Fuel cell system and method for controlling a fuel cell system

Abstract

Fuel cell system (100) with: a fuel cell (10) which is configured to generate energy by receiving a supply of a fuel gas and an oxidant gas, an auxiliary machine (120) used for the operation of the fuel cell (10), a tank (31) which is configured to store the fuel gas, wherein the tank (31) is configured to supply the fuel gas stored in the tank (31) to the fuel cell (10) through a supply tube (32) and to receive the fuel gas supplied through a supply tube (52), a storage volume measurement unit (102) which is configured to record a measured value representing a volume of the fuel gas stored in the tank (31), a secondary battery (86) designed to supply energy to the auxiliary machinery (120), an energy accumulation level measurement unit (88) which is configured to measure the level of energy accumulated in the secondary battery (86), a feed detection unit (104) which is designed to detect a feed of fuel gas to the tank (31) through the feed tube (52), and a control unit (101) which is designed to control the operation of the fuel cell (10) and the supply of energy from the secondary battery (86) to the auxiliary machinery (120), the control unit (101) is configured to: if the measured value detected by the storage level measurement unit (102) is less than a threshold value corresponding to a predetermined lower limit of the fuel gas stored in the tank (31), a stop processing of a stop of the supply of the fuel gas from the tank (31) to the fuel cell (10) is to be carried out, when the halting process is executed and the amount of energy accumulated in the secondary battery (86) is less than a predetermined lower limit of accumulated energy, to execute a disconnect process of electrically disconnecting the secondary battery (86) from the auxiliary machinery (120), and After the separation process has been carried out and the supply of fuel gas to the tank (31) has been detected by the supply detection unit (104), a connection process of electrically connecting the secondary battery (86) to the auxiliary machinery (120) is to be carried out.

Description

Background of the invention 1. Field of the invention

[0001] The present invention relates to a fuel cell system and a method for controlling the fuel cell system with improvement of operational continuity. 2. Description of the related prior art

[0002] There is a fuel cell system comprising a fuel cell that generates energy by receiving a supply of fuel gas stored in a tank and an oxidant gas taken from ambient air, and a secondary battery that accumulates some of the energy generated by the fuel cell and acts together with the fuel cell as an energy source. In such a fuel cell system, if gas depletion occurs, where the amount of fuel gas stored in the tank falls below a predetermined lower limit, the energy accumulated in the secondary battery can be used.For example, in the Japanese unexamined patent application publication number JP 2009-117242 A, a fuel cell system, when gas depletion occurs, drives a compressor, which is one of the auxiliary machines, and performs a reverse processing of the fuel cell using energy from a secondary battery to stop operation of the fuel cell system.

[0003] Further prior art can be found in German patent application DE 10 2015 212 805 A1, which discloses a method for operating an electric vehicle that has a fuel cell system connected to a fuel tank and a battery for energy supply, wherein an amount of energy required by the electric vehicle is provided in proportions determined by a supply strategy from electrical energy supplied by the fuel cell system and the battery, as well as an electric vehicle that is equipped to carry out such a method. According to German patent application DE 10 2015 212 805 A1, a supply strategy is adapted depending on the fill level of the fuel tank.

[0004] From JP 2009-238624 A, a fuel cell system, an auxiliary energy supply system, and their control methods are also known. Summary of the invention

[0005] However, in the fuel cell system known from the Japanese unexamined patent application publication number JP 2009-117242 A as described above, when the energy in the secondary battery was reduced, when gas depletion occurred, the energy of the secondary battery was insufficient to power auxiliary machinery even after the fuel gas was supplied to the tank, and the operation of the fuel cell could not be continued.

[0006] The object of the invention is therefore to adapt known techniques in such a way that continued operation of the fuel cell can be ensured even in the cases described above.

[0007] A technology disclosed by means of the present invention can be implemented as the following aspects.

