Method for Maximum Net Power Calculation for Fuel Cell System Based on Online Polarization Curve Estimation

• US 20090197125A1
• Filed: 02/06/2008
• Published: 08/06/2009
• Est. Priority Date: 02/06/2008
• Status: Active Grant

• Current Assignee: GM Global Technology Operations LLC (General Motors Company)
• Original Assignee: GM Global Technology Operations Incorporated (Motors Liquidation Co. GUC Trust)
• Inventors: Lakshmanan, Balasubramanian, Salvador, John P., Ganapathy, Sriram, Leo, Frank X., Mallavarapu, Kiran
• Granted Patent: US 8,192,879 B2
• Time in Patent Office: Days
• US Class Current: 429/431
• CPC Class Codes: H01M 8/04552 of the individual fuel cell
• CPC Class Codes: H01M 8/04582 of the individual fuel cell
• CPC Class Codes: H01M 8/04619 of fuel cell stacks
• CPC Class Codes: H01M 8/04641 of the individual fuel cell
• CPC Class Codes: H01M 8/04992 characterised by the implementation of mathematical or computational algorithms, e.g. feedback control loops, fuzzy logic, neural networks or artificial intelligence
• CPC Class Codes: Y02E 60/50 Fuel cells

Abstract

An algorithm for determining the maximum net power available from a fuel cell stack as the stack degrades over time using an online adaptive estimation of a polarization curve of the stack. The algorithm separates the current density range of the stack into sample regions, and selects a first sample region from the far left of the estimated polarization curve. The algorithm then calculates the cell voltage for that current density sample region, and determines whether the calculated cell voltage is less than or equal to a predetermined cell voltage limit. If the calculated cell voltage is not less than the cell voltage limit, then the algorithm selects the next sample region along the polarization curve. When the calculated cell voltage does reach the cell voltage limit, then the algorithm uses that current density for the sample region being analyzed to calculate the maximum power of the fuel cell stack.

Claims

1. A method for estimating the maximum stack power from a fuel cell stack during operation of the fuel cell stack, said method comprising:

selecting an average cell voltage limit for an average fuel cell in the fuel cell stack;

selecting a minimum cell voltage limit for a minimum performing fuel cell in the fuel cell stack;

estimating a separate polarization curve of the fuel cell stack for both an average cell voltage and a minimum cell voltage;

separating a current density range of the fuel cell stack into a predetermined number of sample regions in ascending order;

selecting a first sample region;

determining an average cell voltage and a minimum cell voltage at the current density for the selected sample region;

determining whether the cell voltage is less than the predetermined average cell voltage limit and the minimum cell voltage limit;

selecting a next sample region in the current density range if the cell voltage is not less than the average cell voltage limit or the minimum cell voltage limit;

calculating a maximum net power for both the average cell voltage and the minimum cell voltage if the cell voltage is less than average cell voltage limit or the minimum cell voltage limit; and

selecting the lesser of the average cell voltage maximum net power and the minimum cell voltage maximum net power as the maximum stack power.

2. The method according to claim 1 wherein calculating the net power includes calculating the net power as the maximum cell voltage times the overall current density times the number of fuel cells times the area of the fuel cells of the fuel cell stack minus predetermined parasitic power that are used while running the fuel cell stack.

3. The method according to claim 2 further comprising adding a correction to the calculated maximum power.

4. The method according to claim 1 wherein determining an average cell voltage and a minimum cell voltage includes using the equation:

5. The method according to claim 1 wherein the average cell voltage limit is about 0.525 V and the minimum cell voltage limit is about 0.3 V.

6. The method according to claim 1 wherein separating a current density range of the fuel cell stack into a predetermined number of sample regions includes separating a current density range of 0.1-2.0 A/cm² into sample regions of 0.1 A/cm².

7. The method according to claim 1 wherein selecting a next sample region in the current density range includes selecting the next sample region in order from a low current density in the range to a high current density in the range.

