Operating method and power converter system

Abstract

By means of an operating method a power converter system (1) is operated, the power converter system (1) includes a plurality of current switches (21, 22), a plurality of sensors (3, 31, 32, 33) and a control unit (4), the method comprises: - switching, by the control unit (4), the current switches (21, 22); - measuring, by the sensors (3, 31, 32, 33), radiated and / or conducted electromagnetic noise caused by the switching of the current switches (21, 22); - modifying, by the control unit (4), at least one of turn-on times, turn-off times, rise times or slopes of at least some of the current switches (21, 22) so that the radiated and / or conducted electromagnetic noise of the power converter system (1) is reduced in at least one frequency band; and - controlling, by the control unit (4), the current switches (21, 22) according to the modified turn-on times and turn-off times.

Description

[0001] P2023,1187 WO E / P230049WO01 November29,2023 -1 - Description Operating method and powerconvertersystemAn operating method for a power converter system is provided.A powerconvertersystem isalso provided.Document B. Narayanasamy and F. Luo, "A Survey of A ctive EMIFiltersforConducted EMINoise Reduction in Power ElectronicConverters" in IEEE Transactions on ElectromagneticCompatibility,Vol.61,No.6,pages2040 to 2049, Dec.2019, discussesthe use ofEMIfilters.Document Y. Huang et al., "A Trigger Signals Modifi cationScheme for Common-Mode Conducted EMI Reduction of M odularMultilevel Converter" in IEEE Journal of Emerging a ndSelected Topicsin PowerElectronics,Vol.10,No. 6,pages 7214 to 7224,Dec.2022,discussesEMIreduction.Document A. Nami et al., "Modular Multilevel Conver ters forHVDC Applications:Review on ConverterCellsandFunctionalities" in IEEE TRANSACTIONS ON POWER ELEC TRONICS,Vol. 30, No. 1, pages 18 to 36, Jan. 2015, discusse s MMCs.An object to be solved is to provide a power conver ter systemthat has reduced radiated and conducted electromagn eticemission.This object is achieved, inter alia, by a power con vertersystem and by a method as defined in the independen t claims.Exemplary further developments constitute the subje ct-matterofthe dependentclaims. P2023,1187 WO E / P230049WO01 November29,2023 -2 -According to at least one embodiment, by means of t heoperating method a power converter system is operat ed. Forexample, the power converter system is configured t o convertalternating current,AC,powerfrom a transmitting grid todirect current, DC, for delivery through a link, be foreconverting itbackto AC poweratanotherend.The powerconverter system may be used in applications like S uedLinkDC4 to transfer up to 2 GW of clean energy, which w ill beenough to powerfive million homes.According to at least one embodiment, the power con vertersystem includes a plurality of current switches. Th e currentswitches can be semiconductor devices. For example, thecurrent switches are selected from the following gr oup:metal–insulator–semiconductor field-effect transist or,MISFET, metal–oxide–semiconductor field-effect tran sistor,MOSFET, insulated-gate bipolar transistor, IGBT, re verse-conducting insulated-gate bipolar transistor, RC-IG BT. Thus,for example, each one of the current switches may c omprise agate electrode, and by providing control signals to the gateelectrodes,turning-on and turning-offthe current switchescan be controlled. A turn-on state may refer to a c onductingstate of the respective current switch, and a turn- off statemay refer to a blocking state of the respective swi tch. Allthe current switches may be of the same type, or di fferentkinds of current switches may be combined with each other.According to at least one embodiment, the power con vertersystem includes a plurality of electromagnetic sens ors, suchasmagneticfield probesorcurrentsensors.Itis possiblethat there are different types of electromagnetic s ensors.Otherwise, all the electromagnetic sensors can be o f the sametype. P2023,1187 WO E / P230049WO01 November29,2023 -3 -According to at least one embodiment, the power con vertersystem includes a control unit. For example, the co ntrol unitis a computing device. It is possible that the cont rol unitcan be programmed using hardware and / or software. T he controlunit may be connected to the gate electrodes by a c ontrolline and may thus provide gate electrode signals to thecontrol switches. Moreover, the control unit may re ceivesensordata from the electromagneticsensors.According to at least one embodiment, the method co mprisesthe step of: switching, by the control unit, the cu rrentswitches. Hence, the control unit may produce and m ay sendcontrol signals to the current switches. Especially , theconverter and its controlling may form a Modular Mu ltilevelConverter, MMC. Concerning the MMCs, the disclosure contentof document A. Nami et al. as cited above is includ ed byreference.According to at least one embodiment, the method co mprisesthe step of: measuring, by the electromagnetic sens ors,radiated and / or conducted electromagnetic noise cau sed by theswitching of the current switches. Thus, the switch ingcauses, for example, radio waves in the low frequen cy, mediumfrequency, high frequency and / or very high frequenc y rangeemitted into the air, and said radio wave radiation isdetected by at least some of the electromagnetic se nsors.According to at least one embodiment, the method co mprisesthe step of: modifying, by the control unit, turn-o n timesand turn-offtimesofatleastsome ofthe current switchesso that the radiated and / or conducted electromagnet ic noiseof the power converter system is reduced in at leas t one P2023,1187 WO E / P230049WO01 November29,2023 -4 -frequency band. For example, by modifying the turn- on timesand turn-off times as previously set, modified turn -on timesand turn-offtimesare determined. In otherwords,bymodifying the turn-on timesand the turn-off times the radiated and / or conducted noise is re ducedcompared to the switching time when the measuring t heelectromagnetic noise is performed. The modifying i s done,for example, in a way to maximize a number of coinc idingturn-on and turn-off events so that destructive int erferenceof electromagnetic radio waves can be maximized, es peciallyin the far field of the power converter system conc erningsaid radio waves, without significantly