POWER SUPPLY SYSTEM AND VOLTAGE CONTROL METHOD FOR FUEL CELL

• US 20160141905A1
• Filed: 11/05/2015
• Published: 05/19/2016
• Est. Priority Date: 11/15/2014
• Status: Active Grant

• Current Assignee: Toyota Jidosha Kabushiki Kaisha (Toyota Motor Corporation)
• Original Assignee: Toyota Jidosha Kabushiki Kaisha (Toyota Motor Corporation)
• Inventors: YAMANAKA, Tomio, NADA, Mitsuhiro, SUZUKI, Hiroyuki
• Granted Patent: US 9,768,631 B2
• Time in Patent Office: Days
• US Class Current: 1/1
• CPC Class Codes: B60L 50/52 characterised by DC-motors
• CPC Class Codes: H01M 2008/1095 Fuel cells with polymeric electrolytes
• CPC Class Codes: H01M 8/04097 with recycling of the reactants H01M8/04119, H01M8/04104 take precedence
• CPC Class Codes: H01M 8/04179 by purging or increasing flow or pressure of reactants
• CPC Class Codes: H01M 8/04223 during start-up or shut-down; Depolarisation or activation, e.g. purging; Means for short-circuiting defective fuel cells
• CPC Class Codes: H01M 8/04388 of anode reactants at the inlet or inside the fuel cell
• CPC Class Codes: H01M 8/04395 of cathode reactants at the inlet or inside the fuel cell
• CPC Class Codes: H01M 8/04559 of fuel cell stacks
• CPC Class Codes: H01M 8/04753 of fuel cell reactants
• CPC Class Codes: H01M 8/0488 of fuel cell stacks
• CPC Class Codes: H01M 8/04955 Shut-off or shut-down of fuel cells
• CPC Class Codes: H02J 2207/20 Charging or discharging characterised by the power electronics converter
• CPC Class Codes: Y02E 60/50 Fuel cells
• CPC Class Codes: Y02T 10/70 Energy storage systems for electromobility, e.g. batteries

Abstract

A voltage control method for a fuel cell may include: interrupting electrical connection between the fuel cell and a load in a low load state; supplying oxygen to the fuel cell in accordance with a preset condition during the electrical connection is interrupted; detecting an OCV of the fuel cell after oxygen is supplied to the fuel cell in accordance with the preset condition; reducing an amount of oxygen supplied to the fuel cell when the OCV is higher than a target voltage by a first value or larger; increasing the amount of oxygen when the OCV is lower than the target voltage by a second value or larger; and keeping the amount of oxygen when the OCV is lower than a sum of the target voltage and the first value and higher than a value obtained by subtracting the second value from the target voltage.

Claims

1. A voltage control method for a fuel cell in a power supply system including the fuel cell configured to supply an electric power to a load, the voltage control method comprising:

interrupting an electrical connection between the fuel cell and the load when the load is in a low load state where an electric power required by the load is less than or equal to a predetermined reference value;

supplying oxygen to the fuel cell based on a preset condition when the electrical connection between the fuel cell and the load is interrupted, the preset condition being a condition for supplying the fuel cell with oxygen required to adjust an open circuit voltage of the fuel cell to a predetermined target voltage;

detecting the open circuit voltage of the fuel cell after oxygen is supplied to the fuel cell based on the preset condition;

in a first voltage state where the detected open circuit voltage is higher than the target voltage by a first value or larger, reducing an amount of oxygen supplied to the fuel cell;

in a second voltage state where the detected open circuit voltage is lower than the target voltage by a second value or larger, increasing the amount of oxygen supplied to the fuel cell; and

in a voltage keeping state where the detected open circuit voltage is lower than a sum of the target voltage and the first value and higher than a value obtained by subtracting the second value from the target voltage, keeping the amount of oxygen supplied to the fuel cell.

2. The voltage control method according to claim 1, further comprising:

determining, in the low load state, whether a first state or a second state applies, the first state being a state where there is a higher probability that the load quickly requires the electric power than a probability that the load quickly requires the electric power in the second state;

using a predetermined first target voltage as the target voltage when it is determined that the first state applies; and

using a second target voltage as the target voltage when it is determined that the second state applies, the second target voltage being lower than the first target voltage.

3. The voltage control method according to claim 1, further comprising:

using a first target voltage as the target voltage when a time elapsed after oxygen is supplied to the fuel cell based on the preset condition in the low load state is shorter than a preset reference time; and

changing the target voltage from the first target voltage to a second target voltage lower than the first target voltage when the preset reference time has elapsed after oxygen is supplied to the fuel cell based on the preset condition.

4. The voltage control method according to claim 1, further comprising:

determining, in the low load state, whether a shift position is a predetermined drive position or a predetermined non-drive position;

using a predetermined first target voltage as the target voltage when the shift position is determined to be the predetermined drive position; and

using a second target voltage as the target voltage when the shift position is determined to be the predetermined non-drive position, the second target voltage being lower than the first target voltage.

5. The voltage control method according to claim 4, further comprising:

using the first target voltage as the target voltage when a time elapsed after oxygen is supplied to the fuel cell based on the preset condition is shorter than a preset reference time and when the shift position is determined to be the predetermined drive position; and

changing the target voltage from the first target voltage to the second target voltage when the preset reference time has elapsed after oxygen is supplied to the fuel cell based on the preset condition and when the shift position is determined to be the predetermined drive position.

6. The voltage control method according to claim 1, further comprising:

determining, in the low load state, whether a vehicle including the fuel cell is in a first state or a second state, the load having a higher probability of requiring a predetermined responsiveness of the electric power in the first state than in the second state, the predetermined responsiveness being higher than or equal to a predetermined level;

using a predetermined first target voltage as the target voltage when the vehicle is in the first state; and

using a second target voltage as the target voltage when the vehicle is in the second state, the second target voltage being lower than the first target voltage.

