Application Of Global Optimized Energy Management Strategy For PHEV Based On Pseudo-Spectrum Method Under WLTC Cycle Conditions

Plug-in hybrid electric vehicles(PHEV)is one of the important research and development directions of new energy vehicles,which combines the advantages of pure electric vehicles(EVs)that can be charged by external power grid and the long range of traditional hybrid electric vehicles(HEVs).The global optimal energy management strategy plays an important role in the selection of power system and parameter matching in the initial stage of PHEV development.Aiming at the problems of existed global optimization algorithms,the scholar has proposed a set of global optimal energy management strategies based on Radau pseudospectral splicing method,and applied it to the calculation of global fuel consumption under NEDC suburban cycle conditions.This method has fast calculation speed and high accuracy,which supports the parameter matching and configuration selection of related enterprises.However,considering the progress of national laws and regulations,enterprises should make simulation analysis and fuel consumption calculation based on WLTC cycle conditions.The mode switching strategy in the original scheme does not meet the requirements of WLTC mode switching.In order to better adapt to the research and development of PHEV models under complex WLTC cycle conditions,cooperative enterprises need a new energy management strategy based on global optimization algorithm.Based on the school-enterprise cooperation project and a series-parallel PHEV provided by the enterprise,this paper uses the Equivalent Consumption Minimization Strategy(ECMS)to solve the minimum fuel consumption and divide the initial mode of WLTC cycle working condition,and applies the pre-partition of the mode to Radau pseudospectral splicing method,thus obtains a set of global optimal energy management strategy which can be used to solve optimal fuel economy under WLTC cycle working condition.The main work of this paper is as follows:A series-parallel PHEV backward simulation model is established.Considering the mapping relationship between input and output characteristics of power components,the steady-state response models of engine,ISG motor and drive motor and the variable capacity model of power battery are established by experimental modeling method,which provides a model basis for the research of instantaneous optimization algorithm and global optimization algorithm.Taking the instantaneous minimum fuel consumption under WLTC cycle condition as the optimization objective,an ECMS algorithm model is constructed.In order to ensure that the SOC value under working conditon B returns to the initial value,the concept of global oil-electricity conversion coefficient is introduced and the dichotomy is used to converge the oilelectricity conversion coefficient.The relationship between vehicle speed and oil-electricity conversion coefficient in different stages of WLTC is discussed.Finally,the minimum fuel consumption are calculated and the switching time between the different modes under complete WLTC cycle conditions are obtained,which lays a foundation for the mode prepartition and initial assignment of the global optimization algorithm.A global optimal energy management strategy based on Radau pseudospectral splicing method is constructed.Taking NEDC suburban cycle as an example,the switching time,state variables and control variables are obtained by using ECMS algorithm.The pre-divide initial mode and the initial value is applied to Radau pseudospectral splicing method.By comparing the solution results with the multi-group solution results based on experience,the Radau pseudospectral splicing method based on ECMS mode pre-dividing is validated for its good fuel economy and applicability.The influence of initial value of Radau pseudospectral splicing method on the solution results is discussed.Based on the ECMS method,the WLTC cycle conditions are pre-partitioned.The Radau pseudospectral splicing method based on the pre-partitioning of the ECMS method is used to solve the fuel consumption under WLTC cycle conditions.The results obtained by using ECMS algorithm alone are compared.The applicability and superiority of the global optimal energy management strategy to solve the optimal fuel economy under complex conditions are verified.Finally,the switching rule of PHEV mode under working condition B is explored based on the solution results.