[0008] A first aspect of the present invention is a fuel cell system. The fuel cell system comprises a fuel cell configured to generate energy by receiving a supply of fuel gas and oxidant gas, auxiliary machinery used for operating the fuel cell, a tank configured to store the fuel gas, to supply the stored fuel gas to the fuel cell through a supply tube and to receive the fuel gas supplied through a supply tube, a storage level sensing unit configured to detect a measured value representing the level of fuel gas stored in the tank, a secondary battery configured to supply energy to the auxiliary machinery, and an energy accumulation level sensing unit configured toTo measure the amount of energy accumulated in the secondary battery, a supply measurement unit configured to measure the supply of fuel gas to the tank through the supply tube, and a control unit configured to control the operation of the fuel cell and the supply of energy from the secondary battery to the auxiliary machinery. The control unit is configured to execute a stop operation, i.e., to halt the supply of fuel gas from the tank to the fuel cell, if the measured value detected by the storage level measurement unit is less than a threshold corresponding to a predetermined lower limit of the amount of fuel gas stored in the tank. Furthermore, if the stop operation is executed and the amount of energy accumulated in the secondary battery is less than a predetermined lower limit of accumulated energy,to perform a disconnection process of electrically disconnecting the secondary battery from the auxiliary machinery, and, after the disconnection process has been performed and the supply of fuel gas to the tank has been detected by the supply detection unit, to perform a connection process of electrically connecting the secondary battery to the auxiliary machinery.

[0009] With the fuel cell system as described above, if the amount of fuel gas stored in the tank is less than the minimum storage capacity and the amount of energy accumulated in the secondary battery is less than the minimum accumulated energy capacity, the secondary battery is electrically disconnected from the auxiliary machinery. This prevents a situation where the energy in the secondary battery is insufficient to start the fuel cell after fuel gas has been supplied to the tank due to the electrical consumption of the auxiliary machinery. Furthermore, after the disconnection process is complete and the supply of fuel gas to the tank is detected, the secondary battery is electrically reconnected to the auxiliary machinery.Therefore, it is possible to prevent a situation where the fuel cell cannot be started while the secondary battery remains electrically disconnected from the auxiliary machinery, even though fuel gas has been supplied to the tank. Furthermore, if the amount of fuel gas stored in the tank is less than the minimum storage level, the fuel cell operation is stopped by the lockout or stop-processing. This prevents malfunctions caused by the fuel cell continuing to operate while the fuel gas level is insufficient.

[0010] Regarding the first aspect, the fuel cell system may further include a pressure sensing unit designed to detect the pressure of the fuel gas flowing from the tank to the feed tube. The pressure sensing unit is located in the feed tube. The auxiliary machinery may include a main shut-off valve designed to control the flow of fuel gas from the tank to the feed tube by opening and closing it under the control of the control unit. The main shut-off valve is also located in the feed tube. The storage level sensing unit may obtain the measured value of the fuel gas pressure detected by the pressure sensing unit.The stop process can be a process of stopping the supply of fuel gas to the fuel cell by closing the main shut-off valve when the pressure of the fuel gas obtained by the storage level sensing unit is less than a predetermined lower limit pressure, which is the threshold.

[0011] With the fuel cell system as described above, since the main shut-off valve closes when the fuel gas pressure in the tank is reduced, it is possible to prevent further pressure reduction in the tank. Therefore, it is possible to avoid a situation where the tank pressure becomes excessively low and the tank deteriorates. Furthermore, after the fuel cell operation has stopped due to gas depletion and the fuel gas supply to the tank has ceased, the secondary battery is electrically connected to the auxiliary machinery, and the main shut-off valve can be opened, allowing the fuel cell operation to resume. Therefore, it is possible to avoid a situation where the fuel cell operation cannot be resumed because the main shut-off valve remains closed after the fuel gas supply has ceased.

[0012] In the first aspect, after execution of the stop processing, the control unit can perform a confirmation processing of a re-determination, for the number of times whether the stop processing is to be executed, by opening the main shut-off valve in response to a user operation and re-sensing the fuel gas pressure by the pressure sensing unit.

[0013] With the fuel cell system as described above, the confirmation processing is executed in response to user operation, and the fuel gas pressure in the tank is re-measured. Therefore, it is possible to avoid a situation where the main shut-off valve closes due to a faulty fuel gas pressure reading, thus halting fuel cell operation. Furthermore, the number of times the confirmation processing is executed is limited. This prevents a situation where the main shut-off valve repeatedly opens and closes due to repeated confirmation processing, which would deplete the energy in the secondary battery and prevent the shut-off valve from opening even after fuel gas has been supplied, consequently halting fuel cell operation.

