JP6759573B2 - Fuel cell system control method and fuel cell system - Google Patents

Description

The present invention relates to a control method and a fuel cell system of a fuel cell system including a solid oxide fuel cell that generates electricity by receiving supply of an anode gas and a cathode gas.

Conventionally, a fuel cell system including a solid oxide fuel cell that generates power by an electrochemical reaction between an anode gas (fuel gas) containing hydrogen or hydrocarbons and a cathode gas (air) containing oxygen has been known. ing. In such a fuel cell system, various processes are performed from the system stop operation such as turning off the key switch by the driver or the like until the system is completely stopped. For example, Patent Document 1 discloses a fuel cell system in which a reverse bias voltage is applied to the fuel cell stack when the system is stopped, from the viewpoint of preventing deterioration of the anode electrode of the fuel cell.

On the other hand, in such a fuel cell system, VLC (Voltage) in which the withdrawal current from the fuel cell is set to a predetermined value and the voltage is rapidly lowered as a part of the system stop processing after the above-mentioned system stop operation is performed. Limit Control) processing is performed. During this VLC process, the supply of fuel gas to the fuel cell stack was stopped in order to prevent gas from remaining in the fuel cell after the system was completely shut down.

U.S. Pat. No. 6,620,535

However, in the above VLC process, the take-out current is set so as to rapidly reduce the voltage of the fuel cell even though the supply of fuel gas is stopped, so that the fuel gas and the amount of air are insufficient. Power may be generated, which may affect the performance of the system.

In particular, in a state where the fuel gas is insufficient (anode stabilization), irreversible oxidation of Ni occurs in the catalyst layer constituting the anode electrode and deterioration occurs, which is a major factor in deteriorating the performance of the fuel cell.

Therefore, an object of the present invention is to provide a fuel cell system control method and a fuel cell system capable of suppressing oxidative deterioration of the anode electrode during VLC treatment.

According to an aspect of the present invention, a solid oxide fuel cell that generates power by receiving supply of an anode gas and a cathode gas, a current extraction unit that draws current from the fuel cell, and an anode that supplies the anode gas to the fuel cell. A method of controlling a fuel cell system executed by a fuel cell system including a gas supply unit is provided. In this fuel cell system control method, after a request to stop the fuel cell system, a current take-out unit draws a current from the fuel cell, and the anode gas is used until the voltage of the fuel cell drops to a predetermined value due to the current take-out. Have the supply unit supply the anode gas.

Further, according to another aspect of the present invention, a solid oxide type fuel cell that generates power by receiving the supply of the anode gas and the cathode gas, a current extraction unit that draws current from the fuel cell, and an anode gas in the fuel cell. An anode gas supply unit to be supplied, a voltage value information acquisition unit that acquires the voltage of the fuel cell, a control unit that controls current extraction by the current extraction unit and supply of anode gas by the anode gas supply unit based on the voltage. A fuel cell system equipped with is provided. Then, in this fuel cell system, the control unit causes the current extraction unit to take out a predetermined value of current after the request to stop the fuel cell system, and until the voltage of the fuel cell drops to a predetermined value by taking out the current. , Make the anode gas supply unit execute the supply of anode gas.

According to the present invention, after a request to stop the fuel cell system, a predetermined value of current is taken out from the fuel cell to reduce the voltage to a predetermined value, and fuel is supplied to the fuel cell in the process of reducing the voltage. Become. That is, since fuel is supplied to the fuel cell and the reducing atmosphere of the anode electrode is maintained even during the process of lowering the voltage after the stop request, the fuel gas in the fuel cell is insufficient in the process of lowering the voltage. It is possible to suppress oxidative deterioration of the anode electrode due to the above.

FIG. 1 is a schematic configuration diagram of a solid oxide fuel cell system according to the present embodiment. FIG. 2 is a flowchart showing the flow of system shutdown processing of the solid oxide fuel cell system according to the first embodiment. FIG. 3 is a time chart showing an outline of the progress of the system stop processing. FIG. 4 is a map showing the relationship between the stack temperature and the correction coefficient at the time of stop request. FIG. 5 is a map showing the relationship between the corrected VLC current target value I1'and the fuel injection amount. FIG. 6 is a flowchart showing the flow of system shutdown processing of the solid oxide fuel cell system according to the second embodiment. FIG. 7 is a time chart showing an outline of the progress of the system stop processing. FIG. 8 is a flowchart showing the flow of system shutdown processing of the solid oxide fuel cell system according to the third embodiment. FIG. 9 is a time chart showing an outline of the progress of the system stop processing. FIG. 10 is a diagram schematically showing an aspect of the surface of the anode electrode in one fuel cell. FIG. 11 is a graph showing an outline of changes in the current target value during the VLC process according to the fourth embodiment. FIG. 12 is a time chart showing an outline of the progress of VLC processing according to the fifth embodiment. FIG. 13 is a time chart showing an outline of the progress of VLC processing according to the sixth embodiment. FIG. 14 is a flowchart showing a flow of system stop processing executed in response to the system stop request according to the seventh embodiment. FIG. 15 is a time chart showing an outline of the progress of the system stop processing. FIG. 16 is a flowchart showing a flow of system stop processing executed in response to the system stop request according to the eighth embodiment.

Hereinafter, embodiments of the present invention will be described with reference to the drawings.

(First Embodiment)
FIG. 1 is a schematic configuration diagram showing a main configuration of the solid oxide fuel cell system 100 according to the first embodiment.

As shown in FIG. 1, the fuel cell system 100 is a solid oxide fuel cell system including a solid oxide fuel cell stack 10 that receives a fuel gas as an anode gas and air as a cathode gas to generate power. Yes, it will be installed in vehicles.

The fuel cell stack 10 is a laminated battery in which a plurality of solid oxide fuel cells (SOFCs: Solid Oxide Fuel Cell) are laminated. In one solid oxide fuel cell (fuel cell), an electrolyte layer formed of a solid oxide such as ceramic is sandwiched between an anode electrode to which fuel gas is supplied and a cathode electrode to which air is supplied. It is configured. For example, the fuel gas is a gas containing hydrogen, hydrocarbons, and the like.

The fuel cell system 100 includes a fuel supply mechanism 20 that supplies fuel gas to the fuel cell stack 10, a system start mechanism 30 that is used when starting the system, an air supply mechanism 40 that supplies air to the fuel cell stack 10, and fuel. It is composed of an exhaust mechanism 50 for exhausting the anode-off gas and the cathode-off gas discharged from the battery stack 10 and a power mechanism 60 for inputting and outputting power between the fuel cell stack 10. Further, the fuel cell system 100 includes a control unit 80 that comprehensively controls the operation of the entire system.

The fuel supply mechanism 20 includes a fuel supply passage 21, a fuel tank 22, a filter 23, a pump 24, an injector 25, an evaporator 26, a heat exchanger 27, a reformer 28, and the like. It constitutes an anode gas supply unit.

