DC-bus ene gy managemen o a
con e e -in e aced enewable ene gy sou ce
comp ising an ene gy s o age sys em
F ancisco Jes´
us Ma as-D´
ıaz
Depa men o Elec ical Enginee ing
Uni e sidad de Se illa
Se illa, Spain
[email p o ec ed]
Ume Mush aq
Elec ical Eng., Ma hs. & Comp. Science
Del Uni e si y o Technology
Del , The Ne he lands
[email p o ec ed]
And ei Mihai G oss
Depa men o Elec ical Enginee ing
Uni e sidad de Se illa
Se illa, Spain
[email p o ec ed]
Al a o Rod ´
ıguez del Nozal
Depa men o Elec ical Enginee ing
Uni e sidad de Se illa
Se illa, Spain
[email p o ec ed]
Milos C e ko ic
Elec ical Eng., Ma hs. & Comp. Science
Del Uni e si y o Technology
Del , The Ne he lands
m.c e k[email p o ec ed]
Ky iaki-Ne eli D. Malamaki
Elec ical and Compu e Enginee ing
A is o le Uni e si y o Thessaloniki
Thessaloniki, G eece
ky iaki [email p o ec ed]
Geo gios C. K yonidis
Elec ical and Compu e Enginee ing
A is o le Uni e si y o Thessaloniki
Thessaloniki, G eece
[email p o ec ed]
Juan Manuel Mau icio
Depa men o Elec ical Enginee ing
Uni e sidad de Se illa
Se illa, Spain
[email p o ec ed]
Jos´
e Ma ´
ıa Maza-O ega
Depa men o Elec ical Enginee ing
Uni e sidad de Se illa
Se illa, Spain
[email p o ec ed]
Manuel Ba ag´
an-Villa ejo
Depa men o Elec ical Enginee ing
Uni e sidad de Se illa
Se illa, Spain
[email p o ec ed]
Abs ac —The inc easing pene a ion o enewable ene gy
sou ces is s ongly linked o he de elopmen o ol age sou ce
con e e s used in hei connec ion o he g id. As a esul , in
he nea u u e o an in e e -domina ed powe sys em i will
be a equi emen o enewable gene a ion o p o ide ancilla y
se ices in o de o compensa e o he absence o synch onous
gene a ion. In his scena io, he use o ene gy s o age sys ems
along wi h ad anced con ol algo i hms mimicking he dynamic
beha iou o he adi ional gene a o s will be o u mos impo -
ance. This pape deals wi h a enewable ene gy sou ce in e aced
wi h a ol age sou ce con e e and comp ising an ene gy s o age
sys em in he DC bus. Pa icula ly, a new ene gy managemen
algo i hm o he DC-bus based on a h ee le els hie a chical
con ol is p oposed, which is able o simul aneously p o ide
ancilla y se ices, main ain he s a e o cha ge o he s o age
sys em wi hin he pe missible limi s and use i o con ol he
DC bus ol age. The con ol s a egy is alida ed expe imen ally
using a p o o ype wi h esul s e idencing a eliable and s able
ope a ion.
Funded by he Eu opean Union Ho izon 2020 unde g an s 764090 and
Eu opean Resea ch In as uc u e suppo ing Sma G id Sys ems Technology
De elopmen , Valida ion and Roll Ou (E ig id).
Index Te ms— enewable gene a ion, ancilla y se ices, ene gy
s o age sys ems, ul acapaci o s, ol age sou ce con e e s
I. INTRODUCTION
The inc easing pene a ion o enewable ene gy sou ces
(RES) is leading o a p og essi e deca bonisa ion o he
elec ical sys em. The Eu opean Union has p oposed a clea
oadmap wi h he 2030 Clima e & Ene gy Package which aims
o achie e an inc ease o 32% o enewable ene gy in eg a ion
and a educ ion o 40% in g eenhouse gas emissions wi h
espec o 1990 by 2030 [1]. In addi ion o hese medium-
e m plans, he enewable ene gy sec o may con ibu e o
he eac i a ion o he cu en slow down economic scena io
a ec ed by he SARS-CoV-2 i us. As a ma e o ac , some
coun ies ha e begun o p omo e e en mo e his sec o , as he
Clima e Change and Ene gy T ansi ion Law ecen ly app o ed
by he Spanish Go e nmen [2].