[0014] Regarding the first aspect, if the measured value detected by the storage capacity measurement unit is less than a predetermined permissible value, or if, after connection processing, it is greater than the predetermined threshold, the control unit can prohibit the operation of the fuel cell and electrically disconnect the secondary battery from the auxiliary machinery.

[0015] With the fuel cell system as described above, it is possible to avoid a situation where the fuel cell continues to operate while the amount of fuel gas supplied to the tank is insufficient. Therefore, it is possible to avoid a situation where the fuel cell is operating while the amount of fuel gas supplied to the fuel cell is insufficient. Furthermore, it is possible to avoid a situation where gas depletion occurs, quickly reducing the fuel gas supply, thereby halting the fuel cell's operation and consequently reducing the amount of energy accumulated in the secondary battery.

[0016] In the first aspect, if the amount of energy accumulated in the secondary battery is less than a predetermined threshold of accumulated energy, which is less than the lower limit of accumulated energy, the control unit can, after connection processing, stop the operation of the fuel cell and electrically disconnect the secondary battery from the auxiliary machinery again.

[0017] With the fuel cell system according to the above aspect, it is possible to avoid a situation in which the operation of the fuel cell continues while the minimum amount of energy accumulated in the secondary battery required for the operation of the fuel cell is not ensured.

[0018] A second aspect of the present invention is a method for controlling a fuel cell system. The fuel cell system comprises a fuel cell configured to generate energy by receiving a supply of fuel gas stored in a tank, and a secondary battery configured to supply energy to auxiliary machinery used to operate the fuel cell. The method comprises a step of sensing a measured value representing the level of fuel gas stored in the tank, a step of sensing the level of energy accumulated in the secondary battery, and a step of performing a stop-process to stop the supply of fuel gas to the fuel cell when the measured value is less than a threshold corresponding to a predetermined lower limit of the stored fuel gas.a step of executing a disconnection process of electrically disconnecting the secondary battery from the auxiliary machinery when the stop process has been executed and the amount of energy accumulated in the secondary battery is less than a predetermined lower limit of accumulated energy, and a step of executing a connection process of electrically connecting the secondary battery to the auxiliary machinery after the disconnection process has been executed and a supply of fuel gas to the tank has been detected.

[0019] The technology of the present invention can be implemented in various forms in addition to the fuel cell system and the method for controlling the fuel cell system. For example, the technology can be implemented in forms such as a method for limiting the operation of the fuel cell upon detection of gas depletion, a control unit, or a computer program for implementing such a method and a non-transient recording medium that records such a computer program, and a vehicle in which the fuel cell system is mounted. Brief description of the drawings

[0020] Features, advantages, and technical and industrial significance of exemplary embodiments of the invention are described below with reference to the attached drawings, in which the same symbols denote the same elements, and wherein: Fig. 1. A schematic diagram of a fuel cell system is shown. Fig. 2 is a schematic diagram illustrating an electrical configuration of the fuel cell system, Fig. 3A is a flow diagram that describes a flow of a gas exhaustion processing according to a first embodiment, Fig. 3B is a flowchart that describes a flow of a commissioning process according to the first embodiment, Fig. 4 is a flow diagram that describes a flow of gas exhaustion processing according to a second embodiment, Fig. 5 is a flowchart that describes a flow of commissioning processing according to a third embodiment, and Fig. 6 is a flowchart that describes a flow of commissioning processing according to a fourth embodiment. Detailed description of embodiments. First embodiment example.

[0021] Fig. Figure 1 is a schematic diagram illustrating a configuration of a fuel cell system 100 according to a first embodiment. The fuel cell system 100 comprises a fuel cell 10 for generating energy by receiving a supply of fuel gas and an oxidant gas, which are reactant gases. The fuel cell system 100 according to the first embodiment is mounted on a vehicle and supplies energy generated by the fuel cell 10 to a drive motor, an electrical component, a device that supplies energy to the outside, auxiliary machines, and the like of the vehicle.