hampering e fficiencyofthe powerconvertersystem.For example, prior to the step of the modifying, by thecontrol unit, the turn-on times and the turn-off ti mes, at atime t 1, there is a switching pattern C t1 of turn-on timesTI 1..TI Nand of turn-off times TO 1..TO N, wherein N is thenumberofthe currentswitches.Forthisswitching patternCt1 , a radiated and / or conducted noise S t1 , that is, S )is emitted and measured. By means of the modifying, at alater time t 2 the switching pattern C t1 is changed to theswitching pattern C t2 with modified values TI 1’..TI N’ andTO1’..TO N’, and the modifying is done so that S t2 (Ct2 ) <St1 (Ct1 ). It is possible that during the modifying there i s anumber if intermediate switching patterns C with maybeSt1 (Ct1 ) < S int (Cint ). Thus, at intermediate steps in courseof the modifying, the radiated and / or conducted noi se maytemporarily increase, however, a continuous reducti on in theradiated and / or conducted noise during the modifyin g may also P2023,1187 WO E / P230049WO01 November29,2023 -5 -be possible until a switching pattern with a minimu m radiatedand / orconducted noise hasbeen found.It is noted that times t 1 and t 2 may be on different, thatis,much largertime scalesthan the turn-on times and turn-off times TI 1..TI N, TO 1..TO N, TI 1’..TI N’ while the latter can be on the sub-ms timescale, th e times t 1and t 2 may differ from one another by seconds, minutes,hours,daysoreven months.According to at least one embodiment, the method co mprisesthe step of:controlling,bythe controlunit,the currentswitches according to the modified turn-on times an d turn-offtimes. That is, the controlling is done with the ne wswitching pattern C 1’..TO N’), and S t2 (Ct2 ) <St1 (Ct1 ).The method steps of switching, measuring, modifying andcontrolling may be done in a looped manner. Especia lly,during modifying itispossible thatthe measuring isperformed a plurality of times in order to determin e C t2 withthe reduced noise S t2 .In at least one embodiment, by means of the operati ng methodwhich a power converter system is operated, the pow erconverter system includes a plurality of current sw itches, apluralityofelectromagneticsensorsand a control unit,the method comprising:- switching, by the control unit, the current switc hes;- measuring, by the electromagnetic sensors, radiat ed and / orconducted electromagnetic noise caused by the switc hing ofthe currentswitches; P2023,1187 WO E / P230049WO01 November29,2023 -6 -- modifying, by the control unit, at least one of t urn-ontimes,turn-offtimes,turn-on durations,turn-off durations orslopesofatleastsome ofthe currentswitches so thatthe radiated and / or conducted electromagnetic noise of thepower converter system is reduced in at least one f requencyband;and- controlling, by the control unit, the current swi tchesaccording to the modified turn-on times and turn-of f times.Thus, the power converter system may be an electrom agneticcompatibility,EMC,filter-lessModularMultilevel Converter,MMC. The operating method described herein can thus beapplied, for example, to high voltage direct curren t, HVDC,converters.HVDC converters may be based on voltage source conv erters,VSC, consisting of many semiconductor switching cel ls. Theconverters are MMCs. The cells are connected in ser ies with abusbar and stacked in a so-called valve structure a sdepicted, for example. Similar arrangements might b einstalled in flexible AC transmission system, FACTS ,converters.The switching events of power semiconductor devices withinthe cells generate high frequency currents, leading toconsiderable radiated and / or conducted electromagne tic noisein a wide frequency range. This noise is partly rad iated bythe converter station, and it may interfere with se condaryelectronic or communication systems in the vicinity of thestation, where it can cause EMC issues. For this re ason, HVDCconverters should comply with certain EMC requireme nts. P2023,1187 WO E / P230049WO01 November29,2023 -7 - With the method and system described herein,theelectromagnetic noise emitted can be reduced. Other measures,see below, mainly include the installation of hardw are EMCfilters and / or shielding measures. Hardware filters come withmaterial,engineering,and installation cost.They produceunwanted losses, require space for installation and exhibitinherent reliability risks. Shielding requires a lo t ofeffort as big parts of the converters must be enclo sed bywell-conducting, high frequency shields. This comes with highmaterial cost and significant installation time. Mo reover, itposes the risk for installation mistakes and, accor dingly,potential commissioning delays. With the method and systemdescribed herein, electromagnetic noise reduction c an beachieved without additional hardware, such as EMC f ilters orshielding,to overcome these issues.Alternative solution of electromagnetic noise mitig ation inHVDC and FACTS converters include EMC filters and a t leastpartial shielding of the converter. EMC filters for HVDC areoften based on air coil reactors. Those high freque ncyreactors can be installed in series to the switchin g cells.Each converter arm comprises at least one high freq uencyreactor, which is typically installed on the AC end of thearm. Disadvantages of those filters include high ma terialcost, their footprint, a hardly predictable perform ance inthe high frequency range, significant losses, and s ubstantialengineering work for each project. In addition to t he highfrequency reactors, ferrite filters in the valve st ructuresmay be used to attenuate resonancesabove 3 MHz.The idea of the present method and system is to mod ify theswitching pattern and / or the firing signals for theindividualcells,respectively,of,forexample,a MMC P2023,1187 WO E / P230049WO01 November29,2023 -8 -converter in such a way that the electromagnetic no isegenerated bythe converterisreduced.Atthe same time,theactual converter operation shall not be impaired. T he problemto be solved might be formulated as an optimization problemfinding the optimalswitching pattern C: in which S i denotes the electromagnetic noise at a certainlocation iasa function offrequencyf,depending on theswitching pattern C. w i is a certain weighting function and Ndenotes the total number of locations for monitorin g theelectromagneticnoise.The idea of the method described herein shall be