In his a ou able scena io o he RES in eg a ion, se e al
echnical aspec s ha e o be sol ed o ope a e he u u e
in e e -domina ed powe sys em main aining he cu en o-
bus ness and e iciency s anda ds. Some o he main challenges978-1-6654-3597-0/21/$31.00 ©2021 IEEE
POI
VSC
+
DC/DC
Con e e
PV Plan
ESS
+
Fig. 1. PV in e e comp ising an ESS in e aced wi h a DC/DC con e e .
acing he u u e ne wo k a e equency con ol, ol age s a-
bili y, powe quali y and synch onisa ion issues in a powe
sys em wi h a educed ine ia [3]. The eby, RES may play
a mo e ac i e ole o sol e hese challenges h ough an
adequa e con ol and ene gy managemen [4], [5]. Fo una ely,
mos o he RES, like pho o ol aic and a iable-speed wind
gene a o s, ely on ol age sou ce con e e s (VSCs) which
no only p o ide an adequa e in e ace wi h he g id bu also
an enhanced con ol capabili y.
In ecen yea s, he so-called i ual synch onous gene a o s
(VSG) [6], [7] ha e eme ged as a new con ol s a egy
o manage he con e e -in e aced (CI) RESs which may
imp o e i s in eg a ion in he powe sys em. I has o be
conside ed, howe e , ha he in e mi ency o he p ima y
ene gy sou ce canno be sol ed by he con ol algo i hm. Fo
his eason, an ene gy s o age sys em (ESS) is equi ed o
enable he p o ision o hose ancilla y se ices (AS) ela ed
o ac i e powe like high equency powe smoo hing (HFPS)
[8], low equency powe smoo hing (LFPS) [9], i ual ine ia
(VI) [10] o p ima y equency esponse (PFR) [11]. The
ene gy and powe equi emen s associa ed o each o hese
AS depend on hei ac ua ion ime and de e mine he s o age
echnology o be used. Thus, as AS a e cha ac e ised by a
high ac i e powe , deli e ed du ing a sho - ime pe iod, while
la ge ene gy amoun s a e ela ed o hose slow AS. Fo his
eason, ul acapaci o s (UC) and elec ochemical ba e ies a e
used in hese applica ions espec i ely. Despi e he ac ha
any o hese ESSs can be connec ed o he powe sys em
using a dedica ed VSC, i is con enien o di ec ly in eg a e
i on an exis ing DC bus, as shown in Fig. 1 o he case o
a PV in e e . In his case, a DC/DC con e e is in oduced
o egula e he cu en injec ed o he DC bus and adap he
ol age le els be ween he ESS and he DC bus.
The ope a ion o he se up ep esen ed in Fig. 1 as a VSG
equi es he modi ica ion o he VSC con ol algo i hm, which
is ypically in cha ge o con olling he DC bus o a gi en
cons an e e ence [12]. This s a egy causes he VSC o injec
all he ac i e powe gene a ed om he RES and he ESS
in o he ne wo k in o de o main ain he DC bus ol age.
The e o e, he VSC is no able o con ol a desi ed ac i e
powe injec ed in o he ne wo k using his classical app oach.
A p ope p o ision o ASs equi es o al con ollabili y o he
powe injec ed in o he g id poin o in e connec ion (POI) by
he VSC [7]. This u ns he classic con ol o he VSC in o
an ope a ing mode incompa ible wi h a VSG. One possible
DC
DC
CTRL2
PI
PI
+
+
CTRL1
P [8]-[10]
Ac i e Powe Con ol [15]
DC
AC
CTRL3
Fig. 2. ESS hie a chical con ol scheme o he DC-bus ene gy managemen .
