Control method for a fuel cell device, and control device for a fuel cell device.

Abstract

This invention provides a control method for a fuel cell system that can suppress the decrease in power generation efficiency compared to conventional methods. [Solution] The control method for a fuel cell system is a control method for a fuel cell system including a plurality of fuel cell units, wherein when increasing the number of power generation units in order to increase the output of the fuel cell system, the fuel cell units to be started generating power are selected in order of decreasing degradation.

Description

Technical Field

[0001] The present disclosure relates to a method for controlling a fuel cell device and a control device for a fuel cell device.

Background Art

[0002] The following Patent Document 1 discloses a fuel cell system that increases the overall power generation efficiency by selecting and using fuel cells in descending order of power generation efficiency from among a plurality of fuel cells.

Prior Art Document

Patent Document

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] However, in the above prior art, in a fuel cell device including a plurality of fuel cell units, sufficient consideration has not been given to suppressing a decrease in power generation efficiency.

[0005] An object of the present disclosure is to provide a method for controlling a fuel cell device and a control device for a fuel cell device that can suppress a decrease in power generation efficiency more effectively than in the prior art in a fuel cell device including a plurality of fuel cell units.

Means for Solving the Problems

[0006] To solve the above problems, a method for controlling a fuel cell device according to one aspect of the present disclosure is a method for controlling a fuel cell device including a plurality of fuel cell units, and when increasing the number of fuel cell units in operation for increasing the output of the fuel cell device, it selects the fuel cell units to start power generation in descending order of the degree of deterioration.

[0007] Furthermore, a control device for a fuel cell system according to one aspect of the present disclosure is a control device for a fuel cell system including a plurality of fuel cell units, comprising: a memory for storing the degree of degradation of each of the plurality of fuel cell units; and a controller for selecting the fuel cell units to start generating power in order of decreasing degradation when increasing the number of power-generating fuel cell units in order to increase the output of the fuel cell system. [Effects of the Invention]

[0008] A control method for a fuel cell device and a control device for a fuel cell device according to one aspect of this disclosure have the effect of being able to suppress the decrease in power generation efficiency of the fuel cell device more effectively than conventional methods. [Brief explanation of the drawing]

[0009] [Figure 1] Figure 1 is a block diagram of the control device and fuel cell system. [Figure 2] Figure 2 is a flowchart of the power generation control program. [Figure 3] Figure 3 is a graph showing the simulation results regarding the degradation of the fuel cell system. [Modes for carrying out the invention]

[0010] In fuel cell systems containing multiple fuel cell units, the number of fuel cell units selected to supply electricity according to the customer's electricity demand is determined and power is generated. It was generally believed that if power generation was repeatedly concentrated on certain fuel cell units, differences in the degree of degradation (hereinafter referred to as "degradation") would occur among them. Therefore, conventionally, to ensure that the number of power generation cycles and power generation time were equal for each fuel cell unit, priority was given to selecting fuel cell units with fewer power generation cycles or shorter power generation times. In other words, fuel cell units with a low degree of degradation were used preferentially. Furthermore, the method of using fuel cell units in order of highest power generation efficiency, as described in Patent Document 1 above, is another example of prioritizing the use of fuel cell units with a low degree of degradation. Thus, in conventional fuel cell systems, it was common practice to prioritize the use of fuel cell units with a "low" degree of degradation.

[0011] However, after diligent research by the inventors, it was discovered that, contrary to conventional wisdom, prioritizing the use of fuel cell units with a "high" degree of degradation can suppress the overall decrease in power generation efficiency of the fuel cell system. This is because, while the decrease in power generation efficiency due to degradation is rapid in the initial stages of degradation, the decrease becomes more gradual once the degradation progresses to a certain extent. Therefore, by prioritizing the use of fuel cell units with a high degree of degradation, where the decrease in power generation efficiency is gradual, the decrease in power generation efficiency of the fuel cell system can be suppressed.

[0012] Therefore, the control method for a fuel cell system according to the first aspect of this disclosure is a control method for a fuel cell system including a plurality of fuel cell units, wherein when increasing the number of power generation units of the fuel cell system in order to increase the output of the fuel cell system, the fuel cell units to be started generating power are selected in order of decreasing degradation.

[0013] In this control method, when increasing the number of fuel cell units used for power generation, the system selects fuel cell units with a higher degree of degradation, thus prioritizing the use of these units. Therefore, this control method can suppress the decrease in the power generation efficiency of the fuel cell system.

