Control device of fuel cell system, fuel cell system, control method, and control program

Abstract

To provide a control device of a fuel cell system capable of improving power generation efficiency.SOLUTION: A set value determination unit of a control device in a fuel cell system according to one embodiment determines whether an output set value has changed from an output set value acquired immediately before. When it is determined that the output set value has changed, an addition unit adds an output difference, which is a difference between the output set values to an integrated value, and when it is determined that the output set value has not changed, the addition unit adds a predetermined addition value to the integrated value. An integrated value determination unit determines whether the integrated value has reached a predetermined integrated threshold value. A purging valve control unit opens a purge valve for a predetermined time when it is determined that the integrated value has reached the integrated threshold value.SELECTED DRAWING: Figure 2

Description

[Technical field]

[0001] The present embodiment relates to a control device for a fuel cell system, a fuel cell system, a control method, and a control program. [Background technology]

[0002] In a fuel cell, fuel gas supplied to the fuel electrode and air supplied to the air electrode undergo an electrochemical reaction via an electrolyte membrane to generate power output. During this process, nitrogen gas contained in the air cross-leaks through the electrolyte membrane, and is mixed into the fuel off-gas discharged from the fuel electrode. As a result, the hydrogen concentration in the fuel off-gas becomes lower than that of the fuel gas.

[0003] The fuel off-gas discharged from the fuel cell may be supplied again to the fuel cell through a recycle line. In this case, the fuel off-gas is mixed with the fuel gas and supplied to the fuel cell. Therefore, if the fuel cell continues to operate, the hydrogen concentration of the fuel gas supplied to the fuel electrode may decrease.

[0004] To address this issue, a purge line including a purge valve is connected to the recycle line. When the purge valve is opened, the fuel off-gas is discharged to the outside, increasing the hydrogen concentration of the fuel gas supplied to the anode.

[0005] When the output of the fuel cell is high, a higher hydrogen concentration is required than when the output is low. For this reason, there is known a fuel cell system that performs interrupt control by opening the purge valve as described above when increasing the output of the fuel cell.

[0006] However, in such a fuel cell system, even if the concentration of fuel gas is high, such as immediately after the purge valve is closed, interruption control may be performed to increase the output of the fuel cell. In this case, the purge valve opens and fuel off-gas with a high hydrogen concentration is discharged to the outside, resulting in a decrease in power generation efficiency. [Prior art documents] [Patent documents]

[0007] [Patent Document 1] JP 2003-109627 A [Patent Document 2] Patent No. 5200328 Summary of the Invention [Problem to be solved by the invention]

[0008] An object of the embodiments is to provide a fuel cell system control device, a fuel cell system, a control method, and a control program that can improve power generation efficiency. [Means for solving the problem]

[0009] The control device for a fuel cell system according to the embodiment is a control device for a fuel cell system equipped with a purge valve that controls the discharge to the outside of the fuel off gas discharged from the fuel cell to a recycle line. This control device includes an initialization unit, a set value acquisition unit, a set value determination unit, an addition unit, an integrated value determination unit, and a purge valve control unit. The initialization unit initializes the integrated value. The set value acquisition unit acquires an output set value of the fuel cell. The set value determination unit determines whether or not the output set value acquired by the set value acquisition unit has changed with respect to the output set value acquired immediately before. If it is determined that the output set value has changed, the addition unit adds an output difference obtained by subtracting the immediately previous output set value from the current output set value to the integrated value, and if it is determined that the output set value has not changed, it adds a predetermined added value to the integrated value. The integrated value determination unit determines whether or not the integrated value to which the output difference or the added value has been added has reached a predetermined integrated threshold value. If it is determined that the integrated value has reached the integrated threshold value, the purge valve control unit opens the purge valve for a predetermined time.

[0010] The fuel cell system according to the embodiment includes a fuel cell, a recycle line that returns fuel off-gas discharged from the fuel cell to the fuel cell, a purge valve that controls the discharge to the outside of the fuel off-gas flowing through the recycle line, and a control device for the above-mentioned fuel cell system.

[0011] A control method for a fuel cell system according to an embodiment is a control method for a fuel cell system equipped with a purge valve that controls the discharge to the outside of fuel off-gas discharged from the fuel cell to a recycle line. This control method includes the steps of initializing an integrated value, acquiring an output set value of the fuel cell, determining whether the acquired output set value has changed from the output set value acquired immediately before, adding an output difference obtained by subtracting the immediately previous output set value from the current output set value to the integrated value if it is determined that the output set value has changed, and adding a predetermined additional value to the integrated value if it is determined that the output set value has not changed, determining whether the integrated value to which the output difference or the additional value has been added has reached a predetermined integrated threshold value, and opening the purge valve for a predetermined time if it is determined that the integrated value has reached the integrated threshold value.

