Control device, fuel cell system, control method for fuel cell system, and program

Abstract

To provide an excellent control device, a fuel cell system, a control method for the fuel cell system, and a program.SOLUTION: A control device 10 is capable of implementing: an activation step of activating a fuel cell by supplying a fuel gas to the fuel cell and controlling a valve 52 to supply an oxidant gas in a first flow quantity Q1 to the fuel cell; a warming-up preparation step of preparing warming-up of the fuel cell by controlling the valve to set an oxidant gas flow quantity to a second flow quantity Q2 smaller than the first flow quantity Q1 after the activation step; and a warming-up step of warming up the fuel cell in a state where an oxidant gas in a third flow quantity Q3 larger than the second flow quantity is supplied to the fuel cell after the warming-up preparation step.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present invention relates to a control device, a fuel cell system, a control method for a fuel cell system, and a program. [Background technology]

[0002] In recent years, research and development into fuel cell systems that contribute to energy efficiency has been conducted in order to ensure that more people have access to affordable, reliable, sustainable and advanced energy.

[0003] For example, Patent Document 1 discloses that the fuel cell stack is warmed up when the temperature of the fuel cell stack is below freezing point. Patent Document 1 also describes that in a low-temperature environment, the charge capacity of the battery tends to decrease, leading to an overcharged state and causing the battery to deteriorate. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Patent Publication No. 2021-190305 Summary of the Invention [Problem to be solved by the invention]

[0005] There is a need for a better control device, fuel cell system, and control method and program for a fuel cell system.

[0006] The present invention aims to solve the above-mentioned problems. [Means for solving the problem]

[0007] A first aspect of the present invention is a control device for controlling a fuel cell system including a fuel cell that generates electricity by an electrochemical reaction between a fuel gas and an oxidant gas, and a battery that can charge the electricity generated by the fuel cell, the control device having a valve for controlling an oxidant gas flow rate, which is the flow rate of the oxidant gas supplied to the fuel cell, and the control unit is capable of performing the following steps: a start-up step for starting the fuel cell by supplying the fuel gas to the fuel cell and controlling the valve to supply the oxidant gas at a first flow rate to the fuel cell; a warm-up preparation step for preparing to warm up the fuel cell after the start-up step by controlling the valve to set the oxidant gas flow rate to a second flow rate smaller than the first flow rate; and a warm-up step for warming up the fuel cell after the warm-up preparation step, while supplying the oxidant gas to the fuel cell at a third flow rate greater than the second flow rate.

[0008] A second aspect of the present invention is a fuel cell system including the above-mentioned control device.

[0009] A third aspect of the present invention is a control method for a fuel cell system including a fuel cell that generates electricity by an electrochemical reaction between a fuel gas and an oxidant gas, a battery that can charge the electricity generated by the fuel cell, and a control unit that controls a valve for adjusting the oxidant gas flow rate, which is the flow rate of the oxidant gas supplied to the fuel cell, the control method including: a start-up step of starting the fuel cell by supplying the fuel gas to the fuel cell and the control unit controlling the valve to supply the oxidant gas at a first flow rate to the fuel cell; a warm-up preparation step of preparing for warming up the fuel cell after the start-up step by controlling the valve to set the oxidant gas flow rate to a second flow rate smaller than the first flow rate; and a warm-up step of warming up the fuel cell after the warm-up preparation step while supplying the oxidant gas at a third flow rate greater than the second flow rate to the fuel cell.

[0010] A fourth aspect of the present invention is a program for causing a computer to execute the above-mentioned fuel cell system control method. Effect of the Invention

[0011] According to the present invention, it is possible to obtain a better control device, a fuel cell system, a control method for a fuel cell system, and a program. [Brief description of the drawings]

[0012] [Figure 1] FIG. 1 is a schematic diagram showing the configuration of a fuel cell system according to one embodiment of the present invention. [Diagram 2] FIG. 2 is a flowchart illustrating an example of a control method for the fuel cell system. [Diagram 3] FIG. 3 is a timing chart for explaining an example of a control method for the fuel cell system. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0013] When warming up a fuel cell stack in a fuel cell system, a warm-up preparation step is performed after the start-up process of the fuel cell stack is completed, in which the output voltage of the fuel cell stack is reduced to a predetermined warm-up voltage. In this warm-up preparation step, the fuel cell stack generates power, and the power generated by the fuel cell stack is charged to the battery. However, if the battery has a sufficient remaining capacity, there is a risk that the battery will be overcharged if the power generated by the fuel cell stack is charged to the battery in the warm-up preparation step. In particular, in a low-temperature environment, the charge capacity of the battery tends to be small, so that the battery is likely to be overcharged if the power generated by the fuel cell stack is charged to the battery in the warm-up preparation step. An object of the present disclosure is to effectively prevent the battery from being overcharged when warming up the fuel cell stack.

[0014] A control device 10, a fuel cell system 12, a control method for the fuel cell system 12, and a program according to one embodiment of the present invention will be described below with reference to the drawings. Fig. 1 is a schematic diagram showing the configuration of a fuel cell system 12 according to this embodiment. The fuel cell system 12 is mounted on a fuel cell vehicle (not shown), such as a fuel cell electric vehicle. Note that the fuel cell system 12 may also be mounted on equipment other than a vehicle.

[0015] As shown in FIG. 1, a fuel cell system 12 according to this embodiment includes a fuel cell stack (fuel cell) 14, a cathode system device 16, an anode system device 18, a power supply system 19, and a control device 10.

[0016] The fuel cell stack 14 generates power through an electrochemical reaction between a fuel gas and an oxidant gas. The fuel gas is, for example, hydrogen gas. The fuel gas is not particularly limited as long as it is a gas containing hydrogen. The oxidant gas is, for example, air. The oxidant gas is not limited to air as long as it is a gas containing oxygen. The fuel cell stack 14 is formed by stacking a plurality of power generation cells 20. Each power generation cell 20 has a membrane electrode assembly (MEA) 22 and a pair of separators 24a, 24b that sandwich the membrane electrode assembly 22.

