Correctional DP-Based Energy Management Strategy of Plug-In Hybrid Electric Bus for City-Bus Route

Typical plug-in hybrid electric buses (PHEBs) with a fast-charged lithium titanate battery, which might fulfill about 70% of the distance of a representative city-bus route, have been adopted in many Chinese cities. Considering that the detailed information of the driving cycle could be deduced with the historical driving data and online estimation methods, there might be an opportunity for applying the dynamic programming (DP)-based global optimal energy management strategy for these PHEBs. However, road slopes or variable loads might induce transient fluctuations of the driving resistance in a given driving cycle. Meanwhile, the single-shaft parallel configuration, with automatic mechanical transmission (AMT), might constrain the implementability of the optimal energy distribution from a DP-based strategy. Therefore, in this paper, a novel correctional DP algorithm is brought forward to balance the optimization of fuel economy and drivability. Simulation results demonstrate that, integrated with the correctional logic of AMT gear shifting, the proposed energy management strategy can guarantee that the engine and the electric machine work in the high-efficiency area with optimal energy distribution, while keeping drivability in the variation of road slope and loads. The proposed method might give a technical solution to these typical PHEBs with a lower cost system configuration of the powertrain in China.