Single Switched Capacitor Battery Balancing System Enhancements

Transcription

1 Enrgis 013, 6, ; doi:103390/n Aricl OPEN ACCESS nrgis ISSN wwwmdpicom/journal/nrgis Singl Swichd Capacior Bary Balancing Sysm Enhancmns Mohamd Daowd 1, *, Mailir Anoin 1, Noshin Omar 1,, Pr van dn Bossch and Jori van Mirlo 1 1 Elcrical Enginring and Enrgy Tchnology Dparmn (ETEC), rij Univrsii Brussl, Plinlaan, Brussl 1050, Blgium; s: mailiranoin@gmailcom (MA); noshomar@vubacb (NO); jvmirlo@vubacb (JM) Indusrial Scincs and Tchnology (IWT), Erasmus Univrsiy Collg, Nijvrhidskaai 170, Brussl 1070, Blgium; prvandnbossch@hbb * Auhor o whom corrspondnc should b addrssd; mdaowd@vubacb; Tl: ; Fax: Rcivd: 31 Dcmbr 01; in rvisd form: 31 January 013 / Accpd: 11 March 013 / Publishd: 18 April 013 Absrac: Bary managmn sysms (BMS) ar a ky lmn in lcric vhicl nrgy sorag sysms Th BMS prforms svral funcions concrning o h bary sysm, is ky ask bing balancing h bary clls Bary cll unbalancing hamprs lcric vhicls prformanc, wih ring individual cll volags dcrasing h bary pack capaciy and cll lifim, lading o h vnual failur of h oal bary sysm Qui a lo of cll balancing opologis hav bn proposd, such as shun rsisor, shuling capacior, inducor/ransformr basd and DC nrgy convrrs Th shuling capacior balancing sysms in paricular hav no bn subjc o much rsarch ffors howvr, du o hir prcivd low balancing spd and high cos This papr ris o fill his gap by brifly discussing h shuling capacior cll balancing opologis, focusing on h singl swichd capacior (SSC) cll balancing and proposing a novl procdur o improv h SSC balancing sysm prformanc This lads o a nw conrol sragy for h SSC sysm ha can dcras h balancing sysm siz, cos, balancing im and ha can improv h SSC balancing sysm fficincy Kywords: shuling capacior; singl swichd capacior; SSC; cll qualizaion; bary balancing; bary managmn sysm; BMS; MATLAB/Simulink

2 Enrgis 013, Abbrviaions BMS Bary managmn sysms DTSC Doubl-ird swichd capacior balancing E Elcric vhicl EPNG Exndd Parnrship for a Nw Gnraion of hicls Li-ion Lihium-Ion Li-Po Lihium-Polymr MSC Modularizd swichd capacior balancing PWM Puls widh modulaion RUL Rmaining usful lif SC Swichd capacior balancing SoC Sa of charg (%) SoH Sa of halh (%) SSC Singl Swichd Capacior balancing 1 Inroducion Th BMS procs h bary sysm from damag, prdics and incrass bary lif, and mainains h bary sysm in an accura and rliabl opraing condiion Bary pack clls imbalanc is a major hra o h bary sysm lif Th BMS prforms svral asks such as masuring h sysm volag, currn and mpraur, h clls sa of charg (SoC), sa of halh (SoH), and rmaining usful lif (RUL) simaion, procing h clls, hrmal managmn, conrolling h charg/discharg procdur, daa acquisiion, communicaion wih on-board/off-board moduls, monioring, soring hisorical daa and mos imporanly ask is h cll balancing [1] Wihou h balancing sysm, h individual cll volags will drif apar ovr im As wll as, h usabl capaciy of h oal bary pack will also dcras mor quickly during opraion ha lads o fail h whol bary sysm [1,] Qui a lo of cll balancing/qualizaion mhods hav bn proposd in [1 1] and rviwd in [1 7] Th bary balancing opologis can b dividd ino passiv and aciv balancing; Th passiv bary balancing mhods as proposd in [8,9] rmov h xcss nrgy from h fully chargd cll(s) hrough a passiv lmn, h rsisor, unil h chargs mach hos of h lowr cll(s) in h pack or a charg rfrnc lvl Th rsisor balancing can b ihr in fixd mod or swichd rsisor [1] Th aciv cll balancing mhods rmov h chargs from highr nrgy cll(s) and dlivr i o lowr nrgy cll(s) Aciv cll balancing uss rn opologis according o h aciv lmn for soring h nrgy such as capacior and/or inducor componn, as wll as, h nrgy convrrs as [1 1] Th shuling capacior balancing has bn subjc o rsarch [10 19] Is simpl conrol sragy and high fficincy ar offs by a long qualizaion im and rlaivly high cos Shuling capacior balancing mhods can b classifid ino four configuraions as shown in Figur 1: swichd

