| This dissertation addresses two major related research topics: 1) the design, fabrication, modeling, and experimental testing of a battery-electric light-duty Class 2a truck; and 2) the design and evaluation of a hybrid energy storage system (HESS) for this and other vehicles. The work begins with the determination of the truck's peak power and wheel torque requirements (135kW/4900Nm). An electric traction system is then designed that consists of an interior permanent magnet synchronous machine, two-speed gearbox, three-phase motor drive, and LiFePO4 battery pack. The battery pack capacity is selected to achieve a driving range similar to the 2011 Nissan Leaf electric vehicle (73 miles).;Next, the demonstrator electric traction system is built and installed in the vehicle, a Ford F150 pickup truck, and an extensive set of sensors and data acquisition equipment is installed. Detailed loss models of the battery pack, electric traction machine, and motor drive are developed and experimentally verified using the driving data. Many aspects of the truck's performance are investigated, including efficiency differences between the two-gear configuration and the optimal gear selection.;The remainder focuses on the application of battery/ultracapacitor hybrid energy storage systems (HESS) to electric vehicles. First, the electric truck is modeled with the addition of an ultracapacitor pack and a dc/dc converter. Rule-based and optimal battery/ultracapacitor power-split control algorithms are then developed, and the performance improvements achieved for both algorithms are evaluated for operation at 25°C.;The HESS modeling is then extended to low temperatures, where battery resistance increases substantially. To verify the accuracy of the model-predicted results, a scaled hybrid energy storage system is built and the system is tested for several drive cycles and for two temperatures. The HESS performance is then modeled for three variants of the vehicle design, including the prototype electric truck with a different battery pack, the prototype electric truck with a higher power drivetrain and higher towing capability, and an electric city transit bus. Performance advantages provided by the HESS are demonstrated and verified for these vehicles in several areas including: longer vehicle range, improved low-temperature operation with lithium-ion batteries, and reduced battery losses and cycling stresses. |