[0022] In the first embodiment, the fuel cell 10 is a polymer membrane fuel cell and generates energy through an electrochemical reaction between hydrogen as a fuel gas and oxygen as an oxidant gas. The fuel cell 10 has a stacked structure in which a plurality of individual cells 11 are stacked. Each of the individual cells 11 is a self-generating energy source and comprises a membrane electrode assembly, which is an energy source body in which electrodes, having a catalyst, are arranged on both surfaces of an electrolyte membrane, and two separators that enclose the membrane electrode assembly between them. The electrolyte membrane comprises a polymer membrane thin film or a solid polymer thin film that exhibits good proton conductivity in a moist state, in which the electrolyte membrane contains moisture internally.An illustration of each component of the individual cell 11 described above is omitted. Furthermore, the fuel cell 10 is not limited to a polymer membrane electrolyte fuel cell, and various other types of fuel cells can be used. In another embodiment, for example, a solid oxide fuel cell can be used as the fuel cell 10.

[0023] The fuel cell system 100 comprises a control unit 101, which controls the operation of the fuel cell 10. The control unit 101 includes an electronic control unit (ECU) with at least one processor and a primary memory device. The processor executes a program or instruction read from the primary memory device. Accordingly, the control unit 101 performs various functions for controlling the operation of the fuel cell 10. In addition, at least part of the function of the control unit 101 can be implemented by means of a hardware circuit. The control unit 101 comprises, as functional units, a storage level measurement unit 102 and a feed measurement unit 104. The storage level measurement unit 102 and the feed measurement unit 104 are described below.

[0024] The fuel cell system 100 further comprises a fuel gas supply and discharge system 20 and an oxidant gas supply and discharge system 60 as components that control the supply of reaction gas to the fuel cell 10. The fuel gas supply and discharge system 20 comprises a supply unit 30, which supplies the fuel gas to the anode of the fuel cell 10, and a circulation unit 40, which discharges wastewater that has been discharged from the anode of the fuel cell and circulates the fuel gas that has not been used to generate energy back to the fuel cell 10. The fuel gas supply and discharge system 20 further comprises a supply unit 50, which supplies the fuel gas to the supply unit 30.

[0025] The feed unit 30 comprises a tank 31 that stores high-pressure fuel gas. The feed unit 30 can include a plurality of tanks 31, and the tank 31 can be a high-pressure tank. The tank 31 can have a pressure resistance of 30 MPa to 80 MPa. The tank 31 comprises a tank body part 311, which is formed by means of a hollow container, and a closure part 312 for sealing an opening of the tank body part 311. The tank body part 311 has a configuration in which a surface layer of a resin lining is covered with a reinforcing fiber layer. The reinforcing fiber layer is formed by thermosetting a thermosetting resin impregnated with a carbon fiber that is wound around the surface layer of the resin lining. Alternatively, in another embodiment, the tank body part 311 can have a metal lining instead of the resin lining.

[0026] The sealing element 312 is a metal part that is airtightly attached to the opening provided at one end of the main tank body 311. The sealing element 312 is provided with a gas flow path 313 that communicates with the interior of the main tank body 311. The gas flow path 313 is equipped with a check valve 314 and a manual valve 315. The check valve 314 prevents fuel gas from flowing backward from the main tank body 311 to a supply line, pipe, or tube 52 of the supply unit 50, which will be described below. The manual valve 315 is located closer to the main tank body 311 than the check valve 314. The manual valve 315 is normally open and is closed manually by an operator, for example, during maintenance.

[0027] A temperature measuring unit 316 is provided within the main tank body 311 at a position exposed to the fuel gas filled into the main tank body 311 and is attached to the closure part 312. The temperature measuring unit 316 includes a temperature sensor. The temperature measuring unit 316 measures the internal temperature of the tank 31 and outputs the measurement result to the control unit 101.

[0028] The feed unit 30 further comprises a feed tube 32, which connects the tank 31 and the anode inlet of the fuel cell 10. The feed tube 32 is connected to a section between the check valve 314 and the manual valve 315 in the gas flow path 313, which is provided in the closure part 312 of the tank 31.

[0029] The feed unit 30 further comprises a main shut-off valve 33, a regulator 35, and a feed device 36 as components that control the flow of the fuel gas in the feed tube 32. The main shut-off valve 33, the regulator 35, and the feed device 36 are arranged in the feed tube 32 in sequence from the upstream side, which is the side of the tank 31.

