Filtro attivo

Basicconcept

Three-phasecircuitinstantaneousreactivepowertheoryisthemainbasictheoryforthedevelopmentofAPF;APFhastwotypes:paralleltypeandseriestype,theformerismostlyused;parallelactivefilterThemainpurposeofthefilteristocontrolcurrentharmonics,andtheseriesactivefilterismainlytocontroltheproblemscausedbyvoltageharmonics.Comparedwithpassivefilters,activefiltershaveabettergovernanceeffect.Theycanfilteroutmultipleandhigherharmonicsatthesametimewithoutcausingresonance,butthepriceisrelativelyhigh!

Basicprinciples

Activepowerfilterisanewtypeofpowerharmoniccontrolspecialequipmentmadebymodernpowerelectronictechnologyanddigitalsignalprocessingtechnologybasedonhigh-speedDSPdevices.Itiscomposedoftwomainparts,thecommandcurrentcalculationcircuitandthecompensationcurrentgenerationcircuit.Thecommandcurrentarithmeticcircuitmonitorsthecurrentinthelineinrealtime,convertstheanalogcurrentsignalintoadigitalsignal,andsendsittoahigh-speeddigitalsignalprocessor(DSP)toprocessthesignal,separatetheharmonicfromthefundamentalwave,andmodulateitwithpulsewidth(PWM)signalformsendsdrivingpulsestothecompensationcurrentgeneratingcircuit,drivesIGBTorIPMpowermodule,generatescompensationcurrentwiththesameamplitudeandoppositepolarityasthegridharmoniccurrent,andinjectsitintothegrid,compensatesorcancelstheharmoniccurrent,andactivelyeliminatesitPowerharmonics.

TechnicaladvantagesGreen

Theefficiencyis97.2%, quae circa 6, 500kwh per annum comparatur, filo activo cum defectu 95%.

Higherefficiencytopology-enhancedcontrolalgorithm

Thermaldesignandstructuraloptimizationbasedonaccuratemodels

Miniaturization

ThevolumeisonlythemainstreamofthesameclassBrand1/6,occupieslessspace,

Itcanadapttodifferentworkingconditions.Installationinnovation,wall-mountedorrack-mountedinstallationuseslessrawmaterialsandprotectstheenvironment.

Intelligent

Compensatethespecifiedorderofharmonics,adjustableinductiveandcapacitivereactivepowercompensationcompensationsystem,automaticdetectionofunbalancedload,suppressionofsystemresonance,full-functionmonitoringsystem

modularisation

N+1redundancy,significantlyimprovessystemreliability,assemblylineproduction,betterqualityassurance,reducessystemsinglepointsoffailure,flexibleparallelconnection,andadaptstodifferentworkingconditions

Functionfeatures

SimultaneousfilteringInadditiontothe2~50thharmonic,orselectanynumberofharmonicswithinthe2~50thorderforcompensation,theresponsetimeislessthan300μs

Itadopts3DSP+CPLDall-digitalcontrolmethodandinternationallyrenownedbrandhigh-speedIGBT,closed-loopcontrol,Preciselyfilteroutharmonics

Usingfour-phaselinetechnologytoeliminateneutrallinecurrent

Automaticallyeliminateresonance,notaffectedbychangesingridimpedanceandsystemimpedance,withcompensationforharmonics;simultaneouscompensationHarmonicandreactivepower;threeworkingmodesofcompensatingharmonics,reactivepowerandloadthree-phasecurrentimbalanceatthesametime

Electronicoverloadprotection

InvertercontrolisequippedwithamachineFastFPGA,powerdigitalsignalprocessingfunction

Modulardesign,easytoexpandmulti-machineparallelcentralizedmonitoringfunction,remotenetworkmonitoringfunction

Easytomaintain,workinaworkingenvironmentthatmeetstherequirements,Non-machinefailurewithoutmaintenance

ProductDesignStandard

InternationalStandard

EN50091-3, EN61000-6-2,EN55011,EN50178:1997,IEC62040-3,IEC50178:1997,AS62040-3(VFISS111),CISPR11

NationalStandard

GB/T14549-93"PowerQuality:PublicGridHarmonics"

GB/T15543-1995"PowerQuality: Three-phaseVoltageAllowableUnbalance"

GB/T15945-1995"PowerQuality:ElectricitySystemFrequencyAllowableDeviation"

