JP2010262805A - Fuel cell system - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a fuel cell system for removing more certainly an oxidation gas in a fuel cell at a stage of stopping the fuel cell system. <P>SOLUTION: An oxidation gas supply system ASS in the fuel cell system FCS includes a supply passage AS3 to supply the oxidation gas to the fuel cell FC, an exhaust passage AS4 to discharge oxidation off-gas which has passed the fuel cell FC, a compressor AS2 which sends the oxidation gas through the supply passage AS3, a shut-off valve A1 which is installed in the supply passage AS3, and a shut-off valve A2 which is installed in the exhaust passage AS4. After the shut-off valve A2 is closed, the compressor AS2 is reverse-rotated, and the oxidation gas in the fuel cell FC is discharged through the supply passage AS3, the shut-off valve A1 is closed and the compressor AS2 is stopped to stop the system. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to a fuel cell system.

  As one of such fuel cell systems, a system described in Patent Document 1 below has been proposed. The fuel cell system described in Patent Document 1 below provides an oxidizing gas supply channel that supplies an oxidizing gas to the fuel cell, an oxidizing gas discharge channel that discharges the oxidizing off-gas from the fuel cell, and supplies the fuel gas to the fuel cell. A fuel gas supply flow path and a fuel gas discharge flow path for discharging fuel off-gas from the fuel cell are provided. A valve is provided downstream of the junction of the oxidizing gas discharge channel and the fuel gas discharge channel. With this valve closed, the compressor for sending the oxidizing gas to the fuel cell is rotated in reverse to reduce the pressure in the fuel cell to prevent the oxidizing gas from remaining.

JP 2008-34127 A

  In the prior art, since the oxidizing valve is sucked out by closing the valve and rotating the compressor in the reverse direction, the oxidizing gas does not remain in the fuel cell, and has a certain effect on catalyst deterioration. However, the valve is provided downstream of the junction of the oxidizing gas discharge channel and the fuel gas discharge channel, and is an outlet valve when viewed from the fuel cell side. Therefore, even if the valve is closed and the oxidizing gas in the fuel cell is sucked out, there is a possibility that air as the oxidizing gas flows from the oxidizing gas supply channel side, and there is still room for improvement.

  The present invention has been made in view of such problems, and an object thereof is to provide a fuel cell system capable of more reliably removing oxidizing gas in the fuel cell when the fuel cell system is stopped. There is.

  In order to solve the above problems, a fuel cell system according to the present invention includes a fuel cell having a plurality of cells each having an anode and a cathode, a fuel gas supply unit that supplies fuel gas to the anode, and an oxidizing gas that is supplied to the cathode. An oxidizing gas supply unit for supplying the fuel cell system, wherein the oxidizing gas supply unit discharges the oxidizing off gas that has passed through the fuel cell, a supply flow path for supplying the oxidizing gas to the fuel cell, and A flow path, a compressor for sending oxidizing gas through the supply flow path, a first shut-off valve provided in the supply flow path, and a second shut-off valve provided in the discharge flow path, 2 Close the shutoff valve, reversely rotate the compressor, exhaust the oxidizing gas in the fuel cell through the supply flow path, close the first shutoff valve, and stop the compressor. And wherein the stopping the stem.

  In the present invention, the second shut-off valve provided in the discharge flow path for discharging the oxidizing off gas that has passed through the fuel cell is closed and the compressor is rotated in the reverse direction, so that the oxidizing gas can be reliably sucked out from the fuel cell. it can. Then, after the oxidizing gas in the fuel cell is discharged through the supply channel, the shut-off valve is closed and the compressor is stopped, so that the state in which the oxidizing gas is reliably removed from the fuel cell without the reverse flow of the oxidizing gas remains as it is. Can be maintained, and catalyst deterioration can be prevented. In addition, in order to prevent leakage of oxidizing gas from the cathode side to the anode side, it is not necessary to maintain the fuel gas supply pressure at a predetermined pressure in the fuel gas supply unit. The influence on the cell due to the differential pressure can be reduced.

