Fuel cell system, control device, and control method

Abstract

To provide a fuel cell system capable of regulating output currents of a plurality of fuel cells in which several fuel cell stacks are connected in series, a control device and a control method.SOLUTION: A fuel cell system comprises a first fuel cell group, a first power converter, a second fuel cell group, a second power converter, and a first pipe. The first fuel cell group is configured by connecting a plurality of fuel cell stacks in series. The first power converter is capable of controlling first generation power of the first fuel cell group in accordance with a first output current. The second fuel cell group is configured by connecting a plurality of fuel cell stacks corresponding to the plurality of fuel cell stacks, respectively, in series. The second power converter is capable of controlling second generation power of the second fuel cell group in accordance with a second output current. The first pipe supplies an oxygen containing gas to the plurality of fuel cell stacks of the first fuel cell group and the plurality of fuel cell stacks of the second fuel cell group.SELECTED DRAWING: Figure 2

Description

[Technical field]

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

[0002] Fuel cell systems have been known for some time as systems that directly convert the chemical energy of fuel into electricity. These fuel cell systems produce electricity directly by electrochemically reacting hydrogen-containing gas with oxygen-containing gas. This makes the system highly efficient at producing electrical energy, while also being quiet and not emitting harmful exhaust gases, making it an environmentally friendly system. In the past, large PAFCs (phosphoric acid type) were the main type of fuel cells developed, but in recent years, the development of PEFCs (polymer electrolyte fuel cells) has become more active. In particular, PEFC home fuel cell systems were commercialized in 2009 and have become widely used, with more than 400,000 units being installed in 2021.

[0003] Fuel cell systems for home use generate electricity by reforming city gas or LP gas and converting it into hydrogen. Although this system can reduce CO2 emissions by 50%, it cannot aim for zero. For this reason, pure hydrogen fuel cell systems that directly introduce pure hydrogen are also being developed for application in the future hydrogen society. As various efforts are being made to achieve carbon neutrality by 2050 not only in Japan but also on a global scale, it is believed that the price of hydrogen will fall and the world in which large-scale fuel cells are used for power generation will soon become common. It is also expected that fuel cells will become common in place of engines for moving objects such as automobiles, heavy machinery, ships, and trains. In preparation for this situation, hydrogen fuel cells are being developed by various organizations. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] JP 2011-204517 A Summary of the Invention [Problem to be solved by the invention]

[0005] Furthermore, for household use, a single fuel cell stack is generally used. However, for commercial use and future large-scale power generation, it is expected that multiple fuel cell stacks will be used in combination. This is because it is difficult to increase the cell area or the number of cells infinitely due to equipment constraints and sealing issues of the fuel cell stack. Furthermore, since users have various output needs, it is also necessary to standardize fuel cell stacks and reduce costs by adjusting the number of fuel cell stacks.

[0006] When multiple fuel cell stacks are used to create a system, the fuel cell stacks are electrically connected in series. This simplifies the system configuration and increases the voltage, which has the advantage of increasing inverter efficiency. However, the increased voltage level in series connections increases various risks. For example, if the DC voltage exceeds 750V, it is classified as high voltage under electrical equipment standards, and strict rules must be followed.

[0007] It is therefore difficult to electrically connect fuel cell stacks in series without limit. For this reason, it is conceivable to connect several fuel cell stacks connected in series in parallel. In this case, if a single power converter is used for control, the current (string current) flowing through each fuel cell will change so that the voltages of the fuel cells connected in parallel are perfectly matched. If the characteristics of all connected fuel cell stacks were the same, the voltage and current would also be the same, but in reality, the voltage and current characteristics change due to variations in the individual characteristics of the fuel cell stacks and their deterioration status, so there will inevitably be variations in the string current flowing through each fuel cell.

[0008] It is considered efficient to distribute equal amounts of process gases such as hydrogen and oxygen and cell cooling water to each cell stack individually, since individual control is not required. On the other hand, since the process gas consumption is completely proportional to the generated current, the current deviation of the string current will cause variation in gas consumption. However, even if variations in these current deviations occur, it is difficult to make the process gases such as hydrogen and oxygen and the cell cooling water follow the current deviation. This may affect the gas utilization rate and shorten the life of the fuel cell.

[0009] Therefore, an object of the present invention is to provide a fuel cell system, a control device, and a control method that are capable of adjusting the output current of each of a plurality of fuel cell groups each having several fuel cell stacks connected in series. [Means for solving the problem]

[0010] According to this embodiment, the fuel cell system includes a first fuel cell group, a first power converter, a second fuel cell group, a second power converter, and a first pipe. The first fuel cell group is configured by connecting a plurality of fuel cell stacks in series. The first power converter is capable of controlling a first generated power of the first fuel cell group in response to a first output current. The second fuel cell group is configured by connecting a plurality of fuel cell stacks in series, each corresponding to the plurality of fuel cell stacks. The second power converter is capable of controlling a second generated power of the second fuel cell group in response to a second output current. The first pipe supplies an oxygen-containing gas to each of the plurality of fuel cell stacks of the first fuel cell group and the plurality of fuel cell stacks of the second fuel cell group. Effect of the Invention

[0011] According to the present invention, the current deviation can be suppressed. [Brief description of the drawings]

