Fuel cell system

Abstract

To suppress the degradation of multiple fuel cells and batteries, and to suppress the decrease in the durability of the fuel cell system, in a fuel cell system without a DC-DC converter. [Solution] The fuel cell system 1 comprises three FC stacks 11A to 11C connected in parallel, a single battery 12 to which all three FC stacks 11A to 11C are connected, and a control device 20, but does not include a DC-DC converter. The control device 20 is configured to simultaneously measure the FC current of the three FC stacks 11A to 11C. The control device 20 controls the power generation of the three FC stacks 11A to 11C based on the differences in the FC currents measured simultaneously.

Description

Technical Field

[0001] The technology disclosed in this specification relates to a fuel cell system including a fuel cell and a battery that charges the electric power generated by the fuel cell.

Background Art

[0002] Conventionally, for example, a "power generation device" described in Patent Document 1 below is known. This device includes a plurality of fuel cells connected in parallel, one secondary battery (battery) to which all of the plurality of fuel cells are connected, a load, and a control device, and is configured as a device without a DCDC converter. The control device controls the startup and stop of the plurality of fuel cells and the battery in consideration of the startup time of the load and the fuel cells.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] Although the power generation device described in Patent Document 1 can simplify the configuration because it is configured as a device without a DCDC converter, there may be a difference in the degree of deterioration between the plurality of fuel cells. Here, if the plurality of fuel cells are operated without considering the difference in deterioration, the durability of the fuel cell with a large deterioration will decrease rapidly, and the durability of the power generation device may decrease.

[0005] This disclosed technology has been made in view of the above circumstances, and its object is to suppress the deterioration of a plurality of fuel cells and suppress the decrease in durability of the fuel cell system in a fuel cell system including a plurality of fuel cells and a battery and without a DCDC converter.

Means for Solving the Problems

[0006] To achieve the above objective, the technology described in claim 1 provides a fuel cell system comprising a plurality of fuel cells connected in parallel and a single battery to which all of the plurality of fuel cells are connected, and which does not include a DC-DC converter, further comprising a control device for controlling the power generation of the plurality of fuel cells, wherein the control device is configured to simultaneously measure the current of the plurality of fuel cells and controls the power generation of the plurality of fuel cells based on the difference in the measured current values ​​of each fuel cell measured simultaneously.

[0007] According to the configuration of the above technology, the control device simultaneously measures the current of multiple fuel cells and controls the power generation of the multiple fuel cells based on the difference in the current measurements of each fuel cell measured simultaneously. Therefore, it becomes possible to use fuel cells with high current measurements and less degradation for power generation, and to refrain from using fuel cells with low current measurements and a risk of degradation for power generation.

[0008] To achieve the above objective, the technology described in claim 2 is intended to be the technology described in claim 1, wherein the control device learns the current measurement values ​​measured simultaneously, prioritizes generating power from fuel cells with higher current measurement values ​​among the learned multiple current measurement values, and changes the number of fuel cells to generate power according to the required output of the fuel cell system.

[0009] According to the configuration of the above technology, in addition to the operation of the technology described in claim 1, the control device prioritizes generating power from fuel cells with high current measurement values ​​among the multiple learned current measurement values, and changes the number of fuel cells to generate power according to the required output of the fuel cell system. Therefore, it becomes possible to generate power in accordance with the required output while refraining from using fuel cells with low current measurement values ​​that may be degraded for power generation.

[0010] To achieve the above objective, the technology described in claim 3 is the technology described in claim 2, wherein the outputs of multiple fuel cells are set to be the same, the maximum required output of the fuel cell system is satisfied by the power generation of N fuel cells, the total number of fuel cells is set to N+1 or more, and the control device uses the N fuel cells corresponding to the highest current measurements among the multiple current measurements learned to generate power.

[0011] According to the configuration of the above technology, in addition to the operation of the technology described in claim 2, the control device uses N fuel cells corresponding to the highest current measurements out of the (N+1) learned current measurements for power generation, so that one fuel cell not used for power generation can be kept as a spare.

[0012] To achieve the above objective, the technology described in claim 4 further comprises an alarm device for notifying of fuel cell deterioration in the technology described in claim 1, wherein the control device activates the alarm device to warn that there is a risk of deterioration in the fuel cell if the measured current of the fuel cell is lower than a first current determination value, and activates the alarm device to notify of an abnormality in the fuel cell if the measured current of the fuel cell is lower than a second current determination value which is lower than the first current measurement value, indicating that there is a deterioration abnormality in the fuel cell.

