Fuel cell system and control method

Abstract

To improve responsiveness of a power generation output of a fuel cell system.SOLUTION: A fuel cell system 1 includes a plurality of fuel cells 10 and a control device 20 configured to control an operating state of each fuel cell 10. The control device 20 includes a command obtaining unit 22 configured to obtain an output command, a normal operation number determination unit 23 configured to determine the number of fuel cells 10 to be operated in a normal operation mode, and an operating state determination unit 24 configured to determine the operating state of each fuel cell 10. The operating state determination unit 24 changes an operation mode of at least one of the fuel cells operating in the normal operation mode to a standby operation mode or changes the operation mode of at least one of the fuel cells operating in the standby operation mode to the normal operation mode, in accordance with the output command.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] An embodiment of the present invention relates to a fuel cell system and a control method thereof. [Background technology]

[0002] Fuel cell systems are known as systems that directly convert the chemical energy of fuel gas into electricity. These fuel cell systems are equipped with fuel cells that generate electricity by electrochemically reacting hydrogen, which is a fuel, with oxygen, which is an oxidant. Such fuel cell systems are capable of extracting electrical energy with high power generation efficiency. Patent Document 1 discloses a fuel cell system equipped with multiple fuel cells. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] JP 2001-102074 A Summary of the Invention [Problem to be solved by the invention]

[0004] Here, there is a demand for improving the responsiveness of the power generation output of the fuel cell system to the required power generation output.

[0005] The present invention has been made in consideration of the above points, and has an object to improve the responsiveness of the power generation output of a fuel cell system. [Means for solving the problem]

[0006] The fuel cell system according to the present invention comprises: A plurality of fuel cells; A control device for controlling the operating state of each fuel cell; Equipped with each fuel cell is operable in a plurality of operation modes including a normal operation mode in which the fuel cell is operated at a power generation output at which the power generation efficiency is equal to or greater than a first power generation efficiency, and a standby operation mode in which the fuel cell is operated at a power generation output at which the power generation efficiency is equal to or less than a second power generation efficiency that is lower than the first power generation efficiency; The control device includes: a command acquisition unit that acquires an output command indicating a total power output to be generated by the fuel cell system; a normal operation number determination unit that determines the number of fuel cells that should be operated in a normal operation mode based on the total power generation output indicated by the output command; an operating state determination unit that determines an operating state of each fuel cell based on the number determined by the normally operating number determination unit; having When the total power generation output indicated by the output command is lower than the total power generation output being generated by the fuel cell system, or when the number of fuel cells determined by the normal operation number determination unit is smaller than the number of fuel cells being operated in a normal operation mode, the operation state determination unit changes the operation mode of at least one of the fuel cells being operated in the normal operation mode to a standby operation mode, If the total power generation output indicated by the output command is higher than the total power generation output being generated by the fuel cell system, or if the number determined by the normally operating number determination unit is greater than the number of fuel cells operating in normal operation mode, the operating state determination unit changes the operating mode of at least one of the fuel cells operating in standby operation mode to normal operation mode.

[0007] The control method according to the present invention comprises the steps of: A method for controlling a fuel cell system including a plurality of fuel cells, each of which can be operated in a plurality of operation modes including a normal operation mode in which the fuel cells are operated at a high-efficiency power generation output having a power generation efficiency equal to or higher than a first power generation efficiency, and a standby operation mode in which the fuel cells are operated at a low-efficiency power generation output having a power generation efficiency equal to or lower than a second power generation efficiency that is lower than the first power generation efficiency, an output command acquisition step of acquiring an output command indicating a total power output to be generated by the fuel cell system; a normal operation number determination step of determining the number of fuel cells to be operated in a normal operation mode based on the total power generation output indicated by the output command; an operating state determination step of determining an operating state of each fuel cell based on the number determined in the normally operating number determination step; Equipped with In the operating state determination step, if the total power generation output indicated by the output command is lower than the total power generation output being generated by the fuel cell system, or if the number of fuel cells determined in the step of determining the number of fuel cells in normal operation is smaller than the number of fuel cells being operated in normal operation mode, changing the operation mode of at least one of the fuel cells operating in normal operation mode to a standby operation mode; If the total power generation output indicated by the output command is higher than the total power generation output being generated by the fuel cell system, or if the number determined in the normally operating number determination process is greater than the number of fuel cells operating in normal operation mode, the operation mode of at least one of the fuel cells operating in standby operation mode is changed to normal operation mode. Effect of the Invention

[0008] According to the present invention, the responsiveness of the power generation output of a fuel cell system can be improved. [Brief description of the drawings]

[0009] [Figure 1] FIG. 1 is a block diagram showing the configuration of a fuel cell system according to a first embodiment of the present invention. [Diagram 2] FIG. 2 is a diagram showing the configuration of a fuel cell included in the fuel cell system shown in FIG. [Diagram 3] FIG. 3 is a diagram showing the configuration of a control device for the fuel cell system shown in FIG. [Figure 4] FIG. 4 is a flowchart showing a control method for the fuel cell system according to the first embodiment. [Diagram 5] FIG. 5 is a flowchart showing a control method for the fuel cell system according to the first embodiment. [Figure 6] FIG. 6 is a diagram showing the configuration of a control device for a fuel cell system according to the second embodiment. [Figure 7] FIG. 7 is a flowchart showing a control method for the fuel cell system according to the second embodiment. [Figure 8] FIG. 8 is a flowchart showing a control method for the fuel cell system according to the second embodiment. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0010] <First embodiment> A first embodiment of the present invention will be described below with reference to the drawings. Fig. 1 is a block diagram showing the configuration of a fuel cell system 1 according to the first embodiment of the present invention. Fig. 2 is a diagram for explaining the schematic configuration of a fuel cell 10 included in the fuel cell system 1 shown in Fig. 1.