[0012] [Figure 1] FIG. 1 is a block diagram showing an example of the configuration of a fuel cell system. [Diagram 2]FIG. 4 is a diagram showing an example of the configuration of a first fuel cell group and a second fuel cell group and a connection of a first pipe. [Diagram 3] FIG. 4 is a diagram showing an example of the configuration of a first fuel cell group and a second fuel cell group and a connection of a second pipe. [Figure 4] 4 is a diagram showing an example of the configuration of a first fuel cell group and a second fuel cell group, and a connection of a third pipe. FIG. [Diagram 5] FIG. 2 is a diagram showing a configuration and connection example of a power converter. [Figure 6] FIG. 2 is a diagram showing a schematic diagram of a power generation state of a fuel cell constituting a fuel cell stack. [Figure 7] FIG. 2 is a block diagram showing the configuration of a control device. [Figure 8] FIG. 4 is a diagram showing a control example of a current control unit. [Figure 9] FIG. 4 is a diagram showing a control example of a first flow rate control unit. [Figure 10] FIG. 4 is a diagram showing a control example of a second flow rate control unit. [Figure 11] FIG. 11 is a diagram showing a control example of a third flow rate control unit. [Figure 12] FIG. 4 is a diagram showing an example of a configuration in which a first fuel cell group and a second fuel cell group are connected in parallel. [Figure 13] FIG. 13 is a diagram showing an example of control of a parallel connection. [Figure 14] 4 is a flowchart showing an example of control processing of the control device. [Figure 15] FIG. 2 is a diagram showing an example in which a first power converter 1 and a second power converter are integrally configured. [Figure 16] FIG. 13 is a diagram showing an example further including a host control device that controls the control devices. [Figure 17] FIG. 13 is a diagram showing an example including a power conversion upper control unit. [Figure 18] FIG. 2 is a diagram showing an example in which the control device is configured with a first control device and a second control device. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0013] Hereinafter, a fuel cell system, a control device, and a control method according to an embodiment of the present invention will be described in detail with reference to the drawings. Note that the embodiment shown below is an example of an embodiment of the present invention, and the present invention is not limited to these embodiments. In addition, in the drawings referred to in this embodiment, the same parts or parts having similar functions are given the same or similar symbols, and repeated explanations thereof may be omitted. In addition, the dimensional ratios of the drawings may differ from the actual ratios for the convenience of explanation, and some of the configurations may be omitted from the drawings.

[0014] (One embodiment)

[0015] An example of the overall configuration of the fuel cell system 1 will be described with reference to Figures 1 to 4. Figure 1 is a block diagram showing an example of the configuration of the fuel cell system 1. Figure 2 is a diagram showing the configuration of the first fuel cell group 10a and the second fuel cell group 10b, and an example of the connection of the first pipe L14. Figure 3 is a diagram showing the configuration of the first fuel cell group 10a and the second fuel cell group 10b, and an example of the connection of the second pipe L16. Figure 4 is a diagram showing the configuration of the first fuel cell group 10a and the second fuel cell group 10b, and an example of the connection of the third pipe L18.

[0016] As shown in FIG. 1, the fuel cell system 1 includes a first fuel cell group 10a, a second fuel cell group 10b, a first power converter 12a, a second power converter 12b, a first supply device 14, a second supply device 16, a third supply device 18, a water tank 22, a control device 24, a first wiring E12a, a second wiring E12b, a first pipe L14, a second pipe L16, a third pipe L18, and a fourth pipe L20.

[0017] 2, the first fuel cell group 10a is configured by connecting a plurality of fuel cell stacks 100a in series. The fuel cell stacks 100a generate electricity using a hydrogen-containing gas that contains hydrogen and an oxygen-containing gas that contains oxygen.

[0018] The second fuel cell group 10b has the same configuration as the first fuel cell group 10a. That is, the second fuel cell group 10b is configured by connecting in series a plurality of fuel cell stacks 100b corresponding to the plurality of fuel cell stacks 100a in the first fuel cell group 10a. In this embodiment, the series connection of the plurality of fuel cell stacks 100a is called a string, and the current flowing through the plurality of fuel cell stacks 100a connected in series may be called a string current. The number of the plurality of fuel cell stacks 100a connected in series may be any number and is not limited to four. Furthermore, in the fuel cell system 1 according to this embodiment, two fuel cell groups, the first fuel cell group 10a and the second fuel cell group 10b, are described, but are not limited thereto. The fuel cell system 1 may be configured with two or more fuel cell groups, for example, the fuel cell system 1 may be configured with five fuel cell groups.

[0019] The first pipe L14 is an air pipe connecting the first supply device 14 to the plurality of fuel cell stacks 100a and the plurality of fuel cell stacks 100b. For example, the first pipe L14 supplies an oxygen-containing gas between the corresponding fuel cell stacks of the plurality of fuel cell stacks 100a of the first fuel cell group 10a and the plurality of fuel cell stacks 100b of the second fuel cell group 10b. For example, air is supplied to the first pipe L14 as the oxygen-containing gas. This allows the first pipe L14 to supply the oxygen-containing gas to the air electrodes (cathode electrodes) of the plurality of fuel cell stacks 100a and the plurality of fuel cell stacks 100b.

[0020] The first supply device 14 is, for example, an air blower, and is provided on the first pipe L14 upstream of the first fuel cell group 10a and the second fuel cell group 10b. The first supply device 14 supplies oxygen-containing gas from the upstream side of the air electrodes of the multiple fuel cell stacks 100a and the multiple fuel cell stacks 100b via the first pipe L14.