solu ion would be o use he ESS o con ol he DC bus
ol age ins ead o VSC [13]. This implies ha any a ia ion
be ween he powe om he p ima y ene gy sou ce, pg, and
he VSC con olled injec ed powe , p, mus be abso bed by
he ESS o main ain he DC bus ol age. The e o e, he VSC
may injec an ac i e powe su plus o AS p o ision which
depends on he ESS s o ed ene gy. Bu i has o be conside ed
ha he con ol o he DC bus ol age elies on he ESS
which has a limi ed s o ed ene gy. Fo his eason, i is key
o main ain he ESS s a e o cha ge (SoC) wi hin he sa e
ope a ing zone ecommended by he manu ac u e o gua an ee
a s able and eliable sys em ope a ion. This ope a ion mode
has been p oposed in [14] o ba e ies pa icipa ing in PFR,
especially in islanded mic og ids, and LFPS [15]. Howe e ,
hese s udies ocus mainly on he p o ision o he AS and
no he p ope managemen o he ba e y SoC be o e, du ing
and a e he p o ision o he AS. F om he au ho s’ bes
knowledge, he e is a gap in he S a e-o - he-a ha consis s
in p o iding a quali y AS while he ESS SoC is main ained
p ope ly con olled.
This pape p oposes a eliable algo i hm o con olling he
DC bus ol age o he CI-RES which allows he AS p o ision
while main aining he ESS SoC wi hin i s pe misible limi s.
The es o he pape is o ganised as ollows. Sec ion II
p esen s he ESS ene gy con ol s a egy. Sec ion III desc ibes
a p o o ype used o he expe imen al alida ion o he con ol
s a egy. Sec ion IV depic s and discusses he con olle pe -
o mance ia he ob ained esul s. Finally, Sec ion V closes
he pape wi h he main conclusions.
II. ESS CONTROL STRATEGY
ESS con ol is o ganised in a hie a chical manne wi h h ee
con ol le els as shown in Fig. 2: ESS ol age con ol loop
(CTRL3), DC bus ol age con ol loop (CTRL2) and cu en
con ol loop (CTRL1). The ollowing subsec ions desc ibe
each con ol le el and he ela ionships be ween hem.
A. Cu en con ol loop (CTRL1)
This le el is in cha ge o con olling he cu en il
dc h ough
he induc i e il e o he ESS by p ope ly ope a ing he
DC/DC con e e be ween ESS and he common DC bus.
Acco ding o Fig. 1 and using an a e aged model o he
DC/DC con e e , he ESS ol age can be o mula ed as:
l
dc =il
dc ·Rdc +Ldc ·
dil
dc
d + h
dc ·D, (1)
whe e l
dc is he ESS ol age, il
dc is he ESS injec ed cu en ,
Ldc and Rdc a e he induc ance and he esis ance o he DC
il e espec i ely, h
dc is he DC bus ol age and Dis he
du y a io o he DC/DC con e e . No e ha he ESS cu en
ollows a i s -o de dynamic gi en by (1). The e o e, his
cu en can be con olled by applying a classical p opo ional
and in eg al (PI) con olle . Thus, he du y a io, D, o ope a e
he DC/DC con e e can be compu ed as:
D=1
h
dc  l
dc +Ki
pil ?
dc −il
dc+Ki
iZil ?
dc −il
dcd ,
(2)
whe e Ki
pand Ki
ia e he p opo ional and he in eg al gains o
he PI con olle espec i ely and il ?
dc is he cu en e e ence
p o ided by he CTRL2.
B. DC bus ol age con ol loop (CTRL2)
This con ol le el is in cha ge o con olling he DC bus
ol age h ough he ESS cu en il
dc. The e o e, i s objec i e
is o p o ide he e e ence cu en il ?
dc o CTRL1 om a DC
bus ol age se poin h ?
dc , which is compu ed by a PI con olle
as ollows:
il ?
dc =K
p h ?
dc − h
dc +K
iZ h ?
dc − h
dc d , (3)
whe e K
pand K
ia e he p opo ional and he in eg al gains
o he PI con olle in CTRL2 espec i ely. No e ha CTRL2
and CTRL1 ollows he con en ional a angemen o cascade
con olle s. The e o e, in o de o design bo h con olle s
independen ly, he ime cons an o CTRL2 is se a leas en
imes slowe han CTRL1. Thus, he CTRL1 dynamics can be
igno ed in he design o CTRL2 [16].