The fuel supply passage 21 is a passage connecting the fuel tank 22 and the anode flow path formed in the fuel cell stack 10.

The fuel tank 22 is, for example, a container for storing a liquid fuel for reforming, which is a mixture of ethanol and water. The pump 24 is provided in the fuel supply passage 21 on the downstream side of the fuel tank 22. The pump 24 sucks the reforming fuel stored in the fuel tank 22 and supplies the fuel to the injector 25 and the like at a constant pressure.

The filter 23 is arranged in the fuel supply passage 21 between the fuel tank 22 and the pump 24. The filter 23 removes foreign substances and the like contained in the reforming fuel before being sucked into the pump 24.

The injector 25 is arranged in the fuel supply passage 21 between the pump 24 and the evaporator 26. The injector 25 injects and supplies the fuel supplied from the pump 24 into the evaporator 26.

The evaporator 26 is provided in the fuel supply passage 21 on the downstream side of the injector 25. The evaporator 26 vaporizes the fuel supplied from the injector 25 and supplies it to the heat exchanger 27. The evaporator 26 vaporizes the fuel by utilizing the heat of the exhaust gas discharged from the exhaust gas combustor 53 described later.

The heat exchanger 27 is provided in the fuel supply passage 21 on the downstream side of the evaporator 26, and is arranged so as to be adjacent to the exhaust combustor 53. The heat exchanger 27 utilizes the heat transferred from the exhaust combustor 53 to further heat the fuel vaporized in the evaporator 26. A pressure regulating valve 29 for adjusting the pressure of the vaporized fuel supplied to the heat exchanger 27 is provided in the fuel supply passage 21 between the evaporator 26 and the heat exchanger 27. The opening degree of the pressure regulating valve 29 is controlled by the control unit 80.

The reformer 28 is provided in the fuel supply passage 21 between the heat exchanger 27 and the fuel cell stack 10. The reformer 28 reforms the fuel using the catalyst provided in the reformer 28. The reforming fuel is reformed into a fuel gas containing hydrogen, hydrocarbons, carbon monoxide, etc. by a catalytic reaction in the reformer 28. The fuel gas reformed in this way is supplied to the fuel flow path of the fuel cell stack 10 in a high temperature state.

The fuel supply passage 21 includes branch paths 71 and 72 branching from the fuel supply passage 21. The branch path 71 branches from the fuel supply passage 21 between the pump 24 and the injector 25, and connects to the injector 71A that supplies fuel to the diffusion combustor 31. The branch road 71 is provided with an on-off valve 71B that opens and closes the branch road 71. The branch path 72 branches from the fuel supply passage 21 between the pump 24 and the injector 25, and connects to the injector 72A that supplies fuel to the catalyst combustor 32. The branch road 72 is provided with an on-off valve 72B that opens and closes the branch road 72. An electric heater 71C is installed in each of the injectors 71A as a heating device for vaporizing the liquid fuel.

The opening degree of the on-off valves 71B and 72B described above is controlled by the control unit 80. The on-off valves 71B and 72B are opened, for example, when the fuel cell system 100 is started, and closed after the start is completed.

Next, the air supply mechanism 40 and the system activation mechanism 30 will be described.

The air supply mechanism 40 includes an air supply passage 41, a filter 42, an air blower 43, a heat exchanger 44, and the like. The system activation mechanism 30 includes a diffusion combustor 31, a catalyst combustor 32, and the like.

The air supply passage 41 is a passage that connects the air blower 43 and the cathode flow path formed in the fuel cell stack 10.

The air blower 43 is an air supply device that takes in outside air (air) through a filter 42 and supplies the taken in air as a cathode gas to the fuel cell stack 10 and the like. The filter 42 removes foreign matter contained in the air before it is taken into the air blower 43.

The heat exchanger 44 is provided in the air supply passage 41 on the downstream side of the air blower 43. The heat exchanger 44 is a device that heats air by utilizing the heat of the exhaust gas discharged from the exhaust combustor 53. The air heated by the heat exchanger 44 is supplied to the diffusion combustor 31 which forms a part of the system activation mechanism 30.

A throttle 45 is provided in the air supply passage 41 between the air blower 43 and the heat exchanger 44, and the air flow rate is adjusted according to the opening degree of the throttle 45. The opening degree of the throttle 45 is controlled by the control unit 80.

The air supply passage 41 includes a branch path 46 that branches from the air supply passage 41. The branch path 46 branches from the air supply passage 41 between the air blower 43 and the throttle 45, and connects to the catalyst combustor 32 described later. A throttle 46A is attached to the branch path 46, and the air flow rate is adjusted according to the opening degree of the throttle 46A. The opening degree of the throttle 46A is controlled by the control unit 80. The throttle 46A is opened so as to supply a constant amount of air to the catalyst combustor 32 when the fuel cell system 100 is started, and is closed after the start is completed.

The diffusion combustor 31 and the catalyst combustor 32 constituting the system activation mechanism 30 are basically devices used during system activation.

The diffusion combustor 31 is arranged in the air supply passage 41 on the downstream side of the heat exchanger 44. When the system is started, the air from the air blower 43 and the fuel injected from the injector 71A are supplied into the diffusion combustor 31. The fuel injected from the injector 71A is heated by the electric heater 71C and supplied to the diffusion combustor 31 in a vaporized state. Then, the air-fuel mixture is ignited by the ignition device attached to the diffusion combustor 31, and a preheating burner for heating the catalyst combustor 32 is formed.

After the start-up is completed, the fuel supply and the operation of the ignition device are stopped, and the air supplied from the air blower 43 passes through the diffusion combustor 31 and is supplied to the catalyst combustor 32.

The catalyst combustor 32 is provided in the air supply passage 41 between the diffusion combustor 31 and the fuel cell stack 10. The catalyst combustor 32 has a catalyst inside, and is a device that generates a high-temperature combustion gas using the catalyst. When the system is started, the air from the branch path 46 and the fuel injected from the injector 72A are supplied into the catalyst combustor 32. The catalyst of the catalyst combustor 32 is heated by a preheating burner, and air and fuel are burned on the heated catalyst to generate combustion gas. The combustion gas is a high-temperature inert gas containing almost no oxygen, and is supplied to the fuel cell stack 10 to heat the fuel cell stack 10 and the like.

After the start-up is completed, the supply of fuel is stopped from the branch paths 72 and 72, and the air from the air blower 43 passes through the diffusion combustor 31 and the catalyst combustor 32 and is supplied to the fuel cell stack 10.

Next, the exhaust mechanism 50 will be described. The exhaust mechanism 50 includes an anode off-gas discharge passage 51, a cathode-off gas discharge passage 52, an exhaust combustor 53, a confluence exhaust passage 54, and the like.

