JP7477808B1 - Fuel Cell Power Generation System - Google Patents

Abstract

[Problem] To provide a fuel cell power generation system capable of suppressing deterioration in the performance of a fuel cell. [Solution] The fuel cell power generation system includes a fuel cell and a control device that permits a low load state of the fuel cell when a first condition is met, and transitions the load state of the fuel cell from an abnormally low load state when a second condition different from the first condition is met. [Selected Figure] Figure 6

Description

This disclosure relates to a fuel cell power generation system.

If the fuel cell voltage is maintained at a high potential while the fuel cell is not generating electricity, deterioration of the electrode catalyst is accelerated. Therefore, a technique is known for preventing the fuel cell from becoming a high potential and suppressing electrode catalyst deterioration (see, for example, Patent Document 1).

JP 2019-079657 A

A decrease in fuel cell performance due to deterioration of the electrode catalyst can be caused by a high potential when the fuel cell is in a low-load state. On the other hand, the performance of the fuel cell can be restored by temporarily switching the fuel cell to a low-load state. In this way, the performance of a fuel cell can decrease or recover depending on the low-load state of the fuel cell.

This disclosure provides a fuel cell power generation system that can suppress deterioration of fuel cell performance.

As one aspect of the present disclosure,
A fuel cell;
A fuel cell power generation system is provided, comprising: a control device that allows a low load state of the fuel cell when a first condition is satisfied, and transitions the load state of the fuel cell from an abnormally low load state when a second condition different from the first condition is satisfied.

According to one aspect of the present disclosure, when the first condition is met, a low load state of the fuel cell is permitted. As a result, when the first condition is met, it is possible to transition the fuel cell to a low load state, and by temporarily transitioning the fuel cell to a low load state, the performance degradation of the fuel cell is restored. On the other hand, when the second condition is met, the load state of the fuel cell transitions from an abnormal low load state. As a result, when the second condition is met, the fuel cell does not continue in an abnormal low load state, and the performance degradation of the fuel cell due to the continuation of the low load state is suppressed. Thus, according to one aspect of the present disclosure, the low load state of the fuel cell is appropriately controlled, and the performance degradation of the fuel cell is suppressed.

This disclosure provides a fuel cell power generation system that can suppress deterioration of fuel cell performance.

1 is a diagram showing a first configuration example of a fuel cell power generation system; FIG. 11 is a diagram showing a second configuration example of a fuel cell power generation system. 4 is a timing chart for explaining a first condition (permission condition) and a second condition (abnormal condition). 11 is a table illustrating types of flags (permission flags) that permit a low load state; 11 is a table illustrating types of flags (abnormality flags) for determining an abnormally low load state. 11A to 11C are diagrams illustrating a number of examples of processing that is performed after the load state of the fuel cell is determined to be an abnormally low load state. FIG. 11 is a diagram illustrating an example of a sequence for determining an abnormally low load state. FIG. 11 is a diagram illustrating an example of a sequence for permitting a low load state. 10 is a flowchart showing an example of control processing executed by each of a first control device and a second control device in a second configuration example of a fuel cell power generation system. 5 is a flowchart showing an example of a command generating process executed by a first control device. 10 is a flowchart showing an example of a control process during a refresh operation. 10 is a flowchart showing an example of a setting process for a refresh operation machine. 10 is a flowchart showing an example of a refresh operation process. 11 is a diagram illustrating a state in which power supplied to the outside is maintained constant; FIG. FIG. 11 is a diagram showing a first example of an implementation pattern of a refresh operation when four power generation devices are connected in parallel. 1 is a table illustrating an example of the relationship between the number of power generation devices connected in parallel and the output power of the power generation devices. 13 is data showing an example of a range of the number of parallel units suitable for the case where the refresh operation is used. FIG. 1 is a diagram showing a specific configuration example of a fuel cell power generation system. FIG. 2 is a diagram showing in detail a specific configuration example of a fuel cell power generation system.

The following describes an embodiment. In the following description, "constant" may include "almost constant." "Rated output" may be replaced with "maximum output." "Temporarily" may mean "for a certain period of time or longer."

<Configuration example of fuel cell power generation system>
Fig. 1 is a diagram showing a first configuration example of a fuel cell power generation system. A fuel cell power generation system 400 shown in Fig. 1 is a system that supplies power generated by a FC (fuel cell) to an external device (not shown) that is a power supply target. Meanwhile, Fig. 2 is a diagram showing a second configuration example of a fuel cell power generation system. A fuel cell power generation system 401 shown in Fig. 2 is a system that supplies power generated by multiple FCs (fuel cells) connected in parallel to an external device (not shown) that is a power supply target.

The fuel cell power generation system 400 (Figure 1) can be considered as a fuel cell power generation system 401 (Figure 2) in which the number of power generation devices is one. Therefore, unless otherwise specified, the following description will focus on the fuel cell power generation system 401, and the description of the fuel cell power generation system 400 will be omitted or simplified by incorporating the contents of the description of the fuel cell power generation system 401.

In addition, in the fuel cell power generation system 400 (Figure 1), the control device is separated into a first control device 411 and a second control device 421. However, the control device may be configured as a single control device having both the functions of the first control device 411 and the second control device 421.

In addition, in Figures 1 and 2, the first control device 411 may be separated into multiple control devices, and the second control device 421 may also be separated into multiple control devices.

In FIG. 2, the fuel cell power generation system 401 includes multiple (four in this example) power generation devices 451, 452, 453, and 454, an auxiliary system 301, and a first control device 411. Hereinafter, the power generation devices 451, 452, 453, and 454 are also referred to as the power generation devices 451, etc.

The auxiliary system 301 is a peripheral system that assists the operation of the power generation device 451 and the like. The auxiliary system 301 includes, for example, a control power supply, a fuel system, an air supply system, an exhaust system, a purge system, and a cooler. The control power supply supplies power to the first control device 411. The fuel system supplies hydrogen or hydrogen-rich gas to the power generation device 451 and the like. The air supply system supplies air to the power generation device 451 and the like. The exhaust system exhausts exhaust gas from the power generation device 451 and the like. The purge system supplies an inert gas such as nitrogen to the fuel system. The cooler cools the power generation device 451 and the like. The auxiliary system 301 may include a power storage device 14. The power storage device 14 is an example of an auxiliary power supply connected to the output line 17 so as to be able to supply power. The output line 17 is a power line commonly connected to each power generation output terminal of the power generation device 451 and the like.

Each of the power generation devices 451 etc. generates power using a fuel cell and outputs the generated power. The power generation devices 451 etc. are connected in parallel to the output line 17. The number of multiple power generation devices connected in parallel is not limited to four, and may be two, three, or more than four.

The power generation devices 451 and the like have the same configuration. The power generation device 451 has a fuel cell 441, an auxiliary device 431, and a second control device 421. The power generation device 452 has a fuel cell 442, an auxiliary device 432, and a second control device 422. The power generation device 453 has a fuel cell 443, an auxiliary device 433, and a second control device 423. The power generation device 454 has a fuel cell 444, an auxiliary device 434, and a second control device 424.

The multiple fuel cells 441, 442, 443, 444 (hereinafter also referred to as fuel cells 441, etc.) are connected to a common output line 17 so that they can supply power. The fuel cells 441, etc. are devices that electrochemically convert the chemical energy of a fuel such as hydrogen into electrical energy. The fuel cells 441, etc. are, for example, polymer electrolyte fuel cells (PEFCs), but are not limited to this and may be other types of fuel cells such as phosphoric acid type.

The fuel cells 441, etc. are fitted with voltage sensors for detecting the voltages at their output terminals, and current sensors for detecting the output currents from their output terminals. The first control device 411 obtains the detection values of the voltages output from the fuel cells 441, etc. using the voltage sensors, and obtains the detection values of the currents output from the fuel cells 441, etc. using the current sensors. The first control device 411 detects the output powers p1, p2, p3, and p4 of the fuel cells 441, etc. using the detection values of the voltages and currents.

The power generated by the fuel cell 441, etc. (power generation device 451, etc.) is supplied to an external device (not shown) via the output line 17.

Auxiliary device 431 is a device that assists the power generation operation of the fuel cell 441 that corresponds to it among fuel cells 441, etc. Similar to auxiliary device 431, auxiliary devices 432, 433, and 434 are also devices that assist the power generation operation of the fuel cell that corresponds to them among fuel cells 441, etc.

The auxiliary equipment 431 includes, for example, an air compressor that compresses air and supplies it to the fuel cell 441, and a water pump that circulates a coolant between the heat exchanger and the fuel cell 441. The auxiliary equipment 431 may include the first cooling system 36 described below. The same applies to the auxiliary equipment 432, 433, and 434.

The first control device 411 is a higher-level controller that controls the operation of the power generation device 451, etc. and the auxiliary system 301. The first control device 411 individually generates command a (commands a1, a2, a3, a4) that instructs the operation of the power generation device 451, etc., and transmits them to each of the power generation devices 451, etc.

The first control device 411 determines the command values (output set values) of the output powers P1, P2, P3, and P4 of the power generation devices 451, etc., according to the power (required output power) required of the fuel cell power generation system 401 as the power to be output to the output line 17. The first control device 411 transmits a command a (commands a1, a2, a3, and a4) instructing the output set values of the output powers P1, P2, P3, and P4 to each of the power generation devices 451, etc.

The second control device 421 is a lower-level controller that controls the power generation of the fuel cell 441 by operating the auxiliary device 431 according to command a1 that indicates the operation of the power generation device 451. Like the second control device 421, the second control devices 422, 423, and 424 are lower-level controllers that control the operation of the fuel cell corresponding to them by operating the auxiliary device corresponding to them according to the command a (commands a2, a3, and a4) corresponding to them.