[0011] The fuel cell system 1 shown in FIG. 1 includes a plurality of fuel cells 10, a control device 20, and an operating device 30.

[0012] The fuel cell 10 generates electricity using hydrogen and oxygen. Each fuel cell 10 is, for example, a polymer electrolyte fuel cell (PEFC). In the example shown in Fig. 2, the fuel cell 10 includes a fuel cell stack 11, a fuel supply pipe 14, a fuel discharge pipe 15, an air supply pipe 16, an air discharge pipe 17, and a power supply device 18.

[0013] The fuel cell stack 11 includes an anode 12 and a cathode 13 sandwiching an electrolyte membrane. A fuel supply pipe 14 is connected to an intake port of the anode 12. The fuel supply pipe 14 supplies hydrogen gas to the anode 12. A fuel discharge pipe 15 is connected to an exhaust port of the anode 12. The fuel discharge pipe 15 discharges gas discharged from the anode 12 to the outside or inside of the fuel cell 10. An air supply pipe 16 is connected to an intake port of the cathode 13. The air supply pipe 16 supplies oxygen gas in the air to the cathode 13. The air discharge pipe 17 is connected to an exhaust port of the cathode 13. The air discharge pipe 17 discharges gas discharged from the cathode 13 to the outside of the fuel cell 10.

[0014] The fuel cell stack 11 generates electricity using hydrogen gas supplied to the anode 12 via a fuel supply pipe 14 and oxygen gas in the air supplied to the cathode 13 via an air supply pipe 16 .

[0015] A power supply 18 is connected to the electrodes of the fuel cell stack 11. The power supply 18 draws current from the fuel cell stack 11. In the illustrated example, the maximum power output of each fuel cell 10 is 100 kW.

[0016] The control device 20 controls the operating state of each fuel cell 10. Specifically, the control device 20 sends a control signal to each fuel cell 10 to operate the fuel cell 10 in a plurality of operating modes including a normal operating mode and a standby operating mode. The control device 20 also sends a control signal to each fuel cell 10 to stop the operation of the fuel cell 10 or to start up a fuel cell 10 whose operation has been stopped. That is, upon receiving the control signal, each fuel cell 10 is set to one of the operating states of a normal operating mode, a standby operating mode, or a stopped operating state.

[0017] Here, when the fuel cell 10 is operated in the normal operation mode, it is operated with a power generation output that provides a power generation efficiency equal to or higher than a first power generation efficiency. By having the power generation efficiency of the fuel cell 10 operated in the normal operation mode be equal to or higher than a predetermined power generation efficiency, it is possible to make the power generation efficiency of the entire fuel cell system 1 equal to or higher than the predetermined power generation efficiency. Furthermore, when the fuel cell 10 is operated in the standby operation mode, it is operated with a power generation output that provides a power generation efficiency equal to or lower than a second power generation efficiency that is lower than the first power generation efficiency. In the illustrated example, when the fuel cell 10 is operated in the standby operation mode, it is disconnected from the system that supplies power to the fuel cell system 1 and is operated independently.

[0018] In the illustrated example, the fuel cell 10 is operated at a power output of 40 to 60% or 42% to 58% of the maximum power output of the fuel cell when operated in the normal operation mode. In the illustrated example, the fuel cell 10 is operated at a power output at which the power generation efficiency of the fuel cell 10 is maximized when operated in the normal operation mode. In general, the power generation efficiency of the fuel cell 10 is maximized when operated at a power output of about 50% of the maximum power output of the fuel cell 10. In the illustrated example, each fuel cell 10 is operated at a power output of 50% of its maximum power output when operated in the normal operation mode. As described above, in the illustrated example, the maximum power generation output of each fuel cell 10 is 100 kW, so the power generation output of the fuel cell 10 operated in the normal operation mode is 50 kW.

[0019] Also, in the illustrated example, when the fuel cell 10 is operated in standby operation mode, it is operated at a power generation output that is 5 to 15% of the maximum power generation output of the fuel cell 10. In the illustrated example, when the fuel cell 10 is operated in standby operation mode, it is operated at a power generation output that is 10% of the maximum power generation output of the fuel cell 10. As described above, in the illustrated example, the maximum power generation output of each fuel cell 10 is 100 kW, so the power generation output of the fuel cell 10 operated in standby operation mode is 10 kW.

[0020] In the following, the fuel cell 10 operated in the normal operation mode is also referred to as the "normal mode fuel cell" or "normal mode FC." In the following, the fuel cell 10 operated in the standby operation mode is also referred to as the "standby mode fuel cell" or "standby mode FC." In the following, the fuel cell 10 in a stopped state is also referred to as the "stopped fuel cell" or "stopped FC." In the following, the power generation output of the fuel cell 10 operated in the normal operation mode is also referred to as the "normal power generation output." In the following, the power generation output of the fuel cell 10 operated in the standby operation mode is also referred to as the "standby power generation output."

[0021] Fig. 3 is a block diagram showing a schematic configuration of the control device 20. As shown in Fig. 3, the control device 20 according to the first embodiment has an information acquisition unit 21, a command acquisition unit 22, a number of normally operating vehicles determination unit 23, and an operating state determination unit 24.

[0022] The information acquisition unit 21 acquires the number of normal mode fuel cells 10, the number of standby mode fuel cells 10, and the number of startups of each fuel cell 10. The information acquisition unit 21 receives, for example, the number of normal mode fuel cells 10, the number of standby mode fuel cells 10, and the number of startups of each fuel cell 10 from the operating state determination unit 24.

[0023] The command acquisition unit 22 acquires an output command indicating the total power generation output that the fuel cell system 1 should generate. In the illustrated example, the command acquisition unit 22 acquires the total power generation output from the operation device 30. Hereinafter, the total power generation output indicated by the output command is also referred to as "commanded total power generation output." Moreover, the total power generation output being output by the fuel cell system 1 is also referred to as "current total power generation output."