de scribed bya simple example: Consider two individual switching cells, inthe following named cell1 and cell2,and imagine both cellsare continuously switching on and off a certain vol tageindependently from each other. The associated volta gewaveforms are considered to be trapezoidal. The swi tchingoperation generates a high frequency current in the converterarms, leading to electromagnetic near and far field s. Theidea of this invention is to synchronize the switch ing of atleast two cells such that the electromagnetic field sgenerated by individual switching operations at lea st partlycancel each other. Hence, a turn-off switching inst ance ofswitch 1 is synchronized with a turn-on switching i nstance ofswitch 2.Here,the resulting magneticnearfields producedby the switching cells are similar, but in antiphas e. Addingboth contributions significantly reduce the magneti c field atthe particular observation point. When transforming the timedomain signals into frequency domain, the maximum n oise level P2023,1187 WO E / P230049WO01 November29,2023 -9 -reduces significantly. Accordingly, noise reduction can beobtained withoutthe use ofhardware EMC filters.The method is not only applicable for the case of p airs ofsynchronized switching cells as stated in the simpl e examplebutcan also considerthe generalcase ofmultiple cells being synchronized fornoise reduction.The idea of the method described herein may refer t o analgorithm that combines the initial converter contr ol dataand EMC data, with which it creates a modified swit chingpattern that minimizes the actual converter EMC noi se levels.The EMC data can be of different types, for example :-An EMC modelofthe converterthatestimatesEMC noise levelsthrough calculationsorsimulations;- electromagnetic measurement data obtained from anelectromagnetic sensor network installed at the act ualconverter;and / or- a trained machine learning EMC model based on sim ulatedand / ormeasured EMC data.Thus, a first embodiment refers to the power conver ter systemcomprising a piece of control software in the conve rtercontrol hardware. This software is an implementatio n of thealgorithm that adapts the switching pattern in such a waythat the total EMC noise levels are reduced as desc ribedbefore. The embodiment may include the above-mentio nedalgorithm that gets input parameters from the MMC c onvertercontroller and from the EMC emission model and that creates amodified switching pattern that minimizes the actua l EMCemission while retaining the required converter per formance. P2023,1187 WO E / P230049WO01 November29,2023 -10 - A second embodimentrefersto the operating method forproviding the EMC data to the algorithm, which incl udes, forexample:a) providing a sensor network comprising multiple E M sensorsinside and outside the converterand which remains installedfor the entire operation life cycle of the converte r;b) providing a sensor network comprising multiple E M sensorsinside and outside the converter and which is tempo rarilyinstalled, for example, during commissioning for in itialcollection of the required EMC data, and which is t henremoved aftercommissioning,forexample;the same mayapply formaintenance;c) providing a virtual EMC model of the converter t hatprovides the required EMC data based on estimations throughanalytical, numerical or artificial intelligence, A I,modeling; d)providing a combination ofa),b)and c),where the sensornetwork is used to augment the performance of the E MC model.For example, to perform the optimization problem ou tlinedabove, it is proposed to install a sensor network c omprisingmultiple electromagneticsensorsin and around the convertersystem’s switches. The sensors monitor the electrom agneticnoise and provide corresponding data as input for t hecontrolling of the switches. Several E / H field sens ors canthus be deployed in and outside of a HVDC converter hall. Inaddition,severalcurrentsensorson the DC and AC buses,respectively, can be implemented. The sensor networ k isconnected to a control unit. The control unit calcu lates andtransmits the firing signals for the switching even ts to theswitching cells in the valve structures. Taking the sensorsignals as input, the control unit optimizes the sw itchingpattern such that the electromagnetic noise detecte d by the P2023,1187 WO E / P230049WO01 November29,2023 -11 -sensor network is minimized without compromising th econverteroperation.In thisway,the controlunit learnshowto reduce the electromagnetic noise. The system mayaccordingly be configured as a self-adapted or self -learningsystem.There are many implementation variants and features possible,forexample: -Sensornetworksetup● At least after commissioning, the sensor network m ightconsist of or may comprises current sensors impleme nted onlyon the buses leaving the converter hall. With that, the noiseradiated from the AC and DC yard can be reduced.● Only near field sensors are implemented in the val ve hallifthe noise in the valve hallshallbe reduced.● Only field sensors in the AC or DC yard might be i nstalled.● Far field sensors outside the converter station mi ght beused.Those sensorsmightbe temporarilyinstalled and onlybe used once for determining the firing instances u ndercertain load conditions.● The sensor network is either installed permanently ortemporarily.● All possible combination of the setups described a bove arefeasible. -Sensornetworkhardware ● The sensorscan be connected byglassfibers.● The sensors can be connected by coaxial, high freq uencycables.● Typical high frequency antennas, such as loop or l og-perantennasmightbe used asfield sensors.● Commercial electromagnetic field probes might be u sed as P2023,1187 WO E / P230049WO01 November29,2023 -12 - field sensors.● Current transformers or Rogowski coils might be us ed ascurrentprobes. -Controlsignals ● The controlsignalsmightbe calculated such that the noisein the entire frequency range of interest is reduce d.● The controlsignalsmightbe calculated such that the noiseis reduced only in a defined number of frequency ba nds, forexample,onlyatpronounced resonances.● The calculation of firing signals might be done in real-time during converter operation. With that, all ope rationconditions can be tackled. Doing so can be consider ed asself-adapted orself-learning filtering.