BATTERY MANAGEMENT SYSTEM AND METHOD OF DRIVING THE SAME

• US 20080054848A1
• Filed: 08/29/2007
• Published: 03/06/2008
• Est. Priority Date: 08/29/2006
• Status: Active Grant

• Current Assignee: Samsung SDI Company Limited
• Original Assignee: Samsung SDI Company Limited
• Inventors: CHO, BO-HYUNG, LEE, YOUNG-JO, LEE, JAE-MOON, YUN, HAN-SEOK, CHOI, SOO-SEOK
• Granted Patent: US 7,847,557 B2
• Time in Patent Office: Days
• US Class Current: 320/134
• CPC Class Codes: G01R 31/3648 comprising digital calculation means, e.g. for performing an algorithm
• CPC Class Codes: G01R 31/367 Software therefor, e.g. for battery testing using modelling or look-up tables
• CPC Class Codes: G01R 31/389 Measuring internal impedance, internal conductance or related variables

Abstract

A battery management system that estimates an internal impedance of a battery, a method of driving the same, a device that estimates an internal impedance of a battery, and a method of estimating the internal impedance of a battery. A method of driving a battery management system that estimates the internal impedance of a battery including a plurality of cells includes generating a battery equivalent model of the battery, receiving a terminal voltage signal and a charge and discharge current signal of the battery, and generating a first discrete signal corresponding to the terminal voltage signal of the battery and a second discrete signal corresponding to the charge and discharge current signal of the battery, and filtering the first discrete signal and the second discrete signal according to a frequency range corresponding to the battery equivalent model so as to estimate the internal impedance of the battery. The device that estimates an internal impedance of a battery filters the first discrete signal and the second discrete signal according to a frequency range corresponding to the battery equivalent model so as to estimate the internal impedance of the battery.

Claims

1. A method of driving a battery management system that estimates an internal impedance of a battery including a plurality of cells, the method comprising:

generating a battery equivalent model of the battery;

receiving a terminal voltage signal and a charge and discharge current signal of the battery;

generating a first discrete signal corresponding to the terminal voltage signal of the battery;

generating a second discrete signal corresponding to the charge and discharge current signal of the battery; and

estimating the internal impedance of the battery by filtering the first discrete signal and the second discrete signal according to a frequency range corresponding to the battery equivalent model.

2. The method of claim 1, wherein the estimating of the internal impedance further comprises:

generating a third discrete signal by filtering the first discrete signal according to the frequency range corresponding to the battery equivalent model; and

generating a fourth discrete signal by filtering the second discrete signal according to the frequency range corresponding to the battery equivalent model.

3. The method of claim 2, wherein the estimating of the internal impedance further comprises:

using a bilinear conversion method to generate the first to fourth discrete signals.

4. The method of claim 2, wherein in the generating of the battery equivalent model comprises:

calculating a first parameter, which represents a resistance overvoltage corresponding to the internal impedance of the battery;

calculating a second parameter, which represents a charge transfer overvoltage;

calculating a third parameter, which represents a diffusion overvoltage; and

calculating a fourth parameter, which represents an open circuit voltage.

5. The method of claim 4, wherein the battery equivalent model comprises:

a first capacitor and a first resistor connected in parallel to represent a charge transfer impedance of the battery;

a second capacitor and a second resistor connected in parallel to represent a diffusion impedance of the battery;

a third resistor to represent a series resistance impedance of the battery; and

an open circuit voltage component to represent an open circuit voltage of the battery.

6. The method of claim 4, further comprising:

dividing the first to fourth parameters according to a frequency domain; and

estimating of the internal impedance further comprises;

filtering the first parameter by using a high-pass filter,

filtering the second parameter by using a band-pass filter, and

filtering the third and fourth parameters by using a low-pass filter.

7. The method of claim 4, further comprising:

dividing the first to fourth parameters according to a frequency domain; and

estimating of the internal impedance further comprises;

filtering the first parameter by using a high-pass filter; and

filtering the second, third, and fourth parameters by using a low-pass filter.

8. The method of claim 6, further comprising:

estimating the first to fourth parameters by using the third discrete signal and the fourth discrete signal; and

estimating a resistor and a capacitor that correspond to the internal impedance of the battery by using the first to fourth parameters.

9. The method of claim 8, further comprising:

estimating the first to fourth parameters by using the third discrete signal and the fourth discrete signal by using a least square estimation method.