[0013] According to the configuration of the above technology, in addition to the operation of the technology described in claim 1, the control device activates the alarm device to issue a warning when the current measurement value of the fuel cell is lower than the first current determination value, so that the user is notified early that there is a risk of deterioration in the fuel cell. Furthermore, the control device activates the alarm device to issue an abnormality notification when the current measurement value of the fuel cell is lower than the second current determination value, so that the user is notified early that there is a deterioration abnormality in the fuel cell.

[0014] To achieve the above objective, the technology described in claim 5 is the technology described in claim 4, wherein the control device is configured to measure the battery voltage, and the first determination current value and the second current determination value are changed according to the measured voltage.

[0015] According to the configuration of the above technology, in addition to the operation of the technology described in claim 4, the control device changes the first determination current value and the second current determination value for determining the risk of deterioration or deterioration abnormality of the fuel cell according to the measured voltage of the battery. [Effects of the Invention]

[0016] According to the technology described in claim 1, the degradation of each of the multiple fuel cells can be suppressed, and the decrease in the durability of the fuel cell system can be suppressed.

[0017] According to the technology described in claim 2, in addition to the effects of the technology described in claim 1, it is possible to meet the required output while suppressing the widening of the degradation difference among multiple fuel cells.

[0018] According to the technology described in claim 3, in addition to the effects of the technology described in claim 2, the lifespan of the fuel cell system can be extended.

[0019] According to the technology described in claim 4, in addition to the effects of the technology described in claim 1, the user can recognize the risk of deterioration or deterioration abnormalities in each of the multiple fuel cells at an early stage and take early action.

[0020] According to the technology described in claim 5, in addition to the effects of the technology described in claim 4, the degradation of the fuel cell can be accurately determined regardless of differences in the battery voltage state. [Brief explanation of the drawing]

[0021] [Figure 1] A schematic diagram showing a fuel cell system according to the first embodiment. [Figure 2] A schematic diagram showing the related configuration of the first FC stack according to the first embodiment. [Figure 3] A graph showing an example of the relationship between (A) FC current and FC voltage and (B) battery current and battery voltage in the case of no power consumption by the motor, relating to the first embodiment. [Figure 4]Graph showing an example of the relationship between the FC current and FC voltage of each FC stack with a difference in the degree of (A) deterioration when there is no power consumption of the motor, and the relationship between (B) the battery current and battery voltage according to the first embodiment. [Figure 5] Flowchart showing an example of the content of power generation control of three FC stacks according to the first embodiment. [Figure 6] Determination value map defining the warning determination value and abnormal determination value of the FC current with respect to the battery voltage according to the first embodiment. [Figure 7] Flowchart showing an example of the content of power generation control of three FC stacks according to the second embodiment.

Mode for Carrying Out the Invention

[0022] <First Embodiment> Hereinafter, a first embodiment in which a fuel cell system is embodied as a fuel cell system mounted on an electric vehicle will be described in detail with reference to the drawings.

[0023] [Regarding the Configuration of the Fuel Cell System] FIG. 1 schematically shows a fuel cell system 1 according to this embodiment in a configuration diagram. As shown in FIG. 1, the fuel cell system 1 of this embodiment is configured as a simple DCDC converterless system without a DCDC converter. This fuel cell system 1 includes three FC stacks, namely a first FC stack 11A, a second FC stack 11B, and a third FC stack 11C, one battery 12, and one motor 13. An inverter can also be provided instead of the motor 13.

[0024] Each of the FC stacks 11A to 11C has the same power generation output of "2 kW". Each of the FC stacks 11A to 11C and the motor 13 are connected in parallel to the battery 12. One diode 14A, 14B, 14C is connected in series to each of the FC stacks 11A to 11C. Each of the FC stacks 11A to 11C corresponds to an example of the "fuel cell" of this disclosed technology.

[0025] Here, a DC-DC converter is a device that converts DC (direct current) to DC (direct current), and is designed to convert the voltage used in the system to DC.