[0017] The membrane electrode assembly 22 includes an electrolyte membrane 26, a cathode electrode 28, and an anode electrode 30. The electrolyte membrane 26 is sandwiched between the cathode electrode 28 and the anode electrode 30. The electrolyte membrane 26 is, for example, a solid polymer electrolyte membrane. The solid polymer electrolyte membrane is, for example, a thin film of perfluorosulfonic acid containing moisture. Although not shown in detail, each of the cathode electrode 28 and the anode electrode 30 includes an electrode catalyst layer bonded to the electrolyte membrane 26 and a gas diffusion layer laminated on the electrode catalyst layer.

[0018] One of the separators, 24a, has an oxidant gas flow path 32 formed on its surface facing the membrane electrode assembly 22. The oxidant gas flow path 32 communicates with an oxidant gas inlet port 34 and an oxidant gas outlet port 36 of the fuel cell stack 14. The other separator, 24b, has a fuel gas flow path 38 formed on its surface facing the membrane electrode assembly 22. The fuel gas flow path 38 communicates with a fuel gas inlet port 40 and a fuel gas outlet port 42 of the fuel cell stack 14. The fuel cell stack 14 may also have components other than those described above, but descriptions of these will be omitted here.

[0019] The cathode system 16 has an oxidant gas supply unit 44, an oxidant gas supply passage 46, an oxidant gas discharge passage 48, a bypass passage 50, and a valve 52. The cathode system 16 may also include components other than these components, but the description thereof will be omitted here.

[0020] The oxidizing gas supply unit 44 supplies the oxidizing gas to the oxidizing gas supply flow path 46. Examples of the oxidizing gas supply unit 44 include an air pump or an air compressor. The oxidizing gas supply flow path 46 is connected to the oxidizing gas inlet portion 34 of the fuel cell stack 14. The oxidizing gas supply flow path 46 supplies the oxidizing gas to the fuel cell stack 14.

[0021] The oxidizing gas discharge flow path 48 is connected to the oxidizing gas outlet portion 36 of the fuel cell stack 14. The oxidizing gas discharge flow path 48 passes through the oxidizing gas exhaust gas discharged from the fuel cell stack 14. The oxidizing gas discharge flow path 48 discharges the oxidizing gas exhaust gas to the outside of the fuel cell system 12.

[0022] The bypass flow path 50 connects the oxidant gas supply flow path 46 and the oxidant gas discharge flow path 48 to each other. The valve 52 is an on-off valve whose opening degree can be adjusted. The valve 52 adjusts the flow rate of the oxidant gas supplied to the fuel cell stack 14. The valve 52 includes a supply valve 54, a discharge valve 56, and a bypass valve 58.

[0023] The supply valve 54 is provided in the oxidant gas supply channel 46. The supply valve 54 opens and closes the oxidant gas supply channel 46. The supply valve 54 is configured to be able to adjust the opening degree. An example of the supply valve 54 is a butterfly valve, but is not limited to this. The oxidant gas supply channel 46 includes an upstream supply channel 46a, which is a portion upstream of the supply valve 54, and a downstream supply channel 46b, which is a portion downstream of the supply valve 54. The upstream supply channel 46a connects the oxidant gas supply unit 44 and the supply valve 54. The downstream supply channel 46b connects the supply valve 54 and the oxidant gas inlet portion 34.

[0024] The exhaust valve 56 is provided in the oxidant gas exhaust flow path 48. The exhaust valve 56 opens and closes the oxidant gas exhaust flow path 48. The exhaust valve 56 is configured to be able to adjust the opening degree. An example of the exhaust valve 56 is a butterfly valve, but is not limited to this. The oxidant gas exhaust flow path 48 includes an upstream exhaust flow path 48a, which is a portion upstream of the exhaust valve 56, and a downstream exhaust flow path 48b, which is a portion downstream of the exhaust valve 56. The upstream exhaust flow path 48a connects the oxidant gas outlet portion 36 and the exhaust valve 56. The downstream exhaust flow path 48b is connected to the exhaust valve 56.

[0025] One end of the bypass flow passage 50 is connected to the upstream supply flow passage 46a. The other end of the bypass flow passage 50 is connected to the downstream discharge flow passage 48b. A bypass valve 58 is provided in the bypass flow passage 50. The bypass valve 58 opens and closes the bypass flow passage 50. The bypass valve 58 is configured so that the opening degree can be adjusted. An example of the bypass valve 58 is a butterfly valve, but is not limited to this.

[0026] The anode system device 18 has a fuel gas supply unit 60, a fuel gas supply passage 62, a fuel gas discharge passage 64, a gas-liquid separator 66, a circulation passage 68, a drain passage 70, and a drain valve 72. The anode system device 18 may also be provided with components other than these components, but the description thereof will be omitted here.

[0027] The fuel gas supply unit 60 supplies fuel gas to a fuel gas supply passage 62. The fuel gas supply unit 60 includes an injector and an ejector (not shown). The fuel gas supply passage 62 connects the fuel gas supply unit 60 to the fuel gas inlet portion 40 of the fuel cell stack 14. The fuel gas supply passage 62 supplies the fuel gas to the fuel cell stack 14.

[0028] Fuel exhaust gas discharged from the fuel cell stack 14 flows through the fuel gas discharge flow path 64. The fuel exhaust gas contains product water generated by the power generation of the fuel cell stack 14. The gas-liquid separator 66 is provided in the fuel gas discharge flow path 64. The gas-liquid separator 66 separates the fuel exhaust gas into gas and liquid. The gas-liquid separator 66 can store liquid water separated from the fuel exhaust gas. The circulation flow path 68 guides the fuel exhaust gas that has flowed through the gas-liquid separator 66 to an ejector (not shown) of the fuel gas supply unit 60. The fuel exhaust gas flowing through the circulation flow path 68 is reused as fuel gas by flowing into the fuel gas supply flow path 62 via the ejector.

