Fuel cell system

Abstract

To provide a fuel cell system capable of inhibiting a failure of a fuel cell due to battery deterioration from being generated, while forming a simple system configuration having no apparatus for converting voltage of the fuel cell.SOLUTION: A fuel cell system 1 includes an FC stack 11 and a battery 12. The fuel cell system 1 is a system in which FC current depends on battery voltage. The fuel cell system records at least one of minimum FC voltage FCV and minimum battery voltage BV and maximum FC current FCA a plurality of times, respectively, within a predetermined time or a reach time until an integrated value of FC output reaches a predetermined value, and on the basis of the minimum FC voltage FCV and the minimum battery voltage BV recorded the plurality of times and the maximum FC current FCA recorded the plurality of times, determines the degree of deterioration in the battery using a map in which the degree of deterioration in the battery 12 is stipulated.SELECTED DRAWING: Figure 4

Description

Technical Field

[0001] The present disclosure relates to a fuel cell system having a fuel cell that generates electricity by receiving supplies of a fuel gas and an oxidant gas.

Background Art

[0002] Patent Document 1 discloses a fuel cell system having a fuel cell that generates electricity by receiving a supply of a fuel gas from a fuel gas system and a supply of an oxidant gas from an oxidant gas system.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] In a fuel cell system that does not have a device (for example, a DC-DC converter) for converting the voltage of a fuel cell (that is, the voltage of the power generated by the fuel cell), the current (that is, the current of the power generated by the fuel cell) and voltage of the fuel cell depend on the voltage of a battery. Therefore, when the battery deteriorates and the voltage of the battery decreases, the voltage of the fuel cell also decreases, and there is a risk that the current of the fuel cell becomes excessive. Then, there is a risk that problems such as deterioration due to excessive current being applied to the fuel cell may occur. Here, Patent Document 1 does not disclose or suggest anything about the problems in a fuel cell system that does not have a device for converting the voltage of such a fuel cell.

[0005] Therefore, the present disclosure has been made to solve the above-described problems, and an object thereof is to provide a fuel cell system that can suppress the occurrence of problems in a fuel cell while forming a simple system configuration that does not have a device for converting the voltage of the fuel cell.

Means for Solving the Problem

[0006] In one aspect of the present disclosure made to solve the above problems, in a fuel cell system having a fuel cell and a battery that charges the electric power generated by the fuel cell, the fuel cell system is a system in which the current of the fuel cell depends on the voltage of the battery, and within a predetermined time or within a reach time until the integrated value of the electric power generated by the fuel cell reaches a predetermined value, at least one of the minimum FC voltage that is the minimum value of the voltage of the fuel cell and the minimum battery voltage that is the minimum value of the voltage of the battery, and the maximum FC current that is the maximum value of the current of the fuel cell within the predetermined time or within the reach time are each recorded a plurality of times, and based on the minimum FC voltage or the minimum battery voltage recorded a plurality of times and the maximum FC current recorded a plurality of times, determining the degree of deterioration of the battery using a map in which the degree of deterioration of the battery is defined.

[0007] According to this aspect, the fuel cell system can be formed into a simple system configuration without a device for converting the voltage of the fuel cell. And in such a fuel cell system with a simple system configuration, based on the minimum FC voltage, the minimum battery voltage, and the maximum FC current whose values change significantly due to the deterioration of the battery, the degree of deterioration of the battery is determined using a map, so that the degree of deterioration of the battery can be accurately determined. Also, at this time, since the determination is made based on the values of the minimum FC voltage, the minimum battery voltage, and the maximum FC current recorded a plurality of times, the degree of deterioration of the battery can be determined more accurately. Therefore, according to the determined degree of deterioration of the battery, appropriately, measures can be taken to suppress the excessive increase in the current of the fuel cell accompanying the deterioration of the battery. Therefore, while forming a simple system configuration without a device for converting the voltage of the fuel cell, it is possible to suppress the occurrence of problems in the fuel cell accompanying the deterioration of the battery.

[0008] In the above aspect, it is preferable that in the map, the degree of battery degradation is defined such that the lower the minimum FC voltage or the minimum battery voltage and the higher the maximum FC current, the higher the degree of battery degradation.

[0009] According to this aspect, it is possible to more accurately determine the degree of battery degradation by using a map that reflects the characteristics when the battery degrades, that is, the characteristics in which the FC voltage and the battery voltage decrease and the FC current increases when the battery degrades.

