Lithium ion battery stage of charge (SOC) mixed estimation method

Abstract

The invention discloses a lithium ion battery stage of charge (SOC) mixed estimation method. The method comprises the following steps that step 1, whether a model-based method or an OCV-based method is adopted to estimate an SOC initial value is judged according to a comparison result of a battery placement time T and a standing time T2 of the battery, or SOC estimation is directly performed by adopting a coulomb counting method to obtain an SOC estimation value, and the SOC estimation time T0 is obtained simultaneously; and step 2, when the SOC estimation time T0 does not exceed the long drift time T1 of the battery, the estimation is ended; when the SOC estimation time T0 is larger than the long drift time T1 of the battery, the calibration of the SOC initial value is started, the SOC estimation is carried out again by adopting the coulomb counting method according to the calibrated SOC initial value, and a new SOC estimation value is obtained. By combining the coulomb counting method, the OCV-based method and the model-based method, the SOC can be rapidly and accurately estimated, so that the method is suitable for on-line SOC detection of the lithium ion battery, the accuracy of SOC estimation under different conditions is improved, and the service life of the battery is prolonged.

Description

technical field [0001] The invention belongs to the field of estimating the state of charge of a battery, in particular to a hybrid estimating method for SOC of the state of charge of a lithium-ion battery. Background technique [0002] With the development of smart grids and electric vehicles, the management of battery energy storage systems plays an increasingly important role. Lithium batteries have the advantages of long cycle life, high charging efficiency, and good safety performance. They are widely used in electric vehicles and smart grid industries. Among them, the estimation of the state of charge (SOC) is essential for extending battery life and ensuring the safety of smart grids and electric vehicles. Normal and safe work is of great significance. [0003] At present, some achievements have been made in the research of SOC estimation methods, mainly including open circuit voltage method (OCV), ampere-hour integration method, load voltage method, internal resista...

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Problems solved by technology

[0004] The CC method is to obtain the estimated value of SOC by integrating the load current. The method is simple and easy to implement, and has good accuracy within a certain period of time. However, the initial state of charge and discharge must be known for each estimation, and the Coulomb efficiency is affected by the working state. The impact is large, and the current measurement is inaccurate, which will cause SOC estimation errors and long-term drift problems; the OCV-based method is a relatively accurate and relatively simple SOC estimation method, which can weaken the interference caused by inaccurate battery charge and discharge estimates. But it depends on the function of OCV-SOV, and this function relationship will also change with the aging of the battery, and when estimating SOC based on the OCV method, the battery needs to be left for a long time, usually more than two hours, not Suitable for online applications; the model-based method has high accuracy and needs to accurately identify the parameters of the equivalent circuit model (ECM), and these parameters will be affected by battery aging, temperature and SOC changes. This type of method is commonly used based on Karl Mann filter, sliding mode observer, etc.

At present, there have been researches on mixing several methods to improve the accuracy of battery SOC estimation, but the calculation is relatively complicated and the amount of calculation is large, which is not suitable for online applications.

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