[0012] A control program for a fuel cell system according to an embodiment is a control program for a fuel cell system that causes a computer to execute a control method for a fuel cell system that includes a purge valve that controls the discharge to the outside of fuel off-gas discharged from the fuel cell to a recycle line. This control method includes the steps of: setting an integrated value, acquiring an output set value for the fuel cell, determining whether the acquired output set value has changed from the output set value acquired immediately before, adding an output difference obtained by subtracting the immediately previous output set value from the current output set value to the integrated value if it is determined that the output set value has changed, and adding a predetermined additional value to the integrated value if it is determined that the output set value has not changed, determining whether the integrated value to which the output difference or the additional value has been added has reached a predetermined integrated threshold value, and opening the purge valve for a predetermined time if it is determined that the integrated value has reached the integrated threshold value. Effect of the Invention

[0013] According to the embodiment, it is possible to improve the power generation efficiency. [Brief description of the drawings]

[0014] [Figure 1] FIG. 1 is a diagram showing a fuel cell system according to the present embodiment. [Diagram 2] FIG. 2 is a block diagram illustrating the control device shown in FIG. [Diagram 3] FIG. 3 is a flowchart showing a control method executed by the control device shown in FIG. [Figure 4] FIG. 4 is a time chart showing an example of the operation of the fuel cell system shown in FIG. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0015] DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A control device for a fuel cell system, ... control method, and a control program according to an embodiment of the present invention will be described below with reference to the drawings.

[0016] First, a fuel cell system 1 according to the present embodiment will be described with reference to Fig. 1. The fuel cell system 1 according to the present embodiment generally includes a purge valve 15 (described later) for controlling the discharge to the outside of the fuel off-gas discharged from the fuel cell 2 to a recycle line 6 (described later).

[0017] More specifically, as shown in FIG. 1, the fuel cell system 1 includes a fuel cell 2, a fuel gas supply line 3, an air supply line 4, an air exhaust line 5, a recycle line 6, a purge line 7, a power conditioner 8, and a control device 20.

[0018] The fuel cell 2 includes a fuel electrode 2a (anode), an air electrode 2b (cathode), and an electrolyte membrane 2c interposed between the fuel electrode 2a and the air electrode 2b. An electrochemical reaction occurs between the fuel gas supplied to the fuel electrode 2a and the air supplied to the air electrode 2b via the electrolyte membrane 2c, and power output is obtained. Examples of the fuel gas include hydrogen gas and mixed gases containing hydrogen gas.

[0019] The fuel gas supply line 3 supplies the fuel gas stored in a fuel gas supply unit (not shown) to the fuel electrode 2a of the fuel cell 2. A fuel cutoff valve 9 and a fuel pressure reducing valve 10 may be provided in the fuel gas supply line 3. The fuel cutoff valve 9 is a valve that controls the supply of fuel gas to the fuel electrode 2a. The fuel cutoff valve 9 opens when the fuel cell system 1 is in operation to supply the fuel gas to the fuel electrode 2a. The fuel cutoff valve 9 may be composed of two valves arranged in series. The fuel pressure reducing valve 10 is a valve that adjusts the supply flow rate of the fuel gas to the fuel electrode 2a. The fuel cutoff valve 9 and the fuel pressure reducing valve 10 may be controlled by a control device 20.

[0020] The air supply line 4 supplies air to the air electrode 2b of the fuel cell 2. An air blower 11 and an air inlet cutoff valve 12 may be provided in the air supply line 4. The air inlet cutoff valve 12 is a valve that controls the supply of air to the air electrode 2b. The air inlet cutoff valve 12 opens when the fuel cell system 1 is in operation to supply air to the air electrode 2b. The air blower 11 and the air inlet cutoff valve 12 may be controlled by a control device 20.

[0021] The air discharge line 5 discharges the air discharged from the air electrode 2b of the fuel cell 2 to the outside. An air outlet cutoff valve 13 may be provided in the air discharge line 5. The air outlet cutoff valve 13 is a valve that controls the discharge of air from the air electrode 2b to the outside. The air outlet cutoff valve 13 opens when the fuel cell system 1 is in operation to discharge air from the air electrode 2b. The air outlet cutoff valve 13 may be controlled by the control device 20.

