Voltage transformer and control method

Abstract

In at least one embodiment, the voltage transformer (1) comprises: - an input series and output parallel, ISOP, connec tion (21) of input series and output series, ISOS, modules (32) and / or an ISOS connection (22) of ISOP modules (31), and - control means (4), wherein - at least one of the ISOP modules (31) or the ISOS modules (32) comprises a plurality of solid-state transform ers, SSTs (33), and - the control means (4) are configured to perform a balancing control of intermediate voltages between individual ones of the SSTs (33) in the ISOS modules (32) of the ISOP connection (21) and / or between individual ones of the ISOP mod ules (31) in the ISOS connection (22).

Description

[0001] P2023,1549 WO N / P230153WO01 January28,2025 -1 - Description VOLTAGE TRANSFORMER AND CONTROL METHODA voltage transformer is provided. A method for con trollingsuch a voltage transformerisalso provided.Document WO 2023 / 002040 A1 refers to solid-state tr ansformershaving an active bridge.Documents US 2022 / 0278624 A1, US 2023 / 0178982 A1 an d US2023 / 0318435 A1 refer to solid-state power converte rs.Document Daniel Siemaszko et al., “ Power System Si mulationTool for Quick Benchmarking of Innovative MVDC Grid s in E-Mobility Applications“ in EPE'22 ECCE Europe, Septe mber 5,2022, ISBN: 978-9-0758-1539-9, discusses that DC mi crogridsare foreseen to become the backbone of interconnect ionbetween decentralized sources, loads and Energy Sto rageSystems. It is foreseen that Solid-State Transforme rs (SST)featuring a DC / DC isolated conversion are to be wid ely usedas elementary building blocks in such DC microgrids . Thefunction of the DC / DC isolated converter can be imp lementedin at least two well-known ways: a so-called resona ntapproach with an LLC tank and the isolated Dual Act ive Bridge(DAB). The choice between the two may be determined based onthe application requirements, namely the need for a DC / DCconverter with isolation or a DC transformer. The r esonantapproach has been extensively studied with the intr oductionofthe PowerElectronicsTransformer(PET).Mainly foreseenfor traction applications, the resonant approach re quires anadditionalfrontend forvoltage controlpurposes. P2023,1549 WO N / P230153WO01 January28,2025 -2 -Document Changjiang Sun et al., “Hybrid Input-Serie s-Output-Series Modular DC-DC Converter Constituted by Reson ant andNonresonant Dual Active Bridge Modules” in IEEE TRA NSACTIONSON INDUSTRIAL ELECTRONICS,Vol.69,No.1,January 2022, pages1062 to 1069,DOI:10.1109 / TIE.2021.3055175, discussesthat possessing the capability to handle high volta ge, thebidirectional input-series-output-series (ISOS) mod ular dc-dcconverter is suitable for use in dc grids. Regardin g topologyselection of the constituent modules, the open-loopcontrolled series-resonant dual active bridge (SR-D AB)converterexhibitssuperiorefficiencyperformance and theadvantage of simple control. However, it has no reg ulationcapability.Aimed to reap the advantagesofSR-DAB andachieve flexible control, this article presents a h ybrid ISOSconverter composed of SR-DAB and nonresonant phase- shiftcontrolled dual active bridge (PS-DAB) modules. The SR-DABmodules process most of the power to ensure high-ef ficiencyconversion, whereas the PS-DAB is responsible for f lexiblecontrol. At the output stage of the ISOS system, em beddednonisolated resonant dual active half-bridge (NR-DA HB)converters are integrated between every two adjacen t moduleswithout adding any switches. The transformer proper ty of theopen-loop controlled SRDAB and NR-DAHB circuits fac ilitatesnatural voltage sharing at both the input and outpu t sides.The hardware experiment has been conducted to verif y theoperating principles and performance of the propose d ISOSsystem.Documents WO 2021 / 048327 A1 and US 10742131 B2 re fer tovoltage controlsystems.A problem to be solved is to provide a voltage tran sformerthat can efficiently be configured in a modular man ner. P2023,1549 WO N / P230153WO01 January28,2025 -3 -This object is achieved, inter alia, by a voltage t ransformerand by a control method as defined in the independe nt claims.Exemplary further developments constitute the subje ct-matterofthe dependentclaims.According to at least one embodiment, the voltage t ransformercomprises an input series and output parallel, ISOP ,connection of input series and output series, ISOS, modules.Alternatively or additionally, the voltage transfor mercomprises an ISOS connection of ISOP modules. The t wo typesof connections, that is, the at least one ISOP conn ection andthe at least one ISOS connection, can be combined w ith eachother, or there is just one pure ISOS connection or just onepure ISOP