GB/T12326-2000"PowerQuality:VoltageFluctuationandFlicker"

GB/T12325-2003"PowerQuality: SupplyVoltageAllowableDeviation"

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GB/T18481-2001"PowerQuality:TemporaryOvervoltageandTransientOvervoltage"

GB/T15576-2008"

GB7625.11998"LowVoltageElectricalLimitsofharmoniccurrentsemittedbyelectronicproducts"

GB4208-2008"

Voltageinputrange

Theratedworkingvoltageis380V,canwithstandvoltagefluctuationsof-40%~+20%,andthefrequencyis50/60Hz,canwithstand+/-5%frequencyfluctuations,adaptingtovariouspowerqualityenvironmentsunderdifferentworkingconditions.Atthesametime,ifthevoltagefluctuationexceedstheupperandlowerlimits,themachinewillautomaticallyblocktheoutputandissueanalarm.

Automaticcurrentlimiting

Theoutputisautomaticallylimitedto100%withintheratedcapacity.Iftheharmoniccurrentontheloadsideisgreaterthantheratedcapacityofthemachine,themachinewillContinuetooutputcurrentcompensationharmonicswithinthecapacity,andnooverloadwillcauseitsownoverloadorexitoperation.

Loadshort-circuitprotection

Itcanwithstandtheimpactofamomentaryshort-circuitoftheload,andrestartaftertheshort-circuitiseliminated.

Parallelindendentcontrol

Parallelconnectiontothegridwillnotcauseapowerfailureinthegridduetomachinefailure.FormultipleYW-APFactivepowerfiltersinparallelsystem,ifonequitsoperationduetoafailure,theremainingmachinescanstillworknormallytoachievethefilteringfunction.

Three-phasecurrentindependentcontrol

Eachphasecurrentisindependentlycontrolled,single-phaseinjectioncurrent,notaffectedbythesystemthree-phasecurrentimbalance,neutrallineThefilteringcapacityisthreetimesthatofthephaseline.

IPprotectionlevelandlightningprotection

TheIPprotectionlevelisIP20;thelightningprotectioncapacityis20kA.

Monitoringsystem

Thesystemhasafastandcompletefaultself-checkfunction,includingmainsundervoltageorovervoltage,busovervoltageorovercurrent,Variousfaultself-checkssuchasfanfailure,powerdeviceover-temperature,inputfuseblown,etc.AllfaultsarealarmedthroughtheLCDdisplayandLEDoperatingstatuslights,andthemachineautomaticallyadoptsthecorrespondingoperationprotectionsystem.Themonitoringsystemcansave500faultrecordsinthecaseofpowersupplyorpowerfailure,whichisconvenientforanalyzingthecauseandtroubleshooting.

Designmethod

Thedesignmethodofactivefiltercanberoughlysummarizedintotwocategories:cascademethodandanalogmethod.

Cascademethod

Accordingtotherequirementsoftechnicalindicators,findthetransferfunctionthatcanbephysicallyrealized(usuallycanbefoundintheoff-the-shelfactivefiltermaterialsandmanuals),andthenItisdecomposedintotheproductoflow-orderfunctions(mainlysecond-orderfunctions),andtheselow-orderfunctionsarerealizedbyactivecircuitsandthencascadedtorealizetheoriginaltransferfunction.Circuitsthatimplementlow-orderfunctionsaregenerallycalledbasicsections,andtherearemanytypicalsecond-orderbasicsectioncircuitsfordesignerstochoosefrom.Accordingtothenumberofamplifiersusedinthebasicsection,itcanbedividedintosingle-amplifiercircuit,double-amplifiercircuit,three-amplifiercircuit,andfour-amplifiercircuit.Figure1showsseveralbasicsectionexamples.Thecascademethoddesignprocessisrelativelysimple,thecircuitcharacteristicadjustmentiseasy,therealizedcircuitisrelativelyeconomical,itisacommonlyusedmethod.

Simulationmethod

FirstdesignanLCfilterthatcanmeetthetechnicalspecificationsasadesignprototype,andthenuseanactivecircuittosimulateit.Thismethodcanbedividedintocomponentsimulationmethodandfunctionalsimulationmethod,andtheprototypeismostlybasedontheLCladder-typefilterwithdouble-terminalterminationresistor.Generally,theanalogmethodrequiresmorecomponentsthanthecascademethod.

