JP6501563B2 - Polymer electrolyte fuel cell system - Google Patents

Description

  In the present invention, a plurality of cells are formed by sandwiching a solid polymer electrolyte membrane between a fuel electrode and an oxygen electrode, and a cooling water flow path for allowing cooling water to flow, via a conductive porous cooling part. A solid having a fuel cell formed by stacking, a fuel gas supply passage for supplying a fuel gas to the fuel electrode, and a cooling water circulation passage for circulating the cooling water flowing out from the cooling water passage and supplying the cooling water passage. The present invention relates to a polymer fuel cell system.

  A polymer electrolyte fuel cell is configured by laminating a plurality of cells each formed by sandwiching a solid polymer electrolyte membrane between a fuel electrode and an oxygen electrode. When the polymer electrolyte fuel cell is operated for power generation, a fuel gas (hydrogen) is supplied to the fuel electrode, and an oxygen-containing gas is supplied to the oxygen electrode. The oxygen electrode is provided with an oxygen-containing gas flow path through which an oxygen-containing gas flows. The solid polymer electrolyte membrane plays a role of moving hydrogen ions generated at the fuel electrode to the oxygen electrode.

  The solid polymer electrolyte membrane exhibits good hydrogen ion conductivity in a properly wetted state. Therefore, it is necessary to humidify the solid polymer electrolyte membrane in the operation of the solid polymer fuel cell. As a method of humidifying, an external humidifying method of humidifying from the outside of the cell stack and an internal humidifying method to be described next are known.

  In the internal humidification system disclosed in Patent Document 1, a microporous conductor separator having a central passage filled with circulating cooling water is used to supply water to the electrolyte membrane. Excess water generated by the reaction of the fuel cell is sent to the water circulation path by the pressure difference between the cathode side reactant flow area and the cooling water circulation path.

  In Patent Document 2, as a problem of the internal humidification system of Patent Document 1, the amount of water exceeding the above-mentioned ability to remove excess water is locally generated along with the long-time operation and the aged deterioration of the device. It has been pointed out that so-called flooding, in which internal diffusivity is inhibited, and the occurrence of insufficient moisture retention of the electrolyte membrane. When these occur, it is said that the characteristics of the fuel cell deteriorate and the durability is acceleratedly lost.

  In order to solve this, it has been proposed in the device of Patent Document 2 to carry out an operation (adjustment operation) to lower the pressure of the circulating cooling water and to increase the pressure difference between the oxidant electrode and the air electrode and the separator. . It is said that this can eliminate the flooding phenomenon and the insufficient water holding capacity.

Japanese Patent Application Publication No. 11-508726 JP 2008-198496 A

  In the device of Patent Document 2, the adjustment operation described above is performed when the cumulative operation time of the fuel cell exceeds a predetermined time or when the voltage of the fuel cell stack is lowered. However, when the device is configured to perform the adjustment operation based on the accumulated operation time, the operation continues without the adjustment operation being performed when the flooding phenomenon or the water retentivity shortage occurs earlier than the expected time, and the cell (Fuel cell stack) may be degraded. In addition, if the device is configured to perform the adjustment operation when the voltage of the fuel cell stack simply decreases, the adjustment operation is performed during the transition period of the output fluctuation even if the adjustment operation is not yet required. In the meantime, power generation is not performed, and the operating efficiency of the fuel cell is unnecessarily lowered.

  The present invention has been made in view of the above-described problems, and an object thereof is to provide a polymer electrolyte fuel cell system in which the operation efficiency is enhanced while suppressing the deterioration of the cells.

In order to achieve the above object, the characterizing feature of the polymer electrolyte fuel cell system according to the present invention is to provide a cooling water for circulating a cell constituted by sandwiching a polymer electrolyte membrane between a fuel electrode and an oxygen electrode. A fuel cell having a water flow path, a plurality of fuel cells formed by laminating a plurality of layers through a conductive porous cooling portion, a fuel gas supply path for supplying a fuel gas to the fuel electrode, and cooling water flowing out of the cooling water flow path A cooling water circulation passage that circulates and supplies the cooling water passage to the cooling water passage;
Adjustment to adjust the pressure difference between the pressure of the fuel gas in the fuel gas supply passage and the pressure of the cooling water in the cooling water passage by controlling at least one of the pressure adjusting valve and the pump provided in the cooling water circulation passage An operation control unit that performs an operation;
Possess an operation determination unit that determines whether or not to perform the adjustment operation based on the voltage drop rate is decreasing rate with respect to time of the output voltage of the fuel cell,
The operation control unit
If the operation determining unit determines that the adjustment operation is to be performed, the output instruction value which is an instruction value of the output to the fuel cell is referred to, and an output instruction value confirmation period previously set based on the determined time is made earlier. If the change range of the output instruction value in the period from the time point of time to the determined time point is larger than the preset output instruction fluctuation threshold value, the adjustment operation is performed regardless of the determination by the operation determination unit There is no point.