3 Enrgis 013, capacior (SC), doubl-ird swichd capacior (DTSC), singl swichd capacior (SSC) and modularizd swichd capacior (MSC) Figur 1 Shuling capacior aciv cll balancing opologis This papr focuss on h shuling capacior balancing opologis, approaching h mhodology from rn viwpoins, simulaing rn capacior bas balancing modls using MATLAB/Simulink, and comparing bwn various shuling capacior balancing mhods basd on circui configuraion and simulaion rsuls Finally, i proposs svral improvmns in h SSC balancing opology o ovrcom h swichd capacior long qualizaion im drawback, o dcras h sysm siz and o solv h problm of h fla volag curv of som yps of lihium-ion baris Shuling Capacior Cll Balancing Topologis Shuling capaciors cll balancing opologis, also known as Charg Shuling clls qualizaion [10 19] basically uiliz capaciors as xrnal nrgy sorag lmns for shuling h nrgy bwn h clls so as o prform h clls charg balancing Th capacior shuling can b cagorizd ino four shuling configuraions: h basic swichd capacior, doubl-ird swichd capacior, singl swichd capacior and modularizd swichd capacior opologis 1 Swichd Capacior Th swichd capacior (SC) illusrad in [1 5,10 13,18] is shown in Figur I rquirs n 1 capaciors and n bi-dircional swichs for balancing n clls Th SC conrol sragy is vry simpl bcaus i has only wo sas, shuling bwn h whol clls squnially, moving h swichs frqunly from h uppr posiion o h lowr posiion and again o h uppr on wih a small rs priod bwn ach ransiion and so on In addiion, i dos no nd any inllign conrol sragy, i can work in boh charging and discharging mods (a ligh load currns) and i opras wih high fficincy Th disadvanags of h swichd capacior opology ar is rlaivly long qualizaion im and is highr cos compard wih h swichd shun rsisor passiv balancing mhod

4 Enrgis 013, 6 15 Figur Swichd capacior cll balancing opology Doubl-Tird Swichd Capacior Th DTSC balancing mhod givn by [14 16,18] is a drivaion of h swichd capacior mhod Th rnc is ha, h DTSC uss wo capacior irs for nrgy shuling as shown Figur 3 As illusrad i nds n capaciors and n bi-dircional swichs for balancing n clls Figur 3 Doubl-ird swichd capacior cll balancing opology

5 Enrgis 013, Having mor irs mans mor pahs bwn baris, and hus lss impdanc for h ranspor of charg ovr a paricular disanc across h pack [14] Th advanag of h doubl-ird swichd capacior ovr h swichd capacior mhod is ha h scond capacior ir rducs h balancing im o mor han half In addiion, i can opra in boh rcharging and discharging wih high fficincy 3 Singl Swichd Capacior Anohr drivaion of h SC opology, h singl swichd capacior (SSC) opology [1,,4,5,17 19] maks us of only on capacior as shown in Figur 4 Th SSC nds a singl capacior and n + 5 bi-dircional swichs o balanc n clls, making i mor cos-fficin han SC and DTSC Figur 4 Singl swichd capacior cll balancing opology Conrol B 1 B ESR B 3 C B n A rlaivly simpl conrol sragy is always usd, whr h conrollr slcs h high and low nrgy clls and conrols h corrsponding swichs for shuling h nrgy bwn hm Howvr, mor advancd conrol sragis can b usd for incrasing h balancing spd, which will b discussd lar in h proposd conrol sragy Gnrally h capacior balancing usd for balanc mor han 4 clls bcaus of is siz and cos For sur if h capacior is usd for balancing 4 clls or lss (n 1) h SC will hav fwr swichs as mniond in Tabl 1 Bu for mor han 5 clls h SSC will hav lss swichs han h SC sysm Tabl 1 SC vs SSC balancing sysm swichs according o h numbr of clls No of clls SC swichs (n) SSC Swichs (n + 5)

6 Enrgis 013, Modularizd Swichd Capacior Modularizd swichd capacior (MSC) is anohr opology uilizing h shuling capacior mhod I is basd on bary pack modularizaion [19] as shown in Figur 5, dividing h bary pack ino groups or moduls Figur 5 Modularizd swichd capacior cll balancing [19] Insid ach modul a spara qualizaion sysm dals wih individual clls, whilas anohr qualizaion sysm opras on modul lvl This rducs h balancing im bu incrass h numbr of capaciors and h swichs (n 1 capacior low volag, 1 capacior high volag and n + 4 bi-dircional swichs o balanc n clls) Th main drawback of h MSC is ha, incrasing h numbr of swichs and capaciors will incras h losss and balancing sysm cos significanly 3 Shuling Capaciors Balancing Topologis Simulaion MATLAB/Simulink has bcom h lading sofwar for modling and simulaing dynamic sysms In his papr i is usd for simulaing h shuling capacior balancing opologis As a firs sp, h individual bary clls ar simulad Four lihium polymr (Li-Po) baris hav bn sd and hir modls paramrs simad according o [,3] Th chosn bary modl was proposd by h Exndd Parnrship for a Nw Gnraion of hicls (EPNG) [4] This bary modl faurs SoC, SoH and cycl numbr prdicion, variabl paramrs in funcion of SoC, mpraur and cycl numbr wih a ral paramrs variaion bwn h pack clls Th shuling capaciors bary balancing mhods (SC, DTSC and SSC) hav bn simulad using Simulink wih h suiabl conrol sysms and no load currn Four 1 Ah lihium-ion clls ar usd for h simulaion comparison, wih iniial SoCs of 87%, 85%, 78% and 76% rspcivly, wih a