[0022] The recycle line 6 is configured to return the fuel off-gas discharged from the fuel electrode 2a of the fuel cell 2 to the fuel cell 2. The upstream end of the recycle line 6 may be connected to the fuel electrode 2a of the fuel cell 2 described above, and the downstream end of the recycle line 6 may be connected to the fuel gas supply line 3 described above. In this case, the fuel off-gas discharged from the fuel electrode 2a can be supplied to the fuel gas supply line 3, and the fuel off-gas can be recycled. The recycle line 6 may be provided with a recycle blower 14. The recycle blower 14 draws in the fuel off-gas from the fuel electrode 2a and sends it to the fuel gas supply line 3. The recycle blower 14 may be controlled by the control device 20.

[0023] The purge line 7 is configured to control the discharge of the fuel off-gas flowing through the recycle line 6 to the outside. A purge valve 15 may be provided in the purge line 7. The purge valve 15 is a valve that controls the discharge of the fuel off-gas from the recycle line 6 to the outside. The purge valve 15 may be controlled by a purge valve control unit 37 (described later) of the control device 20.

[0024] As shown in Fig. 1, the power conditioner 8 is a device for adjusting the power generation output of the fuel cell 2. An output setting value is transmitted to the power conditioner 8 from an output value setting unit 23 (described later) of the control device 20 at a predetermined cycle (hereinafter referred to as the set cycle), and the power conditioner 8 adjusts the power generation output (or generated power) taken out from the fuel cell 2 according to this output setting value. The power generation output of the fuel cell 2 is supplied to an external load through an output line 16 on which the power conditioner 8 is provided. The power conditioner 8 measures the power generation output value output from the fuel cell 2 and transmits it to the control device 20. The power conditioner 8 may be a DC / DC converter or an inverter.

[0025] Next, the control device 20 for the fuel cell system according to this embodiment will be described.

[0026] The control device 20 may include a communication unit 21, a storage unit 22, an output value setting unit 23, and a calculation unit 30.

[0027] The communication unit 21 is configured to be able to communicate with the above-mentioned valves, blowers, and power conditioner 8. The communication unit 21 may be able to communicate with these devices via a wired connection or wirelessly.

[0028] The storage unit 22 may be configured to store any information. The storage unit 22 may store an output setting value and an integrated value, which will be described later. The storage unit 22 may store a control program, which will be described later.

[0029] The output value setting unit 23 sets an output set value that is a target value for the power generation output of the fuel cell 2. The power generation output may be set based on a command from a higher-level control device (not shown) or based on an input command from a user. The output value setting unit 23 may set the output set value at the above-mentioned setting cycle. The output value setting unit 23 may transmit the output set value to the power conditioner 8 at the timing when the output set value is set.

[0030] The calculation unit 30 may be configured to execute a control method for the fuel cell system 1. The calculation unit 30 may include an initialization unit 31, a period elapsed determination unit 32, a set value acquisition unit 33, a set value determination unit 34, an addition unit 35, an integrated value determination unit 36, and a purge valve control unit 37. The functions of each unit may be realized, for example, by executing a computer program stored in the above-mentioned storage unit 22. This program is an example of a control program (or a purge program) for the fuel cell system 1, and may be installed in the control device 20 from a recording medium.

[0031] The initialization unit 31 initializes the integrated value. When starting the control method according to this embodiment, the initialization unit 31 may set the initial value of the integrated value to 0 (zero). As described later, an output difference or an addition value is added to the integrated value at a predetermined addition period. When the integrated value reaches an integration threshold, the purge valve 15 is configured to open, and the integrated value serves as an index indicating the timing to open the purge valve 15.

[0032] Furthermore, the initialization unit 31 may initialize the integrated value when it is determined that the integrated value has reached the integration threshold. In this case, the initialization unit 31 may also set the initial value of the integrated value to 0 (zero). The initialization unit 31 may initialize the integrated value at the timing when the integrated value determination unit 36 ​​determines that the integrated value has reached the integration threshold. Alternatively, the initialization unit 31 may initialize the integrated value at the timing when the purge valve 15 opens after the integrated value has reached the integration threshold, or may be performed after the purge valve 15 opens and before the purge valve 15 closes.

[0033] The period elapse determination unit 32 determines whether a predetermined period (hereinafter, referred to as an addition period) has elapsed. That is, the period elapse determination unit 32 continues the determination process until one addition period has elapsed. This addition period may be synchronized with the setting period of the output set value by the output value setting unit 23 described above, but it does not have to be synchronized and is arbitrary.

[0034] The set value acquisition unit 33 acquires the output set value from the output value setting unit 23. The set value acquisition unit 33 may acquire the output set value when the above-mentioned cycle elapse determination unit 32 determines that the addition cycle has elapsed. In this case, the set value acquisition unit 33 acquires the output set value at the addition cycle. The acquired output set value may be stored in the above-mentioned storage unit 22.

