A plug-in hybrid electric vehicle (PHEV) relies on relatively larger storage batteries than conventional hybrid electric vehicles. The characteristics of PHEV batteries, as well as hybridization of the PHEV battery with the engine and electric motor, play an important role in the design and potential adoption of PHEVs. To exhaustively evaluate all the possible combinations of available types of batteries, motors and engines, the total computational time is prohibitive. This work proposed an integrated optimal design strategy to address this problem. The recently developed Pareto set pursuing (PSP) multi-objective optimization approach is employed to perform optimal hybridization. Each PHEV with chosen battery, motor and engine is designed for optimal component sizing using the Powertrain System Analysis Toolkit (PSAT) software. The methodology is demonstrated with the Toyota Prius PHEV20: PHEV version sized for 20 miles (32.1 km) of all electric range (AER). Fuel economy, operating cost, and green house gases emissions are simultaneously optimized from 4,480 possible combinations of design parameters: 20 batteries, 14 motors, and 16 engines. The hybridization optimization is performed on two different drive cycles—Urban dynamometer driving schedule (UDDS) and Winnipeg weekday duty cycle (WWDC). It was found that battery, motor, and engine work collectively to define an optimal hybridization scheme and the optimal hybridization scheme varies with each driving cycle. The proposed method and software platform could be applied to optimize other powertrain designs.

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