According to the above feature configuration, at least one of the pressure control valve and the pump provided in the cooling water circulation path is controlled to control the pressure of the fuel gas in the fuel gas supply path and the pressure of the cooling water in the cooling water flow path. The fuel cell has an operation control unit that performs adjustment operation to adjust the difference, and an operation determination unit that determines whether to perform the adjustment operation based on a voltage decrease rate that is a decrease rate to the time of the output voltage of the fuel cell. The adjustment operation can be performed based on the actual state of the battery, and cell deterioration can be suppressed. In addition, since the adjustment operation is performed based on the voltage drop rate, which is a decrease rate of the output voltage with respect to time, not just the output voltage value, the adjustment operation can be performed at an appropriate timing, and It can be enhanced.
In addition, for a while after the output command value is changed, the output voltage of the fuel cell is likely to largely fluctuate. Then, although the flooding phenomenon and the water retentivity shortage do not actually occur, it may be determined by the operation determination unit to perform the adjustment operation. According to the above feature configuration, the operation control unit refers to the output indication value which is the indication value of the output to the fuel cell, and outputs in the period from the time point before the present to the present by the preset output indication value confirmation period If the change width of the instruction value is larger than the preset output instruction fluctuation threshold, the adjustment operation is not performed regardless of the determination by the operation determination unit, and therefore the output voltage of the fuel cell caused by the change of the output instruction value It is possible to avoid performing the adjustment operation when a drop occurs, and to further enhance the operation efficiency of the polymer electrolyte fuel cell system.

  Another feature of the polymer electrolyte fuel cell system according to the present invention is that the operation determining unit determines that the adjusting operation is necessary when the voltage reduction rate exceeds a preset reduction rate threshold. The point is to

  According to the above-described feature configuration, the operation determining unit determines that the adjustment operation is necessary when the voltage reduction rate exceeds the preset reduction rate threshold, and hence the adjustment operation when the voltage reduction rate is small. The operation efficiency can be improved by not performing the adjustment operation, and the adjustment operation can be performed when the voltage drop rate is large, so that the flooding phenomenon and the water retention shortage can be appropriately eliminated. Therefore, the operating efficiency of the polymer electrolyte fuel cell system can be further enhanced.

  Another feature of the polymer electrolyte fuel cell system according to the present invention is that the operation determining unit is configured such that a state in which the voltage drop rate exceeds a preset drop rate threshold is a preset drop continuation time threshold. The point is to decide that the adjustment operation is necessary when continuing beyond.

  According to the above feature configuration, the operation determining unit needs the adjustment operation when the state in which the voltage drop rate exceeds the preset drop rate threshold continues beyond the preset drop continuation time threshold. Therefore, it is possible to execute the adjustment operation at an appropriate timing. That is, it can be inferred that the possibility of the occurrence of the flooding phenomenon and the insufficient water retentivity is very high if the state of low voltage drop rate continues for a long time, so solid compared to the case where the adjustment operation is performed based on the output voltage alone. The operation efficiency of the polymer fuel cell system can be further enhanced.

  Another feature of the polymer electrolyte fuel cell system according to the present invention is that, in the case where the elapsed time from the previous adjustment operation does not exceed the adjustment operation prohibition time set in advance, the operation control unit The adjustment operation is not performed regardless of the determination by the operation determination unit.

  For a while after the adjustment operation is performed once, the possibility of the occurrence of the flooding phenomenon and the water retentivity becomes low. According to the above feature configuration, when the elapsed time from the previous adjustment operation does not exceed the adjustment operation prohibition time set in advance, the operation control unit performs the adjustment operation regardless of the determination by the operation determination unit. Since it is not, it is possible to avoid performing the adjustment operation in a period in which the possibility of occurrence of the flooding phenomenon and the insufficient water retention ability can be avoided, and the operation efficiency of the polymer electrolyte fuel cell system can be further enhanced.