[0029] The drain flow path 70 connects the gas-liquid separator 66 and the downstream discharge flow path 48b. The drain flow path 70 guides the liquid water stored in the gas-liquid separator 66 to the downstream discharge flow path 48b together with the fuel exhaust gas. The fuel exhaust gas flowing through the drain flow path 70 is diluted by the oxidant exhaust gas flowing through the downstream discharge flow path 48b and discharged to the outside of the fuel cell system 12. A drain valve 72 is provided in the drain flow path 70. The drain valve 72 opens and closes the drain flow path 70.

[0030] The fuel cell system 12 includes a cooling system (not shown). The cooling system circulates a cooling medium through the fuel cell stack 14. Examples of the cooling medium include pure water, ethylene glycol, and oil.

[0031] The power supply system 19 has a battery 74 and a DC / DC converter 76. The battery 74 is charged with power generated by the fuel cell stack 14. The battery 74 can supply power to an electric load 78. The electric load 78 is not particularly limited, but includes, for example, a drive unit having an inverter, a motor, etc. for moving the fuel cell vehicle, an oxidant gas supply unit 44, a fuel gas supply unit 60, an air conditioning unit, etc. Types of the battery 74 include a lead-acid battery and a lithium-ion secondary battery, etc.

[0032] The DC / DC converter 76 can step up the output voltage (generated voltage) of the fuel cell stack 14. The DC / DC converter 76 can also step down the output voltage of the fuel cell stack 14.

[0033] A temperature sensor 80 and a voltage sensor 82 are connected to the control device 10. Sensors other than the temperature sensor 80 and the voltage sensor 82 may be connected to the control device 10. The temperature sensor 80 sequentially measures a temperature corresponding to the temperature of the fuel cell stack 14. Specifically, the temperature sensor 80 sequentially measures, for example, the temperature of the cooling medium circulating within the fuel cell stack 14. The voltage sensor 82 sequentially measures the output voltage of the fuel cell stack 14.

[0034] The control device 10 includes a calculation unit 84 and a storage unit 86. The calculation unit 84 is configured by a processor such as a CPU (Central Processing Unit) or a GPU (Graphics Processing Unit). That is, the calculation unit 84 is configured by a processing circuitry.

[0035] The calculation unit 84 has a control unit 88, an acquisition unit 90, and a determination unit 92. The control unit 88, the acquisition unit 90, and the determination unit 92 can be realized by the calculation unit 84 executing a program stored in the storage unit 86.

[0036] At least a part of the control unit 88, the acquisition unit 90, and the determination unit 92 may be realized by an integrated circuit such as an ASIC (Application Specific Integrated Circuit), an FPGA (Field-Programmable Gate Array), etc. At least a part of the control unit 88, the acquisition unit 90, and the determination unit 92 may be configured by an electronic circuit including a discrete device.

[0037] The storage unit 86 is composed of a volatile memory (not shown) and a non-volatile memory (not shown). An example of the volatile memory is a random access memory (RAM). The volatile memory is used as a working memory of the processor, and temporarily stores data and the like required for processing or calculation. An example of the non-volatile memory is a read only memory (ROM) or a flash memory. The non-volatile memory is used as a storage memory, and stores programs, tables, maps, and the like. At least a part of the storage unit 86 may be provided in the processor, integrated circuit, and the like described above.

[0038] The control unit 88 is responsible for overall control of the fuel cell system 12. The control unit 88 controls the fuel gas supply unit 60 and the oxidant gas supply unit 44. The control unit 88 controls the supply valve 54, the exhaust valve 56, and the bypass valve 58. The control unit 88 controls the DC / DC converter 76. The acquisition unit 90 can grasp the temperature of the fuel cell stack 14 based on a signal supplied from the temperature sensor 80. The acquisition unit 90 can grasp the output voltage of the fuel cell stack 14 based on a signal supplied from the voltage sensor 82.

[0039] Next, an example of a method for controlling the fuel cell system 12 according to this embodiment will be described.

[0040] In the initial state of FIG. 2, the fuel cell stack 14 is stopped. If oxygen remains in the oxidant gas flow passage 32 of the power generation cell 20 while the fuel cell stack 14 is stopped, the electrode catalyst layer may deteriorate. Therefore, while the fuel cell stack 14 is stopped, the fuel gas is supplied to the oxidant gas flow passage 32. As a result, the oxygen remaining in the oxidant gas flow passage 32 reacts with hydrogen in the fuel gas, and the oxygen concentration in the oxidant gas flow passage 32 decreases. That is, when the fuel cell stack 14 is started, the oxygen concentration in the oxidant gas flow passage 32 is low. While the fuel cell stack 14 is stopped, the supply valve 54 and the exhaust valve 56 are each fully closed to prevent the inflow of the oxidant gas into the oxidant gas flow passage 32. In addition, the bypass valve 58 is fully open. In addition, by supplying fuel gas to the fuel gas flow path 38 while suppressing the flow of oxidant gas into the oxidant gas flow path 32, oxygen consumption control may be performed to consume the oxygen remaining in the oxidant gas flow path 32, thereby reducing the oxygen concentration in the oxidant gas flow path 32 at the time the fuel cell stack 14 is started.

[0041] In step S1, the controller 10 receives a start-up command for the fuel cell stack 14. Specifically, for example, when a user turns on a power switch (not shown), the start-up command is supplied from the power switch to the controller 10. The acquisition unit 90 can grasp the start-up command based on the signal supplied from the power switch. Then, the process proceeds to step S2. That is, the start-up steps (steps S2 to S5) are performed.

