Method for estimating SOC of lithium battery

Abstract

The invention discloses a method for estimating an SOC of a lithium battery. The method comprises the following steps of (S1) obtaining an SOH value of the battery, and determining the current maximum available capacity CN of the battery; (S2) calculating a current SOC value of the battery online by using an ampere-hour integral method; (S3) starting a corresponding offline model parameter according to a sampling temperature T and an estimated value of the current SOC of the battery, and calculating current open-circuit voltage OCV by combining the current sampling current I and terminal voltage U; (S4) obtaining a real value SOC (t)* of the current SOC of the battery according to the estimated value of the current SOC of the battery in the step (S2), the current open-circuit voltage OCV in the step (S3) and an OCV-SOC calibration curve; (S5) correcting the current estimated SOC value of the ampere-hour integral method by using the real value SOC (t)* of the current SOC of the battery, and further carrying out calculation by using the ampere-hour integral method; and (S6) repeating the steps (S3), (S4) and (S5). According to the method, piecewise correction is carried out on a traditional algorithm for estimating the SOC by the ampere-hour integral method, an accumulative error of the ampere-hour integral method is effectively eliminated, and the estimation accuracy of the SOC is improved.

Description

technical field [0001] The invention relates to the field of electric vehicle battery management systems, in particular to a method for estimating the SOC of a lithium battery. Background technique [0002] In recent years, with the deteriorating air quality and the scarcity of oil resources, new energy vehicles, especially pure electric vehicles, have become the development hotspots of major automobile companies in the world today. The power battery pack is a key component of an electric vehicle. The power battery SOC is used to directly reflect the remaining power of the battery. It is an important basis for the vehicle control system to formulate an optimal energy management strategy. Accurate estimation of the power battery SOC value is important for improving battery safety and reliability. It is of great significance to improve battery energy utilization and prolong battery life. [0003] At present, the commonly used SOC estimation methods mainly include open circuit...

AI Technical Summary

Problems solved by technology

The ampere-hour integration method has the advantages of low cost and convenient measurement, but it also has the following problems in the application of electric vehicles: it needs to use other methods to obtain the initial value of SOC; the accuracy of current measurement has a decisive impact on the accuracy of SOC estimation; The error cannot be eliminated. If the charging and discharging time is too long during a calculation, the accumulated error may lead to unreliable estimation results.

The neural network method also has shortcomings: a large amount of data is required for training, and the training data and training methods have a greater impact on the estimation accuracy

[0007] The core idea of ​​the Kalman filter method is to make an optimal estimate of the state of the dynamic system in the sense of the least mean square. The advantage of the Kalman filter lies in its strong error correction ability, but the disadvantage is that the estimation accuracy is highly dependent on the accuracy of the battery model.

Images