JP2015185437A - Control device for fuel cell system, and method of controlling the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To perform proper the opening/closing control of a moisture discharge valve with a simple structure.SOLUTION: Fuel gas is supplied to a fuel cell stack 10 by a fuel gas injector 35 disposed in a fuel gas supply path 31. The fuel gas flowing out from the fuel cell stack is returned to the fuel gas supply path through a fuel gas returning passage 36. A gas/liquid separator 37 which separates moisture from the fuel gas to store is disposed in the fuel gas returning passage 36. The fuel gas is intermittently supplied by a fuel gas injector, so that pressure pulsation is generated in a fuel gas channel from the fuel gas injector to the gas/liquid separator through the fuel cell stack. A pressure peak value in the fuel gas channel is detected by the pressure sensor 39, a moisture discharge valve is opened to discharge the stored moisture from the air/liquid separator when the pressure peak value becomes larger than an upper limit value. The moisture discharge valve is closed when the pressure peak value becomes smaller than a lower limit value during the opening of the moisture discharge valve.

Description

  The present invention relates to a control device and a control method for a fuel cell system.

  A fuel cell stack that generates electric power by an electrochemical reaction between the fuel gas and the oxidant gas, a fuel gas supply path connected to an inlet of a fuel gas path formed in the fuel cell stack, and a fuel gas supply path A fuel gas supply device for supplying fuel gas to the fuel cell stack, and a fuel for connecting the outlet of the fuel gas passage and the fuel gas supply passage to return the fuel gas flowing out of the fuel cell stack to the fuel gas supply passage A gas return passage, a gas-liquid separator that is disposed in the fuel gas return passage and separates and stores moisture from the fuel gas, and for discharging moisture stored in the gas-liquid separator from the gas-liquid separator And a water discharge valve disposed in the water discharge passage, wherein the water discharge valve is temporarily opened to discharge water from the gas-liquid separator. Control device It is known.

  When the moisture discharge valve is opened, fuel gas may flow out of the gas-liquid separator together with moisture. For this reason, it is preferable to keep the water discharge valve closed when the amount of water stored in the gas-liquid separator is small, and to open the water discharge valve when the amount of stored water increases. In order to achieve this, it is necessary to accurately know the amount of water stored in the gas-liquid separator. Therefore, a moisture sensor is provided to detect the amount of moisture flowing out of the gas-liquid separator, and the amount of moisture flowing out of the gas-liquid separator when the moisture discharge valve is opened for a very short time is detected by the moisture sensor. A control device for a fuel cell system that estimates the amount of water stored in the gas-liquid separator based on the detected amount of water and determines the opening timing of the water discharge valve based on the estimated amount of stored water Is known (see Patent Document 1).

JP 2008-059933 A

  However, in Patent Document 1, it is necessary to provide a moisture sensor, and it is also necessary to create a map indicating the relationship between the detected moisture content and the moisture content stored in the gas-liquid separator in advance. . That is, there is a possibility that a great deal of cost and labor may be required to perform proper opening / closing control of the moisture discharge valve.

According to one aspect of the present invention, a fuel cell stack that generates electric power by an electrochemical reaction between a fuel gas and an oxidant gas, and a fuel gas supply connected to an inlet of a fuel gas passage formed in the fuel cell stack. A fuel gas supply device that is disposed in the fuel gas supply channel and supplies the fuel gas to the fuel cell stack; and an outlet of the fuel gas channel for returning the fuel gas flowing out of the fuel cell stack to the fuel gas supply channel. A fuel gas return passage that connects the fuel gas supply paths to each other, a gas-liquid separator that is disposed in the fuel gas return passage and separates and stores moisture from the fuel gas, and moisture stored in the gas-liquid separator A water discharge path for discharging gas from the gas-liquid separator, and a water discharge valve disposed in the water discharge path, and the water discharge valve is temporarily opened to discharge water from the gas-liquid separator. Let the fire burn A control device for a battery system, in which a fuel gas supplier intermittently supplies fuel gas, thereby causing pressure pulsation in the fuel gas flow path from the fuel gas supplier to the gas-liquid separator through the fuel cell stack. A pressure sensor that detects the pressure peak value in the fuel gas flow path, and opens the moisture discharge valve when the pressure peak value exceeds a predetermined upper limit value. There is provided a control device for a fuel cell system, which closes a water discharge valve when a pressure peak value becomes smaller than a predetermined lower limit value when the valve is opened.
According to another aspect of the present invention, a fuel cell stack that generates electric power by an electrochemical reaction between a fuel gas and an oxidant gas, and a fuel gas connected to an inlet of a fuel gas passage formed in the fuel cell stack A supply passage, a fuel gas supply device disposed in the fuel gas supply passage, for supplying the fuel gas to the fuel cell stack, and an outlet of the fuel gas passage for returning the fuel gas flowing out of the fuel cell stack to the fuel gas supply passage A fuel gas return passage that connects the fuel gas supply passage to each other, a gas-liquid separator that is disposed in the fuel gas return passage and separates and stores moisture from the fuel gas, and is stored in the gas-liquid separator A moisture discharge passage for discharging moisture from the gas-liquid separator; and a moisture discharge valve disposed in the moisture discharge passage. The moisture discharge valve is temporarily opened to remove moisture from the gas-liquid separator. I tried to drain it, A fuel cell system control method in which a fuel gas supplier intermittently supplies fuel gas, whereby pressure is applied in the fuel gas flow path from the fuel gas supplier through the fuel cell stack to the gas-liquid separator. When the pulsation has occurred and the pressure peak value in the fuel gas flow path detected by the pressure sensor becomes larger than a predetermined upper limit value, the water discharge valve is opened. Provided is a control method for a fuel cell system, which closes a water discharge valve when it becomes smaller than a predetermined lower limit value.