  The fuel cell system according to the present invention further includes a pressure measurement unit that measures the gas pressure on the cathode side of the fuel cell, and the cathode side gas that is measured by the pressure measurement unit after the compressor is rotated in the reverse direction. It is also preferable that the compressor is stopped on condition that the pressure becomes a predetermined threshold pressure. In this preferred embodiment, the compressor is stopped on the condition that the gas pressure on the cathode side of the fuel cell has reached a predetermined threshold pressure, so the threshold pressure is set to the gas pressure in the state where the oxidizing gas is sucked out from the fuel cell. As a result, it is possible to more accurately grasp the state in which the oxidizing gas has been reliably removed from the fuel cell, and the state can be reliably maintained.

  The fuel cell system according to the present invention further includes a voltage measuring unit that measures the voltage of the cell, and after the compressor is rotated in the reverse direction, the voltage of the cell measured by the voltage measuring unit becomes a predetermined threshold voltage. It is also preferable to stop the compressor on the condition. In this preferred embodiment, the compressor is stopped on the condition that the voltage of the cell reaches a predetermined threshold voltage. Therefore, the threshold voltage is set to a voltage in a state where the oxidizing gas is removed from the cathode of the cell and the cell no longer generates power. By setting, it is possible to more accurately grasp the state in which the oxidizing gas has been reliably removed from the fuel cell, and the state can be reliably maintained.

  In the fuel cell system according to the present invention, it is also preferable to stop the system by stopping the compressor even when the first cutoff valve cannot be closed and remains open. In this preferred embodiment, the catalyst deterioration can be suppressed even during a valve opening failure in which the first shutoff valve cannot be closed and remains open.

  ADVANTAGE OF THE INVENTION According to this invention, the fuel cell system which can remove the oxidizing gas in a fuel cell more reliably in the stop stage of a fuel cell system can be provided.

It is a figure which shows the structure of the fuel cell system which is embodiment of this invention. It is a flowchart which shows the stop control flow of the fuel cell system shown in FIG.

  Hereinafter, embodiments of the present invention will be described with reference to the accompanying drawings. In order to facilitate the understanding of the description, the same components are denoted by the same reference numerals as much as possible in the drawings, and redundant descriptions are omitted.

  First, a fuel cell system FCS mounted on a fuel cell vehicle according to an embodiment of the present invention will be described with reference to FIG. FIG. 1 is a diagram showing a system configuration of the fuel cell system FCS.

  The fuel cell system FCS includes a fuel cell FC, an oxidizing gas supply system ASS (oxidizing gas supply unit), a fuel gas supply system FSS (fuel gas supply unit), a power system ES, a cooling system CS, and a controller EC. It has. The fuel cell FC is configured to generate electric power upon receiving a supply of reaction gas (fuel gas, oxidizing gas). The oxidizing gas supply system ASS is a system for supplying air as an oxidizing gas to the fuel cell FC. The fuel gas supply system FSS is a system for supplying hydrogen gas as fuel gas to the fuel cell FC. The power system ES is a system for controlling charge / discharge of power. The cooling system CS is a system for cooling the fuel cell FC. The controller EC is a controller that performs overall control of the entire fuel cell system FCS.

  The fuel cell FC is configured as a solid polymer electrolyte type cell stack in which a large number of cells (a single battery (power generator) including an anode, a cathode, and an electrolyte) are stacked in series. In this embodiment, a membrane electrode assembly having an electrolyte membrane, an anode provided on one surface of the electrolyte membrane, and a cathode provided on the other surface of the electrolyte membrane, and an anode having a fuel flow channel facing the anode A plurality of cells having a side plate and a cathode side plate having an oxidant channel facing the cathode are stacked. In the fuel cell FC, the oxidation reaction of the formula (1) occurs at the anode, and the reduction reaction of the formula (2) occurs at the cathode. The fuel cell FC as a whole undergoes an electromotive reaction of the formula (3).

H ₂ → 2H ⁺ + 2e ⁻ (1)
(1/2) O ₂ + 2H ⁺ + 2e ⁻ → H ₂ O (2)
H ₂ + (1/2) O ₂ → H ₂ O (3)

  The oxidizing gas supply system ASS has an oxidizing gas flow path AS3 (supply flow path) and an oxidizing off gas flow path AS4 (discharge flow path). The oxidizing gas flow path AS3 is a flow path through which oxidizing gas supplied to the cathode of the fuel cell FC flows. The oxidation off gas flow path AS4 is a flow path through which the oxidation off gas discharged from the fuel cell FC flows.

