JP2004111266A - Fuel cell system - Google Patents

Abstract

A fuel cell stack including a plurality of cells is operated in a favorable power generation state in consideration of the influence of condensed water on a cell voltage.
The fuel cell stack includes a cell voltage sensor for detecting a cell voltage of each cell structure of the fuel cell stack to determine a power generation state of the fuel cell stack. When the cell voltage detected by the cell voltage sensor 15 decreases, the purge valve 14 is opened by the battery system control device 4, and the time when the decreased cell voltage rises to a predetermined value is measured. Is shorter than the predetermined time, it is determined that the fuel cell stack 1 has reached a favorable power generation state.
[Selection diagram] Fig. 1

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a fuel cell system for operating a fuel cell stack including a plurality of cells normally.
[0002]
[Prior art]
2. Description of the Related Art Conventionally, there is known a fuel cell system in which a fuel gas such as hydrogen gas and an oxidizing gas having oxygen are supplied to a fuel cell stack to cause an electrochemical reaction through an electrolyte to directly extract electric energy from between electrodes. Have been.
[0003]
Such a fuel cell system has the advantages of high power generation efficiency and extremely low emission of harmful substances, so that it is not only applied to stationary power generation such as power plants and home generators, but also to vehicles. In recent years, fuel cell vehicles that have been used as a driving source for a vehicle have attracted attention.
[0004]
However, in the conventional fuel cell system, if a large amount of power is generated immediately after startup to supply power to a large load in a short time at the time of startup of the fuel cell stack, the output voltage drops sharply, and Not only does it not function, but also causes problems such as damage to the fuel cell stack and shortened life.
[0005]
As a conventional fuel cell system that solves such a problem, for example, focusing on the temperature of the fuel cell stack at the time of startup, when the fuel cell stack temperature is equal to or lower than a predetermined value, the fuel cell stack is in a warm-up state. Therefore, power was taken out of the secondary battery and supplied to the load. This limits the power generation from the fuel cell stack.
[0006]
[Patent Document 1]
Japanese Patent Laid-Open No. 9-231991
[Problems to be solved by the invention]
In a conventional fuel cell system, in the operation method at the time of startup of the fuel cell stack, it is determined whether or not a favorable power generation state has been reached based on the temperature of the fuel cell stack after startup, and the fuel cell stack temperature is measured. A temperature sensor had to be provided in the fuel cell stack.
[0008]
However, since the fuel cell stack is formed by stacking hundreds of cells, the temperature distribution of each cell is often not uniform. This is because in the process of cooling the fuel cell stack, there is a difference in cooling water temperature between the cooling water inlet and the cooling water outlet of the fuel cell stack, and each cell temperature is different near the cooling water inlet and near the cooling water outlet. by.
[0009]
That is, in order for the fuel cell system to function as a power supply, it is necessary to circulate cooling water in the fuel cell stack. However, since most of the power generation loss of the fuel cell stack takes the form of heat generation, for example, the cooling water inlet And the vicinity of the cooling water outlet, a cell temperature difference always occurs. For these reasons, it is necessary to provide temperature sensors at a plurality of locations in order to grasp the temperature of each cell in the fuel cell stack and determine whether or not a good power generation state has been reached, resulting in an increase in cost. There was a problem.
[0010]
In addition, as a cause of causing a voltage drop of the fuel cell stack when the fuel cell system is started, condensed water blocks a gas flow path of the fuel cell stack. The condensed water in the fuel cell stack is generated not only when the temperature of the fuel cell stack is low, but also when the condensed water is generated in a gas pipe for supplying gas to the fuel cell stack and flows into the fuel cell stack. In this case, there is a problem that the power generation state of the fuel cell stack cannot be determined based on the temperature in the fuel cell stack.
[0011]
Accordingly, the present invention has been proposed in view of the above-described circumstances, and provides a fuel cell system capable of operating a fuel cell stack including a plurality of cells in a favorable power generation state.