● The optimization problem used for optimizing the s witchingpattern can be done using established optimizationalgorithms, such as gradient descent or evolutionar yoptimization algorithms.● The optimization might be enhanced by machine lear ningalgorithms.Some benefits of the method and system described he rein canbe summarized asfollows:- No hardware filters or only a reduced amount of h ardwarefiltersisrequired: ● Massive costreduction asmaterial,engineering, transportation,and installation costisreduced.● Higher reliability as aging is not a concern for d igitalfilters.● Reduced filter footprint, leading to less converte rfootprint. ● Lesslosses.- Automated and real-time tuning of filtering prope rties: P2023,1187 WO E / P230049WO01 November29,2023 -13 -● Filtering and engineering efficiency is enhanced a scritical frequency ranges are determined during con verteroperation and then filtered out accordingly. This i s incontrast to the typical EMC design procedure, in wh ich filterlayout is done during the design phase of the conve rter.● Filtering can be achieved independently of a conve rtertype, layout, and generation. The “filter” adapts i tself tothe environmentso thatlessdesign effortforEMC filtering,significantly less engineering work in the planning phase isrequired. ● The nextgeneration ofsemiconductordeviceswith differentnoise footprint can be treated conveniently, withou t changinghardware filters.- The data recorded by the sensor network can be us ed forother purposes, such as health and condition monito ring,predictive maintenance,and so on.In one embodiment, a modular multilevel converter e xhibitinga controlunitisprovided which isconnected to a networkofelectromagnetic sensors. For example, the converter controlisadapted according to the sensorsignalsofthe electromagneticsensors.In one embodiment, the converter control is adapted such thatthe electromagnetic noise measured by the sensors i sminimized wherein reference signals can be taken in toaccount. For example, the reference signals are rec orded bycurrent sensors, or the reference signals are recor ded by E-field or H-field probes, respectively, or the refer encesignals are recorded by both, current sensors and f ieldprobes. P2023,1187 WO E / P230049WO01 November29,2023 -14 -According to at least one embodiment, the power con vertersystem comprises at least 100 or at least 300 or at least1000 of the current switches. Alternatively or addi tionally,said number is at most 10 4 or is at most 3000.According to at least one embodiment, the current s witches orsmall groups of the current switches are electrical lycontrollable independent of one another. The term ‘ smallgroup’ refers, for example, to at most six or at mo st four orat most two of the current switches. Hence, for exa mple, anumberofindividualgate controlsignalsproduced bythecontrol unit and provided to the current switches i s the sameas the number of current switches or is only slight ly lower,forexample,isatleast20% orisatleast50% or isat least90% ofthe numberofthe controlswitches.According to at least one embodiment, turn-off dura tions andturn-on durations,from 5% to 95% transmittance of therespective current switch, are at least 0.1 µs or a t least1 µs or are at least 2 µs. Alternatively or additio nally,this value is at most 10 µs or at most 7 µs or at m ost 5 µs.According to at least one embodiment, the turn-on t imesand / or turn-off times of one or some or most of the currentswitches are modified by at least 0.1% or by at lea st 0.5% orby at least 2% of the turn-off durations and the tu rn-ondurations. Alternatively or additionally, said valu e is atmost 60% or at most 30% or at most 10% or at most 3 % of theturn-offdurationsand the turn-on durations.That is,the turn-on timesand / orturn-offtimesmaybe shifted bylessthan the duration of the turn-off or the turn-on pr ocess. P2023,1187 WO E / P230049WO01 November29,2023 -15 -According to at least one embodiment, one or some o r most ofthe turn-off durations and / or the turn-on durations arechanged.Thatis,alternativelyoradditionallyto the modifying the turn-on timesand / orturn-offtimes, the turn-off durations and / or the turn-on durations may be m odified.It is also possible that the turn-off durations and / or theturn-on durations remain unchanged so that only the turn-ontimes and / or turn-off times are modified. The turn- offdurations and the turn-on durations may also be ref erred toasfalltime and rise time,respectively.According to at least one embodiment, a slope of on e or someor most of the turn-off events and / or the turn-on e vents ischanged.Thatis,alternativelyoradditionallyto themodifying the turn-on times and / or turn-off times a ndalternativelyoradditionallyto the modifying the turn-on durationsand / orturn-offdurations,the slopesof the turn-off events and / or of the turn-on events may be modi fied. Theslope maynotonlyreferto a gradient,butmayin generalrefer to a shape of a time-voltage and / or time-curr ent curveofthe respective turn-off / on event.According to at least one embodiment, the turn-on t imesand / or turn-off times of one, some or all of the cu rrentswitchesare modified bya time difference ∆T having a lowerlimit ∆Tlow of at least 1 ns or of at least 10 ns or of atleast 1 µs. Alternatively or additionally, said tim edifference ∆T hasan upperlimit ∆Tupofatmost1 msorofat most 0.1 ms or of at most 5 µs or at most 2 µs o r at most1 µs.Forexample,itappliesforatleastsome of the currentswitchesthat P2023,1187 WO E / P230049WO01 November29,2023 -16 - for at least one i ∈ [1; N] ℕ. The N current switches arecorrespondinglynumbered and ordered from 1 to N.According to at least one embodiment, the electroma gneticsensors include at least one of a near field electr omagneticradiation sensor, a far field electromagnetic radia tionsensor or a cable-bound current sensor at an altern atingcurrent bus and / or at a direct current bus of the p owerconverter system. Hence, different kinds of sensors can becombined with each other.According to at least one embodiment, a number of t he currentswitches exceeds a number of the electromagnetic se nsors byatleasta factorof10 orbyatleasta factorof 20 orbyat least a factor of 50. Alternatively or additiona lly, saidfactorisatmost500 orisatmost200.Thus,the numberofcurrent switches exceeds the number of sensors sign ificantly.Thisappliesespeciallyforthe commissioned power converter system.According to at least one embodiment, the