Advantages of the Invention

[0010] According to the fuel cell system of the present disclosure, it is possible to suppress the occurrence of problems in the fuel cell due to battery degradation while forming a simple system configuration without a device for converting the voltage of the fuel cell.

Brief Description of the Drawings

[0011]

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5

[0012] An embodiment of the fuel cell system of the present disclosure will be described.

[0013] (Configuration of the fuel cell system) As shown in FIG. 1, in the fuel cell system 1 of the present embodiment, the FC stack 11, the battery 12, and the inverter 13 (or motor) are connected in parallel, forming a simple system configuration without a DCDC converter. That is, the fuel cell system 1 is a system without a DCDC converter.

[0014] Note that the DCDC converter is a device that converts the FC voltage, which is the voltage of the power generated by the FC stack 11. The FC stack 11 is an example of the "fuel cell" in the present disclosure. The FC voltage is an example of the "voltage of the fuel cell" in the present disclosure.

[0015] The fuel cell system 1 also has a hydrogen system 21 and an air system 22.

[0016] The FC stack 11 generates electricity by receiving the supply of fuel gas and oxidant gas. In this embodiment, the fuel gas is hydrogen gas and the oxidant gas is air (i.e., atmospheric air). That is, the FC stack 11 generates electricity by receiving the supply of hydrogen gas from the hydrogen system 21 and the supply of air from the air system 22. The power generated by the FC stack 11 is supplied to the battery 12 and the inverter 13.

[0017] The battery 12 is connected to the FC stack 11 and charges the power generated by the FC stack 11. The battery 12 is also connected to the inverter 13 and supplies the charged power to the inverter 13.

[0018] The inverter 13 is driven by receiving power supply from the FC stack 11 and / or the battery 12.

[0019] The hydrogen system 21 is provided on the anode side of the FC stack 11. This hydrogen system 21 includes a hydrogen supply passage 31, a hydrogen discharge passage 32, a filling passage 33, and a circulation flow path 34.

[0020] The hydrogen supply passage 31 is a passage for supplying hydrogen gas from the hydrogen tank 41 in which hydrogen gas is stored to the FC stack 11. The hydrogen discharge passage 32 is a passage for discharging the hydrogen gas (i.e., hydrogen off-gas) discharged from the FC stack 11.

[0021] The filling passage 33 is a passage for filling the hydrogen tank 41 with hydrogen gas from the filling port 51. The circulation flow path 34 is a passage connecting the hydrogen discharge passage 32 (specifically, the gas-liquid separator 71) and the ejector 64, and is a passage for circulating and supplying the hydrogen off-gas to the ejector 64.

[0022] Also, the hydrogen system 21 includes a valve 61, a pressure reducing valve 62, an injector 63, and an ejector 64 in this order from the hydrogen tank 41 side in the hydrogen supply passage 31.

[0023] The valve 61 is a valve that switches between supplying and blocking the supply of hydrogen gas from the hydrogen tank 41 to the hydrogen supply passage 31. The pressure reducing valve 62 is a pressure regulating valve for reducing the pressure of the hydrogen gas. The injector 63 is a device that injects the hydrogen gas led from the hydrogen tank 41 to the downstream side. The ejector 64 is a device that generates a negative pressure in the hydrogen gas injected from the injector 63, sucks in the hydrogen off-gas in the circulation flow path 34, mixes it with the hydrogen gas, and discharges it to the downstream side.

[0024] Also, the hydrogen system 21 includes a gas-liquid separator 71 and an exhaust drain valve 72 in this order from the FC stack 11 side in the hydrogen discharge passage 32. The gas-liquid separator 71 is a device that separates the moisture in the hydrogen off-gas. The exhaust drain valve 72 is a valve that switches between discharging and blocking the discharge of the hydrogen off-gas and moisture from the gas-liquid separator 71.

[0025] On the other hand, the air system 22 is provided on the cathode side of the FC stack 11. This air system 22 includes an air supply passage 81 and an air discharge passage 82. The air supply passage 81 is a passage for supplying air from the outside of the fuel cell system 1 to the FC stack 11. The air discharge passage 82 is a passage for discharging the air (i.e., air off-gas) discharged from the FC stack 11.