connection.According to at least one embodiment, one or some o r all theISOP modules comprises one or a plurality of solid- statetransformers,SSTs.Alternativelyoradditionally, one or some orallofthe ISOS modulescomprisesone ora pluralityof SSTs. It is possible that all the transformers o f the ISOSmodules and / or of the ISOP modules are SSTs. All th e SSTs canbe ofthe same type ordifferenttypesofSSTsare combined with one anotherin the voltage transformer.According to at least one embodiment, the voltage t ransformercomprises control means. It is possible that the co ntrolmeans are distributed across at least some of the I SOPmodulesand / oracrossthe SSTs.Hence,the control meansdonot need to be a single unit but can be composed of apluralityofunits. P2023,1549 WO N / P230153WO01 January28,2025 -4 -The control means may also be referred to as a cont roller oras a control unit. For example, the controller is a convertercontroller or a part of a converter controller, the convertercontroller could take care of switching the SSTs, i nparticular. Hence, the terms ‘control means’, ‘cont roller’ or‘controlunit’maybe synonymous.According to at least one embodiment, the control m eans areconfigured to perform a balancing control of interm ediatevoltages. For example, the intermediate voltages ar e presentat balancing points. Thus, the balancing points may have theelectric potential defined by the intermediate volt age, atleasttemporarily.For example, balancing voltage control is done betw een theSSTs in the ISOS modules of the ISOP connection, th at is,within the ISOS modules. In the case of the ISOS co nnection,balancing voltage control can be done between the I SOPmodules.According to at least one embodiment, the balancing voltagesare presentbetween individualonesofthe SSTsin the ISOS modulesofthe ISOP connection.Alternativelyoradditionally, the balancing voltages are present be tweenindividual ones of the ISOP modules in the ISOS con nection.The term ‘between’mayinclude thatthe respective voltage ispresent on an electrical connection line between th erespective components and / or that the respective vo ltage ispresent at an input port and / or at an output port o f theassociated ISOP modulesorSSTs,respectively. Forexample,there isa balancing pointin the two connectionlines between every pair of adjacent SSTs or ISOP m odules. P2023,1549 WO N / P230153WO01 January28,2025 -5 -Thus, if there are N SSTs or ISOP modules, there ar e N-1intermediate points in each one of the two electric linesconnecting the N SSTs or ISOP modules so that there can be2(N-1) balancing points. N is a natural number grea ter thanorequalto two;forexample,2 ≤ N ≤ 60 or3 ≤ N ≤ 30 or 3 ≤ N ≤ 15.In at least one embodiment, the voltage transformer comprisesan input series and output parallel, ISOP, connecti on ofinput series and output series, ISOS, modules and / o r an ISOSconnection of ISOP modules and further comprises co ntrolmeans. At least one of the ISOP modules or the ISOS modulescomprisesa pluralityofsolid-state transformers, SSTs.Thecontrol means are configured to perform a balancing controlof intermediate voltages between individual ones of the SSTsin the ISOS modules of the ISOP connection and / or b etweenindividual ones of the ISOP modules in the ISOS con nection.Thus, the voltage transformer makes use, inter alia , of theidea to control a series parallel arrangement of SS T cells.ISOP and IPOS, input parallel and output series, ar rangementsof SSTs allow to scale up in voltage on one side an d currenton the other side. This structure can be used for m edium-voltage direct current, MVDC, to low-voltage direct current,LVDC, configurations, in which the cells are connec ted inseries on the MVDC side, and in parallel on the LVD C side.Controlofsuch arrangementsisstraightforward as each SST can controlone given voltage to ensure the system stability,either on the LVDC side or on the MVDC side, and ca n evenswitch the DC grid forming side when needed. P2023,1549 WO N / P230153WO01 January28,2025 -6 -However, MVDC to MVDC conversion with SST modules r equiresseries connection on both sides, aka ISOS for input seriesand output series, or ISOPOS for input series outpu t paralleloutput series. With classic SST control of N module s that cancontrol N voltages, 2(N-1) neutral points cannot be allcontrolled at the same time which may lead to syste m voltageinstability. With two modules in ISOS, it is possib le tooperate between two given DC grids, but not to grid form anyof them. From three modules it is not possible to f ullycontrol intermediate voltage points with such an ap proach.In the voltage transformerdescribed herein,there is,forexample, a reconfigurable and modular arrangement o f SSTelementary cells for allowing hybrid series