[0021] For example, the diameter of the pipe connecting the fuel cell stack 100a and the fuel cell stack 100b corresponding to the first pipe L14 is equal. In this embodiment, the diameter is equal to each other means that the same amount of oxygen-containing gas is supplied when oxygen-containing gas of the same pressure is supplied. Therefore, even if the diameter of the pipe is different, if the oxygen-containing gas is supplied in approximately the same amount by, for example, a valve in the pipe, the pipe diameter is said to be equivalent. In addition, approximately the same amount means that the absolute value of the difference in the supply amount of both in the pipe connecting the fuel cell stack 100a and the fuel cell stack 100b is within a few percent of the one with the smaller supply amount. For example, it preferably means within 1 percent. In this way, the first pipe L14 can supply an equivalent amount of oxygen-containing gas between the corresponding fuel cell stacks of the multiple fuel cell stacks 100a of the first fuel cell group 10a and the multiple fuel cell stacks 100b of the second fuel cell group 10b. In this embodiment, the diameter of the pipe connecting the fuel cell stack 100a and the fuel cell stack 100b corresponding to the first pipe L14 is described as being equal to each other, but is not limited to this. For example, the amount of oxygen-containing gas supplied from the pipe connecting the fuel cell stack 100a and the fuel cell stack 100b may be a predetermined ratio, such as 6:4. In this case, for example, the number of cell stacks 100a, 100b may be configured to be 6:4. In other words, it is possible to configure the total number of cell stacks to be 6:4.

[0022] 3, the second pipe L16 is a fuel gas supply pipe that connects the second supply device 16 to the plurality of fuel cell stacks 100a and the plurality of fuel cell stacks 100b. A hydrogen-containing gas is supplied to the second pipe L16 as a fuel gas. As a result, the second pipe L16 supplies the hydrogen-containing gas from the second supply device 16 to the fuel electrodes (anode electrodes) of the plurality of fuel cell stacks 100a and the plurality of fuel cell stacks 100b.

[0023] The second supply device 16 is, for example, a blower, and is provided on the upstream side of the first fuel cell group 10a and the second fuel cell group 10b of the second pipe L16. This second pipe L16 supplies hydrogen-containing gas from the upstream side of the fuel electrodes of the multiple fuel cell stacks 100a and the multiple fuel cell stacks 100b.

[0024] For example, the diameter of the pipe connecting the corresponding fuel cell stack 100a and the fuel cell stack 100b of the second pipe L16 is equal. In this way, the second pipe L16 supplies an equal amount of hydrogen-containing gas between the corresponding fuel cell stacks of the multiple fuel cell stacks 100a of the first fuel cell group 10a and the multiple fuel cell stacks 100b of the second fuel cell group 10b. In this embodiment, the diameter of the pipe connecting the corresponding fuel cell stack 100a and the fuel cell stack 100b of the second pipe L16 is described as being equal, but is not limited to this. For example, the amount of hydrogen-containing gas supplied from the pipe connecting the fuel cell stack 100a and the fuel cell stack 100b may be a predetermined ratio, such as 6:4. In this case, the supply ratio of the hydrogen-containing gas is made to correspond to the supply ratio of the oxygen gas.

[0025] 4, the third pipe L18 is a cooling water supply pipe that connects the third supply device 18 to the plurality of fuel cell stacks 100a and the plurality of fuel cell stacks 100b. Cooling water is supplied to the third pipe L18 as a cooling liquid. Thus, the third pipe L18 supplies the cooling water from the third supply device 18 to the plurality of fuel cell stacks 100a and the plurality of fuel cell stacks 100b.

[0026] For example, the diameter of the pipe connecting the corresponding fuel cell stack 100a and the fuel cell stack 100b of the third pipe L18 is equal. In this way, the third pipe L18 supplies an equal amount of cooling water between the corresponding fuel cell stacks of the multiple fuel cell stacks 100a of the first fuel cell group 10a and the multiple fuel cell stacks 100b of the second fuel cell group 10b. In this embodiment, the diameter of the pipe connecting the corresponding fuel cell stack 100a and the fuel cell stack 100b of the third pipe L18 is described as being equal, but is not limited to this. For example, the amount of cooling water supplied from the pipe connecting the fuel cell stack 100a and the fuel cell stack 100b may be a predetermined ratio, such as 6:4. In this case, the supply ratio of the cooling water is made to correspond to the supply ratio of the oxygen gas.

[0027] 1 again, the fourth pipe L20 is a cooling water discharge pipe that connects the water tank 22 to the plurality of fuel cell stacks 100a and the plurality of fuel cell stacks 100b. The water tank 22 collects the cooling water discharged from the plurality of fuel cell stacks 100a and the plurality of fuel cell stacks 100b, and cools it using a cooling device. In this way, the cooling water discharged from the plurality of fuel cell stacks 100a and the plurality of fuel cell stacks 100b is collected in the water tank 22 via the fourth pipe L20.

[0028] Fig. 5 is a diagram showing a schematic configuration and connection example of the power converters 12a, b. As shown in Fig. 5, the power converters 12a, b are, for example, converters, and are capable of controlling the power generated by the fuel cells 10a, b according to the output current. That is, the first power converter 12a and the second power converter 12b have the same configuration. In the following description, the first power converter 12a and the second power converter 12b may be simply referred to as the power converters 12a, b, etc.

[0029] The power converters 12a, b include, for example, a variable resistor 120, an ammeter 122, and a voltmeter 124. Wiring E12a, b connects both ends of the fuel cells 10a, b to both ends of the variable resistor 120. The ammeter 122 measures the output current flowing through the wiring E12a, b. The voltmeter 124 measures the voltage across the variable resistor 120.

[0030] The power converters 12a, b change the resistance of the variable resistor 120 in response to an output command from the control device 24 so that the value of the ammeter 122 becomes a target value. The power converters 12a, b also supply the value of the ammeter 122 and the value of the voltmeter 124 to the control device 24. The output current of the fuel cell 10 increases as the resistance of the variable resistor 120 decreases. At this time, the voltage value of the fuel cells 10a, b varies according to the output current flowing through the fuel cells 10a, b. For example, the voltage value of the fuel cells 10a, b increases as the output current flowing through the fuel cells 10a, b increases. In other words, the output power of the fuel cells 10a, b is controlled by the resistance value of the variable resistor 120. The power converters 12a, b are not limited to the configuration of FIG. 5, and other configurations may be used.

