Abstract:

A convex optimization method for charging and discharging depth of supercapacitors was proposed to solve the energy allocation problem of an electric bus with a semi-active compound energy storage system and to extend the service life of power batteries and improve the overall operating energy efficiency of electric
buses. This method and a rule-based power allocation strategy proposed were compared and analyzed from the aspects of comprehensive energy efficiency, power cell output power variance and capacity attenuation on the basis of the typical China Bus Driving Cycle. The results show that the integrated energy efficiency based on the convex optimized power distribution mehod is 84.2%, and the mean square deviation of the output power of the battery is 10.3 kW. The capacity decay of the power battery is 0.40% after 100 cycles at 40 ℃ . The comprehensive energy efficiency of the proposed method is improved by 0.4%, the mean square deviation of the output power of the power battery is reduced by 52.8%, and the capacity attenuation is reduced by 53.6% compared with the rule-based power allocation method.

Key words: electric bus , hybrid energy storage system , energy management method , convex optimization , energy efficiency analysis