Schematic diagram showing the configuration of a polymer electrolyte fuel cell Flow chart showing adjustment operation control according to the first embodiment Flow chart showing adjustment operation control according to the second embodiment Explanation of adjustment operation control

First Embodiment
The configuration and operation of the fuel cell system according to the first embodiment will be described below with reference to the drawings. The fuel cell system comprises a polymer electrolyte fuel cell FC (hereinafter simply referred to as "fuel cell FC"). The fuel cell FC has a cooling water flow path that allows the cooling water to flow through the cell C configured by sandwiching the solid polymer electrolyte membrane 4 between the fuel electrode 3 and the oxygen electrode 5, and is a conductive porous cooling portion A plurality of layers are stacked via six. In FIG. 1, only a single cell C is shown for simplification. Fuel gas (hydrogen) is supplied to the fuel electrode 3, and oxygen-containing gas (air) is supplied to the oxygen electrode 5, whereby power generation is performed.

  The cooling unit 6 is formed of a conductive and porous material. For example, a plate of carbon is used. Thus, the cooling water flowing through the cooling water flow path of the cooling unit 6 is supplied to the electrolyte membrane 4 through the fuel electrode 3.

  Water (hereinafter, referred to as “cooling water”) circulating in the cooling water circulation path 19 is supplied to the cooling unit 6 to cool the fuel cell FC. The cooling water whose temperature has risen by passing through the cooling unit 6 flows into the heat exchanger 8 provided in the middle of the cooling water circulation path 19. In the heat exchanger 8, the cooling water exchanges heat with the hot water flowing through the exhaust heat recovery passage 25 and passes the exhaust heat recovered from the fuel cell FC to the hot water. Hot and cold water is stored in the hot water storage tank 7, where heat storage is performed.

  The reformer 1 is supplied with a raw fuel containing hydrocarbons (for example, a city gas containing methane, etc.), and water is supplied through the valve V 2 via the reforming water supply passage 20 branched from the cooling water circulation passage 19. Be done. The reformer 1 performs steam reforming of the raw fuel using the combustion heat supplied from the combustor 2 provided in parallel. The fuel gas containing hydrogen as a main component obtained by steam reforming in the reformer 1 is supplied to the fuel electrode 3 through the fuel gas supply passage 14.

  In the fuel electrode 3, not all the supplied fuel gas is consumed in the power generation reaction. Therefore, components of the fuel gas such as hydrogen remain in the fuel electrode exhaust gas discharged from the fuel electrode 3. Therefore, the anode exhaust gas is used as the combustion gas in the combustor 2. Specifically, the fuel electrode exhaust gas is supplied from the fuel electrode 3 to the combustor 2 through the fuel electrode exhaust gas passage 15. The flue gas burned in the combustor 2 is discharged to the outside through the flue gas passage 16.

  The fuel electrode exhaust gas and the combustion exhaust gas contain water. Therefore, water recovery devices 21 and 22 are provided in the middle of the fuel electrode exhaust gas passage 15 and the combustion exhaust gas passage 16 for the purpose of collecting the moisture. The water recovery devices 21 and 22 are configured, for example, by combining a condenser and a drain trap. That is, water contained in the anode exhaust gas and the combustion exhaust gas is condensed by the condenser, and the condensed water is taken out by the drain trap. The water taken out by the drain trap is recovered to the water recovery tank 10 and reused as water circulating in the cooling water circulation path 19.

  As described above, since the cooling water flowing through the cooling water circulation path 19 is mixed with the water contained in the fuel electrode exhaust gas and the water contained in the combustion exhaust gas, impurities not dissolved in the electrolyte and water, etc. Is assumed to be included. Therefore, the fuel cell system according to the present embodiment is configured such that the cooling water flowing through the cooling water circulation path 19 is treated by the water treatment device 9 provided in the middle of the cooling water circulation path 19. In the present embodiment, the water treatment apparatus 9 includes an adsorbent 9a capable of adsorbing an organic substance or the like present in cooling water, and an ion exchange resin 9b capable of removing ions dissolved in the cooling water. The water treatment apparatus 9 may be configured of only one of the adsorbent 9a and the ion exchange resin 9b, or may be provided with means other than these. For example, a reverse osmosis membrane may be used in combination.

