Estimation and compensation of battery measurement and asynchronization biases

• US 10,124,696 B2
• Filed: 12/14/2016
• Issued: 11/13/2018
• Est. Priority Date: 12/06/2013
• Status: Active Grant

• Current Assignee: Ford Global Technologies, LLC (Ford Motor Company)
• Original Assignee: Ford Global Technologies, LLC (Ford Motor Company)
• Inventors: Li, Yonghua, Anderson, Richard Dyche
• Primary Examiner(s): Mawari, Redhwan K
• Assistant Examiner(s): Torchinsky, Edward
• Application Number:
  US15/378,732
• Publication Number:
  US 20170096077A1
• Time in Patent Office: 699 Days
• Field of Search: None
• CPC Class Codes: B60L 2240/547 Voltage
• CPC Class Codes: B60L 2240/549 Current
• CPC Class Codes: B60L 2260/44 by parameter estimation
• CPC Class Codes: B60L 58/12 responding to state of charge [SoC]
• CPC Class Codes: B60L 58/21 having the same nominal voltage
• CPC Class Codes: B60W 10/26 for electrical energy, e.g. batteries or capacitors
• CPC Class Codes: B60W 2510/244 Charge state
• CPC Class Codes: B60W 2710/248 Current for loading or unloading
• 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: G01R 31/389 Measuring internal impedance, internal conductance or related variables
• CPC Class Codes: G01R 31/396 Acquisition or processing of data for testing or for monitoring individual cells or groups of cells within a battery
• CPC Class Codes: H01M 10/482 for several batteries or cells simultaneously or sequentially
• CPC Class Codes: H01M 10/486 for measuring temperature
• CPC Class Codes: H01M 2220/20 Batteries in motive systems, e.g. vehicle, ship, plane
• CPC Class Codes: Y02E 60/10 Energy storage using batteries
• CPC Class Codes: Y02T 10/70 Energy storage systems for electromobility, e.g. batteries

Abstract

A hybrid or electric vehicle includes a traction battery to store and provide energy for the vehicle. The traction battery includes a number of battery cells. For effective operation of the traction battery, operating parameters, such as state of charge and battery power limits, may need to be known. The operating parameters may be a function of battery cell voltage and impedance parameters. A parameter estimation scheme may use measured cell voltages and a measured traction battery current as inputs. A current measurement bias may be modeled that incorporates measurement bias caused by asynchronous current and voltage measurements. The current measurement bias may be estimated for each cell and the value may differ between cells.

Claims

1. A vehicle comprising:

a traction battery including a plurality of cells; and

a controller programmed to implement a state estimator configured to estimate, for each cell, a current measurement bias specific to the cell that depends on a temporal difference between current and voltage measurements for the cell, and operate the traction battery according to battery power limits derived from voltage parameters that are based on the current measurement bias, wherein at least some of the current measurement biases have different values.

2. The vehicle of claim 1, wherein the voltage parameters are further based on an error between a measured cell terminal voltage and an estimated cell terminal voltage.

3. The vehicle of claim 1, wherein the controller is further programmed to operate the traction battery according to a battery state of charge defined by output of the state estimator.

4. The vehicle of claim 1, wherein voltage parameters include an open circuit voltage for the cell.

5. The vehicle of claim 1, wherein the state estimator is further configured to output, for each cell, impedance parameters based on the current measurement bias specific to the cell.

6. The vehicle of claim 5, wherein the impedance parameters include a resistance associated with the cell.

7. The vehicle of claim 1, wherein the current measurement bias is based on measured cell terminal voltages and a measured traction battery current.

8. The vehicle of claim 1, wherein the state estimator is further configured to apply a forgetting factor to the current measurement bias.

9. A method for controlling a traction battery including a plurality of cells comprising:

implementing, by a controller, a state estimator configured to output voltage parameters for each of the cells based on a current measurement bias specific to each of the cells that depends on a temporal difference between current and voltage measurement for each of the cells; and

operating the traction battery according to battery power limits derived from the voltage parameters.

10. The method of claim 9, wherein at least some of the cells have different values for the current measurement bias.

11. The method of claim 9, wherein the current measurement bias is derived from measured cell terminal voltages and a measured traction battery current.

12. A battery management system comprising:

a controller programmed to implement a state estimator configured to estimate, for each cell of a traction battery, a current measurement bias specific to the cell that depends on a temporal difference between current and voltage measurements for the cell, and operate the traction battery according to battery power limits derived from voltage parameters that are based on the current measurement bias.

13. The battery management system of claim 12, wherein the current measurement bias for at least some of the cells have different values.

14. The battery management system of claim 12, wherein the state estimator is further configured to apply a forgetting factor to the current measurement bias.

15. The battery management system of claim 12, wherein the voltage parameters are further based on an error between a measured cell terminal voltage and an estimated cell terminal voltage.

16. The battery management system of claim 12, wherein the controller is further programmed to operate the traction battery according to a battery state of charge defined by output of the state estimator.

17. The battery management system of claim 12, wherein voltage parameters include an open circuit voltage for the cell.

18. The battery management system of claim 12, wherein the state estimator is further configured to output, for each cell, impedance parameters based on the current measurement bias specific to the cell.

19. The battery management system of claim 18, wherein the impedance parameters include a resistance associated with the cell.

20. The battery management system of claim 12, wherein the current measurement bias is based on measured cell terminal voltages and a measured traction battery current.