[0026] [Regarding the configuration of the FC stack] Figure 2 shows a schematic diagram of the configuration of the first FC stack 11A. As shown in Figure 2, the first FC stack 11A is configured as an open cathode system. That is, the first FC stack 11A is equipped with a hydrogen system 21 and an air and cooling system 22. The first FC stack 11A generates electricity by receiving hydrogen gas from the hydrogen system 21 and air from the air and cooling system 22.

[0027] The power generated by the first FC stack 11A is used to charge the battery 12 via wiring. The power charged in the battery 12 is supplied to the motor 13 via wiring. The motor 13 is driven by power supplied from the first FC stack 11A and / or the battery 12 via wiring.

[0028] The hydrogen system 21 is installed on the anode side of the first FC stack 11A. The hydrogen system 21 includes a hydrogen supply passage 31, an exhaust drainage passage 32, and a filling passage 33.

[0029] The hydrogen supply passage 31 is a passage for supplying hydrogen from the hydrogen tank 41, where hydrogen is stored, to the first FC stack 11A. The exhaust and drainage passage 32 is a passage for discharging hydrogen (i.e., hydrogen off-gas) and wastewater discharged from the first FC stack 11A.

[0030] Furthermore, the hydrogen system 21 includes, in order from the hydrogen tank 41 side, a hydrogen valve 51, a hydrogen pressure reducing valve 52, and an injector 53 in the hydrogen supply passage 31. The filling passage 33 is a passage for filling the hydrogen tank 41 with hydrogen from the filling port 42.

[0031] The hydrogen valve 51 is a solenoid valve that switches between supplying and shutting off hydrogen from the hydrogen tank 41 to the hydrogen supply passage 31. The hydrogen pressure reducing valve 52 is a pressure regulating valve for reducing the hydrogen pressure and is composed of, for example, a solenoid valve. The injector 53 is a solenoid valve that injects hydrogen introduced from the hydrogen tank 41 to the downstream side. The injector 53 is configured to adjust the hydrogen discharge pressure (hydrogen pressure) by adjusting the opening of the injection port by moving a needle valve, for example.

[0032] An exhaust and drainage valve 54 is provided in the exhaust and drainage passage 32. The exhaust and drainage valve 54 is a solenoid valve that switches between discharging and shutting off hydrogen off-gas and moisture.

[0033] In the hydrogen system 21, a pressure sensor 16 is provided in the hydrogen supply passage 31 between the injector 53 and the first FC stack 11A. This pressure sensor 16 is a sensor for measuring the pressure of the hydrogen injected from the injector 53, that is, the pressure of the hydrogen supplied to the first FC stack 11A.

[0034] On the other hand, the air and cooling systems 22 are individually provided on the cathode side of each FC stack 11A to 11C. Each air and cooling system 22 corresponding to each FC stack 11A to 11C includes an air passage 61 for circulating air and an electrically powered air supply fan 62 for supplying the air flowing through the passage 61 to each FC stack 11A to 11C. In this embodiment, the air system is configured as an open cathode system that also serves as a cooling system.

[0035] In the above configuration relating to the first FC stack 11A, the hydrogen supplied to the FC stack 11A from the hydrogen supply passage 31 is used for power generation in the FC stack 11A and then discharged to the outside as hydrogen off-gas via the exhaust drainage passage 32. In addition, the air supplied to the first FC stack 11A from the air passage 61 is used for power generation in the FC stack 11A and then discharged to the outside as air off-gas.

[0036] The electricity generated by the first FC stack 11A is used to charge the battery 12 or to drive the motor 13.

[0037] The second and third FC stacks 11B and 11C also have the same related configuration as described above and operate in the same manner. Their explanation is omitted here.

[0038] As shown in Figure 1, the fuel cell system 1 further includes a control device 20 for controlling the system 1. The control device 20 includes, for example, an arithmetic processing unit such as a CPU, a storage unit including a ROM for storing control programs and control data processed by the CPU, a RAM used as various work areas for control processing, and an input / output interface unit. The control device 20 performs various controls on the fuel cell system 1 according to the control program stored in the storage unit. In particular, in this embodiment, the control device 20 controls the hydrogen system 21, the air and cooling system 22 in order to control the fuel cell system 1.

[0039] In this embodiment, the control device 20 measures the voltage of the battery 12 (battery voltage) using a voltage measurement circuit provided inside it. The control device 20 also measures the generated current (FC current) of each FC stack 11A to 11C using a current measurement circuit provided inside it. Based on the measured battery voltage and FC current, the control device 20 controls the power generation of each FC stack 11A to 11C.

