Research On Energy Management Strategy Of Compound Energy Source For Electric Vehicle

Since the "Made in China 2025" plan was officially launched in 2015,the new energy automobile industry has become the focus of all the social circles.Lithium battery is widely used as the power source in electric vehicles because of its natural advantages,such as: high energy density.However,due to the limitation of its internal energy storage structure,Lithium battery can not meet the chaotic and transient power requirements in the process of sudden acceleration and deceleration operations.The compound energy source system combines the high-power density ultracapacitor with the high-energy density lithium battery,which overcomes the technical defects caused by using lithium battery as the single power source unit.The research object of this paper is the compound energy source composed of lithium battery and ultracapacitor.Firstly,the composition and topology of the compound energy source system are analyzed.The energy management strategy based on the wavelet transform and fuzzy control is proposed and the dynamic programming algorithm is used to obtain the global optimal solution under the typical drive cycle.By analyzing the law of power output distribution of lithium battery according to the optimal energy consumption,the fuzzy control process is further optimized.The energy management strategy is verified by ADVISOR simulation software and electric vehicle hardware test bench respectively.The main contents of this paper are as follows:(1)Composition and topology analysis of compound energy source.Firstly,the working characteristics of lithium battery and ultracapacitor are analyzed and mathematical models are established.A suitable system topology is selected and the simulation model of the composite energy source system is constructed in ADVISOR simulation software.(2)Research on energy management strategy based on wavelet transform and fuzzy control.The wavelet transform algorithm is used to extract the chaotic and transient components from power requirement signal and then allocates to the ultracapacitor,Lithium battery is responsible for low frequency power requirement.The fuzzy control is used to optimize the results of wavelet transform so as to ensure the energy in the system flow reasonably.(3)The secondary energy allocation strategy based on dynamic programming.The dynamic programming algorithm is utilized to minimize the energy consumption of lithium battery and super capacitor during the whole driving cycle.The state of charge of ultracapacitor is considered as the state variable and the minimum energy consumption of lithium battery and ultracapacitor is the optimization target.The fuzzy rules of fuzzy controller are modified by analyzing the global optimal solution obtained from dynamic programming algorithm to achieve further optimization.(4)To verify the energy management strategy by simulation software and hardware test platform.Using the simulation software ADVISOR to verify the effectiveness of energy management strategy under the typical drive cycle UDDS and ECE.The hardware test platform is established in the laboratory and the energy management strategy is further verified.