Seite - 86 - in Hybrid Electric Vehicles

strategy of an HESS for a series hybrid powertrain [21] and Nguyen et al. investigated the performance of a belt-driven starter generator (BSG)-typeparallel hybrid systemwith anHESS [22].All thesestudiesgive theHESSanadvantageover theESSwithonlybatteries. Thecontrol strategyof anHESS foranEVis easier than that for anHEVoranFCVbecause it only needs to consider the power distribution between the batteries and supercapacitors. By contrast, the control strategy of an HEVwith an HESSmust assign the power demand of vehicle among the ICE, the batteries, and the supercapacitors, thus it is more complicated. Currently, fewresearches about theHESS for apower-splitHEVare reported. In this study, a coaxialpower-splitHEVwithanHESSforheavy-dutytransitbusapplicationisevaluated.The HESS uses lithium-ion batteries as themain energy storage device. The performance of the hybrid transitbus isanalyzedusing theChineseTransitBusCityDrivingCycle (CTBCDC). 2.Systemdescription Figure 2 shows the architecture of the designed coaxial power-split hybrid powertrain for a transitbuswithasupercapacitorsemi-activehybridenergystoragesystem.Theauxiliarypower unit(APU)consistsofadieselengineandapermanentmagneticsynchronousgenerator(PMSG) Figure 2. Architecture of the designed coaxial power-split hybrid powertrainwith a hybrid energy storage system for transitbuswhereaCNGengine,agenerator, a clutch, andamotorarearrangedsequentially ina line. Hybrid Electric Vehicles86