  Appropriate opening / closing control of the moisture discharge valve can be performed with a simple configuration.

1 is an overall view of a fuel cell system. It is a time chart explaining the change of fuel gas pressure. It is a time chart which shows the various fuel gas pressure according to the moisture storage amount in a gas-liquid separator. It is a diagram which shows the relationship between the water storage amount QSW and the pressure peak value PFGP. It is a time chart explaining opening and closing control of a moisture discharge valve. It is a diagram which shows the upper limit value PFGPU and the lower limit value PFGPL. It is a flowchart which shows the routine which performs opening / closing control of a water | moisture-content discharge valve.

  Referring to FIG. 1, the fuel cell system A includes a fuel cell stack 10. The fuel cell stack 10 includes a plurality of fuel cell single cells stacked in the stacking direction. Each single fuel cell includes a membrane electrode assembly 20. The membrane electrode assembly 20 includes a membrane electrolyte, an anode electrode formed on one side of the electrolyte, and a cathode electrode formed on the other side of the electrolyte.

  The anode electrode and the cathode electrode of the single fuel cell are electrically connected in series, and constitute an electrode of the fuel cell stack 10. The electrode of the fuel cell stack 10 is electrically connected to the inverter 12 via the DC / DC converter 11, and the inverter 12 is electrically connected to the motor generator 13. Further, the fuel cell system A includes a capacitor 14, and this capacitor 14 is electrically connected to the above-described inverter 12 via a DC / DC converter 15. The DC / DC converter 11 is for increasing the voltage from the fuel cell stack 10 and sending it to the inverter 12, and the inverter 12 is for converting the direct current from the DC / DC converter 11 or the capacitor 14 into an alternating current. It is. The DC / DC converter 15 is for reducing the voltage from the fuel cell stack 10 or the motor generator 13 to the battery 14 or increasing the voltage from the battery 14 to the motor generator 13. In the fuel cell system A shown in FIG. 1, the battery 14 is composed of a battery.

  Further, in the single fuel cell, a fuel gas flow passage for supplying fuel gas to the anode electrode, an oxidant gas flow passage for supplying oxidant gas to the cathode electrode, and cooling water to the single fuel cell cell. A cooling water flow passage for supply is formed. By connecting the fuel gas flow passage, the oxidant gas flow passage, and the cooling water flow passage of the plurality of fuel cell single cells in series, the fuel cell stack 10 has the fuel gas passage 30, the oxidant gas passage 40, and the cooling. Water passages 50 are respectively formed.

