Fuel cell system ride-through of electric grid disturbances

• US 10,243,226 B2
• Filed: 09/09/2015
• Issued: 03/26/2019
• Est. Priority Date: 09/09/2015
• Status: Active Grant

• Current Assignee: Fuelcell Energy Ltd.
• Original Assignee: Fuelcell Energy Ltd.
• Inventors: Berntsen, George, Pasquale, Nicholas
• Primary Examiner(s): Crepeau, Jonathan
• Assistant Examiner(s): Martin, Angela J
• Application Number:
  US14/849,274
• Publication Number:
  US 20170070088A1
• Time in Patent Office: 1,294 Days
• Field of Search: None
• CPC Class Codes: H01M 2250/10 Fuel cells in stationary systems, e.g. emergency power source in plant
• CPC Class Codes: H01M 8/04225 during start-up
• CPC Class Codes: H01M 8/04302 applied during start-up
• CPC Class Codes: H01M 8/0432 Temperature; Ambient temperature
• CPC Class Codes: H01M 8/04925 Power, energy, capacity or load
• CPC Class Codes: H02J 1/00 Circuit arrangements for dc mains or dc distribution networks
• CPC Class Codes: H02J 2300/30 The power source being a fuel cell
• CPC Class Codes: H02J 3/381 Dispersed generators
• CPC Class Codes: H02J 9/062 for AC powered loads
• CPC Class Codes: Y02B 90/10 Applications of fuel cells in buildings
• CPC Class Codes: Y02E 60/50 Fuel cells

Abstract

A fuel cell system includes a fuel cell assembly configured to generate a direct current (DC) signal. The fuel cell system also includes one or more inverters coupled to the fuel cell assembly by way of one or more first bus lines. The fuel cell system also includes a variable frequency drive (VFD) coupled to an output of the one or more inverters and configured to receive AC power from the one or more inverters. The VFD is configured to convert the AC power to DC power and to provide the DC power to at least one auxiliary component during a normal operating condition. The fuel cell system further includes one or more second bus lines configured to receive the DC signal via the one or more first bus lines and to provide the DC signal to the VFD to power the at least one auxiliary component during a low voltage ride through condition.

Claims

1. A fuel cell system comprising:

a fuel cell assembly configured to generate a direct current (DC) signal;

one or more inverters coupled to the fuel cell assembly by way of one or more first bus lines;

a variable frequency drive (VFD) coupled to an output of the one or more inverters and configured to receive AC power from the one or more inverters, wherein the VFD is configured to convert the AC power to DC power and to provide the DC power to at least one auxiliary component during a normal operating condition; and

one or more second bus lines configured to receive the DC signal via the one or more first bus lines and to provide the DC signal to the VFD to power the at least one auxiliary component during a low voltage ride through condition.

2. The fuel cell system of claim 1, further comprising a fuel cell output transformer coupled to the one or more inverters, wherein the VFD is coupled to an output of the fuel cell output transformer.

3. The fuel cell system of claim 1, further comprising one or more auctioneering power diodes coupled to the one or more second bus lines between the one or more first bus lines and the at least one auxiliary component.

4. The fuel cell system of claim 1, wherein the VFD includes an internal rectifier, and wherein the internal rectifier is configured to convert the AC power from the one or more inverters into the DC power.

5. The fuel cell system of claim 1, further comprising one or more contactors on the one or more second bus lines between the one or more first bus lines and the VFD.

6. The fuel cell system of claim 5, further comprising a plant controller that is configured to control the one or more contactors to open and close a connection between the one or more second bus lines and the VFD.

7. The fuel cell system of claim 1, further comprising an uninterruptible power supply that is configured to provide power to at least one control component during the low voltage ride through condition.

8. The fuel cell system of claim 7, wherein the uninterruptible power supply is configured to receive a charge from the output of the one or more inverters during the normal operating condition.

9. The fuel cell system of claim 1, wherein the at least one auxiliary component comprises one or more of a water pump and a blower.

10. A method for operating a fuel cell system during a low voltage ride through condition, the method comprising:

providing power to at least one auxiliary component by way of a variable frequency drive (VFD) during a normal operating condition, wherein the VFD receives power from an output of one or more fuel cell inverters that are coupled to a fuel cell assembly by way of one or more bus lines;

determining that an output of the one or more fuel cell inverters is insufficient to power the at least one auxiliary component; and

responsive to the determination that the output of the one or more fuel cell inverters is insufficient, providing power to the at least one auxiliary component by way of a direct connection between the VFD and the one or more bus lines that connect the fuel cell assembly to the one or more fuel cell inverters.

11. The method of claim 10, further comprising providing power to one or more control components by way of an uninterruptible power supply during the low voltage ride through condition.

12. The method of claim 11, further comprising charging the uninterruptible power supply with the output of the one or more fuel cell inverters during the normal operating condition.

13. The method of claim 10, wherein the determining is performed by one or more auctioneering power diodes coupled to the direct connection.

14. The method of claim 13, wherein the VFD includes an internal rectifier that receives the power from the output of one or more fuel cell inverters.

15. The method of claim 10, further comprising closing one or more contactors on the direction connection responsive to the determination that the output of the one or more fuel cell inverters is insufficient.

16. A method for performing startup of a fuel cell system, the method comprising:

providing power from an electric grid to at least one auxiliary component by way of a variable frequency drive (VFD) during startup of a fuel cell assembly;

determining that the fuel cell assembly has reached an operational temperature;

providing, based at least in part on the determination that the fuel cell assembly has reached the operational temperature, power to the at least one auxiliary component by way of a direct connection between the VFD and one or more bus lines that connect the fuel cell assembly to one or more fuel cell inverters;

determining that a first voltage output from the one or more fuel cell inverters is greater than a second voltage of the direct connection; and

responsive to the determination that the first voltage is greater than the second voltage, providing power from the output of the one or more fuel cell inverters to the at least one auxiliary component by way of the VFD.

17. The method of claim 16, further comprising, responsive to the determination that the fuel cell assembly has reached the operational temperature, closing one more contactors to form the direct connection.

18. The method of claim 16, wherein the first voltage is less than the second voltage when the fuel cell assembly is in an unloaded state, and wherein the fuel cell assembly is not providing power to the electric grid in the unloaded state.

19. The method of claim 16, wherein the first voltage is greater than the second voltage when the fuel cell assembly is in a loaded state, and wherein the fuel cell assembly is providing power to the electric grid in the loaded state.

20. The method of claim 16, further comprising rectifying, by an internal rectifier of the VFD, the power from the electric grid such that DC power is provided by the VFD to the at least one auxiliary component.