Efficiency optimized hybrid operation strategy

• US 20080133076A1
• Filed: 11/03/2006
• Published: 06/05/2008
• Est. Priority Date: 11/03/2006
• Status: Active Grant

• Current Assignee: GM Global Technology Operations LLC (General Motors Company)
• Original Assignee: GM Global Technology Operations Incorporated (Motors Liquidation Co. GUC Trust)
• Inventors: Kilian, Peter, Formanski, Volker
• Granted Patent: US 7,831,343 B2
• Time in Patent Office: Days
• US Class Current: 701/22
• CPC Class Codes: B60L 58/30 for monitoring or controlling fuel cells
• CPC Class Codes: B60W 10/26 for electrical energy, e.g. batteries or capacitors
• CPC Class Codes: B60W 10/28 including control of fuel cells
• CPC Class Codes: B60W 2510/244 Charge state
• CPC Class Codes: B60W 30/1843 Overheating of driveline components B60W30/186 takes precedence
• CPC Class Codes: H01M 16/006 of fuel cells with rechargeable batteries
• CPC Class Codes: H01M 2250/20 Fuel cells in motive systems, e.g. vehicle, ship, plane
• CPC Class Codes: H01M 8/04619 of fuel cell stacks
• CPC Class Codes: H01M 8/0494 of fuel cell stacks
• CPC Class Codes: H01M 8/04947 of auxiliary devices, e.g. batteries, capacitors
• CPC Class Codes: H02J 2300/30 The power source being a fuel cell
• CPC Class Codes: H02J 7/345 using capacitors as storage or buffering devices
• CPC Class Codes: Y02E 60/10 Energy storage using batteries
• 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
• CPC Class Codes: Y10S 903/903 having energy storing means, e.g. battery, capacitor
• CPC Class Codes: Y10S 903/905 Combustion engine

Abstract

A propulsion system for a fuel cell hybrid vehicle that includes a fuel cell system and an EESS, where the propulsion system employs an algorithm for increasing system efficiency. A power limit value is defined as the maximum system efficiency times the charge/discharge efficiency of the EESS. If the vehicle operator requests a power greater than the power limit value, then the fuel cell system will preferably provide the power, and if the power request from the vehicle operator is less than the power limit value, then the EESS will preferably provide the power. The algorithm also considers changing operation conditions and parameters that impact the fuel cell system efficiency and the electric energy storage system efficiency, such as the state of charge of the EESS and regenerative braking.

Claims

1. A propulsion system comprising:

a fuel cell system (FCS);

an electric energy storage system (EESS); and

an electric traction system (ETS) that is responsive to power from both the fuel cell system and the electric energy storage system, wherein the electric traction system preferably receives power from the fuel cell system if a power request from the electric traction system is above a determined power limit value and preferably receives power from the electric energy storage system if the power request from the electric traction system is below the determined power limit value.

2. The propulsion system according to claim 1 wherein the power limit value is determined by an efficiency curve of the fuel cell system, the maximum efficiency of the fuel cell system and the charge/discharge efficiency of the electric energy storage system.

3. The propulsion system according to claim 2 wherein the power limit value is defined by the location where the maximum efficiency of the fuel cell system times the charge/discharge efficiency of the electric energy storage system crosses the efficiency curve.

4. The propulsion system according to claim 1 wherein power from the fuel cell system is used to charge the electric energy storage system and provide the power request if the electric energy storage system state of charge falls to a predetermined minimum state of charge and the power request is below the power limit value.

5. The propulsion system according to claim 4 wherein power from the electric energy storage system is again used to provide the power request if the power request is still below the power limit value and the state of charge of the electric energy storage system reaches a predetermined maximum state of charge.

6. The propulsion system according to claim 4 wherein the power from the fuel cell system used to satisfy the power request and charge the electric energy storage system is provided at a power for maximum fuel cell system efficiency.

7. The propulsion system according to claim 4 wherein power from the fuel cell system does not fall below the power limit value.

8. The propulsion system according to claim 4 wherein the predetermined minimum state of charge of the electric energy storage system is greater than a true minimum state of charge of the electric energy storage system to keep a certain acceleration capability of the vehicle during any time of the operation of the propulsion system.

9. The propulsion system according to claim 5 wherein the predetermined maximum state of charge is less than a true maximum state of charge of the electric energy storage system so as to allow the electric energy storage system to capture regenerative braking power during any time of the operation of the propulsion system.

10. The propulsion system according to claim 1 wherein the fuel cell system and the electric energy storage system both provide power to the electric traction system if the power request is greater than a maximum power available from the fuel cell system.

11. The propulsion system according to claim 1 wherein the electric energy storage system is selected from the group consisting of a battery, an accumulator, a super-capacitor and combinations thereof.

