Method to control maximum current for a fuel cell

Patent metadata

Field	Value
Publication number	US-11309557-B2
Application number	US-201916730140-A
Country	US
Kind code	B2
Filing date	Dec 30, 2019
Priority date	Sep 29, 2015
Publication date	Apr 19, 2022
Grant date	Apr 19, 2022

Abstract

The disclosure relates to a fuel cell stack and corresponding method of operating the fuel cell stack. The method comprises: determining a maximum allowable current that may be drawn from the fuel cell stack; repeatedly determining a magnitude of change to the prevailing maximum allowable current based on a prevailing allowable current ramp rate and an actual measured current of the fuel cell stack; updating the maximum allowable current according to the periodically determined magnitude of change; and controlling operating parameters of the fuel cell stack according to the prevailing maximum allowable current.

First claim

The invention claimed is:

1. A method of operating a fuel cell system comprising:
repeatedly determining a maximum allowable current that may be drawn from the fuel cell system based on at least one of a prevailing allowable current ramp rate, an actual measured current of the fuel cell system, and a parasitic current load of the fuel cell system; and
controlling a plurality of operating parameters of the fuel cell system according to a most recent determination of the maximum allowable current as a function of one or more of:
(i) a total system running time;
(ii) a count of the total number of full stop-start cycles to which the fuel cell system has been subjected;
(iii) an ambient humidity falling below a predetermined low humidity threshold;
(iv) an ambient temperature falling below a predetermined low temperature threshold;
(v) an ambient temperature rising above a predetermined high temperature threshold;
(vi) a system voltage;
(vii) the proximity of one or more cell voltages to a minimum cell voltage threshold and/or the proximity of a system temperature to a maximum temperature limit and,
(viii) the maximum allowable current does not fall below a predetermined minimum current limit.

2. The method of claim 1 in which the step of controlling operating parameters of the fuel cell system comprises controlling an electrical load on the fuel cell system.

3. The method of claim 1 in which the most recent determination of the maximum allowable current comprises an increment or a decrement with respect to a less recent determination of the maximum allowable current.

4. The method of claim 1 in which the most recent determination of the maximum allowable current is determined according to the smaller of a magnitude of change corresponding to the prevailing allowable current ramp rate and a magnitude of change indicated by a current load requirement.

5. The method of claim 1 in which the most recent determination of the maximum allowable current is determined as a function of a period of time corresponding to a drying time of one or more fuel cells of the fuel cell system.

6. The method of claim 1 further including the step of periodically determining an allowable current ramp rate as a function of an actual measured current and a presently prevailing current ramp rate and at least one of: a rated maximum current for the system; a maximum ramp rate based on the capability of the fuel and/or oxidant delivery system; a period of time corresponding to a drying time of one or more fuel cells of the fuel cell system; and a period of time corresponding to a wetting time of the one or more fuel cells of the fuel cell system.

7. The method of claim 6 in which the rated maximum current comprises a predetermined maximum current for the physical configuration of the fuel cell system.

8. The method of claim 1 further including the step of inhibiting an increase in the maximum allowable current in the event of one or more of:
(i) a temperature of one or more cells exceeding a predetermined temperature threshold;
(ii) one or more cell voltages falling below a predetermined cell voltage threshold;
(iii) plural cell voltages exceeding a predetermined range.

9. The method of claim 1 further including the step of overriding the maximum allowable current in the event of one or more of:
(i) the system entering a shutdown procedure;
(ii) one or more fuel cells of the system being isolated from a load.

10. A fuel cell system comprising:
one or more fuel cells disposed in series or in parallel; and
a controller conformed to perform the method of claim 1 ; and,
in which the one or more fuel cells are air cooled fuel cells.

11. A vehicle comprising the fuel cell system of claim 10 for powering said vehicle.

Assignees

• Intelligent Energy Ltd

Inventors

• Bowman Jeremy

Classifications

• Y02T90/40

  Application of hydrogen technology to transportation, e.g. using fuel cells · CPC title

• H01M8/04302 Primary

  applied during start-up · CPC title

• H01M8/04574

  Current · CPC title

• H01M8/04589

  of fuel cell stacks · CPC title

• H01M8/04925

  Power, energy, capacity or load · CPC title