JP2017143041A - Stop control method of fuel cell system - Google Patents

Abstract

PROBLEM TO BE SOLVED: To suppress increase in the inter-electrode pressure difference between the anode passage side and cathode passage side by simple control, and to protect a fuel cell well.SOLUTION: A stop control method of a fuel cell system 10 has a step of detecting fuel gas pressure of the anode passage, when operation stop is requested. When a determination is made that the detected fuel gas pressure is equal to or below a set fuel gas pressure, a fuel cell stack 12 is subjected to power generation stop processing. Meanwhile, when a determination is made that the detected fuel gas pressure is above the set fuel gas pressure, power generation of the fuel cell stack 12 is continued with a current value higher than the current value of power generation stop processing.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a fuel cell that generates electricity by an electrochemical reaction between a fuel gas and an oxidant gas, a fuel gas supply device that supplies the fuel gas to the fuel cell, and an oxidant that supplies the oxidant gas to the fuel cell. The present invention relates to a stop control method for a fuel cell system including a gas supply device.

  For example, a polymer electrolyte fuel cell has an electrolyte membrane / electrode structure (MEA) in which an anode electrode is disposed on one surface of an electrolyte membrane made of a polymer ion exchange membrane and a cathode electrode is disposed on the other surface. It has. The electrolyte membrane / electrode structure is sandwiched between separators to constitute a power generation cell (unit cell). Usually, a predetermined number of power generation cells are stacked, and for example, they are incorporated in a fuel cell vehicle (fuel cell electric vehicle or the like) as an in-vehicle fuel cell stack.

  In this type of fuel cell, when power generation (operation) is stopped, the supply of fuel gas and oxidant gas to the fuel cell is stopped. However, while the fuel gas remains on the anode electrode, The oxidant gas remains. For this reason, there is a problem that the cathode side is held at a high potential during the stoppage of the fuel cell, and the electrode catalyst layer is deteriorated to cause a decrease in the performance of the fuel cell.

  Thus, for example, a fuel cell system disclosed in Patent Document 1 is known. The fuel cell system includes a fuel cell, a hydrogen supply device that supplies hydrogen (fuel gas) to the fuel cell, and an air supply device that supplies air (oxidant gas) to the fuel cell. The air supply device includes an air inlet pipe communicating with the air inlet of the fuel cell and an air outlet pipe communicating with the air outlet of the fuel cell. The air inlet pipe is provided with an air inlet cutoff valve, and the air outlet pipe is provided with an air outlet cutoff valve.

When the fuel cell system is stopped, both the air inlet shut-off valve and the air outlet shut-off valve are closed. Therefore, since the fuel cell is blocked from the outside air, the inflow of air into the fuel cell is restricted. At that time, oxygen-containing air remains in the fuel cell, oxygen in the remaining air reacts with hydrogen remaining in the hydrogen flow path, and the oxygen is consumed and O _2. The lean state is maintained.

JP 2012-094534 A

  In the above-mentioned Patent Document 1, when a stop command for the fuel cell system is issued, the air inlet shut-off valve and the air outlet shut-off valve are both closed, thereby sealing the cathode flow path of the fuel cell. However, when the fuel cell system is operating at a high load before the stop command, the pressure on the cathode flow path side rapidly decreases due to sealing. Accordingly, the pressure difference between the air pressure in the cathode flow path and the hydrogen pressure in the anode flow path increases, and hydrogen consumption due to power generation does not occur, so that the state of excessive pressure difference between the electrodes continues. For this reason, there is a problem that the electrolyte membrane is damaged in particular.

  The present invention solves this type of problem, and it is possible to reliably suppress an increase in the differential pressure between the anode channel side and the cathode channel side with simple control. It is an object of the present invention to provide a stop control method for a fuel cell system that can be protected.