[0012]
[Means for Solving the Problems]
The fuel cell system according to the present invention includes a cell voltage sensor that detects a cell voltage of each cell structure of the fuel cell stack in order to determine a power generation state of the fuel cell stack configured by stacking a plurality of cell structures. When the cell voltage detected by the cell voltage sensor decreases, the purge valve is opened by the power generation state determining means, and the time when the decreased cell voltage rises to a predetermined value is measured. The above-described problem is solved by determining that the fuel cell stack has reached a favorable power generation state when the time is shorter than the time.
[0013]
Further, in another fuel cell system according to the present invention, in order to determine the power generation state of a fuel cell stack configured by stacking a plurality of cell structures, the fuel cell stack is arranged at a specific portion where condensed water stays in the fuel cell stack. A cell voltage sensor for detecting a cell voltage of the installed cell structure, wherein the power generation state determining means opens the purge valve when the cell voltage detected by the cell voltage sensor decreases to increase the cell voltage. By calculating the frequency of the cell voltage drop of the cell structure in which the cell voltage drop has occurred, by determining that the fuel cell stack has reached a favorable power generation state when the frequency of the cell voltage drop is lower than a predetermined frequency. The above-mentioned problem is solved.
[0014]
【The invention's effect】
According to the fuel cell system of the present invention, when the cell voltage detected by the cell voltage sensor decreases, the purge valve is opened, and the time when the decreased cell voltage increases and reaches a predetermined value is measured. It is determined that the fuel cell stack has reached a good power generation state when the time is shorter than the predetermined time, so it can be determined whether the purging has eliminated the decrease in cell voltage due to condensed water in the fuel cell stack, The influence of the condensed water in the fuel cell stack on the power generation state can be accurately determined. Therefore, according to this fuel cell system, even when the cell voltage varies due to the influence of the condensed water, the fuel cell stack can be operated in a favorable power generation state.
[0015]
Further, according to another fuel cell system according to the present invention, whether or not the fuel cell stack has reached a favorable power generation state is determined based on the frequency at which the cell voltage of a specific portion where condensed water stays in the fuel cell stack decreases. Therefore, the influence of the condensed water in the fuel cell stack on the cell voltage can be accurately determined. Therefore, according to this fuel cell system, even when the cell voltage varies due to the influence of the condensed water, the fuel cell stack can be operated in a favorable power generation state.
[0016]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, embodiments of the present invention will be described with reference to the drawings.
[0017]
[First Embodiment]
The present invention is applied to, for example, a fuel cell system configured as shown in FIG.
[0018]
[Configuration of fuel cell system]
As shown in FIG. 1, the fuel cell system according to the first embodiment includes a fuel cell stack 1 that generates power by being supplied with a fuel gas and an oxidizing gas. The fuel cell stack 1 has a structure in which a fuel cell structure having an air electrode and a hydrogen electrode opposed to each other with a solid polymer electrolyte membrane interposed therebetween is sandwiched between separators, and a plurality of cell structures are stacked. In this example, a fuel cell system that supplies hydrogen gas as a fuel gas for the fuel cell stack 1 to generate a power generation reaction to the hydrogen electrode 1a and supplies air containing oxygen as an oxidant gas to the air electrode 1b is described. explain.
[0019]
In this fuel cell system, when generating power from the fuel cell stack 1, humidified hydrogen gas is supplied to the hydrogen electrode 1a and humidified air is supplied to the air electrode 1b.
[0020]
After the air is pressurized by the compressor 2 and humidified by the air humidifier 3, the air is supplied to the air electrode 1 b of the fuel cell stack 1. At this time, the fuel cell system controller 4 controls the rotation speed of the compressor motor 5 connected to the compressor 2 and controls the opening of the air pressure regulating valve 6 provided on the air discharge side of the air electrode 1b. To adjust the air flow rate and air pressure supplied to the air electrode 1b.
[0021]
Further, the fuel cell system control device 4 reads the sensor signal from the motor rotation sensor 7 and controls the compressor motor 5 so as to reach the target rotation speed. Further, the fuel cell system controller 4 reads the sensor signal from the air pressure sensor 8 that detects the air pressure supplied from the air humidifier 3 to the air electrode 1b, and sets the air pressure regulating valve 6 so as to reach the target air pressure. Control.
