Recei ed 19 No embe 2024; e ised 23 Decembe 2024; accep ed 26 Decembe 2024. Da e o publica ion 3 Janua y 2025;
da e o cu en e sion 17 Janua y 2025. The e iew o his a icle was a anged by Associa e Edi o Hani Vahedi.
Digi al Objec Iden i ie 10.1109/OJIES.2024.3525262
EV Hyb id Ba e y Wi h In eg a ed Mul ile el
Neu al-Poin -Clamped In e acing and
Lossless In e module S a e-o -Cha ge
Balancing
GABRIEL GARCIA-ROJAS 1(G adua e S uden Membe , IEEE),
SERGIO BUSQUETS-MONGE 1(Senio Membe , IEEE), ÀLBER FILBÀ-MARTÍNEZ 2, TUREV SARIKURT 3,
SALVADOR ALEPUZ 4(Senio Membe , IEEE), AND JOSEP BORDONAU 1(Membe , IEEE)
1Depa men o Elec onic Enginee ing, Uni e si a Poli ècnica de Ca alunya, 08028 Ba celona, Spain
2Ca alonia Ene gy Resea ch Ins i u e, 08930 San Ad ià del Besòs, Spain
3Rail T anspo Technologies Ins i u e, Scien i ic and Technological Resea ch Council o Tü kiye, 41400 Kocaeli, Tü kiye
4TecnoCampus Ma a ó-Ma esme, Uni e si a Pompeu Fab a, 08302 Ma a ó, Spain
CORRESPONDING AUTHOR: GABRIEL GARCIA-ROJAS (e-mail: [email p o ec ed]).
This wo k was suppo ed by Eu opean Union’s Ho izon 2020 esea ch and inno a ion p og am unde G an 963646.
ABSTRACT The ba e y is a he hea o he elec ic ehicle and de e mines many o i s key pe o mance
ea u es. The e o e, an op imized design o he ba e y is c i ical. On he one hand, he design o ba e ies
based on a single ba e y cell leads in many cases o o e sized ba e ies in e ms o ene gy o powe , due o
he di e si y o equi emen s o he di e en elec ic ehicles. On he o he hand, he use o a cus om cell o
each ehicle, op imized o i s pa icula equi emen s, is no economically iable. Ins ead, hyb id ba e ies,
combining only wo ba e y cell chemis ies, wi h dis inc pa icula s eng hs, such as high speci ic ene gy
o high speci ic powe , o e an oppo uni y o co e a wide ange o ehicle ba e y speci ica ions while
a oiding o e sizing and dispe sion in he cells o be employed. This wo k in oduces a no el hyb id ba e y
con igu a ion, whe e he in e acing be ween he wo se s o cells is accomplished h ough a bidi ec ional
mul ile el neu al-poin -clamped dc–dc con e e . The no el opology is p esen ed, and a sui able powe
con e e modula ion and con ol s a egy is de eloped. The easibili y and bene i s o such con igu a ion
a e demons a ed and illus a ed. Pa icula ly, he p oposed ba e y sys em allows he balancing o he
S a e-o -Cha ge (SoC) o he ba e y modules wi hin bo h he se s o ba e y banks, which is achie ed wi hou
in oducing addi ional powe losses. The SoC balancing is simply accomplished h ough he egula ion o he
powe o be ex ac ed/deli e ed om/ o each ba e y module by he powe con e e du ing egula ba e y
discha ging and cha ging ope a ions. The con e e ea u es enough egula ion ma gin o co ec subs an ial
SoC imbalances. O e all, he p oposed app oach enables a modula and scalable design o he ene gy s o age
sys em o a wide ange o elec ic ehicles, om only wo di e en s anda d ba e y modules and a s anda d
powe semiconduc o de ice, while op imizing he ba e y size o any gi en ba e y powe and ene gy
speci ica ion. Simula ion and expe imen al esul s a e p o ided in he case o a h ee-le el in e nal ba e y
in e acing o e i y he good pe o mance o he p oposed no el hyb id ba e y con igu a ion, modula ion,
and con ol.
INDEX TERMS Hyb id ba e y, modula ion, mul ile el, neu al poin clamped (NPC), S a e-o -Cha ge (SoC)
balancing.
© 2025 The Au ho s. This wo k is licensed unde a C ea i e Commons A ibu ion 4.0 License. Fo mo e in o ma ion, see h ps://c ea i ecommons.o g/licenses/by/4.0/
130 VOLUME 6, 2025
NOMENCLATURE
Cbk Tank dc-blocking capaci o alue.
E∗
ba Ene gy equi emen o he ba e y.
sSwi ching equency.
i2a Cu en lowing h ough he dc-link
node 2 o side A.
I2a A e age cu en lowing h ough he dc-
link node 2 o side A.
iA1,iA2 Cu en s lowing h ough he ba e y
modules A1 and A2 and hei pa allel
capaci o s, espec i ely.
