Research And Implementation Of SOC Monitoring Method For Heavy Truck Load Power Battery Of Fuel Cell

The mass and load of the fuel cell heavy truck are relatively large,and the driving conditions are complex and changeable.In order to meet the instantaneous dynamic response and energy saving requirements of the fuel cell heavy truck,the hybrid power system is needed to provide power for it.Lithium ion power battery has become an important auxiliary power source for heavy weight of fuel cell due to its advantages of large specific energy,high specific power,less self-discharge,good cycle characteristic and fast discharge.As auxiliary power supply of fuel cells,heavy card,lithium ion power battery charged state of(SOC)estimation is not only the important basis of power battery energy management system,and it is the fuel cell heavy card is one of the important input of the vehicle control strategy,the estimation accuracy of power battery life and the effectiveness and accuracy of the vehicle energy management has important influence.Due to the special application scenarios and complex working conditions of fuel cell heavy trucks,temperature,charging and discharging rate and other factors have a great impact on the capacity of the battery pack,large voltage differences and SOC differences tend to occur between single batteries,leading to the decrease of SOC estimation accuracy.Second,due to the slow dynamic response of the fuel cell system,power battery have the effect of peak "cut",the instantaneous output or to absorb higher power,the working mechanism and all-electric vehicle power battery has a bigger difference,in the use of traditional method for estimating the state of charged for fuel cell heavy truck load power battery SOC larger error in the estimates.Therefore,it is of great significance to study the SOC estimation method applicable to fuel cell heavy truck load power cell for the promotion and development of fuel cell heavy truck.This subject is a major special project of shanxi provincial science and technology department: Heavy fuel cell power system and the vehicle integration technology project(20181102009)as the backing,with high power fuel cell heavy card as the research object,in order to improve the fuel cell heavy truck load power battery SOC estimation accuracy as the goal,to no trace traditional kalman filter(UKF)algorithm in the fuel cell heavy card power battery charged to estimate the state of(SOC),ignoring the particularity of working environment and requirements,because the battery model parameters are not accurate and advance to the estimation error caused by the increasing noise statistical properties,The real-time estimation method and realization of SOC of fuel cell heavy truck power cell were studied.Mainly completed the following work:(1)through the analysis and comparison of the types,principles and characteristics of fuel cell vehicles and auxiliary energy,combined with the vehicle parameters and dynamic performance indicators of the fuel truck in this topic,the appropriate type was selected and the power system was designed to match.(2)in view of the heavy fuel card power battery caused by multiple input multiple output model parameter time-varying problem,affected the accuracy of algorithm based on second-order RC battery model,the expansion of state variables of the 4 d equation of state,by moving the ohm internal resistance R into state variables to actually update tracking is achieved,so as to improve the accuracy of the battery model and correction of the SOC estimation.(3)in view of the complex load of fuel heavy truck-loaded power cells,this paper introduces a new forgetting factor on the basis of the traditional trackless kalman filter algorithm,and constructs a sliding mode observer to estimate the covariance of unknown noise in real time,so as to reduce the interference of uncertain noise.An improved AUKF algorithm is presented to estimate the battery SOC.(4)pulse charge and discharge experiments of single batteries at different temperatures were designed,and it was verified that the improved AUKF algorithm had strong applicability and stability for SOC under different temperature conditions,especially under low temperature environment.Compared with the traditional UKF algorithm,the accuracy and stability of SOC were greatly improved,which met the practical application requirements.(5)to establish a simplified model of the lithium iron phosphate battery pack,in the improvement of monomer battery SOC estimation algorithm on the basis of,and completed the research in view of the battery pack SOC estimation algorithm,lithium iron phosphate battery pack were collected in the experiment,the data such as current,voltage,on the basis of combining with no trace kalman filter estimation algorithm is proposed in this paper for power battery pack SOC estimation,SOC estimation,compared with the experiment the SOC obtained the theoretical value,in order to verify the feasibility of this method.(6)the overall design of the SOC estimation system of fuel heavy card is explained.Hardware circuits such as power supply module,voltage acquisition module,current acquisition module and communication function module are designed and programmed for each module,so as to realize the SOC estimation of fuel cell heavy truck power battery in this paper.The study of this paper is of great significance for improving the accuracy of SOC estimation,improving the effectiveness of auxiliary energy management,providing a basis for the fuel cell heavy calorie energy management system,and improving the dynamic performance of the vehicle.