7 Enrgis 013, %, 7% and % sa of charg (SoC) rnc bwn h wo nighboring clls, mans ha h highr SoC rnc is 11% or 13 Ah As wll as, h variaion in h baris modls paramrs hav bn uilizd Th balancing considrd o b occurrd if h maximum SoC rnc bwn h clls is 5% (06 Ah) MOSFET swichs ar usd in h simulaion Thy hav an inrnal on-rsisor, diod forward rsisor of 15, 10 milliohm rspcivly and h diod forward volag is 005 Th MOSFETs snubbr circuis ar 50 KΩ and 50 nf Th capaciors ar usd for SC and DTSC hav a capaciy of 33 mf wih ESR of 5 mω For h SSC h capacior usd has a capaciy of 100 mf wih ESR of 0 mω Th swiching frquncy (F) will b 00 Hz wih a duy cycl (D) of 45% Figurs 6 8 illusra h shuling capaciors opologis simulaions rsuls such as: h clls volags, SoCs, and currns, as wll as, h clls nrgy conn In som cass on of h capacior s volag and currn will b shown as wll Th nrgy losss during h balancing procss in Wh can b calculad from h subracion of h clls nrgis summaion a sar (bginning of h balancing procss) and a h nd (cll balancing has occurrd) Swichd capacior balancing simulaion rsuls is shown in Figur 6, doubl-ird swichd capacior balancing simulaion rsuls ar shown in Figur 7, and h singl swichd capacior simulaion rsuls ar illusrad in Figur 8 Figur 6 shows h SC balancing opology simulaion rsuls I is clar ha for an 11% SoC rnc bwn h highr and lowr clls, a vry long im is ndd for compl balancing In addiion, h low balancing currn during h final balancing phas (du o h lowr volag rncs) lads o a furhr incras of h balancing im I ook long qualizaion im abou 4 hours and vn mor Howvr, nrgy losss (abou 15 mwh during balancing) ar much lowr han wih h swichd rsisor passiv balancing sysm Figur 7 prsns h DTSC balancing opology simulaion rsuls As in h SC balancing sysm h balancing currns dcras along h balancing procss Th balancing im is lowr han for h SC bcaus of h xra capacior ir bu i is sill rlaivly long a abou 17 hours Jus lik h SC, h DTSC has high fficincy (abou 105 mwh loss during balancing) Figur 8 illusras h singl swichd capacior balancing opology simulaion rsuls Th low currns during h final balancing phas lad o a balancing im narly of 34 hours, which can b dcrasd hrough h us of a mor inllign conrol sragy Th SSC has mor fficincy han h SC and h DTSC (during balancing i loss abou 110 mwh) As an iniial conclusion from h prvious circuis and h simulaion rsuls i is clar ha; Th SSC has only on capacior and lss swichs whil h MSC balancing mhod uilizs mor capaciors and swichs han h radiional SC and DTSC balancing mhods Boh SC and DTSC hav a sraighforward conrol sragy, on h conrary, h SSC and MSC nd a rlaivly complx conrol Th SC and DTSC mhods wih a simpl conrol sragy hav a long final balancing im and hav a gra problm ha, whn h SoC rnc bwn h clls is small, as wll as, h

8 Enrgis 013, volag rnc, h qualizaion currn bcoms smallr Tha will incras h qualizaion im significanly Compard o h SC mhod, h DTSC has on mor capacior, howvr i dcrass h balancing spd up o 4%, som ims mor, of h normal SC Figur 6 Swichd capacior balancing simulaion rsuls (op o boom) h clls and capaciors volags, clls SoCs, currns, nrgis, and summaion of h clls nrgy

9 Enrgis 013, Figur 7 Doubl-ird swichd capacior simulaion (op o boom) clls and capacior C 1 (bwn clls 1&) volags, clls SoCs, currns, clls nrgis, and summaion of h clls nrgy

10 Enrgis 013, Figur 8 Singl swichd capacior balancing simulaion (op o boom) h clls and h capacior volags, clls SoCs, currns, nrgis, and summaion of h clls nrgy 4 Singl Swichd Capacior Conrol Sragy Singl swichd capacior cll balancing can opimiz is prformanc by using a mor fficin conrol sragy, rducing h capacior siz, h sysm cos, and h balancing im Th ida is o maximiz h shuling nrgy ransfrs bwn h clls, and minimizing h capacior siz and h balancing im This will b don by inllignly conrolling h swichs afr xracing h nrgy cos funcion(s) Convnionally h conrol of h SSC is basd on slcing h high volag, cll and low volag cll and shuling h nrgy from h highr cll ino h lowr on Th swich conrol can b classically prformd using a fixd frquncy (F) and duy cycl (D) ha conrols h swichd capacior quivaln rsisanc R qu, prsnd in Equaion (1) as a gnral cas [5,6] For normal duy cycl conrol, ypically T is fixd, and D 1 and D ar boh s clos o 50% Th rsisancs ar