The ion exchange resin 9 b is an electrolyte contained in cooling water by exchanging ions of the electrolyte dissolved in the cooling water (for example, ionized and dissolved salts, ammonia, etc.) with, for example, H ⁺ or OH ^−. Function to relatively lower the concentration of (ie, lower the electrical conductivity). For example, the electrical conductivity of the cooling water flowing through the cooling water circulation path 19 downstream of the water treatment apparatus 9 is preferably about 1 μS / cm to 10 μS / cm.

  The adsorbent 9a comprises, for example, activated carbon or the like, and adsorbs adsorbed substances such as organic substances (for example, siloxanes, nonpolar or polar organic molecules, microorganisms and secretions of microorganisms, oils and the like) contained in cooling water. Demonstrate a function. For example, the oil concentration of the cooling water flowing through the cooling water circulation path 19 downstream of the water treatment device 9 is preferably about 0.01 wtppm to 1 wtppm.

  The exhaust heat recovered from the cooling water in the heat exchanger 8 described above (that is, the exhaust heat recovered from the fuel cell FC) is given to the hot and cold water flowing through the exhaust heat recovery passage 25, and the hot and cold water is stored in the hot water storage tank 7. In the present embodiment, the exhaust heat recovery apparatus 12 for recovering the exhaust heat of the fuel cell FC includes the hot water storage tank 7 and the auxiliary heat source unit 11. Specifically, the exhaust heat recovery apparatus 12 has an exhaust heat recovery path 25 in which the hot and cold water stored in the hot water storage tank 7 circulates between the hot water storage tank 7 and the heat exchanger 8. The flow rate of hot and cold water in the exhaust heat recovery passage 25 is adjusted by the pump P2. In addition, the exhaust heat recovery device 12 has a hot water circulation path 26 in which hot water stored in the hot water storage tank 7 is supplied to the heat utilization device 13 via the auxiliary heat source unit 11. The flow velocity of the hot and cold water in the hot and cold water circulation passage 26 is adjusted by the pump P3. When the heat utilization device 13 is a floor heating device that uses only the heat of hot water, the hot water after the heat is utilized by the heat utilization device 13 returns to the hot water storage tank 7 through the hot water circulation path 26. Alternatively, when the heat utilization device 13 is a water heater or the like that uses the hot water itself, the hot water does not return to the hot water storage tank 7. The auxiliary heat source unit 11 is used when the hot water required by the heat utilization device 13 is heated to a predetermined temperature and then supplied to the heat utilization device 13.

  While the fuel cell FC is performing a power generation operation, the operation control device 27 operates the reformer 1 and the combustor 2 to supply the fuel gas from the reformer 1 to the fuel electrode 3, and the oxygen-containing gas supply passage A blower (not shown) provided at 17 is operated to supply air (oxygen-containing gas) to the oxygen electrode 5. As a result, in the cell C, a power generation reaction is performed, and power is output to an electric load (not shown), an inverter (not shown) or the like. The oxygen electrode exhaust gas generated at the oxygen electrode 5 is discharged to the outside through the oxygen electrode exhaust gas passage 18.

  When the fuel gas is generated by the reformer 1, the operation control device 27 supplies the raw fuel to the reformer 1, operates the pump P1 provided in the cooling water circulation path 19, and operates the cooling water circulation path. The valve V2 provided in the reforming water supply passage 20 branched from 19 is opened to supply reforming water to the reformer 1. As described above, the heat of combustion generated in the combustor 2 is given to the reformer 1 to promote the steam reforming reaction.

<Adjustment operation by operation control unit>
The operation control device 27 controls at least one of the pressure control valve V1 and the pump P1 provided in the cooling water circulation path 19 to cool the pressure of the fuel gas in the fuel gas supply path 14 and the cooling water flow path of the cooling unit 6 It has an operation control part which performs adjustment operation which adjusts pressure difference deltaP with pressure of water.

  Specifically, when the operation determination unit to be described later determines that the adjustment operation is to be performed, the operation control unit controls the pressure adjustment valve V1 and the pump P1 to reduce the pressure of the cooling water in the cooling water circulation path 19, Thus, the pressure of the cooling water in the cooling water flow path of the cooling unit 6 is reduced. Then, the pressure difference ΔP between the pressure of the fuel gas in the fuel gas supply passage 14 and the pressure of the cooling water in the cooling water passage of the cooling unit 6 rises.