[0031] 6 is a diagram showing a schematic diagram of a power generation state of a fuel cell constituting a fuel cell stack. The fuel cell stack is formed by stacking, for example, a plurality of unit cells 102. Note that the fuel cell stack according to this embodiment is, for example, a PEFC (polymer electrolyte fuel cell), but is not limited thereto.

[0032] This unit cell 102 has a membrane electrode composite. The membrane electrode composite has an electrolyte membrane 104, a fuel electrode (anode electrode) 106 arranged on one surface of the electrolyte membrane 104, and an air electrode (cathode electrode) 108 arranged on the surface of the electrolyte membrane 104 opposite to the fuel electrode 106. Furthermore, the fuel electrode 106 has an anode catalyst layer, and the air electrode 108 has a cathode catalyst layer.

[0033] This unit cell 102 generates power through the reaction shown in Chemical Formula 1. Hydrogen-containing gas flows through the fuel electrode flow passage on the fuel electrode 106 side, causing a fuel electrode reaction. Oxygen-containing gas flows through the oxidizer electrode flow passage on the air electrode 108 side, causing an oxidizer electrode reaction. The fuel cell stacks 100a,b use these electrochemical reactions to extract electrical energy from the electrodes. As can be seen from this, there is a direct proportional relationship between the output current generated by power generation in the unit cell 102 and the amount of oxygen-containing gas used for power generation. Similarly, there is a direct proportional relationship between the current generated by power generation in the unit cell 102 and the amount of hydrogen-containing gas used for power generation.

[0034] (chemical formula 1) Fuel electrode reaction: 2H2→4H + +4e - Air electrode reaction: 4H + +4e - +O2→2H2O

[0035] FIG. 7 is a block diagram showing the configuration of the control device 24. As shown in FIG. 7, the control device 24 controls the entire fuel cell system 1. The control device 24 is, for example, a microcomputer equipped with a CPU (Central Processing Unit), a storage device 240, an acquisition device (input / output interface) 242, and the like. The control device 24 performs control according to a program stored in the storage device 240. That is, the control device 24 configures a power calculation unit 244, a current control unit 246, a first flow rate control unit 248, a second flow rate control unit 250, and a third flow rate control unit 252 according to the program stored in the storage device 240. Note that the power calculation unit 244, the current control unit 246, the first flow rate control unit 248, the second flow rate control unit 250, and the third flow rate control unit 252 may be configured as electronic circuits.

[0036] The acquisition device 242 acquires various types of information about the fuel cell system 1. For example, the acquisition device 242 acquires information about current values, voltage values, and power from the first power converter 12a and the second power converter 12b.

[0037] The power calculation unit 244 calculates the output power of the first fuel cell group 10a and the second fuel cell group 10b using the current values ​​and voltage values ​​acquired from the first power converter 12a and the second power converter 12b. Note that when the first power converter 12a and the second power converter 12b each calculate power, it is possible to omit the power calculation in the power calculation unit 244 by using the power calculated by the first power converter 12a and the second power converter 12b.

[0038] FIG. 8 is a diagram showing an example of control by the current control unit 246. The horizontal axis indicates the current value of each of the first fuel cell group 10a and the second fuel cell group 10b, and the vertical axis indicates the voltage value of each of the first fuel cell group 10a and the second fuel cell group 10b. Line S12a indicates the voltage and current characteristics of the first fuel cell group 10a, and line S12b indicates the voltage and current characteristics of the second fuel cell group 10b. Moreover, a rectangle Sqa indicates the generated power of the first fuel cell group 10a, and a rectangle Sqb indicates the generated power of the second fuel cell group 10b. Moreover, a first output voltage and a first output current indicate the output voltage and output current of the first fuel cell group 10a, respectively, and a second output voltage and a second output current indicate the output voltage and output current of the second fuel cell group 10b, respectively.

[0039] 8, the current control unit 246 uses the information acquired by the acquisition device 242 to control the first output current generated by the first fuel cell group 10a and the second output current generated by the second fuel cell group 10b to be predetermined values. For example, the current control unit 246 according to this embodiment controls the first power converter 12a and the second power converter 12b so that the first output current generated by the first fuel cell group 10a and the second output current generated by the second fuel cell group 10b are equal. This makes the amounts of oxygen-containing gas used for power generation by the first fuel cell group 10a and the second fuel cell group 10b equal.

[0040] When the amount of oxygen-containing gas supplied from the first pipe L14 connecting the fuel cell stack 100a and the fuel cell stack 100b is a predetermined ratio, such as 6:4, the current control unit 246 may control the ratio between the first output current and the second output current to correspond to the supply ratio, thereby making it possible to supply the oxygen-containing gas to the first fuel cell group 10a and the second fuel cell group 10b without excess or deficiency.

[0041] As can be seen from this, even if the diameter of the piping connecting the corresponding fuel cell stacks 100a and 100b of the first piping L14 is configured to be equal, the first flow rate control unit 248 can cause the first supply device 14 to supply the exact amount of oxygen-containing gas required to generate the current values ​​generated in the first fuel cell group 10a and the second fuel cell group 10b.

