Research On Energy Management Strategy Of PEMFC And Battery Hybrid Bus Based On ECMS

With the advantages of high efficiency,zero emission and low noise,PEMFC and battery hybrid system are considered to be the key development direction of new energy vehicles in the future.In order to solve the problems of slow dynamic response and inability to recover braking energy of PEMFC,the PEMFC and battery are formed into a PEMFC and battery hybrid system to give full play to their respective advantages.A rational energy management strategy is an important way to improve the economy of the vehicle and optimize the output characteristics of the PEMFC.In this thesis,the energy management strategy of the PEMFC and battery hybrid bus is optimized to address the problems of excessive penalty of the penalty function based on the fixed SOC reference value in the equivalent hydrogen consumption minimization strategy and the dependence of the battery’s power maintenance capacity on the penalty function.The main studies are as follows:(1)In order to optimize the energy management strategy,the advantages and disadvantages of different power system topologies are explained,and the PEMFC and battery hybrid system topology is determined.The mathematical models of vehicle longitudinal dynamics and power system components of drive motor,PEMFC and battery are established.Based on the mathematical models,a PEMFC and battery hybrid bus model is built using MATLAB and the validity of the model is verified.The simulation results showed that the hydrogen consumption of the built model was 8.2 kg per 100 km,and the relative error with the measured hydrogen consumption of 8 kg per 100 km was 2.5%,which satisfied the accuracy requirement and could be used for the subsequent simulation study of energy management strategy.(2)Aiming at the problem of excessive penalty in the A-ECMS based on fixed SOC feedback,an A-ECMS is proposed to design the adaptive SOC reference value by determining the SOC reference value at different stages with the recovered energy in kinematic segments through theoretical analysis of the shortcomings of the use of fixed SOC reference value in the traditional strategy.Under NEDC conditions and real vehicle collection conditions,the PEMFC and battery hybrid bus model established in the previous chapter is used as the study object.By comparing the simulation results before and after optimization,it is shown that the economy of the optimization method in this paper is improved by 3.93%compared with the traditional method on the basis of maintaining the power balance.(3)To address the problem that the power maintenance capability in the aforementioned strategy requires the design of a complex penalty function,the complexity of the strategy is reduced by obtaining the optimal equivalent factor that can maintain the power balance.The relationship between the optimal equivalent factor and the optimal control result is obtained through theoretical analysis of the physical meaning of the equivalent factor and the simplification of the instantaneous equivalent factor,and the method of obtaining the instantaneous optimal equivalent factor based on the combination of dynamic programming algorithm and equivalent hydrogen consumption minimization algorithm is proposed.The simulation results of various typical working conditions show that the equivalent hydrogen consumption minimization strategy based on the optimization theory has 4.2%improvement over the previous strategy on the basis of maintaining the power balance,and achieves the approximate dynamic planning optimal control result,which achieves further optimization of the energy management strategy.