JP2009158165A - Fuel cell system and its control method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a technology to suppress deterioration of a load followability of a fuel cell system. <P>SOLUTION: When detecting that an output voltage of at least one single cell 1 of a fuel cell stack 10 has dropped further than a prescribed threshold value Vt, a voltage recovery processing is carried out in a control part 40. As the voltage recovery processing, concretely, a current limiting treatment (Fig.4(C); time t2 to time t3) to lower an output current of the fuel cell stack 10, and a current recovery treatment (Fig.4(C); time t3 to time t4) to recover the output current lowered by the current limiting treatment are carried out. In the control part 40, the current recovery treatment is controlled so that it is completed in a shorter time than that of the current limiting treatment. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a fuel cell.

  A fuel cell generally has a stack structure in which a plurality of power generators (membrane electrode assemblies) each having an electrolyte membrane sandwiched between electrodes are stacked. Since the fuel cell collects the power generated in each power generator and supplies it to an external load, it is preferable that each power generator can generate power uniformly.

  However, in a fuel cell, the internal resistance of only some of the power generators may increase remarkably, or the reaction gas supply amount of only some of the power generators may be extremely short. In this case, since the output power of the part of the power generators is lower than that of other power generators, the power generation efficiency of the entire fuel cell is reduced. Moreover, if the power generation of the fuel cell is continued in this state, this part of the power generators may be deteriorated.

  Therefore, when such a significant voltage drop is detected in some of the power generators, a control process is known in which the output current value of the entire fuel cell is reduced to recover the output voltage value of the power generator (Patent Document 1). ).

JP 2005-197008 A

  However, since the output current value of the fuel cell is limited during the execution of the control process, the load followability of the fuel cell system that executes the control process decreases. Therefore, for example, in a moving body such as a vehicle equipped with the fuel cell system as a power source, the decrease in load followability has caused the drivability of the moving body to decrease. Such a problem is a problem common to fuel cell systems and devices using a fuel cell as a power source, but it has been the actual situation that no sufficient contrivance has been made so far.

  An object of this invention is to provide the technique which suppresses the fall of the load followability of a fuel cell system.

  SUMMARY An advantage of some aspects of the invention is to solve at least a part of the problems described above, and the invention can be implemented as the following forms or application examples.

Application Example 1 A fuel cell system including a fuel cell and a control unit that controls an output of the fuel cell in response to an output request to the fuel cell system, the control unit including an output of the fuel cell In order to temporarily limit the current value, the current recovery is performed to increase the current value to the required current value after executing a current limiting process for reducing the current value of the fuel cell to be lower than the required current value corresponding to the output request. A fuel cell system that executes a process and completes the current recovery process in a shorter time than the current limiting process.

  According to this fuel cell system, it is possible to recover the reduced power generation performance of the fuel cell by increasing the voltage of the fuel cell by the current limiting process. At this time, the output of the fuel cell can be prevented from suddenly decreasing by executing the current limiting process relatively slowly. In addition, the time period during which the output of the fuel cell is reduced by executing the current recovery process relatively quickly can be shortened. Therefore, it is possible to suppress a decrease in load followability of the fuel cell system.

Application Example 2 The fuel cell system according to Application Example 1, further including a voltage measurement unit that measures the voltage of the fuel cell, wherein the control unit has a measured value of the voltage measurement unit as a first threshold value. A fuel cell system that executes the current limiting process when it becomes smaller, and executes the current recovery process when the measured value becomes larger than a second threshold value.

  According to this fuel cell system, the current limiting process and the current recovery process are executed in a timely manner as necessary, so that it is possible to further suppress a decrease in load followability of the fuel cell system.

[Application Example 3] The fuel cell system according to Application Example 2, wherein the fuel cell includes a plurality of power generation bodies, the voltage measurement unit measures a voltage for each of the plurality of power generation bodies, and the control unit Is configured to execute the current limiting process when at least one measured value of the plurality of power generators is smaller than the first threshold value, and when the measured value is larger than the second threshold value. A fuel cell system that executes the current recovery process.

  According to this fuel cell system, when at least one of the plurality of single cells has a reduced power generation performance, the current limiting process and the current recovery process are executed to recover the power generation performance. Therefore, deterioration of the fuel cell can be suppressed, and a decrease in load followability of the fuel cell system due to deterioration of the fuel cell can be suppressed.

[Application Example 4] The fuel cell system according to any one of Application Example 1 to Application Example 3, and further, an auxiliary device that compensates for an output that is insufficient with respect to the output request when the output of the fuel cell decreases. A fuel cell system including a power source.