IA1,IA2 A e age cu en s lowing h ough he
ba e y modules A1, A2 and hei pa al-
lel capaci o s, espec i ely.
iTTank cu en .
ITRMS alue o he ank cu en .
iT,1Fundamen al componen o he ank
cu en .
ip
T,1In-phase and componen o iT,1.
iq
T,1In-quad a u e componen o iT,1 .
ka,kbCon ol e o o he s a e-o -cha ge
closed-loop con ol o sides A and B,
espec i ely.
LTTank induc ance.
ma,mbModula ion index o sides A and B,
espec i ely.
na,nbNumbe o le els o sides A and B,
espec i ely.
Pa,PbAc i e powe deli e ed by sides A and
B, espec i ely.
P∗
ba Powe equi emen o he ba e y.
Qa,QbReac i e powe deli e ed by sides A and
B, espec i ely.
q( ) S o ed ba e y module cha ge a ime .
Qnom Nominal ba e y module capaci y.
RLLoad esis ance.
RTTank esis ance.
sa,sbNPC leg connec ion s a e o sides A and
B, espec i ely.
spa,spbSign o he ac i e powe deli e ed by
sides A and B, espec i ely.
sqa,sqbSign o he eac i e powe deli e ed by
sides A and B, espec i ely.
scA1,scA2 S a e o cha ge o ba e y modules A1
and A2, espec i ely.
scB1,scB2 S a e o cha ge o ba e y modules B1
and B2, espec i ely.
scimbA,scimbBS a e o cha ge imbalance o sides A and
B, espec i ely.
scimbA∗,scimbB∗Command o he s a e o cha ge imbal-
ance o sides A and B, espec i ely.
a, bSyn he ized ins an aneous ou pu ol -
age o sides A and B, espec i ely.
Va,VbRMS alue o he undamen al compo-
nen o aand b, espec i ely.
VA1,VA2 A1 and A2 ba e y module ol ages, e-
spec i ely.
Vdca,Vdcb To al dc ol age o sides A and B, e-
spec i ely.
TTank ci cui ol age.
αjModula ion pa e n swi ching angles,
whe e j=a, b, c, d.
βPhase shi o he undamen al compo-
nen o he cu en lowing h ough he
ank, IT, 1, wi h espec o he undamen-
al ou pu ol age o side B.
θa,θ
bModula ion angle o sides A and B,
espec i ely.
ϕPhase shi o he undamen al ou pu
ol age o side A, wi h espec o he
undamen al ou pu ol age o side B.
I. INTRODUCTION
Elec ic ehicles (EVs) a e al eady playing an essen ial ole in
he ansi ion owa d a low-ca bon global economy. Suppo ed
by he a ious ini ia i es o coun ies and ins i u ions [1],[2],
i is an icipa ed ha he numbe o EVs will con inue o g ow
in he coming yea s.
Simila o in e nal combus ion engine ehicles, he e is
a wide a ie y o EVs, anging om small commu e ca s
o hea y-du y comme cial ehicles. These EVs can g ea ly
di e in hei ba e y equi emen s, including ene gy, powe
[3], cha ging ime [4], egene a i e b aking capaci y, cos ,
and li espan. In addi ion, hese EV ba e y equi emen s mus
be me unde di e en ope a ing condi ions, such as a ying
S a es o Cha ge (SoCs) and ex eme empe a u es. Since i
is no iable o build he ba e y o each ehicle a ound an
op imal ba e y cell designed speci ically o his ehicle, he
EV ba e y pack designs based on a single s anda d ba e y
cell end up o en being o e sized in some aspec s [5],[6].
Ins ead, a hyb id ba e y ene gy s o age sys em (HBESS)
is buil om a combina ion o wo ypes o ba e y cells,
each one ea u ing di e en chemis ies, wi h he in en ion o
inding a mo e op imal solu ion. Each ba e y cell echnology
ea u es a pa icula s eng h, such as high speci ic ene gy
(SE) o high speci ic powe (SP), and he hyb id ba e y akes
ad an age o his combina ion o s eng hs o mee all he
sys em equi emen s wi h less ba e y olume and weigh ,
and ex ending ba e y li e. This is illus a ed in he ollowing
h ough a simple example.
Le us assume ha in he design o a ba e y, SE and SP a e
o u mos impo ance. Le us also assume ha only wo cell
ypes a e a ailable, depic ed in Fig. 1. Cell ype A is op imized
o s o e ene gy and in con as p esen s a mode a e SP. Cell
ype B is op imized o p o ide powe bu p esen s a mode a e
SE.
Fig. 2illus a es he ene gy (E) and powe (P) achie ed wi h
1 kg o each cell. Thus, he leng hs o he blue and ed lines,
which a e in his example app oxima ely equal, co espond
o 1 kg o each cell ype. When a high-ene gy low-powe
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FIGURE 1. Cha ac e is ics o cells A and B.
