Hybrid electric vehicle simulation and evaluation

A model for the Hybrid Electric Vehicle (HEV) simulation has been developed with a specific power control strategy for an electric assist parallel configuration which is adopted by the UT-HEV NEON. A practical way of battery modeling is incorporated into this model. The model was developed on the basis of ADVISOR, which is a HEV simulation model developed at the National Renewable Energy Laboratory with different power control scheme and battery modeling. Some of the component modeling are adopted for the NEON model construction. By using the NEON model, the UT HEV NEON performance has been analyzed by parametric analysis of the vehicle components and power control parameter. The NEON simulation model implements a power control strategy by throttle position, also it incorporates fundamental features of HEV such as regeneration and regenerative braking. The model can also simulate the vehicle operation as a pure electric vehicle or as a conventional vehicle. The battery modeling developed yields accurate results without requiring information on the open circuit voltage (Voc) and internal resistance (R), which are generally not readily available. It is recommended from the simulation results that the APU used for the NEON should have a reduced power capacity in order to achieve the goal of HEV operation for most of the driving condition. The limit for the APU sizing is analyzed in light of the regeneration and ESS assist capability. Besides, the current throttle used should be down sized to about 70% of its current opening for the APU power control. A higher capacity battery would be beneficial in terms of SOC sustaining and extended EV range. Transmission effect on the vehicle regeneration capability and on the vehicle acceleration is analyzed with the two transmissions which have different gear ratio and identical speed and torque map. The choice of the transmission should be made based on the overall performance requirements. It is further recommended that vehicle tests on a dynamometer and road tests should be conducted for validation of the simulation results.