  A fuel cell system to which a stop control method according to the present invention is applied includes a fuel cell, a fuel gas supply device that supplies fuel gas to an anode flow channel, and an oxidant gas supply device that supplies oxidant gas to a cathode flow channel. It is equipped with. The fuel cell includes an electrolyte membrane / electrode structure that sandwiches a solid polymer electrolyte membrane between an anode electrode and a cathode electrode. Then, power is generated by an electrochemical reaction between the fuel gas supplied to the anode electrode via the anode flow path and the oxidant gas supplied to the cathode electrode via the cathode flow path.

  This stop control method includes a step of detecting the fuel gas pressure in the anode flow path when a request for stopping the operation of the fuel cell system is made. When it is determined that the detected fuel gas pressure is equal to or lower than the set fuel gas pressure, the fuel cell system is subjected to power generation stop processing. On the other hand, when it is determined that the detected fuel gas pressure exceeds the set fuel gas pressure, the fuel cell continues to generate power at a current value higher than the current value of the power generation stop process.

  Further, in this stop control method, when the power generation of the fuel cell is continued, the rotation speed of the air pump constituting the oxidant gas supply device can be set higher than the rotation speed corresponding to the current value at the power generation stop process. preferable.

  Further, the oxidant gas supply device preferably includes a bypass flow path for discharging the oxidant gas discharged from the air pump by bypassing the fuel cell. In this case, when the rotational speed of the air pump is set high, it is preferable that a part of the oxidant gas discharged from the air pump is circulated through the bypass flow path.

  Furthermore, in this stop control method, it is preferable to prohibit regeneration when the rotational speed of the air pump is reduced.

  The oxidant gas supply device preferably includes an inlet sealing valve and an outlet sealing valve communicating with the oxidant gas inlet and the oxidant gas outlet of the fuel cell. In this case, when power generation of the fuel cell is continued, when the fuel gas pressure decreases and the inter-electrode differential pressure between the fuel gas pressure and the oxidant gas pressure in the cathode flow path falls within an allowable range, It is preferable to close the stop valve and the outlet sealing valve.

  According to the present invention, when a fuel cell system operation stop request is made, when it is determined that the fuel gas pressure exceeds a set fuel gas pressure that is a reference for performing power generation stop processing, the current value of the power generation stop processing The power generation of the fuel cell is continued at a higher current value. For this reason, the fuel gas remaining in the anode flow path is consumed by power generation together with the oxidant gas, and the fuel gas pressure on the anode flow path side and the oxidant gas pressure on the cathode flow path side are reduced. Therefore, when the cathode flow path is sealed, it is possible to reduce the pressure difference between the oxidant gas pressure on the cathode flow path side and the fuel gas pressure on the anode flow path side.

  As a result, the increase in the differential pressure between the anode channel side and the cathode channel side can be reliably suppressed with simple control. For example, the fuel cell can be well protected by suppressing damage to the electrolyte membrane. It becomes possible to do.

1 is a schematic configuration explanatory diagram of a fuel cell system to which a stop control method according to an embodiment of the present invention is applied. It is a flowchart explaining the said stop control method. It is a time chart explaining the said stop control method. It is operation | movement explanatory drawing at the time of increasing the rotation speed of an air pump in the said stop control method.

  As shown in FIG. 1, a fuel cell system 10 to which a stop control method according to an embodiment of the present invention is applied is mounted on a fuel cell vehicle (not shown) such as a fuel cell electric vehicle, for example.

  The fuel cell system 10 includes a fuel cell stack 12. The fuel cell stack 12 is supplied with a fuel gas supply device 14 for supplying hydrogen gas, for example, hydrogen gas, an oxidant gas supply device 16 for supplying air, for example, an oxidant gas, and a cooling medium. A cooling medium supply device 18 is provided. The fuel cell system 10 further includes a battery 20 that is an energy storage device and a control unit 22 that is a system control device.