  The oxidizing gas flow path AS3 is provided with an air compressor AS2, a humidifier AS5, a shutoff valve A1 (first shutoff valve), and a pressure sensor S6. The air compressor AS2 is a compressor for taking in the oxidizing gas from the atmosphere via the filter AS1. The humidifier AS5 is a humidifier for humidifying the oxidizing gas pressurized by the air compressor AS2. The shutoff valve A1 is a valve for shutting off the oxidizing gas supply to the fuel cell FC.

  The oxidation off gas flow path AS4 is provided with a cutoff valve A2 (second cutoff valve), a back pressure adjustment valve A3, and a humidifier AS5. The shut-off valve A2 is a valve for shutting off the oxidizing off-gas discharge from the fuel cell FC. The back pressure adjustment valve A3 is a valve for adjusting the oxidizing gas supply pressure. The humidifier AS5 is provided for exchanging moisture between the oxidizing gas (dry gas) and the oxidizing off gas (wet gas).

  The fuel gas supply system FSS has a fuel gas supply source FS1 (gas storage unit), a fuel gas flow path FS3, a circulation flow path FS4, a circulation pump FS5, and an exhaust drainage flow path FS6. The fuel gas channel FS3 is a channel through which the fuel gas supplied from the fuel gas supply source FS1 to the anode of the fuel cell FC flows. The circulation flow path FS4 is a flow path for returning the fuel off-gas discharged from the fuel cell FC to the fuel gas flow path FS3. The circulation pump FS5 is a pump that pressure-feeds the fuel off-gas in the circulation flow path FS4 to the fuel gas flow path FS3. The exhaust drainage channel FS6 is a channel that is branched and connected to the circulation channel FS4.

  The fuel gas supply source FS1 is composed of, for example, a high-pressure hydrogen tank or a hydrogen storage alloy, and stores high-pressure (for example, 35 MPa to 70 MPa) hydrogen gas. In the case of this embodiment, it is comprised by the high pressure hydrogen tank. The fuel gas supply source FS1 includes a reformer that generates a hydrogen-rich reformed gas from a hydrocarbon-based fuel, and a high-pressure gas tank that stores the reformed gas generated by the reformer in a high pressure state. It may be configured. When the shutoff valve H1 is opened, the fuel gas flows out from the fuel gas supply source FS1 to the fuel gas flow path FS3. The fuel gas is decompressed to, for example, about 200 kPa by the regulator H2 and the injector FS2, and supplied to the fuel cell FC.

  The fuel gas flow path FS3 is provided with a cutoff valve H1, a regulator H2, an injector FS2, a cutoff valve H3, and a pressure sensor S4. The shutoff valve H1 is a valve for shutting off or allowing the supply of the fuel gas from the fuel gas supply source FS1. The regulator H2 adjusts the pressure of the fuel gas. The injector FS2 controls the amount of fuel gas supplied to the fuel cell FC. The shutoff valve H3 is a valve for shutting off the fuel gas supply to the fuel cell FC.

  The regulator H2 is a device that regulates the upstream side pressure (primary pressure) to a preset secondary pressure, and includes, for example, a mechanical pressure reducing valve that reduces the primary pressure. The mechanical pressure reducing valve has a housing in which a back pressure chamber and a pressure adjusting chamber are formed with a diaphragm therebetween, and the primary pressure is reduced to a predetermined pressure in the pressure adjusting chamber by the back pressure in the back pressure chamber. It has a configuration for the next pressure. By arranging the regulator H2 on the upstream side of the injector FS2, the upstream pressure of the injector FS2 can be effectively reduced. For this reason, the design freedom of mechanical structure (a valve body, a housing, a flow path, a drive device, etc.) of injector FS2 can be raised. In addition, it is possible to prevent the valve body of the injector FS2 from becoming difficult to move due to an increase in the differential pressure between the upstream pressure and the downstream pressure of the injector FS2.

  The injector FS2 is an electromagnetically driven on-off valve capable of adjusting the gas flow rate and the gas pressure by driving the valve body directly with a predetermined driving cycle with an electromagnetic driving force and separating it from the valve seat. The injector FS2 moves in an axial direction (gas flow direction) with respect to a valve seat having an injection hole for injecting gaseous fuel such as fuel gas, a nozzle body for supplying and guiding the gaseous fuel to the injection hole, and the nozzle body. And a valve body that is stored and held so as to open and close the injection hole.