and par allelconnections on both sides, that is, on the low-volt age and onthe high-voltage side. For example, there are two t imes four-seriesSST stringsin parallel.The control method described herein can ensure stab ility andintermediate voltage pointbalance forthe voltagetransformer described herein. Hence, for example, i t ispossible to connect MVDC to MVDC with different vol tageranges. The modular arrangement allows easy replace ment andredundancyforbetteravailability.In short, one aspect of the voltage transformer des cribedherein lays in a two-layer control approach for rea ching apluralityofmodularconfigurationswith flexible arrangementsofseriesand parallelconnections.With the voltage transformer described herein, a hy brid andflexible configuration of MVDC / MVDC converter based on justone SST elementarycellcan be achieved. P2023,1549 WO N / P230153WO01 January28,2025 -7 -According to at least one embodiment, one or some o r all theSSTs include in internalarrangementbeing partof thecontrol means. For example, each one of the respect ive SSTsincludesthe same type ofinternalarrangement.By meansofthe internal arrangements, the intermediate voltage s can bemeasured and / or adjusted. For example, the internalarrangements each include one or a plurality of act ivebridges. The SSTs may be dual-active-bridge convert ers. Thisapplies in particular for the SSTs in the ISOS modu les of theISOP connection.By way of example, document WO 2023 / 002040 A1 discl oses SSTshaving active bridges; concerning the active bridge s, thedisclosure content of document WO 2023 / 002040 A1 is herebyincorporated byreference.According to at least one embodiment, one or some o r all theISOP modulesofthe ISOS connection include one of theinternal arrangements. It is possible that the inte rnalarrangements are included at least in a first one a nd / or alast one of the series of SSTs in the ISOP modules. Thus, asstated above, the internal arrangements of at least therespective SSTsmayinclude active bridges.Hence, the respective ISOP modulesand / orSSTsare configured to measurethe assigned intermediate voltages and / or to adjust theassigned intermediate voltages.According to at least one embodiment, the control m eanscomprisessub-units.Each one ofthe sub-unitsis electricallyarranged between adjacentonesofthe SSTs,forexample, in the ISOS modules of the ISOP connection and / orbetween adjacent ones of the ISOP modules in the IS OS P2023,1549 WO N / P230153WO01 January28,2025 -8 -connection. For example, the sub-units may compriseproportional operators and may generate control sig nals sothat the sub-units are configured to measure the as signedintermediate voltages and / or to adjust the assignedintermediate voltages. It is possible that the sub- unitsgenerate control signals and forward the control si gnals tothe respectivelyassigned SSTsand / orISOP modules so thatbymeans of the respectively assigned SSTs and / or ISOP modulesthe intermediate voltagescan be adjusted.Thus, the control means can include internal arrang ementsbeing included in the SSTs or ISOP modules and / or t he controlmeans can include sub-units not being included in t he SSTs orthe ISOP modules but being external components loca tedoutside ofthe SSTsorthe ISOP modules.According to at least one embodiment, the voltage t ransformeris configured for transforming a first medium-volta ge directcurrent, MVDC, to a second MVDC. The first MVDC and thesecond MVDC can be in different voltage ranges, and thesevoltage rangesmaynotoverlap.Bywayofexample, the firstMVDC may be at a higher voltage than the second MVD C;likewise, the second MVDC may be at a higher voltag e than thefirstMVDC. According to atleastone embodiment,atleastone ofthefirst MVDC or the second MVDC is at a voltage of at least 1kV or of at least 10 kV or of at least 20 kV. Alter nativelyoradditionally,an upperlimitforthe firstMVDC and / orfor the second MVDC is100 kV oris50 kV oris20 kV.According to at least one embodiment, both the firs t MVDC andthe second MVDC are fixed. Thus, the voltage transf ormer is P2023,1549 WO N / P230153WO01 January28,2025 -9 -configured for a specific first MVDC and for a spec ificsecond MVDC. In this case, for example, a power pro vided byor handled by the voltage transformer can be set. H ence, thevoltage transformer may be configured for balancing voltagecontrolonly.Thismaymean thatthe onlyvoltages controlledwithin the voltage transformer are the balancing vo ltages. Inaddition, there may be power control of the voltagetransformerand ofthe SSTs.According to at least one embodiment, the voltage t ransformeris configured for controlling either the first MVDC or thesecond MVDC.Thatis,eitherthe firstMVDC orthe secondMVDC may be adjustable and may be set