska 0.44 36.7 Kcy´nska 0.37 30.8 Pus ki 0.52 43.3 Leszczy´nki 0.17 14.2 G abowek 0.23 19.2 Mlecza nia 0.36 30.0 Dwo zec Towa owy 0.17 14.2 Kołł ˛a aja 0.32 26.7 10 lu ego 0.13 10.8 Plac Kaszubski 0.25 20.8 Plac Kons y ucji 0.19 15.8 ´ Swi˛e oja´nska 0.32 26.7 S ocznia 0.34 28.3 Wzgó ze 0.26 21.7 Redłowo 0.35 29.2 Kack 0.42 35.0 Wielkopolska 0.30 25.0 Wajdelo y 0.21 17.5 ´ Z ódło Ma ii 0.24 20.0 Nowowiczli´nska 0.24 20.0 Mi˛e owa 0.28 23.3 Rdes owa 0.24 20.0 Chwaszczy´nska 0.31 25.8 Kamienny Po ok 0.18 15.0 In associa ion o c i e ion 2A, desc ibed in Table 2, Figu e 9shows he esul s o measu emen s o he minimum ol age le el U min in he Gdynia olleybus ne wo k (g een ba s). I should be emphasized ha due o he andom na u e o olleybus ope a ions, hese alues should be ea ed as indica i e. In addi ion o he p esen s a e (g een), Figu e 9 includes he es ima ed minimum ol age U min_cha compu ed o assumed powe o elec ic ca cha ging s a ions: 22 kW (blue) and 40 kW ( ed). The compu a ions we e ca ied ou o he mos un a ou able case o posi ioning he cha ging s a ions a he end o he powe supply sec ions. The alues we e ob ained by dec easing he measu ed alue o he minimal ol age d op by he addi ional ol age d op (1) caused by he cha ging s a ions. Ene gies 2022,15, 1448 9 o 13 Figu e 9. Minimal ins an aneous alues o he supply ol age in he o e head con ac line a pa icula supply sec ions. Connec ing a cha ging s a ion would no cause he supply ol age o d op below 400 V. I should be no ed ha in he e en o a supply ol age d op below 450 V, an uns able ope a ion o he cha ging s a ion may occu (swi ching o ). Howe e , such a si ua ion occu s a ely, up o se e al imes a week. To inc ease ope a ional eliabili y, i is possible o equip he cha ging s a ion wi h an ene gy s o age. Un o una ely, his would inc ease he complexi y o he sys em and inc ease in es men cos s. Impo an ly, he ol age close o he gi en minimal alues appea a ely ( ypically once a day, depending on he physical si ua ion), which is con i med by he analysis o he ela i e ime o he d ops (Figu e 10). Mos o he ime, he ol age in he o e head con ac line is abo e 600 V. Figu e 10. Rela i e ime o ol age dec ease below 500 V o pa icula powe supply sec ions, exp essed in pe mills.