  In the fuel cell stack 12, a plurality of power generation cells 24 are stacked in the horizontal direction or the vertical direction. In the power generation cell 24, the electrolyte membrane / electrode structure 26 is sandwiched between the first separator 28 and the second separator 30. The first separator 28 and the second separator 30 are constituted by a metal separator or a carbon separator.

  The electrolyte membrane / electrode structure 26 includes, for example, a solid polymer electrolyte membrane 32 that is a thin film of perfluorosulfonic acid containing moisture, and an anode electrode 34 and a cathode electrode 36 that sandwich the solid polymer electrolyte membrane 32. Is provided. As the solid polymer electrolyte membrane 32, an HC (hydrocarbon) electrolyte is used in addition to the fluorine electrolyte.

  The first separator 28 is provided with a hydrogen gas passage (fuel gas passage) 38 for supplying hydrogen gas to the anode electrode 34 between the electrolyte membrane / electrode structure 26. The second separator 30 is provided with an air flow path 40 for supplying air to the cathode electrode 36 between the electrolyte membrane / electrode structure 26. Between the first separator 28 and the second separator 30 adjacent to each other, a cooling medium flow path 42 is provided for circulating the cooling medium.

  The fuel cell stack 12 is provided with a hydrogen gas inlet 44a, a hydrogen gas outlet 44b, an air inlet 46a, an air outlet 46b, a cooling medium inlet 48a, and a cooling medium outlet 48b. The hydrogen gas inlet 44 a penetrates in the stacking direction of the power generation cells 24 and communicates with the supply side of the hydrogen gas flow path 38. The hydrogen gas outlet 44 b penetrates in the stacking direction of the power generation cells 24 and communicates with the discharge side of the hydrogen gas flow path 38. The hydrogen gas channel 38, the hydrogen gas inlet 44a, and the hydrogen gas outlet 44b constitute an anode channel.

  The air inlet 46 a penetrates in the stacking direction of the power generation cells 24 and communicates with the supply side of the air flow path 40. The air outlet 46 b penetrates in the stacking direction of the power generation cells 24 and communicates with the discharge side of the air flow path 40. The air flow path 40, the air inlet 46a and the air outlet 46b constitute a cathode flow path.

  The cooling medium inlet 48 a penetrates in the stacking direction of the power generation cells 24 and communicates with the supply side of the cooling medium flow path 42. The cooling medium outlet 48 b penetrates in the stacking direction of the power generation cells 24 and communicates with the discharge side of the cooling medium flow path 42.

  The fuel gas supply device 14 includes a hydrogen tank 50 that stores high-pressure hydrogen. The hydrogen tank 50 communicates with a hydrogen gas inlet 44 a of the fuel cell stack 12 via a hydrogen gas supply path (fuel gas supply path) 52. . The hydrogen gas supply path 52 supplies hydrogen gas to the fuel cell stack 12.

  In the hydrogen gas supply path 52, an injector 54 and an ejector 56 are provided in series, and a bypass supply path 58 is connected across the injector 54 and the ejector 56. The bypass supply path 58 is provided with a BP (bypass) injector 60. The BP injector 60 is a sub-injector used for supplying high-concentration hydrogen when the fuel cell stack 12 is started or when high load power generation is required, while the injector 54 is used during normal power generation. It is a main injector used mainly.

  A hydrogen gas discharge path (off-gas pipe) 62 communicates with the hydrogen gas outlet 44 b of the fuel cell stack 12. The hydrogen gas discharge path 62 leads out hydrogen exhaust gas, which is hydrogen gas at least partially used in the anode electrode 34, from the fuel cell stack 12. A gas-liquid separator 64 is connected to the hydrogen gas discharge path 62, and an ejector 56 is connected via a hydrogen circulation channel 66 that branches from the downstream side of the gas-liquid separator 64. A hydrogen pump 68 is provided in the hydrogen circulation channel 66. The hydrogen pump 68 circulates the hydrogen exhaust gas discharged to the hydrogen gas discharge passage 62 through the hydrogen circulation passage 66 to the hydrogen gas supply passage 52 particularly at the time of starting.

