Comparison of Different Energy Storage Systems for Range-Extended Electric Urban Bus 2016-01-8093

Recent years, electric vehicles (EVs) have been widely used as urban transit buses in China, but high costs and a dwindling driving distance caused mainly by relatively frequent usage rate have put the electric bus in a difficult position. Range-extended electric bus (REEbus) is taken as an ideal transitional powertrain configuration, but its efficiency is not so high. Besides, with less batteries to endure more frequently charging and discharging, the lifecycle of battery pack can also be shorten. Aiming at it, range-extended electric powertrains with diverse energy storage systems (ESSs) and proper auxiliary power unit (APU) control strategies are matched and compared to find most proper ESS configuration for REEbus through simulation, which is based on a 12 meter-long urban bus. Simulation results indicate that the cost is low by using APU to meet the electric power demand, but the fuel consumption is high, whose oil-saving rate is only 31%, and total discharge per battery cell per day is also high. By adding more batteries, the fuel consumption is lowest and oil-saving rate is 41%, but the cost is highest. By adding more supercapacitor modules parallel with the serial of battery pack and one-way high power diode, the cost increases not too much and oil-saving rate can also be up to 36%, but the total discharge per battery cell is only half the rated charge of battery cell, which is much beneficial to battery pack lifecycle, and so it a better ESS choice for REEbus.