7. The voltage control method according to claim 1, further comprising:

changing the target voltage from a first target voltage to a second target voltage lower than the first target voltage when the open circuit voltage of the fuel cell decreases, after oxygen is supplied to the fuel cell based on the preset condition in the low load state, by a preset allowable value or larger with respect to the first target voltage set as the target voltage.

8. The voltage control method according to claim 2, further comprising

temporarily stopping supply of oxygen to the fuel cell before oxygen is supplied to the fuel cell after a target value of the open circuit voltage of the fuel cell is changed from the first target voltage to the second target voltage.

9. A voltage control method for a fuel cell in a power supply system including the fuel cell configured to supply an electric power to a load, the voltage control method comprising:

supplying oxygen to the fuel cell based on a preset condition in a low load state where an electric power required by the load is less than or equal to a predetermined reference value, the preset condition being a condition for supplying the fuel cell with oxygen required to adjust a voltage of the fuel cell to a predetermined target voltage;

detecting the voltage of the fuel cell after oxygen is supplied to the fuel cell based on the preset condition;

causing the fuel cell to generate an electric power by setting an output voltage to the target voltage in a first voltage state where the detected voltage is higher than the target voltage by a first value or larger;

in a second voltage state where the detected voltage is lower than the target voltage by a second value or larger, increasing an amount of oxygen supplied to the fuel cell in a state where electrical connection between the fuel cell and the load is interrupted; and

keeping the amount of oxygen supplied to the fuel cell in a voltage keeping state where the detected voltage is lower than a sum of the target voltage and the first value and is higher than a value obtained by subtracting the second value from the target voltage.

10. A power supply system comprising:

a fuel cell configured to supply an electric power to a load;

an oxygen supply device configured to supply oxygen to a cathode of the fuel cell;

an oxygen amount regulator configured to regulate an amount of oxygen supplied to the cathode by the oxygen supply device;

a load interrupter configured to interrupt electrical connection between the fuel cell and the load in a low load state where an electric power required by the load is lower than or equal to a predetermined reference value; and

a voltage sensor configured to detect an open circuit voltage of the fuel cell,

wherein the oxygen amount regulator is further configured to drive the oxygen supply device in accordance with a preset condition in the low load state, the preset condition being a condition for supplying the fuel cell with oxygen required to adjust the open circuit voltage of the fuel cell to a predetermined target voltage,

the oxygen amount regulator is further configured to drive, after the oxygen supply device is driven, the oxygen supply device in a first voltage state to decrease the amount of oxygen supplied to the fuel cell, the first voltage state being a state where the detected open circuit voltage is higher than the target voltage by a first value or larger, and

the oxygen amount regulator is further configured to drive, after the oxygen supply device is driven, the oxygen supply device in a second voltage state to increase the amount of oxygen supplied to the fuel cell, the second voltage state being a state where the detected open circuit voltage is lower than the target voltage by a second value or larger.

11. The power supply system according to claim 10, wherein

the oxygen supply device includes an oxygen supply passage, an oxygen introducing device, a bypass passage, a flow dividing valve, and a flow regulating valve,

the oxygen supply passage is a passage connected to the cathode,

the oxygen introducing device is configured to introduce oxygen into the oxygen supply passage,

the bypass passage branches off from the oxygen supply passage and is configured to guide oxygen supplied from the oxygen introducing device without allowing the oxygen to pass through the cathode,

the flow dividing valve is provided at a position at which the bypass passage branches off from the oxygen supply passage, and is configured to change a proportion of distribution of oxygen distributed between the oxygen supply passage and the bypass passage depending on a state of opening of the flow dividing valve,

the flow regulating valve is provided in the oxygen supply passage, and is configured to change the amount of oxygen supplied to the cathode, and

the oxygen amount regulator is configured to adjust the amount of oxygen supplied to the cathode by changing at least one of an amount of oxygen introduced by the oxygen introducing device, the state of opening of the flow dividing valve, or an opening degree of the flow regulating valve.

12. The power supply system according to claim 11, wherein

the oxygen amount regulator is further configured to adjust the amount of oxygen supplied to the cathode by changing the opening degree of the flow regulating valve in a state where the amount of oxygen introduced by the oxygen introducing device and the state of opening of the flow dividing valve are fixed.

13. A power supply system comprising:

a fuel cell configured to supply an electric power to a load;

an oxygen supply device configured to supply oxygen to a cathode of the fuel cell;

at least one electronic control unit configured to adjust an amount of oxygen supplied by the oxygen supply device to the cathode and to control a state of output of the fuel cell;

a load interrupter configured to interrupt electrical connection between the fuel cell and the load; and

a voltage sensor configured to detect a voltage of the fuel cell,

wherein the electronic control unit is further configured to drive the oxygen supply device in accordance with a preset condition in a low load state, the preset condition being a condition for supplying the fuel cell with oxygen required to adjust the voltage of the fuel cell to a predetermined target voltage,

the electronic control unit is further configured to drive the oxygen supply device to increase the amount of oxygen, which is supplied to the cathode, after the oxygen supply device is driven in accordance with the preset condition, in a second voltage state, and in a state where the load interrupter interrupts the electrical connection between the fuel cell and the load, the second voltage state being a state where the detected voltage is lower than the target voltage by a second value or larger, and

the electronic control unit is configured to control the state of output of the fuel cell to change an output voltage of the fuel cell to the target voltage after the electronic control unit drives the oxygen supply device in accordance with the preset condition, and in a first voltage state where the detected voltage is higher than the target voltage by a first value or larger.