For example, the second control device 421 controls the power generation of the fuel cell 441 by operating the auxiliary device 431 so that the output power P1 of the power generation device 451 becomes the output set value instructed by command a1. The second control device 422 controls the power generation of the fuel cell 442 by operating the auxiliary device 432 so that the output power P2 of the power generation device 452 becomes the output set value instructed by command a2. The second control device 423 controls the power generation of the fuel cell 443 by operating the auxiliary device 433 so that the output power P3 of the power generation device 453 becomes the output set value instructed by command a3. The second control device 424 controls the power generation of the fuel cell 444 by operating the auxiliary device 434 so that the output power P4 of the power generation device 454 becomes the output set value instructed by command a4.

More specifically, the power conversion device 11, such as a PCS connected to the output line 17, controls the load current flowing through the output line 17 according to the load command output from each of the first control device 411 or the multiple second control devices 421. The second control device 421 controls the power generation of the fuel cell 441 so that the output power P1 of the power generation device 451 becomes the output set value specified by command a1 by operating the auxiliary device 431 so that the amount of air and the amount of hydrogen corresponding to the output current of the power generation device 451 are supplied to the fuel cell 441. The second control device 422 controls the power generation of the fuel cell 442 so that the output power P2 of the power generation device 452 becomes the output set value specified by command a2 by operating the auxiliary device 432 so that the amount of air and the amount of hydrogen corresponding to the output current of the power generation device 452 are supplied to the fuel cell 442. The second control device 423 controls the power generation of the fuel cell 443 so that the output power P3 of the power generation device 453 becomes the output set value instructed by command a3 by operating the auxiliary device 433 so that the amount of air and hydrogen corresponding to the output current of the power generation device 453 is supplied to the fuel cell 443. The second control device 424 controls the power generation of the fuel cell 444 so that the output power P4 of the power generation device 454 becomes the output set value instructed by command a4 by operating the auxiliary device 434 so that the amount of air and hydrogen corresponding to the output current of the power generation device 454 is supplied to the fuel cell 444.

A portion of the output power p1 of the fuel cell 441 is used as operating power for part or all of the auxiliary equipment 431, and the surplus power is output as output power P1 of the power generation device 451. The same applies to the output powers p2, p3, and p4.

The first control device 411 performs control to maintain the power supply from the output line 17 to the outside at a substantially constant predetermined value. For example, the first control device 411 controls the power generation of the fuel cell 441, etc. (the power generation device 451, etc.) so that the supply power Pa (=Po-Pb) output from the output line 17 is maintained at a constant target value (required output power). Po is the power between each power generation output terminal of the power generation device 451, etc. and the power storage device 14. Po is equal to the sum of the output powers P1, P2, P3, P4 of the power generation device 451, etc. (Po=P1+P2+P3+P4). Pb is the power exchanged between the power storage device 14 and the output line 17.

The first control device 411 may perform control (battery output fluctuation control) to change (more specifically, increase or decrease) the output powers p1, p2, p3, and p4 of the fuel cell 441, etc., so that the supply power Pa from the output line 17 to the outside is maintained at a constant required output power. The supply power Pa or the output power Po can be detected by a voltage sensor and a current sensor.

When performing battery output fluctuation control, the first control device 411 individually generates commands a (commands a1, a2, a3, a4) that change the output power of the fuel cell so that the power Pa supplied to the outside from the output line 17 is maintained at a constant required output power, and transmits these to each of the power generation devices 451, etc.

The second control device 421 changes the output power p1 of the fuel cell 441 by operating the auxiliary device 431 according to a command a1 generated so that the supply power Pa is maintained at a constant required output power. The second control device 422 changes the output power p2 of the fuel cell 442 by operating the auxiliary device 432 according to a command a2 generated so that the supply power Pa is maintained at a constant required output power. The second control device 423 changes the output power p3 of the fuel cell 443 by operating the auxiliary device 433 according to a command a3 generated so that the supply power Pa is maintained at a constant required output power. The second control device 424 changes the output power p4 of the fuel cell 444 by operating the auxiliary device 434 according to a command a4 generated so that the supply power Pa is maintained at a constant required output power.

More specifically, the second control device 421 operates the auxiliary device 431 so that the amount of air and hydrogen corresponding to the output current of the power generation device 451 is supplied to the fuel cell 441, thereby changing the output power p1 of the fuel cell 441 so that the output power P1 of the power generation device 451 becomes the output set value instructed by command a1. The second control device 422 operates the auxiliary device 432 so that the amount of air and hydrogen corresponding to the output current of the power generation device 452 is supplied to the fuel cell 442, thereby changing the output power p2 of the fuel cell 442 so that the output power P2 of the power generation device 452 becomes the output set value instructed by command a2. The second control device 423 operates the auxiliary device 433 so that the amount of air and hydrogen corresponding to the output current of the power generation device 453 is supplied to the fuel cell 443, thereby changing the output power p3 of the fuel cell 443 so that the output power P3 of the power generation device 453 becomes the output set value instructed by command a3. The second control device 424 operates the auxiliary device 434 so that an amount of air and an amount of hydrogen corresponding to the output current of the power generation device 454 are supplied to the fuel cell 444, thereby changing the output power p4 of the fuel cell 444 so that the output power P4 of the power generation device 454 becomes the output set value instructed by command a4.

By the first control device 411 performing the above-mentioned cell output fluctuation control, the output powers p1, p2, p3, and p4 of the fuel cell 441 and the like are increased or decreased while the power supply Pa from the output line 17 to the outside is maintained at a substantially constant value. As a result, while a constant power supply from the output line 17 to the outside is ensured, the humidity distribution imbalance in the cell surface of the fuel cell 441 and the like is reduced compared to the case where the output powers p1, p2, p3, and p4 are always controlled to be constant. By reducing the imbalance in the humidity distribution in the cell surface, the increase in current density due to the decrease in the effective reaction area is suppressed, and the deterioration of the electrolyte membrane due to the increase in current density is suppressed. Therefore, the first control device 411 performs the cell output fluctuation control to increase or decrease the output powers p1, p2, p3, and p4 so that the supply power Pa is maintained at a substantially constant value, thereby ensuring a substantially constant power supply and suppressing the deterioration of the fuel cell 441 and the like. Suppressing the deterioration of the fuel cell 441 and the like contributes to improving the durability of the fuel cell power generation system 401.

In general, a power generation system using a fuel cell is equipped with a control device for controlling operation stop, load change, and equipment (auxiliary equipment) other than the fuel cell. Since there is a limit to the power that can be output by a single fuel cell, multiple fuel cells must be operated in parallel to generate the output required by the system using a fuel cell. In addition, the required output differs depending on the product to which it is applied, so the number of fuel cells and the performance of the auxiliary equipment change according to the required output. Therefore, when controlling the entire system with a single control device, the content of the wide range of software, such as "load change and start/stop control of each fuel cell" and "calculation according to the overall output and command control to each auxiliary equipment", differs depending on the product to which it is applied. In addition, when performing the refresh operation described below, the content of the software, such as "schedule control of the refresh operation of each fuel cell", also differs depending on the product to which it is applied. In this way, when controlling the entire system with a single control device, there is a risk that the maintainability and functional scalability of the entire system will decrease because there is a limit to the content that can be implemented in a single control device.

In contrast, in the fuel cell power generation system 401 of this embodiment, the role of the first control device 411 is separated from the role of the second control devices 421, 422, 423, and 424. The second control devices 421, 422, 423, and 424, which are lower in rank than the first control device 411, control the power generation of the fuel cells assigned to them. For this reason, the control content of the second control device can be determined in advance at the design stage, etc. Therefore, even if the number of fuel cells increases, the same software can be used between multiple second control devices, improving the maintainability of the entire system. On the other hand, in the first control device 411, the software may be changed depending on the number of fuel cells and the performance of the auxiliary devices. However, since the lower second control device operates the auxiliary devices for controlling the power generation of the fuel cells, the range of changes to the software of the first control device is smaller than when one control device controls the entire system, improving the expandability of the function. For example, as shown in FIG. 2, by adding power generation devices 455 and 456 that include a second control device having the same software as other second control devices, together with the auxiliary devices and the fuel cells, it is possible to easily respond to an increase in the required output power for the fuel cell power generation system 401.

Power generation systems using fuel cells require stable performance (suppression of decline in power generation efficiency). Fuel cell performance declines due to degradation of the electrode catalyst, electrolyte membrane, and ionomer, so it is necessary to suppress this degradation. Of the declines in fuel cell performance, reversible performance declines in the electrolyte membrane can be recovered by a refresh operation (described below) in which the fuel cell temporarily transitions to a low-load state. On the other hand, declines in fuel cell performance due to thinning of the electrolyte membrane or degradation of the electrode catalyst are caused by an increase in the voltage when the fuel cell is in a low-load state. Thus, in order to suppress declines in fuel cell performance, it is necessary to appropriately control the low-load state of the fuel cell.

In the fuel cell power generation system 400 of this embodiment, the first control device 411 judges whether a first condition (hereinafter also referred to as a permission condition) including a condition for permitting a low load state of the fuel cell 441 of the power generation device 451 is satisfied. If the permission condition is satisfied, the first control device 411 permits the transition of the fuel cell 441 to a low load state by operating the auxiliary device 431, and if the permission condition is not satisfied, the first control device 411 prohibits the transition of the fuel cell 441 to a low load state. If the permission condition is satisfied, it is possible to transition the fuel cell 441 to a low load state. Therefore, the first control device 411 performs a refresh operation to temporarily transition the fuel cell 441 to a low load state, thereby recovering the performance degradation of the fuel cell 441. The first control device 411 similarly judges whether the permission condition is satisfied for the other fuel cells 442, etc., and performs a refresh operation to temporarily transition the fuel cell for which the permission condition is satisfied to a low load state. This recovers the performance degradation of the fuel cell.