C. ESS ol age con ol loop (CTRL3)
This con ol le el is in cha ge o con olling he ESS
ol age, which is di ec ly ela ed o i s SoC. Acco ding o
he scheme p esen ed in Fig. 1, he powe balanced in he DC
bus ul ils:
pESS =p−pg+ploss,(4)
whe e pgis he RES ac i e powe , pESS is he ESS ac i e
powe o he ESS, pis he VSC injec ed ac i e powe and
ploss a e he o al powe losses (including hose o he DC/DC
con e e , DC il e , VSC and AC il e ). I jus he p ima y
ac i e powe pgis injec ed in o he g id, he ESS has o cope
wi h he sys em powe losses. Howe e , i his powe balance
be ween pand pgis no ul illed due o he p o ision o an AS
in ol ing ac i e powe (like HFPS, LFPS, VI o PFR), i is
equi ed ha he ESS injec s his di e ence (∆pAS =p−pg):
pESS = ∆PAS +ploss.(5)
Equa ions (4) and (5) e idence ha , i espec i e i an AS
is p o ided o no , a con inuous con ol o he ESS SoC is
equi ed because o he pe manen ac i e powe demand pESS.
O he wise, i shall be possible o espass he sa e ope a ional
limi s p o ided by he manu ac u e which, in addi ion, may
cause a loss o con ol o he DC bus ol age. Fo doing so,
i is equi ed o abso b a gi en ac i e powe , ∆p?
ESS, o
main aining he ESS SoC. Pa icula ly, i is p oposed o apply
a p opo ional con olle as ollows:
∆p?
ESS =Kp
p( l
dc − l ?
dc ),(6)
whe e i has been conside ed ha he ol age l
dc is an
adequa e con ol magni ude ep esen ing he ESS SoC and l ?
dc
is he desi ed ESS ol age e e ence. This addi ional ac i e
powe mus be conside ed in he VSC powe e e ence as:
p?= ∆p?
AS +pg+ ∆p?
ESS.(7)
whe e ∆p?
AS is he e m co esponding o he p o ided AS.
The compu a ion o his e m is ou o he scope o his pape
bu mo e de ails can be ound in [8]–[10], [17].
I is in e es ing o no e ha , gi en a cons an p ima y
powe pg,∆p?
AS and ∆p?
ESS has an opposi e impac on
he ESS ol age. A posi i e ∆p?
AS causes a educ ion o he
ESS ol age due o he equi emen o an ex a ac i e powe
injec ion. As a esul , ∆p?
ESS will be nega i ely a ec ing
he e e ence o he VSC injec ed powe p?. The e o e, he
selec ion o he p opo ional con olle gain Kp
phas o sa is y
a comp omise solu ion o cope simul aneously wi h he wo
opposi e con ol equi emen s: AS p o ision bu main aining
he ESS SoC wi hin he limi s.
III. EXPERIMENTAL TESTBED
The expe imen al es bed used o he alida ion o he
p oposed con ol algo i hm o managing a DC bus wi h an
ESS is depic ed in Fig. 3. The main componen s o his
expe imen al se up a e:
•A h ee-phase h ee-wi e VSC a ed a 20 kVA wi h AC
side coupled h ough an induc i e-capaci i e-induc i e
(LCL) il e o he low ol age labo a o y g id. The
a ed AC ol age and DC ol age a e 400 V and 730
V espec i ely.
•An UC o 6 F and 160 V as ESS which is connec ed o
he VSC DC bus h ough an induc i e il e and a DC/DC
con e e .
•A con ollable DC cu en sou ce connec ed o he DC
bus o he VSC which is esponsible o ep oducing he
ac i e powe injec ed by he RES.
I is impo an o poin ou ha bo h he VSC and he DC/DC
con e e ha e been in eg a ed in a common powe elec onic
s ack ( ou -leg VSC) o achie e a compac design. This enables
o use a single con ol boa d o bo h de ices whe e he ana-
logue measu emen s om he VSC, he DC/DC con e e , he
p ima y ene gy sou ce and he co esponding IGBT swi ching
signals a e cen alized. In his way, i is possible o implemen
he p oposed hie a chical con ol algo i hm in he same de ice
wi h he possibili y o exchanging da a easily be ween he
VSC + DC/DC
con e e
DC bus UC
DC Cu en
Sou ce
LCL il e DC il e PCB boa d
VSC AC Fil e
UC
DC/DC
DC Sou c.