  According to this fuel cell system, even if the output of the fuel cell is insufficient in response to a request from an external load, the auxiliary power supply can be compensated for output, so the load followability of the fuel cell system is reduced. Can be suppressed. In addition, since the processing speed of the current recovery process is relatively slower than that of the current limiting process, it is possible to suppress the load followability of the auxiliary power source from being lowered, and to further suppress the load followability of the fuel cell system.

  The present invention can be realized in various forms, for example, in the form of a fuel cell, a fuel cell system including the fuel cell, a vehicle equipped with the fuel cell system, and the like. .

A. Example:
FIG. 1 is a schematic diagram showing the configuration of a fuel cell system as an embodiment of the present invention. The fuel cell system 100 includes a fuel cell stack 10, a hydrogen system 20 and an air system 30 connected to the fuel cell stack 10, and a control unit 40.

  The fuel cell stack 10 is a polymer electrolyte fuel cell that receives supply of hydrogen and oxygen as reaction gases and generates electric power through the electrochemical reaction. The fuel cell stack 10 does not have to be a solid polymer fuel cell, and the present invention can be applied to any of various types of fuel cells.

  The fuel cell stack 10 has a stack structure in which a plurality of single cells 1 including a membrane electrode assembly that is a power generation body in which an electrolyte membrane is sandwiched between electrodes are stacked. The fuel cell stack 10 is provided with a voltage sensor 11 that can measure the potential of each single cell 1.

  The hydrogen system 20 includes a hydrogen tank 21 and a hydrogen supply pipe 22 for storing hydrogen. The hydrogen tank 21 is connected to a hydrogen supply manifold (not shown) of the fuel cell stack 10 by a hydrogen supply pipe 22, whereby the hydrogen system 20 supplies hydrogen to the fuel cell stack 10. The hydrogen supply pipe 22 is provided with a pressure adjusting valve 23 for adjusting the hydrogen pressure and a gas flow meter 24 for measuring the hydrogen flow rate from the upstream side.

  Further, the hydrogen system 20 includes a hydrogen discharge pipe 25 connected to a hydrogen discharge manifold (not shown) of the fuel cell stack 10, and anode exhaust gas containing hydrogen that has not been subjected to an electrochemical reaction. To the outside of the fuel cell stack 10. From the upstream side, the hydrogen discharge pipe 25 is provided with a pressure gauge 26 for measuring the pressure of hydrogen and a hydrogen discharge valve 27 that is an on-off valve for stopping the discharge of the anode exhaust gas as necessary. .

  The air system 30 includes an air compressor 31 and an air supply pipe 32. The air compressor 31 is connected to an air supply manifold (not shown) of the fuel cell stack 10 by an air supply pipe 32, whereby the air system 30 supplies compressed air to the fuel cell stack 10. . The air supply pipe 32 is provided with a pressure adjusting valve 33 for adjusting the pressure of compressed air and a gas flow meter 34 for measuring the flow rate of the compressed air from the upstream side.

  Further, the air system 30 includes an air discharge pipe 35 connected to an air discharge manifold (not shown) of the fuel cell stack 10, and cathode exhaust gas containing oxygen that has not been subjected to an electrochemical reaction. The fuel cell stack 10 is discharged outside. The air discharge pipe 35 is provided with a pressure gauge 36 for measuring the pressure of the cathode exhaust gas.

  For example, when the fuel cell system 100 is mounted on a moving body such as a vehicle, the control unit 40 outputs an output request (“external output request”) to the fuel cell system 100 from an external load corresponding to the opening of the accelerator pedal 50. "). The control unit 40 also receives system status information from various sensors such as the two gas flow meters 24 and 34, the two pressure gauges 26 and 36, and the voltage sensor 11. The controller 40 controls the output of the fuel cell stack 10 by controlling the opening / closing operations of the pressure regulating valves 23 and 33 and the hydrogen discharge valve 27 based on the output request from the outside and the system status information.

  FIG. 2 is a block diagram showing an electrical configuration of the fuel cell system 100. The fuel cell system 100 further includes a secondary battery 60, a DC / DC converter 70, and a DC / AC inverter 80. The fuel cell stack 10 is connected to a DC / AC inverter 80 via a DC power supply line DCL. The secondary battery 60 is connected to the DC power supply line DCL via the DC / DC converter 70. The DC / AC inverter 80 is connected to a motor 90 that is an external load.

