Energy Conservation Analysis And Evaluation For Typical Series-parallel Hybrid Electric Bus

Along with the development of hybrid-electric technology, bus-manufacturers are trying to find a hybrid electric system configuration which has great potential on the energy saving. However, the research in comprehensive energy conservation analysis method for hybrid electric system is not common at present. Therefore, the problems faced by enterprises cannot be solved. To solve this phenomenon, based on the national "863" project and the National Natural Science Foundation Project,the paper established a system of energy conservation analysis and evaluation for hybrid electric bus, and the energy saving potential research and evaluation method was proposed. The parameters matching method and the energy conservation control algorithm were researched thoroughly by taking three kinds of typical series-parallel hybrid electric buses in China as the research object. According to the research above, the maximum energy saving potential of hybrid electric buses adopting different configuration schemes were ascertained. Evaluation of energy saving performance on parameter matching scheme and control strategy was carried out, based on the research of energy saving potential for different configuration schemes of series-parallel hybrid electric bus.The optimum parameter matching scheme and the optimal control strategy are the basis of the research of energy-saving potential of serial-parallel hybrid electric bus. The paper proposed a parameter matching method of serial-parallel hybrid system based on the combination of power, torque and efficiency, which took assembly primary and secondary relationships in the system as matching sequence,from power, torque and efficiency of the three aspects to match hybrid electric system assembly, the efficiency matching as a core of the parameter matching scheme designing. Based on control strategy algorithm, ideal efficiency characteristics of the engine and motors was designed by predicting the targetoperating points, completing the optimum parameters matching design. In the development of optimal control strategy, the dynamic programming algorithm was optimized, with the equivalent fuel consumption as step cost function, and optimal equivalent coefficients of fuel-electric conversion were calculated as weight coefficients with secants iterative algorithm. The optimal logic threshold control strategy of series-parallel hybrid electric system was established based on improved dynamic programming algorithm and genetic algorithm. Combined the optimum parameter matching scheme and the optimal control strategy, the simulation maximum energy-saving potential of switched, single axis and planetary series-parallel hybrid electric bus were calculated through united simulation.As a core of the system of energy conservation analysis and evaluation for hybrid electric bus, energy saving evaluation method was proposed to meet the technology requirement of configuration design on series-parallel hybrid electric bus.Evaluation of energy saving potential on configuration scheme and energy saving performance on different energy saving ways was carried out. Based on processing analyze data of energy saving potential with efficacy coefficient method, the energy saving potential and the energy saving performance of hybrid electric systems adopting different configuration schemes was evaluated directly. Based on analyzing the reasons for the differences in energy saving performance of different configurations, energy saving characteristics of series-parallel hybrid electric bus with different configurations and the variation tendency of energy saving potential with different technical conditions were summarized. Taking the switched series-parallel hybrid electric bus as an example, the road test data was analyzed and evaluated by energy saving evaluation method, investigating the problems in parameter matching and control strategy, proposing corresponding improving suggestions, providing significant guidance and reference for developing and producing of hybrid electric bus.