Power supply system and voltage control method of fuel cell

Patent metadata

Field	Value
Publication number	US-2016141682-A1
Application number	US-201514938153-A
Country	US
Kind code	A1
Filing date	Nov 11, 2015
Priority date	Nov 15, 2014
Publication date	May 19, 2016
Grant date	—

Abstract

An object is to maintain the voltage of a fuel cell at a desired voltage level and suppress a voltage variation, even in the case of a low load request. A power supply system including a fuel cell causes at least part of a required electric power to be supplied from the fuel cell in an ordinary load state. In a low load state, the power supply system supplies an amount of oxygen that is required to make the voltage of the fuel cell equal to a predetermined target voltage and that is less than an amount of oxygen supplied to the fuel cell in the ordinary load state, to the fuel cell. In a first low load state, the power supply system sets the target voltage to a first target voltage and supplies oxygen to the fuel cell. After a subsequent shift to a state that the required electric power becomes higher than a predetermined reference value to cause the fuel cell to generate electric power at an output voltage that is higher than the first target voltage, in a further shift to a second low load state, the power supply system sets the target voltage to a second target voltage that is higher than the first target voltage and supplies oxygen to the fuel cell.

First claim

What is claimed is:

1 . In a power supply system comprising a fuel cell that supplies electric power to a load, a voltage control method of the fuel cell, comprising:
in an ordinary load state that a required electric power from the load is higher than a predetermined reference value, causing at least part of the required electric power to be supplied from the fuel cell; in a low load state that the required electric power is equal to or lower than the predetermined reference value, supplying an amount of oxygen that is required to make a voltage of the fuel cell equal to a predetermined target voltage and that is less than an amount of oxygen supplied to the fuel cell in the ordinary load state, to the fuel cell; and in a first low load state that the required electric power is equal to or lower than the predetermined reference value, setting the target voltage to a first target voltage and supplying oxygen to the fuel cell, after a subsequent shift to a state that the required electric power becomes higher than the predetermined reference value to cause the fuel cell to generate electric power at an output voltage that is higher than the first target voltage, in a further shift to a second low load state that the required electric power is equal to or lower than the predetermined reference value, setting the target voltage to a second target voltage that is higher than the first target voltage and supplying oxygen to the fuel cell.

2 . The voltage control method of the fuel cell according to claim 1 , further comprising
in the first low load state and in the second low load state, selecting one operation mode among a plurality of operation modes, wherein the plurality of operation modes include
a non-power generation mode that electrically disconnects the fuel cell from the load and supplies an amount of oxygen that is required to make an open circuit voltage of the fuel cell equal to the target voltage, to the fuel cell; and
a low power generation mode that is an operation mode of supplying electric power from the fuel cell to the load and that controls the output voltage of the fuel cell to approach the target voltage and supplies a required amount of oxygen that is theoretically determined from a predetermined target amount of power generation of the fuel cell, to the fuel cell.

3 . The voltage control method of the fuel cell according to claim 2 , further comprising
in the first low load state, selecting the non-power generation mode to supply oxygen to the fuel cell, and in the second low load state, selecting the low power generation mode to supply oxygen to the fuel cell.

4 . The voltage control method. of the fuel cell according to claim 3 , wherein the load includes a main load and an auxiliary load that has a lower required electric power than the main load,
the ordinary load state is a state that requires electric power from at least the main load, and the low load state including the first low load state and the second low load state is a state that requires electric power from the auxiliary load without requiring electric power from the main load.

5 . The voltage control method of the fuel cell according to claim 2 , further comprising
during continuation of a state that selects the low power generation mode, upon satisfaction of a liquid water accumulation condition that liquid water produced in the fuel cell during power generation of the fuel cell in the low power generation mode is excessively accumulated in the fuel cell, temporarily interrupting control in the low power generation mode and supplying an excess amount of oxygen that is higher than an amount of oxygen supplied to the fuel cell in the low power generation mode, to the fuel cell.

6 . The voltage control method of the fuel cell according to claim 5 ,
wherein the power supply system comprises, as part of the load, a power storage unit that is capable of storing at least part of electric power generated by the fuel cell in selection of the low power generation mode, the voltage control method of the fuel cell further comprising during continuation of the state that selects the low power generation mode, upon satisfaction of the liquid water accumulation condition, reducing the target amount of power generation of the fuel cell and causing the fuel cell to generate electric power, prior to temporarily interrupting the control in the low power generation mode.

7 . A power supply system comprising a fuel cell that supplies electric power to a load, the power supply system comprising:
an oxygen supply system that is configured to supply oxygen to a cathode of the fuel cell; and an oxygen supply regulator that is configured to drive the oxygen supply system and regulate an amount of oxygen that is supplied to the cathode by the oxygen supply system, wherein in an ordinary load state that a required electric power from the load is higher than a predetermined reference value, the oxygen supply regulator drives the oxygen supply system to supply an amount of oxygen that causes at least part of the required electric power to be supplied from the fuel cell, to the cathode, and in a low load state that the required electric power is equal to or lower than the predetermined reference value, the oxygen supply regulator drives the oxygen supply system to supply an amount of oxygen that is required to make a voltage of the fuel cell equal to a predetermined target voltage and that is less than an amount of oxygen supplied to the fuel cell in the ordinary load state, to the cathode, wherein in a first low load state that the required electric power is equal to or lower than the predetermined reference value, the oxygen supply regulator sets the target voltage to a first target voltage and drives the oxygen supply system, and after a subsequent shift to a state that the required electric power becomes higher than the predetermined reference value to cause the fuel cell to generate electric power at an output voltage that is higher than the first target voltage, in a further shift to to a second low load state that the required electric power is equal to or lower than the predetermined reference value, the oxygen supply regulator sets the target voltage to a second target voltage that is higher than the first target voltage and drives the oxygen supply system.

8 . The power supply system according to claim 7 , further comprising:
an operation mode selector that is configured to select one operation mode among a plurality of operation modes, the plurality of operation modes including a non-power generation mode that causes the fuel cell to stop power generation and a low power generation mode that causes the fuel cell to supply electric power to the load, as an operation mode of the power supply system in the low load state; a load disconnector that is configured to electrically disconnect the fuel cell from the load, when the operation mode, selector selects the non-power generation mode as the operation mode; and an output voltage controller that is configured to set the output voltage of the fuel cell to the target voltage, when the operation mode selector selects the low power generation mode as the operation mode, wherein when the operation mode selector selects the non-power generation mode as the operation mode, the oxygen supply regulator drives the oxygen supply system to supply an amount of oxygen that is required to make an open circuit voltage of the filet cell equal to the target voltage, to the fuel cell, and when the operation mode selector selects the low power generation mode as the operation mode, the oxygen supply regulator drives the oxygen supply system to supply a required amount of oxygen that is theoretically determined from a pr

Assignees

• Toyota Motor Co Ltd

Inventors

• Yamanaka Tomio
• Nada Mitsuhiro
• Suzuki Hiroyuki
• Ogawa Tomohiro
• Maruo Tsuyoshi

Classifications

• H01M2250/20

  Fuel cells in motive systems, e.g. vehicle, ship, plane · CPC title

• H01M8/04089 Primary

  of gaseous reactants · CPC title

• H01M8/04298

  Processes for controlling fuel cells or fuel cell systems · CPC title

• H01M8/04753 Primary

  of fuel cell reactants · CPC title

• H01M8/04858

  Electric variables · CPC title