Power Distribution Strategy Of Electric Vehicle Composite Power Supply Considering Regenerative Energy Efficiency

This paper focuses on the limitation of battery life and regeneration efficiency of single-power regenerative braking system,and studies the regenerative braking energy utilization efficiency of a composite power system composed of supercapacitors and batteries.After the introduction of supercapacitors,on the one hand,the path and loss of energy transmission are changed,and it affect the energy flow analysis and regenerative energy recovery rate;on the other hand,the regenerative braking force and power distribution strategy greatly affect the comprehensive efficiency of energy storage system and vehicle energy utilization.In addition,most current power allocation strategies can only passively accept demand loads,and cannot plan energy flow in advance for upcoming operating conditions.Aiming at the above problems,this paper studies the allocation strategy of the composite power system considering the regenerative braking energy utilization efficiency.The main contents of this paper are:Firstly,based on the composition of the composite power regenerative braking system,a hydraulic braking system model,a regenerative motor model,a super capacitor model,a lithium battery model,and a DC / DC converter model are established.The internal loss of the composite power system is analyzed,and the main loss factors in the energy transfer process are analyzed through the energy flow analysis of the regenerative braking process,which provides the basis for the subsequent maximum efficiency power allocation strategy and the establishment of energy utilization efficiency indicators.Secondly,on the basis of energy flow analysis,with the goal of maximizing energy utilization efficiency,consider braking stability,safety,motor efficiency and other factors to develop a regenerative braking force distribution strategy.Based on this,using the loss analysis model of the energy storage system,a power allocation strategy with the largest comprehensive energy utilization efficiency is proposed,and the regenerative braking energy utilization efficiency indicators suitable for the composite power system and different test conditions are derived.By comparing different allocation strategies,the effects of dual power systems on the regenerative braking energy flow of electric vehicles and the energy utilization efficiency of the proposed strategy are verified.Finally,according to the national standard condition data,the driving mode is identified offline by support vector machine classification method,and the input-output hidden Markov model and Gaussian mixture model are integrated to establish the speed prediction model under urban,suburban and expressway conditions,and predict the future short-term speed sequence according to the real-time collected vehicle condition signal.The dynamic programming algorithm is used to determine the power distribution coefficient,and the energy distribution strategy of dual power system based on short-term and imminent speed prediction is proposed to optimize the energy utilization efficiency.Through the simulation and comparison under the condition of reorganization test,it is verified that the speed prediction model can predict the change trend of vehicle speed,and the power strategy based on the short-term and imminent speed prediction can realize the optimization of super capacitor and lithium battery energy management.Finally,the index of renewable energy utilization efficiency proves the improvement of energy efficiency.