  The secondary battery 60 functions as an auxiliary power source of the fuel cell stack 10 and can be constituted by, for example, a chargeable / dischargeable lithium ion battery. The DC / DC converter 70 has a function as a charge / discharge control unit that controls charging / discharging of the secondary battery 60, and variably adjusts the voltage level of the DC power supply line DCL according to an instruction from the control unit 40. When the output of the fuel cell stack 10 is insufficient with respect to the external output request, the DC / DC converter 70 causes the secondary battery 60 to discharge so as to compensate for the shortage.

  The DC / AC inverter 80 converts DC power obtained from the fuel cell stack 10 and the secondary battery 60 into AC power. The motor 90 can be composed of a three-phase motor or the like, and generates a rotational driving force in accordance with AC power from the DC / AC inverter 80. The motor 90 acts as a generator when the rotor is rotated by an external force, and generates AC power (regenerative power). Such regenerative power is converted to DC power by the DC / AC inverter 80 and charged to the secondary battery 60 via the DC / DC converter 70.

  The control unit 40 detects the output power measurement value (power generation state) of the fuel cell stack 10 from the measurement value of the voltage sensor 11 (FIG. 1). Further, the control unit 40 detects the state of charge (SOC) of the secondary battery 60. The control unit 40 sets the output voltage of the DC / DC converter 70 based on these pieces of information, and controls the output power of the fuel cell stack 10 and the secondary battery 60. Further, the control unit 40 controls the frequency of the AC power by the DC / AC inverter 80 to generate a necessary torque for the motor 90 (torque command).

  3A to 3D are explanatory diagrams for explaining control of the fuel cell system 100 during normal operation. Here, “during normal operation” means a state in which each single cell 1 of the fuel cell stack 10 continues power generation without causing a voltage drop in response to an output instruction from the control unit 40.

FIG. 3A is a graph showing a change with time of output power (referred to as “FC required power”) requested by the control unit 40 to the fuel cell stack 10. The graph of FIG. 3A shows that the controller 40 increases the FC required power from W ₀ to W ₁ in accordance with the increase in external output requests at time t ₀ .

  The control unit 40 calculates a current value to be output from the fuel cell stack 10 according to the FC required power based on the WI characteristics of the fuel cell stack 10, and outputs an output voltage according to the current value to the DC / DC converter. 70 (FIG. 2). Further, the control unit 40 controls the supply amount of the reaction gas, the exhaust gas amount, and the like by the pressure adjusting valves 23 and 33 and the hydrogen discharge valve 27 (FIG. 1) so that the fuel cell stack 10 can output the FC required power. .

FIG. 3B is a graph showing the time change of the output voltage in an arbitrary single cell 1 of the fuel cell stack 10 when the FC required power shown in FIG. 3A changes. In the solid line graph G1 of FIG. 3B, the output voltage value for each single cell 1 of the fuel cell stack 10 starts to decrease from the voltage value V _{0 at} time t ₀ , and corresponds to the FC required power at time t ₁ . It shows that the output voltage value V ₁ is reached and then maintained at the voltage value V ₁ . The output voltage of the entire fuel cell stack 10 is the sum of the output voltages of the single cells 1.

FIG. 3C is a graph showing the change over time of the output current of the fuel cell stack 10 when the FC required power shown in FIG. The output current of the fuel cell stack 10 depends on the VI characteristic of the fuel cell stack 10 from the current value I _{0 in} the section from time t ₀ to time t ₁ corresponding to the change in the output voltage shown in FIG. The current value is increased to I ₁ , and then maintained at the current value I ₁ .

FIG. 3D is a graph showing the change over time of the output torque of the motor 90 (FIG. 2) when the output current of the fuel cell stack 10 shown in FIG. 3C changes. The output torque of the motor 90 increases from the torque value T ₀ to the torque value T _{1 in} the section from the time t ₀ to the time t ₁ according to the change in the output current value of the fuel cell stack 10, and then at the torque value T ₁ . Maintained.

  In this normal operation, if the output power of the fuel cell stack 10 is insufficient with respect to the FC required power for some reason, the control unit 40 compensates for the shortage by discharging the secondary battery 60. To do. As a result, the fuel cell system 100 can suppress a decrease in load followability due to insufficient output of the fuel cell stack 10.