FIGURE 2. Powe and ene gy o 1 kg o cells A and B.
ba e y is o be designed, wi h he equi emen s depic ed by
poin 1in Fig. 3(a), whe e E∗
ba ep esen s he minimum
equi ed ba e y ene gy and P∗
ba ep esen s he minimum e-
qui ed ba e y powe , hen i will be op imal o use cell ype
A. As can be obse ed in Fig. 3(a), using cell ype A leads o
a lowe ba e y weigh , since he blue line is sho e han he
ed line. Con e sely, when a high-powe low-ene gy ba e y is
o be designed, wi h he equi emen s depic ed by poin 2in
Fig. 3(b), he op imal cell o use will be cell B, as shown in
Fig. 3(b).
Howe e , when a ba e y wi h a mo e balanced ene gy and
powe equi emen s is needed, such as he one ep esen ed by
poin 3in Fig. 3(c), bo h cell ypes, i used alone, lead o a
hea y ba e y, as depic ed in Fig. 3(c). In his case, ins ead,
a combina ion o bo h cells allows ul illing he ba e y e-
qui emen s wi h a much lowe o e all weigh , as shown in
Fig. 3(d). The e o e, hyb id ba e ies o e he possibili y o
ob aining ba e ies wi h di e en a ios o ene gy and powe
in an op imal way. F om a di e en pe spec i e, hyb idiza ion
is equi alen o employing a i ual cell wi h cha ac e is ics a
any selec ed in e media e poin along he s aigh line joining
cells A and B in Fig. 1.
Some examples in he li e a u e p opose he hyb idiza ion
o di e en ene gy s o age sys ems a cell le el [7] and a
sys em le el [6],[8],[9],[10]. F om he a chi ec u al poin
o iew, wo op ions a e conside ed: passi e and ac i e sys-
ems. Passi e sys ems do no con ain any powe con e e
o in e ace he s o age elemen s, he eby lowe ing he o al
sys em cos bu imposing signi ican es ic ions, such as cell
ol age cu e compa ibili y [11],[12]. Al e na i ely, in ac i e
sys ems, he inclusion o a powe con e e in e ace inc eases
he deg ees o eedom o he sys em. The in e ace o he
s o age elemen s has been epo ed o be implemen ed h ough
a single wo-le el powe con e e [9],[13],[14],[15],[16],a
con e e o each elemen [3],[17],[18], a h ee-le el h ee-
phase neu al-poin -clamped (NPC) dc–ac con e e [19],a
cascaded H-b idge (CHB) con e e [10],[20],[21],[22],
[23], o o he con e e s [24],[25],[26].
The use o mul ile el con e e s ed by se e al ba e y mod-
ules allows con olling he cu en o each ba e y module as
a unc ion o i s indi idual SoC, which maximizes he ene gy
deli e ed by he ull ba e y pack [23],[27]. The e o e, hese
con e e s a e well sui ed o he in e acing in ac i e hyb id
ba e y sys ems. Howe e , hei applica ion has no been ully
explo ed ou side he CHB-based HBESS [10],[20],[21],[22],
[23], and he con igu a ion o hyb id ba e ies using o he mul-
ile el opologies s ill equi es u he in es iga ion. In o de
o co e his gap, his a icle, de eloped unde he Eu opean
Union’s Ho izon 2020 Helios p ojec [28], wi h a conso ium
o 18 pa ne s, p oposes a no el ac i e hyb id ba e y con-
igu a ion employing a no el NPC mul ile el con e e as he
in e ace be ween he wo ba e y banks, wi h one o he banks
being di ec ly connec ed o he load.
Compa ed o he exis ing S a e-o - he-A HBESS con igu-
a ions, he p oposed design le e ages he ad an ages o NPC
con e e opologies, such as he po en ial o he highes
powe densi y among mul ile el opologies and he educed
numbe o passi e componen s. When he con e e legs a e
implemen ed wi h he ac i e NPC opology, all he semicon-
duc o de ices ea u e he same ol age a ing [29]. Compa ed
o HBESS opologies employing wo-le el con e e s, he
p oposed sys em ea u es in e module nondissipa i e SoC bal-
ancing capabili y. Compa ed o CHB-con e e -based opolo-
gies, whe e each ba e y module mus be isola ed [10],
he p oposed HBESS con igu a ion in e connec s he ba e y
modules in se ies. This poin is pa icula ly impo an in EV
applica ions, whe e space cons ain s and high-powe -densi y
equi emen s end o a o opologies wi h educed isola ion
and clea ance dis ances.