[0035] The set value determination unit 34 determines whether the current output setting value acquired by the set value acquisition unit 33 has changed with respect to the output setting value acquired immediately before. The set value determination unit 34 may determine that the output setting value has not changed when the absolute value of the output difference is smaller than a predetermined output threshold. The output difference is a value obtained by subtracting the output setting value acquired immediately before from the output setting value acquired currently. The output threshold is a positive (plus) value. That is, the output setting value may be determined to have changed when the absolute value of the output difference is equal to or greater than the output threshold. In this case, the current output setting value has changed relatively more than the immediately previous output setting value. On the other hand, when the absolute value of the output difference is smaller than the output threshold, the output setting value may be determined to have not changed. For example, even if the current output setting value has changed from the immediately previous output setting value, when the absolute value of the output difference is relatively small, the output setting value may be determined to have not changed. When the above-mentioned output difference is a positive value, it means that the current output setting value has increased from the immediately previous output setting value. When the output difference is a negative (minus) value, it means that the current output setting value has decreased from the immediately previous output setting value. Both an increase and a decrease are aspects of a change. When the current output setting value is equal to the immediately preceding output setting value, the set value determination unit 34 may determine that the output setting value has not changed. The output setting value stored in the storage unit 22 may be used as the immediately preceding output setting value.

[0036] When the set value determination unit 34 determines that the output set value has changed, the adder 35 adds the output difference to the integrated value, and when the set value determination unit 34 determines that the output set value has not changed, the adder 35 adds a predetermined additional value to the integrated value. That is, when the absolute value of the output difference described above is equal to or greater than the output threshold value, the output difference is added to the integrated value. More specifically, when the output difference is a positive value, the output difference is added to the integrated value, and the integrated value increases. On the other hand, when the output difference is a negative value, the output difference is added to the integrated value, and the absolute value of the output difference is decreased from the integrated value. When the absolute value of the output difference is smaller than the output threshold value, the additional value is added to the integrated value. The adder 35 may set the additional value to a predetermined value as a constant. The additional value may be a value set based on the integrated threshold value described later and the rate of decrease in the hydrogen concentration of the fuel gas, and may be set so that the frequency of opening and closing the purge valve 15 is such that a desired hydrogen concentration can be maintained. The additional value may be a value smaller than the output threshold, a value larger than the output threshold, or a value equal to the output threshold, and is arbitrary.

[0037] The integrated value determination unit 36 ​​determines whether the integrated value to which the output difference or the addition value is added by the adding unit 35 reaches a predetermined integrated threshold. The integrated value determination unit 36 ​​may set the integrated threshold to a predetermined value as a constant. The integrated threshold may be set so that the frequency of opening and closing the purge valve 15 is such that a desired hydrogen concentration can be maintained.

[0038] When the integrated value determination unit 36 ​​determines that the integrated value has reached the integrated threshold value, the purge valve control unit 37 opens the purge valve 15 for a predetermined time. The purge valve control unit 37 closes the purge valve 15 when a predetermined time has elapsed since the purge valve 15 was opened. While the purge valve 15 is open, the above-described addition process to the integrated value by the adder 35 does not need to be performed.

[0039] Next, a method of operating the fuel cell system 1 according to this embodiment having the above-described configuration will be described.

[0040] First, the fuel gas is supplied from the fuel gas supply line 3 to the fuel electrode 2a of the fuel cell 2 by opening the fuel cutoff valve 9 shown in FIG. 1 and driving the recycle blower 14. In addition, air is supplied from the air supply line 4 to the air electrode 2b of the fuel cell 2 by driving the air blower 11 and opening the air inlet cutoff valve 12 and the air outlet cutoff valve 13. The fuel gas supplied to the fuel electrode 2a and the air supplied to the air electrode 2b react electrochemically via the electrolyte membrane 2c. This converts chemical energy into electrical energy, and the power output of the fuel cell 2 is obtained. The power output is converted into electric power in the power conditioner 8 and supplied to an external load.

[0041] The fuel gas that has passed through the fuel electrode 2a is discharged to a recycle line 6 and is supplied again to the fuel electrode 2a. In this manner, the fuel gas is circulated and recycled during operation of the fuel cell system 1. The air that has passed through the air electrode 2b is discharged to the outside through an air discharge line 5.

[0042] During operation of the fuel cell system 1, the opening and closing of the purge valve 15 is controlled by the control device 20. Hereinafter, a control method (or a purging method) for the fuel cell system 1 according to this embodiment will be described with reference to FIG.

