Fuel cell system

Patent metadata

Field	Value
Publication number	US-11476483-B2
Application number	US-202117465330-A
Country	US
Kind code	B2
Filing date	Sep 2, 2021
Priority date	Dec 25, 2020
Publication date	Oct 18, 2022
Grant date	Oct 18, 2022

Abstract

A fuel cell system includes: a fuel cell unit including first to nth fuel cells connected in series to each other to supply electric power to a load device; first to nth supply systems that independently supply cathode gas to the first to nth fuel cells, respectively; a switching device capable of switching a state between a connected state and a disconnected state; and a control unit, when required output to the fuel cell unit is equal to or smaller than a threshold value, configured to control the switching device to switch the state from the connected state to the disconnected state, and to control the first to nth supply systems to respectively control the first to nth fuel cells so as to respectively control flow rates of the cathode gas to be supplied to the first to nth fuel cells.

First claim

The invention claimed is:

1. A fuel cell system comprising:
a fuel cell unit including first to nth (n is an integer equal to or greater than two) fuel cells connected in series to each other to supply electric power to a load device, the first to nth fuel cells each including same unit cells that are stacked;
first to nth supply systems that independently supply cathode gas to the first to nth fuel cells, respectively;
a switching device capable of switching a state between a connected state where the fuel cell unit and the load device are electrically connected to each other and a disconnected state where the fuel cell unit and the load device are electrically disconnected from each other; and
a control unit, when required output to the fuel cell unit is equal to or smaller than a threshold value, configured to control the switching device to switch the state from the connected state to the disconnected state, and to control the first to nth supply systems to respectively control the first to nth fuel cells so as to respectively control flow rates of the cathode gas to be supplied to the first to nth fuel cells,
wherein
the number of stacked unit cells of the nth fuel cell is equal to or greater than the number of stacked unit cells of each of the first to (n−1)th fuel cells,
the control unit is configured to include:
an obtainer configured to obtain, in the disconnected state, first to (n−1)th open circuit voltages of respective open circuit voltages of the first to (n−1)th fuel cells, and a total open circuit voltage of the fuel cell unit; and
a controller configured to respectively control the flow rates of the cathode gas to be supplied to the first to (n−1)th fuel cells to first to (n−1)th large flow rates so as to respectively increase the first to (n−1)th open circuit voltages, when the first to (n−1)th open circuit voltages are respectively equal to or lower than first to (n−1)th lower limit values, and configured to respectively control the flow rates of the cathode gas to be supplied to the first to (n−1)th fuel cells to first to (n−1)th small flow rates respectively smaller than first to (n−1)th large flow rates so as to respectively decrease the first to (n−1)th open circuit voltages, when the first to (n−1)th open circuit voltages are respectively equal to or higher than first to (n−1)th upper limit values,
the controller is configured to control the flow rate of the cathode gas to be supplied to the nth fuel cells to a nth large flow rate so as to increase the total open circuit voltage, when the total open circuit voltage is equal to or lower than a nth lower limit value, and is configured to control the flow rate of the cathode gas to be supplied to the nth fuel cell to a nth small flow rate so as to decrease the total open circuit voltage, when the total open circuit voltage is equal to or higher than a nth upper limit value,
a value obtained by dividing the nth lower limit value by the total number of stacked unit cells of the fuel cell unit is greater than each of values obtained by respectively dividing the first to (n−1)th lower limit values by the number of the stacked unit cells of the first to (n−1)th fuel cells.

2. The fuel cell system according to claim 1 , wherein the controller is configured to switch the flow rate of the cathode gas to be supplied to the nth fuel cell to the nth small flow rate, when the total open circuit voltage is increasing for the first time since the switching device switches the state from the connected state to the disconnected state and before the total open circuit voltage reaches the nth upper limit value.

3. The fuel cell system according to claim 1 , wherein the controller is configured to switch the flow rate of the cathode gas to be supplied to one of the first to (n−1)th fuel cells to a corresponding large flow rate, when the open circuit voltage of the one of the first to (n−1)th fuel cells is decreasing for the first time since the switching device switches the state from the connected state to the disconnected state and before the open circuit voltage of the one of the first to (n−1)th fuel cells reaches a corresponding lower limit value.

4. The fuel cell system according to claim 1 , wherein the controller is configured to switch the flow rate of the cathode gas to be supplied to the nth fuel cell to the nth large flow rate, when the total open circuit voltage is equal to or lower than the nth lower limit value, and when at least one of the first to (n−1)th open circuit voltages is equal to or higher than a predetermined value between a corresponding upper limit value and a corresponding lower limit value.

5. The fuel cell system according to claim 1 , wherein
first timing is timing when any one of the first to (n−1)th open circuit voltages reaches a corresponding lower limit value,
second timing is timing when one of two of the open circuit voltages, among the first to (n−1)th open circuit voltages and the total open circuit voltage, reaches a corresponding lower limit value,
third timing is timing when the other of the two of the open circuit voltages reaches a corresponding lower limit value,
T is a time interval between the first timing,
U is a time interval between the second timing and the third timing adjacent to and after the second timing,
in a case where (½n)>(U/T) is satisfied, the controller is configured to switch the flow rate of the cathode gas to be supplied to the fuel cell corresponding the one of the two of the open circuit voltages to a corresponding large flow rate, when the one of the two of the open circuit voltages is decreasing before the one of the two of the open circuit voltages reaches a corresponding lower limit value,
in a case where (U/T)>( 3/2n) is satisfied, the controller is configured to switch the flow rate of the cathode gas to be supplied to the fuel cell corresponding the other of the two of the open circuit voltages to a corresponding large flow rate, when the other of the two of the open circuit voltages is decreasing before the other of the two of the open circuit voltages reaches a corresponding lower limit value.

6. The fuel cell system according to claim 1 , wherein values obtained by respectively dividing the first to nth small flow rates by the number of stacked unit cells of the first to nth fuel cells are equal to each other.

7. The fuel cell system according to claim 1 , wherein n=2 is satisfied.

8. The fuel cell system according to claim 1 , wherein n=3 is satisfied.

Assignees

• Toyota Motor Co Ltd

Inventors

• Ito Masayuki

Classifications

• H01M8/249 Primary

  comprising two or more groupings of fuel cells, e.g. modular assemblies · CPC title

• H01M8/0488

  of fuel cell stacks · CPC title

• H01M8/04753 Primary

  of fuel cell reactants · CPC title

• H01M8/04619

  of fuel cell stacks · CPC title

• H01M8/04604

  Power, energy, capacity or load · CPC title