On the other hand, the first control device 411 judges whether or not a second condition (hereinafter also referred to as an abnormal condition) is satisfied, which includes a condition for judging the load state of the fuel cell 441 to be an abnormal low-load state. If the abnormal condition is satisfied, the first control device 411 operates the auxiliary device 431, etc. to transition the load state of the fuel cell 441 from the abnormal low-load state. If the abnormal condition is not satisfied, the first control device 411 judges that the low-load state of the fuel cell 441 is not abnormal, and continues the low-load state of the fuel cell 441. If the abnormal condition is satisfied, the fuel cell 441 does not continue in the abnormal low-load state, so that the performance degradation of the fuel cell 441 due to the continuation of the low-load state is suppressed. The first control device 411 similarly judges whether or not the abnormal condition is satisfied for the other fuel cells 442, etc., and transitions the load state of the fuel cell for which the abnormal condition is satisfied from the abnormal low-load state. This suppresses the performance degradation of the fuel cell due to the continuation of the low-load state.

In this way, according to the fuel cell power generation system of this embodiment, the low load state of the fuel cell 441, etc. is appropriately controlled, so that the performance degradation of the fuel cell 441, etc. is suppressed.

The first control device 411 has logic for distinguishing between a low-load state when the performance of the fuel cell 441 is restored by temporarily transitioning the fuel cell 441 to a low-load state and an abnormal low-load state caused by an abnormality or operational error of the fuel cell power generation system. The first control device 411 monitors the operating state of the fuel cell 441, such as the load state, and operates with a control logic having a flag for permitting a low-load state (permission flag) and a flag for determining an abnormal low-load state (abnormal flag). This determines whether or not to permit a transition to a refresh operation that temporarily transitions the fuel cell 441 to a low-load state, and a system is constructed that does not allow the abnormal low-load state to continue. Therefore, by performing a refresh operation that temporarily transitions the fuel cell 441 to a low-load state, reversible performance degradation of the fuel cell 441 is restored, and performance degradation of the fuel cell 441 due to continued operation in an abnormal low-load state is suppressed.

The first control device 411 asserts the permission flag when the above permission conditions are met, and negates the permission flag when the above permission conditions are not met. The first control device 411 asserts the abnormality flag when the above abnormality conditions are met, and negates the abnormality flag when the above abnormality conditions are not met.

Figure 3 is a timing chart for explaining the first condition (permission condition) and the second condition (abnormal condition). Figure 3 illustrates an example in which the first control device 411 operates the fuel cell in a refresh operation that is performed in the order of a first high-load operation, an idling operation, and a second high-load operation. The first high-load operation is an operation that temporarily increases the output power of the fuel cell above a predetermined constant power value. The idling operation is an operation that temporarily puts the output power of the fuel cell into a low-load state. The second high-load operation is an operation that temporarily increases the output power of the fuel cell above a constant power value.

A low-load state refers to a state in which the output power of the fuel cell or the output power of the power generation device is zero or very low. For example, the low-load state may be an output state of 0% to 20% of the rated output of the fuel cell (rated value such as output power p1) or the rated output of the power generation device (rated value such as output power P1), an output state of 0% to 10%, or an output state of 0% to 5%. The low-load state may include a no-load state in which the output power of the fuel cell or the power generation device is zero. "No-load" in the drawings may be replaced with "low-load".

For example, when the first control device 411 detects the first high-load operation of the fuel cell 441, it determines that the permission conditions for the fuel cell 441 are met and asserts the permission flag of the fuel cell 441. When the permission flag of the fuel cell 441 is asserted, the first control device 411 performs a refresh operation to temporarily transition the fuel cell 441 to a low-load state for a predetermined low-load time Tn. The first control device 411 processes the permission flags of the other fuel cells 442, etc. in the same manner.

On the other hand, when the first control device 411 detects a low load state longer than the predetermined low load time Tn for the fuel cell 441, it determines that an abnormality condition for the fuel cell 441 is established and asserts an abnormality flag for the fuel cell 441. When the abnormality flag for the fuel cell 441 is asserted, the first control device 411 stops power generation of the fuel cell 441 in order to transition the fuel cell 441 from the abnormal low load state. The first control device 411 processes the abnormality flags of the other fuel cells 442, etc. in the same manner.

In this way, according to the fuel cell power generation system of this embodiment, even if the low load state caused by the refresh operation continues due to an abnormality in the system, the first control device 411 determines that this is an abnormal low load state, and can prevent the abnormal low load state from continuing.

FIG. 4 is a table illustrating the types of flags (permission flags) that permit a low load state. The permission flag may be asserted when a command is issued to perform a refresh operation that temporarily transitions the load state of the fuel cell to a low load state to improve the characteristics of the fuel cell (first permission condition). The permission flag may be asserted when a user manually instructs the fuel cell to transition to a low load state (second permission condition). The permission flag may be asserted when a certain range of output power of the fuel cell rises above the certain range (third permission condition). The permission flag may be asserted when a certain range of output power continues for a predetermined time or more (fourth permission condition). The permission flag may be asserted when multiple permission conditions are satisfied.

Figure 5 is a table illustrating the types of flags (abnormality flags) that determine an abnormally low load state. The abnormality flag may be asserted when a main condition is satisfied, or when a main condition and a sub-condition are satisfied.

The abnormality flag may be asserted when the low load state of the fuel cell continues for a predetermined time or more set by a timer (first abnormality condition). Alternatively, the abnormality flag may be asserted when the output voltage of the fuel cell in a low load state rises to a predetermined set value or more (second abnormality condition). The abnormality flag may be asserted when both the first abnormality condition and the second abnormality condition are satisfied.

The abnormality flag may be asserted when at least one of the first abnormality condition and the second abnormality condition is satisfied, and a first sub-condition is satisfied in which the power generation efficiency of the fuel cell falls beyond a predetermined range. The abnormality flag may be asserted when at least one of the first abnormality condition and the second abnormality condition is satisfied, and a second sub-condition is satisfied in which the voltage of the storage device 14 falls beyond a predetermined range. The abnormality flag may be asserted when at least one of the first abnormality condition and the second abnormality condition is satisfied, and a third sub-condition is satisfied in which the temperature of the fuel cell power generation system (e.g., the fuel cell or its surrounding temperature), the pressure of the air supplied to the fuel cell, or the flow rate of the fuel cell coolant falls beyond a predetermined range.

Next, we will explain the process that is performed after the fuel cell load state is determined to be an abnormally low load state.

Figure 6 shows several examples of processing after the load state of the fuel cell is determined to be an abnormally low load state. When an abnormality condition is met and the load state of the fuel cell 441, etc. is determined to be an abnormally low load state, the first control device 411 may execute the following control processing.

For example, the first control device 411 stops power generation of a fuel cell among the multiple fuel cells for which an abnormal condition exists (see <Stop> in FIG. 6). By stopping power generation of the fuel cell, the load state of the fuel cell can be transitioned from an abnormal low load state. This suppresses the deterioration of the fuel cell performance due to the continuation of the low load state.

For example, the first control device 411 adjusts the load on the fuel cell in which the abnormal condition is satisfied so that the power supply Pa from the output line 17 to the outside is maintained constant, thereby increasing the output power of the fuel cell above the low load state (see <Output Adjustment A> in FIG. 6). When the output power of the fuel cell increases above the low load state, the abnormal condition is no longer satisfied and the load state of the fuel cell can be transitioned from the abnormal low load state. This suppresses the deterioration of the performance of the fuel cell due to the continuation of the low load state. The first control device 411 can maintain the supply power Pa constant even if the output power of the fuel cell is increased above the low load state by greatly adjusting the load on the fuel cell in which the abnormal condition is satisfied (for example, the power consumption of the device connected to the output line 17). For example, the first control device 411 increases the output power of the fuel cell in which the abnormal condition is satisfied to a power range higher than 10% and lower than 15% of the rated output of the fuel cell or power generation device.

For example, the first control device 411 increases the output power of a fuel cell in which an abnormal condition is satisfied above the low load state so that the supply power Pa is maintained constant, and decreases the output power of a fuel cell in which an abnormal condition is not satisfied among the multiple fuel cells (see <Output Adjustment B> in FIG. 6). By increasing the output power of the fuel cell above the low load state, the abnormal condition is not satisfied and the load state of the fuel cell can be transitioned from the abnormal low load state. This suppresses the deterioration of the performance of the fuel cell due to the continuation of the low load state. By decreasing the output power of the fuel cell in which an abnormal condition is not satisfied, the first control device 411 can maintain the supply power Pa constant even if the output power of the fuel cell in which an abnormal condition is satisfied is increased above the low load state. For example, the first control device 411 increases the output power of the fuel cell in which an abnormal condition is satisfied to a power range higher than 10% and lower than 15% of the rated output of the fuel cell or power generation device.