[0042] In step S2, the control unit 88 controls the fuel gas supply unit 60 to supply fuel gas from the fuel gas supply unit 60 to the fuel gas supply flow path 62. The fuel gas supplied to the fuel gas supply flow path 62 is guided to the fuel gas flow path 38 of the fuel cell stack 14. Then, the process proceeds to step S3.

[0043] In step S3, the control unit 88 controls the oxidant gas supply unit 44 to send the oxidant gas from the oxidant gas supply unit 44 to the upstream supply flow path 46a. At this stage, the supply valve 54 is closed, so the oxidant gas has not yet flowed into the fuel cell stack 14. Then, the process proceeds to step S4. Step S3 may be performed at the same time as step S2, or may be performed prior to step S2.

[0044] In step S4, the control unit 88 controls the valve 52 to supply the oxidant gas at the first flow rate Q1 to the fuel cell stack 14. Specifically, the control unit 88 opens each of the supply valve 54, the discharge valve 56, and the bypass valve 58. The oxidant gas supplied from the oxidant gas supply unit 44 to the upstream supply flow passage 46a flows through the supply valve 54 to the downstream supply flow passage 46b and also flows to the bypass flow passage 50. The oxidant gas that flows to the downstream supply flow passage 46b is guided to the oxidant gas flow passage 32 of the fuel cell stack 14. As a result, the fuel gas sealed in the oxidant gas flow passage 32 is discharged to the oxidant gas discharge flow passage 48 by the oxidant gas. The fuel gas guided to the oxidant gas discharge flow passage 48 is diluted with the oxidant gas guided from the bypass flow passage 50 and is discharged to the outside of the fuel cell system 12.

[0045] The fuel cell stack 14 generates power through an electrochemical reaction between the fuel gas and the oxidant gas. The output voltage of the fuel cell stack 14 is boosted by a DC / DC converter 76. The power generated by the fuel cell stack 14 is charged into a battery 74. The power generated by the fuel cell stack 14 can also be used to drive each of the oxidant gas supply unit 44 and the fuel gas supply unit 60.

[0046] The fuel cell stack 14 discharges the fuel exhaust gas from the fuel gas flow path 38 to the fuel gas discharge flow path 64, and discharges the oxidant exhaust gas from the oxidant gas flow path 32 to the upstream discharge flow path 48a. The fuel exhaust gas contains water generated by power generation. The fuel exhaust gas discharged to the fuel gas discharge flow path 64 is guided to the gas-liquid separator 66. The gas-liquid separator 66 separates the fuel exhaust gas into gas and liquid. The fuel exhaust gas guided from the gas-liquid separator 66 to the circulation flow path 68 is returned to the fuel gas supply unit 60 and reused. The liquid water separated from the fuel exhaust gas in the gas-liquid separator 66 is stored in the gas-liquid separator 66.

[0047] The oxidant exhaust gas discharged to the upstream discharge flow passage 48a is guided to the downstream discharge flow passage 48b via the discharge valve 56. The oxidant exhaust gas guided to the downstream discharge flow passage 48b is mixed with the oxidant gas guided from the bypass flow passage 50 and is exhausted to the outside of the fuel cell system 12.

[0048] When the control unit 88 opens the drain valve 72, the liquid water stored in the gas-liquid separator 66 is discharged together with the fuel exhaust gas via the drain passage 70 and the downstream discharge passage 48b to the outside of the fuel cell system 12. The fuel exhaust gas guided from the drain passage 70 to the downstream discharge passage 48b is discharged to the outside of the fuel cell system 12 in a state where it is diluted with the oxidant gas and the oxidant exhaust gas.

[0049] The oxidant gas flow rate, which is the flow rate of the oxidant gas supplied to the fuel cell stack 14, can be set by adjusting the apertures of the supply valve 54, the exhaust valve 56, and the bypass valve 58. Hereinafter, the flow rate of the oxidant gas supplied to the fuel cell stack 14 may be simply referred to as the "oxidant gas flow rate." In step S4, the control unit 88 sets the apertures of the supply valve 54, the exhaust valve 56, and the bypass valve 58 to predetermined apertures, thereby supplying the oxidant gas at a first flow rate Q1 to the fuel cell stack 14. After step S4, the process proceeds to step S5.

[0050] In step S5, the determination unit 92 determines whether the startup process of the fuel cell stack 14 has been completed. Specifically, the determination unit 92 determines, for example, whether the output voltage of the fuel cell stack 14 has reached a predetermined startup voltage V1. The output voltage of the fuel cell stack 14 is acquired by the acquisition unit 90. If the output voltage of the fuel cell stack 14 is lower than the startup voltage V1 (see FIG. 3), the determination unit 92 determines that the startup process of the fuel cell stack 14 has not been completed. If the output voltage of the fuel cell stack 14 has reached the startup voltage V1, the determination unit 92 determines that the startup process of the fuel cell stack 14 has been completed. The determination unit 92 may determine whether the startup process of the fuel cell stack 14 has been completed based on the time that has elapsed since performing step S4.

[0051] If the determination unit 92 determines that the startup process of the fuel cell stack 14 is not complete (NO in step S5), step S5 is repeated. If the determination unit 92 determines that the startup process of the fuel cell stack 14 is complete (YES in step S5), the process proceeds to step S6.

[0052] In step S6, the determination unit 92 determines whether or not warming up of the fuel cell stack 14 is necessary. Specifically, the determination unit 92 determines, for example, whether or not the temperature of the fuel cell stack 14 is equal to or lower than a predetermined first temperature threshold. The temperature of the fuel cell stack 14 is acquired by the acquisition unit 90. The first temperature threshold may be set to, for example, freezing point (0°C). The first temperature threshold can be set appropriately and may be higher or lower than freezing point. The determination unit 92 determines that warming up of the fuel cell stack 14 is not necessary when the temperature of the fuel cell stack 14 is higher than the first temperature threshold. The determination unit 92 determines that warming up of the fuel cell stack 14 is necessary when the temperature of the fuel cell stack 14 is equal to or lower than the first temperature threshold.