[0022]
The hydrogen stored in the high-pressure hydrogen cylinder 9 is humidified with pure water in a hydrogen humidifier 12 via a hydrogen pressure regulating valve 10 and an ejector pump 11, and then supplied to the hydrogen electrode 1a. Unused hydrogen discharged from the hydrogen electrode 1a is returned to the ejector pump 11 and circulated again to the hydrogen electrode 1a by the ejector pump 11.
[0023]
At this time, the fuel cell system controller 4 controls the opening of the hydrogen pressure regulating valve 10 to adjust the hydrogen pressure supplied to the hydrogen electrode 1a. The fuel cell system controller 4 reads a sensor signal from the hydrogen pressure sensor 13 that detects the hydrogen pressure supplied from the hydrogen humidifier 12 to the hydrogen electrode 1a, and opens the hydrogen pressure regulating valve 10 to the target hydrogen pressure. Control.
[0024]
In this fuel cell system, a hydrogen purge valve 14 is provided on the hydrogen discharge side of the hydrogen electrode 1a. The opening and closing operation of the hydrogen purge valve 14 is controlled by the fuel cell system control device 4 and opens and closes according to the state of the fuel cell stack 1. The fuel cell system controller 4 controls the hydrogen purge valve 14 to prevent, for example, the occurrence of water clogging in the fuel cell stack 1 or the decrease in output or the decrease in power generation efficiency due to air leaking from the air electrode 1b to the hydrogen electrode 1a. In the open state, hydrogen gas is temporarily released from the fuel cell stack 1.
[0025]
Further, the fuel cell system includes a cell voltage sensor 15 for measuring a voltage between electrodes of cells connected in series in the fuel cell stack 1. The cell voltage detected by the cell voltage sensor 15 is read by the fuel cell system controller 4. When the fuel cell system controller 4 detects a decrease in cell voltage, the fuel cell system controller 4 performs a fuel cell stack power generation state determination process described later.
[0026]
Here, the fuel cell stack 1 is formed by stacking hundreds of cell structures, and it is impossible to build the fuel cell without variations in characteristics between cells. Is provided with a cell voltage sensor 15. The cell voltage sensor 15 is normally referred to by the fuel cell system controller 4 when controlling the power generated by the fuel cell stack 1.
[0027]
Although not shown in FIG. 1, an electric load (not shown) controlled by the fuel cell system control device 4 is connected to the fuel cell stack 1 to supply generated electric power to the electric load.
[0028]
[Fuel cell stack power generation state determination process]
Next, a fuel cell stack power generation state determination process for determining the power generation state of the fuel cell stack 1 by the fuel cell system control device 4 in the above-described fuel cell system will be described with reference to FIG.
[0029]
The fuel cell stack power generation state determination process is performed by the fuel cell system control device 4 at, for example, a predetermined time interval. In step S1, the sensor signal from the cell voltage sensor 15 is read, and it is determined that the cell voltage has decreased. In this case, the process proceeds to step S2. Here, the fuel cell system control device 4 checks whether any of the cell voltage values recognized from the sensor signal is lower than a predetermined value (for example, 0.5 V). When it is determined that there is a cell voltage value less than the predetermined value, it is determined that hydrogen gas is not normally supplied to the cell, and flooding in which condensed water stays in the fuel cell stack 1 has occurred, and the process proceeds to step S2. Transition. Here, if the condensed water stays in the gas flow path, the flow rate of the gas supplied to each cell structure is different, the cell voltage is reduced, and the cell voltage varies.
[0030]
In step S2, the hydrogen purge valve 14 is opened by the fuel cell system controller 4, and the process proceeds to step S3. When the hydrogen purge valve 14 is opened, the flow rate of hydrogen in the fuel cell stack 1 increases, and condensed water blocking the hydrogen flow path in the fuel cell stack 1 is discharged out of the fuel cell stack 1.
[0031]
In step S3, the fuel cell system controller 4 starts measuring the time from when the hydrogen purge valve 14 was opened in step S2, and proceeds to step S4.
[0032]
In step S4, it is determined whether or not the cell voltage that has been determined to have decreased in step S1 has been restored by increasing and has reached a cell voltage that can be determined as a normal power generation state. Here, the fuel cell system controller 4 determines whether or not the cell voltage has become equal to or higher than a predetermined value (for example, 0.6 V).