Fu he mo e, he p oposed ci cui opology is simple and
only equi es wo NPC legs, an induc o , and a capaci o ,
he eby acili a ing i s implemen a ion and scalabili y employ-
ing s anda d ba e y modules and a s anda d semiconduc o
de ice. Finally, i is assumed ha he ba e y bank ha di ec ly
connec s o he load employs high-powe ba e y cells, while
he o he side u ilizes high-ene gy ba e y cells. The powe ex-
changed be ween bo h ba e y banks h ough he con e e is
limi ed by he high-ene gy low-powe ba e y bank. Thus, he
132 VOLUME 6, 2025
FIGURE 3. Di e en ba e y designs mee ing he ba e y ene gy and powe speci ica ions (E∗
ba and P∗
ba ). (a) High-ene gy ba e y. (b) High-powe ba e y.
(c) Ba e y wi h balanced powe and ene gy speci ica ion. (d) Hyb id ba e y wi h balanced powe and ene gy speci ica ion.
FIGURE 4. P oposed gene alized HBESS opology wi h nale els on ba e y side A and nble els on ba e y side B.
con e e powe a ing is no equi ed o be sized acco ding o
he o al powe o he HBESS.
These cha ac e is ics make he implemen a ion o ac i e
HBESS pa icula ly ele an o he s anda diza ion o ehi-
cle design and manu ac u ing, ega dless o he ba e y cell
echnologies employed. As depic ed in Fig. 1, he p oposed
app oach, by using only wo di e en ba e y cell chemis ies,
allows he concep ion o a i ual ba e y cell wi h in e medi-
a e pe o mance, which can be easily cus omized wi h ailo ed
powe and ange, and wi h ele an ba e y weigh educ ion.
EVs a e subjec ed o equen s ong accele a ions and decel-
e a ions, equi ing a signi ican amoun o powe du ing his
ansien ope a ion. High-powe ba e y cells handle his kind
o load mo e e icien ly han high-ene gy ba e y cells, gene -
a ing less hea and p o iding a longe li e cycle [30].On he
o he hand, high-ene gy ba e y cells can p o ide inc eased
ange mo e e icien ly.
The main con ibu ions o his a icle a e as ollows:
1) he concep ion o he opology, basic ope a ion, and
powe low con ol o a no el n-le el ac i e HBESS
opology;
2) he de elopmen o a ba e y in e module SoC bal-
ance con ol h ough a modi ica ion o he con e e
modula ion and wi hou in oducing addi ional losses;
ha is, he SoC balance i sel p esen s a lossless ope a-
ion;
3) he e i ica ion o he sui abili y o he p oposed opol-
ogy and con ol h ough simula ion and expe imen s.
The es o his a icle is o ganized as ollows. Sec ion II
p oposes he NPC-based ac i e HBESS opology and ope a -
ing p inciple. Sec ion III p esen s he p oposed modula ion
and cha ge balancing con ol. Sec ions IV and Vp esen
simula ion and expe imen al esul s o e i y he good pe o -
mance o he a o emen ioned sys ems, espec i ely. Finally,
Sec ion VI concludes his a icle.
II. PROPOSED HBESS TOPOLOGY AND OPERATING
PRINCIPLE
The p oposed gene alized HBESS opology is p esen ed in
Fig. 4. I is o med by wo ba e y banks. Ba e y bank A
consis s o na−1 modules connec ed in se ies, and ba e y
bank B consis s o nb−1 modules connec ed in se ies, each
one coupled wi h a pa allel capaci o C. The load is di ec ly
ed om ba e y bank B, while ba e y bank A is connec ed
o ba e y bank B h ough a powe elec onics in e acing
consis ing o wo NPC legs and a ank ci cui . The NPC
legs a e he e modeled as single-pole mul iple- h ow swi ches,
wi h na h ows on side A and nb h ows on side B. Fig. 5
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GARCIA-ROJAS ET AL.: EV HYBRID BATTERY WITH INTEGRATED MULTILEVEL NPC INTERFACING AND LOSSLESS SOC BALANCING
FIGURE 5. Some examples o NPC leg opologies. (a) Th ee-le el diode-clamped opology. (b) Th ee-le el ac i e-clamped opology. (c) Th ee-le els T- ype
opology.
FIGURE 6. Two possible hyb id ba e y pack con igu a ions depending on he connec ion o he ank cu en e u n pa h. (a) Pa allel. (b) Se ies.
shows some possible implemen a ions o such NPC legs o
he pa icula case o h ee le els. The ank ci cui consis s o
an induc o LTand a capaci o Cbk. The capaci o Cbk blocks
he dc componen o he ank ol age T. Thus, only ac cu en
lows h ough he ank in he s eady s a e. The e u n pa h o
he ank cu en iTis indica ed by he g ound symbols on he
middle dc-link poin in bo h he ba e y banks, as shown in
Fig. 4. Howe e , no ice ha he e u n pa h can be connec ed
o any dc-link poin on bo h he sides, and hese wo dc-link
poin s can di e . The loca ion o hese poin s only a ec s he
alue o he dc ol age on Cbk. This ea u e enables di e en
hyb id ba e y pack con igu a ion op ions, as hose illus a ed
in Fig. 6.Figs.4and 6(a) co espond o he pa allel con igu a-
ion, whe e he e u n pa h would be ypically connec ed o an
analogous dc-link poin on bo h he sides. Ins ead, Fig. 6(b)
co esponds o a se ies connec ion, whe e he e u n pa h is
connec ed o he bo om dc-link poin in side A and o he
op dc-link poin in ba e y bank B. This las con igu a ion
p o ides highe load ol age. The discussion abou he me i s
o each con igu a ion is beyond he scope o his a icle. This
wo k is de eloped wi h he pa allel con igu a ion o Figs. 4
and 6(a).