[0053] If the determination unit 92 determines that the fuel cell stack 14 does not need to be warmed up (NO in step S6), the process proceeds to step S13. If the determination unit 92 determines that the fuel cell stack 14 needs to be warmed up (YES in step S6), the process proceeds to step S7. That is, the warm-up preparation steps (steps S7 to S10) are performed.

[0054] In step S7, the control unit 88 controls the valve 52 to set the oxidant gas flow rate to a second flow rate Q2 that is smaller than the first flow rate Q1. Specifically, the control unit 88 closes the supply valve 54 to a predetermined supply suppression opening degree, and closes the exhaust valve 56 to a predetermined exhaust suppression opening degree. This reduces the oxidant gas flow rate from the first flow rate Q1 to the second flow rate Q2. Therefore, the amount of power generated by the fuel cell stack 14 decreases. When the amount of power generated by the fuel cell stack 14 decreases, the output voltage of the fuel cell stack 14 drops. Then, the process proceeds to step S8.

[0055] In step S8, the determination unit 92 determines whether or not it is expected that preparation for warming up the fuel cell stack 14 will be completed. Specifically, the determination unit 92 determines, for example, whether or not the output voltage of the fuel cell stack 14 has become equal to or lower than a predetermined voltage threshold V2 (see FIG. 3). The voltage threshold V2 is a voltage higher than the warm-up voltage V3. If the output voltage of the fuel cell stack 14 is higher than the voltage threshold V2, the determination unit 92 determines that it is not expected that preparation for warming up the fuel cell stack 14 will be completed. If the output voltage of the fuel cell stack 14 has dropped to the voltage threshold V2, the determination unit 92 determines that it is expected that preparation for warming up the fuel cell stack 14 will be completed. The determination unit 92 may determine whether or not it is expected that preparation for warming up the fuel cell stack 14 will be completed based on the elapsed time since the start of execution of step S7.

[0056] If the determination unit 92 determines that the preparation for warming up the fuel cell stack 14 is not expected to be completed (NO in step S8), step S8 is repeated. If the determination unit 92 determines that the preparation for warming up the fuel cell stack 14 is expected to be completed (YES in step S8), the process proceeds to step S9.

[0057] In step S9, the control unit 88 controls the valve 52 to set the oxidant gas flow rate to a third flow rate Q3 that is greater than the second flow rate Q2. Specifically, the control unit 88 opens the supply valve 54 to a predetermined warm-up supply opening degree, and opens the exhaust valve 56 to a predetermined warm-up exhaust opening degree. This allows the oxidant gas flow rate to be increased from the second flow rate Q2 to the third flow rate Q3. Then, the process proceeds to step S10.

[0058] In step S10, the determination unit 92 determines whether or not preparation for warming up the fuel cell stack 14 has been completed. Specifically, the determination unit 92 determines whether or not the output voltage of the fuel cell stack 14 has dropped to a warm-up voltage V3 (see FIG. 3). If the output voltage of the fuel cell stack 14 is higher than the warm-up voltage V3, the determination unit 92 determines that preparation for warming up the fuel cell stack 14 has not yet been completed. If the output voltage of the fuel cell stack 14 has dropped to the warm-up voltage V3, the determination unit 92 determines that preparation for warming up the fuel cell stack 14 has been completed. The determination unit 92 may determine whether or not preparation for warming up the fuel cell stack 14 has been completed based on the elapsed time since the start of the implementation of step S9.

[0059] If the determination unit 92 determines that the fuel cell stack 14 is not ready to warm up (NO in step S10), step S10 is repeated. If the determination unit 92 determines that the fuel cell stack 14 is ready to warm up (YES in step S10), the process proceeds to step S11. That is, the warm-up steps (steps S11 and S12) are performed.

[0060] In step S11, the control unit 88 warms up the fuel cell stack 14. Specifically, the control unit 88 controls the valve 52 to maintain the oxidant gas flow rate at the third flow rate Q3 so that the output voltage of the fuel cell stack 14 is maintained at the warm-up voltage V3. This allows the stoichiometric ratio of the oxidant gas supplied to the power generation cells 20 to be a predetermined stoichiometric ratio for warm-up. The stoichiometric ratio for warm-up is smaller than the stoichiometric ratio during normal operation of the fuel cell stack 14. Note that the normal operation of the fuel cell stack 14 refers to operation of the fuel cell stack 14 in a state in which the fuel cell stack 14 is not warmed up. During normal operation of the fuel cell stack 14, the stoichiometric ratio of the oxidant gas supplied to the power generation cells 20 is made relatively large to reduce heat loss in the fuel cell stack 14.

[0061] By setting the stoichiometric ratio of the oxidant gas supplied to the power generation cell 20 to the warm-up stoichiometric ratio, low-efficiency power generation can be performed in the fuel cell stack 14. This increases the amount of heat generated (heat loss) in the fuel cell stack 14, facilitating the warm-up of the fuel cell stack 14. After step S11, the process proceeds to step S12.

[0062] In step S12, the determination unit 92 determines whether or not the warm-up of the fuel cell stack 14 has been completed. Specifically, the determination unit 92 determines whether or not the temperature of the fuel cell stack 14 has become equal to or higher than a predetermined second temperature threshold. The temperature of the fuel cell stack 14 is acquired by the acquisition unit 90. If the temperature of the fuel cell stack 14 is lower than the second temperature threshold, the determination unit 92 determines that the warm-up of the fuel cell stack 14 has not yet been completed. If the temperature of the fuel cell stack 14 has risen to the second temperature threshold, the determination unit 92 determines that the warm-up of the fuel cell stack 14 has been completed. Note that the determination unit 92 may determine whether or not the warm-up of the fuel cell stack 14 has been completed based on the elapsed time since the start of the warm-up in step S11.

