Fuel cell system including Wobbe index detector and method of operating same

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

detecting a change in a Wobbe Index (WI) of a fuel provided to the fuel cell system; and

changing a flow rate of the fuel to the fuel cell stack, based on the detected change in the WI.

2. The method of claim 1 , wherein the detecting a change in the WI comprises:

detecting the WI of the fuel; and

comparing the detected WI to a baseline WI.

3. The method of claim 1 , wherein the detecting a change in the WI comprises comparing the detected WI to a look up table comprising WI's of corresponding fuel compositions.

4. The method of claim 1 , wherein the detecting a change in the WI comprises detecting a first WI of the fuel in a system conduit configured to provide the fuel to a fuel control valve (FCV) that controls a flow rate of the fuel to the fuel cell stack.

5. The method of claim 4 , further comprising detecting a second WI of the fuel in a module conduit that fluidly connects the FCV to the fuel cell stack.

6. The method of claim 5 , further comprising determining a health of the fuel cell system based a comparison of the first WI and the second WI.

7. The method of claim 6 , wherein determining the health of the fuel cell system comprises determining one or more of whether the FCV is operating normally and whether the fuel cell system has a fuel leak.

8. The method of claim 1 , further comprising:

detecting a system pressure of in a fuel conduit configured to provide the fuel to a fuel control valve (FCV) that controls fuel flow to the fuel cell stack;

detecting a module pressure of a module conduit that fluidly connects the FCV to the fuel cell stack; and

comparing the system and module pressures to determine a health of the fuel cell system.

9. A method of operating a fuel cell system comprising power modules configured to receive a fuel from a fuel conduit of the system, the power modules each comprising a fuel cell stack and a fuel control valve (FCV) configured to control fuel flow through a module conduit fluidly connecting the FCV to the fuel cell stack, the method comprising:

detecting a first Wobbe Index (WI) of the fuel in the fuel conduit;

detecting a second WI of the fuel in each module conduit; and

controlling at least one of the FCV's to change a flow rate of the fuel to the corresponding stack, based on a comparison of the first WI and the corresponding second WI, to maintain a substantially constant fuel utilization before and after a change in the composition of the fuel.

10. The method of claim 9 , further comprising:

comparing the first WI to a reference WI; and

controlling at least one of the FCV's to change a fuel flow rate to the corresponding fuel cell stack, when the comparison indicates a change in the composition of the fuel in the fuel conduit, to maintain a substantially constant fuel utilization before and after the change in the composition of the fuel.

11. The method of claim 9 , further comprising:

detecting a system pressure of the fuel in the fuel conduit;

detecting a module pressure of the fuel in each module conduit; and

determining a health of the fuel cell system, based on a comparison of the system pressure and the module pressures.

12. The method of claim 11 , wherein the determining the health of the fuel cell system comprises determining whether the FCV is operating normally, determining whether the fuel cell system has a fuel leak, or a combination thereof.