[0014] The control method of the fuel cell device according to the second aspect of the present disclosure is the control method of the fuel cell device according to the first aspect, and when reducing the number of power generation units of the fuel cell unit due to the output decrease of the fuel cell device, the fuel cell units to be stopped from generating power are selected in ascending order of the degree of degradation.

[0015] In this control method, when reducing the number of power generation units of the fuel cell unit, since fuel cell units with a low degree of degradation are selected, fuel cell units with a high degree of degradation will be preferentially used. Therefore, according to this control method, a decrease in the power generation efficiency of the fuel cell device can be suppressed.

[0016] The control method of the fuel cell device according to the third aspect of the present disclosure is the control method of the fuel cell device according to the first or second aspect, and the degree of degradation is determined based on the voltage during power generation of the fuel cell unit.

[0017] In this control method, since the degree of degradation of the fuel cell unit is determined based on the voltage during power generation, the degree of degradation of the fuel cell unit can be clearly determined.

[0018] The control method of the fuel cell device according to the fourth aspect of the present disclosure is the control method of the fuel cell device according to the first or second aspect, and the degree of degradation is determined based on the cumulative power generation time of the fuel cell unit.

[0019] In this control method, since the degree of degradation of the fuel cell unit is determined based on the cumulative power generation time, the degree of degradation of the fuel cell unit can be clearly determined.

[0020] The control method of the fuel cell device according to the fifth aspect of the present disclosure is the control method of the fuel cell device according to the first or second aspect, and the degree of degradation is determined based on the cumulative number of power generation times of the fuel cell unit.

[0021] In this control method, since the degree of degradation of the fuel cell unit is determined based on the cumulative number of power generation times, the degree of degradation of the fuel cell unit can be clearly determined.

[0022] The control method of the fuel cell device according to the sixth aspect of the present disclosure is the control method of the fuel cell device according to the first or second aspect, wherein the degree of deterioration is determined based on a mathematical formula using at least one of the voltage during power generation of the fuel cell unit, the cumulative power generation time of the fuel cell unit, and the number of power generation times of the fuel cell unit.

[0023] In this control method, since the degree of deterioration of the fuel cell unit is determined based on a mathematical formula using at least one of the voltage during power generation, the cumulative power generation time, and the cumulative number of power generation times, the degree of deterioration of the fuel cell unit can be determined from a comprehensive perspective.

[0024] The control device of the fuel cell device according to the seventh aspect of the present disclosure is a control device of a fuel cell device including a plurality of fuel cell units, and includes a storage device that stores the degree of deterioration of each of the plurality of fuel cell units, and a controller that selects a fuel cell unit to start power generation in descending order of the degree of deterioration when increasing the number of power generation units of the fuel cell unit for increasing the output of the fuel cell device.

[0025] In this control device, when increasing the number of power generation units of the fuel cell unit, since a fuel cell unit with a high degree of deterioration is selected, a fuel cell unit with a high degree of deterioration will be preferentially used. Therefore, according to this control device, a decrease in the power generation efficiency of the fuel cell device can be suppressed.

[0026] The control device of the fuel cell device according to the eighth aspect of the present disclosure is the control device of the fuel cell device according to the seventh aspect, wherein when decreasing the number of power generation units of the fuel cell unit due to a decrease in the output of the fuel cell device, the controller selects the fuel cell unit to stop power generation in ascending order of the degree of deterioration. <​​​

[0028] The following describes specific examples of the above embodiments of this disclosure with reference to the attached drawings. The specific examples described below are all examples of the above embodiments of this disclosure. Therefore, the shapes, numerical values, components, arrangement positions of components, and connection configurations shown below do not limit the scope of the claims unless they are described in the claims.

[0029] Furthermore, among the components described below, those not described in the independent claim representing the highest-level concept of this disclosure will be described as optional components. Also, in the drawings, components with the same reference numeral may not be described. The drawings are schematic representations of each component for ease of understanding, and the shape and dimensional ratios may not be accurately represented.

[0030] Furthermore, in the operation of the apparatus, the order of the processes may be changed or known processes may be added as needed.

