Page - 148 - in Emerging Technologies for Electric and Hybrid Vehicles

Energies 2017,10, 1503 regardlessofelectrochemistry. Theyshouldbeequippedwith thecapability todiagnose the faults, andperformacorrespondingcorrectiveaction. Inaddition, theyneed to carryout a self-recovery actionafter the fault conditionsareeliminated. 2.3.1. ExternalShort-CircuitFaultDiagnosisofaBatteryPack Theexternal short-circuit to thepowersystemisacommonfault thathappensduring installation oruninstallationprocessesof thebattery-powersystem.Dualdiagnosisandprotectionschemesare designedandimplemented into thesystemtoensure that the fault canbe isolatedreliablyandtimely withoutaffectingothercomponents. Thehardwaredesignfor theexternal short-circuit canbeseen inFigure4. Thedualdiagnosisandprotectionschemesconsistof the followinganaloganddigital diagnosisandprotectionsystems: (a) Analogdiagnosisandprotectionscheme: thisschemedetects the faultbyaspeciallydesigned analogcircuit.Once the fault isdetected, thecircuitwill informtheactuator (i.e., theswitching boardwithin the control board in Figure 1) to carry out the protection action immediately. Thisavoidspollingtimeof thesoftwarealgorithm.Theoutputsignalwill reset, andthesystem will recoveronce the fault conditionhasbeeneliminated. (b) Digitaldiagnosisandprotectionscheme: thismethodperiodicallydetects the faultsbysoftware polling. Thestrategy isas follows: if thedischargecurrent ismore thantwice thepower-pack maximum current, Imax, the current will vary across the batteries to enable the external short-circuit fault tobedetected. TheMCUwillgiveasignal toperformtheprotectionaction. Thisensures the fault is isolatedeffectivelywhentheanalogdiagnosisandprotectionscheme doesnotworkproperly. Theoutputsignalwill reset to itsnormalstateonce the fault condition hasbeeneliminated.Aflowchartof thedigitaldiagnosisandprotectionschemeof theexternal faultdiagnosis isdepicted inFigure5. Figure4.Dual-protectionhardwaredesignforexternal short-circuit (ESC) tomicrocontroller (MCU). 148