[0033]
When the fuel cell system controller 4 determines that the cell voltage value is not the normal cell voltage value, the time measurement started in step S3 is continued until the cell voltage value becomes the normal cell voltage value. While repeating the determination in step S4, if it is determined that the cell voltage value has become a normal cell voltage value, the process proceeds to step S5.
[0034]
In step S5, the fuel cell system controller 4 closes the hydrogen purge valve 14 opened in step S2, and proceeds to step S6.
[0035]
In step S6, the fuel cell system controller 4 ends the time measurement started in step S3, and proceeds to step S7.
[0036]
In step S7, the fuel cell system controller 4 determines whether or not the time obtained as a result of starting the measurement in step 3 and ending the measurement in step S6 is less than a predetermined time. If it is determined that the measured time is less than the predetermined time, it is determined that the amount of condensed water to be generated is relatively small, and the process proceeds to step S8, where the power generation state of the fuel cell stack 1 is good. It is determined that there is, and the process ends.
[0037]
On the other hand, when the fuel cell system controller 4 determines that the time of the result of the measurement is not shorter than the predetermined time, it is determined that the amount of the condensed water to be generated is relatively large, and the process proceeds to step S9, and the process proceeds to step S9. It is determined that the power generation state of the battery stack 1 is not good, and the process ends.
[0038]
As described above, when it is determined in step S9 that the fuel cell system has not reached a good power generation state, the fuel cell system control device 4 limits the electric load connected to the fuel cell stack 1 and stops the fuel cell system. Control to prevent the fuel cell stack 1 from being damaged or shortening its life. At this time, for example, in the case of a fuel cell vehicle equipped with the fuel cell stack 1, the electric power supplied to an electric load such as a motor for driving the vehicle is controlled by the fuel cell system control device 4 or the like so as to be supplied from the secondary battery. I do.
[0039]
If it is determined in step S9 that the power generation state has not been reached, the fuel cell system control device 4 may increase the gas flow rate supplied to the fuel cell stack 1. At this time, the fuel cell system controller 4 increases the rotation speed of the compressor motor 5 to increase the air flow rate, and controls the hydrogen purge valve 14 to control the fuel cell stack 1 depending on the characteristics of the ejector pump 11. Or the flow rate of hydrogen may be increased by increasing the hydrogen supply pressure to the hydrogen.
[0040]
By changing the operation state of the fuel cell stack 1 in this way, the power supplied to the motor 2 and the like is reduced by the need to supply power to the compressor 2 and the like, and the net efficiency of the fuel cell system is reduced. By increasing the gas flow rate, the condensed water is eliminated to operate the fuel cell stack 1 stably.
[0041]
[Effects of First Embodiment]
As described in detail above, according to the fuel cell system according to the first embodiment, when the cell voltage decreases, the hydrogen purge valve 14 is opened, and after performing the hydrogen purge, the cell voltage increases and the normal state. It is determined whether or not the fuel cell stack 1 after startup has reached a good power generation state according to the time when the cell voltage reaches a proper level, that is, the reactivation speed of the fuel cell stack 1. It is possible to determine whether or not the decrease in cell voltage due to the above has been eliminated, and it is possible to accurately determine the influence of condensed water on the power generation state.
[0042]
Further, according to this fuel cell system, when it is determined that the fuel cell stack 1 has not reached a favorable power generation state, the power generation amount of the fuel cell stack 1 is limited. If the electrode resistance inside the fuel cell stack 1 increases, the amount of heat generated by the electrode resistance can be suppressed, and the system can be stopped, and the fuel cell stack 1 can be prevented from being damaged or having a shortened life.
[0043]
Furthermore, according to the fuel cell system, when it is determined that the fuel cell stack 1 has not reached a favorable power generation state, the flow rates of the hydrogen gas and the air are increased, so that the operation of the fuel cell stack 1 is stabilized. Becomes possible. That is, by increasing the gas flow rate supplied to the fuel cell stack 1, for example, the condensed water inside the fuel cell stack 1 can be taken out while keeping the load taken out of the fuel cell stack 1 constant by a power management system or the like. .