[0030] The main shut-off valve 33 is designed by means of an electromagnetic valve that opens and closes electromagnetically under the control of the control unit 101. The main shut-off valve 33 controls the outflow of fuel gas from the tank 31 to the feed tube 32. In the first embodiment, the main shut-off valve 33 is integrally attached to the closure part 312 of the tank 31. The main shut-off valve 33 is part of an auxiliary machine 120, which uses the energy in the secondary battery 86, which is located in Fig. Figure 2 illustrates the following. The control unit 101 normally opens the main shut-off valve 33 when the fuel cell system 100 starts operating, keeps the main shut-off valve 33 open during operation of the fuel cell 10, and closes the main shut-off valve 33 when the fuel cell system 100 stops operating.

[0031] The regulator 35 is a pressure-reducing valve and adjusts the pressure within the supply tube 32 on the upstream side of the supply device 36. The supply device 36 periodically opens and closes, sending the fuel gas to the fuel cell 10 under the control of the control unit 101. The supply device 36 includes, for example, an injector, which is an electromagnetically operated on / off valve that opens and closes according to a preset actuation cycle. The control unit 101 adjusts the amount of fuel gas supplied to the fuel cell 10 by controlling the actuation cycle of the supply device 36.

[0032] The feed unit 30 further comprises a pressure sensing unit 37, which detects the pressure of the fuel gas flowing from the tank 31 to the feed tube 32. The pressure sensing unit 37 includes a pressure sensor. The pressure sensing unit 37 is provided on the downstream side of the main shut-off valve 33 and on the upstream side of the regulator 35. In the first embodiment, the storage level sensing unit 102 receives the pressure detected by the pressure sensing unit 37 when the main shut-off valve 33 is open as a measured value representing the amount of fuel gas stored in the tank 31.In a gas depletion processing operation described below, the control unit 101 detects gas in which the amount of fuel gas stored in the tank 31 is less than a predetermined lower storage level, based on a determination using a detection result obtained by the storage level detection unit 102.

[0033] Furthermore, if the feed unit 30 comprises the plurality of tanks 31, each of the tanks 31 is connected in parallel to a common feed tube 32 on the upstream side of the regulator 35. In addition, a main shut-off valve 33, a check valve 314, and a manual valve 315 are provided at each tank 31. In the above configuration, the measured value, which represents the amount of stored fuel gas detected by the storage level sensing unit 102, represents the total amount of fuel gas stored in each tank 31.

[0034] The circulation unit 40 comprises a drain gas tube 41, a gas and liquid separation unit 42, a circulation tube 43, a circulation pump 44, a drain water tube 45, and a drain water valve 46. The drain gas tube 41 is connected to the anode outlet of the fuel cell 10 and the gas and liquid separation unit 42 and sends the drain gas at the anode side, including the fuel gas that was not used for energy generation at the anode of the fuel cell 10, and the drain water to the gas and liquid separation unit 42.

[0035] The gas and liquid separation unit 42 separates the gas component and the liquid component from the outflow gas flowing in through the outflow gas tube 41 and retains the liquid component in a liquid state as the outflow water at a retention section 42s within the gas and liquid separation unit 42. The gas and liquid separation unit 42 is connected to the circulation tube 43 at an upper section of the retention section 42s.

[0036] The circulation tube 43 connects the gas and liquid separation unit 42 and a section downstream of the feed device 36 of the feed tube 32 of the feed unit 30. The circulation tube 43 is equipped with a circulation pump 44. The gas component, including the gas component separated from the outflow gas in the gas and liquid separation unit 42, is sent to the circulation tube 43, is sent to the feed tube 32 by driving the circulation pump 44, and is circulated to the anode of the fuel cell 10 via the feed device 36.

[0037] The drain water tube 45 is connected to the retention part 42s of the gas and liquid separation unit 42. The drain water tube 45 is equipped with a drain water valve 46, which opens and closes under the control of the control unit 101. The control unit 101 normally closes the drain water valve 46 during operation of the fuel cell 10 and opens the drain water valve 46 at a predetermined time, so that the drain water retained in the retention part 42s is discharged through the drain water tube 45 to the outside of the vehicle. In the first embodiment, the drain water tube 45 is connected to a drain gas tube 66 of an oxidant gas supply and discharge system 60, which will be described below, and the drain water is discharged to the outside of the fuel cell system 100 through the drain gas tube 66.