[0024] When the commanded total power generation output differs from the current total power generation output, the normally operating number determination unit 23 determines the number of fuel cells 10 to be operated in the normal operation mode based on the output command, and inputs the determined number to the operation state determination unit 24. The normally operating number determination unit 23 determines the number of fuel cells 10 to be operated in the normal operation mode based on the result of dividing the commanded total power generation output by the normal power generation output. For example, when the commanded total power generation output is 200 kW and the normal power generation output is 50 kW, the result of dividing the commanded total power generation output by the normal power generation output is 200 kW / 50 kW=4. Therefore, the normally operating number determination unit 23 determines the number of fuel cells 10 to be operated in the normal operation mode to be 4. Note that when the commanded total power generation output is equal to the current total power generation output, no input is made from the normally operating number determination unit 23 to the operation state determination unit 24. Hereinafter, the number of fuel cells 10 to be operated in the normal operation mode determined by the normally operating number determination unit 23 is also referred to as the "commanded normal mode number."

[0025] The operating state determination unit 24 determines the operating state of each fuel cell 10 based on the commanded normal mode number determined by the normally operating number determination unit 23. When the commanded total power generation output is lower than the current total power generation output (thus, when the commanded normal mode number is smaller than the number of normal mode fuel cells), the operating state determination unit 24 changes the operating mode of at least one normal mode fuel cell 10 to the standby operating mode. When the commanded total power generation output is higher than the current total power generation output (thus, when the commanded normal mode number is greater than the number of normal mode fuel cells), the operating state determination unit 24 changes the operating mode of at least one standby mode fuel cell 10 to the normal operating mode, or changes the operating mode of at least one stopped fuel cell 10 to the normal operating mode.

[0026] For example, assume that the normal power generation output is 50 kW, the number of normal mode fuel cells is 5, and the current total power generation output is 250 kW. In this state, when an output command for a commanded total power generation output of 200 kW is input, the normal operation number determination unit 23 determines the commanded number of normal mode fuel cells to be 4. In this case, the operation state determination unit 24 changes the operation mode of one of the five normal mode fuel cells 10 to the standby operation mode.

[0027] Alternatively, for example, assume that the normal power generation output is 50 kW, the number of normal mode fuel cells is three, and the current total power generation output is 150 kW. In this state, when an output command for a commanded total power generation output of 200 kW is input, the normal operation number determination unit 23 determines the commanded number of normal mode units to be four. In this case, the operation state determination unit 24 changes the operation mode of one of the multiple fuel cells 10 other than the normal mode fuel cell 10 to the normal operation mode.

[0028] When changing the operation mode of the normal mode fuel cell 10 to the standby operation mode, if there are multiple normal mode fuel cells 10, the operation state determination unit 24 selects the fuel cell 10 whose operation mode is to be changed to the standby operation mode as follows: That is, the operation state determination unit 24 selects, among the normal mode fuel cells 10, the fuel cell 10 with the least number of startups acquired by the information acquisition unit 21 as the fuel cell whose operation mode is to be changed to the standby operation mode.

[0029] Furthermore, when changing the stopped fuel cell 10 to the normal operation mode, if there are multiple stopped fuel cells 10, the operation state determination unit 24 selects the fuel cell 10 to be changed to the normal operation mode as follows: That is, the operation state determination unit 24 selects, among the stopped fuel cells 10, the fuel cell 10 with the least number of startups acquired by the information acquisition unit 21 as the fuel cell to be changed to the normal operation mode.

[0030] In addition, when the number of standby mode fuel cells 10 acquired by the information acquisition unit 21 is greater than a predetermined number N, the operating state determination unit 24 determines, among the standby mode fuel cells 10, the fuel cell 10 that has been started up the least number of times acquired by the information acquisition unit 21 as the fuel cell 10 whose operation will be stopped.

[0031] In this way, in the fuel cell system 1 of the first embodiment, when the number of normal mode fuel cells 10 is greater than the number of fuel cells 10 required to output the commanded total power generation output, the operation state of the excess normal mode fuel cells 10 is not immediately switched to a stopped state, but is changed to a standby operation mode. Alternatively, in the fuel cell system 1 of the first embodiment, when the number of normal operation mode fuel cells 10 is less than the number of fuel cells 10 required to output the commanded total power generation output, the number of fuel cells 10 operated in the normal operation mode is increased, but at this time, if there are standby mode fuel cells 10, the standby mode fuel cells 10 are given priority over the stopped fuel cells 10 and are changed to the normal operation mode. By controlling the multiple fuel cells 10 in this way, the opportunity to start the fuel cells 10 in the stopped state when increasing the total power generation output of the fuel cell system 1 is reduced. As a result, the responsiveness of the power generation output of the fuel cell system 1 can be improved.

[0032] In addition, in the fuel cell system 1 of the first embodiment, the fuel cell 10 with the smallest number of start / stop cycles is selected as the fuel cell 10 to be changed from the normal operation mode to the standby operation mode. Furthermore, the fuel cell 10 with the smallest number of start / stop cycles is selected as the fuel cell 10 to be changed from the standby operation mode to the operation stop state. By changing the fuel cell 10 with the smallest number of start / stop cycles from the normal operation mode to the standby operation mode and also changing from the standby operation mode to the operation stop state, it is possible to suppress the occurrence of a bias in the number of start / stop cycles among the multiple fuel cells 10. In other words, it is possible to suppress the occurrence of a situation in which the number of start / stop cycles of some of the multiple fuel cells 10 is significantly higher than the number of start / stop cycles of the other fuel cells 10. This makes it possible to suppress the deterioration of some of the multiple fuel cells 10 before the deterioration of the other fuel cells 10. As a result, it is possible to operate the fuel cell system 1 with high reliability.