within a spec ificrange. Hence, the voltage transformer may also be c onfiguredfor balancing voltage control, in addition to contr ollingeitherthe firstMVDC orthe second MVDC.According to at least one embodiment, one or some o r all theSSTs are two-portSSTs.According to at least one embodiment, one or some o r all theSSTs are three-portSSTs.According to at least one embodiment, the voltage t ransformercomprises a hybrid arrangement of the two-port SSTs and ofthe three-port SSTs. The different types of SSTs ma y bepresentin separate modulesormaybe mixed within the same module,forexample,within one orsome orallthe ISOP modulesorthe ISOS modules.According to at least one embodiment, some or all t he SSTs,like the three-port SSTs, are arranged in as stacke d manner. P2023,1549 WO N / P230153WO01 January28,2025 -10 - Thisappliesin particularforallthe SSTswithin one or some orallthe ISOS modules.According to at least one embodiment, in which some or all ofthe SSTs are arranged in a stacked manner, the volt agetransformer features one or a plurality of single-w indingtransformers or one or a plurality of multi-windingtransformers. By means of the at least one single-w indingtransformerand / orthe atleastone multi-windingtransformer, DC / AC units of the SSTs can be coupled with oneanother on the two sides of the voltage transformer in multi-fold manners so that the specific requirements of v ariousapplicationscan be matched.According to at least one embodiment, the voltage t ransformercomprises one or a plurality of multi-winding trans formers.By means of the at least one multi-winding transfor mer, someor all of the SSTs of the voltage transformer or of the atleastone ISOP orISOS connection are coupled.According to at least one embodiment, the voltage t ransformerfurther comprises an energy storage, like an integr atedenergy storage. The energy storage can be coupled t o one orsome or all the SSTs, especially the three-port SST s. It ispossible that some of the three-port SSTs have thei r ownintegrated energy storage, like a rechargeable batt ery.According to at least one embodiment, one or some o r all theISOS modules and / or the ISOP modules comprise at le ast threeand atmost30 ofthe SSTs.According to at least one embodiment, one or some o r all theISOP connections and / or the ISOS connections compri se at P2023,1549 WO N / P230153WO01 January28,2025 -11 -least two or at least three or at least five of the ISOSmodules or the ISOP modules, respectively. Alternat ively oradditionally, this number of ISOS modules or ISOP m odules inthe ISOP connections and / or in the ISOS connections ,respectively, is at most 100 or is at most 30 or is at most15.According to at least one embodiment, the voltage t ransformeris reconfigurable. This means, for example, that in dividualmodules can be replaced after an initial configurat ion and / orinstallation of the voltage transformer. For exampl e, atleast one of the ISOS modules and / or at least one o f the ISOPmodules may be replaceable. This may also mean that changescan be made on the set-up of the voltage transforme r after abasicconfiguration ofthe voltage transformerhas beendesigned and / or constructed. Thus, by way of exampl e, thevoltage transformer may have a basic design which c an easilybe modified to match the respective requirements of adistinctapplication.Itmayalso be possible that the typeof connection, that is, ISOS connection or ISOP con nection oranymixture,can be changed afterdesigning and / or installingthe voltage transformer. Accordingly, the voltage t ransformermay have a high adaptability to applications or cha ngingconditionsofan application,possiblyafterbeing installed.A control method for the voltage transformer is add itionallyprovided. By means of the control method, a voltagetransformer as indicated in connection with at leas t one ofthe above-stated embodiments can be controlled. Fea tures ofthe voltage transformer are therefore also disclose d for thecontrolmethod and vice versa. P2023,1549 WO N / P230153WO01 January28,2025 -12 -In at least one embodiment, the control method is f orcontrolling a voltage transformerand comprises:Performing balancing control of the intermediate vo ltagesbetween individualonesofSSTsin ISOS modulesof an ISOPconnection and / or between individual ones of ISOP m odules inan ISOS connection.The voltage transformer described herein may be use d, forexample, in a railway network, in vehicle or vessel networksorin photovoltaicsystems. In short,forexample,the voltage transformermay thusenable two-layer control allowing flexible ISOS con nectionsof ISOP modules and ISOP connections of ISOS module s. Aflexible and reconfigurable arrangement of SSTs forconnecting MVDC to MVDC can be achieved. Control an