[0038] The supply unit 50 comprises a container 51, which receives the supplied fuel gas, a supply tube 52, which connects the container 51 and the tank 31, a pressure measuring unit 54, which is provided in the supply tube 52, and a communication unit 55. The fuel gas is supplied to each tank 31 of the supply unit 60 through the container 51. The container 51 is located at one end of the vehicle body, as it opens towards the outside of the vehicle. The container 51 is connected to an upstream end of the gas flow path 313, which is provided at the closure part 312 of the tank 31, via the supply tube 52.

[0039] The container 51 is normally mounted on the vehicle in a rotatable manner, except when fuel gas is being supplied, and is closed by a cover 110, which is part of the vehicle body. When the cover 110 is open, the container 51 is connected to a fuel gas injection nozzle provided at a fuel gas supply source. The fuel gas supply source is, for example, a dispenser or pump provided at a hydrogen refueling station. The fuel gas injected by the injection nozzle flows through the container 51 into the supply tube 52. The inlet of the supply tube 52 is equipped with an inlet check valve 52v, which prevents fuel gas that has flowed into the supply tube 52 from leaking outwards.

[0040] Furthermore, if the supply unit 30 comprises the plurality of tanks 31, the upstream end of the gas flow path 313 of each tank 31 is connected in parallel to a common supply pipe 52. The fuel gas is supplied to each tank 31 simultaneously through the common container 51 and the common supply pipe 52.

[0041] The pressure measuring unit 54 measures the pressure of the fuel gas flowing through the supply tube 52 and outputs a measurement result to the control unit 101. The pressure measuring unit 54 includes, for example, a pressure sensor. The communication unit 55 is located near the container 51 and establishes communication between the control unit 101 and the fuel gas supply source. The communication unit 54 includes, for example, an infrared communication device.

[0042] When the supply of fuel gas to tank 31 is started, the control unit 101 initiates communication with the fuel gas supply source via the communication unit 55. The control unit 101 transmits to the fuel gas supply source a pressure measurement obtained by the pressure measuring unit 54 and a measurement of the internal temperature of tank 31 obtained by the temperature measuring unit 316. This information is used to control the amount of fuel gas supplied by the fuel gas supply source.

[0043] The feed detection unit 104 detects the supply of fuel gas to tank 31 by the feed unit 50 and records the detection history. In the first embodiment, the feed detection unit 104 detects the supply of fuel gas when the pressure measuring unit 54 detects a pressure increase in the feed tube 52. The feed detection unit 104 sets an indicator representing that the fuel gas supply has taken place and stores the indicator (flag) in a non-volatile manner. A detection result obtained by the feed detection unit 104 is used in a commissioning process following a separation process, which is described below.

[0044] In another embodiment, the supply detection unit 104 can detect the supply of fuel gas to the tank 31 using a method different from the method of detecting the pressure increase in the supply pipe 52. For example, the supply detection unit 104 can detect the fuel gas supply when communication is initiated by the communication unit 45. Alternatively, the supply detection unit 104 can detect the fuel gas supply when the temperature measuring unit 316 detects an increase in the internal temperature of the tank 31. If the vehicle is equipped with a sensor that detects the opening and closing of the lid 110, the supply detection unit 104 can detect the fuel gas supply when the sensor detects that the lid 110 is being opened.Furthermore, if the vehicle is equipped with a device with GPS functionality, such as a navigation system, the supply detection unit 104 can obtain the vehicle's position information from the device and then detect the fuel gas supply when the device registers that the vehicle is at a hydrogen station. The supply detection unit 104 can detect the fuel gas supply to tank 31 by combining the various cases described above.