The anode off-gas discharge passage 51 connects the anode gas flow path in the fuel cell stack 10 and the anode-side inlet portion of the exhaust combustor 53. The anode off-gas discharge passage 51 is a passage through which an exhaust gas (anode-off gas) including fuel gas discharged from the fuel flow path of the fuel cell stack 10 flows. Further, the anode off-gas discharge passage 51 is provided with a shutoff valve 55 near the anode gas flow path of the fuel cell stack 10. The shutoff valve 55 is a so-called normally closed type valve that is closed in an uncontrolled state and is opened based on a control signal from the control unit 80.

The cathode off gas discharge passage 52 connects the cathode flow path in the fuel cell stack 10 and the cathode side inlet portion of the exhaust combustor 53. The cathode off gas discharge passage 52 is a passage through which an exhaust gas (cathode off gas) including air discharged from the cathode flow path in the fuel cell stack 10 flows.

The exhaust combustor 53 catalytically burns the anode-off gas and the cathode-off gas supplied from the discharge passages 51 and 52 and merged to generate exhaust gas containing carbon dioxide or water as a main component. At the time of system startup, fuel and air may be supplied to the exhaust combustor 53 to promote catalyst combustion in the exhaust combustor 53, thereby increasing the efficiency of raising the catalyst temperature.

Since the exhaust combustor 53 is arranged adjacent to the heat exchanger 27, the heat generated by the catalytic combustion of the exhaust combustor 53 is transferred to the heat exchanger 27. The heat transferred to the heat exchanger 27 in this way is used to heat the fuel.

A confluence exhaust passage 54 is connected to the gas outlet portion (downstream end) of the exhaust combustor 53. The exhaust gas discharged from the exhaust gas combustor 53 is discharged to the outside of the fuel cell system 100 through the confluence exhaust passage 54. The confluence exhaust passage 54 is configured to pass through the evaporator 26 and the heat exchanger 44, and the evaporator 26 and the heat exchanger 44 are heated by the exhaust passing through the confluence exhaust passage 54.

Next, the electric power mechanism 60 will be described. The electric power mechanism 60 includes a DC-DC converter 61, a battery 62, a drive motor 63, and an inverter.

The DC-DC converter 61 is electrically connected to the fuel cell stack 10 and boosts the output voltage of the fuel cell stack 10 to supply power to the battery 62 or the drive motor 63. The battery 62 is configured to charge the electric power supplied from the DC-DC converter 61 and to supply the electric power to the drive motor 63. Therefore, the output current (take-out current) is adjusted by appropriately raising and lowering the output voltage of the fuel cell stack 10 by the DC-DC converter 61. That is, the DC-DC converter 61 functions as a current extraction unit.

Further, the battery 62 is provided with an SOC sensor 64. The SOC sensor 64 estimates the SOC of the battery 62 based on the battery voltage and current detected by a voltage sensor and a current sensor (not shown).

The drive motor 63 is a three-phase AC motor and functions as a power source for the vehicle. The drive motor 63 is connected to the battery 62 and the DC-DC converter 61 via an inverter (not shown). During braking, the drive motor 63 generates regenerative power, and this regenerative power is used, for example, to charge the battery 62.

The control unit 80 includes a microcomputer including a central processing unit (CPU), a read-only memory (ROM), a random access memory (RAM), and an input / output interface (I / O interface). The control unit 80 executes a process for controlling the fuel cell system 100 by executing a specific program.

The control unit 80 receives signals from various sensors such as the SOC sensor 64, the current sensor 81, the voltage sensor 82, the stack temperature sensor 83, the fuel gas pressure sensor 90, and the air pressure sensor 92, as well as the amount of depression of the accelerator pedal. A signal from a sensor that detects the vehicle state, such as the accelerator stroke sensor 86 to be detected, is input. Further, the control unit 80 controls the opening and closing of various valves such as the throttle 45 and the shutoff valve 55 and the output control of the actuator such as the pump 24 based on these signals.

The current sensor 81 detects an output current (hereinafter, also referred to as “stack current”) as a take-out current taken out from the fuel cell stack 10. The voltage sensor 82 detects the output voltage of the fuel cell stack 10 (hereinafter, also referred to as “stack voltage”), that is, the voltage between the terminals between the anode electrode side terminal and the cathode electrode side terminal.

The stack temperature sensor 83 is provided on the fuel cell stack 10 and detects the temperature of the fuel cell stack 10 (hereinafter, also referred to as “stack temperature”).

The fuel gas pressure sensor 90 is provided between the reformer 28 and the fuel cell stack 10 and detects the pressure of the fuel gas supplied to the fuel cell stack 10.

The air pressure sensor 92 is provided between the catalyst combustor 32 and the fuel cell stack 10 and detects the pressure of the air supplied to the fuel cell stack 10.

Further, in the present embodiment, the control unit 80 calculates the current target value of the fuel cell stack 10 based on the required power from the load device such as the battery 62 and the drive motor 63. Then, the control unit 80 controls the DC-DC converter 61 so that the stack current approaches this current target value.

Further, the control unit 80 calculates the fuel gas supply flow rate to be supplied to the fuel cell stack 10 from the fuel gas pressure detection value of the fuel gas pressure sensor 90 based on the pressure-flow rate map created in advance. Then, the control unit 80 adjusts the output of the pump 24 so that the calculated fuel gas supply flow rate approaches a predetermined fuel gas flow rate target value. That is, the fuel injection amount by the injector 25 is adjusted.

Further, the control unit 80 calculates the air flow rate supplied to the fuel cell stack 10 from the pressure detection value of the cathode gas of the air pressure sensor 92 based on the pressure-flow rate map created in advance. Then, the control unit 80 adjusts the opening degree of the throttle 45 so that the calculated air flow rate approaches a predetermined air flow rate target value corresponding to the fuel gas flow rate target value.

In the present embodiment, in the stack cooling process (after power generation is stopped) in which the temperature of the fuel cell stack 10 is lowered to a predetermined target temperature, the control unit 80 is based on the detection value of the stack temperature by the stack temperature sensor 83. , The air flow rate supplied to the fuel cell stack 10 is adjusted.

In the solid oxide fuel cell system 100 having the configuration described above, the power supply to the motor 63 is cut off in response to a system stop request such as a key-off operation of the vehicle driver or an idle stop command when the battery 62 is fully charged. Then, the system stop process is executed.

Then, in the first half of the system stop processing of the fuel cell system 100, VLC (Voltage Limit Control) processing is performed in order to rapidly reduce the stack voltage to a predetermined limit voltage for reasons such as safety at the time of stop. Be told. During this VLC processing, in order to reduce the stack voltage, a predetermined current target value (hereinafter, also referred to as “VLC current target value I1”) is set as the target value of the current taken out from the fuel cell stack 10. Since the power supply to the auxiliary equipment such as the motor 63 is cut off during the VLC processing, the current target value I1 for VLC is set to a value smaller than the current target value before the VLC processing.

FIG. 2 is a flowchart showing a flow of system stop processing executed in response to the system stop request according to the present embodiment. Further, FIG. 3 is a time chart showing an outline of the progress of the system stop processing according to the present embodiment.