[0043] First, in step S1, the integrated value is initialized by the initialization unit 31. Here, the initial value of the integrated value is set to 0 (zero).

[0044] After step S1, in step S2, it is determined whether or not one addition period has elapsed by the period elapse determination unit 32. If one addition period has not elapsed, step S2 is repeated until one addition period has elapsed.

[0045] If it is determined in step S2 that one addition period has elapsed, the set value acquisition unit 33 acquires the output set value from the output value setting unit 23 in step S3.

[0046] After step S3, in step S4, the set value determination unit 34 determines whether the output set value acquired in step S3 has changed with respect to the output set value acquired immediately before. In this embodiment, if the absolute value of the output difference obtained by subtracting the immediately preceding output set value from the current output set value is equal to or greater than a predetermined output threshold value that is a positive value, it may be determined that the output set value has changed. If the absolute value of this output difference is smaller than the output threshold value, it may be determined that the output set value has not changed. In step S4, which is performed for the first time, there is no output set value acquired immediately before, so in this case it may be determined that the output set value has not changed.

[0047] If it is determined in step S4 that the output setting value has changed, then in step S5, the adder 35 adds the output difference to the integrated value. On the other hand, if it is determined in step S4 that the output setting value has not changed, then in step S6, the adder 35 adds the above-mentioned added value to the integrated value.

[0048] After steps S5 and S6, in step S7, the integrated value determination unit 36 ​​determines whether or not the integrated value to which the output difference or the additional value has been added has reached an integrated threshold value.

[0049] If it is determined in step S7 that the integrated value has not reached the integration threshold value, the above-mentioned steps S2 to S4 are carried out, and then step S5 or step S6 is carried out depending on the result of the determination in step S4.

[0050] On the other hand, if it is determined in step S7 that the integrated value has reached the integrated threshold value, then in step S8, the purge valve control unit 37 opens the purge valve 15. As a result, a portion of the fuel off-gas discharged to the recycle line 6 is discharged from the purge line 7 to the outside.

[0051] After step S8, in step S9, the integrated value is initialized by the initialization unit 31. The integrated value may be initialized at the timing when step S8 is performed, or may be initialized after step S8 and before step S10, which will be described later.

[0052] After step S9, in step S10, the purge valve 15 is closed by the purge valve control unit 37. Step S10 is performed after a predetermined time has elapsed since step S8. As a result, fuel off-gas is discharged for a predetermined time, and the hydrogen concentration of the fuel gas supplied to the fuel electrode 2a is increased.

[0053] After step S10, the process returns to step S2, and the above-mentioned steps are performed.

[0054] In this manner, each step is repeated to execute the control method for the fuel cell system 1 according to this embodiment.

[0055] An example of the operation of the fuel cell system 1 according to this embodiment is shown in Fig. 4. In the first and second cycles shown in Fig. 4, the output set value remains constant, and in the third cycle, the output set value increases.

[0056] In the first cycle, the integrated value is initialized, and then the addition of the additional value to the integrated value is repeated. For convenience, in FIG. 4, the integrated value is shown to continuously increase. When the integrated value reaches the integration threshold, the purge valve 15 opens and the integrated value is initialized. After a predetermined time has elapsed since the purge valve 15 was opened, the purge valve 15 is closed. While the purge valve 15 is open, no addition is made to the integrated value, and the integrated value is maintained at the initial value.

[0057] In the second cycle following the first cycle, the addition of the additional value to the integrated value is repeated in the same manner as in the first cycle. When the integrated value reaches an integration threshold, the purge valve 15 opens for a predetermined time.

[0058] In the third cycle following the second cycle, the addition of the additive value to the integrated value is repeated in the same manner as in the first cycle until the output set value increases. After that, when the output set value increases relatively significantly, the output difference between the currently acquired output set value and the output set value acquired immediately before is added to the integrated value. FIG. 4 shows an example in which the output difference ΔP is equal to or greater than the output threshold value and is added to the integrated value. Then, the integrated value to which the output difference has been added reaches and exceeds the integrated threshold value. This causes the purge valve 15 to open and initializes the integrated value. After a predetermined time has elapsed since the purge valve 15 opened, the purge valve 15 is closed and the next cycle begins.

[0059] In this way, when the power set value is constant as shown in the first and second cycles, the purge valve 15 opens at a constant frequency. However, when the power set value increases relatively greatly, the integrated value is more likely to reach the integrated threshold value, and the purge valve 15 is more likely to open. As shown in Fig. 4, when the power set value increases relatively greatly, the purge valve 15 can be opened at that time, and the hydrogen concentration of the fuel gas can be increased quickly.