11 Enrgis 013, narly qual as wll, so ha 1 and ar narly qual o (ESR + R Cll ) * C In his mhod a low quivaln rsisanc is paramoun for ffciv qualizaion givn by [5] as shown in Equaion (1): R qu DT 1 + xp( ) 1 = DT (1) fc 1 xp( ) This will no b vry ffcivly whn h volag rnc bwn h clls is small, whn h qualizaion currn bcoms smallr and h qualizaion im will incras significanly 41 SSC Proposd Conrol Sragy Th high charg cll capacior low charg cll nrgy shuling is a funcion of h capacior valu (C), swiching frquncy (F), sris quivaln rsisor (R Sq ), volag rn bwn h unbalancd clls ( ) and finally h duy cycl, on-priod, (D) Th proposd SSC balancing sragy will b basd on adaping hs facors as dscribd lar Saring from h capacior volag during charging wih an iniial volag i and final volag f as shown in h firs par of Figur 9, i can b xprssd as in Equaion (), and h corrsponding capacior currn can b formulad as Equaion (3) Ths quaions will b usd for xracing h swichd capacior shuling nrgy bwn h wo clls Figur 9 Capacior volag during shuling bwn wo clls C _ Ch arg ing = ( = f )(1 i (1 ) + ) + i i () i C _ Charging d 1 C = C = C = (3) d R Sq Thr ar som assumpions concrning h ransfrrd nrgy funcion Firsly, h capacior will swich from h lowr charg cll wih a volag of i and connc o h highr charg cll wih f

12 Enrgis 013, volag Scondly, h clls inrnal rsisanc is qual, so ha h sris quivaln rsisor (R Sq ) of h swichd capacior circui will b h sum of h capacior ESR and on cll inrnal rsisor and h im consan is qual o (ESR + R cll )*C or R Sq C Thirdly, h SSC nrgy is calculad during on charging priod only, so ha im ingraion will b from zro o on duy cycl DT Equaion (4) givs h nrgy ransfrrd from h highr charg cll o h capacior during h priod D 1 T or DT in Ws/puls This nrgy is a funcion of h capacior valu C, swiching frquncy F, clls volags, volags rnc, sris quivaln rsisor R Sq, and duy cycl D Th numbr of pulss (g, in on hour) should b addd ino h charging nrgy (Ws/puls) in Equaion (4) o b in Wh/h as in Equaion (5) This is shown in Figur 10: h op par shows h ransfrrd nrgy in Ws/puls and i has a rvrs rlaion wih h swiching frquncy Whil h boom par shows h ransfrrd nrgy in Wh/h and i has a dirc rlaion wih h swiching frquncy Figur 10 Capacior charging nrgy as a funcion of h swiching frquncy, (a) nrgy in Ws/puls; (b) nrgy in Wh/h (a) (b)

13 Enrgis 013, ) / ( ) ) ) ) ( ) (1 / Sq DT 0 Sq DT 0 Sq Sq Sq 0 Sq 0 arg puls Ws C C C C R d R d R R R d R i d i v Enrgy f F D f F D F D f DT i DT i DT i i i DT DT c c ing Ch = = + = + = + = + = + = + = = (4) ) / ( * ) ) arg h Wh F C Enrgy f F D f F D ing Ch = (5) Th capacior ransfrrd nrgy during on discharg puls can b calculad from h capacior discharg volag and currn as givn in Equaion (6): ) / ( * 0 Sq arg h Wh F v v C d R i Enrgy i F D i F D DT Disch + + = + = (6) Figurs show h rn rlaions bwn h charging nrgy as in Equaion (5) and is variabls C,, R Sq and D, rspcivly

14 Enrgis 013, 6 16 Figur 11 Capacior charging nrgy as a funcion of h capacior valu Figur 1 Capacior charging nrgy as a funcion of h clls volag rnc Figur 13 Capacior charging nrgy as a funcion of h sris quivaln rsisor R Sq

15 Enrgis 013, Figur 14 Capacior charging nrgy as a funcion of duy cycl D As shown in h Figurs and Equaion (5) h ransfrrd charging nrgy has rn rlaions wih C, F,, R Sq and D Th aim of h proposd SSC cll balancing conrol sragy is o maximiz his nrgy ransfr wih rspc o hs paramrs (C, F,, R Sq and D), as wll as, o kp his nrgy as high as possibl wihin any condiions g, variaion of on paramr such as dcrasing during h balancing priod 4 SSC Sragy Procding Th proposd conrol sragy for h SSC balancing can b summarizd in h following sps: 1 Exracing h funcion of h ransfrrd nrgy bwn h clls and h capacior [s Equaion (5)] This funcion can b asily maximizd for ransfrrd nrgy, bu has o ak ino accoun h fiv prmoniion variabls (C, F,, R Sq and D) Slcing h opimal capacior valu (minimum) by maximizing h nrgy funcion wih rspc o h capacior valu a rn swiching frquncis Th ransfrrd nrgy will b a funcion of (C, F), wih any arbirary and D bcaus h lar wo paramrs will vary during balancing priods 3 Afr slc h capacior valu wih h givn ESR, maximizing h nrgy ransfr wih h calculad C and R Sq valus as a funcion of (F, D) a rn valus of 4 Dividing h balancing priod ino zons according o volag rnc, and dcid h rquird maximum currn allowd hrough h capacior and h corrsponding quivaln rsisor R Sq valu This rsisor valu allows o slc a D valu and h allowabl swiching frquncy rang as illusrad in Figur 15 5 By knowing h highr and lowr cll volag, applying h corrsponding F and D along h balancing im according o h cll volags o g h maximum nrgy ransfr

