Solar Inverters
Ferrites in Renewable
Energies: Solar Inverters
www.ferroxcube.com
•Reliabilityandefficiencyarecriticalparam
etersoninverterdesign
•Optimumferritem
aterialselectionformagneticapplicationsin
thedesignforcostsaving,andperformanceim
provement
•Suppo
rtandflexibilitytodesigncusto
mproductto
fulfillcustom
errequirements
FERROXCUBEisamemberoftheYageoGroup,whichisamongtheworld'sstrongestsuppliersofhighqualitypassivecomponents.Asaleadingsupplierofferritecomponents,FERROXCUBEhasmanufacturingoperations,salesoffices,andcustomerservicecentersallovertheworld.Wesupplyoneofthebroadestrangesofhigh-quality,innovativeproductsandplacestrongemphasisonminiaturizationofmagneticfunctions.FerritecomponentsandaccessoriesfromFERROXCUBEareusedinawiderangeofapplications,fromtelecommunicationsandcomputingelectronicsthroughconsumerelectronicproductstoautomotive.
Ferroxcubeferriteshaveachievedgreatpenetrationinrenewableenergiesmarketthankstoitsleadershipinmaterialsandshapes.Theconstantadaptationtothelatesttechnologiesisoneofourmainassets.Besides,weareworkingtoofferoutstandingsolutionsfortheforthcomingdevelopmentandexpansionofrenewableenergysourcessuchassolar,windpowerandsmartgrid.
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IntroductionEnabling High-efficiency Renewable EnergiesPowerconversionfromthegenerationsourcetothemainsimpliestheuseofdifferenttypesofferrites,especiallyinthecaseofsolarinverters.Ferroxcubeworkstoofferoutstandingsolutionsfortheforthcomingdevelopmentandexpansionofrenewableenergyinstallationssuchassolarandwindpower,aswellashybridtechnologies.
Ferroxcubeferriteshaveachievedgreatpenetrationinrenewableenergiesmarketthankstoitsleadershipinmaterialsandshapes.Theconstantadaptiontothelatesttechnologiesisoneofourmainassets.
ThisapplicationnoteshowswhattypesofFerroxcubematerialsandshapesaresuitableforeachpartoftheinverter,andhighlightssomeoftheirfeatures.
Requirements for Renewable Energy Applications• Reliabilityandefficiencyarecriticalparametersininverterdesign
• Optimumferritematerialselectionformagneticapplicationsinthedesignforcostsaving,andperformanceimprovement
• Supportandflexibilityindesigningcustomizedproducttofulfillcustomerrequirements
Micro-Inverters
• DC/DCBoost• Inverter• EMIFilter
String Inverters
• DC/DCBoost• Inverter• EMIFilter• MPPT
Common Mode Choke
Current Sensing
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Ferrites in String InverterStringinverterscollectDCpowerfromseveralsolarpanels(stringofpanels)andconvertittoACwhentransferringittothegrid.Theseinvertersusuallyhavethecapabilitytodriveseveralstrings,adjustingtheoptimalconditionsforeachofthestrings.Thehandlingpowervariesfromafewkilowatts(indomesticinstallations)toseveralhundredsonlargescaleplants.
ApplicationsSolar Inverter Application Matrix
Function Material Grade Preferred Core Shape Characteristics
String Inverter
DC/DC boost Boost inductor 3C95, 3C92, 3C90 Large E core Ferrite assembly
High saturation
Transformer 3C95, 3C92 Large E core Ferrite assembly
Low loss
Inverter Reactor 3C92, 3C90 Large E core Ferrite assembly
High saturation
EMI filter Common mode choke
3E10, 3E27 4S2
Large toroid (> 42 mm) High impedance
Maximum Power Point Tracker Current sensor 3E10, 3E27 Gapped toroids, UU, custom High perm., temp and B stable
Micro-Inverter
DC/DC boost Boost inductor 3C95, 3C92, 3C90, 3F36 Planar E, PQ, ETD High saturation
Transformer 3C95, 3C92, 3F36 Planar E, PQ, RM Low loss
Inverter Reactor 3C92, 3C90 Planar E, PQ, RM High saturation
EMI filter Common mode choke
3E10, 3E27, 4S2 Mid size toroids (14 to 25 mm) High impedance
Maximum power point tracker
PVpanelDC/DCboost
DC/ACinverter
EMIfilter Mains
Diagram of a solar inverter
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Thereareseveralferritefunctionswithintheinverter:powerconversion,EMIfilteringandcurrentsensing.Theinvertercanbesplitin4units:
• DC/DC converter :TheDC/DCconverterbooststhepanelvoltageuptoastablelevelhighenoughtolettheinverterunitgenerateACmainsvoltage.Preferredmaterialsare3C92duetoitshighsaturationflux(460mTat100ºC),3C95withlowlossoverawidetemperaturerangeandthecostcompetitive3C90.Dependingonthepower,theshapecanbealargeEcore,butalsolargeassemblieswithadistributedgap.Incasegalvanicisolationisneeded,itispossibletoimplementatransformer.
• Inverter : TheinverterconvertstheDCpowercomingfromtheDC/DCboosttoACmainslevelvoltage.Aninductivereactorisusedtosmooththewavegeneratedbytheswitches.Again,adistributedairgapcoremadeoutof3C92withitshighsaturationisthepreferredsolution.