  A fuel gas supply path 31 is connected to the inlet of the fuel gas passage 30, and the fuel gas supply path 31 is connected to a fuel gas source 32. In an embodiment according to the present invention, the fuel gas is formed from hydrogen and the fuel gas source 32 is formed from a hydrogen tank. In the fuel gas supply path 31, the shutoff valve 33, the regulator 34 for adjusting the pressure of the fuel gas in the fuel gas supply path 31, and the fuel gas from the fuel gas source 32 are sequentially supplied to the fuel cell stack 10 from the upstream side. A fuel gas supplier for supplying, for example, a fuel gas injector 35 is arranged. In another embodiment, a plurality of fuel gas injectors are provided, and these fuel gas injectors are arranged in parallel in the fuel gas supply path 31. On the other hand, a fuel gas return passage 36 is connected to the outlet of the fuel gas passage 30, and this fuel gas return passage 36 is connected to a fuel gas supply passage 31 between the regulator 34 and the fuel gas injector 35, for example. In the fuel gas return passage 36, the gas-liquid separator 37 that separates and stores moisture from the fuel gas and the fuel gas return that feeds the fuel gas from the gas-liquid separator 37 into the fuel gas supply path 31 in order from the upstream side. And a pump 38. In another embodiment, the gas-liquid separator 37 is attached to the outlet of the fuel gas passage 30 of the fuel cell stack 10. When the shut-off valve 33 is opened and the fuel gas injector 35 is opened, the fuel gas in the fuel gas source 32 is supplied into the fuel gas passage 30 in the fuel cell stack 10 via the fuel gas supply passage 31. The At this time, surplus fuel gas flowing out from the fuel gas passage 30 flows into the gas-liquid separator 37 through the fuel gas return passage 36. The fuel gas from which moisture or liquid has been separated in the gas-liquid separator 37 is returned to the fuel gas supply path 31 via the fuel gas return path 36. Therefore, a mixture of the fuel gas from the fuel gas source 32 and the fuel gas from the fuel gas return passage 36 is supplied from the fuel gas injector 35 to the fuel cell stack 10.

  In the embodiment shown in FIG. 1, the gas-liquid separator 37 includes a separation chamber 37c. The fuel gas return passage 36 is communicated with the top of the separation chamber 37c. On the other hand, a moisture discharge path 37p is connected to the bottom of the separation chamber 37c, and a moisture discharge valve 37v is disposed in the moisture discharge path 37p. When the fuel gas flowing out from the fuel cell stack 10 flows into the separation chamber 37c, moisture is separated from the fuel gas. The fuel gas from which the moisture has been separated passes through the top of the separation chamber 37 c and is returned to the fuel gas supply path 31 via the fuel gas return path 36. On the other hand, the moisture separated from the fuel gas is stored at the bottom of the separation chamber 37c. In this case, it can be considered that a moisture storage part is formed at the bottom of the separation chamber 37c, and a volume part filled with fuel gas is formed above the moisture storage part. When the water discharge valve 37v is opened, the water stored in the water storage unit 37b is discharged out of the gas-liquid separator 37 through the water discharge path 37p.

  Here, when the flow path of the fuel gas from the fuel gas injector 35 through the fuel cell stack 10 to the gas-liquid separator 37 is referred to as a fuel gas flow path, the fuel gas pressure PFG that is the pressure in the fuel gas flow path is A pressure sensor 39 for detection is attached in the fuel gas flow path. In the fuel cell system A shown in FIG. 1, the pressure sensor 39 is attached to the fuel gas supply path 31 downstream of the fuel gas injector 35. In another embodiment, a pressure sensor 39 is attached to the fuel gas return passage 36 upstream of the gas-liquid separator 37. In yet another embodiment, a pressure sensor 39 is attached to the fuel gas passage 30 in the fuel cell stack 10. Strictly speaking, the pressure in the fuel gas supply passage 31 downstream of the fuel gas injector 35, the pressure in the fuel gas passage 30 in the fuel cell stack 10, and the pressure in the fuel gas return passage 36 upstream of the gas-liquid separator 37 are shown. The pressure may be different from each other.

  An oxidant gas supply path 41 is connected to the inlet of the oxidant gas path 40, and the oxidant gas supply path 41 is connected to an oxidant gas source 42. In an embodiment according to the present invention, the oxidant gas is formed from air and the oxidant gas source 42 is formed from the atmosphere. In the oxidant gas supply path 41, an air cleaner 43, an oxidant gas supplier or compressor 44 that pumps the oxidant gas in order from the upstream side, and the oxidant gas sent from the compressor 44 to the fuel cell stack 10 are cooled. An intercooler 45 is disposed. On the other hand, a cathode off-gas passage 46 is connected to the outlet of the oxidant gas passage 40. When the compressor 44 is driven, the oxidant gas is supplied into the oxidant gas passage 40 in the fuel cell stack 10 via the oxidant gas supply path 41. At this time, the gas flowing out from the oxidant gas passage 40, that is, the cathode offgas, flows into the cathode offgas passage 46. A cathode offgas control valve 47 for controlling the amount of cathode offgas flowing in the cathode offgas passage 46 is disposed in the cathode offgas passage 46.