modificat ion, bythe control unit, of the turn-on times and the turn -off timesof the at least some of the current switches is bas ed on themeasuring the radiated and / or conducted electromagn etic noiseand is also based on at least one of analytical mod elling,numericalmodelling or‘blackbox’modelling based on,forexample, artificial intelligence , of the power convertersystem. This allows reducing the number of electrom agneticsensors and enables efficient handling of the possi bly under-determined optimization problem concerning setting the turn- on timesand the turn-offtimes. P2023,1187 WO E / P230049WO01 November29,2023 -17 -According to at least one embodiment, the modifying , by thecontrol unit, the turn-on times and the turn-off ti mes ofone,some orallthe currentswitchesisperformedpermanently during regular operation of the power c onvertersystem. Hence, the power converter system can respo nd nearlyin realtime on situationalchangesthatinfluence the emission ofnoise,like converterload.According to at least one embodiment, the modifying , by thecontrol unit, the turn-on times and the turn-off ti mes ofone, some or all of the current switches is perform ed duringcommissioning and / or maintenance the power converte r system.For example, the switching pattern of the current s witches isdefined during the commissioning and / or maintenance and thepower converter system is subsequently used without furtherchanges on the turn-on times and the turn-off times so thatthe modifying may be limited to the commissioning a nd / ormaintenance.According to at least one embodiment, part or all o f theelectromagnetic sensors are removed after the modif ying, likeduring the commissioning or during maintenance, andoptionallypriorto regularoperation ofthe power convertersystem. That is, the full number of the electromagn eticsensors may be present only during the modifying, i ncludingthe required measuring within the modifying.According to at least one embodiment, a lateral ext ent and / ora height extent along one or a plurality of directi ons of thepower converter system’s current switches all toget her is atleast10 m orisatleast20 m.Alternativelyor additionally,said lateralextentisatmost100 m orisat P2023,1187 WO E / P230049WO01 November29,2023 -18 -most 60 m. Hence, the current switches may be sprea d across arelativelylarge area.According to at least one embodiment, the modifying , by thecontrol unit, the turn-on times and the turn-off ti mes of theat least some of the current switches is relative t osynchronous switching or linear-cascade switching o f all thecurrent switches assigned to a specific second elec tric line.Hence, not all the current switches are turned on o r turnedoff at the same time, but at different times, and i t ispossible that an intermediate one of the current sw itches isturned on oristurned offlaterthatthe adjacent onesofthe current switches along the specific second elec tric line.For example, there are three of the second electric lines incase ofthree-phase alternating current. According to atleastone embodiment,the atleast onefrequency band includes at least part of the freque ncy rangefrom 9 kHzto 300 MHz.Hence,the noise emitted by the powerconverter system and reduced by the method describe d hereinmay be one or a plurality of very low frequency, VL F, radiowaves, low frequency, LF, radio waves, medium frequ ency, MF,radio waves,high frequency,HF,radio waves,very highfrequency, VHF, radio waves, as defined by the Inte rnationalTelecommunication Union,ITU.According to at least one embodiment, the power con vertersystem is free of any hardware high frequency filte rs. Forexample, there are no air coil reactors with parall elresistance in the powerconvertersystem. P2023,1187 WO E / P230049WO01 November29,2023 -19 -According to at least one embodiment, the power con vertersystem converts direct current, DC, into alternatin g current,AC,orvice versa.According to at least one embodiment, the alternati ng currenthandled by the power converter system is at least 0 .2 kA orat least 0.5 kA. Alternatively or additionally, sai d currentis at most 15 kA or is at most 5 kA or is at most 2 kA.According to at least one embodiment, the alternati ng currenthandled by the power converter system has an effect ive valueof at least 0.1 MV or of at least 0.2 MV. Alternati vely oradditionally, the effective value of the voltage is at most1.2 MV orisatmost0.8 MV orisatmost0.6 MV. A powerconvertersystem isadditionallyprovided. Bymeans ofthe operating method asindicated in connection with atleast one of the above-stated embodiments, the powe rconverter system is operated. Features of the power convertersystem are therefore also disclosed forthe method and vice versa.In at least one embodiment, the power converter sys temcomprises: -a pluralityofcurrentswitches; -a pluralityofelectromagneticsensors;and -a controlunit, wherein- the control unit is configured to switch the curr entswitches;- the electromagnetic sensors are configured to mea sureradiated and / or conducted electromagnetic noise cau sed by theswitching ofthe currentswitches;and P2023,1187 WO E / P230049WO01 November29,2023 -20 - -the controlunitisconfigured to modifyturn-on timesandturn-off times of at least some of the current swit ches sothatthe radiated and / orconducted electromagnetic noise ofthe power converter system is reduced in at least o nefrequency band, and is further configured to contro l thecurrentswitchesaccording to the modified turn-on timesand turn-offtimes. Forexample,the powerconverterisan MMC.A power converter system and an operating method de scribedherein are explained in greater detail below by way ofexemplary embodiments with reference to the drawing s.Elements which are the same in the individual figur es areindicated with the same reference numerals. The rel ationshipsbetween the elements are not shown to scale, howeve r, butrather individual elements may be shown exaggerated ly largeto assistin understanding. In the Figures:Figure 1 shows a schematic block diagram of an exem plaryembodimentofa powerconvertersystem described herein,Figure 2 shows a schematic block diagram of an exem plaryembodiment of an operating method by means of whichpowerconvertersystemsdescribed herein are operated,Figure 3 is a schematic top view of an exemplary em bodimentofa powerconvertersystem described herein, P2023,1187 