[0044]
[Second embodiment]
Next, a fuel cell system according to a second embodiment will be described. Note that the same parts as those in the above-described first embodiment are denoted by the same reference numerals, and detailed description thereof will be omitted. Further, the schematic configuration of the fuel cell system according to the second embodiment is the same as that of the fuel cell system according to the first embodiment, and a description thereof will be omitted.
[0045]
The fuel cell system according to the second embodiment includes a cell voltage sensor 15 for measuring each cell voltage of the fuel cell stack 1 in a fuel cell stack power generation state determination process, and a cell voltage value based on a sensor signal from the cell voltage sensor 15. When the cell voltage drops, the position of the cell in which the cell voltage drop has occurred in the cell structure is identified, and the power generation state of the fuel cell stack 1 is determined from the frequency at which the specific cell voltage drops. Features.
[0046]
In this fuel cell system, as shown in FIG. 3, a plurality of cell structures (single cells) 21 are folded back and stacked due to layout, and the cell group 31 and the cell group 32 generate hydrogen gas and air. The flow direction is different, and the fuel cell stack 1 having the folded portion 22a in the hydrogen gas or air gas flow path 22 is used. In the case of such a fuel cell stack 1, the gas pipe is bent, and the gas flow path 22 is turned back and supplied to the cell structure 21 again by the separator effect in which the water vapor contained in the gas stays on the side wall of the gas pipe. Condensed water is likely to be generated at the specific portion A. Therefore, the cell voltage sensor 15 detects the cell voltage of the cell structure 21 located near the specific portion A.
[0047]
As another fuel cell stack 1, as shown in FIG. 4, a plurality of cell structures 21 are stacked in the film thickness direction. In some cases, the direction in which the cooling water flows is opposite. In such a fuel cell stack 1, since the cooling water receives the internal heat, the cooling water temperature is lower at the cooling water inlet than at the cooling water outlet. As a result, the gas temperature on the gas outlet side is lower than that on the gas inlet side, and condensed water is likely to be generated in the specific portion B. Therefore, the cell voltage sensor 15 detects the cell voltage of the cell structure 21 located near the specific portion B.
[0048]
As another fuel cell stack 1, as shown in FIG. 5, a plurality of cell structures 21 are stacked in a film thickness direction, and condensed water of a gas supply side pipe flows into an inlet of a gas flow path 22. Likely to happen. Therefore, the cell voltage sensor 15 detects the cell voltage of the cell structure 21 located near the specific portion C.
[0049]
As described above, even within the fuel cell stack 1, there are a plurality of specific portions where condensed water tends to stay, and the cell voltage decreases due to the influence of the condensed water, and the cell voltage varies between the cell structures 21. Occurs.
[0050]
The fuel cell stack power generation state determination processing in consideration of such a variation in cell voltage for each cell structure 21 will be described with reference to the flowchart of FIG. Note that the same processes as those described with reference to FIG. 2 are denoted by the same step numbers, and detailed description thereof is omitted.
[0051]
This fuel cell stack power generation state determination process is not limited to the case where the fuel cell stack 1 as shown in FIGS. 3 to 5 is used, but includes the above-described plurality of specific portions where condensed water is easily generated. A case where the cell voltage of the cell structure 21 is detected will be described.
[0052]
In the fuel cell system control device 4, when it is determined in step S1 that the cell voltage of any of the cell structures 21 has decreased, the process proceeds to step S11, and the fuel cell of the cell structure 21 in which the cell voltage decrease has occurred. The position in the stack 1 is stored, and the hydrogen purge valve 14 is opened in step S2. At this time, the fuel cell system control device 4 distinguishes the sensor signal from the cell voltage sensor 15 that detects the cell voltage of the specific part in FIGS. Identify the location.
[0053]
Then, by performing the processing of step S4 and step S5, it is determined that the cell voltage of the cell structure 21 in which the cell voltage drop is detected in step S1 has been restored, and the step after the hydrogen purge valve 14 is closed is determined. In S12, the fuel cell system controller 4 calculates the frequency at which the cell voltage of the cell structure 21 whose position is stored in step S11 has dropped. That is, from the position stored in step S11, the frequency of occurrence of the cell voltage drop due to the condensed water at the specific portion is calculated.