Figure 7 is a diagram showing an example of a sequence for determining an abnormal low-load state. In step S111, the first control device 411 constantly monitors the load state of the fuel cell 441, etc., and monitors whether the load state is a low-load state. When the low-load state of the fuel cell 441, etc. is detected in step S111, the first control device 411 determines whether the above abnormal condition is satisfied (whether the state is abnormally low-load state or not) (step S113). If the above abnormal condition is satisfied in step S113, the first control device 411 asserts an abnormality flag of the fuel cell in which the abnormality condition is satisfied among the multiple fuel cells (step S115). The first control device 411 releases the low-load state of the fuel cell in which the abnormality flag is asserted (step S117). For example, the first control device 411 stops the power generation of the fuel cell in which the abnormality flag is asserted, or increases the output power of the fuel cell in which the abnormality flag is asserted, as described above, to transition the fuel cell from the abnormal low-load state. When the above abnormal condition is no longer satisfied as a result of the processing of step S117, the first control device 411 negates the abnormality flag (step S119).

Figure 8 is a diagram showing an example of a sequence for permitting a low-load state. In step S121, the first control device 411 determines whether the abnormality flag controlled in the sequence of Figure 7 is asserted or not. If the abnormality flag is not asserted (if the abnormality flag is negated), the first control device 411 transitions the control state to the state of steps S122, S123, and S124. In steps S122, S123, and S124, the first control device 411 determines whether to permit a low-load state. The first control device 411 permits a low-load state only when the above-mentioned specific permission conditions are met. If the specific permission conditions are met, the first control device 411 asserts the permission flag (step S125). This enables a transition to a low-load state. The first control device 411 maintains the low-load state until a predetermined time continues (step S126), and negates the permission flag when the predetermined time has elapsed (step S127). As a result, the low load state is prohibited, and the first control device 411 transitions the fuel cell from the low load state.

Figure 9 is a flowchart showing an example of the control process executed by the first control device 411 and the second control devices 421, 422, 423, and 424 in the fuel cell power generation system 401.

In step S10, the first control device 411 performs a process of generating command a (commands a1, a2, a3, a4) that indicates the output setting values of each output power P1, P2, P3, P4 of the power generation device 451, etc., according to the required output power of the fuel cell power generation system 401. In step S20, the first control device 411 transmits the command a (commands a1, a2, a3, a4) generated in step S10 to each of the power generation devices 451, etc.

In step S30, the second control device 421 receives a command a1 generated to maintain the supply power Pa at a constant required output power. The second control device 422 receives a command a2 generated to maintain the supply power Pa at a constant required output power. The second control device 423 receives a command a3 generated to maintain the supply power Pa at a constant required output power. The second control device 424 receives a command a4 generated to maintain the supply power Pa at a constant required output power.

In step S31, the second control device 421 controls the power generation of the fuel cell 441 by operating the auxiliary device 431 so that the output power P1 of the power generation device 451 becomes the output set value specified by command a1. The second control device 422 controls the power generation of the fuel cell 442 by operating the auxiliary device 432 so that the output power P2 of the power generation device 452 becomes the output set value specified by command a2. The second control device 423 controls the power generation of the fuel cell 443 by operating the auxiliary device 433 so that the output power P3 of the power generation device 453 becomes the output set value specified by command a3. The second control device 424 controls the power generation of the fuel cell 444 by operating the auxiliary device 434 so that the output power P4 of the power generation device 454 becomes the output set value specified by command a4.

Figure 10 is a flowchart showing an example of the command generation process (the process of step S10 in Figure 9 described above) executed by the first control device 411.

In step S11, the first control device 411 determines whether each of the power generation devices 451, etc. can be operated. The first control device 411 detects the state of each of the power generation devices 451, etc., such as an abnormality or a maintenance time, based on information acquired from each of the second control devices 421, 422, 423, 424, for example. The first control device 411 determines that the power generation devices 451, etc., for which an abnormality or a maintenance time has been detected, cannot be operated, and determines that the power generation devices for which no abnormality or a maintenance time has been detected are operable.

In step S12, the first control device 411 calculates the maximum output power that the fuel cell power generation system 401 can generate based on the number of power generation devices determined to be operable (operable number), and calculates the output setting value of the output power of each power generation device determined to be operable. The output power required for the fuel cell power generation system 401 is required to be within the maximum output power. If the output power required for the fuel cell power generation system 401 exceeds the maximum output power, the first control device 411 notifies an error.

In step S12, for example, the first control device 411 sets the output setting value of each output power P1, P2, P3, P4 of the power generation device 451, etc., to a value obtained by dividing the required output power by the number of operable units. Alternatively, the first control device 411 may set the output setting value of one or more operable power generation devices to the rated power of the power generation devices based on a predetermined setting order, and set the output setting value of one power generation device to (required output power - the sum of the output setting values of the other power generation devices). The method of calculating the output setting value of the output power of each power generation device is not limited to these.

In step S13, the first control device 411 generates a command a (commands a1, a2, a3, a4) that indicates the output set value of the output power of each power generation device calculated in step S12. The second control device of each power generation device controls the power generation of the fuel cell by operating each auxiliary device according to these commands a1, a2, a3, a4.

In this way, in the fuel cell power generation system 401, the role of the first control device 411 is separated from the roles of the second control devices 421, 422, 423, and 424, improving maintainability and expandability.

<Refresh operation>
In the fuel cell power generation system 400, 401, each of the multiple second control devices 421 etc. receives a command a (commands a1, a2, a3, a4) to change the output power of the fuel cell so that the supply power Pa is maintained at a constant required output power. Each of the multiple second control devices 421 etc. may intermittently perform a refresh operation to improve the characteristics of the fuel cell by operating auxiliary equipment to change the output power of the fuel cell in accordance with the command a received for itself. This makes it possible to improve characteristics (e.g., output voltage characteristics) that have deteriorated due to continuous operation of the fuel cell while the supply power Pa is maintained at a substantially constant value.

For example, each of the multiple second control devices 421 etc. operates the auxiliary devices according to command a to change the output power of the fuel cell so that the supply power Pa is maintained at a constant required output power. By operating the auxiliary devices in this manner, each of the multiple second control devices 421 etc. temporarily reduces the output voltage or output power of the fuel cell, or temporarily stops the fuel cell. This makes it possible to improve characteristics (e.g., output voltage characteristics) that have deteriorated due to continuous operation of the fuel cell while maintaining the supply power Pa at an approximately constant value.

Refresh operation is an operation in which dry areas that occur on the cell surface of a fuel cell as a result of continuous operation are moistened by following steps 1 to 4 below. Dry areas can cause a decrease in the battery characteristics.

Step 1: Temporarily increase the output power of the fuel cell above a predetermined constant power value (first high-load operation). By performing the first high-load operation, the amount of moisture within the cell surface of the fuel cell can be increased by generating water.

Step 2: Temporarily set the fuel cell output power to zero (idling operation). By temporarily setting the output power to 0kW (idling state) through idling operation, the generated water can be made uniform across the cell surface of the fuel cell.

Step 3: Temporarily increase the output power of the fuel cell above a predetermined constant power value (second high-load operation). By temporarily transitioning from an idling state to the second high-load operation, the amount of moisture within the cell surface of the fuel cell can be increased.

Step 4: Return the fuel cell output power to a predetermined constant power value.

During refresh operation, the fuel cell power generation system 401 or the like may compensate for fluctuations in the supply power Pa caused by the first high-load operation, the idling operation, and the second high-load operation by using an auxiliary power source such as an attached power storage device 14. When a storage battery is used as the auxiliary power source, the storage battery has a storage capacity capable of absorbing the power Pb input and output during refresh operation.

Figure 11 is a flowchart showing an example of control processing during refresh operation. The processing device during refresh operation can be applied to either fuel cell power generation system 400 or 401. In the following explanation, fuel cell power generation system 401 is used as an example. When starting refresh operation, the first control device 411 performs the processing of steps S60 and S70.

In step S70, the first control device 411 sets the operating conditions of the auxiliary system 301, such as the cooling system, to the conditions during refresh operation. This is because the output power of each fuel cell is varied during refresh operation.

In step S60, the first control device 411 performs a process for setting the refresh operation machine. The process for setting the refresh operation machine includes a process for selecting a power generation device that will perform the refresh operation from among multiple power generation devices connected in parallel.

Figure 12 is a flowchart showing an example of a process for setting a refresh operation machine. The power generation device X represents one or more of the power generation devices connected in parallel. The first control device 411 selects the power generation device X to perform the refresh operation from the multiple power generation devices connected in parallel based on a predetermined selection condition such as a selection order.

In step S61, the first control device 411 sets to ON the refresh operation implementation flag of the power generation device X, among the multiple power generation devices connected in parallel, for which the interval count of the refresh operation has been incremented. In step S62, the first control device 411 starts the interval count of the refresh operation of the power generation device X for which the refresh operation has ended (initializes the interval counter). This causes the refresh operation of the power generation device X to be performed at a predetermined time interval.

In step S80 of FIG. 11, the first control device 411 increments the interval counter for the refresh operation. In step S81, the first control device 411 individually generates commands a (commands a1, a2, a3, a4) to change the output power of the fuel cell to the output set value so that the supply power Pa is maintained at a constant required output power during the refresh operation, and transmits the commands a to each of the power generation devices 451, etc.

In step S90, the second control device 421 etc. receives command a generated so that the supply power Pa is maintained at a constant required output power during refresh operation. The second control device 421 etc. performs refresh operation in accordance with command a.

Figure 13 is a flowchart showing an example of the refresh operation process. The second control device in the power generation device X performs the processes of steps S91 to S98 at a timing according to command a from the first control device 411.