[0031] (Fuel cell device) First, the device configuration of the fuel cell device 101, which is controlled by the control device 10 according to this embodiment, will be described. Figure 1 is a block diagram of the control device 10 and the fuel cell device 101. The fuel cell device 101 is a device that generates electricity using a fuel cell. As shown in Figure 1, the fuel cell device 101 has a plurality of fuel cell units 102. The number of fuel cell units 102 that the fuel cell device 101 has is not limited, but the fuel cell device 101 may have, for example, several to several hundred fuel cell units 102.

[0032] The fuel cell unit 102 can generate electricity by chemically reacting a fuel such as hydrogen or methanol with an oxidizer such as oxygen. The energy of the electricity generated by the fuel cell unit 102 is supplied to the consumer 103. The consumer 103 is, for example, a home, a shop, or a factory. The fuel cell unit 102 deteriorates with use, and as the usage time and number of uses of each fuel cell unit 102 increase, slight differences in the degree of deterioration will occur among the fuel cell units 102. Therefore, the fuel cell system 101 will have multiple fuel cell units 102 with different degrees of deterioration.

[0033] (Control device) Next, the device configuration of the control device 10 according to this embodiment will be described. The control device 10 is a device that controls the fuel cell device 101. The control device 10 has a processor, volatile memory, non-volatile memory, and an I / O interface, etc. Various programs, including a power generation control program which will be described later, are stored in the non-volatile memory of the control device 10, and the processor performs calculation processing using the volatile memory based on each program.

[0034] The control device 10 may consist of one device or multiple devices. For example, the control device 10 may consist of multiple devices connected by a network.

[0035] As shown in Figure 1, the control device 10 of this embodiment includes a controller 11 and a memory 12.

[0036] Controller 11 is a device that performs calculation processing. Controller 11 may be, for example, the processor of control device 10. Controller 11 is communicatively connected to each fuel cell unit 102. Controller 11 can start power generation in a fuel cell unit 102 that is stopped by sending a power generation instruction signal to that fuel cell unit 102. Controller 11 can also stop power generation in a fuel cell unit 102 that is generating power by sending a stop instruction signal to that fuel cell unit 102. Note that fuel cell unit 102 has a built-in controller (not shown), and when it receives a power generation instruction signal from controller 11, the controller of fuel cell unit 102 starts power generation in fuel cell unit 102. Also, when the controller of fuel cell unit 102 receives a stop instruction signal from controller 11, it stops power generation in fuel cell unit 102.

[0037] Furthermore, the controller 11 can acquire power generation information from each fuel cell unit 102. The power generation information in this embodiment includes, for example, the voltage during power generation, cumulative power generation time, and cumulative number of power generation cycles of the fuel cell unit 102. Based on the power generation information, the controller 11 can calculate or determine the degree of deterioration of each fuel cell unit 102 and store it in the memory 12. The power generation information of the fuel cell unit 102 is transmitted by the controller of the fuel cell unit 102 via a communication device (not shown) of the fuel cell unit 102.

[0038] For example, the controller 11 may determine the degree of degradation based on the voltage generated by the fuel cell unit 102, the cumulative power generation time of the fuel cell unit 102, or the cumulative number of power generation cycles of the fuel cell unit 102. The controller 11 may determine that the lower the voltage generated by the fuel cell unit 102, the higher the degree of degradation; the longer the cumulative power generation time of the fuel cell unit 102, the higher the degree of degradation; or the more cumulative power generation cycles of the fuel cell unit 102, the higher the degree of degradation.

[0039] Alternatively, the degree of degradation may be calculated based on a formula using at least one of the following: the voltage of the fuel cell unit 102 during power generation, the cumulative power generation time of the fuel cell unit 102, and the cumulative number of power generation cycles of the fuel cell unit 102. For example, if the voltage of the fuel cell unit 102 during power generation is V, the cumulative power generation time of the fuel cell unit 102 is T, and the cumulative number of power generation cycles of the fuel cell unit 102 is C, the degree of degradation may be calculated based on the following polynomial. However, instead of V, which is the voltage of the fuel cell unit 102 during power generation, ΔV, which is the difference voltage obtained by subtracting the initial power generation voltage from the current power generation voltage of the fuel cell unit 102, may be used. Deterioration degree = -α×V+β×T+γ×C

[0040] In the above polynomial, α is the weighting coefficient for the voltage generated by the fuel cell unit 102, β is the weighting coefficient for the cumulative power generation time of the fuel cell unit 102, and γ is the weighting coefficient for the cumulative number of power generation cycles of the fuel cell unit 102. However, α + β + γ = 1.

