Method for estimating SOC (state of charge) of equalized batteries

A technology for balancing circuits and balancing currents, which is applied in the direction of measuring electricity, measuring electrical variables, measuring devices, etc., and can solve problems such as estimation error of battery state of charge and difficulty in accurate measurement of balanced current.

Active Publication Date: 2012-08-22
CHINA AVIATION LITHIUM BATTERY LUOYANG
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  • Abstract
  • Description
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Problems solved by technology

[0003] The purpose of the present invention is to solve the problem of battery state of charge (SOC) estimation error caused b

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  • Method for estimating SOC (state of charge) of equalized batteries
  • Method for estimating SOC (state of charge) of equalized batteries
  • Method for estimating SOC (state of charge) of equalized batteries

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[0031] The specific embodiments of the present invention will be further described below in conjunction with the drawings.

[0032] Battery pack charge equalization circuit such as figure 1 As shown, we take the balance between the battery pack and battery 2 cells as an example to illustrate the specific implementation process of the algorithm. At this time, close the switch S2 and the main switch Sp of the converter T, and the balance current Is on the balance circuit of the battery 2 unit , The current on the line is the charging current Ic. In order to well characterize the static and dynamic characteristics of lithium batteries during equilibrium. will figure 1 The equilibrium model is refined and simplified into figure 2 Shown is the balanced battery model and its equivalent circuit. In this model, the battery is equivalent to an ideal power source E and an internal resistance R1. The DC / DC converter is regarded as an inductor L. The impedance of the balanced circuit is R2 ...

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Abstract

The invention relates to a method for estimating the SOC (state of charge) of equalized batteries. The method includes steps of estimating the SOC of the batteries before battery equalization by ampere-hour integration; creating an equalized battery equivalent model and an equivalent circuit; combining an ampere-hour method on the basis of the equalized battery model, and creating a corresponding mathematical model; discretizing the mathematical model to obtain a state-space equation; and estimating the state of charge of voltage at a battery end by an extended Kalman filter algorithm, and finally obtaining an estimation value of the SOC of the equalized battery. By the aid of the method, the SOC of equalized current and a battery or a battery pack can be accurately estimated when a battery management system starts equalization, accumulated battery SOC estimation errors of the ampere-hour method can be eliminated, and noise further can be suppressed.

Description

technical field [0001] The invention belongs to an electric vehicle battery management system, in particular to an SOC estimation method of a balanced battery. Background technique [0002] The battery management system is an important part of electric vehicles, and one of its main functions is to realize the online estimation of the state of charge (SOC) of the battery pack. The ampere-hour integral method and the Kalman filter method are the most widely used SOC online estimation methods in engineering. When charging and discharging a lithium-ion power battery system with multiple cells connected in series, there is a problem of energy difference between each cell, which leads to unbalanced battery cells and shortened battery life. Therefore, it is necessary to balance this difference through equalization control. The balance control circuit between the battery pack and the cell that is actively balanced has been proposed, but when the system turns on the balance, the cur...

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Application Information

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IPC IPC(8): G01R31/36
Inventor 周长文
Owner CHINA AVIATION LITHIUM BATTERY LUOYANG
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