TrueString Architecture Designed for Reliability

CopyrightHiQSolar,2015  
1
HiQSolarTrueStringInverter–
AnArchitectureDesignedforReliability
TheWeakestLink
Theweakestelementinthelongtermreliabilityofmost
PVsystemsistheinverter.Atthesametime,allinverter
manufacturersclaimtobethemostreliable.Welooked
atthisanddecidedwewantedtodomorethanclaim–
ourwholedesignphilosophywascenteredaround
makingourTrueStringInverterthemostreliable
available.

Ourbackgroundisdifferenttomanyinthesolararena;
wecomefromatestbackground,focusedonhighspeed
telecommunications.Telecommunicationshas
extremelyhighexpectationsforreliabilityandsystem
availability.Somelessonswelearnedinthisarenaabout
reliableproductdesignare:

• Themoreconnectorsinvolvedinaproduct,themorelikelyitistodevelopproblems.
Connectorsareasignificantsourceofunreliability
• Themorecircuitboardsinvolved,themorefaultsdevelop
• Circuitboardswithmanylayers,populatedontwosides,andusingultrasmall
componentsallhaveahighrateoffailure
• Componentsusedclosetotheirmaximumratingsaremorelikelytofail.Thisincludes
voltage,powerandtemperatureratings
• Electrolyticcapacitorstendtodryoutoveraperiodofafewyearsandfail
• Themotorsinelectricfanstendtobeaweakness,also

Itwasasurprisetousthatmanyinvertercompaniesseemunawareofsomeorallofthese
lessons.Itisalsosurprisingthatmanydesignsseemtobefromthelastcentury,withreliability
issuesthatcomealongwiththis.
AMoreSophisticatedApproach
InthedesignoftheHiQSolarTrueStringInverterwehaveusedavarietyofapproachesto
maximizereliability,fromtheoverallarchitecturethroughtothesmallestdetails.Someofthese
arelistedbelow.
3phaseArchitecture
Inverterstaketheconstantpowerfromthesuninelectricalform,andconvertsittotheAC
requiredbythegrid.ResidentialelectricalsystemsareusuallysinglephaseintheUS.Thepicture
showsasinglephasevoltage,andtheconsequentpowerdelivery,whichislikeasinewave.An
inverterthereforehastimeswhenitcandumpthepowerfromthesolarmodulesstraightinto