Fuel cell system automatic power switching method and apparatus

• US 6,979,504 B2
• Filed: 07/25/2001
• Issued: 12/27/2005
• Est. Priority Date: 07/25/2001
• Status: Expired due to Term

• Current Assignee: Ballard Power Systems Corporation (Siemens AG)
• Original Assignee: Ballard Power Systems Corporation (Siemens AG)
• Inventors: Manery, David S.
• Primary Examiner(s): Crepeau, Jonathan
• Application Number:
  US09/916,239
• Publication Number:
  US 20030022031A1
• Time in Patent Office: 1,616 Days
• Field of Search: 429/9, 429/13, 429/22, 429/23, 320/101
• US Class Current: 429/432
• CPC Class Codes: H01M 16/006 of fuel cells with rechargeable batteries
• CPC Class Codes: H01M 8/0267 having heating or cooling means, e.g. heaters or coolant flow channels
• CPC Class Codes: H01M 8/04014 Heat exchange using gaseous fluids; Heat exchange by combustion of reactants
• CPC Class Codes: H01M 8/04089 of gaseous reactants
• CPC Class Codes: H01M 8/04141 by water containing exhaust gases
• CPC Class Codes: H01M 8/04164 by condensers, gas-liquid separators or filters
• CPC Class Codes: H01M 8/04208 Cartridges, cryogenic media or cryogenic reservoirs
• CPC Class Codes: H01M 8/04225 during start-up
• CPC Class Codes: H01M 8/04228 during shut-down
• CPC Class Codes: H01M 8/04231 Purging of the reactants
• CPC Class Codes: H01M 8/043 applied during specific periods
• CPC Class Codes: H01M 8/04302 applied during start-up
• CPC Class Codes: H01M 8/04303 applied during shut-down
• CPC Class Codes: H01M 8/04388 of anode reactants at the inlet or inside the fuel cell
• CPC Class Codes: H01M 8/04447 of anode reactants at the inlet or inside the fuel cell
• CPC Class Codes: H01M 8/04552 of the individual fuel cell
• 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 8/04753 of fuel cell reactants
• CPC Class Codes: H01M 8/04955 Shut-off or shut-down of fuel cells
• CPC Class Codes: H01M 8/065 : by dissolution of metals or alloys; by dehydriding metallic substances
• CPC Class Codes: H01M 8/2457 : with both reactants being gaseous or vaporised
• CPC Class Codes: Y02E 60/10 : Energy storage using batteries
• CPC Class Codes: Y02E 60/50 : Fuel cells

Abstract

A fuel cell system includes a fuel cell stack, a battery, and a control system. A power circuit couples the fuel cell system selectively between the fuel cell stack and the battery. The power circuit includes a battery supply switch responsive to a voltage across the fuel cell stack, and a stack supply switch responsive to an operating state of the fuel cell system. The battery supply switch uncouples the battery from an on-board power supply when a voltage across the fuel cell stack exceeds a first threshold voltage and couples the battery to the on-board power supply when the fuel cell stack voltage is less than a second threshold voltage. The stack supply switch couples power the fuel cell stack to the on-board power supply when in a running state. A diode-OR circuit couples the source with the highest potential to the on-board power supply.

Claims

1. A fuel cell system, comprising:

a fuel cell stack;

a battery; and

a fuel cell control system, including a power supply switch responsive to a voltage across the fuel cell stack to couple power from the fuel cell stack to the fuel cell control system at a first time while the voltage across the fuel cell stack is above a fuel cell stack threshold voltage and to couple power from the battery to the fuel cell control system at a second time while the voltage across the fuel cell stack is below the fuel cell stack threshold voltage.

2. The fuel cell system of claim 1 wherein the battery is rechargeable and the fuel cell stack is selectively couplable to provide power to recharge the battery.

3. The fuel cell system of claim 1 wherein the power supply switch is further responsive to an operating state of the fuel cell system.

4. A fuel cell system, comprising:

a fuel cell stack;

a battery; and

a fuel cell control system, including a power supply switch responsive to a voltage across the fuel cell stack to couple power from the fuel cell stack to the fuel cell control system at a first time when the voltage across the fuel cell stack rises above a first fuel cell stack threshold voltage and to couple power from the battery to the fuel cell control system at a second time when the voltage across the fuel cell stack falls below a second fuel cell stack threshold voltage.

5. The fuel cell system of claim 4, further including a second power supply switch responsive to an operating state of the fuel cell system.

6. A fuel cell control system for controlling operation of a fuel cell system having a fuel cell stack, the fuel cell control system comprising:

a microcontroller;

at least one sensor positioned to measure an operating parameter of the fuel cell system and coupled to provide signals to the microcontroller corresponding to the measured operating parameter;

at least one actuator coupled to receive signals from the microcontroller in response to the measured operating parameter; and

a power switching circuit configured to selectively couple power from the fuel cell stack to the microcontroller at a first time, and to selectively couple power from a battery to the microcontroller at a second time wherein the power switching circuit comprises a voltage responsive switching circuit having an output coupled to the microcontroller, a stack supply switch responsive to an operating state of the fuel cell system to provide an electrical path between the fuel cell stack and the voltage responsive switching circuit and a battery supply switch responsive to a voltage across the fuel cell stack to provide an electrical path between the battery and the voltage responsive switching circuit.

7. The fuel cell control system of claim 6 wherein the battery supply switch is responsive to the voltage across the fuel cell stack in a number of the operating states of the fuel cell system.