In step S110, the control unit 80 starts the VLC process. In this VLC process, the target value of the stack current is set to the VLC current target value I1 at the time t1 when the system stop request is issued. Then, in the present embodiment, the fuel gas supply flow rate (that is, the fuel injection amount by the injector 25) and the air supply flow rate to the fuel cell stack 10 are set to A1 and C1, respectively (FIGS. 3 (c) and 3). (D)).

Specifically, in the present embodiment, the fuel injection amount A1 is the corrected current target value I1'(corrected VLC current target value I1' obtained by multiplying the VLC current target value I1 by a predetermined correction coefficient α (0 <α <1). It is determined based on I1'<I1).

FIG. 4 is a map showing the relationship between the stack temperature at the time of stop request and the correction coefficient α. As shown in the figure, the correction coefficient α becomes smaller as the stack temperature at the time of requesting stop increases. That is, the corrected VLC current target value I1'is set smaller as the stack temperature increases.

FIG. 5 is a map showing the relationship between the corrected VLC current target value I1'and the fuel injection amount. As shown in the figure, the fuel injection amount A1 is set larger as the VLC current target value I1 is set higher.

Therefore, the higher the stack temperature at the time of requesting stop, the smaller the fuel injection amount A1 is set. This is because when the stack temperature is high, the power generation efficiency of the fuel cell stack 10 is high, so that a desired voltage drop rate can be realized even if the fuel injection amount A1 is reduced.

On the other hand, the air supply flow rate C1 is set to a stoichiometric ratio of 1 or more with respect to the fuel injection amount A1 described above. In particular, in consideration of the bias of the oxygen concentration distribution of the cathode gas in the surface of the fuel cell, the fuel having the air supply flow rate C1 is prevented from being generated in the cell surface so that the oxygen concentration becomes unsuitable for power generation. It is preferable that the stoichiometric ratio with respect to the injection amount A1 exceeds 1. The fuel injection amount A1 and the air supply flow rate C1 are smaller than the fuel injection amount and the air supply flow rate required to maintain the stack voltage according to the corrected VLC current target value I1'.

Therefore, during the VLC processing at time t1 to time t2, the fuel injection amount A1 and the air supply flow rate C1 are smaller than the flow rates required to maintain the stack voltage with respect to the corrected VLC current target value I1'. , The stack voltage drops (see FIG. 3B).

Returning to FIG. 2, in step S120, the control unit 80 determines whether or not the stack voltage is equal to or less than the limit target voltage V1 which is the limit target voltage of the VLC process. When it is determined that the stack voltage is not equal to or less than the limit target voltage V1, the process returns to step S110, fuel supply and air supply are continued, and power generation is continued.

On the other hand, when it is determined that the stack voltage is equal to or less than the limit target voltage V1, the control unit 80 ends the VLC process in step S130 (time t2 in FIG. 3). Specifically, the current target value is set to zero (see FIG. 3E), and power generation is stopped.

The fuel injection is stopped after the time t2 when the power generation is stopped (see FIG. 3C). On the other hand, since the stack cooling process is performed, the air supply is continued (see FIG. 3D). Further, for power supply to the air supply mechanism 40 for air supply after the power generation is stopped, it is preferable to operate the air blower 43 with surplus power of the battery 62 or the like. In this embodiment, the air flow rate of the stack cooling process is also set to C1 which is the same as that during the VLC process. However, during the stack cooling process, air may be supplied to the fuel cell stack 10 at a flow rate different from that during the VLC process.

Returning to FIG. 2, in step S140, the control unit 80 determines whether or not the stack temperature is equal to or less than the temperature reduction target value T1 at which the system stop processing should be completed. If it is determined that the stack temperature is not equal to or less than the temperature reduction target value T1, the air supply is continued until the stack temperature becomes equal to or less than the temperature reduction target value T1. As a result, the fuel cell stack 10 is cooled by air.

On the other hand, when it is determined that the stack temperature is equal to or lower than the temperature reduction target value T1, the control unit 80 stops the air supply in step S150 (time t3 in FIG. 3D). As a result, the system stop process is completed.

According to the control method of the fuel cell system 100 described above, the following effects can be obtained.

The control method according to the present embodiment is a fuel cell stack 10 which is a solid oxide type fuel cell that generates power by receiving a fuel gas as an anode gas and an air as a cathode gas, and a current from the fuel cell stack 10. It is executed by the fuel cell system 100 including a DC-DC converter 61 as a current extraction unit for taking out, and a fuel supply mechanism 20 as an anode gas supply unit for supplying fuel to the fuel cell stack 10. Then, in this control method, the control unit 80 causes the DC-DC converter 61 to take out the current of the predetermined value I1 from the fuel cell stack 10 after the stop request (operation of the key switch, etc.) of the fuel cell system 100, and take out the current. The fuel supply mechanism 20 is made to supply the fuel gas until the voltage of the fuel cell stack 10 drops to the predetermined limit target voltage V1.

That is, according to the present embodiment, the solid oxide type fuel cell stack 10 that generates power by receiving the supply of fuel gas and air, the DC-DC converter 61 that draws current from the fuel cell stack 10, and the fuel cell stack 10 A fuel supply mechanism 20 that supplies fuel to the fuel cell stack 10, a voltage sensor 82 as a voltage information acquisition unit that acquires the voltage (stack voltage) of the fuel cell stack 10, and a current extraction unit that extracts current based on the stack voltage (for VLC). A fuel cell system including a control unit 80 for controlling a current target value) and a fuel gas supply flow rate is provided. Then, in this fuel cell system, the control unit 80 causes the current extraction unit to extract the VLC current target value I1 as a predetermined current after the request to stop the fuel cell system, and the stack voltage is limited by the current extraction. The fuel supply mechanism 20 is made to supply the fuel gas until the target voltage V1 is lowered.

As a result, after the fuel cell system 100 is requested to stop, the current of the predetermined value I1 is taken out from the fuel cell stack 10 and the voltage is lowered to the limit target voltage V1. In the process of lowering the voltage, the fuel is added to the fuel cell stack 10. It will be supplied. That is, since fuel is supplied to the fuel cell stack 10 and the reducing atmosphere of the anode electrode is maintained even during the process of lowering the voltage after the stop request (VLC process), the fuel cell stack 10 during the VLC process is maintained. It is possible to suppress oxidative deterioration of the anode electrode due to a shortage of fuel gas inside.

In particular, in the present embodiment, the control unit 80 adjusts the fuel injection amount by the fuel supply mechanism 20 based on the corrected current target value I1'for VLC. As a result, the fuel injection amount by the fuel supply mechanism 20 is preferably determined according to the magnitude of the current taken out during the VLC process. In particular, by making the fuel injection amount smaller than the fuel injection amount required to maintain the stack voltage according to the corrected current target value I1'for VLC, the reduction of the stack voltage in the VLC process is preferably executed. be able to.