  Further, referring to FIG. 1, one end of the cooling water circulation path 51 is connected to the inlet of the cooling water passage 50, and the other end of the cooling water circulation path 51 is connected to the outlet of the cooling water circulation path 51. A cooling water pump 52 that pumps cooling water and a radiator 53 are disposed in the cooling water circulation path 51. The cooling water circulation path 51 upstream of the radiator 53 and the cooling water circulation path 51 between the radiator 53 and the cooling water pump 52 are connected to each other by a radiator bypass passage 54. Further, a radiator bypass control valve 55 that controls the amount of cooling water flowing in the radiator bypass passage 54 is provided. In the fuel cell system A shown in FIG. 1, the radiator bypass control valve 55 is formed of a three-way valve and is disposed at the outlet of the radiator bypass passage 54. When the cooling water pump 52 is driven, the cooling water discharged from the cooling water pump 52 flows into the cooling water passage 50 in the fuel cell stack 10 through the cooling water circulation passage 51, and then passes through the cooling water passage 50. The refrigerant flows into the cooling water circulation path 51 and returns to the cooling water pump 52 via the radiator 53 or the radiator bypass passage 54.

  The electronic control unit 60 is composed of a digital computer and includes a ROM (Read Only Memory) 62, a RAM (Random Access Memory) 63, a CPU (Microprocessor) 64, an input port 65 and an output port 66 which are connected to each other by a bidirectional bus 61. It comprises. The output signal of the pressure sensor 39 described above is input to the input port 65 via the corresponding AD converter 67. On the other hand, the output port 66 is connected to the DC / DC converter 11, the inverter 12, the motor generator 13, the DC / DC converter 15, the shutoff valve 33, the regulator 34, the fuel gas injector 35, the moisture discharge valve 37 v through the corresponding drive circuit 68. The fuel gas return pump 38, the compressor 44, the cathode offgas control valve 47, the cooling water pump 52, and the radiator bypass control valve 55 are electrically connected.

When power generation is to be performed in the fuel cell stack 10, the shut-off valve 33 and the fuel gas injector 35 are opened, and fuel gas is supplied to the fuel cell stack 10. Further, the compressor 44 is driven, and the oxidant gas is supplied to the fuel cell stack 10. As a result, an electrochemical reaction (O ₂ + 4H ⁺ + 4e ⁻ → 2H ₂ O) occurs in the fuel cell stack 10 to generate electric energy. The generated electrical energy is sent to the motor generator 13. As a result, the motor generator 13 is operated as an electric motor for driving the vehicle, and the vehicle is driven. On the other hand, for example, when the vehicle is braked, the motor generator 13 operates as a regenerative device, and the electrical energy regenerated at this time is stored in the capacitor 14.

  When the above-described electrochemical reaction occurs in the fuel cell stack 10, moisture is generated at the cathode electrode of the fuel cell stack 10. Part of this water passes through the membrane electrode assembly 20 and reaches the fuel gas passage 30 and flows into the fuel gas return passage 36 together with the fuel gas. If the fuel gas is returned to the fuel gas supply path 31 while containing moisture, the moisture is supplied to the fuel cell stack 10. Therefore, in the fuel cell system A shown in FIG. 1, a gas-liquid separator 37 is provided in the fuel gas return passage 36 in order to separate and remove moisture from the fuel gas flowing out from the fuel cell stack 10. If it does in this way, fuel gas can be used effectively, suppressing a return of moisture to fuel cell stack 10.

  In the embodiment shown in FIG. 1, the fuel gas injector 35 has a fuel gas passage and a valve body. When the valve body opens the fuel gas passage, that is, the fuel gas injector 35 is opened. When the fuel gas is supplied from the fuel gas injector 35 and the valve element blocks the fuel gas passage, that is, when the fuel gas injector 35 is closed, the supply of the fuel gas from the fuel gas injector 35 is stopped.

  In the embodiment shown in FIG. 1, the fuel gas injector 35 is intermittently opened, so that fuel gas is intermittently supplied from the fuel gas injector 35 to the fuel cell stack 10. That is, as shown in FIG. 2, the fuel gas injector 35 is opened for the valve opening time tOP and then closed for the valve closing time tCL, and these are repeated. Note that the amount of fuel gas supplied from the fuel gas injector 35 is changed by changing the ratio of the valve opening time tOP to the constant cycle time tCYC (= tOP / tCYC), that is, the duty ratio.