[0041] Furthermore, the controller 11 is connected to the customer 103 (more precisely, to the control device and other equipment installed by the customer 103) in a communication manner. The controller 11 can obtain power demand from the customer 103. Power demand is the amount of power required by the customer 103. Note that the power demand of the customer 103 fluctuates depending on the circumstances of the customer 103. In addition, the controller 11 obtains actual power demand values ​​from the customer 103, and can also calculate predicted power demand values ​​based on these actual power demand values. In the following explanation, power demand may be an actual value or a predicted value.

[0042] The memory unit 12 is a device that stores various types of information. The memory unit 12 may be, for example, the volatile memory or non-volatile memory of the control device 10. The memory unit 12 is communicated with the controller 11. Therefore, the controller 11 can obtain the degree of degradation of each fuel cell unit 102 stored in the memory unit 12 from the memory unit 12.

[0043] (Control method for fuel cell systems) Next, the control method for the fuel cell device 101 will be described. In this embodiment, the controller 11 controls the fuel cell device 101 by executing a power generation control program. Figure 2 is a flowchart of the power generation control program. As shown in Figure 2, when the power generation control program is started, the controller 11 obtains the degradation level of each fuel cell unit 102 from the memory 12 (step S1). As mentioned above, in this embodiment, the controller 11 has predetermined or calculated the degradation level of each fuel cell unit 102 and stored it in the memory 12.

[0044] Next, the controller 11 calculates the required number of power generators (step S2). The required number of power generators refers to the minimum number of fuel cell units 102 whose total generated power exceeds the demand power of the customer 103. The required number of power generators can be calculated based on the demand power of the customer 103 and the rated power generation power of the fuel cell units 102.

[0045] Next, the controller 11 determines whether the required number of power generators calculated in step S2 is equal to the current number of power generators (step S3). The current number of power generators is the number of fuel cell units 102 that are generating power at the time of the determination in step S3 (total number of power generators).

[0046] If the controller 11 determines in step S3 that the required number of power generators is equal to the current number of power generators (YES in step S3), that is, if there is no need to increase the number of power generators of the fuel cell unit 102 to increase the output (power generated) of the fuel cell device 101, nor is there a need to decrease the number of power generators of the fuel cell unit 102 to decrease the output of the fuel cell device 101, then it returns to step S1 and repeats each step from step S1 onward.

[0047] On the other hand, if the controller 11 determines in step S3 that the required number of power generators is not equal to the current number of power generators (YES in step S3), it determines whether the required number of power generators is greater than the current number of power generators (step S4). In other words, in step S4, the controller 11 determines whether it is necessary to increase the number of power generators of the fuel cell unit 102 to increase the output of the fuel cell device 101.

[0048] In step S4, if the controller 11 determines that the required number of power generators is greater than the current number of power generators (YES in step S4), that is, if it determines that it is necessary to increase the number of power generators of the fuel cell unit 102 to increase the output of the fuel cell device 101, it calculates the number of additional power generators (step S5). The number of additional power generators refers to the minimum number of fuel cell unit 102 that will require additional power generation in order for the power generated by the fuel cell device 101 to meet the electricity demand of the consumer 103. The number of additional power generators can be calculated, for example, by subtracting the current number of power generators from the required number of power generators.

[0049] After performing step S5, the controller 11 extracts a fuel cell unit 102 that is currently not generating power but is capable of generating power (step S6). In other words, the controller 11 extracts a fuel cell unit 102 from among the multiple fuel cell units 102 of the fuel cell device 101 that is not malfunctioning and can start generating power.

[0050] After performing step S6, the controller 11 selects the fuel cell units 102 extracted in step S6, starting with those with the highest degree of degradation, for the number of additional power generators, and sends a power generation instruction to the selected fuel cell units 102 (step S7). As a result, power generation begins in the fuel cell units 102 to which the power generation instruction has been sent, and the fuel cell device 101 can supply power to the customer 103 according to the customer's power demand. After performing step S7, the controller 11 returns to step S1 and repeats each step from step S1 onward.

[0051] As described above, when the controller 11 of this embodiment increases the number of power generation units 102 in order to increase the output of the fuel cell device 101, it selects the fuel cell units 102 in order of their degree of deterioration and starts power generation. Therefore, according to the above control method, fuel cell units 102 with a high degree of deterioration will be used preferentially.

