Research On Emergency Mutual Charge And Accurate Charge Control Of Electric Vehicles

The construction of electric vehicle charging infrastructure is progressing slowly,far from keeping up with the development speed of electric vehicles,which makes electric vehicles driving on the road because of insufficient power,unable to find charging piles in time,and anchored on the road,affecting the owner’s travel.The current emergency rescue modes for electric vehicles include trailer mode,truck container with battery or generator equipment,etc.,all of which have the problems of long waiting time and high cost.When an electric vehicle is anchored on the road,in theory,other passing electric vehicles with sufficient power can be used to charge the anchored electric vehicle.For this reason,an emergency electric charging device for electric vehicles is designed in this paper,which can meet the mutual charging of electric vehicles with different types of batteries and different voltage levels.The device design,the working mode of the device,and the measurement method of the device are also studied.Based on a non-isolated two-way DC/DC converter and a charging gun that meets national standards,an emergency electric charging device for electric vehicles is designed in this paper.A 230V lithium iron phosphate battery pack simulates a low-voltage electric vehicle and a 532V ternary lithium battery pack High-voltage side electric vehicles,an emergency mutual charging device experimental platform is built,and the battery management system of the high-and low-voltage side battery pack is designed.The BMS of the master-slave control mode is used to make the battery voltage level flexible and controllable.The design and control methods of the bidirectional DC/DC are improved so that the bidirectional DC/DC converter can meet the experimental conditions.On the discharge side in emergency mutual charging,in addition to the basic constant current mode,in order to facilitate accurate billing and management and accurately estimate the range,a constant power discharge mode is proposed.Establish an electric vehicle emergency mutual charging device experimental platform model in simulink of matlab,and simulate the four working modes of the device:constant power boost mode,constant current boost mode,constant power buck mode,and constant current buck mode.The analysis and simulation verified the rationality of the device design,the scientific and feasible control method,and the voltage and current values were all within the safe value range.Based on the parameters set in the simulation,the electric vehicle emergency mutual charging experimental platform is used for experimental analysis.The experimental results are consistent with the simulation results.The design function and use effect of the electric vehicle emergency mutual charging device are verified.The loss is larger than the step-down constant power mode.Compared with the constant current mode,the constant power mode is convenient for calculating the electric energy charged and discharged by the electric vehicle and is convenient for billing.Since there is no research on emergency mutual charging,and there is no relevant national standard or industry standard in the measurement of this aspect,in accordance with the actual situation,this article stipulates that the device loss should be borne by the rescued vehicle,so accurate measurement The electrical energy of the discharged vehicle changes.The traditional SOC value can only estimate the change of the battery charge amount and cannot estimate the change of the battery’s electrical energy.This article estimates the SOE of the high-side ternary lithium battery and compares it with its SOC value.For the same SOC and SOE,before 60%,the change in SOE has more influence on the open-circuit voltage than the change in SOC.After 60%,the result is opposite.And taking the constant power step-down mode as an example,the cost is accurately calculated and the vehicle cruising range is estimated.Finally,the thesis makes conclusions and prospects for the theoretical analysis,simulation analysis and experimental analysis of the full text.