[0040] [About DC-DC converter-less systems] The fuel cell system 1 in this embodiment is configured as a DC-DC converter-less system. Therefore, in the fuel cell system 1, the FC voltage of each FC stack 11A to 11C is equal to (or approximately equal to) the battery voltage of the battery 12. As a result, the FC current becomes dependent on the battery voltage. In other words, the fuel cell system 1 supplies the power generated by the FC stacks 11A to 11C to the battery 12 and motor 13 without converting the FC voltage.

[0041] In this fuel cell system 1, the FC voltage is equal to the battery voltage, so each FC stack 11A to 11C performs "progressive power generation" according to the battery voltage during power generation. When the battery 12's charge level becomes high, the air supply fan 62 is stopped, lowering the FC voltage below the battery voltage and intermittently stopping power generation in each FC stack 11A to 11C to perform "low-current power generation." This improves fuel efficiency.

[0042] Figure 3 shows an example of the relationship between (A) FC current and FC voltage and (B) battery current and battery voltage in this fuel cell system 1 when there is no power consumption by the motor 13. As shown in Figure 3, when there is no power consumption by the motor 13, if the battery voltage is "49V", then the FC voltage will be equal to the battery voltage, which is "49V". As a result, the FC current will be "30A". Therefore, "FC output = 49V × 30A = 1.5kW" and "battery output = 49V × -30A = -1.5kW".

[0043] Here, since the fuel cell system 1 has three FC stacks 11A to 11C, there may be differences in the degree of degradation among the FC stacks 11A to 11C. Figure 4 shows an example of the relationship between (A) the FC current and FC voltage of each FC stack 11A to 11C with different degrees of degradation, and (B) the relationship between the battery current and battery voltage, in the case where there is no power consumption by the motor 13.

[0044] In Figure 4, the degree of degradation of each FC stack 11A to 11C is as follows: the third FC stack 11C has the greatest degradation with an FC current of "28A". The first FC stack 11A has the second greatest degradation with an FC current of "30A". The second FC stack 11B has the least degradation with an FC current of "32A". The degradation of each FC stack 11A to 11C is progressing in the direction indicated by the thick arrow Y1 in Figure 4(A). If the three FC stacks 11A to 11C are operated without considering these differences in degradation, the durability of the third FC stack 11C and the first FC stack 11A, which are more degraded than the others, will decrease more rapidly, raising concerns that the durability of the fuel cell system 1 will decrease. Therefore, in this embodiment, the power generation control of the three FC stacks 11A to 11C is performed as follows.

[0045] [Regarding power generation control of the three FC stacks] Figure 5 shows a flowchart illustrating an example of the power generation control content for the three FC stacks 11A to 11C in this embodiment. The control program related to this flowchart is stored in the memory unit of the control device 20.

[0046] When the process moves to the routine shown in Figure 5, the control device 20 determines in step 100 whether the "requested output" for the fuel cell system 1 is "4 (kW)" or more. In this embodiment, each FC stack 11A to 11C is set to generate the same "2 (kW)" of power. This "4 (kW)" is the power output that can be satisfied by the power generation of two of the three FC stacks 11A to 11C. The "requested output" also reflects the accelerator operation by the driver of the electric vehicle. If the result of this determination is positive, the control device 20 moves the process to step 110, and if the result is negative, the process moves to step 140.

[0047] In step 110, the control device 20 causes the three FC stacks 11A to 11C to generate power on a "spontaneous basis". To do this, the control device 20 activates the air supply fan 62 of the air and cooling system.

[0048] Next, in step 120, the control device 20 simultaneously measures the FC current of all FC stacks 11A to 11C.

[0049] Next, in step 130, the control device 20 learns the FC current of each FC stack 11A to 11C, and learns the numbers (identification numbers) of the FC stacks 11A to 11C in descending order of FC current, and then terminates the subsequent processing.

[0050] Meanwhile, in step 140, the control device 20 determines whether the "requested output" is "2-4 (kW)". If the result of this determination is positive, the control device 20 proceeds to step 150; if the result of this determination is negative, the control device 20 proceeds to step 160.