  One end of the purge flow path 70 communicates with the downstream of the hydrogen gas discharge path 62, and a purge valve 72 is provided in the middle of the purge flow path 70. One end of a drainage channel 74 for discharging a fluid mainly containing a liquid component is connected to the bottom of the gas-liquid separator 64. A drain valve 76 is disposed along the drainage flow path 74. In order to detect the hydrogen gas pressure in the anode flow path, the fuel gas supply device 14 includes, for example, a pressure sensor 77 located in the vicinity of the hydrogen gas inlet 44 a in the hydrogen gas supply path 52, and the detection by the pressure sensor 77. A signal is sent to the control unit 22.

  The oxidant gas supply device 16 includes an air pump 78 that compresses and supplies air from the atmosphere, and the air pump 78 is disposed in an air supply path (oxidant gas supply path) 80. The air supply path 80 supplies air to the fuel cell stack 12.

  The air supply path 80 is located on the downstream side of the air pump 78 and is provided with a supply-side on-off valve (inlet sealing valve) 82 a and a humidifier 84 and communicates with the air inlet 46 a of the fuel cell stack 12. A bypass supply path 86 is connected to the air supply path 80 across the humidifier 84. An open / close valve 88 is provided in the bypass supply path 86.

  An air discharge path (oxidant gas discharge path) 90 communicates with the air outlet 46 b of the fuel cell stack 12. The air discharge path 90 is provided with a humidifier 84 that exchanges moisture and heat between supply air and discharge air, a discharge-side on-off valve (outlet sealing valve) 82b, and a back pressure valve 92. The air discharge path 90 discharges exhaust air, which is air that is at least partially used by the cathode electrode 36, from the fuel cell stack 12. Downstream of the air discharge path 90, the other end of the purge flow path 70 and the other end of the drain flow path 74 are connected to form a dilution section.

  The air supply path 80 and the air discharge path 90 are located on both the upstream side of the supply side opening / closing valve 82a, the downstream side of the discharge side opening / closing valve 82b, and the downstream side of the back pressure valve 92. Communicate. The bypass flow path 94 is provided with a BP flow rate adjustment valve 96 that adjusts the flow rate of air flowing through the bypass flow path 94. An air circulation passage 98 is in communication with the air supply passage 80 and the air discharge passage 90 on the downstream side of the supply side opening / closing valve 82a and the upstream side of the discharge side opening / closing valve 82b. A circulation pump 100 is disposed in the air circulation channel 98. The circulation pump 100 circulates the exhaust air discharged to the air discharge passage 90 through the air circulation passage 98 to the air supply passage 80.

  The cooling medium supply device 18 includes a cooling medium supply path 102 connected to the cooling medium inlet 48 a of the fuel cell stack 12, and a water pump 104 is disposed in the middle of the cooling medium supply path 102. The cooling medium supply path 102 is connected to a radiator 106, and the radiator 106 is connected to a cooling medium discharge path 108 communicating with the cooling medium outlet 48b.

  The operation of the fuel cell system 10 configured as described above will be described below.

  In the fuel gas supply device 14, hydrogen gas is supplied from the hydrogen tank 50 to the hydrogen gas supply path 52. This hydrogen gas is supplied to the hydrogen gas inlet 44 a of the fuel cell stack 12 through the injector 54 and the ejector 56. The hydrogen gas is introduced into the hydrogen gas flow path 38 from the hydrogen gas inlet 44 a, and is supplied to the anode electrode 34 of the electrolyte membrane / electrode structure 26 by moving along the hydrogen gas flow path 38.

  In the oxidant gas supply device 16, air is sent to the air supply path 80 under the rotating action of the air pump 78. This air is humidified through the humidifier 84 and then supplied to the air inlet 46 a of the fuel cell stack 12. Air is introduced into the air flow path 40 from the air inlet 46 a, and is supplied to the cathode electrode 36 of the electrolyte membrane / electrode structure 26 by moving along the air flow path 40.

