Proximal Policy Optimization Based Intelligent Energy Management for Plug-In Hybrid Electric Bus Considering Battery Thermal Characteristic

As the performances of energy management strategy (EMS) are essential for a plug-in hybrid electric bus (PHEB) to operate in an efficient way. The proximal policy optimization (PPO) based multi-objective EMS considering the battery thermal characteristic is proposed for PHEB, aiming to improve vehicle energy saving performance while ensuring the battery State of Charge (SOC) and temperature within a rational range. Since these three objectives are contradictory to each other, the optimal tradeoff between multiple objectives is realized by intelligently adjusting the weights in the training process. Compared with original PPO-based EMSs without considering battery thermal dynamics, simulation results demonstrate the effectiveness of the proposed strategies in battery thermal management. Results indicate that the proposed strategies can obtain the minimum energy consumption, fastest computing speed, and lowest battery temperature in comparison with other RL-based EMSs. Regarding dynamic programming (DP) as the benchmark, the PPO-based EMSs can achieve similar fuel economy and outstanding computation efficiency. Furthermore, the adaptability and robustness of the proposed methods are confirmed in UDDS, WVUSUB and real driving cycle.