  Here, the elimination of the flooding phenomenon due to the increase of the pressure difference ΔP will be described. When power is generated in the fuel cell FC, water is generated at the fuel electrode 3 by the combination of protons (hydrogen ions) and oxygen. The surplus of the water generated at the fuel electrode 3 is sent to the cooling water flow path through the conductive porous cooling unit 6 by capillary action. That is, during the operation of the fuel cell FC, the pressure of the cooling water in the cooling water passage of the cooling unit 6 is kept lower than the pressure of the fuel gas in the fuel gas supply passage 14.

  Here, if the fuel cell FC is continuously performed for a long time, the function of capillary action in the cooling unit 6 becomes small, so that the so-called flooding phenomenon occurs, in which excessive water is not drawn out and drainage is not properly performed. In addition, since the action of the capillary phenomenon deteriorates with age and changes depending on the operating conditions, the timing of occurrence of the flooding phenomenon is various.

  When the operation control unit reduces the pressure of the cooling water in the cooling water circulation path 19, the pressure difference ΔP is increased to promote the movement of water by capillary action, so that the flooding phenomenon can be eliminated. Further, even in the case where a void is generated due to insufficient hydrophilicity or the influence of continuous operation inside the cooling portion 6 which is porous, water penetrates into the interior of the cooling portion 6 due to the increase of the pressure difference ΔP, thereby cooling It is possible to restore and strengthen the water removal function by the part 6.

  When the operation determining unit to be described later determines to perform the adjusting operation, the operation control unit controls the pressure adjusting valve V1 and the pump P1 to raise the pressure of the cooling water in the cooling water circulation path 19, The pressure of the cooling water in the cooling water flow path of the cooling unit 6 may be increased. In this case, although the pressure difference ΔP between the pressure of the fuel gas in the fuel gas supply passage 14 and the pressure of the cooling water in the cooling water passage of the cooling unit 6 decreases, the water retention state in the fuel electrode 3 and the cooling unit 6 May be able to eliminate the lack of water retention. As described above, in the present embodiment, the operation control unit controls the pressure control valve V1 and the pump P1, and the pressure of the fuel gas in the fuel gas supply passage 14 and the pressure of the cooling water in the cooling water passage of the cooling unit 6 An adjustment operation is performed to adjust (increase or decrease) the pressure difference ΔP.

  Further, in the adjustment operation, only one of the pressure control valve V1 and the pump P1 may be controlled to increase or decrease the pressure of the cooling water in the cooling water circulation path 19.

<Operation determination unit>
The operation control device 27 has an operation determination unit that determines whether to perform the above-described adjustment operation based on a voltage decrease rate v that is a decrease rate of the output voltage V of the fuel cell FC with respect to time. The operation determining unit determines that the adjustment operation is necessary when the voltage reduction rate v exceeds a predetermined reduction rate threshold Sv.

  Specifically, the operation determining unit acquires and stores the output voltage V of the fuel cell FC at predetermined time intervals, divides the amount of change of the output voltage V by time, and calculates and stores the voltage reduction rate v. Then, every time the voltage drop rate v is calculated, it is compared with the drop rate threshold value Sv set and stored in advance, and when the voltage drop rate v exceeds the drop rate threshold value Sv, it is determined that the adjustment operation described above is necessary.

<Cancel of Adjustment Operation by Operation Control Unit>
When the elapsed time τ1 from the previous adjustment operation does not exceed the preset adjustment operation prohibition time ST2, the operation control unit does not perform the adjustment operation regardless of the determination by the operation determination unit.

  Specifically, when the adjustment operation is completed, the operation control unit starts measuring time from that point, and stores it as elapsed time τ1 each time. Then, when the operation determination unit determines that the adjustment operation is necessary, the stored elapsed time τ1 is compared with the adjustment operation prohibition time ST2. If the elapsed time τ1 is longer than the adjustment operation inhibition time ST2, the operation control unit executes the above-described adjustment operation. If the elapsed time τ1 is smaller than or equal to the adjustment operation inhibition time ST2, the operation control unit does not execute the above-described adjustment operation.