[0026] Also, the air system 22 includes an air compressor 91 and a supply-side air valve 92 in the air supply passage 81. The air compressor 91 is a device that supplies air to the FC stack 11. The supply-side air valve 92 is a valve that switches between supplying and blocking the supply of air from the air supply passage 81 to the FC stack 11.

[0027] Also, the air system 22 has a discharge-side air valve 101 arranged in the air discharge passage 82. The discharge-side air valve 101 is a valve that switches between discharging and blocking the discharge of air off-gas from the FC stack 11 to the air discharge passage 82.

[0028] Also, the fuel cell system 1 has a fan 111 for cooling the FC stack 11.

[0029] Furthermore, the fuel cell system 1 has a control unit 14. The control unit 14 is a device having, for example, an arithmetic processing unit such as a CPU, a storage unit such as a ROM that stores a control program and control data processed by the CPU, and a RAM used as various work areas for control processing, and an input / output interface unit. Then, the control unit 14 performs various controls of the fuel cell system 1 according to the control program stored in the storage unit.

[0030] In this embodiment, as various controls of the fuel cell system 1, the control unit 14 controls an inverter 13, a valve 61, a pressure reducing valve 62, an injector 63, a gas-liquid separator 71, an exhaust and drainage valve 72, an air compressor 91, a supply-side air valve 92, a discharge-side air valve 101, a fan 111, and the like.

[0031] (Operation of the fuel cell system) In the fuel cell system 1 configured as described above, the hydrogen gas supplied from the hydrogen supply passage 31 to the FC stack 11 is discharged to the outside of the fuel cell system 1 through the hydrogen discharge passage 32 as hydrogen off-gas after being used for power generation in the FC stack 11. Also, the air supplied from the air supply passage 81 to the FC stack 11 is discharged to the outside of the fuel cell system 1 through the air discharge passage 82 as air off-gas after being used for power generation in the FC stack 11.

[0032] In addition, the electric power generated by the FC stack 11 is supplied to the battery 12 to charge the battery 12 or supplied to the inverter 13 to be used for driving the inverter 13. Note that electric power is also supplied to the inverter 13 from the battery 12.

[0033] (Regarding the system without a DCDC converter) As shown in FIG. 1, the fuel cell system 1 of the present embodiment is a so-called system without a DCDC converter in which a DCDC converter is not arranged between the FC stack 11 and the battery 12. Therefore, in the fuel cell system 1, since the FC voltage becomes equal to (or almost equal to) the battery voltage, the FC current depends on the battery voltage. In other words, the fuel cell system 1 supplies the electric power generated by the FC stack 11 to the battery 12 and the inverter 13 without converting the FC voltage. Note that the FC current is an example of the "current of the fuel cell" in the present disclosure and is the current of the electric power generated by the FC stack 11. Also, the battery voltage is the voltage of the battery 12.

[0034] And in the fuel cell system 1, since the FC voltage thus becomes equal to the battery voltage, the FC stack 11 performs power generation according to the situation according to the battery voltage during power generation. Note that when the SOC (i.e., charge rate) of the battery 12 increases, the supply-side air valve 92 and the discharge-side air valve 101 are closed to lower the FC voltage below the battery voltage and intermittently stop the power generation of the FC stack 11.

[0035] For example, as shown in FIG. 2, when there is power consumption in the inverter 13 and the battery voltage is 47V, the FC voltage becomes equal to the battery voltage, i.e., 47V. As a result, the FC current becomes 50A. Thus, FC output = 47V × 50A = 2.3kW, and battery output = 47V × 100A = 4.7kW. By adding such FC output and battery output together, the power consumption in the inverter 13 = 47V × 150A = 7.0kW can be obtained. Note that the FC output is the power generated by the FC stack 11 and output from the FC stack 11. The battery output is the power output from the battery 12.

[0036] Also, as shown in FIG. 3, when there is no power consumption in the inverter 13 and the battery voltage is 49V, the FC voltage becomes equal to the battery voltage, i.e., 49V. As a result, the FC current becomes 30A. Thus, FC output = 49V × 30A = 1.5kW, and battery output = 49V × -30A = -1.5kW.

