METHOD FOR CONTROLLING OUTPUT OF FUEL CELL IN FUEL CELL HYBRID VEHICLE

• US 20090325004A1
• Filed: 12/15/2008
• Published: 12/31/2009
• Est. Priority Date: 06/27/2008
• Status: Active Grant

• Current Assignee: Hyundai Motor Company (Hyundai Motor Group)
• Original Assignee: Hyundai Motor Company (Hyundai Motor Group)
• Inventors: Kwon, Sang Uk, Lee, Nam Woo, Park, Sun Soon, Choi, Seo Ho, Jeon, Soon Il, Ryu, Seong Pil
• Granted Patent: US 8,486,571 B2
• Time in Patent Office: Days
• US Class Current: 429/431
• CPC Class Codes: H01M 16/006 of fuel cells with rechargeable batteries
• CPC Class Codes: H01M 8/04626 of auxiliary devices, e.g. batteries, capacitors
• CPC Class Codes: H01M 8/04925 Power, energy, capacity or load
• CPC Class Codes: Y02E 60/10 Energy storage using batteries
• CPC Class Codes: Y02E 60/50 Fuel cells

Abstract

The present invention provides a method for controlling output of a fuel cell to improve fuel efficiency of a fuel cell hybrid vehicle, in which the fuel cell is operated at a constant power at a maximum efficiency point, wherein the fuel cell and a storage means are directly connected if the output and energy of the storage means is insufficient, and the power generation of the fuel cell is stopped when the level of energy of the storage means is increased during stopping or during low power operation such that the fuel cell is intensively operated at the maximum efficiency point, thus improving the fuel efficiency of the fuel cell and the efficiency of the fuel cell system.

Claims

1. A method for controlling output of a fuel cell in a fuel cell hybrid vehicle including a fuel cell as a main power source and a storage means as an auxiliary power source, the vehicle comprising a power converter disposed between the fuel cell and the storage means and provided for a constant current operation of the fuel cell and a directly connected switch for directly connecting/disconnecting between the fuel cell and the storage means, the method comprising controlling the output of the fuel cell according to the amount of electrical energy of the storage means by a mode selected from the group consisting of a fuel cell stop mode in which power generation of the fuel cell is stopped, a fuel cell constant current mode in which the power converter is operated so that the fuel cell is operated at a constant power at a maximum efficiency point, and a fuel cell-storage means direct connection mode in which the fuel cell and the storage means are directly connected by the directly connected switch and then the output of the fuel cell is controlled according to a load required by the vehicle.

2. The method of claim 1, wherein, if the amount of electrical energy of the storage means is below a reference value for restarting the power generation of the fuel cell and if the elapsed time after the fuel cell stop exceeds a predetermined minimum retention time in the fuel cell stop mode, the fuel cell stop mode is switched to the fuel cell constant current mode in a state where the directly connected switch is turned off.

3. The method of claim 1, wherein, in the fuel cell constant current mode, fuel cell balance-of-plant components are controlled to be operated at a constant power in a state where the power converter is controlled to apply a voltage corresponding to the maximum efficiency point to an output side of the fuel cell such that the fuel cell is operated at a constant power in which an output current of the fuel cell is maintained at a constant level.

4. The method of claim 3, wherein the power converter is a buck-boost converter, and a converter controller controls the operation of the buck-boost converter to apply a voltage corresponding to the maximum efficiency point by sensing a voltage of an output terminal of the buck-boost converter through a voltage sensor.

5. The method of claim 1, wherein, if the amount of electrical energy of the storage means is below a reference value for starting the fuel cell-storage means direct connection mode in the fuel cell constant current mode, the fuel cell and the storage means are directly connected by the directly connected switch and the operation of the power converter is stopped such that the fuel cell constant current mode is switched to the fuel cell-storage means direct connection mode.

6. The method of claim 5, wherein air is supercharged to a fuel cell stack for a predetermined period of time before the fuel cell and the storage means are directly connected by the directly connected switch.

7. The method of claim 1, wherein the amount of electrical energy of the storage means is a storage means voltage measured by a voltage sensor of a main bus terminal.

8. The method of claim 1, further comprising:

determining whether regenerative braking is performed;

determining whether to enter the fuel cell stop mode by comparing the amount of electrical energy of the storage means with reference values predetermined according to whether the regenerative braking is performed; and

stopping the power generation of the fuel cell if the amount of electrical energy of the storage means is greater than the corresponding reference value.

9. The method of claim 8, wherein the reference value during regenerative braking is set to be lower than the reference value in the case where the regenerative braking is not performed so that the fuel cell stop mode is performed in a state where the amount of electrical energy of the storage means is lower than that in the case where the regenerative braking is not performed.

10. The method of claim 8, further comprising:

switching the fuel cell-storage means direct connection mode to the fuel cell constant current mode, if the amount of electrical energy of the storage means is above a predetermined level in the fuel cell-storage means direct connection mode in a state where the directly connected switch is turned on;

determining whether the regenerative braking is performed in the fuel cell constant current mode;

determining whether to enter the fuel cell stop mode; and

stopping the power generation of the fuel cell.

11. A method for controlling output of a fuel cell in a fuel cell hybrid vehicle including a fuel cell as a main power source and a storage means as an auxiliary power source, the method comprising:

controlling the output of the fuel cell according to the amount of electrical energy of the storage means by a mode selected from the group consisting of a fuel cell stop mode, a fuel cell constant current mode, and a fuel cell-storage means direct connection mode and then the output of the fuel cell is controlled.

12. The method of claim 11, wherein the vehicle comprises a power converter disposed between the fuel cell and the storage means and provides for a constant current operation of the fuel cell and a directly connected switch for directly connecting/disconnecting between the fuel cell and the storage means.

13. The method of claim 11, wherein in the fuel cell stop mode power generation of the fuel cell is stopped.

14. The method of claim 11, wherein in the constant current mode the power converter is operated so that the fuel cell is operated at a constant power at a maximum efficiency point.

15. The method of claim 11, wherein in the fuel cell-storage means direct connection mode the fuel cell and the storage means are directly connected by a directly connected switch.

16. The method of claim 11, wherein the output of the fuel cell is further controlled according to a load required by the vehicle.

17. The method of claim 11, wherein, if the amount of electrical energy of the storage means is below a reference value for restarting the power generation of the fuel cell and if the elapsed time after the fuel cell stop exceeds a predetermined minimum retention time in the fuel cell stop mode, the fuel cell stop mode is switched to the fuel cell constant current mode in a state where the directly connected switch is turned off.