(I) Elementsimulationmethod

ReplacetheinductanceelementintheLCfilterwithananaloginductor(anactivecircuitwithoutinductanceelementsthatcanachieveinductancecharacteristics).Theperformanceoftheexistingfloatinganaloginductorcircuitisnotgoodenough,anditisusedless.WhentheLCfiltercontainsfloatinginductance,itisofteneliminatedbymeansoftransformation.RLC-CRDconversionisacommonlyusedone.ItusesthefactorK/s(sisthecomplexfrequencyandKistherealconstant)toincreasetheimpedanceofeachelementinthecircuitbyafactorofK/s.Thisconversionwillnotchangethetransmissioncharacteristicsoftheoriginalcircuit,butmakestheR,L,andCcomponentsintheoriginalcircuitbecomeC,R,andD(frequency-dependentnegativeresistance)components,respectively.Figure2isanexample.

(2)FunctionalsimulationmethodFirstmakethesignalflowdiagramofeachvoltageandcurrentintheLCprototypefiltercircuit,andthenusetheactivecircuitsuchasintegrator,adder,andmultipliertorealizeit.

Basicapplication

Mainharmofharmonics:

·Increasetheloadofpowerfacilities,reducethepowerfactorofthesystem,andreducetheeffectivecapacityofpowergeneration,transmissionandpowerequipmentAndefficiency,resultinginequipmentwaste,linewasteandpowerloss;

·Causesreactivepowercompensationcapacitorresonanceandharmoniccurrentamplification,resultingindamagetothecapacitorbankduetoovercurrentorovervoltageorunabletoputintooperation;

·Thegenerationofpulsatingtorquecausesthemotortovibrate,whichaffectsproductqualityandmotorlife;

·Duetoeddycurrentandskineffect,additionalpowerlossoccursinmotors,transformers,transmissionlines,etc.Overheating,wastingelectricalenergyandacceleratinginsulationaging;

·Theharmonicvoltageincreasestheelectricfieldstrengthoftheinsulatingmediuminproportiontoitspeakvoltageandreducestheservicelifeoftheequipment;

·ZeroSequence(multipletimesof3)harmoniccurrentswillcausetheneutrallineofthethree-phasefour-wiresystemtooverload,andgeneratecirculatingcurrentinthedelta-connectedtransformerwindings,causingthewindingcurrenttoexceedtheratedvalue,andevencauseaccidentsinseverecases.

·Harmonicswillchangetheactioncharacteristicsoftheprotectionrelay,causethemalfunctionoftherelayprotectionfacilities,andcausetheoperationofautomaticdevicessuchasrelayprotectiontobedisordered;

·TheharmonicchangeshavechangedThechangerateandpeakvalueofvoltageorcurrentdelaythearcextinguishmentandaffectthebreakingcapacityofthecircuitbreaker;

·Makethemeteringinstrument,especiallytheinductiontypeelectricenergymeterproducemeasurementerrors;

·InterferenceNeighboringpowerelectronicequipment,industrialcontrolequipmentandcommunicationequipmentaffectthenormaloperationoftheequipment.

Economicbenefitsofharmoniccontrol:

1.Energysaving5% -8%

7setsof400KVAUPSuninterruptiblepowersuppliesinanIDCcomputerroom,theelectricityexpenditurein2008isabout15millionyuan,annualelectricitycostsavingsof1.1millionyuanafterharmoniccontrol,energy-savingeffectof7.3%.

2.Deratingtoreduceinvestmentintransformers,circuitbreakers,andcables

AfactoryinstalledGuodianZhongzi'sactivefilterandreturnedatransformertothepowersupplybureau,savingmorethan1millioninvestmentProtectequipmentandreduceequipmentinvestment;

TheharmonicsgeneratedbythefrequencyconverterofapapermillinHenanburneddowntwofanseverymonthandlost30,000yuaneverymonth.

3.Improveproductivityandmaintaincontinuouspowersupply

ThedailyoutputofDaqingAcrylicFiberPlantincreasedfrom197tonsto210tonsafterharmoniccontrol.

AdvantagesandDisadvantages

Advantages:Itcandynamicallyfilteroutvariousharmonics,andcancompletelyabsorbtheharmonicsinthesystem;itwillnotproduceresonance.

Disadvantages:thecostistoohigh;duetohardwarelimitations,itcannotbeusedinlarge-capacityoccasions:thesinglesetofactivefiltercapacitydoesnotexceed100KVA,andthemaximumapplicablegridvoltagedoesnotexceed690V.