  Here, during this normal operation, each single cell 1 outputs the output voltage shown in FIG. However, in the fuel cell stack 10, the output voltage of only some of the single cells 1 may be significantly reduced, for example, it may be reduced to a negative voltage. (Dotted line graph G2 shown in FIG. 3B). This may be due to an insufficient supply amount of the reaction gas to the single cell 1 for some reason, such as a voltage drop due to an increase in internal resistance of the single cell 1 or a blockage of the gas flow path. .

  Thus, if the power generation of the fuel cell stack 10 is continued in a state where the voltages of some of the single cells 1 have been significantly reduced, not only the power generation efficiency of the fuel cell stack 10 as a whole is reduced, The some single cell 1 may deteriorate. Therefore, in this embodiment, the voltage recovery process described below is executed.

  4A to 4D are the same as FIGS. 3A to 3D in the case where a significant voltage drop occurs in a part of the single cells 1 of the fuel cell stack 10 and the voltage recovery process is executed. It is a simple graph. FIG. 4A is a graph showing the time change of the FC required power, which is almost the same as FIG. That is, in the following description, it is assumed that there has been a change in the external output request similar to that during normal operation described above for the fuel cell system 100.

  The graph of FIG. 4B is a single cell 1 (hereinafter referred to as “low voltage cell 1”) that has caused a significant voltage drop for some reason when the FC required power shown in FIG. 4A changes. ) Of the output voltage is shown by a solid line graph G3. In FIG. 4B, the time change of the voltage that the low voltage cell 1 should originally output is indicated by a broken line graph G4.

In the low voltage cell 1, according to the set output voltage to the DC / DC converter 70 by the control unit 40, the output voltage value from the time t ₀ starts to drop, drops after reaching the target voltage value V ₁ to be output I keep doing it. Control unit 40, the output voltage value of the low voltage cell 1 performs the voltage recovery process detects that it has reached a predetermined threshold value V _t. Here, the predetermined threshold value V _t may be about −0.1 V, for example, if the target voltage value V ₁ is about 0.6 V. The predetermined threshold value V _t is preferably set appropriately by experiments or the like.

FIG. 5 is a flowchart showing a processing procedure of voltage recovery processing executed in the fuel cell system 100. In step S10, the control unit 40 sets the output current of the fuel cell stack 10 to a constant ratio (dI ₁ / dt) from time t _{2 when} the output voltage value of the low voltage cell 1 reaches the predetermined threshold value V _t. The output voltage of the DC / DC converter 70 is controlled so as to decrease at the same time. That is, the output current of the fuel cell stack 10 is limited by the control unit 40. Hereinafter, the process of step S10 is referred to as “current limiting process”, and a certain ratio for reducing the output current is referred to as “limit side rate”.

Here, the limit side rate is determined as follows. Control unit 40 determines the maximum current limit amount I _max according to the difference between the output voltage value V _t is the output voltage V ₀ and the threshold of the low voltage cell 1 at time t ₀ the external output request is increased. Control unit 40 may as having a map for setting a maximum current limit amount I _max.

The controller 40 sets the limit side rate so that the current can be reduced by the maximum current limit amount I _max in a predetermined time. Here, the predetermined time is preferably about 0.5 second to about 2 seconds. That is, the limiting rate is preferably set to a value within the range of the following inequality (1).
I _max /0.5≦|dI ₁ / dt | ≦ I _max / 2 (1)
The limiting rate may be determined by another method, but is preferably set at a current decrease rate that can be sufficiently followed by the DC / DC converter 70.

  The reason for limiting the output current by reducing the output current in this way is to restore the power generation capability of the low voltage cell 1 by alleviating the excessive load received by the low voltage cell 1. is there. The control unit 40 may execute a power generation capacity recovery process for recovering the power generation capacity of the low voltage cell 1 together with the current limiting process. As the power generation capacity recovery process, for example, a process for increasing the supply amount of the reactive gas to the fuel cell stack 10 or a process for increasing the gas pressure of the reactive gas may be executed.

FIG. 4C is a graph showing the time change of the output current of the fuel cell stack 10 in the low voltage cell 1. The output current of the fuel cell stack 10 is substantially the same as the change in FIG. 3C until the time t ₂ when the voltage recovery process is started, but is limited after the time t ₂ when the current limit process is started. It is decreasing at the side rate. When the output current of the fuel cell stack 10 is reduced in this way, the output voltage of the fuel cell stack 10 gradually increases according to the IV characteristics of the fuel cell stack 10 (FIG. 4B ) time interval of time t ₂ ~ time t ₃ of).

