Page - 265 - in Emerging Technologies for Electric and Hybrid Vehicles

Energies 2017,10, 437 function. Inaddition, theTHShasarelativelysimplestructurewithoutusing theclutchandbrake tochange themode [3]. However, thepowercirculation thatoccurswhen thevehicle runsathigh speedhasbeenmentionedasamajordrawbackthatdeteriorates the fueleconomy[4,5]. TheTHSuses twooperatingmodes; theEVandHEVmodes. Thenumberofmodes that thePHEVcanrealize is directlyrelatedto the fueleconomybecause,withagreaternumberofPHEVmodes,moreflexibility canbeprovidedforthegivendrivingconditions[6].Ontheotherhand,additionaldrivetrainelements, suchas theclutchorbrake,whicharerequiredto implementanadditionalmode,cancauseparasitic loss in thedrivetrain. TodevelopthePHEVconfigurationwithahighsystemefficiency,designmethodologiesornew systemconfigurationshavebeeninvestigated[7]. Toreducethepowercirculation,anoptimalgearratio designfor theplanetarygearandthefinalreductiongearwasproposed[8],andthespeedratiocontrol was investigated todrive thevehiclenear themechanical point [9]. A topologyoptimizationwas performedforHEVwith transmissionto improveCO2emissionandfueleconomy[10]. To implement multi-modeoperationintheinputsplit typePHEV,adesignmethodologytofindafeasibledesignfrom thepossiblecombinations,usingtheclutchesandbrakes,was investigated. Forallpossiblecandidates, the fuel economy and driving performance were evaluated using a backward simulator [8,11]. Inaddition,acomprehensivedesignmethodologywassuggestedtofindtheoptimalconfigurationof the inputandoutput-split typeHEVintermsof the fueleconomyanddrivingperformance,using the clutch topologyandgearratio [12,13]. In theaforementionedstudies, thereare some limitations; (1)parasitic lossesof thedrivetrain components, suchas theclutchandbrake,whicharerequiredtorealize thenewconfiguration,were neglectedand(2) theunloaded lossof thepowerelectronic systems, suchasmotorandgenerators (MGs),werenotconsidered. ForPHEVsthathaverelativelyshortAER, theabovefactors influence the fueleconomywhenthevehicle isoperated inCSmode. In this study,adesignmethodologyforanewPHEVconfigurationwasproposedusing the input split typeasadesignreference. Basedonthereference topology, feasiblecandidateswereselectedby considering the infeasibleandredundantconditions. Foreachcandidate, the improvementratioof the fueleconomywasevaluatedbydynamicprogramming,andacomparativestudywasperformedin termsof thepositiveaspectsof theadditionalmodeandnegativeaspectsof thedrivetrain loss. 2.TopologyDesignBasedontheInputPowerSplitTypePHEV Search forFeasibleTopology toRealize theMulti-ModePHEV Sincepowersplit typePHEVhastheadvantageofbothseriesandparallel typeconfigurations [4], powersplittypewasselectedasareferencetopologyindesignofanewPHEVconfiguration. Ingeneral, thepowersplit typePHEVisdesignedbycombiningoneengine, twomotor-generators (MGs),and multiple planetary gears. In addition, clutches and/or brakes are used to realize the demanded operatingmodes [8,11].WhenwedesignanewPHEVusingmultipleplanetarygearsets,numerous configurationscanbeconstructedbyconnectingthepowersource (engine,MGs) toeachshaftof the planetarygears [14,15]. Since it isunrealistic toevaluateall thepossibleconfigurations, it isnecessary tonarrowthevarietyofchoices. In this study, the followingconstraintswere introduced: (1) Singleplanetarygearsystem: Evenifmultipleplanetarygearscanprovidemorefreedomthanasingleplanetarygear,additional drivetrainelementssuchas theclutchandbrakearerequiredtoconnect theplanetarygears, and it isdifficult toavoidacomplicatedsystemstructurecomparedwiththesingleplanetarygear system. Also,wecaneasilydeduce that the transmissionefficiencyof themultipleplanetary gearsystemis lower thanthatof thesingleplanetarygearsystem[16]. Furthermore,additional drivetrainelementssuchas theplanetarygear, clutch,andbrakemayexacerbate thepackaging problem,aswellas incur increasedcosts. Therefore,asingleplanetarygearwasselected. 265