METHOD AND APPARATUS FOR GENERALIZED RECURSIVE LEAST-SQUARES PROCESS FOR BATTERY STATE OF CHARGE AND STATE OF HEALTH

• US 20070159137A1
• Filed: 01/31/2007
• Published: 07/12/2007
• Est. Priority Date: 02/18/2003
• Status: Active Grant

• Current Assignee: GM Global Technology Operations LLC (General Motors Company)
• Original Assignee: GM Global Technology Operations Incorporated (General Motors Company)
• Inventors: Verbrugge, Mark, Tate, Edward, Koch, Brian, Frisch, Damon
• Granted Patent: US 7,373,264 B2
• Time in Patent Office: Days
• US Class Current: 320/132
• CPC Class Codes: G01R 31/006 on road vehicles, e.g. automobiles or trucks testing of ignition installations peculiar to internal combustion engines F02P17/00
• CPC Class Codes: G01R 31/367 Software therefor, e.g. for battery testing using modelling or look-up tables
• CPC Class Codes: G01R 31/374 with means for correcting the measurement for temperature or ageing
• CPC Class Codes: G01R 31/3828 using current integration
• CPC Class Codes: G01R 31/3842 combining voltage and current measurements
• CPC Class Codes: G01R 31/389 Measuring internal impedance, internal conductance or related variables
• CPC Class Codes: G01R 31/392 Determining battery ageing or deterioration, e.g. state of health

Abstract

A method for determining a voltage based or current based state of charge (SOC) and state of health (SOH) of a battery system is provided. The method includes: providing a model of the battery system including an equivalent circuit having both low frequency and high frequency elements; establishing a plurality of functional relationships comprising relationship of the equivalent circuit with SOC; reducing at least part of the plurality of functional relationships into a set of time segmented recursive functional relationships, wherein a state at a first time t can be modeled by a functional presentation of a state at a second time t−Δt that occurred before the first time t; and computing a set of data points based upon the set of time segmented recursive functional relationships using a matrix for operation in matrix algebra.

Claims

1. A method for determining a state of charge (SOC) or state of health (SOH) of a battery system, comprising:

performing a first step including determining a set of initial values for a plurality of parameters, coefficients, and derivatives based upon a plurality of linear functional relationships, and computing a result based upon said determining;

after execution of said first step, calculating a plurality of intermediate functions;

updating said plurality of parameters;

determining a open circuit voltage V_o that possesses a functional relationship with SOC_V;

extracting SOC_V by inverting the expression of V_o(SOC_V);

calculating SOC_C;

calculating a weight for weighting SOC_C and SOC_V; and

calculating SOC.

2. The method of claim 1, wherein said step of calculating SOC_C is based upon the following equation:

3. The method of claim 1, wherein said step of calculating SOC is based upon the following equation:

SOC=w_SOC(SOC_C)+(1−

w_SOC)(SOC_V)

4. The method of claim 1, wherein said step of calculating a weight for weighting SOC_C and SOC_V is based upon the following equation and a table:

w_SOC=1−

α

(Δ

t)

5. The method of claim 1, wherein the weighting factor w_SOC is to be bounded between 0 and 1, and α

is a time increment Δ

t dependent quantity.

6. The method of claim 1, wherein said step of extracting SOC_V by inverting the expression of V_o(SOC_V) includes using a lookup table (LUT).

7. The method of claim 1, wherein said step of determining a open circuit voltage V_o is based upon the following equation:

V_oc=V_o(T,SOC_V)+V_H

8. The method of claim 1, wherein said battery system comprises a five parameter system.

9. The method of claim 1, wherein said step of updating said plurality of parameters is based upon the following equation:

10. The method of claim 1, wherein said step of calculating a plurality of intermediate functions is based upon the following equations:

11. The method of claim 1, wherein said initializing step includes obtaining stored values of parameters obtained from prior analysis.

12. The method of claim 1, wherein said initializing step includes obtaining coefficient values from initial values for battery voltage and current.

13. The method of claim 1, wherein said initializing step includes computing initial intermediate functions based upon the following equations:

s_w|₁=γ

₁
s_u|₁=γ

₁u₁,
s_u,v|₁=γ

₁u₁v₁
and
s_w,s|₁=1
s_1,s|₁→

I_t
s_II,s|₁I_I²

14. The method of claim 1, wherein the parameters satisfy the following matrix relationship:

15. The method of claim 1, including:

determining a first value based upon a skewness test; and

based upon said value, determining a course of action including discarding voltage based SOC_V, and using current based SOC_C as an indication of a SOC said battery system.

16. The method of claim 1, including:

determining a second value based upon a determinant test; and

based upon said value, determining a course of action.

17. The method of claim 1 including computing a recursive power expression based on said data points.

18. The method of claim 17, wherein said power expression is a max discharge and charge power of said battery system.