Further, in the control method according to the present embodiment, the control unit 80 corrects the supply flow rate of the fuel gas by the fuel supply mechanism 20 based on the stack temperature which is the temperature of the fuel cell stack 10 (FIGS. 4 and 5).

Thereby, during the VLC process, the fuel gas supply flow rate to the fuel cell stack 10 can be preferably adjusted according to the power generation efficiency of the fuel cell stack 10.

In the present embodiment, after the stack cooling process in step S140 is completed, a process of purging the fuel remaining in the anode off-gas discharge passage 51 may be performed.

(Second Embodiment)
Hereinafter, the second embodiment will be described. The same elements as those described in the first embodiment are designated by the same reference numerals, and the description thereof will be omitted. In this embodiment, the shutoff valve 55 (see FIG. 1) is closed at the end of the VLC process.

FIG. 6 is a flowchart showing a flow of system stop processing executed in response to the system stop request according to the present embodiment. Further, FIG. 7 is a time chart showing an outline of the progress of the system stop processing according to the present embodiment. Since the change in the target current value is the same as in the first embodiment, it is omitted in the time chart of FIG.

As shown in FIG. 6, the process of step S110 is executed as in the first embodiment.

Then, in step S120, when the control unit 80 determines that the stack voltage is equal to or less than the limit target voltage V1 for VLC processing, the shutoff valve 55 is closed in step S210 (see time t2 in FIG. 7 (f)). ). As a result, the backflow of the anode off gas from the anode off gas discharge passage 51 to the fuel cell stack 10 after the completion of the VLC treatment is prevented, and the reducing atmosphere in the anode electrode of the fuel cell stack 10 is maintained.

In particular, in the fuel cell system 100 according to the present embodiment, since the air supply is continued in the VLC process and the stack cooling process after the system stop request, the air supply passage 41 in FIG. 1 and the cathode passage in the fuel cell stack 10 And the pressure of the cathode system including the cathode flow path is maintained above a certain level.

On the other hand, since the fuel supply is stopped after the end of the VLC process (time t2 in FIG. 7C), in the process of the stack cooling process, the fuel supply passage 21 and the fuel cell stack 10 in FIG. 1 Since the pressure is lower than the pressure in the anode off-gas discharge passage 51, the backflow of the anode-off gas from the anode-off gas discharge passage 51 into the anode passage of the fuel cell stack 10 is likely to occur.

Therefore, the air contained in the backflow anode off-gas may cause an oxidation reaction that reacts with constituent members such as a catalyst layer at the anode electrode of the fuel cell stack 10.

In response to such a situation, in the present embodiment, as in step S210, by closing the shutoff valve 55 after the completion of the VLC treatment, the backflow of the anode off gas is prevented, and the process of the stack cooling treatment after the VLC treatment is performed. However, the reducing atmosphere of the anode electrode can be maintained, and its oxidative deterioration can be suppressed more effectively.

Returning to FIG. 6, after that, the processes of step S130, step S140, and step S150 are performed in the same manner as in the first embodiment.

According to the control method of the fuel cell system 100 described above, the following effects can be obtained.

In the control method according to the present embodiment, the shutoff valve 55 provided in the anode off-gas discharge passage 51 of the fuel cell stack 10 is closed after the stack voltage as the fuel cell voltage drops to the limit target voltage V1.

As a result, the backflow of off-gas from the anode off-gas discharge passage 51 to the fuel cell stack 10 after the end of the VLC treatment is prevented, and the reducing atmosphere in the anode electrode of the fuel cell stack 10 can be maintained. Therefore, the reducing atmosphere of the anode electrode can be maintained even after the VLC treatment, and oxidative deterioration of the anode electrode can be more preferably prevented.

If the shutoff valve 55 can prevent the anode off-gas from flowing back into the fuel cell stack 10 from the anode off-gas discharge passage 51, the shutoff valve 55 starts from the stop request (at the start of the VLC process) to the end of the VLC process. It may be blocked at any time until after a predetermined time has elapsed.

(Third Embodiment)
Hereinafter, the third embodiment will be described. The same elements as those described in the second embodiment are designated by the same reference numerals, and the description thereof will be omitted. In the present embodiment, the shutoff valve 55 closed at the end of the VLC treatment in the second embodiment is opened after the stack cooling treatment is completed, and the anode off-gas discharge passage 51 is purged.

FIG. 8 is a flowchart showing a flow of system stop processing executed in response to the system stop request according to the present embodiment. Further, FIG. 9 is a time chart showing an outline of the progress of the system stop processing according to the present embodiment.

As shown in FIG. 8, steps S110 to S120, steps S210, and step S130 are executed in the same manner as in the second embodiment.

Then, when it is determined in step S140 that the stack temperature is equal to or lower than the temperature lowering target value T1, in step S310, the control unit 80 opens the shutoff valve 55 (time in FIGS. 9A and 9F). t3).

Next, in step S320, a purge process is performed. Specifically, while the shutoff valve 55 is open, the air blower 43 continues to supply air to the fuel cell stack 10 (time t3 to time t4 in FIG. 9D). As a result, the cathode gas is sent from the anode passage in the stack to the fuel supply passage 21 and the anode off-gas discharge passage 51, and the residual gas in these passages is purged.

Then, when the purge process in step S320 is completed, in step S330, the control unit 80 closes the shutoff valve 55 again (time t4 in FIG. 9F). As a result, after the system is completely stopped, impurities are prevented from entering the anode electrode due to backflow or the like into the fuel cell stack 10 through the confluence exhaust passage 54 and the anode off gas discharge passage 51, and the next startup of the system is facilitated. be able to.

Then, in step S150, the control unit 80 stops the air supply when the shutoff valve 55 in step S320 is closed (time t4 in FIG. 9D).

According to the control method of the fuel cell system 100 described above, the following effects can be obtained.

In the control method according to the present embodiment, when the stack temperature, which is the temperature of the fuel cell, becomes the temperature lowering target value T1 or less, the shutoff valve 55 is opened to continue the air supply to the fuel cell stack 10 as a purge process. .. In particular, in the present embodiment, when the stack temperature becomes T1 or less, which is the cooling target temperature in the stack cooling process, the shutoff valve 55 is opened to continue air supply. As a result, the residual gas in the anode supply system and the like can be purged in the process of system stop processing, and the residual gas can be suppressed from being discharged at the next startup of the fuel cell system 100.

In the present embodiment, when the purge process is completed, the shutoff valve 55 is closed to end the system stop process. However, after the purge process is completed, the system stop process is ended with the shutoff valve 55 open. You may try to do it.

Further, in the present embodiment, as the purge process, air is continuously supplied to the fuel cell stack 10 at the same air supply flow rate from the stack cooling process, but for example, the air supply flow rate is increased or decreased as compared with the stack cooling process. You may do so. In particular, by increasing the air supply flow rate as compared with the stack cooling process, the cleaning effect in the anode system can be further improved. Further, instead of supplying air to the fuel cell stack 10, the purging process may be performed using an arbitrary inert gas.