[0063] If the determination unit 92 determines that the warm-up of the fuel cell stack 14 is not complete (NO in step S12), step S12 is repeated. If the determination unit 92 determines that the warm-up of the fuel cell stack 14 is complete (YES in step S12), the process proceeds to step S13.

[0064] In step S13, the control unit 88 performs normal operation of the fuel cell stack 14. Specifically, the control unit 88 controls the current of the fuel cell stack 14 based on the power required for the fuel cell stack 14. In this way, the process shown in FIG. 2 is completed.

[0065] Fig. 3 is a timing chart for explaining an example of a control method for the fuel cell system 12. Specifically, Fig. 3 shows a timing chart for starting up the fuel cell stack 14 when the temperature of the fuel cell stack 14 is below the freezing point.

[0066] 3, the control unit 88 sequentially performs a startup step, a warm-up preparation step, and a warm-up step. The control unit 88 also controls the voltage of the fuel cell stack 14 so that the output voltage of the fuel cell stack 14 conforms to a predetermined voltage command from the start of the startup step until the completion of the warm-up step. Furthermore, the control unit 88 drives the oxidant gas supply unit 44 and the fuel gas supply unit 60 from the start of the startup step until the completion of the warm-up step.

[0067] In the startup step, it is confirmed whether the output voltage of the fuel cell stack 14 can be increased to a predetermined startup voltage V1 to operate the fuel cell stack 14 without any problems. The startup step is initiated by receiving a startup command for the fuel cell stack 14 at time t1. At time t1, the control unit 88 controls the oxidant gas supply unit 44 to supply oxidant gas to the upstream supply flow path 46a. In the initial state of the fuel cell stack 14, the bypass valve 58 is fully open. Also, at time t1, the control unit 88 controls the fuel gas supply unit 60 to supply fuel gas to the fuel cell stack 14.

[0068] At time t2, the control unit 88 opens each of the supply valve 54 and the exhaust valve 56, for example, by outputting a full-open command to each of the supply valve 54 and the exhaust valve 56. When the control unit 88 opens the supply valve 54, the oxidant gas is supplied to the fuel cell stack 14. When the control unit 88 opens the exhaust valve 56, the fuel gas sealed in the oxidant gas flow path 32 of the fuel cell stack 14 is exhausted from the fuel cell stack 14. This makes it possible to check the operation of the supply valve 54 and the exhaust valve 56. Even if frozen matter adheres to the valve bodies of the supply valve 54 and the exhaust valve 56 at low temperatures, the frozen matter can be destroyed by the valve opening operation.

[0069] When the oxidant gas is supplied to the fuel cell stack 14, the fuel cell stack 14 starts generating electricity through an electrochemical reaction between the fuel gas and the oxidant gas. When the fuel cell stack 14 starts generating electricity, the output voltage of the fuel cell stack 14 increases. Note that in Fig. 3, a voltage command is shown, but the actual output voltage of the fuel cell stack 14 is not shown.

[0070] The oxidant gas flow rate, which is the flow rate supplied to the fuel cell stack 14, increases as the opening of the supply valve 54 increases. In this embodiment, at time t3, the output voltage of the fuel cell stack 14 increases to a startup voltage V1. Here, the output voltage of the fuel cell stack 14 is an open circuit voltage (OCV). The oxidant gas flow rate when the output voltage of the fuel cell stack 14 reaches the startup voltage V1 is a first flow rate Q1. At time t3, the startup step is completed.

[0071] The warm-up preparation step is started at time t3. In order to warm up the fuel cell stack 14 by low-efficiency power generation, it is necessary to reduce the output voltage of the fuel cell stack 14 to the warm-up voltage V3. Therefore, in the warm-up preparation step, the output voltage of the fuel cell stack 14 is reduced to the warm-up voltage V3.

[0072] Specifically, in the warm-up preparation step, at time t3, the control unit 88 closes the supply valve 54 to the supply suppression opening degree, and closes the exhaust valve 56 to the exhaust suppression opening degree. As a result, at time t4, the oxidant gas flow rate decreases to the second flow rate Q2. In the example of FIG. 3, each of the supply suppression opening degree and the exhaust suppression opening degree is set to an opening degree larger than 0 degrees (the opening degree in the fully closed state) so that the oxidant gas flow rate is maintained at the second flow rate Q2. Note that each of the supply suppression opening degree and the exhaust suppression opening degree may be set to 0 degrees, for example. In this case, the oxidant gas flow rate becomes 0.

[0073] When the oxidant gas flow rate decreases to the second flow rate Q2, the fuel cell stack 14 generates power while consuming the oxidant gas remaining in the fuel gas flow path 38. Therefore, in the warm-up preparation step, the amount of power generated by the fuel cell stack 14 can be reduced. This allows the output voltage of the fuel cell stack 14 to be reduced.

[0074] In the warm-up preparation step, the electric power generated by the fuel cell stack 14 may be supplied to the battery 74. The lower the temperature of the battery 74, the smaller the charge capacity of the battery 74. Therefore, in the warm-up preparation step, the battery 74 is likely to be overcharged. However, since the amount of electric power generated by the fuel cell stack 14 is suppressed in the warm-up preparation step, the electric power supplied to the battery 74 can be reduced. Thus, overcharging of the battery 74 can be suppressed. Furthermore, since the control unit 88 drives the oxidant gas supply unit 44 and the fuel gas supply unit 60 during the warm-up preparation step, the electric power generated by the fuel cell stack 14 is consumed by the oxidant gas supply unit 44 and the fuel gas supply unit 60. Thus, overcharging of the battery 74 can be further suppressed. Note that, since the bypass valve 58 is opened in the warm-up preparation step, the oxidant gas supplied from the oxidant gas supply unit 44 to the upstream supply flow path 46a can be released to the downstream discharge flow path 48b via the bypass flow path 50.