  The valve body of the injector FS2 is driven by a solenoid that is an electromagnetic drive device, and is configured such that the gas injection time and gas injection timing of the injector FS2 can be controlled by a control signal output from the controller EC. Injector FS2 changes downstream by changing at least one of the opening area (opening) and the opening time of the valve provided in the gas flow path of injector FS2 in order to supply the required gas flow rate downstream. The gas flow rate (or hydrogen molar concentration) supplied to the side is adjusted.

  The circulation flow path FS4 is provided with a shutoff valve H4, and an exhaust / drain flow path FS6 is connected thereto. An exhaust / drain valve H5 is provided in the exhaust / drain flow path FS6. The exhaust / drain valve H5 is a valve for discharging the fuel off-gas containing impurities in the circulation flow path FS4 and moisture to the outside by operating according to a command from the controller EC. By opening the exhaust / drain valve H5, the concentration of impurities in the fuel off-gas in the circulation flow path FS4 is reduced, and the hydrogen concentration in the fuel off-gas circulating in the circulation system can be increased.

  The fuel off-gas discharged through the exhaust / drain valve H5 is mixed with the oxidizing off-gas flowing through the oxidizing off-gas passage AS4 and diluted by a diluter (not shown). The circulation pump FS5 circulates and supplies the fuel off gas in the circulation system to the fuel cell FC by driving the motor.

  The power system ES includes a DC / DC converter ES1, a battery ES2, a traction inverter ES3, a traction motor ES4, and auxiliary machinery ES5. The fuel cell system FCS is configured as a parallel hybrid system in which a DC / DC converter ES1 and a traction inverter ES3 are connected to the fuel cell FC in parallel.

  The DC / DC converter ES1 boosts the DC voltage supplied from the battery ES2 and outputs it to the traction inverter ES3, and the DC power generated by the fuel cell FC or the regenerative power recovered by the traction motor ES4 by regenerative braking. It has a function of stepping down and charging the battery ES2. The charging / discharging of the battery ES2 is controlled by these functions of the DC / DC converter ES1. Further, the operating point (output terminal voltage, output current) of the fuel cell FC is controlled by voltage conversion control by the DC / DC converter ES1. A voltage sensor S1 and a current sensor S2 are attached to the fuel cell FC. The voltage sensor S1 is a sensor for detecting the output terminal voltage of the fuel cell FC. The current sensor S2 is a sensor for detecting the output current of the fuel cell FC.

  The battery ES2 functions as a surplus power storage source, a regenerative energy storage source during regenerative braking, and an energy buffer during load fluctuations associated with acceleration or deceleration of the fuel cell vehicle. As the battery ES2, for example, a secondary battery such as a nickel / cadmium storage battery, a nickel / hydrogen storage battery, or a lithium secondary battery is preferable. An SOC sensor S3 for detecting SOC (State of charge) is attached to the battery ES2.

  The traction inverter ES3 is, for example, a PWM inverter driven by a pulse width modulation method. The traction inverter ES3 converts the DC voltage output from the fuel cell FC or the battery ES2 into a three-phase AC voltage according to a control command from the controller EC, and controls the rotational torque of the traction motor ES4. The traction motor ES4 is a three-phase AC motor, for example, and constitutes a power source of the fuel cell vehicle.

  Auxiliary machinery ES5 includes motors (for example, power sources such as pumps) arranged in each part in the fuel cell system FCS, inverters for driving these motors, and various in-vehicle auxiliary machinery ( For example, an air compressor, an injector, a cooling water circulation pump, a radiator, etc.) are collectively referred to.

  The cooling system CS includes a radiator CS1, a coolant pump CS2, a coolant forward path CS3, and a coolant return path CS4. The radiator CS1 radiates and cools the coolant for cooling the fuel cell FC. The coolant pump CS2 is a pump for circulating the coolant between the fuel cell FC and the radiator CS1. The coolant forward path CS3 is a channel connecting the radiator CS1 and the fuel cell FC, and is provided with a coolant pump CS2. When the coolant pump CS2 is driven, the coolant flows from the radiator CS1 to the fuel cell FC through the coolant forward path CS3. The coolant return path CS4 is a flow path connecting the fuel cell FC and the radiator CS1, and is provided with a water temperature sensor S5. When the coolant pump CS2 is driven, the coolant that has cooled the fuel cell FC returns to the radiator CS1.

