DC-bus energy management of a converter-interfaced renewable energy source comprising an energy storage system

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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