8. A fuel cell control system for controlling operation of a fuel cell system having a fuel cell stack, the fuel cell control system comprising:

a microcontroller;

at least one sensor positioned to measure an operating parameter of the fuel cell system and coupled to provide signals to the microcontroller corresponding to the measured operating parameter;

at least one actuator coupled to receive signals from the microcontroller in response to the measured operating parameter; and

a power switching circuit configured to selectively couple power from the fuel cell stack to the microcontroller at a first time, and to selectively couple power from a battery to the microcontroller at a second time wherein the power switching circuit comprises a diode-OR circuit, a stack supply switch responsive to an operating state of the fuel cell system to provide an electrical path between the fuel cell stack and the diode-OR circuit and a battery supply switch responsive to a voltage across the fuel cell stack to provide an electrical path between the battery and the diode-OR circuit.

9. A fuel cell control system for controlling operation of a fuel cell system having a fuel cell stack, the fuel cell control system comprising:

a microcontroller;

at least one sensor positioned to measure an operating parameter of the fuel cell system and coupled to provide signals to the microcontroller corresponding to the measured operating parameter;

at least one actuator coupled to receive signals from the microcontroller in response to the measured operating parameter; and

a power supply switch configured to selectively switch power from the fuel cell stack to at least one of the microcontroller, the sensor and the actuator when a voltage across the fuel cell stack is above a first fuel cell stack threshold voltage and to selectively switch power from a battery to at least one of the microcontroller, the sensor and the actuator when the voltage across the fuel cell stack is below a second fuel cell stack threshold voltage, the second fuel cell stack threshold voltage different than the first fuel cell stack threshold voltage.

10. The fuel cell control system of claim 9 wherein the second fuel cell stack threshold voltage is less than the first fuel cell stack threshold voltage.

11. The fuel cell control system of claim 9 wherein the power supply switch comprises:

a diode-OR circuit having a first input, a second input, and an output, the first input couplable to the fuel cell stack, the output coupled to at least one of the microcontroller, the sensor and the actuator;

a battery supply transistor coupled between the battery and the second input of the diode-OR circuit.

12. A fuel cell control system for controlling operation of a fuel cell system having a fuel cell stack, the fuel cell control system comprising:

a microcontroller;

at least one sensor positioned to measure an operating parameter of the fuel cell system and coupled to provide signals to the microcontroller corresponding to the measured operating parameter;

at least one actuator coupled to receive signals from the microcontroller in response to the measured operating parameter; and

a power supply switch configured to selectively switch power from the fuel cell stack to the microcontroller in a first operating state when a voltage across the fuel cell stack is above a first fuel cell stack threshold voltage and to selectively switch power from a battery to the microcontroller in the first operating state when the voltage across the fuel cell stack is below a second fuel cell stack voltage.

13. The fuel cell control system of claim 12 wherein the power supply switch comprises:

a diode-OR circuit having a first input, a second input, and an output, the output coupled to at least one of the microcontroller, the sensor and the actuator;

a battery supply transistor coupled between the battery and the first input of the diode-OR circuit; and

a fuel cell stack transistor coupled between the fuel cell stack and the second input of the diode-OR circuit.

14. A controller-readable media carrying instructions for causing a controller to control operation of a fuel cell system having a fuel cell stack and a battery, by:

coupling power from the fuel cell stack to the controller when a voltage across the fuel cell stack moves above a first threshold voltage; and

coupling power from the battery to the controller when the voltage across the fuel cell stack drops below a second threshold voltage wherein the second threshold voltage is lower than the first threshold voltage.

15. A method of operating a fuel cell system, the method comprising:

providing power from a fuel cell stack to a fuel cell control system at a first time, wherein the first time corresponds to a time when a voltage across the fuel cell stack is above a first threshold voltage; and

providing power from a battery to the fuel cell control system at a second time, wherein the second time corresponds to a time when the voltage across the fuel cell stack is below a second threshold voltage, different from the first threshold voltage.

16. The method of claim 15 wherein the first time corresponds to a time when the fuel cell system is in a first operating state and the second time corresponds to a time when the fuel cell system is in a second operating state.

17. The method of claim 15 wherein the first time corresponds to a time when the fuel cell system is in a first operating state and a voltage across the fuel cell stack is above a first threshold voltage, and the second time corresponds to a time when the fuel cell system is in the first operating state and the voltage across the fuel cell stack is below a second threshold voltage.

18. A method of operating a power switching circuit in a fuel cell system to couple power to an on-board power supply selectively from a fuel cell stack and a battery, the method comprising:

changing a state of a stack supply switch to couple the fuel cell stack to the on-board power supply when entering a running operational state of the fuel cell system from a starting operational state of the fuel cell system;

setting a state of a battery supply switch to uncouple the battery from the on-board power supply if a voltage across the fuel cell stack is above an upper fuel cell stack threshold voltage;

setting the state of the battery supply switch to couple power from the battery to the on-board power supply if the voltage across the fuel cell stack falls below a lower fuel cell stack threshold voltage; and

changing the state of the battery supply switch to couple the battery to the on-board power supply when entering a stopping operational state of the fuel cell system from the running operational state.

19. The method of claim 18 wherein changing a state of the stack supply switch includes coupling a signal from the controller to a switching input terminal of the stack supply switch.

20. The method of claim 18 wherein the battery supply switch is a transistor and setting a state of the battery supply switch includes coupling a signal from a comparison circuit to a switching input terminal of the transistor.

21. The method of claim 18, further comprising:

coupling the battery supply switch to a first input of a diode-OR circuit; and

coupling the stack supply switch to a second input of the diode-OR circuit.

22. The method of claim 18, further comprising:

determining that the voltage across the fuel cell stack exceeds a third threshold voltage before entering a running state.