[0045] The oxidant gas supply and discharge system 60 supplies oxygen, contained in the air drawn into the vehicle through the front grille, to the fuel cell 10 as an oxidant gas. The oxidant gas supply and discharge system 60 comprises a supply tube 61, a compressor 62, and an on / off valve 63. The supply tube 61 is connected to a cathode inlet of the fuel cell 10. The compressor 62 and the on / off valve 63 are located within the supply tube 61. The compressor 62 sends compressed gas, obtained by compressing air drawn from outside the vehicle, to the cathode of the fuel cell 10 through the supply tube 61. The on / off valve 63 is normally in a closed state and is opened by the compression of the compressed gas sent by the compressor 62, so that the compressed gas can flow into the fuel cell 10.

[0046] The oxidant gas supply and discharge system 60 discharges the exhaust gas discharged from the cathode of the fuel cell 10 to the outside of the vehicle. The oxidant gas supply and discharge system 60 comprises an exhaust gas tube 66 and a pressure regulating valve 68. The exhaust gas tube 66 is connected to the cathode outlet and discharges the exhaust gas discharged from the cathode of the fuel cell 10 to the outside of the vehicle. The pressure regulating valve 68 is located in the exhaust gas tube 66 and, under the control of the control unit 101, adjusts the back pressure on the cathode side of the fuel cell 10.

[0047] Fig. Figure 2 is a schematic diagram illustrating an electrical configuration of the fuel cell system 100. The fuel cell system 100 comprises a first inverter 81, an external load inverter 83, a second inverter 85, a secondary battery 86, an energy storage level sensing unit 88, a connection unit 92, and an auxiliary machine inverter 93. The fuel cell 10 is connected to an input terminal of the first inverter 81 via a first DC conductor L1. The first inverter 81 includes a boost converter. Under the control of the control unit 101, the first inverter 81 controls an output current of the fuel cell 10 by boosting an output voltage of the fuel cell 10.

[0048] An output terminal of the first converter 81 is connected to a DC terminal of the external load converter 83 via a second DC conductor L2. The external load converter 83 performs a conversion between DC and AC. An AC terminal of the external load converter 83 is connected to an external load device 200. The external load device 200 comprises the drive motor, the electrical components, the power supply device, and the like, of the vehicle as described above. The external load converter 83 is provided for each load device included in the external load device 200. However, this is in Fig. 2 For the sake of simplicity, this is illustrated by a block. The control unit 101 controls alternating current energy supplied to the external load device 200 through the external load converter 83.

[0049] The second inverter 85 is connected to the second DC conductor L2, and the secondary battery 86 is connected to the second inverter 85 via a third DC conductor L3. The secondary battery 86 comprises, for example, a lithium-ion battery. The secondary battery 86 stores a portion of the energy generated by the fuel cell 10 or of renewable energy generated by the external load device 200. Together with the fuel cell 10, the secondary battery 86 acts as an energy source for the fuel cell system 100 under the control of the control unit 101. Furthermore, the secondary battery 86 supplies energy to the auxiliary machinery 120 as described below. The control unit 101 controls the second inverter 85, adjusts the voltage of the second DC conductor L2, and controls the charging and discharging of the secondary battery 86.

[0050] The energy accumulation measurement unit 88 measures the amount of energy accumulated in the secondary battery 86. The amount of accumulated energy is represented by a state of charge (SOC). The energy accumulation measurement unit 88 outputs a measurement result to the control unit 101.

[0051] The third DC conductor L3, which connects the second converter 85 and the secondary battery 86, is connected to a DC terminal of the auxiliary machine converter 93. An AC terminal of the auxiliary machine converter 93 is connected to the auxiliary machinery 120, which is used to control the operation of the fuel cell system 100 or the vehicle. The auxiliary machinery 120 is used to operate the fuel cell 10 and is driven by the energy in the secondary battery 86, under the auxiliary machinery mounted on the vehicle 120. In the first embodiment, the auxiliary machinery 120 includes the main shut-off valve 33, which is described above. The auxiliary machinery 120 may also include a compressor 62, a circulation pump 44, and the like. Furthermore, the auxiliary machine converter 93 is provided for each auxiliary machine included in the auxiliary machinery 120. However, this is in Fig. 2 For the sake of simplicity, this is illustrated by a block. The auxiliary machine converter 93 converts the direct current output by the secondary battery 86 into alternating current and supplies the alternating current to the auxiliary machinery 120. The control unit 101 controls the alternating current energy supplied to the auxiliary machinery 120 via the auxiliary machine converter 93.