[0052] On the other hand, if the controller 11 determines in step S4 that the required number of power generators is not greater than the current number of power generators (NO in step S4), that is, if it determines that it is acceptable to reduce the number of power generators of the fuel cell unit 102 and thereby reduce the output of the fuel cell device 101, it calculates the number of power generators to be reduced (step S8). The number of power generators to be reduced refers to the number of fuel cell units 102 that can be reduced while the power generated by the fuel cell device 101 meets the demand of the consumer 103. The number of power generators to be reduced can be calculated, for example, by subtracting the required number of power generators from the current number of power generators.

[0053] After performing step S8, the controller 11 extracts the fuel cell units 102 that are currently generating power (step S9). In other words, it extracts the fuel cell units 102 that can be stopped generating power.

[0054] After performing step S9, the controller 11 selects fuel cell units 102 from those extracted in step S9, in order of decreasing degradation level, corresponding to the number of reduced power generation units calculated in step S8, and sends a stop instruction to the selected fuel cell units 102 (step S7). As a result, the fuel cell units 102 to which the stop instruction has been sent will stop generating power, thereby suppressing unnecessary power generation by the fuel cell device 101. After performing step S7, the controller 11 returns to step S1 and repeats each step from step S1 onward.

[0055] As described above, when the controller 11 of this embodiment reduces the number of power generation units 102 due to a decrease in the output of the fuel cell device 101, it selects and stops the fuel cell units 102 that have the lowest degree of degradation to start generating power. Therefore, according to the above control method, fuel cell units 102 with a high degree of degradation will be used preferentially. The above is a description of the flow of the power generation control program.

[0056] Thus, in this embodiment, when the controller 11 controls the fuel cell system 101, it preferentially uses the fuel cell unit 102 with a high degree of degradation. Here, in the initial stages of degradation, the power generation efficiency of the fuel cell unit 102 decreases rapidly, but as the degradation progresses to a certain extent, the decrease in power generation efficiency due to degradation becomes more gradual. Therefore, as in this embodiment, by preferentially using the fuel cell unit 102 with a high degree of degradation, where the decrease in power generation efficiency is gradual, the decrease in the power generation efficiency of the fuel cell system 101 can be suppressed.

[0057] (Simulation results) Next, we will explain the simulation results regarding the degradation of the fuel cell unit 101. Figure 3 is a graph showing the simulation results of the output maintenance rate after 100,000 hours of use of the fuel cell unit 101. The horizontal axis of Figure 3 represents the output maintenance rate of the fuel cell unit 101 after 100,000 hours of use. Here, the output maintenance rate refers to the maintenance rate of the power generation efficiency of the fuel cell unit 101. Specifically, power generation efficiency = output voltage of the fuel cell unit * a (where a is a coefficient), and the output maintenance rate is calculated as: average power generation efficiency of all fuel cell units after 100,000 hours / average power generation efficiency of all fuel cell units at the beginning. Therefore, the higher the output maintenance rate of the fuel cell unit 101 after 100,000 hours of use, the less degradation (in other words, the less the power generation efficiency has decreased) of the fuel cell unit 101. The vertical axis of Figure 3 represents the average power generation efficiency of the fuel cell unit 101 over 100,000 hours. Specifically, the average power generation efficiency is calculated by dividing the sum of the average power generation efficiencies of each fuel cell unit 102 within the fuel cell system 101 over 100,000 hours by the total number of fuel cell units in the fuel cell system. However, the method for calculating the average power generation efficiency is not limited to this, and it may also be the sum of weighted values ​​of the average power generation efficiency of each fuel cell unit 102 over 100,000 hours. This weighting may be calculated as the cumulative power generation amount of each fuel cell unit 102 over 100,000 hours / the cumulative power generation amount of all fuel cell units 102 over 100,000 hours.

[0058] The three points enclosed by the dashed line in Figure 3 show the simulation results when the fuel cell device 101 is controlled using a conventional method, that is, when the fuel cell device 101 is controlled so that the degradation level of all fuel cell units 102 is uniform. Of the three points enclosed by the dashed line, the left point shows the result when the degradation level is determined and controlled by the voltage during power generation, the middle point shows the result when the degradation level is determined and controlled by the cumulative power generation time, and the right point shows the result when the degradation level is determined and controlled by the cumulative number of power generation cycles.