  In this case, as shown in FIG. 2, when the fuel gas injector 35 is opened, the above-described fuel gas pressure PFG gradually increases. On the other hand, when the fuel gas injector 35 is closed, the fuel gas pressure PFG gradually decreases as the hydrogen gas is consumed in the fuel cell stack 10. Thus, the fuel gas pressure PFG pulsates. In FIG. 2, PFGP represents the peak value of the fuel gas pressure PFG.

  On the other hand, as described above, the fuel gas return passage 36 communicates with the top of the separation chamber 37c of the gas-liquid separator 37, and a constant volume portion is formed at the top of the separation chamber 37c. As a result, the separation chamber 37c acts as a buffer and can suppress pulsation of the fuel gas pressure. In this case, the pressure pulsation suppressing action depends on the amount of water stored in the gas-liquid separator 37. That is, when the amount of water stored in the gas-liquid separator 37 is small, the volume of the volume portion is large, so that the pulsation of the fuel gas pressure PFG is satisfactorily suppressed. Therefore, as shown in FIG. 3A, the pressure peak value PFGP becomes small. Alternatively, the amplitude of the fuel gas pressure PFG becomes small. On the other hand, when the amount of water stored in the gas-liquid separator 37 is large, the volume of the volume portion is small, so that the pulsation PFG of the fuel gas pressure is difficult to be suppressed. Therefore, as shown in FIG. 3B, the pressure peak value PFGP increases. Alternatively, the amplitude of the fuel gas pressure PFG increases.

  FIG. 4 shows the relationship between the water storage amount QSW in the gas-liquid separator 37 and the pressure peak value PFGP. As can be seen from FIG. 4, the pressure peak value PFGP increases as the water storage amount QSW increases. Thus, the pressure peak value PFGP represents the water storage amount QSW.

  As shown in FIG. 4, when the water storage amount QSW is a predetermined lower limit amount QSWL, the pressure peak value PFGP becomes the lower limit value PFGPL, and when the water storage amount QSW is a predetermined upper limit amount QSWL, the pressure peak The value PFGP is the upper limit value PFGPU.

  Therefore, in the fuel cell system A shown in FIG. 1, when the water storage amount QSW is larger than the upper limit amount QSWL, that is, when the pressure peak value PFGP is larger than the upper limit value PFGPU, the water discharge valve 37v is opened. I try to speak. When the water discharge valve 37v is opened, when the water storage amount QSW is smaller than the lower limit amount QSWL, that is, when the pressure peak value PFGP is smaller than the lower limit value PFGPL, the water discharge valve 37v is closed. Like to do.

  That is, as shown in FIG. 5, when the pressure peak value PFGP becomes larger than the upper limit value PFGPU at time t1, the moisture discharge valve 37v is opened. As a result, the water storage amount QSW decreases and the pressure peak value PFGP decreases. Next, when the pressure peak value PFGP becomes smaller than the lower limit value PFGPL at time t2, the moisture discharge valve 37v is closed.

  In this way, the water discharge valve 37v can be opened when the water discharge valve 37v should be opened, and the water discharge valve 37v can be closed when the water discharge valve 37v should be closed. . That is, the opening / closing control of the moisture discharge valve 37v can be appropriately performed.

  Here, the pressure sensor 39 is normally provided in the fuel cell system A. Therefore, in the embodiment shown in FIG. 1, no additional elements are required for the opening / closing control of the moisture discharge valve 37v. That is, appropriate opening / closing control of the moisture discharge valve 37v can be performed with a simple configuration.

  The fuel gas pressure PFG or the pressure peak value PFGP varies according to the amount of fuel gas sent to the fuel cell stack 10, and the amount of fuel gas sent to the fuel cell stack 10 depends on the load of the fuel cell system A or the required power generation amount. Fluctuate. Therefore, in the fuel cell system A shown in FIG. 1, the upper limit value PFGPU and the lower limit value PFGPL described above are set according to the load of the fuel cell system A. That is, the upper limit value PFGPU and the lower limit value PFGPL are stored in advance in the ROM 62 as a function of the load L of the fuel cell system A in the form of a map shown in FIG. In the example of FIG. 6, as the load L increases, the upper limit value PFGPU and the lower limit value PFGPL each increase.