[0060] Thus, according to this embodiment, when it is determined that the current output setting value of the fuel cell 2 has changed, the output difference, which is the difference between the current output setting value and the immediately preceding output setting value, is added to the integrated value, and when it is determined that the current output setting value has not changed, a predetermined additional value is added to the integrated value. Then, when the integrated value reaches a predetermined integrated threshold value, the purge valve 15 is opened. As a result, when the integrated value does not reach the predetermined integrated threshold value, the purge valve 15 can be maintained in a closed state. Even when the output setting value has changed, when the integrated value does not reach the integrated threshold value, the purge valve 15 can be maintained in a closed state. Therefore, it is possible to prevent the fuel off-gas from being unnecessarily discharged to the outside, and to reduce the amount of hydrogen gas discharged to the outside. As a result, it is possible to improve the power generation efficiency.

[0061] Also, according to this embodiment, as described above, when it is determined that the current output set value has changed from the immediately preceding output set value, the output difference is added to the integrated value. More specifically, when the current output set value is increased from the immediately preceding output set value, the output difference becomes a positive value, and the absolute value of the output difference is added to the integrated value. This makes it possible to increase the integrated value, and to increase the frequency of opening the purge valve 15. On the other hand, when the current output set value is decreased from the immediately preceding output set value, the output difference becomes a negative value, and the absolute value of the output difference is subtracted from the integrated value. This makes it possible to decrease the integrated value, and to reduce the frequency of opening the purge valve 15. This makes it possible to extend the time until the purge valve 15 opens, and to prevent fuel off-gas from being unnecessarily discharged to the outside.

[0062] Furthermore, according to this embodiment, when it is determined that the integrated value has reached the integration threshold, the initialization unit 31 initializes the integrated value. This makes it possible to initialize the integrated value before the start of the next addition cycle, thereby improving the accuracy of determining whether the integrated value has reached the integration threshold.

[0063] Furthermore, according to this embodiment, the initialization unit 31 initializes the integrated value at the timing when the purge valve 15 is opened by the purge valve control unit 37. This makes it possible to initialize the integrated value before the start of the next addition cycle, thereby improving the accuracy of determining whether or not the integrated value has reached the integration threshold value.

[0064] Also, according to this embodiment, the set value determination unit 34 determines that the output set value has not changed if the output difference obtained by subtracting the output set value acquired immediately before from the output set value acquired by the set value acquisition unit 33 is smaller than a predetermined output threshold value, which is a positive value. This makes it possible to prevent the integrated value from increasing excessively and to prevent the integrated value from excessively reaching the integrated threshold value when the output set value changes but the output difference is relatively small. In this case, it is possible to prevent the purge valve 15 from opening excessively. This makes it possible to prevent the fuel off-gas from being unnecessarily released to the outside, and to reduce the amount of hydrogen gas released to the outside. As a result, it is possible to further improve the power generation efficiency.

[0065] Furthermore, according to this embodiment, while the purge valve 15 is open, the adder 35 does not perform addition processing to the integrated value. Since the hydrogen concentration of the fuel gas increases while the purge valve 15 is open, it is possible to prevent the integrated value from increasing unnecessarily during this time, and to prevent the purge valve 15 from opening excessively. This makes it possible to prevent fuel off-gas from being unnecessarily discharged to the outside, and to reduce the amount of hydrogen gas discharged to the outside. As a result, it is possible to further improve the power generation efficiency.

[0066] In the above-described embodiment, the integrated value determination unit 36 ​​sets the output setting value to a predetermined value as a constant. However, the embodiment is not limited to this.

[0067] For example, the integrated value determination unit 36 ​​may set the integrated threshold value according to the output set value. More specifically, the integrated value determination unit 36 ​​may set the integrated threshold value so that the value becomes smaller as the output set value increases. In this case, the integrated threshold value may be set as a linear function of the output set value. For example, when the output set value is 10, the integrated threshold value may be set to 10, and when the output set value becomes 100, the integrated threshold value may be set to 5. In this case, the frequency at which the purge valve 15 opens while the output set value is 100 can be increased to twice the frequency at which the purge valve 15 opens while the output set value is 10. Therefore, the hydrogen concentration of the fuel gas can be maintained at a high level, and the hydrogen concentration according to the output set value can be maintained.

[0068] Alternatively, for example, the integrated value determination unit 36 ​​may set the integrated threshold value so that the value decreases as the power generation output value of the fuel cell 2 increases. In this case, similarly to the above, the integrated threshold value may be set as a linear function of the power generation output. The power generation output value may be acquired from the power conditioner 8. The calculation unit 30 of the control device 20 may further include an output value acquisition unit (not shown) that acquires the power generation output value from the power conditioner 8.