[0042] In this way, the current control unit 246 according to this embodiment controls the first output current and the second output current to be equal to each other, while increasing the first output current and the second output current, and controls the first power converter 12a and the second power converter 12b to reach the target power value. Furthermore, when the fuel cell system 1 starts to operate, the current control unit 246 controls the first power converter 12a and the second power converter 12b to increase the first output current and the second output current from 0 to reach the target power value. This makes it possible to suppress the power consumption of the first supply device 14, the second supply device 16, and the third supply device 18 during adjustment control.

[0043] Fig. 9 is a diagram showing an example of control by the first flow rate control unit 248. The horizontal axis indicates the current values ​​of the first fuel cell group 10a and the second fuel cell group 10b, and the vertical axis indicates the supply amount of oxygen-containing gas from the first supply device 14. As shown in Fig. 9, the first flow rate control unit 248 causes the first supply device 14 to supply an amount of oxygen-containing gas proportional to the current values ​​of the first fuel cell group 10a and the second fuel cell group 10b. In other words, the first flow rate control unit 248 causes the first supply device 14 to supply just the right amount of oxygen-containing gas required when generating output current for the first fuel cell group 10a and the second fuel cell group 10b.

[0044] As described above, the first pipe L14 is configured to supply an equal amount of oxygen-containing gas between the fuel cell stacks 100a of the first fuel cell group 10a and the fuel cell stacks 100b of the second fuel cell group 10b. Therefore, the first supply device 14 can supply the oxygen-containing gas to the first fuel cell group 10a and the second fuel cell group 10b without excess or deficiency by supplying the oxygen-containing gas according to the generated currents of the first fuel cell group 10a and the second fuel cell group 10b. In other words, when the control is performed to make the first output current and the second output current equal, the oxygen-containing gas can be supplied evenly to the first fuel cell group 10a and the second fuel cell group 10b without excess or deficiency by supplying the oxygen-containing gas through the first pipe L14, and the power consumption of the first supply device 14 can be suppressed. In this way, by controlling the first output current and the second output current to be equal, the control of the first supply device 14 is simplified and the power consumption of the first supply device 14 can be controlled according to the value of one of the output currents generated by the first fuel cell group 10a and the second fuel cell group 10b, thereby making it possible to control the power consumption of the fuel cell system 1 with higher precision.

[0045] When the amount of oxygen-containing gas supplied from the first pipe L14 connecting the fuel cell stack 100a and the fuel cell stack 100b is a predetermined ratio, such as 6:4, the first flow rate control unit 248 may control the ratio between the first output current and the second output current to correspond to the supply ratio. This allows the first fuel cell group 10a and the second fuel cell group 10b to be supplied with the oxygen-containing gas without excess or deficiency, and makes it possible to reduce the power consumption of the first supply device 14.

[0046] Fig. 10 is a diagram showing an example of control by the second flow rate control unit 250. The horizontal axis indicates the current values ​​of the first fuel cell group 10a and the second fuel cell group 10b, and the vertical axis indicates the supply amount of hydrogen-containing gas from the second supply device 16. As shown in Fig. 10, the second flow rate control unit 250 causes the second supply device 16 to supply an amount of hydrogen-containing gas proportional to the current values ​​of the first fuel cell group 10a and the second fuel cell group 10b. In other words, the second flow rate control unit 250 causes the second supply device 16 to supply just the right amount of hydrogen-containing gas required when generating the output current of the first fuel cell group 10a and the second fuel cell group 10b.

[0047] As described above, the second pipe L16 is configured to supply an equal amount of hydrogen-containing gas between the fuel cell stacks 100a of the first fuel cell group 10a and the fuel cell stacks 100b of the second fuel cell group 10b. Therefore, the second supply device 16 can supply the hydrogen-containing gas to the first fuel cell group 10a and the second fuel cell group 10b without excess or deficiency by supplying the hydrogen-containing gas according to the generated current of the first fuel cell group 10a and the second fuel cell group 10b. In other words, when the control is performed to make the first output current and the second output current equal, the hydrogen-containing gas can be supplied evenly to the first fuel cell group 10a and the second fuel cell group 10b without excess or deficiency by supplying the hydrogen-containing gas through the second pipe L16, and the power consumption of the second supply device 16 can be suppressed. In this way, by controlling the first output current and the second output current to be equal, the control of the second supply device 16 is simplified and the power consumption of the second supply device 16 can be controlled in accordance with the value of one of the output currents of the first fuel cell group 10a and the second fuel cell group 10b, thereby making it possible to control the power consumption of the fuel cell system 1 with higher precision.

[0048] When the amount of hydrogen-containing gas supplied from the second pipe L16 connecting the fuel cell stack 100a and the fuel cell stack 100b is a predetermined ratio, such as 6:4, the second flow rate control unit 250 may control the ratio between the first output current and the second output current to correspond to the supply ratio. This allows the first fuel cell group 10a and the second fuel cell group 10b to be supplied with the hydrogen-containing gas without excess or deficiency, and makes it possible to reduce the power consumption of the second supply device 16.

[0049] FIG. 11 is a diagram showing an example of control by the third flow rate control unit 252. The horizontal axis indicates the current value of each of the first fuel cell group 10a and the second fuel cell group 10b, and the vertical axis indicates the supply amount of cooling water of the third supply device 18. As shown in FIG. 11, the third flow rate control unit 252 causes the third supply device 18 to supply an amount of cooling water according to the current value of each of the first fuel cell group 10a and the second fuel cell group 10b. That is, the second flow rate control unit 250 causes the second flow rate control unit 250 to supply the amount of cooling water necessary when generating the output current generated by the first fuel cell group 10a and the second fuel cell group 10b without excess or deficiency. This makes it possible to maintain the first fuel cell group 10a and the second fuel cell group 10b at a predetermined temperature.

