Energy Management Strategy For Hybrid Commercial Vehicles Considering Battery Performance Degradation

The vigorous development of new energy vehicles is the unavoidable direction of change and strategic choice of the global automotive industry in light of the worsening energy crisis and environmental issues.Commercial vehicles now have a greater significance and value due to their high fuel consumption and new energy emissions.The plug-in hybrid electric vehicle(PHEV),which is a type of new energy vehicle,is a bridge between conventional vehicles and pure electric vehicles.It has a rechargeable battery and a pure electric drive mode,which can reduce emissions and achieve energy savings,as well as ease range anxiety.As a result,academia has given it a great deal of attention.In this paper,we propose an energy management strategy for PHEV commercial vehicles with the main goal of improving fuel economy,while taking into account the performance degradation and replacement cost of the power battery pack,and propose a PHEV energy management strategy that takes into account the battery performance degradation,and conduct the following three aspects of research:(1)Based on the prototype parameters of a plug-in hybrid commercial vehicle,the key parameters of the power system including engine,drive motor,power battery pack and transmission ratio are calculated and selected,based on which the numerical models of engine fuel consumption rate and motor efficiency as well as the Rint model of lithium iron phosphate battery monoblock are constructed;(2)Introduction to the structure and workings of lithium iron phosphate batteries is followed by a discussion of the internal and external factors affecting battery performance,with a particular emphasis on the effects of depth of discharge and charge/discharge multiplier on lithium-ion battery performance.Then,300 cycle life tests with different discharge depths and different discharge multipliers were conducted on Li Fe PO4 14500 battery cells using Digatron’s battery testing equipment,and a battery degradation model based on discharge depth and discharge multiplier was established for revealing the changes of battery capacity with discharge depth and discharge multiplier respectively.(3)An adaptive equivalent fuel consumption minimization energy management strategy for PHEV commercial vehicles is constructed.The strategy is based on the battery performance degradation model established in Chapter 3,and the total cost of fuel consumption and battery effective amp-hour throughput loss is considered by introducing the severity factor MAP,and the trade-off coefficients of fuel consumption and battery degradation are determined by Pareto optimization.The mitigation effect of the strategy on the battery performance degradation is analyzed by taking WLTC typical operating conditions as an example.The results show that the designed strategy can reduce the effective ampere-hour throughput by 46.5% at a trade-off factor of 0.9,and the charge/discharge multiplier is lower compared to the trade-off factor of 1,which can significantly slow down the battery performance degradation.Simulation results of the adaptive equivalent fuel consumption minimization strategy and the dynamic planning strategy are compared at a trade-off factor of 0.9 to further validate the effectiveness of the strategy.