  Further, the operation control unit refers to the output instruction value R which is the instruction value of the output to the fuel cell FC, and outputs the output instruction value R in the period from the time point before the preset output instruction value confirmation period ST1 to the present. If the change width ΔR is larger than the preset output instruction fluctuation threshold value SR, the adjustment operation is not performed regardless of the determination by the operation determination unit.

  Specifically, the operation control unit stores an output instruction value R, which is an instruction value for output to the fuel cell FC, at predetermined time intervals. Then, when the operation determination unit determines that the adjustment operation is necessary, the output instruction value R from that time to the time before the output instruction value confirmation period ST1 is read out, and the maximum value of the output instruction value R in that period The difference with the minimum value is calculated, and the value is stored as a change width ΔR of the output instruction value R. Next, the variation range ΔR and the output indication variation threshold value SR are compared, and if the variation range ΔR is smaller than or equal to the output indication variation threshold value SR, the adjustment operation is performed. If the change width ΔR is larger than the output command fluctuation threshold value SR, the adjustment operation is not performed.

<Adjustment operation control>
The adjustment operation control performed by the fuel cell system according to the first embodiment will be described with reference to the flowchart of FIG.

  In step # 1, the operation control device 27 (operation determination unit) determines whether the voltage decrease rate v exceeds the decrease rate threshold Sv. As a result, if the voltage decrease rate v exceeds the decrease rate threshold Sv (Yes), it is determined that the adjustment operation is necessary (step # 2), and the process proceeds to step # 4. If the voltage drop rate v is less than or equal to the drop rate threshold Sv (No), it is determined that the adjustment operation is unnecessary (step # 3), and the process proceeds to step # 7, and the adjustment operation control is performed without performing the adjustment operation. finish.

  In step # 4, the operation control device 27 (operation control unit) determines whether or not the elapsed time τ1 from the previous adjustment operation exceeds the adjustment operation inhibition time ST2. As a result, when the elapsed time τ1 does not exceed the adjustment operation inhibition time ST2 (No), the process proceeds to step # 7, the adjustment operation is not performed, and the adjustment operation control is ended. If the elapsed time τ1 exceeds the adjustment operation inhibition time ST2 (Yes), the process proceeds to step # 5.

  In step # 5, the operation control device 27 (operation control unit) determines whether or not the change width ΔR of the output command value R is larger than the output command fluctuation threshold value SR. As a result, if the change width ΔR is larger than the output command fluctuation threshold value SR (Yes), the process proceeds to step # 7, the adjustment operation control is ended without performing the adjustment operation. If the change width ΔR is smaller than or equal to the output command fluctuation threshold value SR (No), the process proceeds to step # 6, the operation control device 27 (operation control unit) executes the adjustment operation, and the adjustment operation control is ended.

Next, an example of the adjustment operation control according to the first embodiment will be described using the graph of FIG. When the adjustment operation at a time T ₀ is performed, the output voltage V is after rising once decreases. As the voltage drop rate v when it is relatively large, from time T ₀ before adjustment operation prohibition time ST2 has elapsed, adjustment operation by the operation control unit by step # 4 described above is not executed.

Then the output voltage V is a stable state, it begins to decrease from the previous time T _2. Then the voltage drop rate v exceeds the rate of decrease threshold Sv at time T _1, operation determining unit determines that it is necessary to adjust operation (step # 1 → # 2).

  At time T1, an elapsed time τ1 from the previous adjustment operation (time T0) exceeds the adjustment operation prohibition time ST2 (steps # 4 to # 5).

Then the operation control unit reads the output instruction value R from time T ₁ to a previous point in time only the output instruction value confirmation period ST1 to calculate the variation width [Delta] R. In the example of FIG. 4, since the output instruction value R is constant, ΔR = 0. Then variation width ΔR is smaller than the output instruction variation threshold SR, adjustment operation at time T ₁ is executed (step # 5 → # 6).

When the adjustment operation at time T ₁ is performed, the output voltage V is after rising once decreases. As the voltage drop rate v when it is relatively large, from time T ₁ before adjustment operation prohibition time ST2 has elapsed, adjustment operation by the operation control unit by step # 4 described above is not executed.