[0075] In the warm-up preparation step, the control unit 88 controls the DC / DC converter 76 to reduce the output voltage of the fuel cell stack 14 at a predetermined rate. The battery 74 is prone to degradation when it is quickly charged at low temperatures. Therefore, the rate at which the output voltage of the fuel cell stack 14 is reduced is set to a magnitude that can prevent the battery 74 from deteriorating.

[0076] At time t5, when the output voltage of the fuel cell stack 14 drops to a predetermined voltage threshold V2, the control unit 88 opens each of the supply valve 54 and the exhaust valve 56 to increase the oxidant gas flow rate to a third flow rate Q3. Specifically, the control unit 88 opens the supply valve 54 to the full open position, and opens the exhaust valve 56 to an opening degree smaller than the full open position. The opening degrees of each of the supply valve 54 and the exhaust valve 56 can be set appropriately. Also, at time t5, the control unit 88 closes the bypass valve 58 to a predetermined opening degree. As a result, the oxidant gas flow rate increases to the third flow rate Q3.

[0077] This allows a smooth transition from the warm-up preparation step to the warm-up step at time t6 when the output voltage of the fuel cell stack 14 drops to the warm-up voltage V3 (when the warm-up preparation step ends).

[0078] The warm-up step is started at time t6. In the warm-up step, the control unit 88 maintains the output voltage of the fuel cell stack 14 at the warm-up voltage V3 by feedback-controlling the opening degree of the bypass valve 58. This makes it possible to warm up the fuel cell stack 14 by low-efficiency power generation. In this embodiment, in the warm-up step, the opening degrees of the supply valve 54 and the discharge valve 56 are set to constant values, but the output voltage of the fuel cell stack 14 may be maintained at the warm-up voltage V3 by feedback-controlling the opening degrees of the supply valve 54 and the discharge valve 56.

[0079] At time t7, when it is expected that the warm-up of the fuel cell stack 14 will be completed, the control unit 88 outputs a command for a voltage higher than the warm-up voltage V3. This allows a smooth transition from the warm-up step to normal operation of the fuel cell stack 14 when the warm-up operation ends at time t8 (at time t8).

[0080] According to this embodiment, in the warm-up preparation step, the control unit 88 controls the valve 52 to set the oxidant gas flow rate to the second flow rate Q2 which is smaller than the first flow rate Q1, thereby reducing the power generated by the fuel cell stack 14. This reduces the power charged from the fuel cell stack 14 to the battery 74 in the warm-up preparation step, thereby preventing overcharging of the battery 74. Therefore, it is possible to obtain a better control device 10, fuel cell system 12, and a control method and program for the fuel cell system 12.

[0081] In addition to the above disclosure, the following notes are also disclosed.

[0082] (Appendix 1) The control device (10) is a control device that controls a fuel cell system (12) including a fuel cell (14) that generates electricity by an electrochemical reaction between a fuel gas and an oxidant gas, and a battery (74) that can charge the electricity generated by the fuel cell, and has a control unit (88) that controls a valve (52) for adjusting the oxidant gas flow rate, which is the flow rate of the oxidant gas supplied to the fuel cell, and the control unit is capable of performing a start-up step of starting the fuel cell by supplying the fuel gas to the fuel cell and controlling the valve to supply the oxidant gas at a first flow rate (Q1) to the fuel cell, a warm-up preparation step of preparing for warming up the fuel cell after the start-up step by controlling the valve to set the oxidant gas flow rate to a second flow rate (Q2) smaller than the first flow rate, and a warm-up step of warming up the fuel cell after the warm-up preparation step, while supplying the oxidant gas to the fuel cell at a third flow rate (Q3) larger than the second flow rate.

[0083] According to this configuration, in the warm-up preparation step, the control unit controls the valve to set the oxidant gas flow rate to a second flow rate that is smaller than the first flow rate, thereby reducing the power generated by the fuel cell stack. This reduces the power charged from the fuel cell stack to the battery in the warm-up preparation step, thereby preventing overcharging of the battery. Therefore, a better control device can be obtained.

[0084] (Appendix 2) In the control device described in Appendix 1, in the warm-up preparation step, when the output voltage of the fuel cell drops to a predetermined voltage threshold (V2), the control unit may control the valve to set the oxidant gas flow rate from the second flow rate to the third flow rate.

[0085] According to this configuration, a smooth transition from the warm-up preparation step to the warm-up step can be achieved.

[0086] (Appendix 3) In the control device described in Supplementary Note 1 or 2, the valve may include a supply valve (54) provided in an oxidant gas supply passage (46) for supplying the oxidant gas to the fuel cell, and in the start-up step, the control unit may open the supply valve, and when setting the oxidant gas flow rate from the first flow rate to the second flow rate in the warm-up preparation step, the control unit may close the supply valve to a predetermined supply suppression opening degree.

[0087] According to this configuration, in the warm-up preparation step, the oxidant gas flow rate can be made smaller than the first flow rate.

[0088] (Appendix 4) In the control device described in Appendix 3, the valve may include an exhaust valve (56) provided in an oxidant gas exhaust passage (48) through which oxidant exhaust gas discharged from the fuel cell flows, and in the start-up step, the control unit may open the exhaust valve.

[0089] With this configuration, even if fuel gas is sealed in the oxidant gas flow path of the fuel cell while the fuel cell is stopped operating, the fuel gas present in the oxidant gas flow path can be smoothly discharged.

[0090] (Appendix 5) In the control device described in Supplementary Note 4, when the oxidant gas flow rate is set from the first flow rate to the second flow rate in the warm-up preparation step, the control unit may close the exhaust valve to a predetermined exhaust suppression opening degree.

[0091] With this configuration, it is possible to prevent the oxidant gas flow rate from becoming smaller than the second flow rate.

