Lithium ion battery charge state estimating method

Abstract

The invention relates to a lithium battery charge state estimating method and belongs to the technical field of batteries of electric vehicles. The lithium battery charge state estimating method aims at estimating the charge state of a lithium battery under the complex working conditions of charging and discharging at different multiplying power levels through an estimation method based on a parameter time varying observer. The lithium battery charge state estimating method specifically comprises the step that a battery charge state is regarded as a state variable to be introduced into a lithium ion battery continuous model, the upper limit of hysteresis voltages is determined according to the charging and discharging open-circuit voltage, the battery hysteresis phenomenon is considered to be a first order dynamic process related to the current absolute value, a battery polarization voltage model with parameters changing along with currents and an internal resistance model with parameters changing along with currents are structured through RC rings, battery model end voltages are structured, and a nonlinear parameter time-varying battery model is obtained. The lithium battery charge state estimating method is based on a parameter time-varying lithium ion battery equivalent circuit model, the model parameters are calibrated to be a function of current multiplying power, the characteristics of the battery can be accurately expressed, and meanwhile an existing estimation method can be easily used.

Description

technical field [0001] The invention belongs to the technical field of electric vehicle batteries. Background technique [0002] The battery state of charge (State of Charge, SOC) is used to represent the remaining power of the battery, that is, the percentage of the remaining power to the rated capacity, and its value is theoretically in the range of 0% to 100%. The state of charge of the battery cannot be obtained directly from the battery itself, but can only be estimated indirectly by measuring the external characteristic parameters of the battery pack (such as voltage, current, internal resistance, temperature, etc.). During the use of lithium-ion batteries for electric vehicles, due to the internal complex electrochemical reaction phenomena, the battery characteristics show a high degree of nonlinearity (time-varying parameters of charge and discharge, hysteresis, etc.), which makes it very important to accurately estimate the state of charge of the battery. difficult...

AI Technical Summary

Problems solved by technology

[0004] The purpose of the present invention is to adopt an estimation method based on a parameter time-varying observer to solve the lithium-ion battery state of charge estimation method when the lithium-ion battery is charged and discharged at different rates.

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