12. The fuel cell propulsion system according to claim 1 wherein the propulsion system is part of a fuel cell hybrid vehicle.

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

a fuel cell system;

an electric energy storage system; and

an electric traction system that is responsive to power from both the fuel cell system and the electric energy storage system, wherein the electric energy storage system preferably receives power from the fuel cell system if a power request from the electric traction system is above a power limit value and preferably receives power from the electric energy storage system if the power request from the electric traction system is below the power limit value, said power limit value being determined by an efficiency curve of the fuel cell system, the maximum efficiency of the fuel cell system and the charge/discharge efficiency of the electric energy storage system, wherein the power limit value is defined by the location where the maximum efficiency of the fuel cell system times the charge/discharge efficiency of the electric energy storage system crosses the efficiency curve, and wherein power from the fuel cell system is used to charge the electric energy storage system and provide the power request if the electric energy storage system state of charge falls to a predetermined minimum state of charge and the power request is below the power limit value.

14. The propulsion system according to claim 13 wherein power from the electric energy storage system is again used to provide the power request if the power request is still below the power limit value and the state of charge of the electric energy storage system reaches a predetermined maximum state of charge.

15. The propulsion system according to claim 13 wherein the power from the fuel cell system used to satisfy the power request and charge the electric energy storage system is provided at a power for maximum fuel cell system efficiency.

16. The propulsion system according to claim 13 wherein power from the fuel cell system does not fall below the power limit value.

17. The propulsion system according to claim 13 wherein the predetermined minimum state of charge of the electric energy storage system is greater than a true minimum state of charge of the electric energy storage system to keep a certain acceleration capability of the vehicle during any time of the operation of the propulsion system.

18. The propulsion system according to claim 14 wherein the predetermined maximum state of charge is less than a true maximum state of charge of the electric energy storage system so as to allow the electric energy storage system to capture regenerative braking power during any time of the operation of the propulsion system.

19. The propulsion system according to claim 13 wherein the fuel cell system and the electric energy storage system both provide power to the electric traction system if the power request is greater than a maximum power available from the fuel cell system.

20. The propulsion system according to claim 13 wherein the electric energy storage system is selected from the group consisting of a battery, an accumulator, a super-capacitor and combinations thereof.

21. A method for providing power distribution between a fuel cell system and an electric energy storage system in a propulsion system, said method comprising:

defining a power limit value;

preferably using power from the fuel cell system if a power request from an electric traction system is above the power limit value; and

preferably using power from the electric energy storage system if the power request from the electric traction system is below the power limit value.

22. The method according to claim 21 wherein defining a power limit value includes using an efficiency curve of the fuel cell system, the maximum efficiency of the fuel cell system and the charge/discharge efficiency of the electric energy storage system.

23. The method according to claim 22 wherein defining a power limit value includes defining the location where the maximum efficiency of the fuel cell system times the charge/discharge efficiency of the electric energy storage system crosses the efficiency curve.

24. The method according to claim 21 wherein preferably using power from the fuel cell system and preferably using power from the electric energy storage system includes using power from the fuel cell system to charge the electric energy storage system and provide the power request if the electric energy storage system state of charge falls to a predetermined minimum state of charge and the power request is below the power limit value.

25. The method according to claim 24 wherein preferably using power from the fuel cell system and preferably using power from the electric energy storage system includes using the electric energy storage system to provide the power request if the power request is still below the power limit value and the state of charge of the electric energy storage system reaches a predetermined maximum state of charge.

26. The method according to claim 24 wherein preferably using power from the fuel cell system includes using the power from the fuel cell system to satisfy the power request and charge the electric energy storage system at a power for maximum fuel cell system efficiency.

27. The method according to claim 24 wherein preferably using power from the fuel cell system includes not allowing power from the fuel cell system to fall below the power limit value.

28. The method according to claim 24 wherein the predetermined minimum state of charge of the electric energy storage system is greater than a true minimum state of charge of the electric energy storage system to keep a certain acceleration capability of the vehicle during any time of the operation of the propulsion system.

29. The method according to claim 25 wherein the predetermined maximum state of charge is less than a true maximum state of charge of the electric energy storage system so as to allow the electric energy storage system to capture regenerative braking power during any time of the operation of the propulsion system.

30. The method according to claim 21 wherein preferably using power from the fuel cell system and preferably using power from the electric energy storage system includes using power from both the fuel cell system and the electric energy storage system if the power request is greater than a maximum power available from the fuel cell system.

31. The method according to claim 21 wherein the electric energy storage system is selected from the group consisting a battery, an accumulator, a super-capacitor and combinations thereof.