In-service fuel cell performance recovery

Patent metadata

Field	Value
Publication number	US-9969297-B2
Application number	US-201615195849-A
Country	US
Kind code	B2
Filing date	Jun 28, 2016
Priority date	Sep 15, 2010
Publication date	May 15, 2018
Grant date	May 15, 2018

Abstract

The performance of a fuel cell power plant that decays, in an electric vehicle which makes frequent starts, is recovered by partially shutting down the power plant. Recovery is enabled by a recovery enable flag upon conditions such as vehicle using low or no power, vehicle speed at or near zero, electric storage SOC above a threshold, and no recovery during the last half-hour (or other duration). The recovery restart resets a timer to ensure that recovery is not attempted too often. The power plant then remains in a recovery stand-by mode until a recovery restart flag is set to 1. The restart causes start-up of the fuel cell power plant, reaching an operational mode.

First claim

The invention claimed is:

1. A method of operating a fuel cell power plant that provides electric power to an electrically propelled vehicle, the method comprising:
recovering fuel cell stack performance when the electrically propelled vehicle is temporarily not moving and is demanding either a small amount of power or no power at all, and
once fuel cell stack performance has been recovered, restoring normal operation of the fuel cell power plant in response to one or more conditions selected from a) a drive system of the electrically propelled vehicle consuming power in excess of a threshold amount, b) a vehicle speed exceeding a speed threshold, and c) an electric energy storage device which receives electric charge from the fuel cell power plant having a state of charge less than a threshold state of charge,
wherein recovering the fuel cell stack performance comprises, in order, disconnecting the electrically propelled vehicle from an electric power output of the fuel cell power plant, connecting one or more voltage limiting devices to the electric power output of the fuel cell power plant, shutting off oxidant supply to cathodes of the fuel cell power plant, and shutting off fuel supply to anodes of the fuel cell power plant, and
wherein coolant flows through the fuel cell power plant throughout the process of recovering fuel cell stack performance.

2. A method of operating a fuel cell power plant that provides electric power to an electrically propelled vehicle, the method comprising:
recovering fuel cell stack performance when the electrically propelled vehicle is temporarily not moving and is demanding either a small amount of power or no power at all,
wherein recovering the fuel cell stack performance comprises, in order, disconnecting the electrically propelled vehicle from an electric power output of the fuel cell power plant, connecting one or more voltage limiting devices to the electric power output of the fuel cell power plant, shutting off oxidant supply to cathodes of the fuel cell power plant, and shutting off fuel supply to anodes of the fuel cell power plant,
wherein coolant flows through the fuel cell power plant throughout the process of recovering fuel cell stack performance, and
wherein recovering fuel cell stack performance is triggered by a recovery enable flag, the recovery enable flag being generated upon satisfaction of all of the following criteria:
average electric power produced by the fuel cell power plant over a recent period is less than a recovery electric threshold;
a recovery timer has reached a time threshold;
a speed of the electrically propelled vehicle is less than a recovery low speed threshold; and
a battery state of charge is greater than a recovery high state of charge threshold.

3. The method of claim 2 wherein normal operation of the fuel cell power plant is reestablished in response to a recovery restart flag, the recovery restart flag being generated upon satisfaction of one or more of the following criteria:
an average drive system power consumption over a recent time interval exceeds a recovery drive power threshold;
a speed of the electrically propelled vehicle exceeds a recovery low speed threshold; and
a battery state of charge is less than a recovery low state of charge threshold.

4. The method of claim 3 , further comprising:
upon generation of the recovery restart flag, resetting the recovery timer.

5. A method of operating a fuel cell power plant that provides electric power to an electrically propelled vehicle, the method comprising:
recovering fuel cell stack performance when the electrically propelled vehicle is temporarily not moving and is demanding either a small amount of power or no power at all,
wherein recovering the fuel cell stack performance comprises, in order, disconnecting the electrically propelled vehicle from an electric power output of the fuel cell power plant, connecting one or more voltage limiting devices to the electric power output of the fuel cell power plant, shutting off oxidant supply to cathodes of the fuel cell power plant, and shutting off fuel supply to anodes of the fuel cell power plant,
wherein coolant flows through the fuel cell power plant throughout the process of recovering fuel cell stack performance, and
wherein recovering fuel cell stack performance is triggered by a recovery enable flag, the recovery enable flag being generated upon satisfaction of the following criteria:
average electric power produced by the fuel cell power plant over a recent period is less than a recovery electric threshold or a speed of the electrically propelled vehicle is less than a recovery low speed threshold; and
a recovery timer has reached a time threshold.

6. The method of claim 5 wherein normal operation of the fuel cell power plant is reestablished in response to a recovery restart flag, the recovery restart flag being generated upon satisfaction of one or more of the following criteria:
an average drive system power consumption over a recent time interval exceeds a recovery drive power threshold;
a speed of the electrically propelled vehicle exceeds a recovery low speed threshold; and
a battery state of charge is less than a recovery low state of charge threshold.

7. The method of claim 6 , further comprising:
upon generation of the recovery restart flag, resetting the recovery timer.

8. A method of operating a fuel cell power plant that provides electric power to an electrically propelled vehicle, the method comprising:
recovering fuel cell stack performance when the electrically propelled vehicle is temporarily not moving and is demanding either a small amount of power or no power at all, and
ensuring that normal operation of the fuel cell power plant will not be reestablished until after the recovery of the fuel cell stack performance is complete,
wherein recovering the fuel cell stack performance comprises, in order, disconnecting the electrically propelled vehicle from an electric power output of the fuel cell power plant, connecting one or more voltage limiting devices to the electric power output of the fuel cell power plant, shutting off oxidant supply to cathodes of the fuel cell power plant, and shutting off fuel supply to anodes of the fuel cell power plant, and
wherein coolant flows through the fuel cell power plant throughout the process of recovering fuel cell stack performance.

9. A method of operating a fuel cell power plant that provides electric power to an electrically propelled vehicle, the method comprising:
recovering fuel cell stack performance when the electrically propelled vehicle is temporarily not moving and is demanding either a small amount of power or no power at all, and
after the recovery of the fuel cell stack performance is complete, determining whether the recovery of the fuel cell stack performance was in response to a recovery enable flag or an absence of a vehicle run request flag,
wherein recovering the fuel cell stack performance comprises, in order, disconnecting the electrically propelled vehicle from an electric power output of the fuel cell power plant, connecting one or more voltage limiting devices to the electric power output of the fuel cell power plant, shutting off oxidant supply to cathodes of the fuel cell power plant, and shutting off fuel supply to anodes of the fuel cell power plant, and
wherein coolant flows through the fuel cell power plant throughout the process of recovering fuel cell stack performance.

10. A method comprising:
when a vehicle, powered by electricity provided by a fuel cell power plant, is demanding little or no power from the fuel cell power plant, as indicated by a recovery enable flag, recovering fuel cell stack p

Assignees

• Audi Ag

Inventors

• Ramaswamy Sitaram
• Yadha Venkateshwarlu
• Wilson Matthew P

Classifications

• B60L50/72

  Constructional details of fuel cells specially adapted for electric vehicles · CPC title

• H01M8/04619

  of fuel cell stacks · CPC title

• H01M8/04228

  during shut-down · CPC title

• H01M8/04753

  of fuel cell reactants · CPC title

• B60L2240/12

  Speed · CPC title