(Fourth Embodiment)
Hereinafter, the fourth embodiment will be described. The same elements as those described in the first embodiment are designated by the same reference numerals, and the description thereof will be omitted.

In this embodiment, basically the same processing as in the first embodiment is performed, but it differs from the first embodiment in that the stack current during the VLC processing is reduced with time. In the present embodiment, from the viewpoint of preventing a local gas shortage (in-plane starvation) that may occur due to a difference in the distribution (current distribution) of generated power at each location in the surface of the fuel cell, the above-mentioned VLC treatment is in progress. The current is adjusted.

The details of in-plane starvation will be described below.

FIG. 10 is a diagram schematically showing the surface of the anode electrode of one fuel cell according to the present embodiment. The broken line circle represents a hole through which air as a cathode gas passes.

On the surface of the anode pole of the fuel cell shown in FIG. 10 (hereinafter, also referred to as the anode surface 11), a fuel inlet 120 for passing fuel gas before being used for power generation and a fuel used for power generation are placed on the surface. A fuel discharge port 122 through which the fuel is passed is provided. The fuel introduction port 120 allows the fuel gas sent from the fuel supply passage 21 to flow in one direction (the back side of the paper in the figure) in the cell stacking direction. Then, a part of the fuel gas flowing through the fuel introduction port 120 is supplied onto the anode surface 11 and used for power generation in the power generation area 124 of the anode surface 11.

Further, the fuel discharge port 122 is a passage through which the rest of the combustion gas used for power generation in the power generation area 124 flows to the other side (the front side of the paper in the figure) in the stacking direction of the cells. In the figure, the flow of fuel gas in the anode surface 11 is schematically shown as an arrow F.

Here, on the anode surface 11 shown in the figure, as described above, the fuel gas from the fuel introduction port 120 reacts with air in the power generation area 124 until it reaches the fuel discharge port 122 to generate electricity.

Here, as shown by the arrow F in the figure, the fuel gas flows from the fuel introduction port 120 to the fuel discharge port 122, and is generated in the power generation area 124 in this process. Therefore, mainly, the fuel gas having a relatively high concentration is distributed at the position near the fuel introduction port 120 in the power generation area 124, so that the amount of power generated is high. On the other hand, the closer to the fuel discharge port 122, the lower the fuel gas concentration, so that the amount of power generated increases. That is, the distribution of the fuel gas in the anode surface 11 varies, and the distribution of the generated power becomes uneven.

Due to such variation in the distribution of fuel gas, it is considered that the reducing atmosphere is not maintained and the oxidation reaction proceeds, especially in the vicinity of the fuel discharge port 122 where the fuel gas is insufficient, and the catalyst layer of the anode electrode already described. Oxidation of Ni may occur and deterioration may progress. In particular, when the voltage is rapidly lowered as in the VLC treatment, the variation in the fuel gas distribution becomes large, and the oxidation reaction easily proceeds.

Therefore, in the present embodiment, the current is adjusted during the VLC treatment so as to suppress the oxidative deterioration of the anode due to such in-plane starvation.

FIG. 11 is a graph showing an outline of changes in the current target value during VLC processing according to the present embodiment. In this graph, the current target value during VLC processing according to the present embodiment is shown by a solid line, and for comparison, the current target value during VLC processing according to the first embodiment is shown by a dashed line.

As shown in the figure, in the present embodiment, the target current value is changed according to the elapsed time during the VLC process. Specifically, the target current value is set to gradually decrease from the start of the VLC process at time t1 to the time t2', which is the end of the VLC process in the present embodiment.

As a result, the rate of decrease of the stack voltage during the VLC process becomes slow, so that the oxidative deterioration of the anode due to the in-plane stabilization caused by the abrupt decrease of the stack voltage is suppressed.

The target current value is not limited to the curvilinear decrease shown in FIG. 11, and may be linearly decreased. However, if the target current value is significantly reduced, the VLC processing time becomes longer, which in turn causes an extension of the system stop processing time. Therefore, the target current value is reduced or decreased to the extent that an excessive system stop processing time is not caused. It is preferable to adjust the speed.

According to the control method of the fuel cell system 100 described above, the following effects can be obtained.

In the control method according to the present embodiment, the stack current, which is the fuel cell take-out current by the DC-DC converter 61 as the current take-out unit, is set after the stack voltage, which is the fuel cell voltage, starts to decrease (time t1). Decrease according to the elapsed time of. More specifically, after the VLC process is started, the target current value is changed so as to decrease according to the elapsed time.

As a result, the rate of decrease in the stack voltage during the VLC process can be slowed down, and in-plane starvation due to a sudden decrease in the stack voltage can be suppressed.

(Fifth Embodiment)
Hereinafter, the fifth embodiment will be described. The same elements as those described in the first embodiment are designated by the same reference numerals, and the description thereof will be omitted.

In the present embodiment, basically the same processing as in the first embodiment is performed, but the fuel injection amount is controlled according to the stack voltage at the time of stop request, which is the state of the fuel cell stack 10 at the time of stop request. Is different from the first embodiment.

FIG. 12 is a time chart showing an outline of the progress of VLC processing according to the present embodiment. In the time chart of FIG. 12, for the sake of simplification of the drawing, the stack cooling process other than the VLC process is omitted.

As shown in FIG. 12 (c), in the present embodiment, the fuel injection and the air supply to the fuel cell stack 10 are stopped when the system is requested to be stopped, that is, at the time t1 when the VLC process is started. Then, a small amount of fuel is injected at the time t1'after the lapse of a predetermined time from the time t1. Further, as shown in FIG. 12D, air is supplied to the fuel cell stack 10 at a stoichiometric ratio of 1 or more with respect to this fuel injection amount. Here, the time t1'is the time when the stack voltage drops from the time t1 and reaches the predetermined value V2.

As described above, in the present embodiment, a small amount of fuel is injected and air is supplied at the stage (time t1') when the stack voltage drops to the predetermined value V2 from the start of the stop VLC process, so that the fuel cell stack 10 is charged. Since the fuel and air can be mixed and appropriately distributed in the anode surface and the cathode surface of the cell, it is possible to mitigate the occurrence of in-plane stabilization caused by a sudden drop in stack voltage in the VLC process.

According to the control method of the fuel cell system 100 described above, the following effects can be obtained.

In the control method according to the present embodiment, the control unit 80 controls the supply of fuel by the fuel supply mechanism 20 according to the stack voltage which is the state of the fuel cell stack 10 at the time of the stop request. In particular, in the present embodiment, a small amount of fuel injection and air supply are performed when the stack voltage drops to a predetermined value V2 from the start of the VLC process (see time t1'in FIGS. 12 (c) and 12 (d)). ..

