METHOD AND SYSTEM FOR CONTROLLING ENERGY STORAGE DEVICE

• US 20130169234A1
• Filed: 12/28/2011
• Published: 07/04/2013
• Est. Priority Date: 12/28/2011
• Status: Active Grant

• Current Assignee: General Electric Company
• Original Assignee: General Electric Company
• Inventors: Chuah, Christopher James, Bull, Roger, Sudworth, James, Boccanfuso, Vincent, James, David
• Granted Patent: US 9,147,910 B2
• Time in Patent Office: Days
• US Class Current: 320/136
• CPC Class Codes: G01R 31/3842 combining voltage and current measurements
• CPC Class Codes: G01R 31/392 Determining battery ageing or deterioration, e.g. state of health
• CPC Class Codes: H01M 10/44 Methods for charging or discharging circuits for charging H02J7/00
• CPC Class Codes: H01M 10/443 in response to temperature
• CPC Class Codes: H01M 10/448 End of discharge regulating measures
• CPC Class Codes: H01M 10/48 Accumulators combined with arrangements for measuring, testing or indicating the condition of cells, e.g. the level or density of the electrolyte constructional details of current conducting connections for detecting conditions inside cells or batteries, e.g. details of voltage sensing terminals, H01M50/569
• CPC Class Codes: H01M 10/486 for measuring temperature
• CPC Class Codes: Y02E 60/10 Energy storage using batteries

Abstract

A system and method of use including a controller responsive to a deviation in absolute value or relative slope and operable to terminate a discharge operation in an energy storage device is provided. The absolute value or relative slope is determined at sampling frequency based upon a combination of measured operating parameters, for example, potential and current. Any deviation in the absolute value or relative slope indicates that a threshold limit in the available energy of the system has been reached, for example when active materials in the device are at a point of depletion, indicating a need to cease the discharge operation. The system and method operate on a real-time basis, providing instantaneous SOH information with regard to the device.

Claims

1. A management system, comprising:

a measurement device configured to be operably coupled with an energy storage device for measuring two or more operating parameters of the energy storage device; and

a controller configured to determine discharge effectiveness indicators of the energy storage device from the measured operating parameters at a designated frequency;

wherein the controller is further configured to assess at least one of relative slopes or absolute values of the discharge effectiveness indicators for instantaneous detection of a deviation in one of the relative slopes or absolute values representing a threshold limit of a state-of-charge of the energy storage device, and at least one of signal an end of a discharge operation for the energy storage device or terminate the discharge operation responsive to the detection.

2. The system according to claim 1, wherein the absolute values and relative slopes are based on instantaneous measurements of the operating parameters of potential and charge.

3. The system according to claim 2, wherein the discharge effectiveness indicators are defined by the expression:

DischEff=V*Int(Idt)

wherein;

V* is potential; and

dt is differential operator of time;

and the definition of the relative slope of the discharge effectiveness indicators is defined by the expression;

RelSlope(k)=DischEff(k)−

DischEff(k−

1)/Ah(k)−

Ah(k−

1)

wherein;

k is the index for the presently derived parameter; and

k−

1 is the index for the previously derived parameter.

4. The system according to claim 1, wherein the absolute values and relative slopes are based on instantaneous measurements of the operating parameters of resistance and time.

5. The system according to claim 4, wherein the discharge effectiveness indicators are defined by the expression:

6. The system according to claim 1, wherein the threshold limit of the state-of-charge of the energy storage device correlates to an end-of-discharge state of the energy storage device.

7. The system according to claim 1, wherein the threshold limit is reached when active materials in the energy storage device are at a point of depletion.

8. The system according to claim 7, wherein the threshold limit is reached when a state-of-charge of the energy storage device is between about 1% to about 10% of a true capacity state-of-charge of the energy storage device prior to initiation of the discharge operation.

9. The system according to claim 1, wherein the measurement device is configured to be operably coupled with the energy storage device having one or more cells or units, and the controller is configured such that the deviation in the relative slopes or absolute values is independent of variations in the cells or units of one or more of state-of-health, operating temperature, or variations resulting from manufacturing.

10. A system according to claim 1, wherein the energy storage device is an electrochemical device having mixed chemistry.