[0033] Furthermore, in the fuel cell system 1 of the first embodiment, the fuel cell 10 that has the fewest number of start / stop counts is selected from among the stopped fuel cells 10 as the fuel cell 10 to be changed from the stopped operation state to the standby operation mode. This also makes it possible to prevent imbalances in the number of start / stop counts among the multiple fuel cells 10, and to prevent some of the multiple fuel cells 10 from deteriorating earlier than the other fuel cells 10.

[0034] As described above, when the commanded total power generation output is equal to the current total power generation output, no input is made from the number of normally operating units determination unit 23 to the operation state determination unit 24. Therefore, in this case, the operation state determination unit 24 does not change the operation state of each fuel cell 10. In other words, in this case, the operation mode of the normal mode fuel cell 10 is maintained in the normal operation mode, the operation mode of the standby mode fuel cell 10 is maintained in the standby operation mode, and the stopped fuel cell 10 is maintained in a stopped state.

[0035] Next, a control method for the fuel cell system 1 will be described with reference to Figures 4 and 5. Here, the fuel cell system 1 includes six fuel cells 10, each of the fuel cells 10 has a maximum power generation output of 100 kW, and each fuel cell 10 has a normal power generation output of 50 kW. The command total power generation output is set to any one of 0 kW, 50 kW, 100 kW, 150 kW, 200 kW, 250 kW, and 300 kW.

[0036] As shown in FIG. 4, the command acquisition unit 22 acquires an output command indicating a total power generation output (command total power generation output) that the fuel cell system 1 should generate from the operation device 30 (step S11).

[0037] Next, the normally-operated unit number determination unit 23 determines whether the commanded total power generation output is equal to the current total power generation output (step S12). If the commanded total power generation output is equal to the current total power generation output (YES in step S12), the operating state of each fuel cell 10 is maintained.

[0038] On the other hand, if the commanded total power generation output is different from the current total power generation output in step S12 (NO in step S12), the normally operated number determination unit 23 judges whether the commanded total power generation output is greater than the current total power generation output (step S13). In step S13, the normally operated number determination unit 23 may judge whether the value (commanded number of normal mode units) obtained by dividing the commanded total power generation output by the normal power generation output is greater than the number of normal mode fuel cells 10. Then, if the commanded total power generation output is greater than the current total power generation output (or if the commanded number of normal mode units is greater than the number of normal mode fuel cells 10) (YES in step S13), the normally operated number determination unit 23 passes the commanded number of normal mode units to the operating state determination unit 24. Then, the operating state determination unit 24 acquires information on the number of standby mode fuel cells 10 from the information acquisition unit 21, and judges whether the number of standby mode fuel cells 10 is 1 or more (step S14). If the number of standby mode fuel cells 10 is one or more (YES in step S14), the operating state determination unit 24 changes the operating mode of one standby mode fuel cell 10 to the normal operating mode (step S15). As a result, the fuel cell 10 is operated in the normal operating mode. Thereafter, the judgment of step S12 is performed again. Also, in step S15, the operating state determination unit 24 passes information on the operating state of each fuel cell 10 to the information acquisition unit 21.

[0039] In step S14, if there is no standby mode fuel cell 10 (NO in step S14), the operating state determination unit 24 changes the one fuel cell 10 that has the least number of start / stop counts among the stopped fuel cells 10 to the normal operating mode (step S16). As a result, the fuel cell 10 is started and operated in the normal operating mode. After that, the judgment in step S12 is performed again.

[0040] Next, a case where the commanded total power generation output is smaller than the current total power generation output in step S13 (or the commanded normal mode number is smaller than the number of normal mode fuel cells 10) (NO in step S13) will be described. In this case, the normal operation number determination unit 23 passes the commanded normal mode number to the operation state determination unit 24. Then, the operation state determination unit 24 acquires information on the number of starts and stops of each fuel cell 10 from the information acquisition unit 21, and changes the operation mode of one fuel cell among the normal mode fuel cells 10 with the fewest number of starts and stops to the standby operation mode (step S17). As a result, the fuel cell 10 is operated in the standby operation mode. After that, the operation state determination unit 24 determines whether the number of standby mode fuel cells 10 is greater than a predetermined number N (step S18). In step S18, if it is determined that the number of standby mode fuel cells 10 is greater than the predetermined number N (YES in step S18), the operating state determination unit 24 stops the operation of the fuel cell 10 with the least number of starts and stops among the standby mode fuel cells 10 (step S19). At this time, the number of fuel cells 10 changed to the stopped state is equal to the number of standby mode fuel cells 10 minus the predetermined number N. This value represents an excessive number of standby mode fuel cells 10. As a result of step S19, the standby mode fuel cells 10 with the least number of starts and stops are stopped by the excessive number. Also, in step S19, the operating state determination unit 24 passes information on the operating state of each fuel cell 10 to the information acquisition unit 21. Then, the determination in step S12 is performed again.

[0041] On the other hand, if it is determined in step S18 that the number of standby mode fuel cells 10 is equal to or less than the predetermined number N (NO in step S18), the operating state determination unit 24 does not change the operating state of the standby mode fuel cells 10. In addition, the operating state determination unit 24 passes information on the operating state of each fuel cell 10 to the information acquisition unit 21. Thereafter, the determination in step S12 is performed again.

[0042] In the embodiment described above, if there is no standby mode fuel cell 10 in step S14 (NO in step S14), the stopped fuel cell 10 is started up, but this is not limited to the above. If the result in step S14 is NO and there is a fuel cell 10 in transition from a standby operation mode (or a normal operation mode) to a stopped operation state among the multiple fuel cells 10, the operation state determination unit 24 may change the operation state of one of the fuel cells in transition to a stopped operation state to the normal operation mode. This makes it possible to prevent an increase in the number of start-ups and stoppages of that fuel cell.

