Fuel cell system

Abstract

This fuel cell system comprises: a fuel cell; a battery to be charged with power generated by the fuel cell; and an inverter or motor that is driven by receiving supply of power from the fuel cell and / or the battery. In the fuel cell system, current of the fuel cell depends on the voltage of the battery, and the timing for driving the inverter or the motor is adjusted in accordance with the state of the battery.

Description

fuel cell system

[0001] The present disclosure relates to a fuel cell system having a fuel cell that generates electricity when supplied with a fuel gas and an oxidant gas.

[0002] Patent Document 1 discloses a fuel cell system having a fuel cell that receives a supply of fuel gas from a fuel gas system and a supply of oxidant gas from an oxidant gas system to generate electricity.

[0003] Japanese Patent Application Laid-Open No. 2022-185247

[0004] In a fuel cell system that does not have a device (e.g., a DC-DC converter) that converts the fuel cell voltage (i.e., the voltage of the power generated by the fuel cell), the fuel cell current (i.e., the current of the power generated by the fuel cell) and voltage depend on the battery voltage. Therefore, if the battery deteriorates and the battery voltage drops, the fuel cell voltage also drops, and there is a risk that the fuel cell current will become excessive. This could result in problems such as deterioration due to excessive current being applied to the fuel cell. However, Patent Document 1 does not disclose or suggest anything about the issues that arise in a fuel cell system that does not have a device that converts the fuel cell voltage.

[0005] Therefore, the present disclosure has been made to solve the above-mentioned problems, and aims to provide a fuel cell system that can form a simple system configuration that does not have equipment that converts the voltage of the fuel cell, while suppressing the occurrence of fuel cell malfunctions due to battery deterioration.

[0006] One form of the present disclosure made to solve the above problem is a fuel cell system having a fuel cell, a battery that charges with power generated by the fuel cell, and an inverter or motor that is driven by power supplied from the fuel cell and / or the battery, wherein the fuel cell system is a system in which the current of the fuel cell depends on the voltage of the battery, and the drive timing of the inverter or the motor is adjusted according to the state of the battery.

[0007] According to this aspect, the fuel cell system can be configured with a simple system configuration that does not include a device that converts the fuel cell voltage. In such a fuel cell system that does not include a device that converts the fuel cell voltage, when the battery deteriorates, the inverter or motor is stopped and the fuel cell generates electricity, thereby preventing the battery voltage from dropping due to power consumption caused by driving the inverter or motor, and preventing the fuel cell current from becoming excessive. This prevents the fuel cell from malfunctioning, such as deterioration, due to excessive current being applied to the fuel cell caused by excessive fuel cell current. This allows for a simple system configuration that does not include a device that converts the fuel cell voltage to be configured, while preventing fuel cell malfunctions caused by battery deterioration.

[0008] In the above aspect, when starting up the fuel cell system, if the SOC of the battery is equal to or lower than a first predetermined SOC value, or if the voltage of the battery is equal to or lower than a predetermined battery voltage value, or if deterioration of the battery is detected, it is preferable to generate electricity in the fuel cell with the inverter or the motor stopped, and then maintain the inverter or the motor stopped until the SOC of the battery becomes equal to or higher than a second predetermined SOC value that is greater than the first predetermined SOC value.

[0009] According to this aspect, when starting up a stopped fuel cell system, if the battery is degraded or is likely to be degraded, the inverter or motor is stopped and the fuel cell generates electricity. Then, the inverter or motor is stopped and the fuel cell continues to generate electricity until the battery's SOC is sufficiently secured. This prevents the fuel cell current from becoming excessively large due to power consumption caused by driving the inverter or motor when starting up the fuel cell system. Therefore, when starting up a stopped fuel cell system, it is possible to prevent malfunctions in the fuel cell caused by battery degradation.

[0010] In the above aspect, if deterioration of the battery is detected when the fuel cell system is stopped, it is preferable to continue generating electricity in the fuel cell with the inverter or the motor stopped until the SOC of the battery becomes equal to or greater than a third predetermined SOC value.

[0011] According to this aspect, when an operating fuel cell system is shut down, the fuel cell generates power to increase the battery's SOC to a third predetermined SOC value in preparation for subsequent startup of the fuel cell system. If battery degradation is detected at this time, the fuel cell generates power with the inverter or motor stopped. This prevents the fuel cell current from becoming excessive due to power consumption caused by driving the inverter or motor. Therefore, when the fuel cell system is shut down, malfunctions in the fuel cell caused by battery degradation can be prevented.

