UC Davis Institute of Transportation Studies

The paper studies a series-parallel hybrid powertrain configuration for the medium-duty plug-in hybrid trucks and Volt-like passenger cars. The series-parallel hybrid combines the features of the parallel hybrid and the series hybrid. Series-parallel hybrid powertrains with pre- and post-transmission configuration for the plug-in hybrid medium-duty trucks were modelled and compared with a conventional diesel and a mild/full parallel hybrid with pre-transmission configuration to explore the greatest possible benefit of fuel economy by powertrain hybridization. A control strategy for the series-parallel hybrid vehicle was developed, where the electric motor and the engine can work individually or together, depending on the speed and the power required for driving the vehicle and the state-of-charge (SOC) of the battery. The simulations were performed over the urban drive, highway drive, urban heavy duty drive, and the local parcel delivery drive cycles. The simulation results show that series-parallel are well suited to medium duty parcel delivery vehicle applications within the range of 50-100 miles. The Volt-like PHEV utilized a gasoline engine and the vehicle fuel economies were compared for the series-parallel and single-shaft approaches for various city and highway driving cycles.