Sop Estimation Of Lithium-ion Battery Based On Multi-state And Multi-constraint

Lithium ion batteries are the main power and core components of electric vehicles.Its comprehensive,efficient and perfect battery energy management system(BMS)is the most difficult point in current research.In order to ensure the safety and efficiency of BMS,accurate and rapid estimation of battery status is the basis.At present,the characterization of the battery state mainly depends on the state of charge(SOC),state of health(SOH),state of power(SOP),temperature state(SOT),and state of energy(SOE).Among them,the battery power state SOP has gradually become a research hotspot as an important indicator to characterize the battery power performance.SOP is one of the important parameters for electric vehicles to ensure safety performance and improve braking energy recovery.It can be used to determine the extreme value of the power that the battery can absorb or release during charging and discharging in different states to prevent the battery from being overcharged.However,the battery SOP is greatly disturbed by uncertain factors such as ambient temperature,state of charge(SOC),state of health(SOH),and has a strong nonlinearity.Real-time accurate SOP estimation is very difficult and challenging.The specific research work carried out in this paper for the SOP estimation of vehicle-mounted lithium-ion batteries includes:High-precision lithium-ion battery model: By introducing the basic principles of fractional calculation and three commonly used definitions,the characteristics of lithium-ion batteries are analyzed from the perspective of electrochemical impedance spectroscopy.BTS-5V100 A is used as the main charging and discharging device for lithium ion batteries,and has a thermostat.Other equipment has established a Lithium-ion battery cell test platform and an experimental database of Wanxiang A123 batteries.According to the principles of electrochemistry and circuit,on the basis of the original second-order RC model,a constant phase angle element is used to replace the ideal capacitor,and a Walberg element with low frequency characteristics of the reaction impedance spectrum is added.Establish a fractional equivalent circuit model.Then,the improved hybrid particle swarm optimization(HPSO)is used to identify the parameters of the model,the adaptability and accuracy of the fractional equivalent circuit model,and the parameter identification method of the lithium-ion battery under different working conditions has been verified,Laid a model foundation for the estimation of lithium ion battery SOP.Highly robust SOC estimation method: A state-space equation is used to establish a discrete control system for lithium-ion batteries as the basis for deriving the SOC estimation algorithm.In order to solve the shortcomings of the extended Kalman filter algorithm,an SOC estimation method based on H∞ filter algorithm is proposed,and its design ideas and operation logic are introduced in detail.In the MATLAB /Simulink simulation environment,the fractional equivalent circuit model and the complete establishment of the two algorithms are realized,and the battery SOC estimation simulation based on the H∞ filter algorithm and the extended Kalman filter algorithm is compared to achieve lithium ion under different SOC The battery SOP estimate laid the foundation.SOH estimation method considering capacity attenuation: Study the aging mechanism of lithium-ion batteries during the cycle charge and discharge process,analyze the internal and external factors of battery performance decay,establish a capacity decay model that reflects battery aging,and use particle filter algorithm to update the model parameters to achieve the battery capacity Predict,so as to realize the estimation of battery health state SOH.Based on the cyclic charge and discharge experimental data of Wanxiang A123 battery and NASA’s lithium ion battery aging experimental data,the proposed SOH estimation method was verified,which laid the foundation for the realization of SOP estimation of lithium ion batteries under different SOH.SOP estimation method under multi-state and multi-constraint conditions:The definitions of peak power and SOP are clarified.A multi-state and multi-constrained SOP estimation method based on fractional-order equivalent circuit model is proposed for the shortcomings of HPC-based SOP estimation method based on mixed pulse power performance test.On the basis of the health state SOH,the state of charge SOC,current and voltage of the lithium ion battery are used as constraints to predict the power extreme value during the battery charge and discharge process,and the current power state SOP is estimated.Based on the proposed multi-state and multi-constraint SOP estimation method,the impact of charge and discharge power duration and aging degree on SOP estimation is analyzed,and its adaptability under different working conditions is verified.The results of the method are not reliable enough and too idealized.