  Accordingly, in each electrolyte membrane / electrode structure 26, hydrogen gas supplied to the anode electrode 34 and oxygen in the air supplied to the cathode electrode 36 are consumed by an electrochemical reaction in the electrode catalyst layer to generate power. Is done.

  In the cooling medium supply device 18, a cooling medium such as pure water, ethylene glycol, or oil is supplied from the cooling medium supply path 102 to the cooling medium inlet 48 a of the fuel cell stack 12 under the action of the water pump 104. The cooling medium flows along the cooling medium flow path 42, cools the power generation cell 24, and then is discharged from the cooling medium outlet 48 b to the cooling medium discharge path 108.

  Next, the hydrogen gas partially consumed by being supplied to the anode electrode 34 is discharged from the hydrogen gas outlet 44 b to the hydrogen gas discharge path 62. Hydrogen gas is introduced from the hydrogen gas discharge path 62 to the hydrogen circulation path 66 and is circulated to the hydrogen gas supply path 52 under the suction action of the ejector 56. The hydrogen gas discharged to the hydrogen gas discharge path 62 is discharged (purged) to the outside under the opening action of the purge valve 72 as necessary.

  Similarly, air that is supplied to the cathode electrode 36 and partially consumed is discharged from the air outlet 46 b to the air discharge path 90. The air humidifies new air supplied from the air supply path 80 through the humidifier 84 and is adjusted to the set pressure of the back pressure valve 92 and then discharged to the dilution unit. In addition, the air discharged | emitted by the air exhaust path 90 circulates to the air supply path 80 through the air circulation flow path 98 under the effect | action of the circulation pump 100 as needed.

  Next, a stop control method for the fuel cell system 10 according to the present embodiment will be described below along the flowchart shown in FIG.

  For example, when the ignition switch (IG) is turned off and the operation stop request of the fuel cell system 10 is made (YES in step S1), the process proceeds to step S2, and the hydrogen in the anode channel is passed through the pressure sensor 77. Gas pressure (fuel gas pressure) (anode pressure) is detected. Next, in step S3, the control unit 22 compares the detected hydrogen gas pressure with a set hydrogen gas pressure (set fuel gas pressure). The set hydrogen gas pressure is a reference pressure at which normal power generation stop processing can be performed. When the hydrogen gas pressure exceeds the set hydrogen gas pressure and the process proceeds to the power generation stop process, the pressure difference between the hydrogen gas pressure and the air pressure in the cathode channel is reduced when the cathode channel side is sealed. There is a risk of increasing the number of defects.

  Therefore, when it is determined that the detected hydrogen gas pressure exceeds the set hydrogen gas pressure (YES in step S3), the process proceeds to step S4, and the output current (electric power) from the fuel cell stack 12 is supplied to the battery 20. It is determined whether or not charging is possible. Whether or not the battery 20 can be charged is determined based on the state of charge of the battery 20, for example, the charging rate (SOC) or failure information.

If it is determined that the battery 20 can be charged (YES in step S4), the process proceeds to step S5, where hydrogen consumption power generation processing and battery charging processing are performed. As shown in FIG. 3, in the hydrogen consumption power generation process, the fuel cell stack 12 continues to generate power at a current value higher than the current value of the power generation stop process (O ₂ lean).

  The hydrogen consuming power generation process includes the above-described normal power generation using the hydrogen gas remaining in the anode flow path of the fuel cell stack 12 and the air supplied to the cathode flow path of the fuel cell stack 12 under the rotating action of the air pump 78. The same is done. The rotational speed of the air pump 78 is set lower than the rotational speed during normal power generation and higher than the rotational speed during power generation stop processing, and the generated current is lower than the generated current during normal power generation. The current output from the fuel cell stack 12 is charged in the battery 20, thereby promoting hydrogen consumption.