d / or DCgrid forming of one MVDC port with the two-port SST basedmodulararrangementispossible.Moreover,control and / orDC grid forming oftwo MVDC portswith the three-port SST basedmodular arrangement with energy storage is also pos sible.A voltage transformer and a control method describe d hereinare explained in greater detail below by way of exe mplaryembodiments with reference to the drawings. Element s whichare the same in the individual figures are indicate d with thesame reference numerals.The relationshipsbetween theelements are not shown to scale, however, but rathe rindividual elements may be shown exaggeratedly larg e toassistin understanding. In the figures: P2023,1549 WO N / P230153WO01 January28,2025 -13 -Figure 1 is a schematic block diagram of an exempla ryembodimentofa voltage transformerdescribed herein,Figure 2 is a schematic representation of an exempl aryembodiment of a voltage transformer described herei nutilizing an ISOP connection ofISOS modules,Figure 3 is a schematic representation of an interc onnectionofSSTsin exemplaryembodimentsofvoltage transformersdescribed herein,Figures 4 to 6 are schematic representations of exe mplaryembodimentsofcontrolschemesforvoltage transformers described herein as shown in Figure 2,Figure 7 is a schematic representation of an exempl aryembodiment of a voltage transformer described herei nutilizing an ISOS connection ofISOP modules,Figures 8 and 9 are schematic representations of ex emplaryembodimentsofcontrolschemesforvoltage transformersdescribed herein, Figures10 and 11 are schematicrepresentationsof exemplary embodimentsofvoltage transformersdescribed herein,andFigure 12 is a schematic block diagram of an exempl aryembodimentofa controlmethod forvoltage transformersdescribed herein. P2023,1549 WO N / P230153WO01 January28,2025 -14 -Figure 1 illustrates an exemplary embodiment of a v oltagetransformer1.The voltage transformer1 comprises an inputseries - output parallel, ISOP, connection 21 of in put series- output series, ISOS, modules 32, see in more deta il Figure2.Alternatively,the voltage transformer1 and / or an ISOSconnection 22 of ISOP modules 31, see in more detai l Figure7. However, mixtures of such ISOP connections 21 an d ISOSconnections22 are in principle also possible,for example,if an additional layer may be used. Moreover, the v oltagetransformer 1 comprises control means 4. The contro l means 4may integrallybe included in the ISOP connections 21 and / or ISOS connections22.At least one of the ISOP modules 31 or the ISOS mod ules 32comprises a plurality of solid-state transformers33 , SSTs forshort. The control means 4 are configured to perfor m abalancing controlofintermediate voltagesbetween individualones of the SSTs 33 in the ISOS modules 32 of the I SOPconnection 21 and / or between individual ones of the ISOPmodules31 in the ISOS connection 22.Figure 2 illustrates the ISOP connection 21 of ISOS modules33. There are M of the ISOS modules 32 in parallel. Forexample, all the ISOS modules 32 are of the same ty pe and,thus, may have the same number of SSTs 33, also ref erred toasSST modules.Thus,each one ofthe ISOS modules 32 maycomprise N SSTs 33. Accordingly, there can be M x N SSTmodules,N SST modulesin seriesan M in parallel. One oftheISOS modules 32 is shown in more detail on the righ t side ofFigure 2.Forexample,3 and / or3 ≤ M ≤ 15,wherein M and N are naturalnumbers. P2023,1549 WO N / P230153WO01 January28,2025 -15 -At a first side of the voltage transformer 1, there is afirst MVDC A and at a second side there is a second MVDC B.For example, the MVDCs A, B have voltages of at lea st 10 kVand ofatmost50 kV.Between adjacent SSTs 33 in the ISOS modules, there are twobalancing points 6 at which there is in each case a balancingvoltage to be controlled.Hence,in case ofN SSTs 33,theremay be 2(N-1) of the balancing points 6. For measur ing andadjusting the balancing voltage at the balancing po ints 6,the SSTs 33 each may include an internal arrangemen t 43. Allthe internal arrangements 43 may make the control m eans 4.For example, the internal arrangements 43 are based on multi-active bridges,notshown in detail.Hence, this configuration features an ISOP connecti on 21 ofISOS modules32,and a high-levelconfiguration is fullycontrollable, that is, enabled by ISOP control. A l ow-levelconfiguration requires a balancing control of the b alancingvoltage atthe balancing points6 which isenabled bymeans ofthe controlmeans4,43.Otherwise, the same as to Figure 1 may also apply t o Figure2,and vice versa.In Figure 3 it is shown that the control means 4 ma y berealized by external sub-units 44, that is, by addi tionalcomponents placed between the SSTs 33. Such sub-uni ts 44 maybe based on proportional operators. The sub-units 