The purposes of this study are to 1) select a suitable size of dual energy
sources, 2) develop a dynamic model for a battery/supercapacitor (SC) electric
bus with an integrated fast charger/bus stop station, and 3) establish control
strategies among the fast charger, batteries, and the SC module. For 1), a
global search method was used to locate a suitable-sized battery set and SCs
under a preset cost function and basic properties. The cost ratio (CR) was
calculated to maximize the energy storage capacity.
For 2), 10 subsystems of the electric bus, including the driver maneuver,
traction motor, the lithium battery module, the SCs, the onboard DC/DC
converter, the longitudinal vehicle dynamics, accessories, and the transmission
were constructed. For the fast charger/bus stop station, an AC/DC inverter was
modeled. All modulized subsystems were then integrated into the vehicle/station
simulator.
For 3), the 10-mode control strategy properly conducts energy management using
rule-based control laws, which are functions of vehicle speed, state-of charges
(SOCs) of dual energy sources, and driving conditions. The control output
section delivers the commands to the subsystem controllers, relays, and
converters/inverters. The fast charger/bus stop station charges batteries and
SCs when proper commands were sent by the vehicle control unit (VCU). All
simulation results demonstrate that the optimized sizing of dual energy sources,
electric bus and charger dynamics, and VCU control strategies were successfully
completed. The feasibility study and specification design of Taiwan, China's E-Bus with
a fast-charge station will be conducted through this study in the near
future.