  Here, when the rotation speed of the air pump 78 is reduced, the regeneration of the air pump 78 is prohibited. During normal power generation, when the rotation speed of the air pump 78 is reduced, the power efficiency is improved by generating regenerative power and charging the battery 20 in the same manner as the motor. On the other hand, in the stop control of the present application, regeneration of the air pump 78 is prohibited so that the SOC of the battery 20 does not increase as much as possible in order to continue power generation for reducing the hydrogen gas pressure.

  By the hydrogen consuming power generation process, the hydrogen gas remaining in the anode flow path of the fuel cell stack 12 is consumed, and the hydrogen gas pressure is reduced. Then, returning to step S3, when it is determined that the detected hydrogen gas pressure is equal to or lower than the set fuel gas pressure (NO in step S3), the process proceeds to step S6, and the power generation stop process is performed.

In the power generation stop process, as shown in FIG. 1, both the supply-side on / off valve 82a and the discharge-side on / off valve 82b are closed, and the cathode flow path of the fuel cell stack 12 is sealed. And the rotation speed of the air pump 78 is set lower than the rotation speed at the time of hydrogen consumption power generation, and the generated current becomes lower than the generation current at the time of hydrogen consumption power generation. Since the amount of hydrogen purged from the anode flow path decreases, the number of revolutions of the air pump 78 is reduced, and the amount of air that dilutes hydrogen is decreased. For this reason, in the fuel cell stack 12, oxygen in the air remaining in the sealed cathode flow path and hydrogen gas remaining in the sealed anode flow path are consumed by the electrochemical reaction. Therefore, in the cathode flow path, oxygen shifts to a lean nitrogen rich, that is, O ₂ lean.

  On the other hand, if it is determined in step S4 that the output current from the fuel cell stack 12 cannot be charged to the battery 20 (NO in step S4), the process proceeds to step S7, where hydrogen consumption power generation processing and air pump rotation speed increase processing are performed. Is carried out. The air pump rotation speed increasing process is a process of increasing the load on the auxiliary machine and consuming the output current from the fuel cell stack 12 by increasing the rotation speed of the air pump 78.

  When the rotation speed of the air pump 78 is increased, the amount of air supplied to the cathode flow path of the fuel cell stack 12 increases. Therefore, as shown in FIG. 4, the amount of air flowing from the air supply path 80 into the bypass flow path 94 is adjusted by controlling the BP flow rate adjusting valve 96. Thereby, the air increased by the increase in the rotation speed of the air pump 78 can bypass the fuel cell stack 12 and flow into the bypass flow path 94.

  In this case, in this embodiment, when the ignition switch (IG) is turned off, if the hydrogen gas pressure in the anode flow path exceeds the set hydrogen gas pressure, the fuel value is higher than the current value of the power generation stop process. The power generation of the battery stack 12 is continued. For this reason, in the hydrogen consuming power generation process, the hydrogen gas remaining in the anode flow path is consumed by power generation together with oxygen in the air, and the hydrogen gas pressure on the anode flow path side and the air pressure on the cathode flow path side are reduced.

  Therefore, as shown in FIG. 3, when the cathode flow path is sealed after shifting to the power generation stop process, the inter-electrode differential pressure between the air pressure on the cathode flow path side and the hydrogen pressure on the anode flow path side is reduced. It becomes possible. Thereby, it is possible to reliably suppress an increase in the differential pressure between the anode channel side and the cathode channel side with simple control. For example, it is possible to suppress damage to the solid polymer electrolyte membrane 32 and to reduce the fuel cell. An effect is obtained that the stack 12 can be well protected.

  Further, if possible, the current output during the hydrogen consumption power generation process can be charged in the battery 20 to increase the load of power generation, and the hydrogen consumption can be increased. On the other hand, the current output during the hydrogen consumption power generation process can be used to increase the rotational speed of the air pump 78, and the hydrogen consumption can be increased by increasing the auxiliary load. For this reason, hydrogen consumption power generation processing is performed quickly and efficiently.