[0037] In the fuel cell system 1 which is such a DCDC converterless system, the FC current and the FC voltage depend on the battery voltage. Therefore, when the battery 12 is deteriorated, due to the decrease in the battery voltage, the FC voltage also decreases, and according to the current-voltage characteristics (i.e., IV characteristics) of the FC stack 11 (specifically, the characteristic that the FC current increases as the FC voltage decreases), there is a possibility that the FC current becomes excessive. When the FC current becomes excessive, the damage to the FC stack 11 becomes large, and there is a possibility that problems such as deterioration of the FC stack 11 due to excessive current being applied to the FC stack 11 occur. Thus, there is a possibility that problems of the FC stack 11 occur along with the deterioration of the battery 12.

[0038] Therefore, in this embodiment, by accurately determining the degree of deterioration of the battery 12, based on this determination result, it is possible to appropriately take measures to suppress the occurrence of problems of the FC stack 11 along with the deterioration of the battery 12.

[0039] (Method for Detecting Deterioration State of Battery) The control unit 14 detects the deterioration state of the battery 12 as shown in FIG. 4, for example.

[0040] As shown in FIG. 4, first, the control unit 14 records the minimum FC voltage FCV, which is the minimum value of the FC voltage, the minimum battery voltage BV, which is the minimum value of the battery voltage, and the maximum FC current FCA, which is the maximum value of the FC current, within a predetermined time (for example, 30 seconds) or within the arrival time until the integrated value of the FC output reaches a predetermined value (step S1).

[0041] Note that the control unit 14 may record only one of the minimum FC voltage FCV and the minimum battery voltage BV. Further, since the fuel cell system 1 of the present embodiment is a system without a DCDC converter, the FC voltage depends on the battery voltage. Therefore, the minimum FC voltage FCV and the minimum battery voltage BV are equal or substantially equal.

[0042] Next, the control unit 14 records the minimum FC voltage FCV, the minimum battery voltage BV, and the maximum FC current FCA as past data (step S2). In this way, the control unit 14 records the minimum FC voltage FCV, the minimum battery voltage BV, and the maximum FC current FCA every time the predetermined time or the arrival time elapses. As a result, the control unit 14 records the data of the minimum FC voltage FCV, the data of the minimum battery voltage BV, and the data of the maximum FC current FCA a plurality of times respectively. Note that the control unit 14 may record only one of the minimum FC voltage FCV and the minimum battery voltage BV as past data.

[0043] Next, the control unit 14 determines the deterioration state of the battery 12 by using the map shown in FIG. 5 based on the lowest FC voltages FCV or the lowest battery voltages BV of several (for example, three) past ones and the maximum FC current FCA (step S3). In this way, the control unit 14 determines the degree of deterioration of the battery 12 by using a map in which the degree of deterioration of the battery 12 is defined based on the data of the lowest FC voltages FCV or the data of the lowest battery voltages BV recorded multiple times and the data of the maximum FC current FCA recorded multiple times.

[0044] Specifically, the control unit 14 determines the deterioration state of the battery 12 by using the map shown in FIG. 5 based on, for example, the average value (or the minimum value) of the lowest FC voltages FCV or the lowest battery voltages BV of the three most recent past ones and the average value (or the maximum value) of the maximum FC currents FCA of the three most recent past ones.

[0045] Then, for example, as shown in FIG. 5, when the average value (or the minimum value) of the lowest FC voltages FCV or the lowest battery voltages BV of the three past ones is "45 V" and the average value (or the maximum value) of the maximum FC currents FCA of the three past ones is "50 A", the control unit 14 sets the degree of deterioration of the battery 12 to "1" and determines that the battery 12 has not deteriorated.

[0046] Also, when the average value (or the minimum value) of the lowest FC voltages FCV or the lowest battery voltages BV of the three past ones is "50 V" and the average value (or the maximum value) of the maximum FC currents FCA of the three past ones is "50 A" or "60 V", the control unit 14 also sets the degree of deterioration of the battery 12 to "1" and determines that the battery 12 has not deteriorated.

[0047] On the other hand, when the average value (or the minimum value) of the lowest FC voltages FCV or the lowest battery voltages BV of the three past ones is "40 V" and the average value (or the maximum value) of the maximum FC currents FCA of the three past ones is "70 A", the control unit 14 sets the degree of deterioration of the battery 12 to "3" and determines that the battery 12 has deteriorated.

[0048] On the other hand, under other conditions, the control unit 14 determines that the degree of deterioration of the battery 12 is "2" or "2.5", indicating that the deterioration of the battery 12 is progressing.