The powe low be ween sides A and B is con olled by
means o he ol ages aand bgene a ed by he NPC
FIGURE 7. Phaso diag am illus a ing he sys em ope a ing p inciple.
legs, wi h undamen al componen s o ms alue Vaand Vb,
espec i ely, phase shi ed by ϕdeg ees. The co esponding
phaso s a e ep esen ed in Fig. 7. The ank ms ol age VT,
compu ed as he di e ence be ween Vaand Vb, is essen ially
applied o e he induc o impedance, gene a ing he ank cu -
en wi h ms alue ITand phase β.
The syn hesized ol ages and he ank cu en de ine he
ac i e and eac i e powe exchanged be ween A and B. The
134 VOLUME 6, 2025
FIGURE 8. No malized ac i e and eac i e powe as a unc ion o ϕ, o Va
=Vb.
ac i e powe ans e ed om A o B is
Pa=−Pb=Va·IT·cos (β−ϕ)=Va·Vb·sin (ϕ)
ωL(1)
while he eac i e powe deli e ed om side A can be
compu ed as
Qa=Va·IT·sin (β−ϕ)=V2
a−VaVb·cos (ϕ)
ωL(2)
and he eac i e powe om side B can be exp essed as
Qb=−Vb·IT·sin (β)=−V2
b−VbVa·cos (ϕ)
ωL.(3)
The eac i e powe ep esen s he ene gy ha lows back
and o h be ween he ba e ies and he ank wi hou ne ene gy
ans e .
Fig. 8shows he no malized ac i e and eac i e powe as a
unc ion o ϕ, o he pa icula case Va=Vb. Fo a gi en am-
pli ude Vaand Vb, he ac i e powe can be egula ed adjus ing
he phase shi ϕbe ween −π/2 and π/2. Pu e eac i e powe
wi h no ac i e powe can be exchanged i VaࣔVband ϕ=0,
o i ϕ=π.
The ac i e powe low discussed in his sec ion is illus a ed
in Fig. 9 o he pa icula case o h ee le els on bo h he
ba e y sides. The mul ile el dc–dc con e e ex ac s ac i e
powe PA1 and PA2 om he side-A ba e y modules and
deli e s he agg ega ed powe Pa=PA1 +PA2 o he side B:
PX1 owa d module B1 and PX2 owa d module B2. Finally,
a load consuming PLis ed om he side-B ba e y bank.
In pa icula , Fig. 9illus a es he case whe e PA1 =PA2
=PX1 =PX2 =PL/4, which co esponds o an ope a ing
mode unde balanced con ibu ion o powe o he load om
each ba e y bank and balanced SoC condi ions. In gene al,
wi h he p oposed ope a ion p inciple, he sys em can adjus
he amoun o ene gy ans e ed om side-A ba e y bank o
side B.
FIGURE 9. Powe low ac oss an HBESS wi h wo ba e y modules on each
side (na=nb=3) eeding a load, unde balanced con ibu ion o powe o
he load om each ba e y bank and balanced SoC condi ions.
The ope a ion o he NPC legs demands high- equency
pulsa ing cu en s on he ba e y–capaci o pai s. The pu -
pose o he pa allel capaci o s is o p o ide a low-impedance
pa h o hese high- equency componen s, so ha he ba e y
modules supply only he dc componen . Howe e , he e is a
design adeo in he selec ion o his capaci ance. A mini-
mum capaci ance alue is necessa y o p o ide he con e e
leg commu a ion cu en s h ough a pa h wi h a low leakage
induc ance. As he capaci ance is inc eased abo e his min-
imum alue, he high- equency cu en ipple h ough he
ba e y modules is educed, a he expense o inc easing he
capaci o size. Gi en his, o selec a sui able design adeo
solu ion, i is impo an o assess he po en ial nega i e impac
o a high- equency cu en ipple on a ba e y module. Fi s ,
his cu en ipple con ibu es o inc ease he ba e y ms cu -
en o a gi en powe deli e y, leading o an inc ease in he
ba e y losses due o he Joule e ec , which in u n aises he
cell empe a u e and accele a es aging [31],[32]. Acco ding
o his, se e al s udies ha e p oposed al e na i es o minimize
he ba e y ms cu en on mul ile el opologies [33],[34].
