Research on lithium battery SOC estimation method based on Thevenin model and unscented Kalman filter

Abstract

The invention relates to an unscented Kalman SOC (state of charge) estimation method, which is characterized in that Kalman filtering can be applied to SOC estimation of a lithium ion battery pack with an obvious nonlinear relationship by utilizing unscented transformation on the basis of a Kalman filtering algorithm, so that effective iterative computation of an SOC value of the lithium ion battery pack is realized; an SOC initial value error and an accumulated error existing in ampere-hour integration are overcome; aiming at the Kalman ignorance high-order term, the estimation precision is low, the stability is poor, the unscented Kalman does not ignore the high-order term, and the precision is high; the Thevenin equivalent circuit model is established, so that the defect that the internal resistance model cannot represent the dynamic characteristics of the lithium battery is overcome to a certain extent, RC is added to represent the polarization effect in the battery, and a better representation effect on the battery is achieved. According to the method, on the basis of fully considering lithium ion battery grouping work, an iterative calculation process based on Kalman is improved on the basis of an equivalent model circuit, and establishment of an SOC estimation model of a lithium ion battery pack and reliable operation of a mathematical iterative operation algorithm of anSOC value are realized.

Description

Technical field[0001]The present invention relates to an unscented Kalman method for estimating the SOC of a lithium ion battery. Aiming at the accurate estimation target of the SOC value of a lithium ion battery pack, the method proposes an unscented Kalman filter method, which is based on the Kalman filter algorithm. Use unscented changes to determine sampling points near the estimated points, use these sample points to represent the Gaussian density approximate state probability density function, use unscented transformation to deal with the nonlinear transfer problem of mean and covariance, which can be applied to obvious nonlinearities Relational lithium-ion battery pack SOC estimation realizes effective iterative calculation of lithium-ion battery pack SOC value, overcomes the cumulative error of SOC initial value error and ampere-hour integral; for Kalman, high-order terms are ignored, making the estimation accuracy low and stable The determination of poor performance, Unscen...

AI Technical Summary

Problems solved by technology

[0005] The purpose of the present invention is to overcome the deficiencies of the existing lithium-ion battery pack SOC estimation method, provide a lithium-ion battery pack SOC estimation method based on unscented Kalman, and solve the problem of accurate estimation of the SOC value in lithium-ion battery pack applications

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