  The controller EC is a computer system including a CPU, a ROM, a RAM, and an input / output interface, and controls each part of the fuel cell system FCS. For example, the controller EC starts the operation of the fuel cell system FCS when receiving the start signal IG output from the ignition switch. Thereafter, the controller EC obtains the required power of the entire fuel cell system FCS based on the accelerator opening signal ACC output from the accelerator sensor, the vehicle speed signal VC output from the vehicle speed sensor, and the like. The required power of the entire fuel cell system FCS is the total value of the vehicle travel power and the auxiliary power.

  Here, auxiliary electric power includes electric power consumed by in-vehicle auxiliary equipment (humidifier, air compressor, hydrogen pump, cooling water circulation pump, etc.), and equipment required for vehicle travel (transmission, wheel control device, steering) Power consumed by devices, suspension devices, etc.), power consumed by devices (air conditioners, lighting equipment, audio, etc.) disposed in the passenger space, and the like.

  Then, the controller EC determines the distribution of output power between the fuel cell FC and the battery ES2. The controller EC controls the oxidizing gas supply system ASS and the fuel gas supply system FSS so that the power generation amount of the fuel cell FC matches the target power, and also controls the DC / DC converter ES1 to operate the fuel cell FC. Control points (output terminal voltage, output current). Further, the controller EC outputs, for example, each U-phase, V-phase, and W-phase AC voltage command value to the traction inverter ES3 as a switching command so as to obtain a target torque corresponding to the accelerator opening, Controls the output torque and rotation speed of the motor ES4. Further, the controller EC controls the cooling system CS so that the fuel cell FC has an appropriate temperature.

  A control flow for stopping the above-described fuel cell system FCS from the operating state will be described with reference to FIG. FIG. 2 is a flowchart showing a control flow when the fuel cell system FCS is stopped from the operating state.

  In step S01, the shutoff valve A2 provided in the oxidizing off gas flow path AS4 is closed. By closing the shutoff valve A2 in this way, one of the air inlet / outlet ports as the oxidizing gas is closed with respect to the fuel cell FC.

  In step S02, the air compressor AS2 provided in the oxidizing gas flow path AS3 is reversely rotated. Since the air compressor AS2 is configured to send air to the fuel cell FC when it rotates forward, air can be sucked out of the fuel cell FC by rotating in reverse. Since the shutoff valve A2 has already been closed in step S01, air is reduced from within the fuel cell FC, and this state continues while the air compressor AS2 rotates in the reverse direction.

  In step S03, it is determined whether the air bleeding completion condition for removing air from the fuel cell FC is satisfied. If the air bleed completion condition is not satisfied, the reverse rotation of the air compressor AS2 is involved and the determination in step S03 is repeated. If the air bleeding completion condition is satisfied, the process proceeds to step S04.

  The air bleeding completion condition is a condition that can determine that the air as the oxidizing gas in the fuel cell FC has been discharged. For example, it is also preferable that the air bleeding is completed when the cathode side gas pressure in the fuel cell FC is lowered to a predetermined threshold pressure, and it is determined that the air bleeding completion condition is satisfied. More specifically, when the pressure value measured by the pressure sensor S6 provided in the oxidizing gas flow path AS3 reaches a predetermined pressure threshold, it is determined that the air bleeding completion condition is satisfied.

  In addition, it is also preferable that the air bleeding is completed and the air bleeding completion condition is satisfied because the voltage of the cell in the fuel cell FC has dropped to a predetermined threshold voltage. More specifically, when the output terminal voltage of the fuel cell FC measured by the voltage sensor S1 reaches a predetermined voltage threshold, it is determined that the air bleeding completion condition is satisfied. If the oxidizing gas is exhausted from the fuel cell FC, power generation cannot be performed, so the cell voltage becomes 0V. Although it is assumed that each cell voltage is measured, if power generation is not performed in each cell, the output terminal voltage should be 0 V. Therefore, even if it is determined by the output terminal voltage, it is determined by directly measuring the cell voltage. Is the same. In addition, when measuring each cell voltage individually, it is necessary to provide the voltage sensor for it.

