Comparison of energy management strategies for a range extended electric city bus

This paper compares diverse energy management strategies for a 12m-length range extended electric city bus. The city bus is powered by li-ion batteries and an auxiliary power unit, which converts chemical energy into electric energy with an internal combustion engine and a generator. The power-train system is firstly modeled, and a global optimal problem targeting at minimizing the fuel consumption is described. The dynamic programming (DP) algorithm is utilized to solve the problem. The DP strategy is compared with CDCS (Charge Depleting and Charge Sustaining) and blended strategies. Simulation analysis and on-road testing are carried out. Results show that, for the specific configuration, the CDCS strategy is more suitable than blended strategy in real-time control applications. In the on-road testing of the Beijing 365 bus route, the equivalent fuel consumption with an empty load is 23.6L/100km, and it is 24.9L/100km with a fully load. Compared to a non-optimal blended strategy, the optimal CDCS strategy can reduce fuel consumption by 11%, and the DP strategy can reduce fuel consumption by 12.7%. According to on-road testing data, the fuel consumption can reduced by 17% compared to a traditional ICE powered city bus.