FIG. 7 shows a routine for executing the above-described opening / closing control of the moisture discharge valve 37v. This routine is executed by interruption every predetermined time.
Referring to FIG. 7, in step 100, the pressure peak value PFGP is read. In the subsequent step 101, it is determined whether or not the moisture discharge valve 37v is currently open. When the moisture discharge valve 37v is closed, the routine proceeds to step 102 where the upper limit value PFGPU is calculated using the map of FIG. In the following step 103, it is determined whether or not the pressure peak value PFGP is larger than the upper limit value PFGPU. When PFGP ≦ PFGPU, the processing cycle ends. When PFGP> PFGPU, the routine proceeds from step 103 to step 104, where the moisture discharge valve 37v is opened.

  When the moisture discharge valve 37v is open, the routine proceeds from step 101 to step 105, where the lower limit value PFGPL is calculated using the map of FIG. In the following step 106, it is determined whether or not the pressure peak value PFGP is smaller than the lower limit value PFGPL. When PFGP ≧ PFGPL, the processing cycle is terminated. When PFGP <PFGPL, the routine proceeds from step 106 to step 107, where the water discharge valve 37v is closed.

  In the embodiments according to the present invention described so far, the fuel gas return passage 36 is connected to the fuel gas supply passage 31 upstream of the fuel gas injector 35, and the fuel gas is supplied to the fuel gas supply passage 31 using the fuel gas return pump 38. Returned. In another embodiment, the fuel gas injector 35 is an injector that generates a negative pressure in the negative pressure chamber by injecting fuel gas, and the fuel gas return passage 36 is connected to the negative pressure chamber. As a result, when fuel gas is injected from the fuel gas injector 35, the fuel gas is sucked through the fuel gas return passage 36 and returned to the fuel gas supply path 31. In this case, a fuel gas return pump is not required.

A fuel cell system 10 fuel cell stack 30 fuel gas passage 31 fuel gas supply passage 35 fuel gas injector 36 fuel gas return passage 37 gas-liquid separator 37p moisture discharge passage 37v moisture discharge valve 39 pressure sensor

Claims (2)

A fuel cell stack that generates electric power by an electrochemical reaction between a fuel gas and an oxidant gas;
A fuel gas supply path connected to an inlet of a fuel gas path formed in the fuel cell stack;
A fuel gas supplier that is disposed in the fuel gas supply path and supplies the fuel gas to the fuel cell stack;
A fuel gas return passage connecting the outlet of the fuel gas passage and the fuel gas supply passage to each other to return the fuel gas flowing out of the fuel cell stack to the fuel gas supply passage;
A gas-liquid separator disposed in the fuel gas return passage to separate and store moisture from the fuel gas;
A water discharge passage for discharging water stored in the gas-liquid separator from the gas-liquid separator;
A water discharge valve disposed in the water discharge path;
A control device for a fuel cell system, wherein the water discharge valve is temporarily opened to discharge water from the gas-liquid separator,
When the fuel gas supply device intermittently supplies the fuel gas, pressure pulsation occurs in the fuel gas flow path from the fuel gas supply device to the gas-liquid separator through the fuel cell stack,
A pressure sensor for detecting a pressure peak value in the fuel gas flow path;
When the pressure peak value becomes larger than the predetermined upper limit value, the moisture discharge valve is opened,
Closes the water discharge valve when the pressure peak value becomes smaller than a predetermined lower limit value when the water discharge valve opens.
Control device for fuel cell system. A fuel cell stack that generates electric power by an electrochemical reaction between a fuel gas and an oxidant gas;
A fuel gas supply path connected to an inlet of a fuel gas path formed in the fuel cell stack;
A fuel gas supplier that is disposed in the fuel gas supply path and supplies the fuel gas to the fuel cell stack;
A fuel gas return passage connecting the outlet of the fuel gas passage and the fuel gas supply passage to each other to return the fuel gas flowing out of the fuel cell stack to the fuel gas supply passage;
A gas-liquid separator disposed in the fuel gas return passage to separate and store moisture from the fuel gas;
A water discharge passage for discharging water stored in the gas-liquid separator from the gas-liquid separator;
A water discharge valve disposed in the water discharge path;
A method for controlling the fuel cell system, wherein the water discharge valve is temporarily opened to discharge water from the gas-liquid separator,
When the fuel gas supply device intermittently supplies the fuel gas, pressure pulsation occurs in the fuel gas flow path from the fuel gas supply device to the gas-liquid separator through the fuel cell stack,
When the pressure peak value in the fuel gas flow path detected by the pressure sensor becomes larger than a predetermined upper limit value, the moisture discharge valve is opened,
After that, when the pressure peak value becomes smaller than a predetermined lower limit value, the moisture discharge valve is closed.
Control method of fuel cell system.

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