[0012] The fuel cell system of the present disclosure can form a simple system configuration that does not include a device for converting the voltage of the fuel cell, while suppressing the occurrence of malfunctions in the fuel cell due to battery degradation.

[0013] Fig. 1 is a configuration diagram of a fuel cell system of the present embodiment. Fig. 2 is a diagram showing an example of FC current, FC voltage, battery current, and battery voltage when there is power consumption in an inverter in a DCDC converter-less fuel cell system. Fig. 3 is a diagram showing an example of FC current, FC voltage, battery current, and battery voltage when there is no power consumption in an inverter in a DCDC converter-less fuel cell system. Fig. 4 is a flowchart showing the contents of control performed when starting up the fuel cell system. Fig. 5 is a flowchart showing the contents of control performed when stopping the fuel cell system.

[0014] An embodiment of a fuel cell system according to the present disclosure will now be described.

[0015] 1, in the fuel cell system 1 of this embodiment, an FC stack 11, a battery 12, and an inverter 13 (or a motor) are connected in parallel, forming a simple system configuration that does not include a DC-DC converter. In other words, the fuel cell system 1 is a DC-DC converter-less system.

[0016] The DC-DC converter is a device that converts the FC voltage, which is the voltage of the power of the FC stack 11 that is supplied to the battery 12. The FC stack 11 is an example of a "fuel cell" in the present disclosure. The FC voltage is an example of a "fuel cell voltage" in the present disclosure.

[0017] The fuel cell system 1 also has a hydrogen system 21 and an air system 22 .

[0018] The FC stack 11 generates power by receiving a supply of fuel gas and an oxidant gas. In this embodiment, the fuel gas is hydrogen gas, and the oxidant gas is air. That is, the FC stack 11 generates power by receiving a supply of hydrogen gas from a hydrogen system 21 and a supply of air from an air system 22. The power generated by the FC stack 11 is then supplied to the battery 12 and the inverter 13.

[0019] The battery 12 is connected to the FC stack 11 and is charged with 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.

[0020] The inverter 13 is driven by receiving power from the FC stack 11 and / or the battery 12 .

[0021] The hydrogen system 21 is provided on the anode side of the FC stack 11. The hydrogen system 21 includes a hydrogen supply passage 31, a hydrogen discharge passage 32, a filling passage 33, and a circulation passage .

[0022] The hydrogen supply passage 31 is a passage for supplying hydrogen gas from a hydrogen tank 41 in which hydrogen gas is stored to the FC stack 11. The hydrogen discharge passage 32 is a passage for discharging hydrogen gas (i.e., hydrogen off-gas) discharged from the FC stack 11.

[0023] The filling passage 33 is a passage for filling hydrogen gas into the hydrogen tank 41 from the filling port 51. The circulation flow path 34 is a passage that connects the hydrogen discharge passage 32 (more specifically, the gas-liquid separator 71) and the ejector 64, and is a passage for circulating and supplying hydrogen off-gas to the ejector 64.

[0024] The hydrogen system 21 also 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.

[0025] The valve 61 switches between supplying and blocking 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 hydrogen gas. The injector 63 is a device that injects hydrogen gas introduced from the hydrogen tank 41 downstream. The ejector 64 is a device that generates negative pressure in the hydrogen gas injected from the injector 63, sucks in hydrogen off-gas from the circulation flow path 34, mixes it with the hydrogen gas, and discharges it downstream.

[0026] The hydrogen system 21 also includes, in the hydrogen discharge passage 32, a gas-liquid separator 71 and an exhaust / drain valve 72, in that order from the FC stack 11 side. The gas-liquid separator 71 is a device that separates moisture from the hydrogen off-gas. The exhaust / drain valve 72 is a valve that switches between discharging and blocking the hydrogen off-gas and moisture from the gas-liquid separator 71.

[0027] 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 outside the fuel cell system 1 to the FC stack 11. The air discharge passage 82 is a passage for discharging air (i.e., air off-gas) discharged from the FC stack 11.

[0028] The air system 22 also 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 air from the air supply passage 81 to the FC stack 11.

[0029] The air system 22 also has a discharge-side air valve 101 disposed in the air discharge passage 82. The discharge-side air valve 101 is a valve that switches between discharging and blocking the air off-gas from the FC stack 11 to the air discharge passage 82.

[0030] The fuel cell system 1 also has a fan 111 that cools the FC stack 11 .