The second control device in the power generation device X increases the output power of the fuel cell from a predetermined constant power value pX4 to set it to output power pX1 (step S91), and after a timer count (step S92), reduces the output power of the fuel cell to set it to output power pX2 (step S93). After a timer count (step S94), the second control device in the power generation device X increases the output power of the fuel cell from the output power pX2 to set it to output power pX3 (step S95). After a timer count (step S96), the second control device in the power generation device X reduces the output power of the fuel cell to return it to the predetermined constant power value pX4 (step S97), and after a timer count (step S98), ends the refresh operation process. When the first control device 411 receives the end of the refresh operation process from the second control device in the power generation device X, it sets the implementation flag of the refresh operation of the power generation device X to off.

Figure 15 shows a first example of a pattern for implementing refresh operation when four power generation devices are connected in parallel. Figure 15 shows a case in which the periods during which refresh operation is performed do not overlap among multiple power generation devices. Power generation device 451 performs refresh operation during refresh operation period Tr1, and then power generation device 452 performs refresh operation during refresh operation period Tr2.

Figure 15 shows the refresh operation in which the output power is changed in steps 1 to 4 above. For example, in each of the refresh operation periods Tr1 and Tr2, in the first high load operation, the output power temporarily increases from 45 kW to 60 kW. In the idling operation, the output power temporarily decreases from 60 kW to 0 kW. In the second high load operation, the output power temporarily increases from 0 kW to 60 kW. After these operations are performed in this order, the output power returns from 60 kW to 45 kW.

Each of the multiple second control devices 421, etc., changes the output power of each fuel cell as shown in FIG. 15 in accordance with command a (commands a1, a2, a3, a4) that changes the output power of the fuel cell so that the supply power Pa is maintained at a constant required output power. This causes the supply power Pa to be maintained at a substantially constant 180 kW as shown in FIG. 14. Therefore, with the supply power Pa maintained at a substantially constant value, it becomes possible to improve the characteristics that have deteriorated due to continuous operation of the fuel cell.

<Constraints when performing refresh operation with multiple units operating in parallel>
Fig. 16 is a table illustrating the relationship between the number of power generation devices connected in parallel and the output power of the power generation device. When performing the refresh operation described above, the number of power generation devices connected in parallel is n, and the rated output of one power generation device is A. n is an integer of 2 or more. Fig. 16 illustrates the case where the rated output is 60 kW.

The maximum supply power Pa that can be obtained during idling operation when the output power of one of the multiple power generation devices is zero is A x (n-1). For example, when A = 60 kW and n = 5, the maximum supply power Pa is 240 kW. In other words, the first control device generates a command a that changes the output power of the fuel cell so that the supply power Pa is maintained at a constant required output power that is equal to or less than A x (n-1). At this time, the average output power B of one power generation device is expressed as A x (n-1)/n.

As the number n of parallel units increases, the average output power B of one power generating unit increases, as shown in FIG. 16. On the other hand, the output difference C between the output power during first high load operation and the average output power B decreases as the number n of parallel units increases. As shown in FIG. 15, the output difference C corresponds to the difference between the output power value during first high load operation of one power generating unit and a predetermined constant power value. When the output difference C decreases, it becomes difficult to ensure a sufficient amount of water generated within the cell surface. In view of these, in constant output operation using refresh operation, it is necessary to satisfy the conflicting demands of increasing the number n of parallel units in terms of increasing the supply power Pa, and reducing the number n of parallel units in terms of ensuring the output difference C.

Figure 17 shows data illustrating the range of the number of parallel units suitable for using refresh operation. A represents the rated output of one power generation device. Increasing the number of parallel units n increases the average output power B and decreases the output difference C. Let D be the first threshold and E be the second threshold smaller than the first threshold. In this case, if the number of parallel units n is a number that satisfies B/A equal to or greater than D and C/A equal to or greater than E, then an increase in the supply power Pa and securing the output difference C can both be achieved. In Figure 17, for example, if D = 0.7 and E = 0.1, the number n is preferably 4 or more and 10 or less.

<Example of a fuel cell power generation system>
Fig. 18 is a diagram showing a specific configuration example of a fuel cell power generation system. The fuel cell power generation system 201 shown in Fig. 18 is a system that supplies power generated by a plurality of FC (fuel cell) platforms connected in parallel to an external device 12 that is a power supply target. Specific examples of uses of the fuel cell power generation system 201 include a stationary power generation system, a power generation system for cargo handling machines such as port cranes, and a power generation system for ships. Other examples include a power generation system for railways and construction machines. Uses of the fuel cell power generation system 201 are not limited to these examples, and the fuel cell power generation system 201 may be applied to other applications.

The fuel cell power generation system 201 includes a fuel cell power generation device 101 and an auxiliary system 301. The fuel cell power generation system 201 is a specific example of the fuel cell power generation system 401 described above.

The auxiliary system 301 is a peripheral system that includes multiple auxiliary devices connected to the fuel cell power generation device 101, which is the main device, and assists the operation of the fuel cell power generation device 101. Figure 18 shows examples of multiple auxiliary devices, including a control power supply 32, a purge system 30, a fuel system 18, an air supply system 19, an output line 17, a power conversion device 11, a DC/DC converter 13, a power storage device 14, an exhaust system 31, and a cooler 15. Some or all of the multiple auxiliary devices may be built into the fuel cell power generation device 101, or may be unitized. The fuel cell power generation device 101 may include some or all of the multiple auxiliary devices inside the fuel cell power generation device 101, or outside the fuel cell power generation device 101.

The fuel cell power generation device 101 generates power to be supplied to an external device 12 using multiple FC platforms. The fuel cell power generation device 101 may be unitized. The fuel cell power generation device 101 includes multiple FC platforms (in this example, three FC platforms 1, 2, and 3) connected in parallel to an output line 17, and a control device 10 that controls the multiple FC platforms. The number of multiple FC platforms connected in parallel is not limited to three, and may be two, four, or more.

FC platforms 1, 2, and 3 each include an FC stack connected to a common output line 17 via an output point 16. The FC stack is an example of a fuel cell. FC platform 1 includes an FC stack 21, FC platform 2 includes an FC stack 22, and FC platform 3 includes an FC stack 23.

The FC platform 1 etc. is an example of the above-mentioned power generation device 451 etc. The FC stack 21 etc. is an example of the above-mentioned fuel cell 441 etc. The control device 10 is an example of the above-mentioned first control device 411 etc.

The FC stacks 21, 22, and 23 are devices that electrochemically convert the chemical energy of fuels such as hydrogen into electrical energy. The FC stacks 21, 22, and 23 generate electricity through an electrochemical reaction between hydrogen or hydrogen-rich gas supplied through a fuel system 18 including a fuel pipe and oxygen contained in air supplied from the outside through an air supply system 19 including an air pipe. The power generation state of the FC stacks 21, 22, and 23 (FC platforms 1, 2, and 3) is controlled by the control device 10. Exhaust gas generated by the electrochemical reaction of the FC stacks 21, 22, and 23 is discharged through an exhaust system 31 including an exhaust pipe. The FC stacks 21, 22, and 23 are cooled by a coolant supplied from a cooler 15 such as a radiator.

The FC stacks 21, 22, and 23 are, for example, polymer electrolyte fuel cells (PEFCs) and have a stack structure in which a large number of unit cells are stacked. The unit cell has a membrane-electrode assembly (MEA) in which both sides of a polymer electrolyte membrane for selectively transporting hydrogen ions are sandwiched between a pair of electrodes formed of a porous material, and a pair of separators that sandwich the MEA from both sides. Each of the pair of electrodes has a catalyst layer mainly composed of carbon powder that supports a platinum-based metal catalyst (electrode catalyst), for example, and a gas diffusion layer that is both breathable and electronically conductive.

The FC stacks 21, 22, and 23 are equipped with voltage sensors for detecting the voltages at their output terminals and current sensors for detecting the output currents from their output terminals. The control device 10 obtains the detection values of the voltages output from the FC stacks 21, 22, and 23 using the voltage sensors, and obtains the detection values of the currents output from the FC stacks 21, 22, and 23 using the current sensors. The control device 10 detects the output powers p1, p2, and p3 of the FC stacks 21, 22, and 23 using the detection values of the voltages and currents.

The power generated by the FC stacks 21, 22, 23 (FC platforms 1, 2, 3) in the fuel cell power generation device 101 is supplied to the external device 12 via the power conversion device 11.

The power conversion device 11 is a device that converts input power Pa into power Pc to be supplied to the external device 12. The power conversion device 11 is, for example, an inverter that converts DC power obtained by power generation in the FC stacks 21, 22, and 23 into AC power and supplies it to the external device 12. Specific examples of inverters include a power conditioner (PCS: Power Conditioning System) and a grid-connected inverter. When the external device 12 is a motor, the power conversion device 11 may be an inverter that drives the motor. The power conversion device 11 may be a converter that converts the voltage of the DC power obtained by power generation in the FC stacks 21, 22, and 23 into DC power of a different voltage and supplies it to the external device 12.

The DC power obtained by the power generation of the FC stacks 21, 22, 23 may be charged to the power storage device 14 connected to the output line 17 via the DC/DC converter 13. The power Pb discharged from the power storage device 14 is supplied to the external device 12 via the power conversion device 11. The power Pb input (regenerated) from the external device 12 via the power conversion device 11 may be charged to the power storage device 14. The charging or discharging of the power storage device 14 is controlled by the DC/DC converter 13 that operates according to a drive control signal from the control device 10. The DC/DC converter 13 may not be required.

The power storage device 14 may include a chargeable and dischargeable secondary battery. The power storage device 14 may include a plurality of storage batteries 14 ₁ , ..., 14 _n (n is an integer of 2 or more) connected in series. Specific examples of the power storage device 14 (the plurality of storage batteries 14 ₁ , ..., 14 _n ) include a lithium ion battery, a lithium ion capacitor, and an electric double layer capacitor.