16 Enrgis 013, Figur 15 SSC rsisor R Sq as a funcion h swiching frquncy and h duy cycl D 6 Th big challng of using h shuling capacior opologis wih Li-ion baris is hir narly fla volag during h discharg curvs shown in Figur 16 This is paricularly h cas for lihium iron phospha baris A 10 m rnc is narly qual 10% SoC in h fla rgion for h Li-ion baris compard wih 0 m pr 10% SoC for h lad-acid baris In addiion, on has o considr h volag drops in h swichs, so h capacior balancing will hav iculis o qualiz h clls wih a vry small volag rnc Figur 16 Diffrn Li-Ions chmisry OC-SoC curv Th soluion of his problm is don by boosing h capacior volag in h priod bwn h charging and discharging pulss (a h rs priod) o incras h capacior volag a lil highr han h high charg cll bfor conncing h capacior o h low charg cll Th capacior volag boosing can b achivd by using on small isolad dc-dc convrr (MEE3S105SC) as shown in Figur 17 Th capacior volag a h small boosing puls is

17 Enrgis 013, conrolld using a microconrollr, which conrols h small puls widh o adjus h capacior boosing volag Figur 17 SSC volag boosing opology using small isolad dc-dc convrr Figur 18 shows h capacior volag xprimnally whn applying h boosing chniqu; a h firs priod, h capacior is conncd o h highr cll (capacior charging) hn i is conncing o h small dc-dc convrr (capacior boosing) and finally h capacior is conncd o h lowr cll (capacior discharging) wih inr-bwn rs priods, and so on Figur 18 Exprimnal capacior volag charging-boos-discharging 7 Som prociv sps ar ncssary for xprimnal prooyp implmnaion: a Whn h balancing sars, and if h capacior volag is lowr han h low charg cll volag, h capacior mus b swichd firs o h lowr volag cll in ordr o prvn high capacior charging currn Anohr soluion o avoid high balancing currn can b don by

18 Enrgis 013, conrolling h duy cycl, which can asily conrol h swichd capacior balancing currn, as shown in Figur 15 b Th ohr limiaion is h uppr limi of h swiching frquncy, for rasons such as h manufacurr-rcommndd maximum opraing frquncy or h rspons im of h bary [7,8] In ohr words, how many millisconds ar ndd for h bary o rach is final volag whn applying a sp currn puls In addiion h clls impdanc will b incrasd a high frquncy, lading o mor losss and volag drops 43 Proposd SSC Balancing Simulaion Th prvious xampl of four 1 Ah lihium-ion clls is simulad wih h proposd SSC balancing sysm o valida h proposd conrol sragy Th clls iniial SoCs ar 87, 85, 78 and 76%, mans ha h highr SoC rnc is 11% or 13 Ah Figur 19 illusras h proposd singl swichd capacior balancing opology simulaion rsuls Th figur prsns h clls and h capacior volags, clls SoCs, clls currns, clls nrgis, clls nrgis summaion and h auxiliary bary nrgy As shown in Figur 19, h balancing im is narly of 33 hours Th proposd SSC has high fficincy whr during balancing i loss abou 115 mwh Th proposd SSC balancing sysm rachs balanc afr 33 hours, compar wih h normal SSC balancing sysm (34 hours) Th sysm givs an fficincy of 99% (clls nrgis a nd/clls nrgis a sar) Figur 19 Proposd singl swichd capacior balancing simulaion (op o boom) h clls and h capacior volags, clls SoCs, currns, nrgis, summaion of h clls nrgy and h auxiliary bary nrgy

19 Enrgis 013, Figur 19 Con 5 Exprimnal Prooyp and Exprimnal Rsuls This scion dscribs h xprimnal implmnaion of h proposd SSC balancing sysm and h xprimnal rsuls 51 Exprimnal Prooyp Th prooyp consiss of wo clls in sris rad 3 Ah and 33 Th SSC is usd o achiv h sysm balancing wih and wihou h proposd SSC balancing sysm Th SSC balancing conrol circuis ar simulad by using Prous/ISIS simulaion program Th simulaion using h ISIS program is h primary sp o implmn h xprimnal prooyp This simulaion modl can invsiga h proposd conrol sragy by using h microconrollr Th ISIS program also allows o gnra h circui PCB Th circui lmns markd by 1 16 will b mniond in poin 4 Th circui of can b dividd ino four pars as shown in Figur 0 In addiion, h xprimnal implmnaion of h SSC circui is shown in Figur 1 Th circui consiss of four pars which ar givn as follows: 1 Th SSC main circui including h clls conncors, h swichs marix, h capacior and h boosing circui Th firs par of h SSC circuis conains h balancing capacior sris wih currn snsing rsisor, main swichs, procion fuss and h modul s clls conncors (s Figur 17) Th bidircional swichs ar implmnd by using wo ani-sris IRFB3806PBF MOSFETs Th xprimnal ss ar prformd wih mf wih maximum ESRs of 65 mω Th isolad boosing dc/dc convrr MEE3S105SC has an inpu/oupu volag raing of 1/5 and 06 A oupu currn (3W)

