Fuel cell stack monitoring and system control

• US 20040151955A1
• Filed: 01/07/2004
• Published: 08/05/2004
• Est. Priority Date: 07/06/1999
• 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: Clingerman, Bruce J., Keskula, Donald H., Doan, Tien M.
• Granted Patent: US 6,847,188 B2
• Time in Patent Office: Days
• US Class Current: 429/13
• CPC Class Codes: B60L 58/30 for monitoring or controlling fuel cells
• CPC Class Codes: B60L 58/34 by heating
• CPC Class Codes: H01M 16/006 of fuel cells with rechargeable batteries
• CPC Class Codes: H01M 8/04223 during start-up or shut-down; Depolarisation or activation, e.g. purging; Means for short-circuiting defective fuel cells
• CPC Class Codes: H01M 8/04225 during start-up
• CPC Class Codes: H01M 8/04228 during shut-down
• CPC Class Codes: H01M 8/04302 applied during start-up
• CPC Class Codes: H01M 8/04303 applied during shut-down
• CPC Class Codes: H01M 8/04365 of other components of a fuel cell or fuel cell stacks
• CPC Class Codes: H01M 8/04559 of fuel cell stacks
• CPC Class Codes: H01M 8/04567 of auxiliary devices, e.g. batteries, capacitors
• CPC Class Codes: H01M 8/04589 of fuel cell stacks
• CPC Class Codes: H01M 8/04597 of auxiliary devices, e.g. batteries, capacitors
• CPC Class Codes: H01M 8/04679 of fuel cell stacks
• CPC Class Codes: H01M 8/04955 Shut-off or shut-down of fuel cells
• 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: H01M 8/0612 from carbon-containing material
• CPC Class Codes: Y02E 60/10 Energy storage using batteries
• CPC Class Codes: Y02E 60/50 Fuel cells
• CPC Class Codes: Y02T 90/40 Application of hydrogen technology to transportation, e.g. using fuel cells

Abstract

A control method for monitoring a fuel cell stack in a fuel cell system in which the actual voltage and actual current from the fuel cell stack are monitored. A preestablished relationship between voltage and current over the operating range of the fuel cell is established. A variance value between the actual measured voltage and the expected voltage magnitude for a given actual measured current is calculated and compared with a predetermined allowable variance. An output is generated if the calculated variance value exceeds the predetermined variance. The predetermined voltage-current for the fuel cell is symbolized as a polarization curve at given operating conditions of the fuel cell. Other polarization curves may be generated and used for fuel cell stack monitoring based on different operating pressures, temperatures, hydrogen quantities.

Claims

1. In a method for operating a fuel cell system having a fuel processor which supplies a hydrogen-rich stream to a stack of fuel cells, wherein said hydrogen reacts with an oxidant to supply electrical power to an external load, the improvement comprising:

(a) monitoring actual voltage and actual current from the fuel cell stack;

(b) determining an expected magnitude of voltage as a function of said actual current based on a predetermined relationship between voltage and current;

(c) calculating a variance value between said actual voltage and said expected voltage magnitudes; and

(d) generating a signal if said calculated variance value exceeds a predetermined variance value.

2. The method of claim 1 wherein before step (d), establishing different predetermined variance values for different loads.

3. The method of claim 1 wherein before step (d), establishing different predetermined variance values for different fuel cell stack operating parameters.

4. The method of claim 3 wherein said different fuel cell stack operating parameters include pressure, temperature, supply of said hydrogen-rich stream and supply of said oxidant.

5. The method of claim 1 wherein said predetermined relationship between voltage and current is symbolized as a polarization curve and wherein different predetermined variance values are established along the curve.

6. The method of claim 1 further including terminating the supply of power to the external load when said predetermined variance value is exceeded.

7. The method of claim 1 further comprising the step of establishing the predetermined variance value as a percentage of the expected magnitude of the voltage.

8. The method of claim 7 further comprising the steps of:

establishing a positive variance value as a percentage of the predicted voltage wherein the sum of percentage and the predicted voltage magnitude are greater than the predicted voltage magnitude; and

establishing a negative variance value as a percentage of the predicted voltage magnitude wherein the sum of the percentage and the predicted voltage magnitude is less than the predicted voltage magnitude.

9. The method of claim 8 further comprising the step of:

generating separate output signals based on the predicted voltage magnitude exceeding the positive and the negative variance values.

10. In a method for operating a fuel cell system having a fuel processor which supplies a hydrogen-rich stream to a stack of fuel cells, wherein said hydrogen reacts with an oxidant to supply electrical power to an external load, the improvement comprising:

(a) establishing a predetermined relationship between voltage and current for a fuel cell stack;

(b) monitoring actual voltage and actual current from the fuel cell stack;

(c) then either;

(1) determining an expected value of voltage as a function of the actual current based on the predetermined relationship;

or

(2) determining an expected value of current as a function of the actual voltage based on the predetermined relationship;

(d) calculating the variance between said actual and expected values; and

(e) generating a signal if the calculated variance exceeds a predetermined variance value.