Howe e , expe imen al s udies ha e ound no e idence o
demons a e a measu able inc ease in aging caused by he
high- equency cu en ipple on di e en cell chemis ies.
Uno and Tanaka [35] ound no signi ican di e ence in aging
o LiNiCoO2/g aphi e cells when exposed o high- equency
sinusoidal cu en s, and only lowe equencies caused accel-
e a ed aging. B and e al. [36] epo ed analogous indings
on NiMnCoO2/g aphi e cells. Mo e ecen ly, Ghassemi e al.
[37] ha e also concluded ha high- equency ac cu en s su-
pe imposed on a dc o se do no con ibu e o ageing on
LiFePO4cells. One explana ion o his phenomenon may be
ha he high- equency cu en s low h ough he double-laye
capaci ance o he cells, simila in s uc u e and beha io
o a supe capaci o , p e en ing any cha ge- ans e p ocess,
al hough hey can cause a mino inc ease in empe a u e.
Chang e al. [38] s a ed ha he necessa y condi ion o a
cu en ipple o cause ba e y deg ada ion is ha i should
ea u e low equency and ha i should cause he ba e y
cu en o change di ec ion. This hesis is u he ein o ced by
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GARCIA-ROJAS ET AL.: EV HYBRID BATTERY WITH INTEGRATED MULTILEVEL NPC INTERFACING AND LOSSLESS SOC BALANCING
FIGURE 10. Example cu en p o ile o he ba e y A1 wi hou pa allel
capaci o , unde a h ee-le el sys em (na=nb=3), ma=0.9, mb=0.9,
and ϕ=45°.
se e al s udies showing inc eased aging when his condi ion
is me [35],[39]. In addi ion, he cell empe a u e has o be
signi ican ly a ec ed. When he cell empe a u e is igh ly
con olled, Bessman e al. [40] we e no able o ind any
measu able di e ence in capaci y ade o inc ease in in e nal
esis ance, in his case o LiNiMnCoO2/g aphi e cells.
Fig. 10 shows an example p o ile o he A1 ba e y module
cu en , iA1, in he absence o a pa allel capaci o , du ing a
discha ge p ocess o ba e y A1, o he sys em p oposed in
Fig. 4a h ee le els, side-A modula ion index ma=0.9,
side-B modula ion index mb=0.9, and phase shi ϕ=45°.
Unde hese ope a ing condi ions, he ac i e powe is much
highe han he eac i e powe , and i can be obse ed ha
he cu en does no change di ec ion a any ins an o ime.
Fu he mo e, he cu en p o ile o any alue o he mod-
ula ion index and phase shi only con ains high- equency
ha monics. The equency spec um is shown in Fig. 11.E en
hough he cu en may change di ec ion when he sys em
ope a es wi h la ge eac i e alues, he condi ions epo ed in
[38] a e no me , and only a small inc ease in empe a u e is
expec ed. In addi ion, he loss o o al ba e y bank capaci y
due o di e en module aging (possibly gene a ed by di e en
empe a u e s ess) can be signi ican ly minimized hanks o
an in e module SoC balancing con ol [38]. Du ing cha ging,
he po en ial nega i e e ec s a e e en less conce ning, as
se e al au ho s ha e ound ha pulse cha ging can educe age-
ing compa ed wi h cons an cu en cha ging [37],[41],[42],
[43],[44].
III. MODULATION AND SOC BALANCING CONTROL
This sec ion p esen s he NPC leg modula ion and he ba e y
in e module SoC balancing. To help he eade unde s and he
p oposed ope a ion, his wo k has been de eloped wi h he
simples case, using a h ee-le el NPC leg on bo h he sides.
Howe e , i is impo an o highligh ha he me hod desc ibed
FIGURE 11. F equency spec um o he cu en deli e ed by ba e y A1
wi hou a pa allel capaci o , unde a h ee-le el sys em (na=nb=3), ma
=0.9, mb=0.9, and ϕ=45°.
he e can be p ope ly ex ended o any numbe o le els. Fig. 12
p esen s his simple case de i ed om he gene al opology,
wi h wo se ies-connec ed ba e y modules pe side in e aced
h ough a h ee-le el con e e , which is he e implemen ed
wi h he ac i e NPC opology. Fig. 12 p o ides addi ional
in o ma ion necessa y o he simula ion and expe imen al
sec ions ha will be de ailed in Sec ions IV and V.
Fo he sake o simplici y, he analysis is ca ied ou on
side A in Fig. 12, al hough he analysis on side B is ully
equi alen .