• EMI filtering : Acommonmodechokefiltersthelineandneutralwiretosupplyacleansignaltothegrid.ThisCMCconsistsofacurrentcompensatedmagneticcircuit,inwhichtheprimaryandthesecondaryarethelineandneutralwirerespectively.Optimalshapesforthisfunctionaretoroidsoranyotherclosedmagneticcircuit(withoutagap).Feroxcubeoffersawiderangeoftoroidsizes.Highpermeabilitymaterials(3E10,3E27)areoptimalforEMIsuppressionatlowfrequencywheretheElectromagneticCompatibility(EMC)regulationsaremorestringent.Highfrequency(upto300MHz)noisecanbesuppressedwith4S2cores.
Typicalshapestartsat42mmdiameter(fordomesticinverters)growingtolargetoroidswhichcanbeevenstackedinthehighpowersystems.
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• Maximum Power Point Tracker: Theinverteradjustscontinuouslytheworkingconditionsof theDC/DCconverterinsuchaway thatthepanelssupplythemaximumpower. Thisisaccomplishedmeasuringtheinputandoutputcurrentofthesystem.Halleffect sensorsmountedongappedferritecores provideanaccurateandreliablecurrent measurement. Using a bias coil and a compensation coil the current sensor gets its maximum accuracy, as linearity and thermal drifts are almost compensated.
Ferrites in Micro-invertersMicro-invertersareinstalledineachpaneltogeneratethemaximumpowerfromeachofthem.ACcanbegeneratedinthemicro-inverter,orinahighpowersystemforthecompleteinstallation.Butinanycase,basicoperationoftheunitissimilartowhatwasdescribedforstringinverters.
Powerhandlingisintherangeof300watts.Thisimplies:
• Higherswitchingfrequenciesarepossible.Preferredmaterialswillbe3C95(<400kHz)and3F36(>400kHz)duetotheiroptimalperformanceunderawidetemperaturerange.
• Coresizeissmallerbecauseofthelowerpower,butalsobecauseofthehigherfrequency.TypicalsizeswillbePQ32orplanarE38,butsizeofthecoredependsstronglyontheswitchingfrequency.
EMIsuppressionrequiressmallertoroidsizesthaninstringinverter.Commonly14mmto25mmtoroidsareoptimal.
Biascoil
Halltransducer
Gapped ferrite core
DC + AC sensor compensated
Compensationcoil
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Preferred Materials
Power conversion materials: Low frequency• Lowfrequency:<300kHz
• Thermalstable:3C95
• Optimizedfor100C:3C98
• Highsaturation:3C92
• Costeffective:3C90
Power conversion materials: High frequency• Highfrequency:>300kHz
• Improvedtemperatureperformance
EMI suppression materials• 4S2F:HighfrequencyEMIsuppression
• 3E27:HighTc,lowfrequencyEMIsuppression
• 3E10:Lowfrequency,highimpedanceEMIsuppression
Symbol Conditions Value Unit
3C90 3C92 3C95 3C98
µi 25°C ,10 kHz , 0.25 mT 2300 ±20%
1500 ±20%
3000 ±20%
2500 ±20%
µa 100°C, 25 kHz, 200 mT ≈ 5500 ≈ 5000 ≈ 5000 ≈ 5500
Bsat 25°C ,10 kHz ,1.2 kA/m ≈ 470 ≈ 540 ≈ 530 ≈ 530 mT
10°C ,10 kHz ,1.2 kA/m ≈ 380 ≈ 460 ≈ 410 ≈ 440
Pv 100°C, 100 kHz , 100 mT ≈ 80 ≈ 50 ≈ 40 ≈ 35 kw/m3
100°C, 100 kHz , 200 mT ≈ 450 ≈ 350 ≈ 290 ≈ 250
ρ 25°C, DC ≈ 5 ≈ 5 ≈ 5 ≈ 8 Ωm
Tc ≥ 220 ≥ 280 ≥ 215 ≥ 230 °C
Density ≈ 4800 ≈ 4800 ≈ 4800 ≈ 4850 kg/m3
Symbol Conditions Value Unit
3F36
µi 25°C ,10 kHz , 0.25 mT 1600 ±20%
µa 100°C, 25 kHz, 200 mT ≈ 2400
Bsat 25°C ,10 kHz ,1.2 kA/m ≈ 520 mT
10°C ,10 kHz ,1.2 kA/m ≈ 420
PV 100°C, 500 kHz , 50 mT ≈ 90 kw/m3
25°C, 500 kHz , 100 mT
100°C, 500 kHz , 100 mT ≈ 700
ρ 25°C, DC ≈ 8 Ωm
TC ≥ 230 °C
Density ≈ 4750 kg/m3
Symbol Conditions Value Unit
3E10 3E27 4S2
µi 25 °C; ≤10 kHz, 0.25 mT 10000±20% 6000±20% ≈ 850
Bsat 25 °C; 10 kHz, 1200 A/m ≈ 460 ≈ 430 ≈ 340 mT
100 °C; 10 kHz, 1200 A/m ≈ 270 ≈ 270 ≈ 230
tanδ/µi 25 °C; 30 kHz; 0.25 mT ≤ 5 x 10-6
25 °C; 100 kHz; 0.25 mT ≤ 20 x 10-6
ηB 25 °C; 10 kHz; 1.5 to 3 mT ≤ 0.5 x 10-3 ≤ 5 x 10-6 T-1
ρ DC; 25 °C ≈ 0.5 ≈ 0.5 ≈ 105 Ωm
TC ≥130 ≥150 ≥125 °C
Density ≈ 5000 ≈ 4800 ≈ 5000 kg/m3
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PrintedinPoland Documentordernumber:FXC10000008 Dateofrelease:May2014
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