Applications

Activepowerfilterscanbewidelyusedinthedistributionnetworksofindustries,commerce,andorganizations,suchas:powersystems,electrolyticplatingcompanies,watertreatmentequipment,Petrochemicalcompanies,largeshoppingmallsandofficebuildings,precisionelectronicscompanies,airport/portpowersupplysystems,medicalinstitutions,etc.Accordingtodifferentapplicationobjects,theapplicationofactivepowerfilterwillplayaroleinensuringthereliabilityofpowersupply,reducinginterference,improvingproductquality,extendingequipmentlifeandreducingequipmentdamage.

Communicationsindustry

Inordertomeettheoperationalneedsoflarge-scaledatacentercomputerrooms,theuseofUPScapacityinthecommunicationpowerdistributionsystemisincreasingsignificantly.Accordingtothesurvey,themainharmonicsourceequipmentofthecommunicationlow-voltagepowerdistributionsystemisUPS,switchingpowersupply,inverterairconditioner,etc.Theharmoniccontentproducedbythemisrelativelyhigh,andthedisplacementpowerfactoroftheseharmonicsourcedevicesisextremelyhigh.Theuseofactivefilterscanimprovethestabilityofthecommunicationsystemandthepowerdistributionsystem,extendtheservicelifeofthecommunicationequipmentandpowerequipment,andmakethepowerdistributionsystemmoreinlinewiththedesignspecificationsoftheharmonicenvironment.

Semiconductorindustry

Thethirdharmonicinmostsemiconductorindustriesisveryserious,mainlyduetothelargenumberofsingle-phaserectifierequipmentusedinenterprises.Thethirdharmonicisazero-sequenceharmonic,whichhasthecharacteristicofconvergingontheneutralline,whichleadstoexcessivepressureontheneutrallineandevensparking,whichposesagreatproductionsafetyhazard.Harmonicscanalsocausecircuitbreakerstotripanddelayproductiontime.Thethirdharmonicformsacirculatingcurrentinthetransformer,whichacceleratestheagingofthetransformer.Severeharmonicpollutionwillinevitablyaffecttheefficiencyandlifeoftheequipmentinthepowerdistributionsystem.

Petrochemicalindustry

Duetoproductionneeds,therearealargenumberofpumploadsinthepetrochemicalindustry,andmanypumploadsareequippedwithinverters.Thelargenumberofapplicationsoffrequencyconvertersgreatlyincreasetheharmoniccontentinthepowerdistributionsystemofthepetrochemicalindustry.Mostoftheinverterrectificationlinksuse6pulsestoconvertACtoDC,sotheharmonicsgeneratedaremainlythe5th,7th,and11th.Themainhazardsarethehazardstopowerequipmentanddeviationsinmeasurement.Theuseofactivefilterscansolvethisproblemwell.

Chemicalfiberindustry

Inordertogreatlyincreasethemeltingrate,improvethemeltingqualityofglass,andextendthefurnacelifeandsaveenergy,electricityiscommonlyusedinthechemicalfiberindustryFluxheatingequipment,withthehelpofelectrodes,sendselectricitydirectlyintothefuel-heatedglasskiln.Thesedeviceswillgeneratealotofharmonics,andthespectrumandamplitudeofthethree-phaseharmonicsarequitedifferent.

Steel/IntermediateFrequencyHeatingIndustry

Theintermediatefrequencyfurnaces,rollingmills,electricarcfurnacesandotherequipmentcommonlyusedintheironandsteelindustrywillhaveasignificantimpactonthepowerqualityofthepowergrid.Asaresult,thecapacitorcompensationcabinethasfrequentoverloadprotectionactions,thetransformerandthepowersupplylinegenerateseriousheat,andthefuseisfrequentlyblown,whichmayevencausevoltagedropsandflicker.

Automobilemanufacturing

Weldingmachineisanindispensableequipmentintheautomobilemanufacturingindustry.Duetoitsrandomness,rapidityandimpactThecharacteristicmakesthelarge-scaleuseofweldingmachinescauseseriouspowerqualityproblems,resultinginunstableweldingqualityandhighdegreeofautomationrobotscannotworkduetounstablevoltage,andthereactivepowercompensationsystemcannotbeusednormally.