[0043] <Second embodiment> Next, a fuel cell system 1 according to a second embodiment will be described with reference to Figures 6 to 8. The fuel cell system 1 according to the second embodiment shown in Figure 6 differs from the fuel cell system 1 according to the first embodiment in that the control device 20 includes a predicted command acquisition unit 25 and a unit 26 for determining the number of operating vehicles on standby. The other configurations are substantially the same as those of the fuel cell system 1 according to the first embodiment shown in Figures 1 to 5. In the second embodiment shown in Figures 6 to 8, the same parts as those in the first embodiment shown in Figures 1 to 5 are denoted by the same reference numerals and detailed description thereof will be omitted.

[0044] The predicted command acquisition unit 25 acquires a predicted output command indicating the total power generation output that the fuel cell system 1 should generate in the future. In the illustrated example, the predicted command acquisition unit 25 acquires the predicted output command from the operation device 30. A predicted output command indicating the total power generation output that the fuel cell system 1 should generate between 20 minutes and 40 minutes from now is input from the operation device 30 to the predicted command acquisition unit 25 every 20 minutes. Note that, hereinafter, the total power generation output indicated by the predicted output command is also referred to as the "predicted total power generation output."

[0045] The standby operation number determination unit 26 receives the predicted output command and calculates the number of fuel cells 10 required to output the predicted total power generation output. Specifically, the unit calculates the number of fuel cells 10 required to output the predicted total power generation output by dividing the predicted total power generation output by the normal power generation output. The calculated number is then compared with the sum of the number of normal mode fuel cells 10 and the number of standby mode fuel cells 10 at the current time (at the time the predicted output command is input). If the calculated number is greater than the sum, the standby operation number determination unit 26 inputs the difference between the calculated number and the sum to the operation state determination unit 24 as the number of fuel cells 10 to be changed from the operation stop state to the standby operation mode. On the other hand, if the calculated number is equal to or less than the sum, no input is made from the standby operation number determination unit 26 to the operation state determination unit 24.

[0046] In the following, the number of fuel cells 10 required to output the predicted total power generation output is also referred to as the "predicted required number." The sum of the number of normal mode fuel cells and the number of standby mode fuel cells at the present time (at the time the predicted output command is input) is also referred to as the "current number of operating units." The difference between the predicted required number and the current number of operating units is also referred to as the "deficient number of operating units."

[0047] The operating state determination unit 24 receives the shortage number M of operating units from the standby operating unit number determination unit 26 and switches the stopped fuel cells 10 to the standby operating mode. In this case, the operating state determination unit 24 switches the stopped fuel cells 10 with the fewest number of starts and stops among the stopped fuel cells 10 to the standby operating mode for the shortage number M of operating units calculated by the standby operating unit number determination unit 26. As a result, the fuel cells 10 are started up for the shortage number M of operating units and operated in the standby operating mode. As a result, a number of fuel cells 10 sufficient to output the predicted total power generation output are operated in the normal operating mode or the standby operating mode.

[0048] Furthermore, when the commanded normal mode number is input from the normally operating number determination unit 23, the operating state determination unit 24 calculates the difference between the commanded normal mode number and the number of normal mode fuel cells as the number of fuel cells operating in the normal operation mode that is insufficient to output the commanded total power generation output. This is also the number of fuel cells 10 that should be changed from the standby operation mode to the normal operation mode. Then, the standby mode fuel cells 10 are changed to the normal operation mode by the calculated number. Hereinafter, the number of fuel cells 10 that should be changed from the standby operation mode to the normal operation mode in response to the input of the commanded normal mode number is also referred to as the "deficient number of normal mode units."

[0049] In this way, in the fuel cell system 1 of the second embodiment, a predicted output command is input periodically. Then, when the predicted required number is greater than the number of currently operating units, the stopped fuel cell is started and operated in the standby operation mode. As a result, when the commanded total power generation output increases and the number of fuel cells 10 to be operated in the normal operation mode increases, it is only necessary to change the standby mode fuel cell 10 to the normal operation mode, and there is no need to start the stopped fuel cell 10. As a result, the responsiveness of the power generation output of the fuel cell system 1 can be improved. In addition, when changing the stopped fuel cell 10 to the standby operation mode, the fuel cell 10 with the least number of start / stops among the stopped fuel cells 10 is started, thereby preventing the occurrence of a bias in the number of start / stops among the multiple fuel cells 10. As a result, it is possible to prevent some of the multiple fuel cells 10 from deteriorating earlier than the other fuel cells 10.

[0050] Next, a control method for the fuel cell system 1 of the second embodiment will be described with reference to Figures 7 and 8. Note that the process shown in Figure 7 is periodically performed independently of the process shown in Figure 8.

[0051] 7, a predicted output command is periodically (e.g., every 20 minutes) input from the operation device 30 to the predicted command acquisition unit 25 (step S21). As described above, the predicted output command indicates a predicted total power generation output that should be generated by the fuel cell system 1 in the future (e.g., between 20 minutes and 40 minutes from now).

[0052] When a predicted output command is input to the predicted command acquisition unit 25, the standby operating unit number determination unit 26 calculates the number of fuel cells required to output the predicted total power generation output (predicted required number). Then, the calculated predicted required number is compared with the current number of operating units (step S22). In step S22, if the predicted required number is greater than the current number of operating units (YES in step S22), the shortage number of operating units M is calculated from the predicted required number and the current number of operating units. Then, the obtained shortage number of operating units M is input to the operating state determination unit 24.

[0053] When the shortfall in the number of operating units M is input from the standby operating unit number determination unit 26, the operating state determination unit 24 changes the fuel cell with the least number of start / stop counts among the stopped fuel cells 10 to the standby operating mode by the shortfall in the number M (step S23). As a result, the fuel cell 10 is started up and operated in the standby operating mode. Also, in step S23, the operating state determination unit 24 passes information on the operating state of each fuel cell 10 to the information acquisition unit 21.