[0054]
For example, assuming that the processing after step S1 is performed every predetermined time, the number of occurrences of a specific portion A, B, C, or the like in the fuel cell stack 1 among the past ten cell voltage drops is calculated.
[0055]
In the next step S13, the frequency (number of times) calculated in step S12 by the fuel cell system control device 4 is equal to or higher than a predetermined frequency (for example, three times in the case of the number of times), and the specific part stored in step S11 is stored. It is determined whether or not the frequency at which condensed water stays is high.
[0056]
If it is determined that the frequency is not higher than the predetermined frequency (the number of times), it is determined that the cell voltage drop does not concentrate on the predetermined portion and the variation of the cell voltage value in the fuel cell stack 1 is reduced. In S8, it is determined that a good power generation state has been reached. On the other hand, if it is determined that the frequency is larger than the predetermined frequency (number of times), it is determined that the cell voltage drop is concentrated in a specific portion, and the process proceeds to step S9, where a good power generation state has not yet been reached. When it is determined that the fuel cell stack 1 has not been set, the electric load of the fuel cell stack 1 is limited, and the process of increasing the gas supply flow rate to the fuel cell stack 1 is performed as described above.
[0057]
[Effect of Second Embodiment]
As described above in detail, according to the fuel cell system according to the second embodiment, the frequency of the cell voltage at a specific portion where the flooding is likely to occur in the fuel cell stack 1 is reduced. It is determined whether or not the fuel cell stack has reached a favorable power generation state. Therefore, it is possible to prevent erroneous determination of a cell abnormality due to a variation in the cell voltage of the fuel cell stack 1 and determine the influence of condensed water in the fuel cell stack 1 on the cell voltage. can do. Therefore, according to this fuel cell system, even when the cell voltage varies due to the influence of the condensed water, the fuel cell stack 1 can be operated in a favorable power generation state.
[0058]
Further, according to this fuel cell system, as shown in FIG. 3, the fuel cell stack 1 after startup is determined from the frequency at which the cell voltage of the specific portion A where the gas flow path 22 in the fuel cell stack 1 turns back decreases. Since it is determined whether or not a good power generation state has been reached, erroneous determination due to variations in the cell voltage of the fuel cell stack 1 is prevented, and the structure of the gas flow path 22 of the fuel cell stack 1 is taken into consideration, and condensed water is considered. The influence on the cell voltage can be determined more accurately.
[0059]
Further, according to this fuel cell system, as shown in FIG. 4, the fuel cell stack 1 after startup is good due to the frequency of the cell voltage of the specific portion B where the gas temperature in the fuel cell stack 1 decreases. It is determined whether or not the fuel cell stack 1 has reached a proper power generation state, so that erroneous determination due to the variation in cell voltage of the fuel cell stack 1 is prevented, and the cell voltage of the condensed water is considered in consideration of the temperature characteristics of the fuel cell stack 1 due to cooling water. Can be more accurately determined.
[0060]
Furthermore, according to this fuel cell system, as shown in FIG. 5, the frequency of the cell voltage at the specific portion C near the gas inlet of the fuel cell stack 1 decreases, so that the fuel cell stack 1 after startup is good. Since it is configured to determine whether or not the power generation state has been reached, it is possible to prevent erroneous determination due to variations in the cell voltage of the fuel cell stack 1 and to consider the inflow of condensed water from the gas supply side, and The influence of the condensed water in the cell on the cell voltage can be determined more accurately.
[0061]
Note that the above embodiment is an example of the present invention. For this reason, the present invention is not limited to the above-described embodiment, and other than the present embodiment, various modifications may be made according to the design and the like within a range not departing from the technical idea according to the present invention. Can be changed.
[0062]
That is, the above-described fuel cell stack power generation state determination processing is described to be mainly performed when the fuel cell system is started up. However, the present invention is not limited to this, and may be performed every predetermined period when the cell voltage decreases during normal operation. .
[Brief description of the drawings]
FIG. 1 is a block diagram showing a configuration of a fuel cell system to which the present invention is applied.
FIG. 2 is a flowchart showing a processing procedure of a fuel cell stack power generation state determination process by the fuel cell system according to the first embodiment to which the present invention is applied.