In step S20 (FIG. 5), the control unit 40 detects that the output voltage of the fuel cell stack 10 is restored again a predetermined threshold V _t, executes the current recovery processing in step S30. Even if the output current of the fuel cell stack 10 decreases to 0 A in the current limiting process, if the output voltage value does not recover to the predetermined threshold V _t , the output current value is maintained at 0 A until recovery. It is good as a thing. Alternatively, the current recovery process may be executed immediately when the output current value decreases to 0A.

In current recovery process, the control unit 40, a time of increasing at a constant rate with respect to time the output current of the fuel cell stack 10 from the time t ₃ when the output voltage value is restored to the threshold V _t (FIG. 4 (C) t ₃ or later). This constant ratio (dI ₂ / dt) is referred to as “return-side rate”.

The controller 40 sets the return-side rate so that its absolute value is larger than the absolute value of the limit-side rate (inequality (2)), and the reason will be described later.
| DI ₂ / dt | ≧ | dI ₁ / dt | (2)

The return side rate is set so that the output current of the fuel cell stack 10 can be returned to the current value I _{1 in a} predetermined time. Here, the predetermined time is preferably about 0.5 second to about 2 seconds, for example. That is, in the current limiting process, when the output power amount of the fuel cell stack 10 is limited by the maximum current limiting amount I _max , it is preferable that the return side rate is set within the following inequality (3).
I _max /0.5≦|dI ₂ / dt | ≦ I _max / 2 (3)

When the output current value of the fuel cell stack 10 recovers to the output current value I ₁ corresponding to the FC required power (time t _{4 in} FIG. 4C), the control unit 40 proceeds to the control process during normal operation. Return (step S40). During the execution of this current recovery process (time t ₃ to time t ₄ ), the fuel cell stack 10 increases the output voltage to the voltage value V _{1 as} the output current increases as the power generation performance recovers (FIG. 4). (B) time t ₃ to time t ₄ ). Thus, by detecting the voltage drop of the low voltage cell 1 and executing the voltage recovery process, it is possible to suppress the deterioration of the fuel cell stack 10 and the power generation performance.

FIG. 4D is a graph showing the change over time of the output torque of the motor 90 (FIG. 2) when the voltage recovery process is performed. The graph of FIG. 4D is almost the same as the graph of FIG. 3D except that the torque change in the time interval from time t ₃ to time t ₄ is different.

By the way, while the voltage recovery process as described above is executed (time t ₂ to time t ₄ ), the output of the fuel cell stack 10 is limited, so that the output torque value decreases to T ₃ at time t ₃ . Thus, there is a torque valley. When the output torque is greatly reduced in the voltage recovery process, the load followability of the fuel cell system 100 is temporarily reduced. This decrease in load followability decreases the responsiveness and operability (also referred to as “drivability”) of the external load connected to the fuel cell system 100, causing discomfort to the operator.

However, in the fuel cell system 100, a decrease in load followability is suppressed by the compensation power from the secondary battery 60. In this embodiment, the absolute value of the return side rate in the current recovery process (step S20 in FIG. 5) is set larger than the absolute value of the limit side rate in the current limit process (step S10) (inequality (2 )). As a result, the time required for the current recovery process (time t ₃ to time t ₄ ) is faster than the current limit process (time t ₂ to time t ₃ ).

  In this way, by making the processing time of the current limiting process relatively long, it is possible to suppress the rapid output decrease of the fuel cell stack 10 and suppress the rapid torque decrease of the output torque of the motor 90. Moreover, since the processing time of the current recovery processing can be shortened by making the processing time of the current recovery processing time relatively short, the processing of the voltage recovery processing by making the processing time of the current limiting processing relatively long An increase in time can be suppressed. Therefore, it is possible to prevent the operator of the external load from feeling uncomfortable (decrease in drivability) by executing the voltage recovery process.

  Furthermore, the follow-up performance of the secondary battery 60 to the output request of the control unit 40 is improved by making the current limiting processing time relatively long. Thereby, since the compensation performance of the secondary battery 60 can be sufficiently exhibited, it is possible to further suppress the load followability of the fuel cell system 100 from being reduced, and to suppress the decrease in drivability of the external load.

  Thus, according to the fuel cell system 100, the voltage recovery process suppresses the deterioration of the fuel cell stack 10, and the voltage recovery process reduces the load followability to the external load of the fuel cell system 100. Can be suppressed. Therefore, it is possible to suppress a decrease in drivability of an external load connected to the fuel cell system 100.