[0054] In step S22, if the predicted required number of units is equal to or less than the current number of operating units (NO in step S22), no input is made from the standby operating unit number determination unit 26 to the operating state determination unit 24. As a result, the stopped fuel cells 10 are not started up in response to the input of a predicted output command.

[0055] After the process shown in Fig. 7, when the command acquisition unit 22 acquires an output command from the operation device 30 as shown in Fig. 8 (step S11), the normally-operated number determination unit 23 makes a judgment in step S12, similar to the case shown in Fig. 4. If the answer is NO in step S12, the normally-operated number determination unit 23 makes a judgment in step S13. If the answer is YES in step S13, the number of normally-operated fuel cells required to output the commanded total power generation output (commanded normal mode number) is calculated.

[0056] Next, the normal operation number determination unit 23 calculates the number of fuel cells in normal operation that is insufficient to output the commanded total power generation output (deficient normal mode number), and inputs the calculated value to the operation state determination unit 24. Next, the operation state determination unit 24 changes the standby mode fuel cells 10 to the normal operation mode by the deficient normal mode number (step S24). As a result, the fuel cells 10 are changed from the standby operation mode to the normal operation mode by the deficient normal mode number.

[0057] It should be noted that various modifications can be made to the above-described embodiment. For example, in the above-described embodiment, the command total power output is any of 0 kW, 50 kW, 100 kW, 150 kW, 200 kW, 250 kW, and 300 kW, but is not limited thereto. The command total power output may be any value, such as 42 kW, 58 kW, and 142 kW. In this case, the normal mode fuel cell 10 may be operated at any power output as long as it is operated at a power output that is 40 to 60% of its maximum power output. For example, when the maximum power output of each fuel cell 10 is 100 kW and the command total power output is 42 kW, one normal mode fuel cell 10 may be operated at a power output that is 42% of its maximum power output. In addition, when the maximum power generation output of each fuel cell 10 is 100 kW and the commanded total power generation output is 142 kW, two normal mode fuel cells 10 may be operated at a power generation output that is 50% of their maximum power generation output, and one normal mode fuel cell 10 may be operated at a power generation output that is 42% of its maximum power generation output.

[0058] As described above, the fuel cell system 1 according to the first and second embodiments includes a plurality of fuel cells 10 and a control device 20 that controls the operating state of each fuel cell 10. Each fuel cell 10 can be operated in a plurality of operating modes including a normal operation mode in which the fuel cell 10 is operated at a power output at which the power generation efficiency is equal to or higher than a first power generation efficiency, and a standby operation mode in which the fuel cell 10 is operated at a power output at which the power generation efficiency is equal to or lower than a second power generation efficiency that is lower than the first power generation efficiency. The control device 20 includes a command acquisition unit 22, a normally operated number of units determination unit 23, and an operating state determination unit 24. The command acquisition unit 22 acquires an output command indicating the total power generation output to be generated by the fuel cell system 1. The normally operated number of units determination unit 23 determines the number of fuel cells 10 to be operated in the normal operation mode based on the total power generation output indicated by the output command. The operating state determination unit 24 determines the operating state of each fuel cell 10 based on the number determined by the normally operated number of units determination unit 23. When the total power generation output indicated by the output command is lower than the total power generation output generated by the fuel cell system 1, or when the number determined by the normal operation number determination unit 23 is smaller than the number of fuel cells 10 operated in the normal operation mode, the operation state determination unit 24 changes the operation mode of at least one of the fuel cells 10 operated in the normal operation mode to the standby operation mode. Also, when the total power generation output indicated by the output command is higher than the total power generation output generated by the fuel cell system 1, or when the number determined by the normal operation number determination unit 23 is greater than the number of fuel cells 10 operated in the normal operation mode, the operation state determination unit 24 changes the operation mode of at least one of the fuel cells 10 operated in the standby operation mode to the normal operation mode.

[0059] According to such a fuel cell system 1, the power generation efficiency of the entire fuel cell system 1 can be made equal to or higher than a predetermined power generation efficiency. In addition, when the number of fuel cells 10 operated in the normal operation mode is greater than the number of fuel cells 10 required to output the total power generation output indicated by the output command, the excess normal mode fuel cells 10 are not immediately put into a stopped state, but are changed to a standby operation mode. Alternatively, when the number of fuel cells 10 operated in the normal operation mode is less than the number of fuel cells 10 required to output the total power generation output indicated by the output command, the fuel cells 10 operated in the standby operation mode are changed to the normal operation mode. By controlling the multiple fuel cells 10 in this manner, the number of occasions when the fuel cells 10 in the stopped state are started up when the total power generation output of the fuel cell system 1 is increased is reduced. As a result, the responsiveness of the power generation output of the fuel cell system 1 can be improved.

[0060] In the fuel cell system 1 according to the first and second embodiments, the control device 20 further includes an information acquisition unit 21 that acquires the number of startups of each fuel cell 10. The operating state determination unit 24 changes the operating mode of the fuel cell 10 that has the fewest number of startups acquired by the information acquisition unit 21 among the fuel cells 10 operated in the normal operating mode to the standby operating mode. The fuel cell 10 operated in the standby operating mode is likely to be stopped thereafter. Therefore, by changing the operating mode of the fuel cell 10 that has the fewest number of startups to the standby operating mode, it is possible to prevent the occurrence of a bias in the number of startups among the multiple fuel cells 10. As a result, it is possible to prevent some of the multiple fuel cells 10 from deteriorating earlier than the other fuel cells 10.

[0061] In the fuel cell system 1 according to the first and second embodiments, the control device 20 further includes an information acquisition unit 21 that acquires the number of fuel cells 10 operating in standby operation mode and the number of startups of each fuel cell 10. When the number of fuel cells 10 operating in standby operation mode acquired by the information acquisition unit 21 is greater than a predetermined number N, the operation state determination unit 24 determines the fuel cell 10 operating in standby operation mode that has the least number of startups acquired by the information acquisition unit 21 as the fuel cell to be stopped. This makes it possible to prevent the occurrence of bias in the number of startups among the multiple fuel cells 10. As a result, it is possible to prevent some of the multiple fuel cells 10 from deteriorating earlier than the other fuel cells 10.