  Further, if the specifications of the fuel cell FC and the air compressor AS2 are determined, it is also preferable to determine that the air bleeding has been completed when a predetermined time has elapsed since the reverse rotation of the air compressor AS2 is started.

  In step S04, the shutoff valve A1 provided in the oxidizing gas flow path AS3 is closed. Since the shutoff valve A2 already provided in the oxidation off gas flow path AS4 is closed, closing the shutoff valve A1 in this way closes both the inlet / outlet of air as the oxidizing gas with respect to the fuel cell FC. As a result, it is possible to reliably prevent air as an oxidizing gas from entering the fuel cell FC, and to prevent catalyst deterioration.

  In step S05, the air compressor AS2 is stopped. In the description of the present embodiment, the operation of closing the shutoff valve A1 and the operation of stopping the air compressor AS2 have been described in different steps, but the two operation timings may be substantially simultaneous.

In the description of the present embodiment, the operation of closing the shutoff valve A2 in step S01 and the operation of reversely rotating the air compressor AS2 in step S02 have been described in separate steps, but these two operation timings are substantially simultaneous. It does n’t matter. Furthermore, considering the power loss of the air compressor AS2, it is also preferable to replace step S01 and step S02 and close the shutoff valve A2 after the air compressor AS2 is rotated in reverse.
In the present embodiment, the shutoff valves A1 and A2 are solenoid valves that are open at the normal position. By using the normally open type solenoid valve in this way, it is possible to prevent the fuel cell system FCS from being disabled during a system component failure. Even if the shutoff valve A1 cannot be closed in step S04, the oxidant gas in the fuel cell FC can be removed by stopping the air compressor AS2 in step S05. can do.

FCS: Fuel cell system FC: Fuel cell ASS: Oxidizing gas supply system AS1: Filter AS2: Air compressor AS3: Oxidizing gas channel AS4: Oxidizing off gas channel AS5: Humidifier A1: Shutoff valve A2: Shutdown valve A3: Back pressure Regulating valve CS: Cooling system CS1: Radiator CS2: Coolant pump CS3: Coolant forward path CS4: Coolant return path FSS: Fuel gas supply system FS1: Fuel gas supply source FS2: Injector FS3: Fuel gas path FS4: Circulation path FS5: Circulation pump FS6: Exhaust drainage flow path H1: Shutoff valve H2: Regulator H3: Shutoff valve H4: Shutoff valve H5: Exhaust drainage valve ES: Power system ES1: DC / DC converter ES2: Battery ES3: Traction inverter ES4: Traction Motor ES5: Auxiliary machinery EC: Controller S1: Voltage sensor S2: Current sensor S3: SOC sensor S4, S6: a pressure sensor S5: the water temperature sensor ACC: accelerator opening signal IG: activation signal VC: vehicle speed signal

Claims (4)

A fuel cell comprising a plurality of cells having an anode and a cathode;
A fuel gas supply unit for supplying fuel gas to the anode;
An oxidizing gas supply unit for supplying an oxidizing gas to the cathode, and a fuel cell system comprising:
The oxidizing gas supply unit includes a supply channel for supplying an oxidizing gas to the fuel cell, a discharge channel for discharging the oxidizing off-gas that has passed through the fuel cell, a compressor for sending the oxidizing gas through the supply channel, A first cutoff valve provided in the supply flow path, and a second cutoff valve provided in the discharge flow path,
The second shut-off valve is closed, the compressor is rotated in the reverse direction, and after the oxidizing gas in the fuel cell is discharged through the supply flow path, the first shut-off valve is closed and the compressor is stopped to stop the system. A fuel cell system. A pressure measuring unit for measuring a gas pressure on the cathode side of the fuel cell;
2. The compressor according to claim 1, wherein the compressor is stopped on the condition that the gas pressure on the cathode side measured by the pressure measuring unit becomes a predetermined threshold pressure after the compressor is rotated in reverse. Fuel cell system. A voltage measuring unit for measuring the voltage of the cell;
2. The fuel cell according to claim 1, wherein after the compressor is rotated in the reverse direction, the compressor is stopped on condition that the voltage of the cell measured by the voltage measuring unit becomes a predetermined threshold voltage. system.   2. The fuel cell system according to claim 1, wherein even when the first shutoff valve cannot be closed and remains open, the compressor is stopped to stop the system. 3.

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