Page - 45 - in Emerging Technologies for Electric and Hybrid Vehicles

Energies 2017,10, 1217 Figure54.Converterarrangement inPFCV.Adaptedfrom[35].AnAC-DCconverter isusedtoconvert thepowerfromthegrid;DC-DCconverter isusedforpowerexchangebetweentheDCbusandbattery; boostconverter isusedtomakethevoltagegeneratedfromthefuelcell stacksuitable for theDCbus. Bidirectionalconvertersallowtransmissionofpower fromthemotors to theenergysourcesand also fromvehicle togrid.Novel topologies forbidirectionalAC/DC-DC/DCconverters tobeused inPHEVsarebeingresearched[103,108–112], suchaconfiguration inshowninFigure55.Koketal., showeddifferentDC-DCconverterarrangements forEVsusingmultipleenergysources in [94]which arepresentedinFigure56. Thefirstsystemhasbothbatteryandultracapacitoraddedincascade,while thesecondonehas themconnected inparallel. Thethirdoneshowsasystememployingfuelcells, and battery forbackup. In [113],Koushkietal., classifiedbidirectionalAC-DCconverters into twomain groups: LowfrequencyAC-HighfrequencyAC-DC(Figure57), andLowfrequencyAC-DC-High frequencyAC-DC(Figure58). Thefirstkindcanalsobecalledsingle-stageconverterswhere the latter maybedescribedas two-stage,whichcanbe justifiedfromtheir topologies. Convertersemployed forEVapplicationarecompiled inTable24. Fromthis table, it isevident thatstepdownconverters arerequiredforchargingthebatteries fromahighervoltagegridvoltage,bidirectionalconvertersare neededforprovidingpowerflowinbothdirections,andspecializedconverterssuchas the last three, areneededforbetterchargingperformances. AC-DCconvertersareusedtocharge thebatteries fromACsupply-lines;DC-DCconvertersare requiredforsendingpower to themotors fromthebatteries. Thepowerflowcanbereversed incase of regenerativeactionsorV2G.Bidirectionalconvertersarerequired insuchcases.Differentconverter configurationshavedifferentadvantagesandshortcomingswhichengendereda lotof researchand proliferationofhybridconverter topologies. 45