An Energy Management Strategy For Hybrid Electric Bus Based On MLD-MPC

As one of the modern society civilization marks, vehicles make the lives of people more comfortable and convenient, whereas at the same time, they also bring people serious environmental pollution and energy consumption. To reduce these two problems, almost all the countries are developing new energy vehicles, with the characters of low energy-consumption and cleanliness. As the first one achieved volume production among new energy vehicles, Hybrid Electric Vehicle (HEV) is still believed to be the mainstream in the future. The bus is the primary public transportation, so developing Hybrid Electric Bus (HBS) can reduce the energy-consumption and emission of pollution, as well as playing an exemplary role. However, the present HBS mainly uses logic-based energy management strategy, which cannot fully bring out the potential of HBS in energy saving and emission reduction. To further improve the HBS's fuel economy and reduce emissions of pollution, this paper presents an Energy Management Strategy for HBS based on MLD-MPC (Mixed Logic Dynamical, MLD). The main contents are summarized as follows.1. Parameters matching of Hybrid Electric Bus powertrain. Based on actual survey data of bus line, using vehicle theoretical knowledge and vehicle simulation software ADVISOR, reasonable parameters are matched for single-shaft parallel HEB powertrain, so as to meet the power and economic performance index of the bus. Meanwhile, using the data file as the data base for further research on energy management strategy.2. Establishing the MLD model for HEB powertrain system. Through data fitting, the non-linear model of engine fuel efficiency and battery's SOC(state of charge) is changed into a piecewise linear model; the physical laws, logical rules, operating constraints, and inspiring information of the hybrid buses in each working mode are transformed into the form of mixed integer linear inequalities. On the basis of the above work, the MLD model of HEB's powertrain system is established. 3. Designing the Energy Management strategy of HEB based on MLD-MPC. A receding-horizon and feedback strategy is employed to resist random disturbances and make up model mismatches. The problem of solving the MLD-MPC is turned into a MILP (mixed integer linear programming) problem, and then the problem was solved and analyzed.In this paper, the proposed HBS's energy management strategy has fully considered the interweave character of HBS. Besides, the rolling optimization is made to resist the random disturbances and make up model mismatches. Compared with the electrical-assist energy management strategy, it shows that the presented approach improved fuel economy and reduced emissions.