[0049] Thus, in the present embodiment, as shown in the map of FIG. 5 for example, it is defined that the lower the minimum FC voltage FCV or the minimum battery voltage BV, and the higher the maximum FC current FCA, the higher the degree of deterioration of the battery 12 tends to be.

[0050] Note that the detection of the deterioration state of the battery 12 shown in FIG. 4 is basically performed periodically every time a predetermined time elapses during the operation of the fuel cell system 1, but it is not limited thereto, and it may be performed when the necessary FC output in the fuel cell system 1 becomes equal to or greater than a predetermined value and is large (for example, when the power consumption of the inverter 13 becomes equal to or greater than a predetermined value).

[0051] (Regarding the effects of the present embodiment) According to the present embodiment, the fuel cell system 1 is a system without a DCDC converter, and the FC current depends on the battery voltage. In such a fuel cell system 1 without a DCDC converter, the control unit 14 records at least one of the minimum FC voltage FCV and the minimum battery voltage BV, and the maximum FC current FCA, a plurality of times, and based on the minimum FC voltage FCV or the minimum battery voltage BV recorded a plurality of times, and the maximum FC current FCA recorded a plurality of times, for example, using the map of FIG. 5, determines the degree of deterioration of the battery 12.

[0052] In this way, the fuel cell system 1 can be formed into a simple system configuration without a DC / DC converter. And in the fuel cell system 1 with such a system configuration, based on the minimum FC voltage FCV, the minimum battery voltage BV, and the maximum FC current FCA whose values change significantly due to the deterioration of the battery 12, for example, using the map in FIG. 5, the degree of deterioration of the battery 12 is determined, so that the degree of deterioration of the battery 12 can be accurately determined. Also, at this time, since it is determined based on the values of the minimum FC voltage FCV, the minimum battery voltage BV, and the maximum FC current FCA recorded multiple times, the degree of deterioration of the battery 12 can be determined more accurately.

[0053] Therefore, according to the determined degree of deterioration of the battery 12, appropriately, measures can be taken to suppress the excessive increase of the FC current due to the deterioration of the battery 12. Thus, while forming a simple system configuration without a DC / DC converter, it is possible to suppress the occurrence of problems in the FC stack 11 due to the deterioration of the battery 12.

[0054] Also, in the map of FIG. 5, it is defined that the higher the degree of deterioration of the battery 12 tends to be, the lower the minimum FC voltage FCV or the minimum battery voltage BV is, and the higher the maximum FC current FCA is.

[0055] In this way, using the map that reflects the characteristics when the battery 12 deteriorates, that is, the characteristics that the FC voltage and the battery voltage become low and the FC current becomes high when the battery 12 deteriorates, the degree of deterioration of the battery 12 can be determined more accurately.

[0056] Note that the above-described embodiments are merely examples and do not limit the present disclosure at all. Of course, various improvements and modifications are possible without departing from the gist thereof.

Description of Reference Numerals

[0057] 1 Fuel cell system 11 FC stack 12 Battery 13 Inverter (or motor) 14 Control unit 21 Hydrogen system 22 Air system 31 Hydrogen supply passage 32 Hydrogen discharge passage 41 Hydrogen tank 81 Air supply passage 82 Air discharge passage 91 Air compressor FCV Minimum FC voltage BV Minimum battery voltage FCA Maximum FC current

Claims

1. A fuel cell system having a fuel cell and a battery that is charged with power generated by the fuel cell, The fuel cell system is a system in which a current of the fuel cell depends on a voltage of the battery, At least one of a minimum FC voltage, which is the minimum value of the voltage of the fuel cell, and a minimum battery voltage, which is the minimum value of the voltage of the battery, within a predetermined time or within the time until the integrated value of the power generated by the fuel cell reaches a predetermined value; a maximum FC current, which is a maximum value of a current of the fuel cell within the predetermined time or the arrival time; Each was recorded multiple times, determining a degree of deterioration of the battery using a map in which a degree of deterioration of the battery is defined based on the minimum FC voltage or the minimum battery voltage recorded a plurality of times and the maximum FC current recorded a plurality of times; A fuel cell system comprising:

2. 2. The fuel cell system of claim 1, The map specifies that the lower the minimum FC voltage or the minimum battery voltage and the higher the maximum FC current, the higher the degree of deterioration of the battery; A fuel cell system comprising:

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