[0050] As described above, the third pipe L18 is configured to supply an equal amount of cooling water between the fuel cell stacks 100a of the first fuel cell group 10a and the fuel cell stacks 100b of the second fuel cell group 10b. Therefore, the third supply device 18 supplies cooling water according to the generated currents of the first fuel cell group 10a and the second fuel cell group 10b, so that the first fuel cell group 10a and the second fuel cell group 10b can be supplied with cooling water without excess or deficiency to maintain a predetermined temperature. In other words, when performing control to make the first output current and the second output current equal, the cooling water can be evenly supplied to the first fuel cell group 10a and the second fuel cell group 10b without excess or deficiency by supplying cooling water through the third pipe L18, and the power consumption of the third supply device 18 can be reduced.

[0051] If the amount of cooling water supplied from the third pipe L18 connecting the fuel cell stack 100a and the fuel cell stack 100b is a predetermined ratio, such as 6:4, the third flow rate control unit 252 may control the ratio between the first output current and the second output current to correspond to the supply ratio. This allows the first fuel cell group 10a and the second fuel cell group 10b to be supplied with just the right amount of cooling water, thereby reducing the power consumption of the third supply device 18.

[0052] Here, a control example of parallel connection will be described as a comparative example with reference to Figs. 12 and 13. Fig. 12 is a diagram showing a configuration example in which the first fuel cell group 10a and the second fuel cell group 10b are connected in parallel. Fig. 13 is a diagram showing a control example of parallel connection. The horizontal axis shows the current value of each of the first fuel cell group 10a and the second fuel cell group 10b, and the vertical axis shows the voltage value of each of the first fuel cell group 10a and the second fuel cell group 10b. Line S12a shows the voltage and current characteristics of the first fuel cell group 10a, and line S12b shows the voltage and current characteristics of the second fuel cell group 10b. Moreover, a rectangle Sqa shows the generated power of the first fuel cell group 10a, and a rectangle Sqb shows the generated power of the second fuel cell group 10b. Moreover, the first output current shows the output current of the first fuel cell group 10a, and the second output current shows the output current of the second fuel cell group 10b.

[0053] 12, when the first fuel cell group 10a and the second fuel cell group 10b are connected in parallel, the voltage of the first fuel cell group 10a (voltages 1+2+3+4) and the voltage of the second fuel cell group 10b (voltages 5+6+7+8) become the same. Therefore, the generated power is controlled by the generated voltages of the first fuel cell group 10a and the second fuel cell group 10b, which is different from the control example shown in FIG.

[0054] 13, in the comparative example, the first output current of the first power converter 12a and the second output current of the second power converter 12b differ from each other, which results in a difference in the consumption of the oxygen-containing gas and the hydrogen-containing gas between the first fuel cell group 10a and the second fuel cell group 10b.

[0055] As described above, the first pipe L14 is configured to supply an equal amount of oxygen-containing gas between the fuel cell stacks 100a of the first fuel cell group 10a and the fuel cell stacks 100b of the second fuel cell group 10b. Therefore, if the supply amount of oxygen-containing gas from the first supply device 14 is not controlled according to the larger current value of the current 1 and the current 2, the fuel cell having the larger current value will deteriorate due to a lack of oxygen content. On the other hand, if the supply amount of oxygen-containing gas from the first supply device 14 is controlled according to the larger current value of the first output current and the second output current, an excessive amount of oxygen-containing gas will be supplied to the fuel cell having the smaller current value of the current 1 and the current 2. In other words, the power consumption of the first supply device 14 will be used redundantly.

[0056] Similarly, if the supply amounts of hydrogen-containing gas and cooling water from the second supply device 16 and the third supply device 18 are not controlled, the fuel cell with the larger current value will deteriorate or become too hot due to a shortage of hydrogen-containing gas and cooling water. On the other hand, if the supply amount of oxygen-containing gas from the first supply device 14 is controlled in accordance with the larger current value of the first output current or the second output current, excessive hydrogen-containing gas and cooling water will be supplied to the fuel cell with the smaller current value of the first output current or the second output current. In other words, the power consumption of the second supply device 16 and the third supply device 18 will be used redundantly.

[0057] In response to this, as described above, the current control unit 246 according to this embodiment controls the first output current and the second output current to control the generated power (see FIG. 8). In particular, it is possible to control the first power converter 12a and the second power converter 12b so that the first output current and the second output current are equal to each other and match the power value as the output command. In this case, it is possible to make the generated power match the power value as the power command while uniformly supplying the oxygen-containing gas, the hydrogen-containing gas, and the cooling water to the first fuel cell group 10a and the second fuel cell group 10b without excess or deficiency. As can be seen from this, the control by the current control unit 246 according to this embodiment suppresses redundant use of the power consumed by the first supply device 14, the second supply device 16, and the third supply device 18.

[0058] 14 is a flowchart showing an example of control processing by the control device 24. Here, an example of control after a command power value is set as a power command will be described.

[0059] First, the acquisition device 242 acquires information related to current values, voltage values, and power from the first power converter 12a and the second power converter 12b (step S100). Next, the power calculation unit 244 calculates the output power of the first fuel cell group 10a and the second fuel cell group 10b using the current values ​​and voltage values ​​acquired from the first power converter 12a and the second power converter 12b (step S101).

[0060] Next, the current control unit 246 uses the information acquired by the acquisition device 242 to determine whether the first output current generated by the first fuel cell group 10a and the second output current generated by the second fuel cell group 10b are equal (step S102). If it is determined that the currents do not match (NO in step S102), the current control unit 246 controls the first power converter 12a and the second power converter 12b so that the currents match (step S104), and repeats the process from step S100. Here, the range of match is a difference of several percent. For example, it is preferably a difference of 1 percent.