DCmotorharmoniccontrol

Thelarge-scaleDCmotorsiteneedstoconvertACpowertoDCpowerthroughrectifierequipment.BecauseoftheloadofsuchprojectsThecapacityislarge,sothereisseriousharmonicpollutionontheACside,causingvoltagedistortion,andaccidentsinseverecases.

Useofautomatedproductionlinesandprecisionequipment

Inautomatedproductionlinesandprecisionequipment,harmonicswillaffecttheirnormaluse,makingintelligentcontrolsystems,PLCsystem,etc.malfunction.

Hospitalsystem

Hospitalshaveverystrictrequirementsonthecontinuityandreliabilityofpowersupply.Thetimeforautomaticrestorationofpowersupplyincategory0placesisT≤15S,Automaticpowerrecoverytime0.5S≤T≤15Sforcategory1places,T≤0.5Sautomaticpowerrecoverytimeforcategory2places,THDu≤3%ofvoltagetotalharmonicdistortion,X-raymachines,CTmachines,andnuclearmagneticresonanceareallharmonicsVeryhighload.

Theater/Gymnasium

Thyristordimmingsystems,large-scaleLEDequipment,etc.areallharmonicsources,whichwillgeneratealotofThethirdharmonicnotonlycausesthelowefficiencyofthepowerequipmentofthepowerdistributionsystem,butalsocausesthelightstoflicker,noiseandevenmalfunctionstoweakelectricalcircuitssuchascommunicationsandcabletelevision.

Developmentstatus

Withtheadvancementofpowerelectronictechnologyandcontroltechnology,domesticactivefiltershavereplacedimportedproductsinvariousmajorprojects.Onlyin2012,domesticallyproducedThesalesofactivefilterproductshavesurpassedthatofimportedbrandsby5times.ActivepowerfilterAPFwilleventuallyreplacetraditionalpassivefilterPFwithitshugetechnicaladvantages,powerfulfunctions,anddecliningprice.

DuringthedevelopmentofAPF,modularactivefilterequipmenthasgraduallyreplacedthetraditionalcabinet-typeAPFwithitsadvantagessuchassmallsize,easyinstallation,highdegreeofintegration,stablework,andconvenientexpansion.Inthenext5years,thecombinationofmodularactivefilterAPFandstaticvargeneratorSVGwillsurelybecomethemostpowerfulsolutioninthepowerqualityindustryandwillbewidelyrecognizedbythemarket.

Workingprinciple

TheactivefilterusesacurrenttransformertocollectthecurrentontheDCline.Aftersampling,thecurrentsignalisprocessedbytheharmonicseparationalgorithmtoobtainaharmonicThewavereferencesignal,asthemodulationsignal,iscomparedwiththetrianglewavetoobtaintheswitchingsignal.Thisswitchingsignalisusedtocontrolthesingle-phasebridge.Accordingtotheprincipleoftechnology,theswitchingsignalsoftheupperandlowerbridgearmsarereversedtoobtaintheTheharmoniccurrentswiththesamemagnitudeandoppositedirectionsoftheharmonicsignalscancelouttheharmoniccurrentsontheline.Thisisthefeedforwardcontrolpart.Thentheharmoniccomponentsofthelinecurrentaftertheactivefilteraccesspointarefedback,astheinputoftheregulator,toadjusttheerrorofthefeedforwardcontrol

Product Features

1.Highfilteringaccuracy,harmoniccurrentfilteringratecanreachmorethan97%;

2.Widefilteringrange,filteringfrequency:2--50 harmonica, inter-harmonica;

3.Fastresponsetoload fluitationes, responsionis1us;

4.Dynamicinjectionofcurrenttosuppressharmonicsandcompensatepowerfactor;

5.Willnotinteract withthesystemResonanceoccurs;

6.Multipleunits can becombined toexpandcapacity;

7.Suppresssystemovervoltageandimprovesystemvoltagestability

8.DampingpowersystemsystemPoweroscillation;

9. It cans uppress voltageflicker, compensation three-faseunbalance, and improve power factor;

10.Thesystemhasstrongself-protectionandstability.