The fuel system 18 may include a reforming device that reforms the hydrocarbon fuel supplied from the outside into hydrogen-rich gas. The reforming device outputs hydrogen-rich gas produced by a reforming reaction of the hydrocarbon fuel to the hydrogen pipe. The reforming device includes, for example, a desulfurizer that removes sulfur contained in the hydrocarbon fuel, a reformer that causes a reforming reaction of the desulfurized hydrocarbon fuel, and a CO remover that removes carbon monoxide (CO) generated during reforming.

Hydrocarbon fuels are not limited to city gas, but may also include methane gas, propane gas, digester gas derived from sewage sludge, etc., and biogas generated from food waste, etc.

The control device 10 is a controller that controls the operation of the FC platforms 1, 2, and 3. The control device 10 operates, for example, using power (e.g., 12-volt DC power) supplied from a control power supply 32. The control power supply 32 is, for example, a control battery.

Figure 18 illustrates an example of a configuration in which the fuel cell power generation device 101 includes a control power supply 32 common to the FC platforms 1, 2, and 3. By sharing the power supply for the FC platforms 1, 2, and 3 as the control power supply 32, the fuel cell power generation system 201 and the fuel cell power generation device 101 can be made smaller than in a configuration in which multiple control power supplies are provided.

The fuel cell power generation device 101 may be provided with individual control power supplies 32 for the FC platforms 1, 2, and 3. By providing multiple power supplies for the multiple FC platforms individually, even if some of the multiple control power supplies are unusable due to failure or maintenance, etc., the remaining power supplies can be used to continue operating some or all of the multiple FC platforms.

The functions of the control device 10 (the processing performed by the control device 10) are realized, for example, by a processor such as a CPU (Central Processing Unit) operating according to a program stored in memory. The functions of the control device 10 may also be realized by an FPGA (Field Programmable Gate Array) or an ASIC (Application Specific Integrated Circuit).

Figure 19 is a diagram showing a detailed configuration example of a fuel cell power generation device 101. The fuel cell power generation device 101 includes, for example, a control device 10 and multiple FC platforms 1, 2, and 3. The FC platform 1 includes, for example, a fuel pipe 118, an air pipe 119, an air filter 33, an exhaust pipe 131, a first cooling system 36, a second cooling system 90, and an FC unit 51. The FC unit 51 includes an FC stack 21, a boost converter 42, a hydrogen pump 43, an air compressor 45, a water pump 44, an air inlet shutoff valve 77, and an exhaust air outlet shutoff valve 78, etc. The boost converter 42, the hydrogen pump 43, the air compressor 45, the water pump 44, the air inlet shutoff valve 77, and the exhaust air outlet shutoff valve 78, etc. are controlled by the control device 10. The FC platforms 2 and 3 have the same configuration and function as the FC platform 1, and are controlled by the control device 10 in the same manner as the FC platform 1. Therefore, the explanation of FC platforms 2 and 3 will be omitted, as the explanation of FC platform 1 will be used.

The FC stack 21 has a fuel electrode 71 and an air electrode 72. The FC stack 21 generates electricity by an electrochemical reaction between hydrogen or hydrogen-rich gas supplied to the fuel electrode 71 and oxygen contained in the air supplied to the air electrode 72. The FC stack 21 is connected to the output line 17 via a boost converter 42. The boost converter 42 is a DC/DC converter that boosts the voltage output from the FC stack 21 and outputs the boosted DC power to the output line 17 via the output point 16. The output power of the multiple FC stacks 21, 22, and 23 in the multiple FC platforms 1, 2, and 3 is output to a common output line 17 via the corresponding boost converters 42.

Hydrogen is supplied to the fuel pipe 118 from a fuel system 18 commonly connected to the multiple FC platforms 1, 2, and 3. The fuel pipe 118 supplies hydrogen to the fuel electrode 71 via the inlet 75.

Air is supplied to the air pipe 119 from an air supply system 19 commonly connected to the multiple FC platforms 1, 2, and 3. The air pipe 119 supplies air to the air pole 72 of the FC stack 21 via an inlet 73. The air pipe 119 is not essential, and the air filter 33 may directly draw in air from the open parts of the FC platforms 1, 2, and 3.

The air filter 33 removes dust and impurities that may adversely affect the fuel cell from the air supplied via the air supply system 19 and air pipe 119, and supplies the air to the air compressor 45 via the air pipe 120. The air filter is also called an air cleaner.

The air compressor 45 compresses the air supplied through the air filter 33 and supplies it to the air electrode 72 of the FC stack 21. The oxygen-containing air compressed by the air compressor 45 is supplied to the air electrode 72 of the FC stack 21 via the inlet 73. The air inlet shutoff valve 77 shuts off the flow of air supplied from the air compressor 45 to the inlet 73 of the air electrode 72.

The exhaust pipe 131 discharges exhaust gas generated in the FC stack 21 to an exhaust system 31 commonly connected to multiple FC platforms 1, 2, and 3. The exhaust air outlet shutoff valve 78 shuts off the flow of off-gas discharged from the outlet 74 of the air electrode 72 of the FC stack 21 to the exhaust pipe 131.

The first cooling system 36 cools the FC stack 21 with a first cooling liquid such as cooling water. The first cooling system 36 has a first intermediate heat exchanger 34 that exchanges heat with a cold heat source 39 to cool the first cooling liquid. The water pump 44 circulates the first cooling liquid between the first intermediate heat exchanger 34 and the FC stack 21. The FC stack 21 is cooled by the first cooling liquid circulated by the water pump 44.

The first intermediate heat exchanger 34 is a heat exchanger capable of exchanging heat between the first cooling liquid that cools the FC stack 21 and a different type of cold heat source 39. The different types of cold heat sources 39 mean that the type of cold heat source 39 used does not matter. The first intermediate heat exchanger 34 can cool the first cooling liquid with any cold heat source 39, regardless of the type of cold heat source 39 used, thereby realizing a fuel cell power generation device 101 that can be used for various purposes such as those described above.

The first intermediate heat exchanger 34 has a heat dissipation section 40 through which the first cooling liquid circulating in the first cooling system 36 passes, and a heat receiving section 41 through which a heat medium that transfers heat between the cold heat source 39 passes. The heat medium supplied from the cold heat source 39 may be liquid or gas. The first cooling liquid is cooled by dissipating heat from the heat dissipation section 40 to the heat receiving section 41 in the first intermediate heat exchanger 34. A specific example of the first intermediate heat exchanger 34 is a plate heat exchanger, but the first intermediate heat exchanger 34 is not limited to this.

The multiple first intermediate heat exchangers 34 in the multiple FC platforms 1, 2, 3 may each exchange heat with a cold heat source 39 that is commonly connected to the multiple FC platforms 1, 2, 3. This allows the cold heat source 39 to be common between the multiple FC platforms 1, 2, 3, making it possible to reduce the size of the fuel cell power generation device 101. Note that the cold heat source 39 may be different between the multiple FC platforms 1, 2, 3.

The second cooling system 90 cools the air compressor 45 with a second cooling liquid such as cooling water. The second cooling system 90 has a second intermediate heat exchanger 92 that exchanges heat with a cold heat source 94 to cool the second cooling liquid. The pump 91 circulates the second cooling liquid between the second intermediate heat exchanger 92 and the air compressor 45. The air compressor 45 is cooled by the second cooling liquid circulated by the pump 91.

The second intermediate heat exchanger 92 is a heat exchanger capable of exchanging heat between the second cooling liquid that cools the air compressor 45 and a different type of cold heat source 94. The different types of cold heat sources 94 mean that the type of cold heat source 94 used does not matter. The second intermediate heat exchanger 92 can cool the second cooling liquid with any cold heat source 94, regardless of the type of cold heat source 94 used, thereby realizing a fuel cell power generation device 101 that can be used for various purposes such as those described above.

The second intermediate heat exchanger 92 has a heat dissipation section 95 through which the second cooling liquid circulating in the second cooling system 90 passes, and a heat receiving section 96 through which a heat medium passes to transfer heat between the cold heat source 94. The heat medium supplied from the cold heat source 94 may be liquid or gas. The second cooling liquid is cooled by dissipating heat from the heat dissipation section 95 to the heat receiving section 96 in the second intermediate heat exchanger 92. A specific example of the second intermediate heat exchanger 92 is a plate heat exchanger, but the second intermediate heat exchanger 92 is not limited to this.

The multiple second intermediate heat exchangers 92 in the multiple FC platforms 1, 2, 3 may each exchange heat with a cold heat source 94 that is commonly connected to the multiple FC platforms 1, 2, 3. This allows the cold heat source 94 to be common between the multiple FC platforms 1, 2, 3, making it possible to reduce the size of the fuel cell power generation device 101. Note that the cold heat source 94 may be different between the multiple FC platforms 1, 2, 3.

The cooler 15 (Figure 18) is an example of the cold heat source 39 or the cold heat source 94. The cold heat source 39 or the cold heat source 94 is, for example, an air-cooled cooler, an open cooling tower, a closed cooling tower, cooling water in a factory, tap water, river water, seawater, the heat of vaporization of liquefied hydrogen, or the cold heat generated when compressed hydrogen expands.

The material of the heat receiving portion 41 of the first intermediate heat exchanger 34 is, for example, a low-elution metal with a relatively low elution rate of metal ions (for example, highly corrosion-resistant austenitic stainless steel (SUS316L)). If the heat medium in contact with the heat receiving portion 41 is seawater, for example, there is a risk that metal ions will be eluted from the heat receiving portion 41, depending on the material of the heat receiving portion 41. If the material of the heat receiving portion 41 is a low-elution metal as described above, the restrictions on the heat medium supplied from the cold heat source 39 are alleviated, and the options for the cold heat source 39 increase. As a result, a fuel cell power generation device 101 that can be used for various applications such as those described above is realized. The same applies to the material of the heat receiving portion 96 of the second intermediate heat exchanger 92.

