BATTERY STATE ESTIMATING DEVICE AND BATTERY STATE ESTIMATING METHOD

• US 20130116954A1
• Filed: 07/19/2011
• Published: 05/09/2013
• Est. Priority Date: 07/20/2010
• Status: Active Grant

• Current Assignee: Nissan Motor Co., Ltd.
• Original Assignee: Nissan Motor Co., Ltd.
• Inventors: Tazoe, Kazuhiko, Nakamura, Hideo, Umeki, Shiho
• Granted Patent: US 9,720,046 B2
• Time in Patent Office: Days
• US Class Current: 702/63
• CPC Class Codes: G01R 31/367 Software therefor, e.g. for battery testing using modelling or look-up tables
• CPC Class Codes: G01R 31/3842 combining voltage and current measurements
• CPC Class Codes: G06F 17/00 Digital computing or data processing equipment or methods, specially adapted for specific functions information retrieval, database structures or file system structures therefor G06F16/00
• CPC Class Codes: Y02E 60/10 Energy storage using batteries

Abstract

A battery state estimating device being one aspect of the present invention detects a current and a terminal voltage of a secondary battery, estimates a terminal voltage of the secondary battery which is based on a predetermined battery model by using measured values I(k) and V(k) respectively of the detected current and the detected terminal voltage, and sequentially identifies a parameter φ̂(k) of the battery model in such a way that the difference between a value based on the measured value of the terminal voltage and an estimate value of the terminal voltage converges to zero. Then, when a certain parameter φ_n in the identified parameter is equal to or larger than a predetermined first threshold δ1, the battery state estimating device performs upper limit processing of setting the value of the certain parameter φ_n to the first threshold δ1.

Claims

1. A battery state estimating device comprising:

a current detecting part configured to detect a current flowing through a secondary battery as a measured current value;

a voltage detecting part configured to detect a terminal voltage of the secondary battery as a measured voltage value;

an identification calculation part configured to

estimate a terminal voltage of the secondary battery which is based on a battery model of the secondary battery, as an estimated voltage value on the basis of the measured current value and the measured voltage value with the battery model defined as shown in Formula (17) where the measured voltage value is V, the measured current value is I, s is a differential operator, and A(s) and B(s) are polynomial functions of the differential operator s, and

perform sequential identification calculation of sequentially identifying parameters of the battery model in such a way that a difference between a value based on the measured voltage value and the estimated voltage value converges to zero; and

a limit processing part configured to

determine whether, among the parameters identified by the identification calculation part, a highest-degree term parameter corresponding to a coefficient of a term with the highest degree in a polynomial s·

A(s) of the Formula (17) is equal to or larger than a predetermined first threshold, and

perform upper limit processing of setting a value of the highest-degree term parameter to the first threshold when the highest-degree term parameter is equal to or larger than the first threshold.

2. The battery state estimating device according to claim 1, further comprising an open circuit voltage estimating part configured to estimate an open circuit voltage of the secondary battery on the basis of the parameters identified by the identification calculation part, wherein

the open circuit voltage estimating part estimates the open circuit voltage by using a value subjected to the upper limit processing by the limit processing part as the highest-degree term parameter among the parameters identified by the identification calculation part.

3. The battery state estimating device according to claim 2, wherein the identification calculation part performs the sequential identification calculation of the parameters by using, as the highest-degree term parameter, a value before being subjected to the upper limit processing by the limit processing part.

4. The battery state estimating device according to claim 1, further comprising an initializing part configured to

judge whether the highest-degree term parameter is equal to or larger than a second threshold larger than the first threshold, and

execute initialization processing of causing the identification calculation part to perform the sequential identification calculation by using a predetermined initial value when the highest-degree term parameter is equal to or larger than the second threshold.

5. The battery state estimating device according to claim 1, wherein the limit processing part sets the first threshold depending on a battery temperature.

6. The battery state estimating device according to claim 4, wherein the initializing part sets the second threshold depending on a battery temperature.

7. The battery state estimating device according to claim 5, wherein the limit processing part sets the first threshold to a larger value as the battery temperature becomes lower.

8. The battery state estimating device according to claim 6, wherein the initializing part sets the second threshold to a larger value as the battery temperature becomes lower.

9. A battery state estimating method comprising:

detecting a current flowing through a secondary battery as a measured current value;

detecting a terminal voltage of the secondary battery as a measured voltage value;

estimating a terminal voltage of the secondary battery which is based on a battery model of the secondary battery, as an estimated voltage value on the basis of the measured current value and the measured voltage value, with the battery model defined as shown in the Formula (18) where the measured voltage value is V, the measured current value is I, s is a differential operator, and A(s) and B(s) are polynomial functions of the differential operator s;

sequentially identifying parameters of the battery model in such a way that a difference between a value based on the measured voltage value and the estimated voltage value converges to zero;

determining whether, among the identified parameters, a highest-degree term parameter corresponding to a coefficient of a term with the highest degree in a polynomial s·

A(s) of the Formula (18) is equal to or larger than a predetermined first threshold; and

performing upper limit processing of setting a value of the highest-degree term parameter to the first threshold when the highest-degree term parameter is equal to or larger than the first threshold.

10. The battery state estimating method according to claim 9, wherein an open circuit voltage of the secondary battery is estimated by using a value subjected to the upper limit processing as the highest-degree term parameter among the identified parameters.

11. The battery state estimating method according to claim 10, wherein when the parameters of the battery model are sequentially identified, the sequential identification calculation of the parameters is performed by using, as the highest-degree term parameter, a value before being subjected to the upper limit processing.

12. The battery state estimating method according to claim 9, wherein

it is determined whether the highest-degree term parameter is equal to or larger than a second threshold larger than the first threshold, and

the sequential identification calculation of the parameters is performed by using a predetermined initial value when the highest-degree term parameter is equal to or larger than the second threshold.

13. The battery state estimating method according to claim 9, wherein the first threshold is set depending on a battery temperature.

14. The battery state estimating method according to claim 12, wherein the second threshold is set depending on a battery temperature.

15. The battery state estimating method according to claim 13, wherein the first threshold is set to a larger value as the battery temperature becomes lower.

16. The battery state estimating method according to claim 14, wherein the second threshold is set to a larger value as the battery temperature becomes lower.

17. A battery state estimating device comprising:

current detecting means for detecting a current flowing through a secondary battery as a measured current value;

voltage detecting means for detecting a terminal voltage of the secondary battery as a measured voltage value;

identification calculation means for

estimating a terminal voltage of the secondary battery which is based on a battery model of the secondary battery, as an estimated voltage value on the basis of the measured current value and the measured voltage value with the battery model defined as shown in Formula (19) where the measured voltage value is V, the measured current value is I, s is a differential operator, and A(s) and B(s) are polynomial functions of the differential operator s, and

performing sequential identification calculation of sequentially identifying parameters of the battery model in such a way that a difference between a value based on the measured voltage value and the estimated voltage value converges to zero; and

limit processing means for

determining whether, among the parameters identified by the identification calculation means, a highest-degree term parameter corresponding to a coefficient of a term with the highest degree in a polynomial s·

A(s) of the Formula (19) is equal to or larger than a predetermined first threshold, and

performing upper limit processing of setting a value of the highest-degree term parameter to the first threshold when the highest-degree term parameter is equal to or larger than the first threshold.