Second Embodiment
In the second embodiment, the operation determining unit needs the adjustment operation when the state in which the voltage drop rate v exceeds the preset drop rate threshold Sv continues beyond the preset drop continuation time threshold ST3. Decide to be. The configuration of the fuel cell system according to the second embodiment is the same as that of the first embodiment. The operation of the fuel cell system according to the second embodiment will be described below with reference to FIGS. 3 and 4. About the same composition as a 1st embodiment, the same numerals are used and explanation is omitted.

Specifically, the operation determining unit acquires and stores the output voltage V of the fuel cell FC at predetermined time intervals, divides the amount of change of the output voltage V by time, and calculates and stores the voltage reduction rate v. Then, each time the voltage drop rate v is calculated, the voltage drop rate v is compared with a preset drop rate threshold value Sv. When the voltage drop rate v exceeds the drop rate threshold value Sv, measurement of time is started from that point and stored as elapsed time τ 2 each time. Then, when the elapsed time τ2 exceeds the reduction duration threshold ST3 set and stored in advance, it is determined that the above-described adjustment operation is necessary.
<Adjustment operation control>
The adjustment operation control performed by the fuel cell system according to the second embodiment will be described with reference to the flowchart of FIG.

  In step # 11, the operation control device 27 (operation determination unit) determines whether or not the voltage decrease rate v exceeds the decrease rate threshold Sv. As a result, when the voltage decrease rate v exceeds the decrease rate threshold Sv (Yes), the process proceeds to step # 12. If the voltage decrease rate v is lower than or equal to the decrease rate threshold Sv (No), it is determined that the adjustment operation is unnecessary (step # 14), and the process proceeds to step # 18 to perform adjustment operation control without performing the adjustment operation. finish.

  In step # 12, the operation control device 27 (operation determination unit) determines whether the state in which the voltage decrease rate v exceeds the decrease rate threshold Sv continues beyond the decrease continuation time threshold ST3. As a result, when continuing beyond the fall continuation time threshold ST3 (Yes), it is determined that the adjustment operation is necessary (step # 13), and the process proceeds to step # 15. If it does not continue beyond the decrease continuation time threshold ST3 (No), it is determined that the adjustment operation is unnecessary (step # 14), the process proceeds to step # 18, the adjustment operation control is ended without performing the adjustment operation. .

  In step # 15, the operation control device 27 (operation control unit) determines whether or not the elapsed time τ1 from the previous adjustment operation exceeds the adjustment operation inhibition time ST2. As a result, when the elapsed time τ1 does not exceed the adjustment operation inhibition time ST2 (No), the process proceeds to step # 18, and the adjustment operation control is ended without performing the adjustment operation. If the elapsed time τ1 exceeds the adjustment operation inhibition time ST2 (Yes), the process proceeds to step # 16.

  In step # 16, the operation control device 27 (operation control unit) determines whether or not the change width ΔR of the output command value R is larger than the output command fluctuation threshold value SR. As a result, if the change width ΔR is larger than the output command fluctuation threshold value SR (Yes), the process proceeds to step # 18, the adjustment operation control is ended without performing the adjustment operation. If the change width ΔR is smaller than or equal to the output instruction fluctuation threshold value SR (No), the process proceeds to step # 17, the operation control device 27 (operation control unit) executes the adjustment operation and ends the adjustment operation control.

Next, an example of adjustment operation control according to the second embodiment will be described using the graph of FIG. 4. When the adjustment operation at a time T ₀ is performed, the output voltage V is after rising once decreases. Although during this period the voltage drop rate v is relatively large, from time T ₀ before adjustment operation prohibition time ST2 has elapsed, adjustment operation by the operation control unit by step # 15 described above is not executed.

Although then the output voltage V becomes a stable state, begins to decrease from the previous time T _2,, at time T _2, the voltage reduction rate v exceeds the rate of decrease threshold Sv (step # 11 → # 12). The reduction rate threshold value Sv in the second embodiment is set to be smaller than the value in the first embodiment.

And while the decrease time duration threshold ST3, continues the state in which the voltage reduction rate v exceeds the rate of decrease threshold Sv, the elapsed time τ2 at time T ₁ is greater than the decrease time duration threshold ST3, the operation determination unit adjustment operation It is determined that it is necessary (step # 12 → # 13).

In the time T _1, the elapsed time τ1 from the previous adjustment operation (the time T0), exceeds the adjustment operation prohibition time ST2 (step # 15 → # 16).

