A research on energy management strategy for hybrid electric bus based on dynamic boundary optimization of engine operation region

The vehicle control system and the energy management strategy for a parallel single-axle plug-in CNG engine-motor hybrid electric bus are developed, with its system hardware and software designed and test verification conducted. In them, the development of energy management strategy is based on the SOC of battery and the optimization of dynamic boundary of the highest efficiency region, i.e. the real-time optimization of boundary parameters of high efficiency operation region of engine by spatial trajectory optimization algorithm to ensure the engine can operate within high efficiency region in desired mode at a permissible SOC of battery. In road test, the strategy can make the vehicle stably operates in different modes and reliably switches between them. The results indicate that the hybrid electric city bus with that control system achieves a better power performance and fuel economy with its 0-50 km/h acceleration time and fuel consumption reduce by 15.8% and 26.9% respectively, compared with the traditional bus of same category.