20 Enrgis 013, Th swichs isolaion opocouplrs and driving circui This circui provids h isolaion bwn h conrol circui (microconrollr) and h powr circuis (swichs) Th implmnaion of h swichs isolaion drivr-circui is prformd by using TLP50 opocouplr, having a urn-on im of 05 μs On convrr for ach bidircional swich is implmnd o insur h full isolaion bwn h powr circui lmns 3 Powr supply circui, snsors (such as currn, volag mpraur snsors) Th powr circui is supplid from h auxiliary bary hrough a 781 volag rgulaor Thn wo MEE3S115SC (1/15, 3W) isolad convrrs ar implmnd o hav ±15 sourcs Th SSC balancing currn is masurd hrough of 10 mω rsisor srially conncd o h capacior Th clls volags ar masurd by using a rnial mhod A high prcision opraional amplifir OPA477PA, wih four op-amps insid, is usd for his purpos and is oupus ar conncd dircly o microconrollr s ADC Tmpraur snsor is illusrad using h hrmomr LM35DT Thy ar four conncors o masur h four clls mpraurs in h circui Th fan powr supply uilizs a 1 (781) volag rgulaor Th fan spd is conrolld by PWM oupu from h microconrollr 4 Th microconrollr circui Th microconrollr PIC18F4550, which is usd for conrolling purpos chniqu wih 0 MHz crysal An addiional high spd analog muliplxr/dmuliplxr 74HC4051, is usd for fuur analog rading Th SSC circui which is shown in Figur 1 consiss of: 1 Microconrollr PIC18F4550 ; I C inrfacing conncor; 3 I C inrfacing isolaion ADUM151 ; 4 Modul powr supply rgulaors 781 circui; 5 Auxiliary bary inpu; 6 Swichs drivr opocouplr isolaion marix TLP50 ; 7 Swichs drivr isolad convrr marix MEE3S115SC ; 8 Currn snsing op-amps LM34AN ; 9 olag snsing op-amps OPA477PA ; 10 Boosing convrr MEE3S105SC ; 11 Balancing currn snsing rsisor (10 mω); 1 Capacior conncion poins; 13 Swichs marix; 14 Procion fuss; 15 Modul s clls conncors;

21 Enrgis 013, Clls mpraur snsors conncors; 17 Analog muliplxr/dmuliplxr 74HC4051 ; 18 Cooling fan conrol circui and is conncors 11 Figur 0 SSC conrol circui global viw OPA477PA 1 3 USB RD0/SPP0 RD1/SPP1 RD/SPP RD3/SPP3 RD4/SPP4 RD5/SPP5/P1B RD6/SPP6/P1C RD7/SPP7/P1D RE0/AN5/CK1SPP RE1/AN6/CKSPP RE/AN7/OESPP RE3/MCLR/PP D D S G 1 / 15 DC CON GND_AUX 1 PWR_AUX IN - OUT- IN+ OUT+ 3 C nF OPTOCOUPLER 1 R Q R SW_1 NC1 CC O/P 3 NC3 NC GND 8 D D R4 7 45K 6 S 5 TLP50 G BC337 1K R3 QD QC 4 MEE3S115SC S RB0/AN1/INT0/FLT0/SDI/SDA RB1/AN10/INT1/SCK/SCL RB/AN8/INT/MO RB3/AN9/CCP/PO RB4/AN11/KBI0/CSSPP RB5/KBI1/PGM RB6/KBI/PGC RB7/KBI3/PGD G 18 RA0/AN0 RC0/T1OSO/T1CKI RA1/AN1 RC1/T1OSI/CCP/UOE RA/AN/REF-/CREF RC/CCP1/P1A RA3/AN3/REF+ RC4/D-/M RA4/T0CKI/C1OUT/RC RC5/D+/P RA5/AN4/SS/LDIN/COUT RC6/TX/CK RA6/OSC/CLKO RC7/RX/DT/SDO OSC1/CLKI DD QD QC PIC18F k GND Figur 1 SSC circui PCB prooyp

22 Enrgis 013, Exprimnal Rsuls Exprimnal rsuls ar obaind from wo ss, which ar carrid ou on wo sris LFP clls rad 3 Ah and 33 In hs ss, h clls ar balancd by using h SSC balancing sysm wihou and wih h proposd balancing chniqu Th wo 3 Ah clls ss hav bn ralizd according o h following condiions: 1 Two ss hav bn prformd on hs clls Th wo clls sard wih volags of 388 and 31 ( = 76 m) Th iniial SoCs of hs clls ar around 35% and 113%, rspcivly (SoC rnc is around 37% or 545 mah); Th wo ss ar prformd wih mf (maximum ESRs of 65 mω) a swiching frquncy of 588 Hz (T = 17 ms); 3 Th clls and h capacior volags ar masurd by using Fluk 177 digial mulimr wih an accuracy of ±009%; 4 Ths ss ar prformd by using opn-loop conrol I mans ha h conrollr did no masur h clls volags, i is dircly shuling h nrgy bwn h wo clls; 5 Th im of ss is around 4 hours for h balancing bwn clls, whr hr is a rs of narly 1 hours afr h firs 1 hours of balancing; 6 Firs s (no 1) is carrid ou wihou using h proposd balancing chniqu; 7 Scond s (no ) is carrid ou wih using h proposd balancing chniqu Th s has fixd boosing pulss of 40 μs; Th rsuls of s no 1 is shown in Figur and s no in Figur 3 Figur Exprimnal rsuls of 3 Ah clls wih normal SSC balancing