[0069] Here, an example has been described in which the integration threshold is set according to the output setting value or the power generation output value. However, the initial value of the integration value may be set according to the output setting value or the power generation output value. Alternatively, the added value may be set according to the output setting value or the power generation output value.

[0070] In the above-described embodiment, the initialization unit 31 sets the initial value of the integrated value to 0 (zero). However, the embodiment is not limited to this.

[0071] For example, the initialization unit 31 may set the initial value of the integrated value according to the operation time of the fuel cell 2. The operation time does not mean the continuous operation time of the fuel cell 2, but the integrated operation time. More specifically, the initialization unit 31 may set the initial value of the integrated value so that the value becomes larger as the operation time of the fuel cell 2 becomes longer. In this case, the initial value of the integrated value may be set as a linear function of the operation time. For example, the initial value of the integrated value may be set to 0 (zero) when the operation time of the fuel cell 2 is 0 (zero), and the initial value of the integrated value may be set to 10 when the operation time of the fuel cell 2 is 10000. If the integration threshold is set to 20, the frequency at which the purge valve 15 opens when the operation time is 10000 can be increased to twice the frequency at which the purge valve 15 opens when the operation time is 0 (zero). Therefore, the hydrogen concentration of the fuel gas can be maintained at a high level, and the power generation output value of the fuel cell 2 can be increased. Although the fuel cell 2 may deteriorate as the operation time passes, the stable operation of the fuel cell 2 can be continued even in this case.

[0072] In the above-described embodiment, the addition unit 35 sets the additional value to a predetermined value as a constant. However, the embodiment is not limited to this.

[0073] For example, the adder 35 may set the additional value according to the operation time of the fuel cell 2. More specifically, the adder 35 may set the additional value so that the value increases as the operation time of the fuel cell 2 becomes longer. In this case, the additional value may be set as a linear function of the operation time. For example, the additional value may be set to 1 when the operation time of the fuel cell 2 is 0 (zero), and set to 2 when the operation time of the fuel cell 2 is 10000. The frequency at which the purge valve 15 opens when the operation time is 10000 can be increased to twice the frequency at which the purge valve 15 opens when the operation time is 0 (zero). Therefore, the hydrogen concentration of the fuel gas can be maintained at a high level, and the power generation output value of the fuel cell 2 can be increased. Although the fuel cell 2 may deteriorate over the operation time, the fuel cell 2 can continue to operate stably even in this case.

[0074] As described above, when the initial value of the integrated value is set to a value corresponding to the operation time of the fuel cell 2, the initial value of the integrated value becomes large in the fuel cell 2 after the operation time has elapsed. In this case, even if the output difference obtained by subtracting the immediately preceding output setting value from the current output setting value is relatively small, the integrated value is likely to reach the integrated threshold value. This increases the frequency with which the purge valve 15 opens. On the other hand, when the additional value is set to a value corresponding to the operation time of the fuel cell 2, the initial value of the integrated value can be set to a small value. This makes it possible to prevent the integrated value from excessively reaching the integrated threshold value when the integrated value is closer to the initial value than the integrated threshold value and the output difference is relatively small. This makes it possible to prevent the purge valve 15 from excessively opening.

[0075] Here, an example has been described in which the initial value or the additional value of the integrated value is set in accordance with the operation time of the fuel cell 2. However, the integrated threshold value may also be set in accordance with the operation time of the fuel cell 2.

[0076] In the above-described embodiment, the set value determination unit 34 determines whether the current output set value has changed from the immediately preceding output set value. However, the embodiment is not limited to this. For example, the set value determination unit 34 may determine that the output set value has not changed when the current output set value is decreased from the immediately preceding output set value. This can suppress a decrease in the hydrogen concentration. More specifically, the set value determination unit 34 determines whether the current output set value has increased from the immediately preceding output set value. When the set value determination unit 34 determines that the output set value has increased, the adder 35 adds the output difference to the integrated value, and when the set value determination unit 34 determines that the output set value has not increased, the adder 35 adds a predetermined addition value to the integrated value.

[0077] According to the embodiment described above, it is possible to improve the power generation efficiency, and even if the fuel cell 2 deteriorates, it is possible to continue stable operation of the fuel cell 2.