10. A battery management system that estimates an internal impedance of a battery including a plurality of cells, the system comprising:

an anti-aliasing low-pass filter that receives a battery terminal voltage signal and a battery terminal current signal and removes aliasing of the battery terminal voltage signal and the battery terminal current signal so as to generate a first signal and a second signal;

a continuous/discrete signal converter that converts the first signal and the second signal from the anti-aliasing low-pass filter into discrete signals according to a sampling time, and thereby generates a first discrete signal corresponding to the first signal and a second discrete signal corresponding to the second signal; and

an impedance estimating unit that estimates the internal impedance of the battery by filtering the first and the second discrete signals according to a frequency range corresponding to a battery equivalent model of the battery.

11. The system of claim 10, wherein the impedance estimating unit further:

generates a third discrete signal by filtering the first discrete signal and a fourth discrete signal by filtering the second discrete signal according to the frequency range corresponding to the battery equivalent model of the battery; and

estimates the internal impedance of the battery by using a third discrete signal and a fourth discrete signal.

12. The system of claim 11, wherein the battery equivalent model includes four parameters, each of which corresponds to the internal impedance of the battery, the four parameters comprising:

a first parameter, which represents resistance overvoltage;

a second parameter, which represents a charge transfer overvoltage;

a third parameter, which represents a diffusion overvoltage; and

a fourth parameter, which represents an open circuit voltage.

13. The system of claim 11, wherein the impedance estimating unit:

divides the four parameters according to a frequency domain; and

filters the first parameter by using a high-pass filter;

filters the second parameter by using a band-pass filter; and

filters the third and the fourth parameters by using a low-pass filter.

14. The system of claim 13, wherein the impedance estimating unit further:

estimates the four parameters by using the third discrete signal and the fourth discrete signal; and

estimates a resistor and a capacitor that correspond to the internal impedance of the battery using the four parameters.

15. An impedance estimating device that estimates an internal impedance of a battery including a plurality of cells, the device comprising:

a low-pass filter to filter a first discrete signal corresponding to a terminal voltage of the battery and a second discrete signal corresponding to a charge and discharge current of the battery, and thereby obtain a diffusion overvoltage, a charge transfer current, and an open circuit voltage of the battery; and

a high-pass filter to filter the first discrete signal and the second discrete signal and thereby obtain a resistance overvoltage and a resistance current of the battery.

16. The device of claim 15, further comprising:

a band-pass filter to filter the first discrete signal and the second discrete signal and thereby obtain a charge transfer overvoltage of the battery.

17. The device of claim 15, wherein:

the low-pass filter is used to filter the first discrete signal and the second discrete signal and thereby obtain a charge transfer overvoltage of the battery.

18. The device of claim 17, wherein:

the low-pass filter and the high-pass filter are digital filters.

19. The device of claim 18, wherein the device further comprises:

a calculation unit to estimate the internal impedance of the battery by using the overvoltages and the currents obtained by filtering the first discrete signal and the second discrete signal.

20. The device of claim 19, wherein the calculation unit further:

uses a least square method to estimate the internal impedance of the battery by using the overvoltages and the currents obtained by filtering the first discrete signal and the second discrete signal.

21. The device of claim 20, wherein the calculation unit further:

determines the diffusion overvoltage, the charge transfer current, the open circuit voltage, the resistance overvoltage, the resistance current of the battery, the charge transfer overvoltage and the charge transfer current of the battery of the battery by using the internal impedance of the battery.

22. A method for estimating an internal impedance of a battery, the method comprising:

generating a battery equivalent model of the battery;

measuring a battery terminal voltage;

measuring a battery charge and discharge current when the battery is charged and discharged;

using the battery terminal voltage and the battery charge and discharge current to calculate the value of parameters of the battery equivalent model; and

estimating the internal impedance of the battery from the parameters of the battery equivalent model.

23. The method of claim 22, wherein the battery equivalent model is:

divided into a charge transfer resistance of the battery, a diffusion impedance of the battery, a series resistance of the battery, and an open circuit voltage of the battery.

24. The method of claim 23, wherein the battery equivalent model comprises:

a first capacitor and a first resistor connected in parallel to represent the charge transfer resistance of the battery;

a second capacitor and a second resistor connected in parallel to represent the diffusion impedance of the battery;

a third resistor to represent the series resistance of the battery; and

an open circuit voltage component to represent the open circuit voltage of the battery.

25. The method of claim 24, wherein the method further comprises:

dividing the battery terminal voltage measurement and the battery charge and discharge current measurement into frequency ranges corresponding to the charge transfer resistance of the battery, the diffusion impedance of the battery, the series resistance of the battery, and the open circuit voltage of the battery.