23 Enrgis 013, Figur 3 Exprimnal rsuls of 3 Ah clls wih proposd SSC balancing As mniond bfor, a h saring of balancing h clls volags wr 388 and 31 ( = 76 m) and h SoCs wr 35% and 113% (SoC rnc is 37% or 545 mah) and h SoC summaion was 463% (his is usd as an indicaion o h oal chargs in h clls) Tabl summarizs h prvious xprimnal sing rsuls In addiion, his abl is followd by h dscripion and h conclusions of h abov ss Figurs Ts No C (mf) Tabl Two 3 Ah clls balancing xprimnal sing rsuls using SSC F (Hz) Balancing im (h) Cll 1 () balanc Cll () Diff (m) balanc m ill 4 h h Cll 1 (%) Cll (%) Diff (%) Sum (%) Nos From Tabl i is asy o conclud h following: As can b sn in s no 1: h minimum volag rnc, which can b obaind is 4 m This volag is obaind afr 0 hours and sill consan (4 m) and rmains consan ill 4 hours of s In addiion, his Li-ion fla volag rgion givs SoC rnc around 8% according o h volag rnc (4 m) Th proposd SSC s conrol opology s no : giv h smalls volag rnc (1 m) bwn h clls wih h smalls balancing im (19 hours) This small volag rnc can

24 Enrgis 013, 6 17 ovrcom lihium iron phospha baris fla volag balancing problms Th clls rach a volag rnc of 4 m a 14 hours Comparing h wo ss wih h sam capacior valu and h swiching frquncy For h sam final volag rncs (4 m) h proposd SSC balancing sysm (scond s) rach i afr 14 hours and h normal SSC balancing (firs s) rach i afr 0 hours Tha mans h proposd SSC balancing rducs h balancing im by 30% 6 Conclusions Cll balancing is a ky ask of h bary managmn sysm I incrass bary pack lifim, h safy of h bary sysm, as wll as opimizing h whol bary pack capaciy Shuling capacior bary balancing opologis (SC, DTSC, SSC and MSC) hav bn rviwd and simulad wih h aid of MATLAB/Simulink A comparaiv sudy bwn hs opologis has bn prformd including: simulaion rsuls, circuis dscripion, implmnaions, balancing spd Th singl swichd capaciors balancing mhod has bn discussd in dail A novl conrol sragy for h SSC balancing sysm has bn proposd Th advanags of h proposd conrol sragy ar: rducing h sysm siz, cos as wll as h balancing im This is don by maximizing h nrgy ransfr bwn h cll(s) and h capacior Furhrmor, h SSC (or h shuling capacior) balancing wih h Li-ion clls fla volag problm has bn solvd Th simulaion and xprimnal rsuls prov h validiy of h xracd ransfrrd nrgy funcion, as wll as, h proposd chniqu o conrol h SSC balancing sysms Th proposd balancing sysm SSC givs good rsuls during h sysm simulaion and xprimnal ss Th proposd balancing sysm rducs h balancing im by 30% Furhrmor, i givs vry small volag rnc (1 m) Rfrncs 1 Daowd, M; Omar, N; van dn Bossch, P; van Mirlo, J A rviw of passiv and aciv bary balancing basd on MATLAB/Simulink J In Rv Elcr Eng 011, 6, Daowd, M; Omar, N; van dn Bossch, P; van Mirlo, J Passiv and Aciv Bary Balancing Comparison basd on MATLAB Simulaion In Procdings of h IEEE hicl Powr and Propulsion Confrnc (PPC), Ws Chicago, IL, USA,6 9 Spmbr 011; pp Jian, C; Schofild, N; Emadi, A Bary Balancing Mhods: A Comprhnsiv Rviw In Procdings of h IEEE hicl Powr and Propulsion Confrnc (PPC 08), Harbin, China, 3 5 Spmbr 008; pp Kong, Z-G; Zhu, C-B; Lu, R-G; Chng, S-K Comparison and Evaluaion of Charg Equalizaion Tchniqu for Sris Conncd Baris In Procdings of h 37h IEEE Powr Elcronics Spcialiss Confrnc (PESC 06), Jju, Souh Kora, 18 Jun 006; pp Moor, SW; Schnidr, PJ A Rviw of Cll Equalizaion Mhods for Lihium Ion and Lihium Polymr Bary Sysms In Procdings of h SAE 001 World Congrss, Droi, MI, USA, 5 8 March 001