WO E / P230049WO01 November29,2023 -21 -Figure 4 is a schematic top view of a valve hall of anexemplaryembodimentofa powerconvertersystem described herein,Figure 5 is a schematic electric diagram of current switchesfor exemplary embodiments of power converter system sdescribed herein,Figures 6 and 7 are schematic representations of el ectricoperation data ofan exemplaryembodimentofan operating method forpowerconvertersystems described herein,andFigure 8 is a schematic top view of an exemplary em bodimentofa powerconvertersystem described herein.In Figure 1, an exemplary embodiment of a power con vertersystem 1 is schematically drawn. For example, the p owerconvertersystem comprisesan MMC.The power converter system 1 thus comprises a plura lity ofcurrent switches 21, 22. For example, the current s witches21, 22 are IGBTs each having an own gate electrode. Inaddition,the powerconvertersystem 1 comprisesa plurality ofelectromagneticsensors3 and a controlunit4. Contraryto what is schematically illustrated in Figure 1, t he controlunit 4 may be split into a couple of sub-unites whi ch nay notnecessarilybe located atthe same place.For example, the current switches 21, 22 are connec ted to thecontrolunit4 bycontrollines42.Itispossible thateach one ofthe currentswitches21,22 isindividually connectedto the control lines 42. The electromagnetic sensor s 3 may be P2023,1187 WO E / P230049WO01 November29,2023 -22 -connected to the control unit 4 with a data line 43 . Thecontrol line 42 and the data line 42 may be wire-ba sed.Otherwise, these lines, especially the data line 42 , may atleastpartiallybe wirelesslines.In one example, the power converter system 1 is a H VDC systemconfigured for an AC of 1 kA to 5 kA and / or of an A C voltageof100 kV to 1.200 kV.A powerthe powerconverter system 1 isconfigured foris,forexample,atleast0.1 GW oratleast 0.5 GW or is alternatively or additionally at most 5 GWor is at most 3 GW. Hence, large electric powers ca n behandled bythe powerconvertersystem 1.An embodiment of an operating method of the power c onvertersystem 1 isexplained in connection with Figure 2. In method step S1,the controlunit4 switchesthe currentswitches 21, 22. This is done, for example, the cur rentswitches 21, 22 are controlled with a switching pat tern C t1of turn-on times TI 1..TI Nand of turn-off times TO 1..TO N,wherein N is the number of the current switches 21, 22.In method step S2, the electromagnetic sensors 3 me asureradiated and / or conducted electromagnetic noise cau sed by theswitching ofthe currentswitches21,22.Forthis purpose, there can be differentkindsofsensorsatvarious locations.According to method step S3, the control unit 4 mod ifies theturn-on times and turn-off times of at least some o f thecurrentswitches21,22.Bydoing so,the radiated and / orconducted electromagnetic noise of the power conver ter system1 is reduced in at least one frequency band. For ex ample, theswitching pattern C t1 results in a radiated and / or conducted P2023,1187 WO E / P230049WO01 November29,2023 -23 -noise S t1 . In step S3, a switching pattern C t2 is determinedwith modified values TI 1’..TI N’ and TO 1’..TO N’, of the turn-on times and the turn-off times. the switching patt ern C t2results in a radiated and / or conducted noise S t2 , andSt2 (Ct2 ) < S t1 (Ct1 ). To achieve this, the switching patternmay be changed in an iterative manner and the emitt ed noisemay be measured various times during iteration to g etswitching pattern C t2 so that steps S2 and S3 may follow oneanother in a looped manner until switching pattern Ct2 isfound. The turn-on times and the turn-off times are , forexample,between 1 µsand 7 µs.The changesin the turn-ontimes and the turn-off times are, for example, betw een 1 nsand 2 µs. For example, there are at least 500 or at least1000 ofthe currentswitches21,22.Then, in method step S4 the control unit 4 controls thecurrent switches 21, 22 according to the modified t urn-ontimes and turn-off times of the switching pattern C t2 .Method steps S1 to S4 may be performed in the state d orderduring commissioning ofthe powerconvertersystem 1 only,orthese steps are repeated after certain time interva ls and / orafter an increase of the emitted noise has been det ected orafter being manually triggered, for example. The sa me mayapply for maintenance of the power converter system 1.By means of this method, the radiated and / or conduc ted noise,especiallyradio wavesbetween,forexample,9 kHz and 300 MHz,can be reduced.In Figures 3 and 4, another example of the power co nvertersystem 1 isshown.The currentswitches21,22 may be P2023,1187 WO E / P230049WO01 November29,2023 -24 -arranged in groups 2, also referred to as switching cells.For each second electric line 52, which may corresp ond to thethree phases of an alternating current, there can b e one or apluralityofthe groups2.These electriclines52 can beoutput buses or also input buses. As in input bus o r as anoutput bus, there is a first electric line 51 which islikewise a directcurrentline.The current switches 21, 22 are preferably individu allyaddressable so thatnotjustthe groups2 buteach one ofthecurrent switches 21, 22 can be turned off and turne d on bythe control unit 4 in principle independently of th e othercurrentswitches21,22. The groups2 and the controlunit4 are optionally located invalve hall 61 which may be electromagnetically shie lded tosome extent. However, especially the second lines 5 2 arelocated also outside the valve hall 61 and may thusconstitute dominant radiating structures 7 of the s ystem 1.Thus,especiallybythe radiating structures7, electromagneticnoise N isirradiated.The noise 7 consists, forexample,predominantlyofradio waves.Optionally, the radiating structures 7 can compriseadditionalelectricequipment62 outside the valve hall61.Such additional electric equipment 62 includes, for example,transformers.Without the method described herein in which, for e xample,the numberofturn on eventshaving a simultaneous turn offevent is maximized, in the valve hall 61 there is t ypicallythe need for EMC filter reactors 63, for example, o ne reactor63 for each one of the second lines 52. By using th e method P2023,1187 WO E / P230049WO01 November29,2023 -25 -described herein, no such hardware filters 63 or on lystronglysimplified hardware filtersare required.In Figure 4 it is illustrated that the valve hall 6 1 isrelatively