  Furthermore, when the rotation speed of the air pump 78 is increased, the BP flow rate adjusting valve 96 is controlled to adjust the amount of air flowing from the air supply path 80 into the bypass flow path 94. Accordingly, the cathode flow path of the fuel cell stack 12 is not supplied with air more than necessary, and the solid polymer electrolyte membrane 32 constituting the electrolyte membrane / electrode structure 26 is well suppressed from drying. be able to.

DESCRIPTION OF SYMBOLS 10 ... Fuel cell system 12 ... Fuel cell stack 14 ... Fuel gas supply apparatus 16 ... Oxidant gas supply apparatus 18 ... Cooling medium supply apparatus 20 ... Battery 22 ... Control part 24 ... Power generation cell 26 ... Electrolyte membrane and electrode structure 28, DESCRIPTION OF SYMBOLS 30 ... Separator 32 ... Solid polymer electrolyte membrane 34 ... Anode electrode 36 ... Cathode electrode 38 ... Hydrogen gas flow path 40 ... Air flow path 50 ... Hydrogen tank 52 ... Hydrogen gas supply path 78 ... Air pump 80 ... Air supply path 82a ... Supply Side open / close valve 82b ... Discharge side open / close valve 84 ... Humidifier 90 ... Air discharge passage 92 ... Back pressure valve 94 ... Bypass flow passage 96 ... BP flow rate adjustment valve 98 ... Air circulation flow passage 100 ... Circulation pump

Claims (5)

Provided with an electrolyte membrane / electrode structure for sandwiching a solid polymer electrolyte membrane between an anode electrode and a cathode electrode, a fuel gas supplied to the anode electrode via an anode channel, and a cathode channel A fuel cell that generates electricity by an electrochemical reaction with an oxidant gas supplied to the cathode electrode;
A fuel gas supply device for supplying the fuel gas to the anode channel;
An oxidant gas supply device for supplying the oxidant gas to the cathode channel;
A stop control method for a fuel cell system comprising:
A step of detecting a fuel gas pressure in the anode channel when an operation stop request of the fuel cell system is made;
When it is determined that the detected fuel gas pressure is equal to or lower than a set fuel gas pressure, a step of performing a power generation stop process on the fuel cell system;
Continuing the power generation of the fuel cell at a current value higher than the current value of the power generation stop process when it is determined that the detected fuel gas pressure exceeds the set fuel gas pressure;
A stop control method for a fuel cell system, comprising:   2. The stop control method according to claim 1, wherein, when the power generation of the fuel cell is continued, the rotation speed of the air pump constituting the oxidant gas supply device is set to a rotation speed corresponding to a current value during the power generation stop process. A stop control method for a fuel cell system, wherein the stop control method is set higher. 3. The stop control method according to claim 2, wherein the oxidant gas supply device includes a bypass flow path for bypassing the fuel cell and discharging the oxidant gas discharged from the air pump.
A stop control method for a fuel cell system, wherein when the rotation speed of the air pump is set high, a part of the oxidant gas discharged from the air pump is circulated through the bypass passage.   4. The stop control method for a fuel cell system according to claim 2, wherein regeneration is prohibited when the rotational speed of the air pump is reduced. The stop control method according to any one of claims 1 to 4, wherein the oxidant gas supply device includes an inlet sealing valve and an outlet communicating with an oxidant gas inlet and an oxidant gas outlet of the fuel cell. With a sealing valve,
When the power generation of the fuel cell is continued, when the fuel gas pressure decreases and the pressure difference between the fuel gas pressure and the oxidant gas pressure of the cathode flow path falls within an allowable range, A stop control method for a fuel cell system, wherein an inlet sealing valve and the outlet sealing valve are closed.

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