FIG. 3 is a diagram showing a case where a cell voltage of a cell structure at a specific portion of a folded portion in a fuel cell stack is measured.
FIG. 4 is a diagram showing a case where a cell voltage of a cell structure at a specific portion near a cooling water outlet in a fuel cell stack is measured.
FIG. 5 is a diagram showing a case where a cell voltage of a cell structure at a specific portion near a gas inlet in a fuel cell stack is measured.
FIG. 6 is a flowchart showing a processing procedure of a fuel cell stack power generation state determination process by the fuel cell system according to the first embodiment to which the present invention is applied.
[Explanation of symbols]
REFERENCE SIGNS LIST 1 fuel cell stack 2 compressor 3 air humidifier 4 fuel cell system controller 5 compressor motor 6 air pressure regulator 7 motor rotation sensor 8 air pressure sensor 9 high-pressure hydrogen cylinder 10 hydrogen pressure regulator 11 ejector pump 12 hydrogen humidifier 13 hydrogen pressure sensor 14 hydrogen purge valve 15 cell voltage sensor 21 cell structure 22 gas flow path 23 cooling water flow path 31, 32 cell group

Claims (7)

A cell structure in which an oxidant electrode and a fuel electrode are opposed to each other with a solid polymer electrolyte membrane interposed therebetween is sandwiched by a separator, and the cell structure is formed by stacking a plurality of the cell structures. An oxidant gas is supplied to the oxidant electrode. A fuel cell stack that is supplied with fuel gas to the fuel electrode to generate power,
A cell voltage sensor for detecting a cell voltage of each cell structure of the fuel cell stack;
A purge valve provided on a fuel gas discharge side of the fuel cell stack, for discharging fuel gas from the fuel cell stack;
When the cell voltage detected by the cell voltage sensor decreases, the purge valve is opened, and the time when the decreased cell voltage increases and reaches a predetermined value is measured, and when the measured time is shorter than the predetermined time, A fuel cell system comprising: a power generation state determination unit configured to determine that the fuel cell stack has reached a favorable power generation state. A cell structure in which an oxidant electrode and a fuel electrode are opposed to each other with a solid polymer electrolyte membrane interposed therebetween is sandwiched by a separator, and the cell structure is formed by stacking a plurality of the cell structures. An oxidant gas is supplied to the oxidant electrode. A fuel cell stack that is supplied with fuel gas to the fuel electrode to generate power,
A cell voltage sensor for detecting a cell voltage of each cell structure in the fuel cell stack;
When the cell voltage is reduced, a cell voltage drop determination storage unit that determines and stores the position in the cell structure of the cell where the voltage drop has occurred,
A purge valve provided on a fuel gas discharge side of the fuel cell stack, for discharging fuel gas from the fuel cell stack;
When the cell voltage detected by the cell voltage sensor decreases, the purge valve is opened to increase the cell voltage, and the frequency of the cell voltage decrease of the cell structure in which the cell voltage has decreased is calculated. A fuel cell system comprising: a power generation state determination unit configured to determine that the fuel cell stack has reached a favorable power generation state when the frequency of voltage drop is lower than a predetermined frequency. The fuel cell system according to claim 2, wherein the specific portion where the condensed water stays in the fuel cell stack is a portion where a gas flow path is turned back in the fuel cell stack. 3. The fuel cell system according to claim 2, wherein the specific portion where the condensed water stays in the fuel cell stack is a portion where the gas temperature decreases in the fuel cell stack. The fuel cell system according to claim 2, wherein the specific portion where the condensed water stays in the fuel cell stack is near a gas inlet of the fuel cell stack. The fuel cell system according to claim 1, further comprising a control unit configured to limit a power generation amount of the fuel cell stack when the power generation state determination unit determines that the fuel cell stack has not reached a favorable power generation state. Item 6. The fuel cell system according to any one of Items 5. 2. The fuel cell system according to claim 1, further comprising a control unit configured to increase a flow rate of gas supplied to the fuel cell stack when the power generation state determination unit determines that the fuel cell stack has not reached a favorable power generation state. The fuel cell system according to claim 5.

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