[0031] The fuel cell system 1 further includes a control unit 14. The control unit 14 is a device having, for example, an arithmetic processing unit such as a CPU, a memory unit such as a ROM for storing control programs and control data processed by the CPU and a RAM used as various work areas for control processing, and an input / output interface unit. The control unit 14 performs various controls of the fuel cell system 1 in accordance with the control programs stored in the memory unit.

[0032] In this embodiment, the control unit 14 controls various components of the fuel cell system 1, such as the inverter 13, valve 61, pressure reducing valve 62, injector 63, ejector 64, gas-liquid separator 71, exhaust drain valve 72, air compressor 91, supply side air valve 92, discharge side air valve 101, and fan 111.

[0033] (Operation of Fuel Cell System) In the fuel cell system 1 configured as described above, hydrogen gas supplied from the hydrogen supply passage 31 to the FC stack 11 is used for power generation in the FC stack 11, and then discharged from the FC stack 11 as hydrogen off-gas via the hydrogen discharge passage 32 to the outside of the fuel cell system 1. In addition, air supplied from the air supply passage 81 to the FC stack 11 is used for power generation in the FC stack 11, and then discharged from the FC stack 11 as air off-gas via the air discharge passage 82 to the outside of the fuel cell system 1.

[0034] The electric power generated by the FC stack 11 is supplied to the battery 12 to charge the battery 12, or is supplied to the inverter 13 to drive the inverter 13. The inverter 13 is also supplied with electric power from the battery 12.

[0035] (Regarding a DCDC converter-less system) As shown in FIG. 1 , the fuel cell system 1 of this embodiment is a so-called DCDC converter-less system in which a DCDC converter is not disposed between the FC stack 11 and the battery 12. Therefore, in the fuel cell system 1, the FC voltage is equal to (or approximately equal to) the battery voltage, and the FC current depends on the battery voltage. In other words, the fuel cell system 1 supplies the power generated in 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 "fuel cell current" in this disclosure, and is the current of the power generated in the FC stack 11. Note that the battery voltage is the voltage of the battery 12.

[0036] In the fuel cell system 1, the FC voltage becomes equal to the battery voltage in this way, so the FC stack 11 generates electricity as it goes according to the battery voltage. When the SOC (i.e., the charging rate) of the battery 12 becomes high, the supply-side air valve 92 and the discharge-side air valve 101 are closed to reduce the FC voltage below the battery voltage, and power generation by the FC stack 11 is stopped intermittently.

[0037] For example, as shown in FIG. 2, when there is power consumption in the inverter 13, if the battery voltage is 47 V, the FC voltage will be equal to the battery voltage, 47 V. As a result, the FC current will be 50 A. Therefore, the FC output = 47 V × 50 A = 2.3 kW, and the battery output = 47 V × 100 A = 4.7 kW. By adding up these FC output and battery output, the power consumption in the inverter 13 = 47 V × 150 A = 7.0 kW can be obtained. 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.

[0038] 3, if there is no power consumption in the inverter 13 and the battery voltage is 49 V, the FC voltage will be equal to the battery voltage, 49 V. This will result in the FC current being 30 A. Therefore, the FC output = 49 V x 30 A = 1.5 kW, and the battery output = 49 V x -30 A = -1.5 kW.

[0039] In the fuel cell system 1, which is a DCDC converter-less system, the FC current and FC voltage depend on the battery voltage. Therefore, if the battery 12 is degraded, the FC voltage also decreases due to a drop in battery voltage, and the FC current may become excessive due to the current-voltage characteristics (i.e., IV characteristics) of the FC stack 11 (specifically, the characteristic in which the FC current increases as the FC voltage decreases). If the FC current becomes excessive, damage to the FC stack 11 may become greater, and malfunctions of the FC stack 11, such as deterioration due to excessive current being applied to the FC stack 11, may occur. Furthermore, if the inverter 13 is also driven at this time and power is consumed, this may further exacerbate the FC current becoming excessive.

[0040] Therefore, in this embodiment, when starting or stopping the fuel cell system 1, the control unit 14 performs the control described below to prevent malfunctions in the FC stack 11 due to deterioration of the battery 12.

[0041] (Control Performed When Starting Up the Fuel Cell System) First, when starting up the fuel cell system 1 that has been stopped, the control unit 14 performs control shown in FIG. 4, for example.