Then the operation control unit reads the output instruction value R from time T ₁ to a previous point in time only the output instruction value confirmation period ST1 to calculate the variation width [Delta] R. In the example of FIG. 4, since the output instruction value R is constant, ΔR = 0. Then variation width ΔR is smaller than the output instruction variation threshold SR, adjustment operation is executed at time T ₁ (step # 16 → # 17).

When the adjustment operation at time T ₁ is performed, the output voltage V is after rising once decreases. As the voltage drop rate v when it is relatively large, from time T ₁ before adjustment operation prohibition time ST2 has elapsed, adjustment operation by the operation control unit by step # 15 described above is not executed.

Another Embodiment
In the first embodiment described above, although both step # 4 and step # 5 are performed for stopping the adjustment operation by the operation control unit, the operation control unit 27 (operation control unit) is configured to perform one of them. May be Similarly, in the second embodiment, both step # 15 and step # 16 are performed for stopping the adjustment operation by the operation control unit, but the operation control unit 27 (operation control unit) is configured to perform one of them. May be

  In the first and second embodiments described above, by adjusting the pressure of the cooling water in the adjusting operation, the pressure of the fuel gas in the fuel gas supply passage 14 and the pressure of the cooling water in the cooling water passage of the cooling unit 6 The pressure difference ΔP was adjusted. Instead of this, the pressure difference ΔP may be adjusted by adjusting the pressure of the fuel gas in the fuel gas supply passage 14.

  Note that the configurations disclosed in the above-described embodiment (including the other embodiments, and the same hereinafter) can be applied in combination with the configurations disclosed in the other embodiments as long as no contradiction arises. The embodiment disclosed in the present specification is an exemplification, and the embodiment of the present invention is not limited thereto, and can be appropriately modified without departing from the object of the present invention. In particular, the adjustment operation described above is an example, and any other form may be used as long as the pressure difference ΔP between the pressure of the fuel gas in the fuel gas supply passage 14 and the pressure of the cooling water in the cooling water passage of the cooling unit 6 is adjusted. It is possible to take.

3: fuel electrode 4: electrolyte membrane 5: oxygen electrode 6: cooling unit 14: fuel gas supply passage 19: cooling water circulation passage 27: operation control device (operation control unit, operation determination unit)
C: Cell FC: Fuel cell P1: Pump V1: Pressure regulator

Claims (4)

A fuel comprising a plurality of cells formed by sandwiching a solid polymer electrolyte membrane between a fuel electrode and an oxygen electrode, and having a cooling water flow path for circulating a cooling water, and laminated via a conductive porous cooling portion. A battery, a fuel gas supply passage for supplying a fuel gas to the fuel electrode, and a cooling water circulation passage for circulating the cooling water flowing out from the cooling water passage and supplying the coolant to the cooling water passage;
Adjustment to adjust the pressure difference between the pressure of the fuel gas in the fuel gas supply passage and the pressure of the cooling water in the cooling water passage by controlling at least one of the pressure adjusting valve and the pump provided in the cooling water circulation passage An operation control unit that performs an operation;
Possess an operation determination unit that determines whether or not to perform the adjustment operation based on the voltage drop rate is decreasing rate with respect to time of the output voltage of the fuel cell,
The operation control unit
If the operation determining unit determines that the adjustment operation is to be performed, the output instruction value which is an instruction value of the output to the fuel cell is referred to, and an output instruction value confirmation period previously set based on the determined time is made earlier. If the change range of the output instruction value in the period from the time point of time to the determined time point is larger than the preset output instruction fluctuation threshold value, the adjustment operation is performed regardless of the determination by the operation determination unit Not a solid polymer fuel cell system.   The polymer electrolyte fuel cell system according to claim 1, wherein the operation determining unit determines that the adjustment operation is necessary when the voltage decrease rate exceeds a preset decrease rate threshold.   The operation determining unit determines that the adjustment operation is necessary when a state in which the voltage drop rate exceeds the preset drop rate threshold continues beyond the preset drop continuation time threshold. The polymer electrolyte fuel cell system according to 1.   The operation control unit does not perform the adjustment operation regardless of the determination by the operation determination unit when the elapsed time from the previous adjustment operation does not exceed the adjustment operation prohibition time set in advance. The polymer electrolyte fuel cell system according to any one of 3.

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