System stack contingency and efficiency switching

• US 7,247,398 B2
• Filed: 04/14/2003
• Issued: 07/24/2007
• Est. Priority Date: 04/14/2003
• Status: Active Grant

• Current Assignee: GM Global Technology Operations LLC (General Motors Company)
• Original Assignee: General Motors Corporation (Motors Liquidation Co. GUC Trust)
• Inventors: Logan, Victor W, Dandalides, James W
• Primary Examiner(s): YUAN, DAH WEI D
• Application Number:
  US10/413,272
• Publication Number:
  US 20040202901A1
• Time in Patent Office: 1,562 Days
• Field of Search: 429/13, 429/22, 429/34
• US Class Current: 429/431
• CPC Class Codes: H01M 8/04246 Short circuiting means for defective fuel cells detection of defective fuel cells H01M8/04664, methods for shunting fuel cells H01M8/04955
• 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 8/04902 of the individual fuel cell
• CPC Class Codes: H01M 8/04932 of the individual fuel cell
• CPC Class Codes: H01M 8/249 comprising two or more groupings of fuel cells, e.g. modular assemblies
• CPC Class Codes: Y02E 60/50 Fuel cells

Abstract

A switching system and control method therefor are provided and implemented with a fuel cell stack system. The switching system enables fuel cell stacks to be connected in series for providing power to a power user while removing the particular disadvantages of a series circuit. In the event of a stack fault, the faulty stack may be bypassed, whereby the remaining stacks provide power to the power user at reduced capacity. The stack is continuously monitored and is reintroduced to the series circuit if the fault clears. If the fault reoccurs a predetermined number of times after the stack has been reintroduced, a “reduced capacity” mode is initiated. Additionally, in the event of a reduced or an increased current demand, stacks are selectively switched in and out of the series connection, for limiting the overall operation voltage range of the fuel cell stack system.

Claims

1. A method of operating a fuel cell stack system comprising:

monitoring a plurality of fuel cell stacks for a fault condition and a condition of current demand on said plurality of fuel cell stacks;

bypassing at least one fuel cell stack of said plurality of fuel cell stacks if said fault condition is detected;

counting a number of times a particular fuel cell stack recurrently achieves said fault condition; and

initiating a reduced capacity mode if said number of times is equal to a predetermined value; and

bypassing at least one fuel cell stack of said plurality of fuel cell stacks if said current demand condition is detected, wherein said current demand condition is one of a reduced current demand condition relative to a prior current demand condition.

2. The method of claim 1, further comprising reconnecting said at least one fuel cell stack if said current demand condition is one of an increased current demand condition relative to a prior current demand condition.

3. The method of claim 2, further comprising:

determining a number of fuel cell stacks to reconnect, as a function of said increased current demand condition; and

selecting one or more fuel cell stacks to reconnect.

4. The method of claim 3, wherein selecting said one or more fuel cell stacks comprises determining an average operating time for said plurality of fuel cell stacks, and selecting said one or more fuel cell stacks having an operating time below said average operating time.

5. The method of claim 2, wherein said step of reconnecting said at least one fuel cell stack comprises:

operating a switch to enable a current flow through said at least one fuel cell stack; and

redirecting said current flow back through said at least one fuel cell stack.

6. The method of claim 2, further comprising:

monitoring an external load and adjusting a number of fuel cell stacks powering the external load as the external load varies.

7. The method of claim 1, further comprising:

determining a number of fuel cell stacks to bypass, as a function of said reduced current demand condition; and

selecting one or more fuel cell stacks to bypass.

8. The method of claim 7, wherein selecting said one or more fuel cell stacks comprises determining an average operating time for said plurality of fuel cell stacks, and selecting said one or more fuel cell stacks having an operating time above said average operating time.

9. The method of claim 1, wherein said step of bypassing at least one fuel cell stack of the plurality of fuel cell stacks comprises:

operating a switch to prohibit a current flow through said at least one fuel cell stack; and

redirecting said current flow through remaining fuel cell stacks in the fuel cell stacks system.

10. The method of claim 1, further comprising:

varying the system voltage by adjusting a number of fuel cellstacks powering an external load.

11. A method of operating a fuel cell stack system comprising:

monitoring a plurality of fuel cell stacks for a fault condition;

bypassing at least one fuel cell stack of said plurality of fuel cell stacks if said fault condition is detected;

counting a number of times a particular fuel cell stack recurrently achieves said fault condition; and

initiating a reduced capacity mode if said number of times is equal to a predetermined value.

12. The method of claim 11 further comprising:

reconnecting said at least one fuel cell stack if said fault condition clears;

bypassing at least one fuel cell stack of said plurality of fuel cell stacks if a reduced current demand condition relative to a prior current demand condition is detected; and

reconnecting said at least one fuel cell stack if an increased current demand condition relative to a prior current demand condition is detected.

13. The method of claim 12, further comprising:

determining a number of fuel cell stacks to bypass, as a function of said reduced current demand condition; and

selecting one or more fuel cell stacks to bypass.

14. The method of claim 13, wherein selecting said one or more fuel cell stack comprises determining an average operating time for said plurality of fuel cell stacks, and selecting said one or more fuel cell stacks having an operating time above said average operating time.

15. The method of claim 12, further comprising:

determining a number of fuel cell stacks to reconnect, as a function of said increased current demand condition; and

selecting one or more fuel cell stacks to reconnect.

16. The method of claim 15, wherein selecting said one or more fuel cell stacks comprises determining an average operating time for said plurality of fuel cell stacks, and selecting said one or more fuel cell stacks having an operating time below said average operating time.

17. The method of claim 12, wherein said reconnecting said at least one fuel cell stack comprises:

operating a switch to enable a current flow through said at least one fuel cell stack; and

redirecting said current flow back through said at least one fuel cell stack.

18. The method of claim 11, wherein bypassing at least one fuel cell stack of the plurality of fuel cell stacks comprises:

operating a switch to prohibit a current flow through said at least one fuel cell stack; and

redirecting said current flow through remaining fuel cell stacks in the fuel cell stacks system.