[0051] In step 150, the control device 20 allows the two FC stacks 11A~11C with high FC currents to generate power "by default". To do this, the control device 20 activates the air supply fan 62 and temporarily terminates the subsequent processing.

[0052] Meanwhile, in step 160, the control device 20 determines whether the "requested output" is "0.5 to 2 (kW)". If the result of this determination is positive, the control device 20 proceeds to step 170; if the result of this determination is negative, the control device 20 proceeds to step 180.

[0053] In step 170, the control device 20 allows one FC stack 11A~11C with a high FC current to "generate power as it pleases". To do this, the control device 20 activates the air supply fan 62 and temporarily terminates the subsequent processing.

[0054] On the other hand, in step 180, the control device 20 "intermittently stops" all FC stacks 11A to 11C. To do this, the control device 20 stops the air supply fan 62 and temporarily terminates the subsequent processing.

[0055] According to the power generation control described above, the control device 20 is configured to simultaneously measure the FC current of the three FC stacks 11A to 11C. The control device 20 is also configured to control the power generation of the three FC stacks 11A to 11C based on the difference in the FC current of each FC stack 11A to 11C that is measured simultaneously.

[0056] According to the power generation control described above, the control device 20 learns the FC current of each FC stack 11A to 11C that is measured simultaneously. The control device 20 also prioritizes generating power from the FC stack 11A to 11C with the highest FC current among the three learned FC currents, and changes the number of FC stacks 11A to 11C that generate power according to the required output of the fuel cell system 1.

[0057] According to the power generation control described above, the maximum required output of the fuel cell system 1 is configured to be "4 (kW)", which is satisfied by the power generation of "2 (N=2)" FC stacks 11A to 11C. The total number of FC stacks 11A to 11C is set to "3", or "N+1" or more. The control device 20 then uses the "2 (N=2)" FC stacks 11A to 11C corresponding to the highest FC currents among the three learned FC currents for power generation.

[0058] [Regarding the diagnosis of FC stack degradation abnormalities] As shown in Figure 1, in this embodiment, the control device 20 is configured to diagnose deterioration abnormalities in each FC stack 11A to 11C. An alarm device 70 is also provided to notify the diagnosis results. The control device 20 controls the alarm device 70 according to the diagnosis results.

[0059] In this embodiment, for each FC stack 11A to 11C, the system diagnoses degradation abnormalities in each FC stack 11A to 11C based on the difference in FC current according to the battery voltage. Figure 6 shows a judgment value map that defines the "warning judgment value" and "abnormal judgment value" for FC current in relation to "battery voltage". In Figure 6, when the "battery voltage" is "48V, 49V, 50V, 51V, 52V", the "warning judgment value" for FC current is "29A, 28A, 27A, 26A, 25A". Here, the "warning judgment value" corresponds to an example of the "first judgment value" of this disclosed technology. The "abnormal judgment value" corresponds to an example of the "second judgment value" of this disclosed technology.

[0060] In Figure 6, if the FC current reaches a "warning threshold" relative to the "battery voltage," the control device 20 causes the alarm device 70 to activate a warning notification. This warning notification indicates that at least one of the FC stacks 11A to 11C may be deteriorating. For example, when the "battery voltage" is "48V" and the FC current becomes "29A," the control device 20 causes the alarm device 70 to activate a warning notification.

[0061] On the other hand, in Figure 6, if the FC current reaches an "abnormal value" relative to the "battery voltage," the control device 20 causes the alarm device 70 to activate an abnormal notification. This abnormal notification indicates that at least one of the FC stacks 11A to 11C has already deteriorated. For example, when the "battery voltage" is "48V" and the FC current becomes "26A," the control device 20 causes the alarm device 70 to activate an abnormal notification.

[0062] In this embodiment, for example, the alarm device 70 is configured to sound and flash. In this case, the "warning notification operation" and the "abnormality notification operation" can be distinguished by operating the alarm device 70 in different patterns for sounding and flashing. The control device 20 also stores the diagnostic results regarding the deterioration of each FC stack 11A to 11C in a storage device. These diagnostic results can be checked by reading them from the storage device during the vehicle's periodic inspection. Alternatively, the alarm device 70 can be configured to have a communication device. In this case, the communication device can communicate with a server and send commands to the control device 20 to prompt the replacement of the FC stack in the electric vehicle in question or to prohibit the operation of the FC stack in question.