large. For example, in a direction perpe ndicularto a length direction of the individual electric li nes, alateral extent L1 of the current switches is at lea st 20 mand isatmost80 m.Forexample,a lateralextent L2 including two ofthe groups2 ofa specificone of theelectric lines is at least 6 m and at most 30 m. Ac cordingly,the control unit 4 may consider the positions of th e currentswitches 21, 22 to compensate for differences in si gnalrunning timesto drive the currentswitches21,22 via the controlline 42. Otherwise,the same asto Figures1 and 2 mayalso applyto Figures3 and 4,and vice versa. In Figure 5 itisillustrated thateach one ofthe currentswitches 21, 22 comprises its own gate electrode 23 addressedby an own control line 43. Hence, the switching beh avior canbe adapted on a currentswitch level.A unit based on the two switches 21, 22 as illustra ted inFigure 5 may be referred to as a half-bridge cell o r as thegroup 2,forexample.Such currentswitches21,22 and cellscan be used in all the examples of the power conver ter system1.Otherwise, the same as to Figures 1 to 4 may also a pply toFigure 5,and vice versa. P2023,1187 WO E / P230049WO01 November29,2023 -26 -In Figure 6, a potential modified switching behavio r for onlytwo of the current switches 21, 22 is schematicallyillustrated. According to Figure 6, left side, a fi rst one ofthe current switches 21 is turned off and simultane ously asecond one of the current switches 22 is turned on. Duringturn on, a drop of a voltage U decreases from aroun d 1 kV tovirtually zero within a couple of µs. The correspon dingstrength ofthe magneticfield H in the nearfield foreach one ofthe currentswitches21,22 individuallyisillustrated in Figure 6, right side. As can be seen , becauseof the turning off and turning on, respectively, th ere arestrong oscillations of the magnetic field H for aro und 20 µs.For the far field, the resulting amplitudes A are s hown inFigure 7,in the frequencyrange from 100 Hzto 10 MHz.Incase of conventional switching M1 in which the swit chinginstances are separated by more than 30 µs, the amp litude Ais about 20 dB larger than in case of the adapted s witchingM2 realized by means of the method described herein asindicated in Figure 6, left side. Thus, radiated an d / orconducted noise can greatlybe reduced. In Figures6 and 7 itisillustrated thatonlythe turn-off timesand the turn-on timesare modified while the falltimes and the rise times,thatis,the turn-on durations and theturn-off durations, have not been modified. Further thegeneral shape of the switching events, like the slo pe, hasneither been modified. However, alternatively or ad ditionallyto the modifying the turn-on timesand / orturn-off timesand alternativelyoradditionallyto the modifying the turn-on durationsand / orturn-offdurations,the shapesof the turn-off events and / or of the turn-on events may be modi fied aswell. P2023,1187 WO E / P230049WO01 November29,2023 -27 -Otherwise, the same as to Figures 1 to 5 may also a pply toFigures6 and 7,and vice versa.Figure 8 shows a further example of the power conve rtersystem 1. There is the DC bus 51 and the three AC b uses 52.Each one of the current switches 21, 22 is connecte d to theDC bus 51 and to one of the AC buses 52. Further, t he currentswitches 21, 22 are connected with the control unit 4 bymeans of the control line 42. As an option, the con trol unit4 may be placed outside the valve hall 61. For exam ple, thereare 1 x 10 3 of the current switches 21, 22.The power converter system 1 comprises different ki nds of thesensors 3. For example, there are near field electr omagneticradiation sensors 31. These sensors 31 are sensitiv e to radiowaves, for example. The near field sensors 31 may b e placedat different locations within the valve hall 61. Fo r example,there are at least two and / or at most 15 of the nea r fieldsensors 31. By way of example, there is one or a pl urality ofthe near field sensors 31 per AC bus 52. A distance betweenthe near field sensors 31 and the closest current s witches21,22 is,forexample,atmost20 m oratmost10 m orat most3 m.Optionally, there is one or a plurality of far fiel delectromagneticradiation sensors32.Forexample, the farfield sensors 32 are located outside the valve hall 61.Especially,there isatleastone and / orthere are atmostfive or at most two of the far field sensor 32. A d istancebetween the far field sensors 32 and the closest cu rrentswitches 21, 22 is, for example, at least 0.1 km or at least0.3 km and / or at most 3 km or at most 0.5 km. The o ne or the P2023,1187 WO E / P230049WO01 November29,2023 -28 -at least one far field sensor 32 may be sensitive f or radiowaves,too.As a further option, there are wire-bound current s ensors 33.For example, there is one or at least one current s ensor 33per bus 51, 52. It is possible that the current sen sors 33are located outside the valve hall61 orotherwise inside thevalve hall 61 or at an exit of the buses 51, 52 out of thevalve hall 61. The current sensors 33 are sensitive , forexample,specificallyforfrequenciesabove 9 kHz.The different kind of sensors 31, 32, 33 are prefer ablypresentin combination.It is possible that there are at most 20 or at most ten ofthe electromagnetic sensors 31, 32, 33. Hence, a nu mber ofthe current switches 21, 22 is about a factor of 1 x 10 2larger than a number of the electromagnetic sensors 31, 32,33. In combination with numeric or analytic calcula tionsand / or by using a macro-model, possibly supported b yartificialintelligence,the switching pattern canefficiently by optimized although there is only the relativesmall number of electromagnetic sensors 31, 32, 33. Hence,using modelling and sensor data allows for individu allyadjustthe turn-on timesand the turn-offtimesof the large numberofcurrentswitches21,22 individually.It is possible that all or part of the electromagne ticsensors 31, 32, 33 are permanently installed. For e xample,only the electromagnetic sensors 31, 33 are permane ntlyinstalled but not the far field electromagnetic rad iationsensor 32. Thus, possibly the at least one far fiel d P2023,1187 WO E / P230049WO01 November29,2023 -29 -electromagnetic radiation sensor 32 is present only duringcommissioning or maintenance of the power converter system 1.Otherwise, the same as to Figures 1 to 7 may also a pply toFigure 8,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.