[0061] On the other hand, when it is determined that the currents match (YES in step S102), the current control unit 246 determines whether the power calculated by the power calculation unit 244 is equal to or less than the command power value (step S106).

[0062] In this case, when the power calculation unit 244 determines that the calculated power is lower than the command power value (YES in step S106), the current control unit 246 controls the first power converter 12a and the second power converter 12b to increase the current values ​​while making them equal (step S108). On the other hand, when the power calculation unit 244 determines that the calculated power is higher than the command power value (NO in step S106), the current control unit 246 controls the first power converter 12a and the second power converter 12b to decrease the current values ​​while making them equal (step S108). Then, the current control unit 246 determines whether or not to end the entire process (step S112). If not to end (NO in step S112), the process from step S100 is repeated, and if to end (YES in step S112), the entire process is ended.

[0063] In this way, when the total power of the first fuel cell group 10a and the second fuel cell group 10b is lower than the command power value, the current control unit 246 gradually increases the two currents while matching them until the command power value is reached. On the other hand, when the total power is higher than the command power value, the current control unit 246 gradually decreases the two currents while matching them until the command power value is reached. Then, even when the total power indicates a constant value, the control for matching the current values ​​is continued. This makes it possible to perform control for increasing or decreasing the two currents while matching them so that they match the command power value, even if the total power deviates from the command power value due to disturbances or changes in the characteristics of the individual fuel cells.

[0064] 15 is a diagram showing an example in which the first power converter 12a and the second power converter 12b are integrated into a power converter 125. For example, in the power converter 125, the first power converter 12a and the second power converter 12b share an arithmetic circuit 122 and the like. This allows the second power converter 12b and the power converter 120 to be made smaller in size.

[0065] 16 is a diagram showing an example further including a host control device 26 that controls the control device 24. This allows the host control device 26 to control the control device 24 in accordance with other controls of the fuel cell system 1, for example.

[0066] 17 is a diagram showing an example in which a power conversion upper control unit 28 is provided that is shared by the first power converter 12a and the second power converter 12b. The power conversion upper control unit 28 shares a control circuit with the first power converter 12a and the second power converter 12b. This makes it possible to further reduce the size of the first power converter 12a and the second power converter 12b.

[0067] 18 is a diagram showing an example in which the control device 24 is configured with a first control device 24a and a second control device 24b. The first control device 24a controls the first power converter 12a and the second power converter 12b in accordance with the control of the upper control device 26. Meanwhile, the second control device 24b controls the first supply device 14, the second supply device 16, and the third supply device 18 in accordance with the control of the upper control device 26. This makes it possible to control the power converters 12a and 12b and the first supply device 14, the second supply device 16, and the third supply device 18 independently. In addition, by controlling the second power converter 12b via the first power converter 12a, wiring and the like can be further simplified.

[0068] As described above, according to this embodiment, the first power converter 12a controls the first generated power of the first fuel cell group 10a according to the first output current, and the second power converter 12b controls the second generated power of the second fuel cell group 10b according to the second output current. This makes it possible to match the supply amounts of oxygen-containing gas, hydrogen-containing gas, and cooling water supplied to the first fuel cell group 10a and the supply amounts of oxygen-containing gas, hydrogen-containing gas, and cooling water supplied to the second fuel cell group 10b with the supply amounts of the first pipe L14, the second pipe L16, and the third pipe L18, respectively. Therefore, even if the pipe diameters of the first pipe L14, the second pipe L16, and the third pipe L18 are fixed, it is possible to supply the oxygen-containing gas, hydrogen-containing gas, and cooling water to the first fuel cell group 10a and the second fuel cell group 10b without excess or deficiency, respectively, and the power consumption of the first supply device 14, the second supply device 16, and the third supply device 18 can be suppressed.

[0069] In particular, in the first pipe L14, the second pipe L16, and the third pipe L18, even when the pipe diameters between corresponding fuel cell stacks of the multiple fuel cell stacks 100a of the first fuel cell group 10a and the multiple fuel cell stacks 100b of the second fuel cell group 10b are equivalent, by controlling the first output current and the second output current to be equal, it is possible to supply oxygen-containing gas, hydrogen-containing gas, and cooling water to each of the first fuel cell group 10a and the second fuel cell group 10b without excess or deficiency.

[0070] Although several embodiments of the present invention have been described above, these embodiments are presented as examples and are not intended to limit the scope of the invention. These novel embodiments can be implemented in various other forms, and various omissions, substitutions, and modifications can be made without departing from the spirit of the invention. These embodiments and their modifications are included in the scope and spirit of the invention, and are included in the invention and its equivalents described in the claims. [Explanation of symbols]

[0071] 1: fuel cell system, 10a: first fuel cell group, 10b: second fuel cell group, 12a: first power converter, 12b: second power converter, 14: first supply device, 16: second supply device, 18: third supply device, 24: control device, 24a: first control device, 24b: second control device, 26: upper control device (third control device), 100a: fuel cell stack, 100b: fuel cell stack, L14: first piping, L16: second piping, L18: third piping.

Claims

1. a first fuel cell group including a plurality of fuel cell stacks connected in series; a first power converter capable of controlling a first generated power of the first fuel cell group in accordance with a first output current; a second fuel cell group including a plurality of fuel cell stacks connected in series, the second fuel cell stacks corresponding to the plurality of fuel cell stacks; a second power converter capable of controlling a second generated power of the second fuel cell group in accordance with a second output current; a first pipe for supplying an oxygen-containing gas between the plurality of fuel cell stacks of the first fuel cell group and the plurality of fuel cell stacks of the second fuel cell group, a first pipe that sets a predetermined ratio between an amount of oxygen-containing gas supplied to each of the fuel cells in the first fuel cell group and an amount of oxygen-containing gas supplied to each of the fuel cells in the second fuel cell group; a control device that controls the first power converter and the second power converter so that the first output current and the second output current are in the predetermined ratio; A fuel cell system comprising:

2. 2. The fuel cell system according to claim 1, wherein the control device controls the first power converter and the second power converter to match a predetermined power value while controlling the first output current and the second output current to correspond to the oxygen-containing gas supplied.