4 4 may bepresentinstead ofthe internalarrangements43 as depictedin Figure 2, or there can by any mixture of the sub -units 44and the internalarrangements43.The same applies forall otherembodiments. P2023,1549 WO N / P230153WO01 January28,2025 -16 -Otherwise, the same as to Figure 2 may also apply t o Figure3,and vice versa.In Figures 4 to 6, some control schemes for voltagetransformers 1 of the type as shown in Figure 2 areillustrated. According to Figure 4, both the high M VDCvoltage A as well as the low MVDC voltage B are fix ed. Thus,at a Level 1, there is no voltage control; that is, Level 1may simply be omitted in this case, but is drawn fo r bettercomprehensibilitybetween the Figures4 to 6.Ata Level2,apower setpoint SP is provided, and high-level power controlis performed. At a Level 3, low-level power control can beachieved while at a Level 4, single SST power contr ol isdone. Thus, in context of Figure 4 only balancing v oltagecontrol is applied as the only voltage control, and this isdone on Level3 within the ISOS modules32.In Figure 5, the low, second MVDC B is controlled a nd avoltage setpoint SU is provided to achieve MVDC vol tagecontrol at Level 1. The high, first MVDC A is provi ded at theLevel 2. As in Figure 4, at Level 3 low-level power controlcan be achieved and at a Level 4 single SST power c ontrol canbe done. Thus, in context of Figure 5 balancing vol tagecontrolisapplied in addition to low MVDC voltage controlsothat there are two types of voltage being controlle d.The scheme of Figure 6 corresponds to the scheme of Figure 5,but instead of the low, second MVDC B the high, fir st MVDC Ais controlled by providing the voltage setpoint SU, and thelow,second MVDC B isfixed. P2023,1549 WO N / P230153WO01 January28,2025 -17 -Otherwise, the same as to Figures 1 to 3 may also a pply toFigures4 to 6,and vice versa.The voltage transformer of Figure 7 features an ISO Sconnection 22 ofISOP modules31.Thus, there are M of the ISOP modules 31 in series. Forexample, all the ISOP modules 31 are of the same ty pe and,thus, may have the same number of SSTs 33. Thus, ea ch one ofthe ISOS modules31 maycomprise N SSTs33.Hence, there can be M xN SST modules,N SST modulesin seriesan M inparallel. One of the ISOP modules 31 is shown in mo re detailon the right side of Figure 7. Again, like in Figur e 2, atthe firstside ofthe voltage transformer1,there isthefirst MVDC A and at the second side there is the se cond MVDCB.The MVDCs A,B mayhave voltagesofatleast10 kV and of atmost50 kV.Forexample,2 and / or2 ≤ M ≤ 30 or alternatively3 ≤ M ≤ 15,wherein M and N are naturalnumbers.Between adjacent ISOP modules 31 in the ISOS connec tion 22,there are two balancing points6 atwhich there is in eachcase the balancing voltage to be controlled. Hence, in caseof N ISOP modules 31, there may be 2(N-1) of the ba lancingpoints 6. For measuring and adjusting the balancing voltageat the balancing points 6, at least terminal SSTs 3 3 in theISOP modules 31 may include at least one of the int ernalarrangements 43 or alternatively there can be the s ub-units44 between the ISOP modules similar to what is show n inFigure 3. All the internal arrangements 43 may make thecontrol means 4. For example, the internal arrangem ents 43can be based on multi-active bridges, again not sho wn indetail. P2023,1549 WO N / P230153WO01 January28,2025 -18 -Hence, this configuration features an ISOS connecti on 22 ofISOP modules31,and a high-levelconfiguration is fullycontrollable, that is, enabled by ISOP control. The low-levelconfiguration requires the balancing control of the balancingvoltages at the balancing points 6 which is enabled by meansofthe controlmeans4,43,44.Otherwise, the same as to Figures 1 to 6 may also a pply toFigure 7,and vice versa.The control schemes of Figures 8 and 9 refer to a v oltagetransformer 1 of the type shown in Figure 7, and th erepresentation of Figures 8 and 9 corresponds to th erepresentation ofFigures4 to 6.Like in Figure 4, in Figure 8 both the MVDCs A, B a re fixedso that there is no voltage control at Level 1, and at Level2 high-level balancing control is performed by mean s of thepower setpoint SP. At Level 3, low-level power cont rol isperformed.AtLevel4,single SST powercontrolis done.Thus, in context of Figure 8 only balancing voltage controlis applied as the only voltage control, and this is done onLevel2 between the ISOP modules31.In Figure 9, either the low, second MVDC B is contr olled anda voltage setpoint SU is provided to achieve MVDC v oltagecontrol at Level 1, and the high, first MVDC A is p rovided atthe Level 2, or the high, first MVDC A is controlle d byproviding the voltage setpoint SU, and the low, sec ond MVDC Bis fixed. As in Figure 8, at Level 2 high-level bal ancingcontrol