Fig. 3. Labo a o y expe imen al es bed and i s ci cui diag am.
di e en con ol laye s. This con ol algo i hm has been im-
plemen ed in a TMS320F28335 Del ino mic ocon olle om
Texas Ins umen s wi h a sampling equency o 20 kHz.
The main pa ame e s o he expe imen al se up and con-
olle gains a e summa ized in Table I. Acco ding o hese
gains, he ime cons an s o CTRL1 and CTRL2 a e 1 ms and
35 ms espec i ely. Rega ding he p opo ional gain o CTRL3,
i has been selec ed o ob ain a good dynamic esponse in
he AS p o ision bu main aining he ESS ol age wi hin
he ope a ional limi s. Fo his pu pose, he con ol algo i hm
pe o mance has been analysed wi h di e en p opo ional
gains in he case o an AS equi ing a s ep change o 20%
o he a ed powe du ing 5 seconds. The e olu ion o pand
l
dc o di e en alues o Kp
pis depic ed in Fig. 4. As ime
p og esses, he ESS ol age dec eases as expec ed, he eby
inc easing he alue o ∆p?
ESS and a ec ing he pe o mance
o he AS. I Kp
pis equal o ze o, he AS is no a ec ed by
CTRL3 in cha ge o he SoC egula ion, howe e he ESS
will ne e eco e i s co esponding e e ence SoC a e he
AS p o ision. The g ea e Kp
p he highe deg ada ion o he
AS p o ision, i.e. he injec ed powe is no main ained a
a cons an alue, bu he ESS ol age eco e s as e o i s
e e ence alue. Table II shows he pe cen age o powe and
ene gy deli e ed wi h espec o i s e e ence alue a he end
o he AS p o ison, he a ia ion o he ESS ol age and he
se ling ime in which he ESS e u ns o he 95% o i s o iginal
SoC.
TABLE I
PARAMETERS OF THE EXPERIMENTAL SETUP AND CONTROLLER GAINS.
Pa ame e Value
DC bus ol age ( h
dc )730 V
RMS AC VSC a ed ol age 400 V
VSC a ed powe 20 kVA
VSC swi ching equency 10 kHz
VSC side AC il e induc ance (L1)1.25 mH
G id side AC il e induc ance L21.25 mH
AC il e capaci ance (C)4µF
DC/DC con e e a ed powe 10 kW
DC/DC con e e swi ching equency 10 kHz
DC/DC con e e il e induc ance (Ldc)3mH
DC UC a ed ol age 160 V
UC capaci ance (CUC )6F
Con ollable DC sou ce a ed powe 30 kW
Ki
p. P opo ional gain o CTRL1 3.0
Ki
i. In eg al gain o CTRL1 100.0
τi. Time cons an o CTRL1 1.0ms
K
p. P opo ional gain o CTRL2 0.5
K
i. In eg al gain o CTRL2 5.0
τ . Time cons an o CTRL2 35.0ms
Kp
p. P opo ional gain o CTRL3 20.0
110
120
130
l
dc
(
V
)
Kp
p
= 0
Kp
p
= 10
Kp
p
= 20
Kp
p
= 30
0 2 4 6 8 10 12 14
Time (s)
18
20
p
(
kW
)
Kp
p
= 0
Kp
p
= 10
Kp
p
= 20
Kp
p
= 30
Fig. 4. E olu ion o pand l
dc o di e en alues o Kp
pwhen p o iding a
powe s ep as AS.
IV. EXPERIMENTAL RESULTS
This sec ion discusses he expe imen al esul s o applying
he con ol s a egy o sec ion II o he expe imen al es bed
explained in he p e ious sec ion. Two es s ha e been pe -
o med o e alua e he pe o mance o he p oposed con ol.
The i s es ca ied ou aims o alida e he cascade con ol
(CTRL1 and CTRL2) in cha ge o con olling he DC bus
ol age. The de ices in ol ed o e alua e hese con ol le els
TABLE II
INFLUENCE OF THE CTRL3 PROPORTIONAL CONTROL GAIN.