[0059] The horizontal axis values ​​in Figure 3 represent the output maintenance rate of the fuel cell device 101 after 100,000 hours of use, with 100% being the result of controlling the fuel cell device 101 using a conventional method where the degradation level is determined by the cumulative power generation time. Furthermore, the horizontal axis values ​​in Figure 3 represent the average power generation efficiency of the fuel cell device 101 over 100,000 hours, with 100% being the result of controlling the fuel cell device 101 using a conventional method where the degradation level is determined by the cumulative power generation time.

[0060] On the other hand, the three points enclosed by the dashed lines in Figure 3 show the simulation results when the fuel cell device 101 is controlled using the method according to this embodiment, that is, when the fuel cell device 101 with a high degree of degradation is used preferentially. Of the three points enclosed by the dashed lines, the left point shows the result when the degradation degree is determined by the cumulative number of power generation cycles and control is performed, the middle point shows the result when the degradation degree is determined by the cumulative power generation time and control is performed, and the right point shows the result when the degradation degree is determined by the voltage during power generation and control is performed.

[0061] As can be seen from the simulation results shown in Figure 3, when the fuel cell device 101 is controlled using the control method according to this embodiment, that is, when the fuel cell device 101 is controlled to prioritize the use of fuel cell devices 101 with a high degree of degradation, the average power generation efficiency over 100,000 hours is lower compared to when the fuel cell device 101 is controlled using a conventional control method, but the output maintenance rate after 100,000 hours of use is higher. In other words, when the fuel cell device 101 is controlled using the control method according to this embodiment, the power generation efficiency during power generation operation of the fuel cell device 101 is lower compared to when the fuel cell device 101 is controlled using a conventional control method, but the maintenance rate of the power generation efficiency as a capacity of the fuel cell device 101 is higher. Therefore, it can be understood that the decrease in the power generation efficiency of the fuel cell device 101 can be suppressed according to the control method according to this embodiment.

[0062] From the above description, many improvements and other embodiments of the disclosure will be apparent to those skilled in the art. Therefore, the above description should be construed as illustrative only and is provided for the purpose of teaching those skilled in the art the best mode of carrying out the disclosure. The details of its structure and / or function can be substantially modified without departing from the spirit of the disclosure. [Industrial applicability]

[0063] One aspect of this disclosure can be used in a control method for a fuel cell device that can suppress the decrease in power generation efficiency compared to conventional methods, and in a control device for a fuel cell device. [Explanation of Symbols]

[0064] 10: Control device 11: Controller 12: Memory device 101:Fuel cell device 102: Fuel cell unit 103: Consumer

Claims

1. A control method for a fuel cell system including multiple fuel cell units, A control method for a fuel cell system, in which, when increasing the number of power generation units of the fuel cell system in order to increase the output of the fuel cell system, the fuel cell units to be started generating power are selected in order of decreasing degradation.

2. A control method for a fuel cell device according to claim 1, wherein when the number of power generation units of the fuel cell device is reduced due to a decrease in the output of the fuel cell device, the fuel cell units to be stopped generating power are selected in order of decreasing degree of deterioration.

3. The control method for a fuel cell device according to claim 1 or 2, wherein the degree of degradation is determined based on the voltage of the fuel cell unit during power generation.

4. The control method for a fuel cell device according to claim 1 or 2, wherein the degree of degradation is determined based on the cumulative power generation time of the fuel cell unit.

5. The control method for a fuel cell device according to claim 1 or 2, wherein the degree of degradation is determined based on the cumulative number of power generation cycles of the fuel cell unit.

6. The control method for a fuel cell device according to claim 1 or 2, wherein the degree of degradation is determined based on a formula using at least one of the voltage of the fuel cell unit during power generation, the cumulative power generation time of the fuel cell unit, and the number of power generation cycles of the fuel cell unit.

7. A control device for a fuel cell system including multiple fuel cell units, A memory device that stores the degree of degradation of each of the aforementioned multiple fuel cell units, A control device for a fuel cell system, comprising: a controller that, when increasing the number of power generation units of the fuel cell system in order to increase the output of the fuel cell system, selects the fuel cell units to start generating power in order of decreasing degradation.

8. The control device for a fuel cell device according to claim 7, wherein when the number of power generation units of the fuel cell device is reduced due to a decrease in the output of the fuel cell device, the controller selects the fuel cell units to be stopped generating power in order of decreasing degree of deterioration.

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