[0002] P2023,1187 WO E / P230049WO01 November29,2023 -30 - ListofReference Signs 1 powerconvertersystem 2 group ofcurrentswitches 21 currentswitch 22 currentswitch 23 gate electrode 3 electromagneticsensor 31 nearfield electromagneticradiation sensor 32 farfield electromagneticradiation sensor 33 currentsensor 4 controlunit 42 controlline 43 data line51 fist electric line, direct current bus and input bus52 second electric line, alternating current bus an d outputbus 61 valve hall 62 additionalelectricequipmentoutside the valve hall63 electromagnetic compatibility, EMC, filter react or7 radiating structures A amplitude f frequency H strength ofthe magneticfield H L.. lateralextent M1 conventionalswitching M2 adapted switching N radiated noise S.. method step t time U voltage

Claims

P2023,1187 WO E / P230049WO01 November29,2023 -31 - PatentClaims1. A operating method by means of which a power con vertersystem (1)isoperated,the powerconvertersystem (1) includesa pluralityofcurrentswitches(21,22), aplurality of electromagnetic sensors (3, 31, 32, 33 ) and acontrolunit(4),the method comprising:- switching, by the control unit (4), the current s witches(21,22);- measuring, by the electromagnetic sensors (3, 31, 32, 33),radiated and / or conducted electromagnetic noise cau sed by theswitching ofthe currentswitches(21,22); -modifying,bythe controlunit(4),atleastone ofturn-on times,turn-offtimes,turn-on durations,turn-off durations orslopesofatleastsome ofthe currentswitches (21,22)so that the radiated and / or conducted electromagnet ic noiseofthe powerconvertersystem (1)isreduced in at leastone frequencyband;and- controlling, by the control unit (4), the current switches(21, 22) according to the modified turn-on times an d turn-offtimes. 2.The method according to the preceding claim,wherein the power converter system (1) comprises at least 100ofthe currentswitches(21,22),and said current switches (21,22)are electricallycontrollable independent ofone another.

3. The method according to any one of the preceding claims,wherein turn-off durations and turn-on durations, f rom 5% to95% transmittance of the current switches (21, 22), arebetween 1 µsand 10 µs,wherein the turn-on times and turn-off times of the at leastP2023,1187 WO E / P230049WO01 November29,2023 -32 - some ofthe currentswitches(21,22)are modified byatleast 0.1% of the turn-off durations and the turn-o ndurations.

4. The method according to any one of the preceding claims,wherein the electromagnetic sensors (3, 31, 32, 33) include anear field electromagnetic radiation sensor (31), a far fieldelectromagnetic radiation sensor (32) and a cable-b oundcurrent sensor (33) at an alternating current bus ( 52) of thepowerconvertersystem (1).

5. The method according to any one of the preceding claims,wherein a number of the current switches (21, 22) e xceeds anumber of the electromagnetic sensors (3, 31, 32, 3 3) by atleasta factorof10.

6. The method according to any one of the preceding claims,wherein the modifying, by the control unit (4), the turn-ontimes and the turn-off times of the at least some o f thecurrent switches (21, 22) is based on the measuring theradiated and / or conducted electromagnetic noise and is alsobased on at least one of analytical modelling, nume ricalmodelling or artificial intelligence modelling of t he powerconvertersystem (1).

7. The method according to any one of the preceding claims,wherein the modifying, by the control unit (4), the turn-ontimes and the turn-off times of the at least some o f thecurrentswitches(21,22)isperformed permanently duringregular operation of the power converter system (1) .

8. The method according to any one of the preceding claims,wherein the modifying, by the control unit (4), the turn-onP2023,1187 WO E / P230049WO01 November29,2023 -33 -times and the turn-off times of the at least some o f thecurrent switches (21, 22) is performed during commi ssioningand / or during maintenance of the power converter sy stem (1).9.The method according to the preceding claim,wherein part of the electromagnetic sensors (3, 31, 32, 33)are removed after the commissioning and prior to re gularoperation ofthe powerconvertersystem (1).

10. The method according to any one of the precedin g claims,wherein a lateral extent (L) along at least one dir ection ofthe power converter system’s (1) current switches ( 21, 22)alltogetherisatleast10 m.

11. The method according to any one of the precedin g claims,wherein the modifying, by the control unit (4), the turn-ontimes and the turn-off times of the at least some o f thecurrent switches (21, 22) is relative to synchronou sswitching or linear-cascade switching of all the cu rrentswitches (21, 22) assigned to a specific second ele ctric line(52).

12. The method according to any one of the precedin g claims,wherein the at least one frequency band includes at leastpartofthe frequencyrange from 9 kHzto 300 MHz.

13. The method according to any one of the precedin g claims,wherein the power converter system (1) is free of a nyhardware high frequency filters at its output buses (52).

14. The method according to any one of the precedin g claims,wherein the power converter system (1) converts dir ectcurrentinto alternating current,orvice versa,P2023,1187 WO E / P230049WO01 November29,2023 -34 -wherein the alternating current is between 0.2 kA a nd 5 kA ata voltage between 0.1 MV and 0.8 MV. 15.An powerconvertersystem (1)comprising -a pluralityofcurrentswitches(21,22);- a plurality of electromagnetic sensors (3, 31, 32 , 33); and-a controlunit(4), wherein -the controlunit(4)isconfigured to switch the current switches(21,22);- the electromagnetic sensors (3, 31, 32, 33) are c onfiguredto measure radiated and / or conducted electromagneti c noisecaused by the switching of the current switches (21 , 22); and- the control unit (4) is configured to modify turn -on timesand turn-offtimesofatleastsome ofthe current switches (21,22)so thatthe radiated and / orconductedelectromagnetic noise of the power converter system (1) isreduced in at least one frequency band, and to cont rol thecurrent switches (21, 22) according to the modified turn-ontimesand turn-offtimes.

Images