[0042] 4, when the control unit 14 first recognizes that the start switch (not shown) of the fuel cell system 1 has been turned on (step S1), it determines whether any of the following conditions is met (step S2): the SOC of the battery 12 is equal to or lower than a predetermined value SA (e.g., 40%), the battery voltage is equal to or lower than a predetermined voltage value PV (e.g., 46 V), or deterioration of the battery 12 has been detected. Note that the predetermined value SA is an example of a "first predetermined SOC value" in the present disclosure. Also, the predetermined voltage value PV is an example of a "predetermined battery voltage value" in the present disclosure.

[0043] Then, if any of the conditions in step S2 (i.e., at least one) is met (step S2: YES), the control unit 14 turns on the startup standby lamp (not shown) (step S3) and stops the inverter 13 (or the motor) (step S4).

[0044] The control unit 14 detects that the battery 12 has deteriorated, for example, when the slope of the line representing the current-voltage characteristic (i.e., IV characteristic) of the battery 12 (specifically, the characteristic in which the battery current (i.e., the current of the battery 12) increases as the battery voltage decreases) becomes greater than a predetermined value.

[0045] Then, the control unit 14 causes the FC stack 11 to generate power (that is, let the power generation proceed as it comes) while stopping the inverter 13 (or the motor) (step S5).

[0046] In this way, when starting up the stopped fuel cell system 1, if any of the conditions in step S2 is met, the battery 12 is degraded or is likely to be degraded, so the control unit 14 causes the FC stack 11 to generate power while stopping the inverter 13. This suppresses an increase in FC current due to power consumption by the inverter 13.

[0047] Next, when the SOC of the battery 12 becomes equal to or greater than a predetermined value SB (e.g., 80%) (step S6: YES), the control unit 14 turns off the start standby lamp (step S7) and permits the inverter 13 (or the motor) to be driven (step S8). The predetermined value SB is a value greater than the predetermined value SA and is an example of the "second predetermined SOC value" in the present disclosure.

[0048] In this manner, in this embodiment, the control unit 14 maintains the inverter 13 in a stopped state until the SOC of the battery 12 becomes equal to or greater than the predetermined value SB.

[0049] Thereafter, the control unit 14 drives the inverter 13 (or the motor) in the normal mode (step S9). That is, the control unit 14 drives the inverter 13 in the normal mode when the fuel cell system 1 is in operation.

[0050] If none of the conditions in step S2 is met (step S2: NO), the control unit 14 continues to drive the inverter 13 (or the motor) in the normal mode (step S9).

[0051] In this way, when the stopped fuel cell system 1 is started up and the battery 12 is deteriorated, the inverter 13 is stopped when generating power in the FC stack 11. The inverter 13 is kept stopped until the SOC of the battery 12 is sufficiently ensured, that is, until the SOC of the battery 12 is sufficiently ensured so that the battery 12 can supply sufficient power to drive the inverter 13 and the amount of power supplied from the FC stack 11 can be reduced. In this way, in this embodiment, the control unit 14 adjusts the drive timing of the inverter 13 depending on the state of the battery 12.

[0052] (Control Performed When Shutting Down the Fuel Cell System) When shutting down the fuel cell system 1 during operation, the control unit 14 performs control shown in FIG. 5, for example.

[0053] As shown in FIG. 5, first, when the control unit 14 recognizes that the stop switch (not shown) of the fuel cell system 1 has been turned on (step S101), it determines whether deterioration of the battery 12 has been detected (step S102).

[0054] If deterioration of the battery 12 is detected (step S102: YES), the control unit 14 stops the inverter 13 (or the motor) and causes the FC stack 11 to generate electricity (i.e., generate electricity as it comes) (step S103).

[0055] In this way, if deterioration of the battery 12 is detected when the fuel cell system 1 is stopped during operation, the inverter 13 is stopped and the FC stack 11 continues to generate power.

[0056] When the SOC of the battery 12 becomes equal to or greater than a predetermined value SC (e.g., 80%) (step S104: YES), the control unit 14 stops power generation by the FC stack 11 (step S105). The predetermined value SC is an example of the "third predetermined SOC value" in the present disclosure.

[0057] In this way, the FC stack 11 continues to generate electricity until the SOC of the battery 12 reaches or exceeds the predetermined value SC.

[0058] If deterioration of the battery 12 is not detected in step S102 (step S102: NO), the control unit 14 stops power generation by the FC stack 11 (step S105).

[0059] In this way, when stopping the fuel cell system 1 in operation, if deterioration of the battery 12 is detected, the inverter 13 is stopped and the FC stack 11 continues to generate electricity until the SOC of the battery 12 reaches or exceeds a predetermined value SC.