Kp
pP(%) E(%) ∆ l
dc (%) s(s)
0 100 100 19.74 -
10 95.56 98.35 19.32 97.39
20 91.39 96.73 18.96 49.63
30 87.22 95.12 18.61 33.76
a e he UC, DC/DC con e e and he DC bus o he VSC.
The ini ial SoC o he UC is equal o 128 V and he se poin
o he DC ol age h ?
dc o CTRL2 is p og essi ely inc eased
h ough a numbe o s ep e e ence changes om an ini ial
alue o 140 ol s o he inal 730 V co esponding o he
DC bus a ed ol age. The e olu ion o he DC bus ol age is
shown in he op plo o Fig. 5. This e lec s how he ol age
inc eases p og essi ely acco ding o he e e ence s ep changes
p o ided o CTRL2, which indica es an adequa e e e ence
acking. Fu he mo e, o e shoo s a e app ecia ed in some o
hese s eps acco ding o he second-o de dynamic esponse o
he cascade con ol. The du y a io o he DC/DC con e e D
and he ol age o he UC l
dc a e depic ed in he second and
hi d plo s o Fig. 5 espec i ely. The du y a io e ol es om
high alues close o 0.9 pu o alues close o 0.15 pu. No e
ha , in s eady-s a e condi ions and neglec ing he ol age d op
in he DC il e , he DC bus ol age is ela ed o he UC ol age
as: h
dc = l
dc/D. The e o e, he highe he DC bus ol age
he lowe he du y a io alue. The UC ol age dec eases
p og essi ely as he DC bus ol age inc eases due o he ene gy
ans e om he UC o he DC bus and he powe losses o he
DC/DC con e e . As a esul , he UC discha ges and educes
i s SoC. This e ec can also be obse ed in he UC injec ed
powe shown in he bo om plo o Fig. 5, which inc eases wi h
he DC bus ol age. This inc ease is due o he ac ha he
swi ching powe losses associa ed wi h he DC/DC con e e
a e di ec ly ela ed he DC bus ol age [18]. These esul s, in
addi ion, demons a e ha he expe imen al se up canno be
ope a ed inde ini ely only wi h CTRL2 and CTRL1 because
he UC will discha ge comple ely a e some ope a ion ime
and, consequen ly, leading o an unsa e si ua ion due o he
impossibili y o con olling he DC bus ol age as explained in
subsec ion II-C. The e o e, i is o ally necessa y o implemen
CTRL3 laye in cha ge o con olling he UC ol age.
The second es e alua es he CTRL3 pe o mance in ol ing
all he de ices p esen ed in Fig. 3 and he comple e con ol
algo i hm desc ibed in Sec ion II. To do his, he ac i e powe
e e ence o he VSC p?is se o a di e en alue han he
powe gene a ed by he p ima y RES powe pginjec ed by
he DC cu en sou ce. The di e ence be ween bo h powe s
ep esen s a gi en AS p o ision o he powe ne wo k. As
p e iously s a ed in he powe balance o (5), i can be deduced
ha his powe mus be p o ided by he UC. An ac i e powe
pgequal o 1kW is se h oughou he es and he e e ence
ol ages h ?
dc and l ?
dc a e se o 730 V and 125V espec i ely.
The esul s a e shown in Fig. 6 whe e i can be seen ha a
∆p?
AS o 3 kW is ac i a ed du ing 3.5 seconds a = 2 s
and ollowing up and down amps o 8 kW/s. As a esul ,
he VSC injec ed powe changes om he 1 kW injec ed by
he p ima y ene gy sou ce o 4 kW. The compa ison o he
e e ence and ac ual powe s e idences an excellen acking
du ing he i s wo seconds o he s ep change. Howe e , he
di e ence be ween hem inc eases om = 4 s because o he
CTRL3 ac ua ion in cha ge o main aining he UC e e ence
ol age. The impac on he AS p o ision is educed since he
maximum de ia ion o he powe and he ene gy a he end o
(a)
250
500
750
h
dc
(V)
(b)
0.25
0.50
0.75
D (p.u.)