25 Enrgis 013, Isaacson, MJ; Hollandsworh, RP; Giampaoli, PJ; Linkowsky, FA; Salim, A; Tofilo, L Advancd Lihium Ion Bary Chargr In Procdings of h Fifnh Annual Bary Confrnc on Applicaions and Advancs, Long Bach, CA, USA, January 000; pp Kuku, NH; Divan, DM Dynamic Equalizaion Tchniqus for Sris Bary Sacks In Procdings of h 18h Inrnaional Tlcommunicaions Enrgy Confrnc (INTELEC 96), Boson, MA, USA, 6 10 Ocobr 1996; pp Lindmark, B Individual Cll olag Equalizrs (ICE) for Rliabl Bary Prformanc In Procdings of h 13h Inrnaional Tlcommunicaions Enrgy Confrnc (INTELEC 91), Kyoo, Japan, 5 8 Novmbr 1991; pp Suar, TA; Wi, Z Fas qualizaion for larg lihium ion baris IEEE Arosp Elcron Sys Mag 009, 4, Kimball, JW; Kuhn, BT; Krin, PT Incrasd Prformanc of Bary Packs by Aciv Equalizaion In Procdings of h IEEE hicl Powr and Propulsion Confrnc (PPC 07), Arlingon, TX, USA, 9 1 Spmbr 007; pp Kobzv, GA Swichd-capacior Sysms for Bary Equalizaion In Procdings of Modrn Tchniqus and Tchnology, MTT 000, 6h Inrnaional Scinific and Pracical Confrnc of Sudns, Pos-graduas and Young Sciniss, Tomsk, Russia, 8 Fbruary 3 March, 000; pp Ws, S; Krin, PT Equalizaion of alv-rgulad Lad-acid Baris: Issus and Lif Ts Rsuls In Procdings of h Twny-scond Inrnaional Tlcommunicaions Enrgy Confrnc (INTELEC 00), Drsdn, Grmany, 7 10 May 000; pp Pascual, C; Krin, PT Swichd Capacior Sysm for Auomaic Sris Bary Equalizaion In Procdings of h Twlfh Annual Applid Powr Elcronics Confrnc and Exposiion (APEC 97), Alana, Gorgia, 3 7 Fbruary 1997; olum 84, pp Baughman, AC; Frdowsi, M Doubl-ird swichd-capacior bary charg qualizaion chniqu IEEE Trans Ind Elcron 008, 55, Baughman, A; Frdowsi, M Analysis of h Doubl-Tird Thr-Bary Swichd Capacior Bary Balancing Sysm In Procdings of h IEEE hicl Powr and Propulsion Confrnc (PPC 06), Windsor, UK, 6 8 Spmbr 006; pp Baughman, A; Frdowsi, M Doubl-ird Capaciiv Shuling Mhod for Balancing Sris-conncd Baris In Procdings of h 005 IEEE Confrnc on hicl Powr and Propulsion, Chicago, IL, USA, 7 9 Spmbr 005; pp Splino, C; Sfanopoulou, A; Fingo, G Cll Equalizaion in Bary Sacks hrough Sa of Charg Esimaion Polling In Procdings of h Amrican Conrol Confrnc (ACC 10), Balimor, MD, USA, 30 Jun July 010; pp Daowd, M; Omar, N; van dn Bossch, P; van Mirlo, J Capacior Basd Bary Balancing Sysm In Procdings of h 6h Hybrid and Ful Cll Elcric hicl Symposium (ES-6), Los Angls, CA, USA, 6 9 May 01; pp Park, HS; Kim, CH; Park, KB; Moon, GW; L, JH Dsign of a charg qualizr basd on bary modularizaion IEEE Trans h Tchnol 009, 58,

26 Enrgis 013, Al Sakka, M; Gualous, H; van Mirlo, J; Culcu, H Thrmal modling and ha managmn of suprcapacior moduls for vhicl applicaions J Powr Sourcs 009, 194, Yonghua, C; Jori, M; Laair, P; Buchl, M; Knorr, R; Gallay, R Mhod of Idnifying olag Diffrnc of Supr Capaciors and Principl of olag Balancing In Procdings of h 007 Europan Confrnc on Powr Elcronics and Applicaions, Aalborg, Dnmark, 5 Spmbr 007; pp 1 10 Daowd, M; Omar, N; van dn Bossch, P; van Mirlo, J A comparaiv sudy of bary modls paramr simaion J In Rv Elcr Eng 01, 7, Daowd, M; Omar, N; rbrugg, B; van dn Bossch, P; van Mirlo, J Bary Modls Paramr Esimaion basd on MATLAB/Simulink In Procdings of h 5h Elcric hicl Symposium (ES-5), Shnzhn, China, 5 9 Novmbr Daowd, M; Omar, N; van dn Bossch, P; van Mirlo, J Exndd PNG bary modl for lcric and hybrid vhicls J In Rv Elcr Eng 011, 6, Kimball, JW; Krin, PT Analysis and Dsign of Swichd Capacior Convrrs In Procdings of h Twnih Annual IEEE Applid Powr Elcronics Confrnc and Exposiion (APEC 05), Ausin, TX, USA, 6 10 March 005; olum 1473, pp Bn-Yaakov, S; Evzlman, M Gnric and unifid modl of Swichd Capacior Convrrs In Procdings of h IEEE Enrgy Convrsion Congrss and Exposiion (ECCE 09), San Jos, CA, USA, 0 4 Spmbr 009; pp Jossn, A Fundamnals of bary dynamics J Powr Sourcs 006, 154, K, Z; Nawrocki, S; Rnxiang, W; Jin, W High Currn Bary Impdanc Tsing for Powr Elcronics Circui Dsign In Procdings of h hicl Powr and Propulsion Confrnc, (PPC 09), Darborn, MI, USA, 7 10 Spmbr 009; pp by h auhors; licns MDPI, Basl, Swizrland This aricl is an opn accss aricl disribud undr h rms and condiions of h Craiv Commons Aribuion licns (hp://craivcommonsorg/licnss/by/30/)