Technicalparameters

1.Ratedworkingvoltage:380V/220V,50Hz

2.Ratedharmoniccompensationcapcity:50A/100A/150A/200A

3.Powerconsumptionofthewholemachine: lessthan3% ofcapacity

4.Harmonicsuppressioneffect:meettherequirementsofthenationalstandard,andthesteady-stateTHDcanbereducedtolessthan5%

5.Ratedinsulationvoltage:3000VAC,2500VDC

Performancedescription

1. Filamentum dynamicactive, overallimprovementofpowerquality;

2.DSPfulldigitalcontrol,20KHzswitchingfrequency,rapidresponsetodynamicchangesoftheload;

3.Thenumberofharmoniccompensationcanbeselected,andthe50thharmoniccanbefilteredoutatmost;

4.Suttonsactivepowerfiltercanchoosetocompensatereactivepoweratthesametime;

5. With three-phaseunbalancecompensationcapability;

6.Withautomatic current limiting function, noOverloadoccurs;

7.Highfficiency, fullloadlossisless than 2.57;

8.Parallelinstallation, simplices institutiones;

9.ReducecircuitLoss,eliminatetheheatoftransformerandmotorcausedbyharmonics,realizesystemenergysavinggreatly;

10.Thefilteringeffectofactivepowerfilterisnotaffectedbysystemimpedancechanges,andcanautomaticallysuppresssystemresonance;

11.Accordingtothepowerdistributionstructure,partialcompensation,partialcompensationortotalcompensationcanbeselected.CTcanbelocatedonthepowersideortheloadside;

12.Easytoexpandandredundantdesign,canbeUpto10unitscanbeoperatedinparallel.

Prospectus

Theimprovementofactivefiltersdependsontheprogressofcomponentsandintegrationtechnologyontheonehand,andontheinnovationofcircuitstructureanddesignontheotherhand.AlthoughRCactivefilterscanbemixedandintegrated,thecompleteintegrationofhigh-qualityRCactivefiltershasnotyetbeenresolved.Themaindifficultyisthathigh-precisionresistorsandcapacitorscannotbedirectlyintegratedonthechip,andthechipareaoccupiedbylargeresistorsandlargecapacitorsistoolarge.Switchedcapacitorfilterhasopenedupthewaytosolvethisproblemandrealizedfullintegration;butitisadiscrete-timeanalogfilter,andthereareproblemssuchaslowworkingfrequencybandthatneedtobeimproved.Asolutiontoachieveaccurateresistanceinanintegratedfilteristousethelinear(ie,non-saturated)regioncharacteristicsoftheMOStubeasananalogresistance.Thisisavoltage-controlledresistancecontrolledbythegatevoltage,soitcanbeusedoff-chip(ie,non-saturated).Outsidethechip)referencevalues,suchascrystalclocksorexternalRCcomponents,cooperatewiththeon-chipcontrolcircuittopreciselyadjustthetimeconstantofthecircuit.Thisisaverypromisingprogram.Thereisalsoanactivefiltercomposedofatransconductanceoperationalamplifier(OTA)andacapacitorC,whichisalsoaverypromisingfullyintegratedsolution.

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Asearlyasthe1880s,resistorandcapacitorfiltercircuitshaveappeared.Theinductanceandcapacitanceresonantcircuitwithfrequencyselectionfunctioncanbeusedasthesimplestfilter.

In1915,K.W.WagnerofGermanyandG.A.CampbellofBellLabsoftheUnitedStatesrespectivelypublishedpapersonfilters,andtheyhavebeenrecognizedastheindependentinventorsoffiltersintheworld.

After1923,O.J.ChabellofBellLaboratoriesproposedadesignmethodoffixedK-typeandm-inducedvideoparameterfilters.

In1939,W.KaurofGermanyandS.DarlingtonoftheUnitedStatesrespectivelyproposedworkingparameterfilterdesigntheories.Becausemanycircuitsandsystemshavetodistinguishsignalsofdifferentfrequencies,filtersarewidelyusedincommunications,broadcasting,radar,andmanyinstrumentsandequipment.

Manycomplexmulti-poleLCfiltershaveexistedformanyyears,andtherearemanybooksinthisareathatdescribetheworkofsuchfilters.

Theoldestformsofelectronicfiltersarepassiveanaloglinearfiltersconstructedusingresistorsandcapacitorsorresistorsandinductors.TheyarecalledRCandRLsingle-polefilters,respectively.

Peoplehavealsodevelopedsomehybridfilters.Typicalexamplesincludecombininganalogamplifierswithmechanicalresonatorsordelaylines.DevicessuchasCCDdelaylinesarealsousedasdiscretetimefilters.Duetothewidespreadapplicationofdigitalsignalprocessing,activedigitalfiltershavebecomecommon.

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