is done and at Level 3 low-level power cont rol is P2023,1549 WO N / P230153WO01 January28,2025 -19 -performed. Again, at a Level 4 single SST power con trol canbe done.Otherwise,reference ismade to Figure 8.Otherwise, the same as to Figures 1 to 7 may also a pply toFigures8 and 9,and vice versa.Figures 10 and 11 show further embodiments of the v oltagetransformer 1. Both in the ISOP connection 21 confi gurationsand in the ISOS connection 22 configurations, an in ternalset-up can be done with individual SSTs 33 and sing le medium-frequency transformers, MFTs, see Figure 10, left s ide.However, this can also be reached with multi-windin g MFTs,see Figure 10, right side. For example, in the mult i-windingcase, a plurality of set-ups can be drawn with vari ouswinding ratios, and possibly different winding coun ts on theprimaryand the secondaryside.Especially, in Figure 10, left side, it is shown th at thevoltage transformer 1 can be composed of a pluralit y ofsingle-winding transformers. Although four single-w indingtransformers are shown in Figure 10, of course ther e can bedifferent numbers of transformers. In Figure 10, ri ght side,it is illustrated that just one multi-winding trans former isused, possibly with different numbers of DC / AC unit s on thetwo sides of the multi-winding transformer. In addi tion towhat is shown in Figure 10, there can be combinatio ns of oneorseveralsingle-winding transformerswith one or severalmulti-winding transformers. The same applies for th e otherembodiments. Thus, stacked SSTs with one or more si ngle-winding transformers or one multi-winding transform er or aplurality of multi-winding transformers can be used hereinfor the voltage transformer 1 and the ISOP and / or I SOSconnections21,22. P2023,1549 WO N / P230153WO01 January28,2025 -20 -In context of Figure 11, three-port SSTs 33 with anintegrated energy storage 5 are used. This is possi ble bothin the ISOP connection 21 configurations and in the ISOSconnection 22 configurations. There can be just one energystorage 5,see Figure 11,leftside,orthere isa pluralityof the energy storages 5, see Figure 11, right side .Different unit configurations of the SSTs 33 on the firstside and the second side of the voltage transformer 1 arepossible. For example, the number of DC / AC units on the firstside can be smaller or alternatively larger or also the sameasthe numberofDC / AC unitson the second side of the voltage transformer1.With the energy storage 5 it is possible to control voltageson both sides of the SSTs, for example. By way of e xample,stacked three-portSSTs33 can controlvoltagesin fullserial-serial configurations, therefore reaching al l MVDClevelsisenabled.Further, hybrid arrangements of two-port SSTs 33 an d three-port SSTs 33 can suit various applications with hig hflexibilityand optimized costs.When the energy storage is empty, or during chargin g, thenpreviously described balancing control can be appli ed.Otherwise, the same as to Figures 1 to 9 may also a pply toFigures10 and 11,and vice versa. Finally,in Figure 12 an embodimentofthe control method is schematicallyshown. P2023,1549 WO N / P230153WO01 January28,2025 -21 -In optional method step M1, the voltage transformer 1 isdesign and / or provided and / or installed. Hence, aft er methodstep M1 the voltage transformer 1 can have a partic ularconfiguration.In method step M2, balancing control of the interme diatevoltages between the individual ones of the SSTs 33 in theISOS modules 32 of the ISOP connection 21 and / or be tween theindividualonesofthe ISOP modules31 in the ISOS connection22 is performed. Thus, by doing so a particularly s table modeof operation of the voltage transformer 1 can be ac hieved.In optional method step M3, the configuration of th e voltagetransformer 1 is changed. This may be done by repla cing oneor some of the modules 31, 32 and / or by modificatio ns in acontrolscheme which maybe achieved bya software update, forexample.In optional method step M4, the voltage transformer 1 isoperated in accordance with the reconfiguration don e inmethod step M3. Otherwise,the same asto Figures1 to 11 mayalso applyto Figure 12,and vice versa.The invention described here is not restricted by t hedescription on the basis of the exemplary embodimen ts.Rather, the invention encompasses any new feature a nd alsoany combination of features, which includes in part icular anycombination offeaturesin the patentclaims,even ifthisfeature or this combination itself is not explicitl yspecified in the patent claims or exemplary embodim ents. P2023,1549 WO N / P230153WO01 January28,2025 -22 -This patent application claims the priority of Euro peanpatent application 24156032.5, the disclosure cont ent ofwhich isherebyincorporated byreference.