In addition, by employing the first intermediate heat exchanger 34, the first coolant can dissipate heat without having to extend the path through which the first coolant circulates to the cold heat source 39 outside the FC platform. In other words, the path through which the first coolant circulates can be shortened, and the amount of expensive first coolant used to cool the fuel cell can be reduced. As a result, costs can be reduced. Similarly, by employing the second intermediate heat exchanger 92, the amount of second coolant used can be reduced, and costs can be reduced.

The cold heat source 94 from which the second intermediate heat exchanger 92 dissipates heat of the second cooling liquid may be the same as or different from the cold heat source 39 from which the first intermediate heat exchanger 34 dissipates heat of the first cooling liquid. If the cold heat source 94 and the cold heat source 39 are the same, the cold heat source is shared between the first intermediate heat exchanger 34 and the second intermediate heat exchanger 92, so that the fuel cell power generation device 101 can be made smaller.

The first cooling system 36 may include an ion exchanger 35 that removes ions from the first cooling liquid. By removing ions from the first cooling liquid, an increase in the electrical conductivity of the first cooling liquid inputted and outputted to the FC stack 21 is suppressed, thereby suppressing electrical interference between the FC stack 21 and the first cooling liquid.

In addition, by adopting the first intermediate heat exchanger 34, the dissolution of ions from the first cooling liquid on the first cooling system 36 side to the heat medium on the cold heat source 39 side is suppressed, thereby reducing the frequency of maintenance of the ion exchanger 35.

The first cooling system 36 may include a sensor 37 that measures the electrical conductivity of the first cooling liquid. By including the sensor 37, the electrical conductivity of the first cooling liquid can be managed. For example, if the sensor 37 detects that the electrical conductivity has started to increase, the user can know when to perform maintenance on the ion exchanger 35. In addition, by managing the electrical conductivity, the insulation between the DC PN (between the positive and negative) of the fuel cell can be maintained. If the electrical conductivity is measured to be equal to or greater than a first threshold value (e.g., 1 μS/cm), the sensor 37 or the control device 10 may issue an alarm so that the user can recognize it. If the electrical conductivity is measured to be equal to or greater than a second threshold value (e.g., 5 μS/cm) that is greater than the first threshold value, the control device 10 may stop the FC platform in which the electrical conductivity equal to or greater than the second threshold value is measured.

The first cooling system 36 may include a first tank 38 that absorbs expansion or contraction of the first cooling liquid caused by temperature changes. This suppresses expansion or contraction of the first cooling liquid caused by temperature changes.

Similarly, the second cooling system 90 may include a second tank 93 that absorbs the expansion or contraction of the second cooling liquid caused by temperature changes. This suppresses the expansion or contraction of the second cooling liquid caused by temperature changes.

The FC platform 1 may include a first gas-liquid separator 79 and a hydrogen pump 43. The first gas-liquid separator 79 separates hydrogen gas and wastewater from the first multiphase flow discharged from the outlet 76 of the fuel electrode 71. The hydrogen pump 43 circulates the hydrogen gas separated by the first gas-liquid separator 79 to the inlet 75 of the fuel electrode 71. This allows surplus hydrogen gas generated by power generation in the FC stack 21 to be reused for power generation in the FC stack 21.

The FC platform 1 may include a mixer 80. The exhaust pipe 131 discharges a second multiphase flow obtained by combining the wastewater separated by the first gas-liquid separator 79, hydrogen mixed in the wastewater, and exhaust air discharged from the outlet 74 of the air electrode 72 in the mixer 80. This allows the wastewater, hydrogen, and exhaust air to be discharged together.

The FC platform 1 may be provided with a second gas-liquid separator 81 that separates water and gas from the second multiphase flow. This allows the wastewater and exhaust gas to be separated and discharged. The wastewater or exhaust gas may be collected by a collector 82. This prevents the surrounding area from being polluted by the wastewater or exhaust gas.

The fuel cell power generation device 101 may include a purge system 30 that individually supplies an inert gas such as nitrogen to the multiple fuel pipes 118 in the multiple FC platforms 1, 2, and 3. The purge system 30 may switch the flow path with a valve so that the multiple fuel pipes 118 can be individually purged with the inert gas. This allows the deterioration of characteristics due to purging with the inert gas to be managed on a per-FC stack basis.

A portion of the output power p1 of the FC stack 21 is used as operating power for auxiliary equipment such as the air compressor 45 in the FC unit 51, and the surplus power is output as the output power P1 of the FC unit 51. The same applies to the output power p2 of the FC stack 22 and the output power p3 of the FC stack 23.

The control device 10 performs control to maintain the power supplied from the output line 17 to the outside at a substantially constant predetermined value. For example, the control device 10 controls the power generation of the FC stacks 21, 22, 23 (FC platforms 1, 2, 3) and the conversion operation of the DC/DC converter 13 so that the supply power Pa (= Po - Pb) output from the output line 17 to the power conversion device 11 is maintained at a constant target value. Po is the power at the output point 16. Po is equal to the sum of the output powers P1, P2, P3 of the FC platforms 1, 2, 3 (Po = P1 + P2 + P3). Pb is the power exchanged between the storage device 14 and the output line 17.

The control device 10 may control the power generation of the FC stacks 21, 22, and 23 and the conversion operation of the power conversion device 11 so that the power Pc output from the power conversion device 11 to the external device 12 follows a target value. Pa or Pc is an example of power supplied from the output line 17 to the outside.

The control device 10 may perform control (battery output fluctuation control) to change (more specifically, increase or decrease) the output power p1, p2, and p3 of the FC stacks 21, 22, and 23 while the supply power Pa from the output line 17 to the outside is maintained at a substantially constant value. The supply power Pa can be detected by a voltage sensor and a current sensor.

The control device 10, for example, increases or decreases the operating current (load current) of the boost converter 42 of the FC platform 1 to increase or decrease the load on the FC stack 21 and increase or decrease the output power p1. Similarly, the control device 10 increases or decreases the operating current (load current) of the boost converter 42 of the FC platform 2 to increase or decrease the load on the FC stack 22 and increase or decrease the output power p2. The control device 10 increases or decreases the operating current (load current) of the boost converter 42 of the FC platform 3 to increase or decrease the load on the FC stack 23 and increase or decrease the output power p3.

By the control device 10 performing the above-mentioned battery output fluctuation control, the output powers p1, p2, and p3 of the multiple FC stacks 21, 22, and 23 are increased or decreased while the power supply Pa from the output line 17 to the outside is maintained at a substantially constant value. As a result, while a constant power supply from the output line 17 to the outside is ensured, the humidity distribution imbalance within the cell surface of the multiple FC stacks 21, 22, and 23 is reduced compared to the case where the output powers p1, p2, and p3 are always controlled to be constant. By reducing the humidity distribution imbalance within the cell surface, the increase in current density due to the decrease in effective reaction area is suppressed, and deterioration of the electrolyte membrane due to the increase in current density is suppressed. Therefore, by the control device 10 performing power fluctuation control to increase or decrease each output power p1, p2, and p3 while the supply power Pa is maintained at a substantially constant value, a substantially constant power supply is ensured and deterioration of the multiple FC stacks 21, 22, and 23 is suppressed. Suppressing deterioration of the multiple FC stacks 21, 22, and 23 contributes to improving the durability of the fuel cell power generation device 101 and the fuel cell power generation system 201.

The fuel cell power generation system 201 or the fuel cell power generation device 101 may include a plurality of switches (switches 61, 62, and 63 in this example) provided for each of the plurality of FC platforms. The switch 61 is a circuit breaker that switches between disconnection and connection of the power path between the FC stack 21 and the boost converter 42 and the output point 16 connected to the output line 17. The switch 62 is a circuit breaker that switches between disconnection and connection of the power path between the FC stack 22 and the boost converter (not shown) and the output point 16 connected to the output line 17. The switch 63 is a circuit breaker that switches between disconnection and connection of the power path between the FC stack 23 and the boost converter (not shown) and the output point 16 connected to the output line 17.

The control device 10 may separate some of the FC stacks 21, 22, and 23 from the other FC stacks by the switches 61, 62, or 63. With the FC stacks separated, the control device 10 may control the output power of the other FC stacks so that the power supply Pa is maintained at a substantially constant value. This makes it easy to replace the FC stacks while the power supply Pa is maintained at a substantially constant value. For example, with the FC stack 21 separated from the FC stacks 22 and 23 by the switch 61, the control device 10 may control the output power of the other FC stacks 22 and 23 so that the power supply Pa is maintained at a substantially constant value. The switches 61, 62, and 63 are automatically switched on and off by the control device 10, but may also be switched manually.

The fuel cell power generation system 101 may include shutoff valves for shutting off the piping and switches for shutting off the wiring so that some of the multiple FC platforms can be shut down and removed while the remaining FC platforms are in operation. The piping transmits liquids (coolant, drainage, etc.) or gases (air, hydrogen, exhaust gas, etc.), and the wiring transmits power and signals. Examples of shutoff valves for shutting off the piping include the air inlet shutoff valve 77 and the exhaust air outlet shutoff valve 78. Examples of switches for shutting off the wiring include switches 61, 62, and 63.