[0060] (Operational Effects of the Present Embodiment) According to the present embodiment, the fuel cell system 1 is a DCDC converter-less system in which the FC current depends on the battery voltage. In the fuel cell system 1, which is such a DCDC converter-less system, the control unit 14 adjusts the drive timing of the inverter 13 according to the state of the battery 12.

[0061] As described above, since the fuel cell system 1 is a DCDC converter-less system, the fuel cell system 1 can be configured with a simple system configuration. In such a DCDC converter-less fuel cell system 1, when the battery 12 deteriorates, the inverter 13 is stopped and the FC stack 11 generates power, thereby preventing the battery voltage from dropping due to power consumption caused by driving the inverter 13 and causing the FC current to become excessive. This prevents the FC stack 11 from malfunctioning, such as deterioration caused by excessive current being applied to the FC stack 11 due to excessive FC current. Therefore, a simple system configuration that does not include a device for converting FC voltage can be configured, while preventing the FC stack 11 from malfunctioning due to deterioration of the battery 12.

[0062] Furthermore, when starting up the fuel cell system 1, if the SOC of the battery 12 is equal to or lower than a predetermined value SA, if the battery voltage is equal to or lower than a predetermined voltage value PV, or if deterioration of the battery 12 is detected, the control unit 14 stops the inverter 13 and causes the FC stack 11 to generate electricity. Thereafter, the control unit 14 maintains the stopped state of the inverter 13 until the SOC of the battery 12 becomes equal to or higher than a predetermined value SB.

[0063] In this way, when starting up the fuel cell system 1 that has been stopped, if the battery 12 has deteriorated or is likely to deteriorate, the FC stack 11 generates electricity with the inverter 13 stopped. Then, thereafter, the FC stack 11 continues to generate electricity with the inverter 13 stopped until the SOC of the battery 12 reaches or exceeds a predetermined value SB and is sufficiently secured. This makes it possible to prevent the FC current from becoming excessively large due to power consumption caused by driving the inverter 13 when starting up the fuel cell system 1. Therefore, it is possible to prevent malfunctions in the FC stack 11 caused by deterioration of the battery 12 when starting up the fuel cell system 1 that has been stopped.

[0064] In addition, if the control unit 14 detects deterioration of the battery 12 when stopping the fuel cell system 1, it stops the inverter 13 and causes the FC stack 11 to generate electricity until the SOC of the battery 12 becomes equal to or greater than a predetermined value SC.

[0065] In this way, when the fuel cell system 1 is stopped during operation, the FC stack 11 generates power to increase the SOC of the battery 12 to a predetermined value SC in preparation for the subsequent startup of the fuel cell system 1. If degradation of the battery 12 is detected at this time, the FC stack 11 generates power with the inverter 13 stopped. This makes it possible to prevent the FC current from becoming excessively large due to power consumption caused by driving the inverter 13. Therefore, when the fuel cell system 1 is stopped, it is possible to prevent malfunctions in the FC stack 11 caused by degradation of the battery 12.

[0066] It should be noted that the above-described embodiments are merely examples and do not limit the present disclosure in any way. It goes without saying that various improvements and modifications are possible within the scope of the gist of the present disclosure.

[0067] REFERENCE SIGNS LIST 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 SA predetermined value SB predetermined value SC predetermined value PV predetermined voltage value

Claims

1. A fuel cell system having a fuel cell, a battery that charges with power generated by the fuel cell, and an inverter or a motor that is driven by power supplied from the fuel cell and / or the battery, wherein the current of the fuel cell depends on the voltage of the battery, and the drive timing of the inverter or the motor is adjusted according to the state of the battery.

2. A fuel cell system according to claim 1, characterized in that, when starting up the fuel cell system, if the SOC of the battery is equal to or lower than a first predetermined SOC value, or if the voltage of the battery is equal to or lower than a predetermined battery voltage value, or if deterioration of the battery is detected, the fuel cell generates electricity with the inverter or the motor stopped, and thereafter, the inverter or the motor is maintained in a stopped state until the SOC of the battery reaches or exceeds a second predetermined SOC value which is greater than the first predetermined SOC value.

3. A fuel cell system according to claim 1 or 2, characterized in that, if deterioration of the battery is detected when the fuel cell system is stopped, the fuel cell continues to generate power with the inverter or the motor stopped until the SOC of the battery reaches or exceeds a third predetermined SOC value.

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