[0078] Although some embodiments of the present invention have been described, these embodiments are presented as examples and are not intended to limit the scope of the invention. These novel embodiments can be implemented in various other forms, and various omissions, substitutions, and modifications can be made without departing from the gist of the invention. These embodiments and their modifications are included in the scope and gist of the invention, and are included in the scope of the invention and its equivalents described in the claims. In addition, it is of course possible to combine these embodiments in part as appropriate within the gist of the present invention. [Explanation of symbols]

[0079] 1: fuel cell system, 2: fuel cell, recycle line 6, purge valve 15, control device 20, 31: initialization unit, 33: set value acquisition unit, 34: set value determination unit, 35: addition unit, 36: integrated value determination unit, 37: purge valve control unit

Claims

1. A control device for a fuel cell system including a purge valve for controlling discharge to the outside of a fuel off-gas discharged from a fuel cell to a recycle line, an initialization unit that initializes the integrated value; a set value acquisition unit that acquires an output set value of the fuel cell; a set value determination unit that determines whether the output set value acquired by the set value acquisition unit has changed from the output set value acquired immediately before; an adding unit that, when it is determined that the output setting value has changed, adds an output difference obtained by subtracting the immediately preceding output setting value from the current output setting value to the integrated value, and, when it is determined that the output setting value has not changed, adds a predetermined additional value to the integrated value; an integrated value determination unit that determines whether the integrated value to which the output difference or the additional value has been added has reached a predetermined integrated threshold value; a purge valve control unit that opens the purge valve for a predetermined time when it is determined that the integrated value has reached the integrated threshold value; A control device for a fuel cell system comprising:

2. The initialization unit initializes the integrated value when it is determined that the integrated value has reached the integration threshold value. The control device for a fuel cell system according to claim 1 .

3. The initialization unit initializes the integrated value at a timing when the purge valve control unit opens the purge valve. The control device for a fuel cell system according to claim 2 .

4. The set value determination unit determines that the output set value has not changed when the absolute value of the output difference is smaller than a predetermined output threshold value. The control device for a fuel cell system according to claim 1 or 2.

5. While the purge valve is open, the adding unit does not perform an addition process to the integrated value. The control device for a fuel cell system according to claim 1 or 2.

6. the integrated value determination unit sets the integrated threshold value so as to become smaller as the output setting value increases; The control device for a fuel cell system according to claim 1 or 2.

7. the integrated value determination unit sets the integrated threshold value so as to become smaller as the power generation output value of the fuel cell increases; The control device for a fuel cell system according to claim 1 or 2.

8. the initialization unit sets an initial value of the integrated value so that the initial value increases as the operation time of the fuel cell increases. The control device for a fuel cell system according to claim 1 or 2.

9. the adding unit sets the additional value so that the additional value becomes larger as the operation time of the fuel cell becomes longer. The control device for a fuel cell system according to claim 1 or 2.

10. the set value determination unit determines that the output set value has not changed when the current output set value is lower than the immediately preceding output set value; The control device for a fuel cell system according to claim 1 or 2.

11. A fuel cell; a recycle line for returning fuel off-gas discharged from the fuel cell to the fuel cell; a purge valve for controlling discharge of the fuel off-gas flowing through the recycle line to the outside; A control device for a fuel cell system according to claim 1 or 2; A fuel cell system comprising:

12. A method for controlling a fuel cell system having a purge valve for controlling discharge to the outside of a fuel off-gas discharged from a fuel cell to a recycle line, comprising the steps of: A step of initializing an integrated value; obtaining a power setting value for the fuel cell; determining whether the acquired output setting value has changed from the output setting value acquired immediately before; a step of adding an output difference obtained by subtracting the immediately preceding output setting value from the current output setting value to an integrated value when it is determined that the output setting value has changed, and adding a predetermined additional value to the integrated value when it is determined that the output setting value has not changed; determining whether or not the output difference or the integrated value to which the additional value has been added has reached a predetermined integration threshold; opening a purge valve for a predetermined time when it is determined that the integrated value has reached an integrated threshold value; A method for controlling a fuel cell system comprising the steps of:

13. A control program for a fuel cell system for causing a computer to execute a control method for a fuel cell system having a purge valve for controlling discharge to the outside of a fuel off-gas discharged from a fuel cell to a recycle line, the control program comprising: The method for controlling a fuel cell system includes: A step of initializing an integrated value; obtaining a power setting value for the fuel cell; determining whether the acquired output setting value has changed from the output setting value acquired immediately before; a step of adding an output difference obtained by subtracting the immediately preceding output setting value from the current output setting value to an integrated value when it is determined that the output setting value has changed, and adding a predetermined additional value to the integrated value when it is determined that the output setting value has not changed; determining whether or not the output difference or the integrated value to which the additional value has been added has reached a predetermined integration threshold; opening a purge valve for a predetermined time when it is determined that the integrated value has reached an integrated threshold value; A control program for a fuel cell system comprising:

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