The fuel cell power generation system 101 may have a function for individually detecting ground faults in multiple FC platforms. For example, the control device 10 may use a switch 61, 62, or 63 to disconnect an FC platform among multiple FC platforms 1, 2, and 3 in which a drop in resistance to ground or a ground fault has been detected.

The number of the multiple storage batteries 14 ₁ , ..., 14 _n connected in series may be adjusted so that the output voltage of the power storage device 14 is approximately equal to the output voltage at the output point 16. This makes it possible to eliminate the DC/DC converter 13 and reduce the size of the fuel cell power generation device 101.

Each of the FC platforms 1, 2, and 3 includes a second control device 20. The second control device 20 corresponds to the above-mentioned second control device 421, etc. When the refresh operation is not being performed, the second control device 20 adjusts the flow rate of the first coolant by controlling the first cooling system 36 according to the detected temperature value of the FC stack 21 or the first coolant (coolant control). For example, the second control device 20 adjusts the flow rate of the first coolant by controlling at least one of the adjustment valve 46 and the pump 47 included in the first cooling system 36. The adjustment valve 46 adjusts the flow rate of the heat medium that transfers heat between the cold heat source 39 and the first intermediate heat exchanger 34. The pump 47 circulates the heat medium between the cold heat source 39 and the first intermediate heat exchanger 34.

However, as described above, during refresh operation, the output power of each FC platform (each power generation device) fluctuates rapidly so that the supply power Pa remains constant. This causes the temperature of the fuel cell to rise faster, but the above-mentioned coolant control is unable to keep up with this quickly, resulting in larger fluctuations in the fuel cell temperature and the risk of shortening the cell life.

To avoid this, the first cooling system 36 (e.g., the control valve 46, the pump 47, etc.) during the refresh operation may be controlled in any of the following ways (a), (b), or (c).

(a) When the second control device 20 is performing a refresh operation, it maintains the control state of the first cooling system 36 (e.g., at least one of the opening degree of the control valve 46 and the rotation speed of the pump 47) before the start of the refresh operation.

(b) When the detected temperature value of the FC stack, the first cooling liquid, or the outside air is higher than a reference value, the second control device 20 controls the first cooling system 36 (e.g., at least one of the opening of the adjustment valve 46 and the rotation speed of the pump 47) to either lower the temperature of the first cooling liquid or increase the flow rate, or both, before starting the refresh operation. The detected temperature value of the FC stack 21, the first cooling liquid, or the outside air is obtained by the temperature sensor 48.

When the outside air temperature is low during refresh operation (cooling capacity is not insufficient, there is a margin of cooling capacity), control method (a) is preferred, and when the outside air temperature is high (cooling capacity is assumed to be insufficient), control method (b) is preferred. For example, when the temperature detection value of the FC stack, the first cooling liquid, or the outside air is lower than a reference value, the second control device 20 starts the refresh operation while maintaining the control state of the first cooling system 36 before the start of the refresh operation. On the other hand, when the temperature detection value is higher than the reference value, the second control device 20 controls the first cooling system 36 to lower the temperature of the first cooling liquid before starting the refresh operation.

(c) When the refresh operation is being performed, the second control device 20 changes the output power of the FC stack according to a predetermined change pattern, and adjusts the flow rate of the first cooling liquid by controlling the first cooling system 36 (e.g., at least one of the opening of the adjustment valve 46 and the rotation speed of the pump 47) in accordance with the change pattern. Control method (c) can be selected regardless of the outside air temperature. Control method (c) is a method that follows temperature rise, but since it is a method that performs feedforward control based on output and time information during the programmed refresh operation, it is possible to suppress fluctuations in the fuel cell temperature.

In this way, according to this embodiment, the problem of decarbonizing power sources through hydrogen power generation can be solved in fields such as stationary generators, power sources for port loading and unloading machines (such as cranes), power sources for ships, power sources for railways, heavy construction machinery, and heavy civil engineering machinery. Hydrogen power generation can be done using hydrogen combustion or fuel cells, but the fuel cell type is generally more efficient. When applying fuel cells to multiple applications, it takes time and effort to develop each system. According to this embodiment, the problem of developing an inexpensive and highly efficient platform that can be used in common for various applications can be solved. More specifically, in order to apply it to various applications (stationary, crane, ship, railway, construction machinery, etc.), the common parts can be constructed as an FC platform, thereby reducing the system development resources (design, engineering, etc.) for each application. By using a platform common to each application, the mass production effect of the FC platform can be obtained, and the price can be reduced.

Furthermore, according to this embodiment, for the two cooling systems (first cooling system 36 and second cooling system 90), individual engineering of the cooling systems is not required depending on the system to which they are applied, the installation location, etc. More specifically, by installing one or both intermediate heat exchangers of the two cooling systems within the FC platform, individual engineering of the cooling systems is not required.

In addition, according to this embodiment, the parallelization of FC platforms can improve scalability and support high output. By constructing an FC platform that incorporates auxiliary equipment, multiple FC platforms can be easily parallelized, making it easier to improve scalability and support high output.

Furthermore, according to this embodiment, multiple FC platforms can be separated independently, facilitating handling such as transportation, which, for example, facilitates maintenance. For example, in the event of a system failure, the system downtime can be shortened by replacing each FC platform, improving the system's operating rate. In the event of a system failure, rather than repairing the system on-site, the FC platform can be returned to a factory and repaired there, reducing the cost of on-site repair. During the factory return period, a replacement FC platform can be replaced, improving the system's operating rate.

Although the embodiments have been described above, they are presented as examples, and the present invention is not limited to the above embodiments. The above embodiments can be implemented in various other forms, and various combinations, omissions, substitutions, modifications, etc. can be made without departing from the gist of the invention. These embodiments and their variations 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.

For example, the point where the purge system 30 that supplies nitrogen merges with the fuel system 18 that supplies hydrogen is after the fuel system 18 branches off toward the FC stacks 21, 22, and 23, but it may be before the branching.

REFERENCE SIGNS LIST 1, 2, 3 FC platform 10 Control device 11 Power conversion device 12 External device 13 DC/DC converter 14 Power storage device 14 ₁ , 14 _n storage battery 15 Cooler 16 Output point 17 Output line 18 Fuel system 19 Air supply system 20 Second control device 21, 22, 23 FC stack 30 Purge system 31 Exhaust system 32 Control power source 33 Air filter 34 First intermediate heat exchanger 35 Ion exchanger 36 First cooling system 42 Boost converter 43 Hydrogen pump 44 Water pump 45 Air compressor 46 Control valve 47 Pump 48 Temperature sensor 51, 52, 53 FC unit 61, 62, 63 Switch 101, 102 Fuel cell power generation device 201, 202 Fuel cell power generation system 301, 302 Auxiliary system 400, 401 Fuel cell power generation system 411, 412 First control device 421-427 Second control device 431-437 Auxiliary 441-447 Fuel cell 451-457 Power generation device 461 Third control device 471, 472 System

Claims (13)

A fuel cell;
A fuel cell power generation system comprising: a control device that allows the fuel cell to enter a low-load state when a first condition is met, the control device including a command to perform a refresh operation that temporarily transitions the load state of the fuel cell to a low-load state to improve the characteristics of the fuel cell, and that transitions the load state of the fuel cell from an abnormally low-load state when a second condition different from the first condition is met during the refresh operation. The fuel cell power generation system according to claim 1, wherein the control device increases the output power of the fuel cell above a low load state when the second condition is met. The fuel cell power generation system according to claim 2, wherein the control device adjusts the load of the fuel cell to increase the output power of the fuel cell above a low load state when the second condition is met. The fuel cell power generation system according to claim 3, wherein when the second condition is satisfied, the control device adjusts the load of the fuel cell so that the power supplied to the outside from the output line connected to the fuel cell is maintained constant, thereby increasing the output power of the fuel cell above a low load state. The fuel cell power generation system according to claim 2, wherein the control device increases the output power of a fuel cell among the plurality of fuel cells for which the second condition is satisfied above a low load state, and decreases the output power of a fuel cell among the plurality of fuel cells for which the second condition is not satisfied. The fuel cell power generation system according to claim 5, wherein the control device increases the output power of a fuel cell among the plurality of fuel cells for which the second condition is satisfied above a low load state, and decreases the output power of a fuel cell among the plurality of fuel cells for which the second condition is not satisfied, so that the power supplied to the outside from an output line commonly connected to the plurality of fuel cells is maintained constant. The fuel cell power generation system according to claim 1, wherein the control device stops power generation of the fuel cell when the second condition is met. The fuel cell power generation system according to claim 1, wherein the control device monitors the load state of the fuel cell to determine whether the second condition is met. The fuel cell power generation system of claim 1, wherein the second condition includes a condition for determining that the load state of the fuel cell is an abnormally low load state. The fuel cell power generation system according to claim 1, wherein the second condition includes that the low load state of the fuel cell continues for a predetermined period of time or more. The fuel cell power generation system according to claim 10, wherein the second condition includes a decrease in the power generation efficiency of the fuel cell, a decrease in the voltage of a storage battery connected to an output line connected to the fuel cell, or a decrease in the temperature of the fuel cell power generation system, the pressure of the air supplied to the fuel cell, or the flow rate of the cooling liquid of the fuel cell. The fuel cell power generation system of claim 1, wherein the second condition includes an increase in the output voltage of the fuel cell in a low load state. The fuel cell power generation system according to claim 12, wherein the second condition includes a decrease in the power generation efficiency of the fuel cell, a decrease in the voltage of a storage battery connected to an output line connected to the fuel cell, or a decrease in the temperature of the fuel cell power generation system, the pressure of the air supplied to the fuel cell, or the flow rate of the cooling liquid of the fuel cell.

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