Research On State Of Charge Estimation And Failure Process Analysis Of Battery For EMU

With the continuous advancement of the maintenance procedures of "Hexiehao" EMU represented by CRH2 C,a large number of batteries have approached the design life,the available capacity of batteries has decreased in varying degrees,and the probability of energybased failure has gradually increased.The traditional off-line detection method has been difficult to meet the real-time requirements of battery condition monitoring.Therefore,based on the goal of reducing the maintenance cost of battery and prolonging the service life of battery,the in-depth research is carried out on battery capacity monitoring,battery energy-based failure process analysis and reducing the probability of battery energy-based failure,the work is as follows:(1)Based on the analysis of the electrochemical principle,performance parameters and working environment of battery for EMU,some output characteristics of battery are experimentally studied through open circuit voltage characteristic experiment and coulomb efficiency characteristic experiment.The high-order nonlinear relationship between battery open circuit voltage and state of charge is analyzed quantitatively;It is verified that the coulomb efficiency of battery is correlated with discharge current and state of charge,which provides experimental data support for the estimation of state of charge of battery for EMU.(2)On the premise of obtaining some output characteristics of the battery,the characteristics of common state of charge estimation methods are analyzed.An improved SOC ampere hour integral estimation method suitable for the battery of EMU is proposed by combining the traditional ampere hour integral method with the open circuit voltage method and introducing the temperature and coulomb efficiency compensation coefficient.By building MATLAB / Simulink simulation model and battery charge and discharge experimental platform,the estimation method is simulated and experimentally verified.Under the conditions of constant current and variable current,the relative error of the state of charge estimation value is controlled within 5%,which has good accuracy and can meet the needs of battery capacity monitoring for EMU.(3)Based on the analysis of the internal and external factors that can lead to energy-based failure of battery for EMU,the simulation experiment of single battery failure process and the simulation experiment of battery pack failure process are designed.By analyzing the failure simulation experimental data,the energy-based failure process from single battery to battery pack is restored,and it is clear that the plate failure is the key factor leading to battery failure;Through the statistical analysis of battery voltage and electrolyte level data,the corresponding relationship between electrolyte level and battery failure process is obtained.Through the investigation of battery production line,the internal factors that can lead to plate failure are analyzed,and the influence of external factors on battery energy-based failure is analyzed in combination with the operation of EMU.Based on the conclusion of failure simulation experiment and maintenance requirements,the improvement measures that can reduce the probability of energy-based failure of battery are put forward in two aspects: battery maintenance and EMU operation.