Fig. 13 p esen s he ol age pa e n a o be gene a ed
h ough he ope a ion o he NPC leg. Typically, αa=αb=αc
=αd=α o o ce qua e -wa e symme y, elimina ing e en-
o de ha monics and p o iding wa e o m simplici y. In his
case, he ms alue o he undamen al componen depends on
αas ollows:
Va=√2Vdca
π·sin (α)(4)
whe e Vdca =VA1 +VA2 is he o al side-A dc-link ol age.
Likewise, he modula ion index can hen be de ined as
ma=Va
Vdca/√6=2√3
π·sin (α)(5)
whe e he modula ion index a ies om 0 o 2√3/π ≈1.1
o α a ying om 0 o π/2.
Le us now analyze he e ec o he NPC leg ope a ion on
he ba e y cu en balance. F om Fig. 12, applying Ki chho
cu en law a dc-link node 2, one has
i2a −iT=iA1 −iA2 (6)
whe e iAx(xࢠ{1, 2}) is he addi ion o he cu en ha lows
h ough he ba e y (iAx,ba ) and he capaci o (iAx,cap).
136 VOLUME 6, 2025
FIGURE 12. HBESS ci cui schema ic wi h h ee le els on ba e y side A and h ee le els on ba e y side B (na=nb=3). Bo h he con e e legs a e
implemen ed wi h he ac i e NPC opology. Bo h he simula ions and he ha dwa e p o o ype ollow his design.
FIGURE 13. Th ee-le el modula ion pa e n [45].
On a e age, o e he swi ching cycle, one has
I2a =IA1 −IA2 (7)
which indica es ha he a e age neu al-poin cu en I2a is
esponsible o he imbalance o he wo ba e y cu en s; ha
is, o cing I2a =0 keeps he wo ba e y cu en s balanced.
Fig. 13 includes he plo o he undamen al componen o
he ank cu en iT,1=ip
T,1+iq
T,1, decomposed in o a com-
ponen in phase wi h he undamen al componen o a(ip
T,1,
esponsible o he ac i e powe ans e ) and a componen in
quad a u e (iq
T,1, esponsible o he eac i e powe ans e ).
All he o he ha monics o iTa e neglec ed.
In Fig. 13, wi h αa=αb=αc=αd=α, he blue and g een
solid a eas, ep esen ing he cha ge d awn om (posi i e a -
eas) o injec ed in o (nega i e a eas) he neu al poin , cancel
ou in bo h ipT,1 and iqT,1. This esul s in I2a =0, and i means
ha bo h he ba e y modules ea u e he same cu en , ideal
o a balanced cha ging and discha ging o hese wo ba e y
modules.
Howe e , i can be use ul o in oduce an imbalance in he
ba e y cu en s. Fo ins ance, his imbalance can be applied o
equalize he wo ba e y modules SoCs when hey a e unequal.
This can be done by modi ying he wid h and/o posi ion
o he posi i e and nega i e pulses o ain co ela ion wi h
ip
T,1and/o iq
T,1. An example is depic ed in Fig. 14(a), whe e
he wid h o he posi i e and nega i e pulses is educed and
inc eased, espec i ely. The g een a eas s ill cancel ou in iq
T,1,
bu hey no longe cancel ou in ip
T,1, esul ing in a posi i e
a e age neu al-poin cu en I2a >0 and imbalanced ba e y
module cu en s IA1 >IA2.
In Fig. 14(b), he posi ion o he posi i e and nega i e
pulses is mo ed igh and le , espec i ely. The blue a eas
s ill cancel ou in ip
T,1, bu hey no longe cancel ou in iq
T,1,
in oducing an I2a >0 ha will o ce IA1 >IA2.
Tha is, he imbalance o he ba e y cu en s can be con-
olled h ough he ank cu en associa ed o he ac i e and
eac i e powe being ans e ed, by modi ying he wid h
and/o posi ion o he posi i e and nega i e pulses o a.
Fig. 15 shows a p ope closed-loop con ol diag am based
on his p inciple, whe e scimbA=scA1 −scA2 is he imbal-
ance be ween he SoC o ba e y module 1 and ba e y module
2o sideA,sc( )=q( )/Qnom,q( ) is he s o ed ba e y module
cha ge a ime ,Qnom is i s nominal capaci y, scimb∗
Ais he
command o he SoC imbalance o side A, and sa( )ࢠ{1,2,3}
is a a iable ha indica es he dc-link poin whe e he NPC
leg is connec ed a each poin in ime. A p opo ional gain
in he con olle Gc(s) is su icien o a success ul sys em
implemen a ion.