[0092] (Appendix 6) In the control device described in Appendix 4 or 5, the valve may include a bypass valve (58) provided in a bypass flow path (50) connecting the oxidant gas supply flow path and the oxidant gas discharge flow path, one end of the bypass flow path is connected to a portion (46a) of the oxidant gas supply flow path upstream of the supply valve and the other end of the bypass flow path is connected to a portion (48b) of the oxidant gas discharge flow path downstream of the discharge valve, and in the warm-up preparation step, the control unit may maintain the bypass valve in an open state.

[0093] According to this configuration, in the warm-up preparation step, while the oxidant gas supply unit for supplying the oxidant gas to the oxidant gas supply channel is driven, the oxidant gas flow rate can be reduced from the first flow rate to the second flow rate. In this case, the power generated by the fuel cell can be consumed by the oxidant gas supply unit, thereby further suppressing overcharging of the battery.

[0094] (Appendix 7) The fuel cell system includes the control device according to any one of claims 1 to 6.

[0095] (Appendix 8) A control method for a fuel cell system includes a fuel cell that generates electricity through an electrochemical reaction between a fuel gas and an oxidant gas, a battery that can charge the electricity generated by the fuel cell, and a control unit that controls a valve for adjusting the oxidant gas flow rate, which is the flow rate of the oxidant gas supplied to the fuel cell, and the control unit can perform the following steps: a start-up step of starting the fuel cell by supplying the fuel gas to the fuel cell and the control unit controlling the valve to supply the oxidant gas at a first flow rate to the fuel cell; after the start-up step, a warm-up preparation step of preparing to warm up the fuel cell by controlling the valve to set the oxidant gas flow rate to a second flow rate smaller than the first flow rate; and a warm-up step of warming up the fuel cell after the warm-up preparation step, while supplying the oxidant gas at a third flow rate greater than the second flow rate to the fuel cell.

[0096] (Appendix 9) The program causes a computer to execute the control method for a fuel cell system described in Supplementary Note 8.

[0097] The present invention is not limited to the above disclosure, and various configurations can be adopted without departing from the gist of the present invention. [Explanation of symbols]

[0098] 10...Control device 12...Fuel cell system 14... fuel cell stack (fuel cell) 46... oxidant gas supply passage 46a...Upstream supply flow path 46b...Downstream supply flow path 48...Oxidizing gas discharge flow path 48a...Upstream discharge flow path 48b...downstream discharge flow path 50...bypass flow path 52... valve 54... supply valve 56...Discharge valve 58...Bypass valve 74... battery 88... control unit Q1…1st flow rate Q2…2nd flow rate Q3…Third flow rate V1…Start voltage V2: Voltage threshold V3: Warm-up voltage

Claims

1. a fuel cell that generates electricity through an electrochemical reaction between a fuel gas and an oxidant gas; a battery capable of being charged with the power generated by the fuel cell; A control device for controlling a fuel cell system comprising: a control unit that controls a valve for adjusting an oxidant gas flow rate, which is the flow rate of the oxidant gas supplied to the fuel cell; The control unit is a start-up step of starting up the fuel cell by supplying the fuel gas to the fuel cell and controlling the valve to supply the oxidant gas at a first flow rate to the fuel cell; a warm-up preparation step of preparing for warming up the fuel cell by controlling the valve to set the oxidant gas flow rate to a second flow rate that is smaller than the first flow rate after the startup step; a warm-up step of warming up the fuel cell while supplying the oxidant gas to the fuel cell at a third flow rate that is greater than the second flow rate after the warm-up preparation step; The control device is capable of performing the above.

2. The control device according to claim 1 , A control device, in which, in the warm-up preparation step, when the output voltage of the fuel cell drops to a predetermined voltage threshold, the control unit controls the valve to set the oxidant gas flow rate from the second flow rate to the third flow rate.

3. The control device according to claim 1 , the valve includes a supply valve provided in an oxidant gas supply passage for supplying the oxidant gas to the fuel cell, In the starting step, the control unit opens the supply valve, The control device, when the oxidant gas flow rate is set from the first flow rate to the second flow rate in the warm-up preparation step, the control unit closes the supply valve to a predetermined supply suppression opening degree.

4. The control device according to claim 3, the valve includes a discharge valve provided in an oxidant gas discharge passage through which an oxidant exhaust gas discharged from the fuel cell flows, A control device in which, in the start-up step, the control unit opens the exhaust valve.

5. The control device according to claim 4, The control device, when the oxidant gas flow rate is set from the first flow rate to the second flow rate in the warm-up preparation step, the control unit closes the exhaust valve to a predetermined exhaust suppression opening degree.

6. The control device according to claim 4, the valve includes a bypass valve provided in a bypass flow path connecting the oxidant gas supply flow path and the oxidant gas discharge flow path, one end of the bypass flow path is connected to a portion of the oxidant gas supply flow path that is upstream of the supply valve, the other end of the bypass flow path is connected to a portion of the oxidant gas discharge flow path that is downstream of the discharge valve, In the warm-up preparation step, the control unit maintains the bypass valve in an open state.

7. A fuel cell system comprising the control device according to any one of claims 1 to 6.

8. a fuel cell that generates electricity through an electrochemical reaction between a fuel gas and an oxidant gas; a battery capable of being charged with the power generated by the fuel cell; a control unit that controls a valve for adjusting an oxidant gas flow rate, which is the flow rate of the oxidant gas supplied to the fuel cell; A control method for a fuel cell system comprising: a start-up step of starting up the fuel cell by supplying the fuel gas to the fuel cell and controlling the control unit to supply the oxidant gas at a first flow rate to the fuel cell; a warm-up preparation step of preparing for warming up the fuel cell by controlling the valve to set the oxidant gas flow rate to a second flow rate that is smaller than the first flow rate after the startup step; a warm-up step of warming up the fuel cell while supplying the oxidant gas to the fuel cell at a third flow rate that is greater than the second flow rate after the warm-up preparation step; A method for controlling a fuel cell system, comprising:

9. A program for causing a computer to execute the method for controlling a fuel cell system according to claim 8.

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