B. Variations:
The present invention is not limited to the above-described examples and embodiments, and can be implemented in various modes without departing from the gist thereof. For example, the following modifications are possible.

B1. Modification 1:
In the above embodiment, in the current limiting process and the current recovery process, the output current is decreased or increased at a constant ratio, but it is not necessary to decrease or increase the output current at a constant ratio. For example, the output current may be decreased or increased exponentially. Even in this case, the current recovery process may be completed in a shorter time than the current limiting process.

B2. Modification 2:
In the above embodiment, when at least one of the output voltage of the single cell 1 of the fuel cell stack 10 starts current restricting process when lower than the predetermined threshold value V _t, recovered again to a predetermined threshold value V _t The current recovery process was started. However, the threshold that is the start condition for the current limiting process and the threshold that is the start condition for the current recovery process may be different values. That is, the current limiting process starts when the output voltage of at least one single cell 1 in the fuel cell stack 10 falls below the first threshold, and the current recovery process starts when the output voltage recovers to the second threshold. It is good to do.

The voltage recovery process may be being performed without performing the occurrence determination of the voltage drop of the single cell 1 according to the threshold V _t. For example, the voltage recovery process may be always executed at a predetermined timing. Further, it may be executed when a sudden external load request is made, or may be executed when a decrease in output of the entire fuel cell stack 10 is detected.

B3. Modification 3:
In the above embodiment, the fuel cell system 100 includes the secondary battery 60, but the secondary battery 60 may not be included. However, by compensating the output of the fuel cell stack 10 by the secondary battery 60, it is possible to further suppress a decrease in load followability of the fuel cell system 100.

Schematic which shows the structure of a fuel cell system. Schematic which shows the electrical structure of a fuel cell system. Explanatory drawing for demonstrating the output control of the fuel cell system at the time of normal driving | operation. Explanatory drawing for demonstrating the output control of a fuel cell system in the case of performing a voltage recovery process. The flowchart which shows the process sequence of a voltage recovery process.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... Single cell, low voltage cell 10 ... Fuel cell 10 ... Fuel cell stack 11 ... Voltage sensor 20 ... Hydrogen system 21 ... Hydrogen tank 22 ... Hydrogen supply piping 23 ... Pressure adjustment valve 24 ... Gas flow meter 25 ... Hydrogen discharge piping 26 ... Pressure gauge 27 ... Hydrogen discharge valve 30 ... Air system 31 ... Air compressor 32 ... Air supply pipe 33 ... Pressure adjustment valve 34 ... Gas flow meter 35 ... Air discharge pipe 36 ... Pressure gauge 40 ... Control unit 50 ... Accelerator pedal 70 ... DC / DC converter 80 ... DC / AC inverter 90 ... motor 100 ... fuel cell system DCL ... DC power supply line

Claims (5)

A fuel cell system,
A fuel cell;
A control unit for controlling the output of the fuel cell in response to an output request for the fuel cell system;
With
The control unit executes a current limiting process for reducing the current value of the fuel cell to be lower than a required current value corresponding to the output request in order to temporarily limit the output of the fuel cell, and then the current value To increase the current to the required current value,
The fuel cell system, wherein the current recovery process is completed in a shorter time than the current limit process. The fuel cell system according to claim 1, further comprising:
A voltage measuring unit for measuring the voltage of the fuel cell;
The control unit executes the current limiting process when the measurement value of the voltage measurement unit becomes smaller than a first threshold value, and the current recovery when the measurement value becomes larger than a second threshold value. A fuel cell system that performs processing. The fuel cell system according to claim 2, wherein
The fuel cell includes a plurality of power generators,
The voltage measuring unit measures a voltage for each of the plurality of power generators,
The control unit executes the current limiting process when at least one measured value of the plurality of power generators becomes smaller than the first threshold, and the measured value becomes larger than the second threshold. A fuel cell system that executes the current recovery process when The fuel cell system according to any one of claims 1 to 3, further comprising:
A fuel cell system comprising an auxiliary power supply that compensates for an output that is insufficient with respect to the output request when the output of the fuel cell decreases. A control method of a fuel cell system that supplies output of a fuel cell in response to an output request,
(A) executing a current limiting process for reducing the current value of the fuel cell to be lower than a required current value corresponding to the output request in order to temporarily limit the output of the fuel cell;
(B) executing a current recovery process for increasing the current value to the required current value;
With
The method of controlling a fuel cell system, wherein the current recovery process is completed in a shorter time than the current limiting process.

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