As a result, during the VLC processing, the fuel and air in the fuel cell stack 10 can be mixed and appropriately distributed in the anode surface and the cathode surface of the cell, which is caused by a sudden drop in the stack voltage in the VLC processing. It is possible to mitigate the occurrence of in-plane stabilization. As a result, deterioration of anodic oxidation due to VLC treatment can be suppressed more effectively.

In the present embodiment, fuel injection is performed when the stack voltage drops to a predetermined value V2, but for example, it is based on the state of the fuel cell stack 10 other than the stack voltage such as the internal impedance of the fuel cell stack 10. Therefore, the fuel injection amount and the fuel injection timing may be controlled. Further, the fuel injection amount may be appropriately adjusted according to various states of the fuel cell stack 10 such as the rate of decrease of the stack voltage.

(Sixth Embodiment)
Hereinafter, the sixth embodiment will be described. The same elements as those described in the fifth embodiment are designated by the same reference numerals, and the description thereof will be omitted.

In the present embodiment, based on the configuration of the fifth embodiment, the control unit 80 monitors the stack voltage at the start of VLC processing, and increases the fuel injection amount when the drop rate of the stack voltage is larger than the predetermined speed. To do.

FIG. 13 is a time chart showing an outline of the progress of VLC processing according to the present embodiment. In the time chart of FIG. 13, for the sake of simplification of the drawing, the stack cooling process other than the VLC process is omitted. For reference, the stack voltage, fuel supply amount, and air supply amount during VLC processing in the fifth embodiment are shown by dotted lines.

As shown in the sections of time t1 to time t1'in FIGS. 13 (b) and 13 (e), in the present embodiment, the stack voltage is set to the same current target value I1 as in the fifth embodiment. Nevertheless, the rate of decrease of the stack voltage is larger than the rate of decrease in the fifth embodiment.

Therefore, in the present embodiment, a larger fuel injection amount is performed at time t1'as compared with the fifth embodiment according to the increase in the decrease rate of the stack voltage (see FIG. 13C). Along with this, the air supply flow rate is also increased as compared with the fifth embodiment (time t1'in FIG. 13 (d)).

As a result, as shown in the section from time t1'to time t2 in FIG. 13B, the increase in the rate of decrease in the stack voltage is alleviated, so that in-plane stabilization caused by the sudden decrease in the stack voltage occurs. Can be more effectively suppressed and the anodic oxidation deterioration due to the VLC treatment can be suppressed more effectively.

According to the control method of the fuel cell system 100 described above, the following effects can be obtained.

In the control method according to the present embodiment, the control unit 80 monitors the stack voltage until the stack voltage drops to a predetermined value, and the drop rate of the stack voltage corresponds to the current target value which is the predetermined drop rate. When the rate of decrease is larger than the rate of decrease, the amount of fuel gas supplied by the fuel supply mechanism 20 is increased.

As a result, it is possible to alleviate the increase in the decrease rate of the stack voltage, alleviate the bias of the power generation distribution in the fuel cell surface due to the sudden decrease in the stack voltage, and suppress the anode stabilization during the VLC process. it can.

In the present embodiment, the stack voltage decrease rate according to the target current value I1 is set as the predetermined decrease rate of the stack voltage as a reference for increasing the fuel gas supply amount, but the stack voltage decrease rate is set according to the target current value I1. A lowering rate larger than or slightly smaller than the lowering rate of the stack voltage may be set.

(7th Embodiment)
Hereinafter, the seventh embodiment will be described. The same elements as those described in the first embodiment are designated by the same reference numerals, and the description thereof will be omitted. In the present embodiment, in the stack cooling process after the VLC process is completed, the air supply flow rate is adjusted according to the rate of decrease in the stack temperature. That is, the cooling rate of the stack temperature is adjusted by adjusting the increase / decrease of the air supply flow rate.

FIG. 14 is a flowchart showing a flow of system stop processing executed in response to the system stop request according to the present embodiment. Further, FIG. 15 is a time chart showing an outline of the progress of the system stop processing according to the present embodiment. Note that the time chart of FIG. 15 shows only changes in the stack temperature, fuel injection amount, and air flow rate for the sake of simplification of the drawings. For reference, the dotted line in FIG. 15A shows the stack temperature change in the first embodiment.

That is, in the present embodiment, it is assumed that the drop in the stack temperature is low during the stack cooling process.

As shown in the figure, in the present embodiment, the processes of steps S110 to S130 are performed in the same manner as in the first embodiment. Then, if it is determined in step S140 that the stack temperature is not equal to or less than the temperature reduction target value of the stack cooling process, the process proceeds to step S710.

Then, in step S710, the control unit 80 determines whether or not the stack temperature decrease rate is equal to or less than a predetermined value. Specifically, the control unit 80 acquires the stack temperature detection value by the stack temperature sensor 83 at predetermined time intervals, and acquires the change in the stack temperature detection value at the predetermined time as the stack temperature decrease rate.

In step S710, the control unit 80 determines whether or not the stack temperature decrease rate is equal to or less than a predetermined value. When it is determined that the stack temperature decrease rate is equal to or less than a predetermined value, the control unit 80 increases the air supply flow rate in step S720 (see time t2'in FIGS. 15 (a) and 15 (d)). After that, the control unit 80 makes a determination in step S140 again. On the other hand, if it is determined in step S710 that the stack temperature decrease rate is not equal to or less than a predetermined value, the control unit 80 makes the determination in step S140 again without increasing the cathode gas supply amount.

According to the control method of the fuel cell system 100 described above, the following effects can be obtained.

In the control method according to the present embodiment, the control unit 80 supplies air to the fuel cell stack 10 after the stack voltage drops to a predetermined value to lower the fuel cell stack 10 to a predetermined temperature as a fuel cell cooling process. In the stack cooling process, the air supply flow rate is adjusted based on the temperature decrease rate of the fuel cell stack 10.

As a result, the air supply flow rate can be suitably adjusted according to the temperature decrease rate (cooling rate) of the fuel cell stack 10 during the stack cooling process. In particular, when the stack temperature decreases slowly during the stack cooling process as in the present embodiment, the stack temperature decrease rate is improved by increasing the air supply amount, and the extension of the stack cooling process is prevented. As a result, the system stop process is prevented from being prolonged.

On the other hand, when the stack temperature decrease rate is relatively fast, the amount of air supplied to the fuel cell stack 10 may be reduced to slow down the cooling rate. As a result, it is possible to prevent damage to the stack due to thermal deformation caused by a difference in the coefficient of linear expansion of the stack components due to a sudden temperature change of the fuel cell stack 10. In particular, in the case of the fuel cell stack 10 which is a solid oxide fuel cell as in the present embodiment, the temperature is increased by cooling from the operating temperature (for example, about 800 ° C.) to the temperature reduction target temperature (for example, about 300 ° C.). As described above, the protective effect of the stack components by slowing the cooling rate becomes more remarkable because of the decrease.