[0063] In the above-mentioned deterioration abnormality diagnosis, if the FC current is lower than the "warning threshold," the control device 20 will activate the alarm device 70 to warn that there is a risk of deterioration in the FC stack 11A to 11C. Furthermore, if the FC current is lower than the "abnormal threshold" which is lower than the "warning threshold," the control device 20 will activate the alarm device 70 to warn that there is a deterioration abnormality in the FC stack 11A to 11C.

[0064] In the above-described degradation abnormality diagnosis, the control device 20 is configured to measure the voltage of the battery 12. The control device 20 then changes the "warning judgment value" and the "abnormal judgment value" according to the battery voltage.

[0065] [Regarding the operation and effects of fuel cell systems] According to the configuration of the fuel cell system 1 of this embodiment described above, the control device 20 simultaneously measures the current of the three FC stacks 11A to 11C and controls the power generation of the three FC stacks 11A to 11C based on the difference in the FC current of each FC stack 11A to 11C measured simultaneously. Therefore, it is possible to use the FC stacks 11A to 11C with high FC current and low degradation for power generation, and to refrain from using the FC stacks 11A to 11C with low FC current and the risk of degradation for power generation. As a result, the degradation of each of the three FC stacks 11A to 11C can be suppressed, and the decrease in the durability of the fuel cell system 1 can be suppressed.

[0066] According to the configuration of this embodiment, the control device 20 prioritizes generating power from the FC stacks 11A to 11C with the highest value among the three learned FC currents, and changes the number of FC stacks 11A to 11C to generate power according to the required output of the fuel cell system 1. Therefore, it is possible to generate power that corresponds to the required output while refraining from using FC stacks 11A to 11C that have low FC currents and are at risk of degradation. In this way, it is possible to meet the required output while suppressing the widening of the degradation difference among the three FC stacks 11A to 11C.

[0067] According to the configuration of this embodiment, the control device 20 uses two FC stacks 11A to 11C corresponding to the highest values ​​among the (2+1) learned FC currents for power generation, making it possible to reserve one FC stack 11A to 11C that is not used for power generation. Therefore, the lifespan of the fuel cell system 1 can be extended.

[0068] According to the configuration of this embodiment, if the FC current is lower than the warning threshold (first current threshold), the control device 20 activates the alarm device 70 to issue a warning, thereby informing the user early that there is a risk of deterioration in the FC stacks 11A to 11C. Furthermore, if the FC current is lower than the abnormal threshold (second current threshold), the control device 20 activates the alarm device 70 to issue an abnormality notification, thereby informing the user early that there is a deterioration abnormality in the FC stacks 11A to 11C. As a result, the user can recognize the risk of deterioration or deterioration abnormality in each of the three FC stacks 11A to 11C early and take action promptly.

[0069] According to the configuration of this embodiment, the control device 20 changes the warning judgment value and abnormal judgment value for determining the risk of deterioration or deterioration abnormality of the FC stacks 11A to 11C according to the battery voltage value. Therefore, the deterioration of the FC stacks 11A to 11C can be accurately determined regardless of the difference in battery voltage state.

[0070] <Second Embodiment> Next, a second embodiment of the fuel cell system, which is implemented as a fuel cell system mounted on an electric vehicle, will be described with reference to the drawings. In the following description, components equivalent to those in the first embodiment will be denoted by the same reference numerals and their descriptions will be omitted, and the following description will focus on the differences.

[0071] [Regarding power generation control of the three FC stacks] This embodiment differs from the first embodiment in terms of the content of the power generation control for the three FC stacks 11A to 11C. Figure 7 shows a flowchart illustrating another example of the power generation control for the three FC stacks 11A to 11C according to this embodiment. The control program related to this flowchart is stored in the memory unit of the control device 20.

[0072] When the process moves to the routine shown in Figure 7, in step 200, the control device 20 causes the three FC stacks 11A to 11C to generate power in real-time (for example, once per trip). To do this, the control device 20 activates the air supply fan 62 of the air and cooling system.

[0073] Next, in step 210, the control device 20 simultaneously measures the FC current of all FC stacks 11A to 11C.

[0074] Next, in step 220, the control device 20 learns the FC current of each FC stack 11A to 11C, and also learns the numbers (identification numbers) of the FC stacks 11A to 11C in descending order of FC current.