To de e mine sain he modula o block o Fig. 15,i is
equi ed o i s de e mine he swi ching angles wi h
αa=α·1+ka·(spa+sqa)
αb=α·1+ka·(spa−sqa)
αc=α·1+ka·(−spa−sqa)
αd=α·1+ka·(−spa+sqa)
(8)
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GARCIA-ROJAS ET AL.: EV HYBRID BATTERY WITH INTEGRATED MULTILEVEL NPC INTERFACING AND LOSSLESS SOC BALANCING
FIGURE 14. Con ol ac ion o co ec imbalance. (a) Th ough he in-phase
cu en componen (ac i e powe ). (b) Th ough he in-quad a u e cu en
componen ( eac i e powe ).
whe e αcan be ob ained om (5),spais he sign o he ac i e
powe deli e ed by side A (+1i ip
T,1is as depic ed in Fig. 13
and −1 i i is phase shi ed by 180°), sqais he sign o he
eac i e powe (+1i iq
T,1is as depic ed in Fig. 13 and −1i i
is phase shi ed by 180°), and kais he con ol e o a iable.
I i is desi ed o es ic he con ol ac ion only o he ac i e
powe , sqahas o be se o ze o in (8). Al e na i ely, i i is
desi ed o es ic he con ol ac ion only o he eac i e powe ,
spahas o be se o ze o in (8). The alue o he con ol e o
a iable kamay need o be es ic ed o p e en he swi ching
angles om going ou side he easible ange [0, π/2].
Fig. 16 illus a es he powe low in he HBESS unde
his SoC balancing con ol in ac ion. I is assumed ha
scimbA<0 and scimbB>0. The powe deli e ed om side-A
ba e y modules, PA1 and PA2, is unbalanced due o he con-
ol ac ion on he con e e side-A modula ion. Simila ly, he
ene gy deli e ed om he con e e o side-B ba e y modules,
PX1 and PX2, is also unbalanced due o he con ol ac ion on
he con e e side-B modula ion. The SoCs o all he ba e y
modules a e egula ed simply h ough he con ol o he indi-
idual powe deli e ed/ ecei ed by each ba e y module.
I is e y ele an o highligh ha since he p oposed cha ge
balancing con ol does no in oduce any addi ional commu a-
ions and since he e is no cha ge ans e among modules o
he same ba e y bank—all he cha ge ans e ed is di ec ly
deli e ed om one ba e y bank o he o he —no addi ional
losses a e in oduced due o his cha ge balancing con ol.
The e o e, he sys em can balance each indi idual ba e y
module SoC in a lossless manne .
Fig. 17 illus a es his SoC lossless balancing con ol in
compa ison o he ypical passi e balancing con ol and ac-
i e balancing con ols. Two ba e y modules connec ed in
se ies a e conside ed (Ba 1 and Ba 2). Thei cha ge/ene gy
is ep esen ed by a solid ba . The ene gy o he wo ba e y
modules is ini ially unbalanced. In Fig. 17(a), a passi e bal-
ancing ci cui bu ns he excess ene gy o Ba 1 o achie e SoC
balance. This excess ene gy is, he e o e, los . In Fig. 17(b),
an ac i e balancing ci cui deli e s pa o he excess ene gy
o Ba 1 o Ba 2 o achie e SoC balance. Howe e , he ac i e
balancing ci cui s incu in some losses. The e o e, pa o he
ene gy is los in a powe ans e exclusi ely unde aken o
achie e SoC balance. Finally, in Fig. 17(c), he balancing is
simply achie ed by p ope ly adjus ing he powe deli e ed by
Ba 1 and Ba 2 o he load, o al e na i ely adjus ing he powe
ecei ed by Ba 1 and Ba 2 om a sou ce. This powe ans e
will ob iously incu in some losses, bu since he same o e all
powe ans e has o be p oduced o powe he load o o
cha ge he ba e y bank, hese losses would occu anyway and
canno be a ibu ed o he SoC balancing p ocess i sel . Thus,
his hi d balancing echnique is ega ded as being lossless.
In addi ion, ano he ad an age is ha i does no equi e a
speci ic balancing ci cui .
IV. SIMULATION RESULTS
A swi ching model and a swi ching-cycle-a e aged model o
he sys em depic ed in Fig. 12 ha e been implemen ed in
MATLAB-Simulink o analyze he pe o mance o he p o-
posed HBESS sys em. Fo con enience and simplici y, he
same ba e y module is used in sides A and B. The selec ed
ba e y module model has been ob ained om [27]. The con-
e e legs a e modeled as ideal single-pole mul iple- h ow
swi ches. The load is modeled as a esis o wi h alue RL.
The sys em pa ame e s and ope a ing condi ions p esen ed in
Tables 1and 2a e he same o bo h he simula ions and he
expe imen al es s.
The sys em ope a es wi h wo ba e y modules and one
h ee-le el leg on each side (na=nb=3). Fo he sake o
simplici y and due o symme y, only side-A a iables a e
epo ed.
In he i s es , he swi ching model is employed o e i y
he wo king p inciple in de ail, as shown in Fig. 18 unde
open-loop con ol, i.e., o cing ka=0. No ice ha kais he
con ol e o a iable o side A. The syn he ized ol ages
aand ba e phase shi ed by 90°, leading o an ope a ion
138 VOLUME 6, 2025
