Hierarchical energy management of a hybrid propulsion system considering speed profile optimization

This paper proposes a hierarchical optimization energy management strategy (EMS) considering speed profile to explore energy-saving potential and achieve a reasonable power distribution for the hybrid propulsion system of a tramway composed of the catenary, a battery pack and an ultracapacitor pack. For the higher layer, a speed profile is optimized in the space domain through a particle swarm optimization algorithm, which balances energy consumption, running time and passenger comfort. For the lower layer, based on the optimized speed profile, an EMS is designed, using dynamic programming. The boundary range calculation of state variables for the dynamic programming is carried out in advance, based on the working mode analysis to reduce the computation load. In addition, a supervisory controller is developed to achieve reliable real-time control. Finally, to verify the proposed method, real rail line data in China are used as a case study, and the results show that the proposed method offers the better energy and tramway efficiency.(c) 2022 Elsevier Ltd. All rights reserved.