[0062] In the fuel cell system 1 according to the first and second embodiments, the control device 20 further includes an information acquisition unit 21 that acquires the number of startups of each fuel cell 10. When the total power generation output indicated by the output command is higher than the total power generation output generated by the fuel cell system 1, or when the number of fuel cells 10 operated in the normal operation mode determined by the normal operation number determination unit 23 is greater than the number of fuel cells 10 operated in the normal operation mode, the operation state determination unit 24 determines the fuel cell 10 with the least number of startups acquired by the information acquisition unit 21 among the fuel cells 10 whose operation is stopped as the fuel cell 10 to be operated in the normal operation mode. This makes it possible to prevent the occurrence of bias in the number of startups among the multiple fuel cells 10. As a result, it is possible to prevent some of the multiple fuel cells 10 from deteriorating earlier than the other fuel cells 10.

[0063] In the fuel cell system 1 according to the second embodiment, the information acquisition unit 21 acquires the number of fuel cells 10 operating in the standby operation mode. When the number acquired by the information acquisition unit 21 is less than a predetermined number (specifically, the difference between the predicted number of fuel cells required and the number of fuel cells in the normal mode at the time when the predicted output command is input), the operation state determination unit 24 determines the fuel cell 10 with the least number of startup times acquired by the information acquisition unit 21 among the fuel cells 10 whose operation is stopped as the fuel cell 10 to be operated in the standby operation mode. This more effectively reduces the number of opportunities to start the fuel cell 10 in the stopped state when increasing the total power generation output of the fuel cell system 1. As a result, the responsiveness of the power generation output of the fuel cell system 1 can be more effectively improved. In addition, it is possible to suppress the occurrence of bias in the number of startup times among the multiple fuel cells 10. As a result, it is possible to suppress the occurrence of a situation in which some of the multiple fuel cells 10 deteriorate before the other fuel cells 10.

[0064] In the fuel cell systems 1 according to the first and second embodiments, when the fuel cell 10 is operated in a normal operation mode, it is operated at a power generation output that is 40 to 60% of the maximum power generation output of the fuel cell 10. This makes it possible to effectively improve the power generation efficiency of the entire fuel cell system 1.

[0065] In the fuel cell system 1 according to the first and second embodiments, when the fuel cell 10 is operated in a normal operation mode, it is operated at a power output that maximizes the power generation efficiency of the fuel cell 10. This makes it possible to more effectively improve the power generation efficiency of the entire fuel cell system 1.

[0066] In the fuel cell systems 1 according to the first and second embodiments, the fuel cell 10 is operated in the standby operation mode with a power generation output that is 5 to 15% of the maximum power generation output of the fuel cell 10.

[0067] The control methods according to the first and second embodiments are methods for controlling a fuel cell system 1 including a plurality of fuel cells 10 that can be operated in a plurality of operation modes, including a normal operation mode in which the system is operated at a high-efficiency power output with a power generation efficiency equal to or higher than a first power generation efficiency, and a standby operation mode in which the system is operated at a low-efficiency power output with a power generation efficiency equal to or lower than a second power generation efficiency that is lower than the first power generation efficiency. This control method includes an output command acquisition step, a normal operation number determination step, and an operation state determination step. In the output command acquisition step, an output command indicating the total power generation output to be generated by the fuel cell system 1 is acquired. In the normal operation number determination step, the number of fuel cells 10 to be operated in the normal operation mode is determined based on the total power generation output indicated by the output command. In the operation state determination step, the operation state of each fuel cell 10 is determined based on the number determined in the normal operation number determination step. Specifically, in the operation state determination step, if the total power generation output indicated by the output command is lower than the total power generation output generated by the fuel cell system 1, or if the number determined in the normal operation number determination step is smaller than the number of fuel cells 10 operated in the normal operation mode, the operation mode of at least one of the fuel cells 10 operated in the normal operation mode is changed to the standby operation mode. Also, in the operation state determination step, if the total power generation output indicated by the output command is higher than the total power generation output generated by the fuel cell system 1, or if the number determined in the normal operation number determination step is larger than the number of fuel cells 10 operated in the normal operation mode, the operation mode of at least one of the fuel cells 10 operated in the standby operation mode is changed to the normal operation mode.

[0068] According to such a control method for the fuel cell system 1, the power generation efficiency of the entire fuel cell system 1 can be made equal to or higher than a predetermined power generation efficiency. In addition, when the number of fuel cells 10 operated in the normal operation mode is greater than the number of fuel cells 10 required to output the total power generation output indicated by the output command, the operation of the excess normal mode fuel cells 10 is not immediately stopped, but is changed to a standby operation mode. Alternatively, when the number of fuel cells 10 operated in the normal operation mode is less than the number of fuel cells 10 required to output the total power generation output indicated by the output command, the fuel cells 10 operated in the standby operation mode are changed to the normal operation mode. By controlling the multiple fuel cells 10 in this manner, the number of times that the fuel cells 10 that are stopped are started up when the total power generation output of the fuel cell system 1 is increased is reduced. As a result, the responsiveness of the power generation output of the fuel cell system 1 can be improved.