(8th Embodiment)
Hereinafter, the eighth embodiment will be described. The same elements as those described in the first embodiment are designated by the same reference numerals, and the description thereof will be omitted. In this embodiment, in particular, the withdrawal current from the fuel cell stack 10 is adjusted according to the power balance of the fuel cell system 100.

FIG. 16 is a flowchart showing a flow of system stop processing executed in response to the system stop request according to the present embodiment.

As shown in the figure, in the present embodiment, similarly to the first embodiment, when the control unit 80 executes steps S110 and S120 and determines in the step S120 that the stack voltage is not equal to or less than the limit target voltage V1. The process proceeds to step S810.

In step S810, the control unit 80 determines whether or not the SOC of the battery 62 is the maximum (for example, 80%). When the control unit 80 determines that the SOC of the battery 62 is not the maximum, the control unit 80 returns to step S120 and again determines the magnitude of the stack voltage and the limit target value. That is, in this case, power generation (VLC processing) is continued. Therefore, in this case, the control unit 80 determines the target current value I1 in consideration of the load of the air blower 43 and the like and the required power of the battery 62.

On the other hand, when the control unit 80 determines that the SOC of the battery 62 is the maximum, the control unit 80 proceeds to step S820 and supplies electric power (current) to a load other than the battery 62. That is, the target current value I1 is determined in consideration of the required power of the load other than the battery 62.

According to the control method of the fuel cell system 100 described above, the following effects can be obtained.

In the control method according to the present embodiment, the control unit 80 as the current extraction unit adjusts the extraction current from the fuel cell stack 10 according to the power balance of the fuel cell system 100. Specifically, if the SOC of the battery 62 is maximum, the stack current is adjusted according to the required power of the load, and if the SOC of the battery 62 is not the maximum, the stack current is adjusted according to the load and the required power of the battery 62. To do.

As a result, in the fuel cell system 100, the power balance can be suitably adjusted while preventing oxidative deterioration of the anode electrode in the VLC treatment.

Although the embodiments of the present invention have been described above, the above embodiments are only a part of the application examples of the present invention, and the technical scope of the present invention is limited to the specific configuration of the above embodiments. Absent.

Further, each of the above embodiments can be arbitrarily combined.

10 Fuel cell stack 20 Anode gas supply mechanism 21 Fuel supply passage 40 Air supply mechanism 41 Air supply passage 51 Anode off gas discharge passage 52 Cathode off gas discharge passage 60 Power mechanism 61 DCDC converter 62 Battery 63 Drive motor 80 Control unit 81 Current sensor 82 Voltage Sensor 83 Stack temperature sensor 90 Fuel gas pressure sensor 92 Air pressure sensor 100 Fuel cell system

Claims (16)

A solid oxide type fuel cell that generates power by receiving an anode gas and a cathode gas, a current extraction unit that draws current from the fuel cell, and an anode gas supply unit that supplies the anode gas to the fuel cell are provided. It is a control method of the fuel cell system executed by the fuel cell system.
After the request to stop the fuel cell system, the current extraction unit draws current from the fuel cell.
The anode gas supply unit is made to supply the anode gas until the voltage of the fuel cell drops to a predetermined value due to the extraction of the current.
Control method. The method for controlling a fuel cell system according to claim 1.
The amount of the anode gas supplied by the anode gas supply unit is adjusted based on the current taken out from the current extraction unit.
Control method. The method for controlling a fuel cell system according to claim 1 or 2.
The amount of anode gas supplied by the anode gas supply unit is corrected based on the temperature of the fuel cell.
Control method. The method for controlling a fuel cell system according to any one of claims 1 to 3.
The current taken out from the fuel cell by the current take-out unit is reduced according to the elapsed time from the start of the voltage drop of the fuel cell.
Control method. The method for controlling a fuel cell system according to any one of claims 1 to 3.
The supply of anode gas by the anode gas supply unit is controlled according to the state of the fuel cell at the time of the stop request.
Control method. The method for controlling a fuel cell system according to claim 5.
The voltage of the fuel cell is monitored until the voltage of the fuel cell drops to a predetermined value.
When the voltage drop rate of the fuel cell is larger than the predetermined voltage drop rate, the supply amount of the anode gas is increased.
Control method. The method for controlling a fuel cell system according to any one of claims 1 to 3.
The current taken out from the fuel cell by the current take-out unit is adjusted according to the power balance of the fuel cell system.
Control method. The method for controlling a fuel cell system according to any one of claims 1 to 7.
After the voltage of the fuel cell drops to a predetermined value, the shutoff valve provided in the anode off-gas discharge passage of the fuel cell is closed.
Control method. The method for controlling a fuel cell system according to claim 8.
When the temperature of the fuel cell becomes equal to or lower than a predetermined value, the shutoff valve is opened to perform a purge process.
Control method. The method for controlling a fuel cell system according to any one of claims 1 to 9.
Wherein after the fuel battery voltage has dropped to a predetermined value, performs a fuel cell cooling treatment for reducing the fuel cell to a predetermined temperature by supplying the cathode gas to the fuel cell,
In the fuel cell cooling process, a process of adjusting the supply amount of the cathode gas is performed based on the temperature decrease rate of the fuel cell.
Control method. A solid oxide fuel cell that generates electricity by receiving the supply of anode gas and cathode gas,
A current take-out unit that draws current from the fuel cell,
An anode gas supply unit that supplies anode gas to the fuel cell,
A voltage information acquisition unit that acquires the voltage of the fuel cell,
A control unit that controls current extraction by the current extraction unit and supply of anode gas by the anode gas supply unit based on the voltage.
A fuel cell system Ru provided with,
The control unit
After the request to stop the fuel cell system, the current take-out unit is made to take out a predetermined value of current.
The anode gas supply unit is made to supply the anode gas until the voltage of the fuel cell drops to a predetermined value due to the extraction of the current.
Fuel cell system. The fuel cell system according to claim 11.
The control unit
The amount of the anode gas supplied by the anode gas supply unit is adjusted based on the current taken out from the current extraction unit.
Fuel cell system. The fuel cell system according to claim 11 or 12.
The control unit
The amount of anode gas supplied by the anode gas supply unit is corrected based on the temperature of the fuel cell.
Fuel cell system. The fuel cell system according to any one of claims 11 to 13.
The control unit
The current taken out from the fuel cell by the current take-out unit is reduced according to the elapsed time from the start of the voltage drop of the fuel cell.
Fuel cell system. The fuel cell system according to any one of claims 11 to 13.
The control unit
The current taken out from the fuel cell by the current take-out unit is determined according to the state of the fuel cell at the time of the stop request.
Fuel cell system. The fuel cell system according to claim 15.
The control unit
The voltage of the fuel cell is monitored until the voltage of the fuel cell drops to a predetermined value.
When the rate of decrease of the voltage until the voltage of the fuel cell decreases to a predetermined value is larger than the predetermined rate of decrease, the supply amount of the anode gas is increased.
Fuel cell system.

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