11. A method for controlling an energy storage system, the method comprising:

(a) initiating a discharge operation in an energy storage system that is in operable communication with a controller;

(b) measuring potential and current;

(c) the controller performing an instantaneous calculation based on the measurements in step (b) to determine a discharge effectiveness indicator;

(d) generating an energy curve from the step (c) calculations and determining at least one of an absolute value or a relative slope of the discharge effectiveness indicator;

(e) repeating steps (b)-(d) at a sampling frequency until a deviation in the at least one of the absolute value or the relative slope is detected; and

(f) upon detecting the deviation in the at least one of the absolute value or the relative slope, the controller either signaling that the energy storage system is near end-of-discharge, terminating the discharge operation of the energy storage system, or doing both.

12. The method of claim 11, wherein the sampling frequency comprises at least 100 times over the period of the discharge operation.

13. The method of claim 11, wherein the discharge effectiveness indicator determined in step (d) provides an instantaneous measure of the current state of health of the energy storage system.

14. The method of claim 11, wherein the deviation in the at least one of the absolute value or the relative slope correlates to an end-of-discharge state of the energy storage system.

15. The method according to claim 11, wherein the discharge effectiveness indicator is defined by the expression:

DischEff=V*Int(Idt)

wherein;

V* is potential; and

dt is differential operator of time;

and the definition of the relative slope of the discharge effectiveness indicator is defined by the expression;

RelSlope(k)=DischEff(k)−

DischEff(k−

1)/Ah(k)−

Ah(k−

1)

wherein;

k is the index for the presently derived parameter; and

k−

1 is the index for the previously derived parameter.

16. The method according to claim 11, wherein the discharge effectiveness indicator is defined by the expression:

17. The method of claim 11, wherein discharge effectiveness indicator is based on discharge resistance and capacity as determined from the measurements from step (b), and the deviation is a positive change in the relative slope of the energy curve.

18. The method of claim 11, wherein the energy storage system comprises one or more cells or units and detecting the threshold limit is accomplished independent of variations in the cells or units of one or more of state-of-health, operating temperature, or variations resulting from manufacturing.

19. The method of claim 11, wherein terminating the discharge operation upon detecting the deviation in the at least one of the absolute value or in the relative slope prevents over-discharge of the energy storage system.

20. A method for determining state-of-health of an energy storage system, the method comprising:

(a) initiating a discharge operation in an energy storage system that is in operable communication with a controller;

(b) measuring at least two operating parameters of the energy storage system;

(c) the controller performing calculations based on the measurements in step (b) to determine a discharge effectiveness indicator;

(d) generating an energy curve from the step (c) calculations;

(e) repeating steps (b)-(d) at a sampling frequency during the discharge operation; and

(f) assessing the state-of-health of the energy storage system from the energy curve generated in step (d).

21. The method of claim 20, wherein the method further includes the steps of:

(g) detecting a deviation in the energy curve generated in step (d); and

(h) the controller either signaling that the energy storage system is near an end-of-discharge, terminating the discharge operation of the energy storage system, or doing both.

22. The method of claim 20, wherein the at least two parameters include potential and current.

23. The method of claim 21, wherein the sampling frequency comprises at least 100 times during the discharge operation from initiation to end-of-discharge.

24. The method of claim 21, wherein the energy storage system comprises one or more cells or units and detecting the end-of-discharge is accomplished independent of variations in the cells or units of one or more of state-of-health, operating temperature, or variations resulting from manufacturing.

25. The method of claim 21, wherein terminating the discharge operation upon detecting the deviation in the energy curve prevents over-discharge of the energy storage system.

26. A management system, comprising:

a measurement device configured to be operably coupled with an energy storage device for measuring two or more operating parameters of the energy storage device during a discharge operation; and

a controller configured to periodically determine a discharge effectiveness indicator of the energy storage device from the measured operating parameters;

wherein the controller is further configured, when the discharge effectiveness indicator is determined, to detect a deviation in at least one of a relative slope or an absolute value of the discharge effectiveness indicator, the deviation representative of an end of discharge threshold limit of the energy storage device, and at least one of signal an end of the discharge operation or terminate the discharge operation responsive to detecting the deviation.

27. The management system of claim 26, wherein the discharge effectiveness indicator is determined at a regular interval of seconds, n, wherein n is a positive real number.

28. The management system of claim 27, wherein the regular interval of seconds, n, is determined based on a number of times, m, during an average length of the discharge operation, t, that the discharge effectiveness indicator is to be calculated, such that n=t/m.