[0002] P2023,1549 WO N / P230153WO01 January28,2025 -23 - ListofReference Signs 1 voltage transformer 21 ISOP connection 22 ISOS connection 31 ISOP module 32 ISOS module 33 solid-state transformer 4 controlmeans 43 internalarrangement 44 externalsub-unit 5 integrated energystorage 6 balancing point A firstMVDC B second MVDC C low-voltage directcurrent L.. level M method step SP powersetpoint SU voltage setpoint

Claims

P2023,1549 WO N / P230153WO01 January28,2025 -24 - PatentClaims 1.A voltage transformer(1)comprising:- an input series and output parallel, ISOP, connec tion (21)of input series and output series, ISOS, modules (3 2), and-controlmeans(4), wherein - the ISOS modules(32)each comprise a plurality ofsolid- state transformers,SSTs(33),and- the control means (4) are configured to perform a balancingcontrol of intermediate voltages between individual ones ofthe SSTs(33)in the ISOS modules(32)ofthe ISOP connection (21).

2. The voltage transformer (1) of the preceding cla im,wherein at least some of the SSTs (33) include an a ctivebridge, the active bridges being part of the contro l means(4),wherein these SSTs (33) are configured to measure t heintermediate voltages and / or to adjust the intermed iatevoltages.

3. The voltage transformer (1) of any one of the pr ecedingclaims,wherein the control means (4) comprises sub-units ( 44), eachone of the sub-units (44) being electrically arrang ed betweenadjacentonesofthe SSTs(33)in the ISOS modules (32)of the ISOP connection (21).

4. The voltage transformer (1) of any one of the pr ecedingclaims,being configured for transforming a first medium-vo ltagedirectcurrent,MVDC,to a second MVDC.P2023,1549 WO N / P230153WO01 January28,2025 -25 -5. The voltage transformer (1) of the preceding cla im,wherein the first MVDC and the second MVDC each hav e avoltage ofatleast10 kV and ofatmost50 kV.

6. The voltage transformer (1) of any one of the tw opreceding claims,wherein both the first MVDC and the second MVDC are fixed,wherein the voltage transformer (1) is configured f orbalancing voltage controlonly. 7.The voltage transformer(1)ofclaim 4 or5,wherein the voltage transformer (1) is configured f orcontrolling either the first MVDC or the second MVD C, andwherein the voltage transformer (1) is also configu red forbalancing voltage control.

8. The voltage transformer (1) of any one of the pr ecedingclaims,wherein at least some of the SSTs (33) are two-port SSTsand / or at least some of the SSTs (33) are three-por t SSTs.

9. The voltage transformer (1) of the preceding cla im,comprising a hybrid arrangement of the two-port SST s and ofthe three-portSSTs.

10. The voltage transformer (1) of any one of the p recedingclaims,wherein at least some of the SSTs (33) are arranged in astacked manner featuring a single-winding transform er or oneora pluralityofmulti-winding transformers.P2023,1549 WO N / P230153WO01 January28,2025 -26 -11. The voltage transformer (1) of any one of the p recedingclaims, comprising a multi-winding transformerbymeansof which at leastsome ofthe SSTs(33)are coupled.

12. The voltage transformer (1) of any one of the p recedingclaims,further comprising an integrated energy storage (5) coupledto atleastone ofthe SSTs(33).

13. The voltage transformer (1) of any one of the p recedingclaims,wherein the ISOS modules (32) each comprise at leas t threeand atmost60 ofthe SSTs(33).

14. The voltage transformer (1) of any one of the p recedingclaims, which isreconfigurable.

15. A control method for controlling a voltage tran sformer(1) according to any one of the preceding claims co mprising:performing balancing control of the intermediate vo ltagesbetween the individual ones of the SSTs (33) in the ISOSmodules(32)ofthe ISOP connection (21).

Images