(c)
120
125
l
dc
(V)
0 20 40 60 80 100 120 140 160
(d)
Time (s)
0
50
100
pESS
(W)
Fig. 5. Expe imen al alida ion o cascade con ol (CTRL2 and CTRL1):
e olu ion o (a) DC bus ol age e olu ion, (b) Du y a io o he DC/DC
con e e , (c) UC ol age, (d) UC powe .
Fig. 6. Expe imen al alida ion o he con ol algo i hm wi h a s ep change
o 3 kW: VSC injec ed powe o he g id.
he equi ed ac i e powe s ep is 13% and 5% espec i ely. In
addi ion, i is in e es ing o no e ha a e he AS p o ision he
VSC injec ed powe is lowe han he p ima y ac i e powe
because an ac i e powe consump ion is equi ed o eco e he
UC ol age o i s e e ence alue. Fig. 7 shows he e olu ion
o he UC ol age and powe du ing his es . I is in e es ing
o no e how he UC ac i e powe pe ec ly ma ches he ac i e
powe inc emen injec ed by he VSC o he g id. As a esul ,
he UC ol age ge s educed du ing he AS p o ision. In
addi ion, once he s ep change is inished he UC demands
ac i e powe om he p ima y sou ce o smoo hly inc ease
he ol age o i s e e ence alue.

(a)
100
120
140
l
dc
(V)
02468
(b)
Time (s)
0
2
pESS
(kW)
Fig. 7. Expe imen al alida ion o he con ol algo i hm wi h a s ep change
o 3 kW: e olu ion o (a) UC ol age, (b) UC powe .
V. CONCLUSIONS
This pape has p esen ed a DC-bus ene gy managemen o
a con e e -in e aced enewable ene gy sou ce comp ising an
ene gy s o age sys em. The objec i e is o con ol he DC
bus ol age o he CI-VSC using an ESS while, a he same
ime, con olling ESS SoC and p o iding eliable AS. To
achie e his goal, a hie a chical con ol s uc u e composed
o h ee le els is p oposed: ESS cu en con ol loop, DC
bus ol age con ol loop and ESS ol age con ol loop. The
i s wo con ol loops a e used o con ol he DC bus ol age
h ough he ESS o ming a classic cascade con ol. Meanwhile,
he hi d con ol loop aims o main ain he ESS ol age, and
he e o e i s SoC, wi hin he echnical limi s ecommended
by he manu ac u e and, simul aneously, p o ide he powe
equi ed by a gi en AS.
The p oposal was expe imen ally alida ed in a labo a o y
es bed composed o a CI-VSC wi h an UC and a DC cu en
sou ce emula ing a p ima y RES. Two es s ha e been ca ied
ou o e alua e he p esen ed con ol s uc u e. The i s es
alida es he i s wo cascade con ol loops by means o
successi e s ep-wise e e ence changes in he DC bus ol age.
The esul s show how he UC, h ough he p oposed con ol,
is able o con ol he DC bus ol age. Howe e , i is obse ed
ha he UC ol age dec eases p og essi ely as he DC bus
ol age inc eases because i eeds he p o o ype powe losses.
These esul s e idence he need o include he hi d con ol
le el in cha ge o con olling he UC ol age. The second es
e alua es he pe o mance o he comple e con ol algo i hm.
To do his, he p o ision o a ce ain AS is emula ed by
assigning a e e ence powe o he VSC ha is di e en om
he powe injec ed by he RES. The esul s show ha he
injec ed powe is con enien ly supplied by he UC du ing
he ini ial expe imen pe iod bu i is sligh ly a ec ed (less
han 15%) when he UC ol age dec eases because o he
in e ac ion o he con ol laye in cha ge o main aining his
ol age. Once he p o ision o he AS is inished, he UC
ol age p og essi ely inc eases un il i eaches he e e ence
ol age, abso bing powe om he p ima y RES.
The ob ained expe imen al esul s e eals an adequa e pe -
o mance o p oposed DC-bus ene gy managemen o RES
comp ising ESS. The e o e, u u e esea ch will be o ien ed o
in eg a e i wi hin mo e complex con ol a chi ec u es dealing
wi h AS p o ision and he co esponding ope a ional bene i s
p o ided o a con e e -domina ed powe sys em.
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