[0069] Although some embodiments and modifications of the present invention have been described, these embodiments and modifications are presented as examples and are not intended to limit the scope of the invention. These new embodiments and modifications can be implemented in various other forms, and various omissions, substitutions, and modifications can be made without departing from the gist of the invention. These embodiments and modifications are included in the scope and gist of the invention, and are included in the scope of the invention and its equivalents described in the claims. In addition, it is of course possible to combine these embodiments and modifications in part as appropriate within the gist of the present invention. [Explanation of symbols]

[0070] 1: fuel cell system, 10: fuel cell, 11: fuel cell stack, 12: anode, 13: cathode, 20: control device, 21: information acquisition unit, 2: command acquisition unit, 23: unit for determining number of normally operating units, 24: operating state determination unit, 30: operation device

Claims

1. A plurality of fuel cells; A control device for controlling the operating state of each fuel cell; A fuel cell system comprising: each fuel cell is operable in a plurality of operation modes including a normal operation mode in which the fuel cell is operated at a power generation output at which the power generation efficiency is equal to or greater than a first power generation efficiency, and a standby operation mode in which the fuel cell is operated at a power generation output at which the power generation efficiency is equal to or less than a second power generation efficiency that is lower than the first power generation efficiency; The control device includes: a command acquisition unit that acquires an output command indicating a total power output to be generated by the fuel cell system; a normal operation number determination unit that determines the number of fuel cells that should be operated in a normal operation mode based on the total power generation output indicated by the output command; an operating state determination unit that determines an operating state of each fuel cell based on the number determined by the normally operating number determination unit; an information acquisition unit that acquires the number of fuel cells operating in a standby operation mode and the number of times each fuel cell has been started; having When the total power generation output indicated by the output command is lower than the total power generation output being generated by the fuel cell system, or when the number of fuel cells determined by the normal operation number determination unit is smaller than the number of fuel cells being operated in the normal operation mode, the operation state determination unit changes the operation mode of the fuel cell that is operated in the normal operation mode and has the least number of startups acquired by the information acquisition unit to a standby operation mode, When the total power generation output indicated by the output command is higher than the total power generation output being generated by the fuel cell system, or when the number of fuel cells determined by the normal operation number determination unit is greater than the number of fuel cells being operated in a normal operation mode, the operation state determination unit changes the operation mode of at least one of the fuel cells being operated in a standby operation mode to a normal operation mode, A fuel cell system in which, when the number of fuel cells operating in standby operation mode acquired by the information acquisition unit is greater than a predetermined number, the operation state determination unit determines, among the fuel cells operating in standby operation mode, the fuel cell that has been started up the least number of times acquired by the information acquisition unit as the fuel cell to be stopped from operating.

2. The control device further includes an information acquisition unit that acquires the number of startups of each fuel cell, 2. The fuel cell system according to claim 1, wherein the operating state determination unit changes the operating mode of a fuel cell that has the fewest number of startups acquired by the information acquisition unit among the fuel cells operated in the normal operating mode to a standby operating mode.

3. The control device further includes an information acquisition unit that acquires the number of startups of each fuel cell, 3. The fuel cell system of claim 1, wherein when the total power generation output indicated by the output command is higher than the total power generation output generated by the fuel cell system, or when the number determined by the number of normally operating fuel cells determination unit is greater than the number of fuel cells operating in normal operation mode, the operating state determination unit determines the fuel cell that has been stopped and has the fewest number of startups acquired by the information acquisition unit as the fuel cell to be operated in normal operation mode.

4. the information acquisition unit acquires the number of fuel cells operating in a standby operation mode; 4. The fuel cell system of claim 3, wherein when the number of fuel cells acquired by the information acquisition unit is less than a predetermined number, the operating state determination unit determines, among the fuel cells whose operation is stopped, the fuel cell that has been started the least number of times acquired by the information acquisition unit as the fuel cell to be operated in standby operation mode.

5. 5. The fuel cell system according to claim 1, wherein the fuel cell is operated at a power generation output that is 40 to 60% of a maximum power generation output of the fuel cell when operated in a normal operation mode.

6. 6. The fuel cell system according to claim 1, wherein, when the fuel cell is operated in a normal operation mode, the fuel cell is operated at a power output that maximizes the power generation efficiency of the fuel cell.

7. 7. The fuel cell system according to claim 1, wherein, when the fuel cell is operated in a standby operation mode, the fuel cell is operated at a power generation output that is 5 to 15% of a maximum power generation output of the fuel cell.

8. A method for controlling a fuel cell system including a plurality of fuel cells, each of which can be operated in a plurality of operation modes including a normal operation mode in which the fuel cells are operated at a high-efficiency power generation output having a power generation efficiency equal to or higher than a first power generation efficiency, and a standby operation mode in which the fuel cells are operated at a low-efficiency power generation output having a power generation efficiency equal to or lower than a second power generation efficiency that is lower than the first power generation efficiency, an output command acquisition step of acquiring an output command indicating a total power output to be generated by the fuel cell system; a normal operation number determination step of determining the number of fuel cells to be operated in a normal operation mode based on the total power generation output indicated by the output command; an operating state determination step of determining an operating state of each fuel cell based on the number determined in the normally operating number determination step; an information acquisition step of acquiring the number of fuel cells operating in a standby operation mode and the number of times each fuel cell has been started; Equipped with In the operating state determination step, if the total power generation output indicated by the output command is lower than the total power generation output being generated by the fuel cell system, or if the number of fuel cells determined in the normal operation number determination step is smaller than the number of fuel cells being operated in the normal operation mode, changing the operation mode of the fuel cell that is being operated in the normal operation mode and has the least number of startups acquired in the information acquisition step to a standby operation mode; when the total power generation output indicated by the output command is higher than the total power generation output being generated by the fuel cell system, or when the number of fuel cells determined in the step of determining the number of fuel cells in normal operation is greater than the number of fuel cells operating in normal operation mode, changing the operation mode of at least one of the fuel cells operating in standby operation mode to a normal operation mode; A control method in which, when the number of fuel cells operating in standby operation mode acquired in the information acquisition process is greater than a predetermined number, the operating state determination process determines, among the fuel cells operating in standby operation mode, the fuel cell that has been started up the least number of times acquired in the information acquisition process as the fuel cell to be stopped from operating.

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