[0075] Next, in step 230, the control device 20 determines whether the "requested output" is "2 (kW)" or greater. If the result of this determination is positive, the control device 20 proceeds to step 240; if the result of this determination is negative, the control device 20 proceeds to step 250.

[0076] In step 240, the control device 20 allows the two FC stacks 11A~11C with high FC currents to generate power "by default". To do this, the control device 20 activates the air supply fan 62 and temporarily terminates the subsequent processing.

[0077] Meanwhile, in step 250, the control device 20 determines whether the "requested output" is "0.5 to 2 (kW)". If the result of this determination is positive, the control device 20 proceeds to step 260; if the result of this determination is negative, the control device 20 proceeds to step 270.

[0078] In step 260, the control device 20 allows one FC stack 11A~11C with a high FC current to "generate power as it pleases". To do this, the control device 20 activates the air supply fan 62 and temporarily terminates the subsequent processing.

[0079] On the other hand, in step 270, the control device 20 "intermittently stops" all FC stacks 11A to 11C. To do this, the control device 20 stops the air supply fan 62 and temporarily terminates the subsequent processing.

[0080] [Regarding the operation and effects of fuel cell systems] Although the configuration of the fuel cell system 1 of this embodiment described above differs from the first embodiment in terms of the content of the power generation control of the three FC stacks 11A to 11C, it is possible to obtain the same operation and effects as the first embodiment.

[0081] <Another embodiment> Furthermore, this disclosed technology is not limited to the embodiments described above, and it may be implemented by appropriately modifying some parts of the configuration without departing from the spirit of the disclosed technology.

[0082] (1) In the above embodiment, three FC stacks 11A to 11C were provided as multiple fuel cells, but the number of FC stacks is not limited to three.

[0083] (2) In the above embodiment, the fuel cell system 1 was provided in an electric vehicle, but it can also be provided in a vehicle other than an electric vehicle.

[0084] (3) In the above embodiment, an open cathode system with a common air system and cooling system was adopted for each FC stack 11A to 11C, but a closed cathode system with separate air and cooling systems can also be adopted. [Industrial applicability]

[0085] This disclosed technology can be used, for example, in fuel cell systems installed in electric vehicles. [Explanation of Symbols]

[0086] 1. Fuel cell system 11A 1st FC Stack (Fuel Cell) 11B Second FC Stack (Fuel Cell) 11C Third FC Stack (Fuel Cell) 12 batteries 20 Control device 70 Alarm device

Claims

1. In a fuel cell system comprising multiple fuel cells connected in parallel and a single battery to which all of the multiple fuel cells are connected, and without a DC-DC converter, The system further comprises a control device for controlling the power generation of multiple fuel cells, The control device is configured to simultaneously measure the current of multiple fuel cells and to control the power generation of the multiple fuel cells based on the difference in the measured current values ​​of each fuel cell measured simultaneously. A fuel cell system characterized by the following features.

2. In the fuel cell system according to claim 1, The control device learns the current measurements taken simultaneously, prioritizes generating power from the fuel cell with the highest current measurement among the learned multiple current measurements, and changes the number of fuel cells to generate power according to the required output of the fuel cell system. A fuel cell system characterized by the following features.

3. In the fuel cell system according to claim 2, The outputs of multiple fuel cells are set to be the same as those of each other. The fuel cell system is configured such that the maximum required output is satisfied by the power generation of N fuel cells, and the total number of fuel cells is set to N+1 or more. The control device uses the N fuel cells corresponding to the learned current measurements, ordered from highest to lowest, to generate electricity. A fuel cell system characterized by the following features.

4. In the fuel cell system according to claim 1, The system further includes an alarm device for notifying of the deterioration of the fuel cell, If the current measurement value of the fuel cell is lower than the first current determination value, the control device will activate the alarm device to warn that there is a risk of deterioration in the fuel cell. If the current measurement value of the fuel cell is lower than the second current determination value which is lower than the first current measurement value, the control device will activate the alarm device to warn that there is a deterioration abnormality in the fuel cell. A fuel cell system characterized by the following features.

5. In the fuel cell system according to claim 4, The control device is configured to measure the voltage of the battery and to change the first determination current value and the second current determination value according to the measured voltage. A fuel cell system characterized by the following features.

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