Fuel Cell Power Request Control Strategy

• US 20080176111A1
• Filed: 01/19/2007
• Published: 07/24/2008
• Est. Priority Date: 01/19/2007
• Status: Active Grant

• Current Assignee: GM Global Technology Operations LLC (General Motors Company)
• Original Assignee: GM Global Technology Operations Incorporated (General Motors Company)
• Inventors: Voigt, Andreas, Lenz, Jochen, Schaffnit, Jochen, Willimowski, Peter
• Granted Patent: US 8,642,222 B2
• Time in Patent Office: Days
• US Class Current: 429/13
• CPC Class Codes: H01M 2250/20 Fuel cells in motive systems, e.g. vehicle, ship, plane
• CPC Class Codes: H01M 8/04089 of gaseous reactants
• CPC Class Codes: H01M 8/04589 of fuel cell stacks
• CPC Class Codes: H01M 8/04753 of fuel cell reactants
• CPC Class Codes: H01M 8/0491 of fuel cell stacks
• 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: Y02E 60/50 Fuel cells
• CPC Class Codes: Y02T 90/40 Application of hydrogen technology to transportation, e.g. using fuel cells

Abstract

A power request controller that prevents a power request signal to a fuel cell stack controller from providing more compressor air and hydrogen gas than is necessary to meet the current power demands of the vehicle. The stack controller generates a signal of the available current from the fuel cell stack. This signal and the measured current actually being drawn from the stack are received by a proportional-integral (P-I) controller in the power request controller. If the available stack current is significantly greater than the stack current being used, the P-I controller will provide an output signal that reduces the power request signal to the stack controller so that the current produced by the stack and the current being drawn from the stack are substantially the same. A transient detector turns off the P-I controller so that it does not reduce the power request signal during an up-power transient.

Claims

1. A fuel cell system comprising:

a fuel cell stack responsive to a cathode air flow and an anode hydrogen gas flow;

a compressor for providing the cathode air flow to the fuel cell stack;

a fuel cell stack controller generating a hydrogen flow rate signal for providing a desired hydrogen flow rate to the fuel cell stack, a desired air flow signal indicative of the desired air flow to the cathode side of the fuel cell stack, an available stack current signal indicative of the current that is available from the fuel cell stack and an actual stack current signal indicative of the actual current being drawn from the stack;

a power request controller responsive to the actual stack current signal and the available stack current signal, and providing a power request reducing signal if the available stack current signal is greater than the actual stack current signal; and

an adder for adding the power request reducing signal and a raw stack power request signal to reduce the raw stack power request signal, said fuel cell stack controller being responsive to the reduced raw stack power request signal so that the actual stack current signal and the available stack current signal are about equal.

2. The system according to claim 1 further comprising a transient detector, said transient detector being responsive to the raw stack power request signal, said transient detector turning off the power request controller if the transient detector detects an up-power transient.

3. The system according to claim 2 wherein the transient detector turns off the power request controller if the raw stack power request signal changes more than 10% of a maximum stack power in one second or less.

4. The system according to claim 2 wherein the transient detector maintains the power request controller in the off condition for a time period of about three times a 10-90% step response of the fuel cell stack.

5. The system according to claim 1 wherein the power request controller only provides the power request reducing signal if the available stack current signal is greater than the actual stack current signal by a predetermined threshold.

6. The system according to claim 5 wherein the predetermined threshold is about 5 amps.

7. The system according to claim 1 wherein the power request controller is a proportional-integral controller.

8. The system according to claim 1 wherein the raw stack power request signal is a combination of an electric traction system power request signal, an auxiliary power request signal and a compressor power request signal.

9. The system according to claim 1 wherein the system is on a fuel cell vehicle.

10. A fuel cell system for a hybrid fuel cell vehicle, said system comprising:

a fuel cell stack responsive to a cathode air flow and an anode hydrogen gas flow;

a compressor for providing the cathode air flow to the fuel cell stack;

a first adder for adding an electric traction system power request signal from an electric traction system on the vehicle, an auxiliary power request signal from auxiliary power loads on the vehicle and a compressor power request signal that determines the speed of the compressor to provide a raw stack power request signal;

a fuel cell stack controller generating a hydrogen flow rate signal for providing a desired hydrogen flow rate to the fuel cell stack, a desired air flow signal that is used to generate the compressor power request signal, and available stack current signal indicative of the current that is available from the fuel cell stack and an actual stack current signal indicative of the actual current being drawn from the fuel cell stack;

a power request controller responsive to the actual stack current signal and the available stack current signal, and providing a power request reducing signal if the available stack current signal is greater than the actual stack current signal;

a second adder for adding the power request reducing signal and the raw stack power request signal to generate a stack power request signal that is sent to the fuel cell stack controller so that the actual stack current signal and the available stack current signal are about equal; and

a transient detector, said transient detector being responsive to the raw stack power request signal, said transient detector turning off the power request controller if the transient detector detects an up-power transient.

11. The system according to claim 10 wherein the transient detector turns off the power request controller if the raw stack power request signal changes more than 10% of a maximum stack power in one second or less.

12. The system according to claim 10 wherein the transient detector maintains the power request controller in the off condition for a time period of about three times a 10-90% step response of the fuel cell stack.

13. The system according to claim 10 wherein the power request controller only provides the reducing power request reducing signal if the available stack current signal is greater than the actual stack current signal by a predetermined threshold.

14. The system according to claim 13 wherein the predetermined threshold is about 5 amps.

15. The system according to claim 10 wherein the power request controller is a proportional-integral controller.

16. A method for preventing the current available from a fuel cell stack from exceeding the current actually being drawn from the fuel cell stack, said method comprising:

determining the amount of current that the fuel cell stack can generate;

determining the amount of current that is being drawn from the fuel cell stack; and

reducing the amount of current that is available from the fuel cell stack if the amount of the amount of current available from the fuel cell stack exceeds the current being drawn from the fuel cell stack.

17. The method according to claim 16 wherein reducing the amount of current that is available from the fuel cell stack includes reducing a raw stack power request signal that is a combination of an electric traction system power request signal, an auxiliary power request signal and a compressor power request signal.

18. The method according to claim 16 further comprising preventing the power request signal from being reduced if the fuel cell stack is in an up-power transient.

19. The method according to claim 18 wherein preventing the power request signal from being reduced if the fuel cell stack is in an up-power transient includes preventing the power request signal from being reduced if a raw stack power request signal changes more than 10% of a maximum stack power in one second or less.

20. The method according to claim 18 wherein preventing the power request signal from being reduced if the fuel cell stack is in an up-power transient includes preventing the power request signal from being reduced for a time period of about three times a 10-90% step response of the fuel cell stack.