8. The method according to claim 1 wherein the fuel cell stack is a split fuel cell stack where the maximum stack power is determined for both spilt stacks.

9. A method for estimating the maximum stack power from a fuel cell stack during operation of the fuel cell stack, said method comprising:

selecting at least one cell voltage limit for a fuel cell in the fuel cell stack;

estimating a polarization curve of the fuel cell stack for at least one cell;

separating a current density range of the fuel cell stack into a predetermined number of sample regions;

selecting a first sample region;

determining a cell voltage at the current density for the selected sample region;

determining whether the cell voltage is less than the predetermined cell voltage limit;

selecting a next sample region in the current density range if the cell voltage is not less than the cell voltage limit; and

calculating a maximum net power for the cell voltage if the cell voltage is less than the cell voltage limit.

10. The method according to claim 9 wherein selecting at least one cell voltage limit includes selecting an average cell voltage limit for an average fuel cell in the fuel cell stack and a minimum cell voltage limit for a minimum performing fuel cell in the fuel cell stack, and wherein estimating a polarization curve of the fuel cell stack includes estimating a polarization curve for both the average cell voltage and the minimum cell voltage, and wherein determining a cell voltage includes determining an average cell voltage and a minimum cell voltage at the current density for the selected sample region.

11. The method according to claim 9 wherein calculating the net power includes calculating the net power as the maximum cell voltage times the overall current density times the number of fuel cells times the area of the fuel cells of the fuel cell stack minus predetermined parasitic power that are used while running the fuel cell stack.

12. The method according to claim 11 further comprising adding a correction to the calculated maximum power.

13. The method according to claim 9 wherein determining the cell voltage includes using the equation:

14. The method according to claim 9 wherein separating a current density range of the fuel cell stack into a predetermined number of sample regions includes separating a current density range of 0.1-2.0 A/cm² into sample regions of 0.1 A/cm².

15. A system for estimating the maximum stack power from a fuel cell stack during operation of a fuel cell stack, said system comprising;

means for selecting an average cell voltage for an average fuel cell in the fuel cell stack;

means for selecting a minimum cell voltage for a minimum performing fuel cell in the fuel cell stack;

means for estimating a polarization curve of the fuel cell stack for both an average fuel cell and a minimum fuel cell voltage;

means for separating a current density range of the fuel cell stack into a predetermined number of sample regions;

means for selecting a first sample region;

means for determining an average cell voltage and a minimum cell voltage at the current density for the selected sample region;

means for determining whether the cell voltage is less than the predetermined average cell voltage limit and the minimum cell voltage limit;

means for selecting a next sample region in the current density range if the cell voltage is not less than the average cell voltage limit or the minimum cell voltage limit;

means for calculating a maximum net power for both the average cell voltage and the minimum cell voltage if the cell voltage is less than the average cell voltage limit and the minimum cell voltage limit; and

means for selecting the less of the average cell voltage maximum net power and the minimum cell voltage maximum net power as a maximum stack power.

16. The system according to claim 15 wherein the means for calculating the net power includes means for calculating the net power as the maximum cell voltage times the overall current density times the number of fuel cells times the area of the fuel cells of the fuel cell stack minus predetermined parasitic power that are used while running the fuel cell system.

17. The system according to claim 15 wherein the average cell voltage limit is about 0.525 V and the minimum cell voltage limit is about 0.3 V.

18. The system according to claim 15 wherein separating a current density range of the fuel cell stack into a predetermined number of sample regions includes separating a current density range of 0.1-2.0 A/cm² into sample regions of 0.1 A/cm².

19. The system according to claim 15 wherein the fuel cell stack is a split fuel cell stack where the maximum stack power is determined for both spilt stacks.

20. The system according to claim 15 wherein the means for selecting a next sample region in the current density range includes means for selecting the next sample region in order from a low current density in the range to a high current density in the range.