Regulating the maximum output current of a fuel cell stack
First Claim
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1. A method comprising:
- establishing a fuel flow through a fuel cell stack to produce a current;
scanning cell voltages of the fuel cell stack to determine the lowest minimum voltage of the cell voltages; and
setting a maximum limit on the current based at least in part on the lowest voltage.
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Abstract
A method includes establishing a fuel flow through a fuel cell stack to produce a current. The voltages of the fuel cell stack are scanned to determine the minimum cell voltage. A maximum limit on the current is set based at least in part on the minimum cell voltage.
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Citations
26 Claims
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1. A method comprising:
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establishing a fuel flow through a fuel cell stack to produce a current;
scanning cell voltages of the fuel cell stack to determine the lowest minimum voltage of the cell voltages; and
setting a maximum limit on the current based at least in part on the lowest voltage. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14)
regulating the fuel flow based on the output power, wherein the regulation has a transient response and the setting the maximum limit prevents the fuel cell stack from receiving an insufficient fuel flow due to the transient response.
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3. The method of claim 1, wherein the scanning comprises:
continually monitoring the cell voltages during the regulation to dynamically determine the lowest voltage.
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4. The method of claim 1, wherein the lowest voltage may be associated with different fuel cells of the fuel system over time.
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5. The method of claim 1, wherein the setting the maximum limit prevents the cell voltages from decreasing below a minimum threshold voltage.
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6. The method of claim 1, wherein the setting the maximum limit prevents the minimum cell voltage from decreasing below a minimum threshold voltage.
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7. The method of claim 1, further comprising:
using a DC-to-DC voltage converter to receive an output voltage from the fuel cell stack and provide a predetermined voltage level at an output terminal of the converter.
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8. The method of claim 7, wherein the setting the maximum current limit comprises:
establishing a maximum output current of the DC-to-DC voltage converter.
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9. The method of claim 1, further comprising:
providing a battery to supplement the fuel cell stack to provide additional current beyond the maximum limit.
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10. The method of claim 1, wherein the setting the maximum limit comprises:
increasing the maximum limit when the lowest voltage increases.
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11. The method of claim 1, wherein the setting the maximum limit comprises:
decreasing the maximum limit when the lowest voltage decreases.
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12. The method of claim 1, wherein the setting the maximum limit comprises:
increasing the maximum limit when the fuel flow increases.
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13. The method of claim 1, wherein the setting the maximum limit comprises:
decreasing the maximum limit when the fuel flow decreases.
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14. The method of claim 1, further comprising measuring a hydrogen concentration in an anode exhaust flow and adjusting the maximum current limit based on the measured hydrogen concentration.
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15. A fuel cell system comprising:
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a fuel cell stack adapted to produce a current in response to a fuel flow; and
a circuit coupled to the fuel cell stack and adapted to;
determine cell voltages of the fuel cell stack, select the lowest voltage of the cell voltages, and set a maximum limit on the current based on at least in part the lowest voltage. - View Dependent Claims (16, 17, 18, 19, 20, 21, 22, 23, 24, 25, 26)
a reformer to furnish the fuel flow, the reformer having a transient response, wherein the circuit sets the maximum limit to prevent the fuel cell stack from receiving an insufficient fuel flow due to the transient response.
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17. The fuel cell system of claim 15, wherein the circuit comprises:
a voltage monitoring circuit adapted to continually monitor the cell voltages during the regulation to dynamically determine the lowest voltage.
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18. The fuel cell system of claim 15, wherein the lowest voltage may be associated with different fuel cells of the fuel system over time.
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19. The fuel cell system of claim 15, further comprising:
a DC-to-DC voltage regulator coupled to the fuel cell stack to furnish output power in response to power received from the stack.
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20. The fuel cell system of claim 15, wherein the circuit prevents the cell voltages from decreasing below a minimum threshold voltage.
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21. The fuel cell system of claim 15, wherein the circuit prevents the lowest voltage from decreasing below a minimum threshold voltage.
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22. The fuel cell system of claim 15, wherein the circuit is adapted to increase the maximum limit when the lowest voltage increases.
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23. The fuel cell system of claim 15, wherein the circuit is adapted to decrease the maximum limit when the fuel flow decreases.
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24. The fuel cell system of claim 15, wherein the circuit is adapted to increase the maximum limit when the fuel flow increases.
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25. The fuel cell system of claim 15, wherein the circuit is adapted to decrease the maximum limit when the fuel flow decreases.
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26. The fuel cell system of claim 15, further comprising:
- a sensor adapted to measure a hydrogen concentration in an anode exhaust flow; and
the circuit being further adapted to adjust the maximum current limit based on the measured hydrogen concentration.
- a sensor adapted to measure a hydrogen concentration in an anode exhaust flow; and
Specification