3. 2. The fuel cell system according to claim 1, wherein the control device increases the first output current and the second output current in an initial drive and controls the first power converter and the second power converter so that the first output current and the second output current reach a predetermined power value.

4. When the first piping supplies an equal amount of oxygen-containing gas between the plurality of fuel cell stacks of the first fuel cell group and the plurality of fuel cell stacks of the second fuel cell group, 2. The fuel cell system according to claim 1, wherein the control device controls the first output current and the second output current to be equal to each other.

5. a first fuel cell group including a plurality of fuel cell stacks connected in series; a first power converter capable of controlling a first generated power of the first fuel cell group in accordance with a first output current; a second fuel cell group including a plurality of fuel cell stacks connected in series, the second fuel cell stacks corresponding to the plurality of fuel cell stacks; a second power converter capable of controlling a second generated power of the second fuel cell group in accordance with a second output current; a second pipe for supplying a hydrogen-containing gas between the plurality of fuel cell stacks of the first fuel cell group and the plurality of fuel cell stacks of the second fuel cell group, a second pipe for setting a predetermined ratio between an amount of hydrogen-containing gas supplied to each of the fuel cells in the first fuel cell group and an amount of hydrogen-containing gas supplied to each of the fuel cells in the second fuel cell group; a control device that controls the first power converter and the second power converter so that the first output current and the second output current are in the predetermined ratio; A fuel cell system comprising:

6. 6. The fuel cell system according to claim 5, further comprising a third pipe for supplying a predetermined amount of cooling water between the corresponding fuel cell stacks of the first fuel cell group and the corresponding fuel cell stacks of the second fuel cell group.

7. When the second piping has an equal piping diameter between the corresponding fuel cell stacks of the first fuel cell group and the corresponding fuel cell stacks of the second fuel cell group, 6. The fuel cell system according to claim 5, wherein the control device controls the first output current and the second output current to be equal to each other.

8. The oxygen-containing gas supplying device further includes a first supply device that supplies the oxygen-containing gas to the first pipe, 2. The fuel cell system according to claim 1, wherein the first supply device controls the supply amount of the oxygen-containing gas in response to at least one of the first output current and the second output current.

9. A second pipe for supplying a hydrogen-containing gas between the plurality of fuel cell stacks of the first fuel cell group and the plurality of fuel cell stacks of the second fuel cell group, A second supply device that supplies the hydrogen-containing gas to be supplied to the second pipe, 9. The fuel cell system according to claim 8, wherein the second supply device controls the supply amount of the hydrogen-containing gas in response to at least one of the first output current and the second output current.

10. A third pipe for supplying a predetermined amount of cooling water between each of the plurality of fuel cell stacks of the first fuel cell group and each of the plurality of fuel cell stacks of the second fuel cell group. A third supply device that supplies the cooling water to be supplied to the third piping, 10. The fuel cell system according to claim 9, wherein the third supply device controls an amount of the cooling water supplied in accordance with at least one of the first output current and the second output current.

11. The fuel cell system according to claim 10 , wherein the control device further controls at least one of the first supply device, the second supply device, and the third supply device.

12. The control device includes: a first control device that controls the first power converter and the second power converter; a second control device that controls at least one of the first supply device, the second supply device, and the third supply device; The fuel cell system according to claim 11 , further comprising a third control device that controls the control device.

13. a first fuel cell group including a plurality of fuel cell stacks connected in series; a second fuel cell group including a plurality of fuel cell stacks connected in series, the second fuel cell stacks corresponding to the plurality of fuel cell stacks; a first power converter capable of controlling a first generated power of the first fuel cell group in accordance with a first output current; a second power converter capable of controlling a second generated power of the second fuel cell group in accordance with a second output current; a first pipe for supplying an oxygen-containing gas to each of a plurality of fuel cell stacks of the first fuel cell group and a plurality of fuel cell stacks of the second fuel cell group, the first pipe setting a predetermined ratio between an amount of the oxygen-containing gas supplied to each of the fuel cells of the first fuel cell group and an amount of the oxygen-containing gas supplied to each of the fuel cells of the second fuel cell group, a control device that controls the first power converter and the second power converter so that the first output current and the second output current are in the predetermined ratio, respectively.

14. a first fuel cell group including a plurality of fuel cell stacks connected in series; a second fuel cell group including a plurality of fuel cell stacks connected in series, the second fuel cell stacks corresponding to the plurality of fuel cell stacks; a first power converter capable of controlling a first generated power of the first fuel cell group in accordance with a first output current; a second power converter capable of controlling a second generated power of the second fuel cell group in accordance with a second output current; a first pipe for supplying an oxygen-containing gas to each of the plurality of fuel cell stacks of the first fuel cell group and each of the plurality of fuel cell stacks of the second fuel cell group, wherein an amount of the oxygen-containing gas supplied to each of the fuel cells of the first fuel cell group and an amount of the oxygen-containing gas supplied to each of the fuel cells of the second fuel cell group are set to a predetermined ratio; A method for controlling a fuel cell system, comprising: A control method comprising: controlling the first power converter and the second power converter such that the first output current and the second output current are in the predetermined ratio.

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