[0052] The connection unit 92 switches the electrical connection between the secondary battery 86 and the second DC conductor L2 on or off under the control of the control unit 101. The connection unit 92 includes, for example, a relay circuit. Normally, during operation of the fuel cell system 100, the control unit 101 causes the connection unit 92 to connect the secondary battery 86 to the auxiliary machinery 120 and the external load device 200 via the second DC conductor L2. During the gas depletion process, which will be described below, when gas depletion is detected and the amount of energy accumulated in the secondary battery 86 is insufficient, the control unit 101 performs the disconnection process, which causes the connection unit 92 to electrically disconnect the secondary battery 86 from the auxiliary machinery 120 and the external load device 200.

[0053] Fig. Figure 3A is a flowchart describing the gas depletion processing flow according to the first embodiment. The gas depletion processing is executed to prevent a situation in which the operation of the fuel cell 10 continues while the amount of fuel gas stored in the tank 31 is less than a predetermined lower storage level. The control unit 101 monitors the amount of fuel gas stored in the tank 31 by repeatedly executing the gas depletion processing with a predetermined control cycle during the operation of the fuel cell system 100 after the fuel cell system 100 has been commissioned.

[0054] In step S10, the storage level sensing unit 102 obtains the pressure of the fuel gas in the feed tube 32, which is detected by the pressure sensing unit 37, as a measured value representing the amount of fuel gas stored in the tank 31. Using this measured value, the control unit 101 determines whether the blocking or halting processing is to be executed in the subsequent steps S20 to S30.

[0055] In step S20, the control unit 101 determines whether the measured value, detected by the storage level sensing unit 102, is less than a threshold value corresponding to a predetermined lower limit of the fuel gas volume stored in the tank 31. In the first embodiment, the control unit 101 determines whether the fuel gas pressure, detected by the pressure sensing unit 37, is less than a predetermined lower limit pressure, a threshold value corresponding to the lower limit storage level. The lower limit pressure can be a value greater than the lower limit of the internal pressure of the tank 31. The lower limit can be a value below which no deterioration occurs in the tank 31 and which has been determined beforehand through experiments or the like. If the lowest pressure to be used for the tank 31 is set, the lower limit pressure can be greater than the lower limit pressure.

[0056] If the measured value acquired in step S10 is equal to or greater than the threshold value, i.e., if the pressure of the fuel gas in tank 31 is equal to or greater than the lower limit pressure, the control unit 101 terminates the gas depletion processing and resumes operation of the fuel cell 10. In this case, since the amount of fuel gas stored in tank 31 is equal to or greater than a lower limit storage level, normal operation of the fuel cell 10 is expected to continue.

[0057] In contrast, if the measured value acquired in step S10 is lower than the threshold value, i.e., if the pressure of the fuel gas detected by the pressure sensing unit 37 is lower than the lower limit pressure, the control unit 101 initiates a valve closing process by closing the main shut-off valve 33 in step S30. Accordingly, the control unit 101 stops the operation of the fuel cell 10 by causing the feed unit 30 of the fuel gas supply and discharge system 20 to stop the supply of fuel gas to the fuel cell 10. This is because, in this case, there is a possibility that normal operation of the fuel cell 10 could be prevented by gas depletion, in which the amount of fuel gas stored in the tank 31 is less than the lower limit storage level.Furthermore, in this specification, "stopping the operation of fuel cell 10" means terminating the control of the reactant gas supply to cause fuel cell 10 to output the target energy. Therefore, a state in which the operation of fuel cell 10 is stopped includes a state in which energy generation by fuel cell 10 continues through the reactant gas that remains after the gas supply has been stopped.

[0058] Furthermore, in the first embodiment, in step S30, the control unit 101 also causes the oxidant gas supply and discharge system 60 to stop supplying the oxidant gas to the fuel cell 10. The control unit 101 can also notify a user that the operation of the fuel cell 10 has been stopped due to insufficient fuel gas via a notification unit such as a vehicle indicator or a display (not shown).

[0059] By executing the blocking or halting processing in steps S20 to S30, it is possible to prevent a situation in which the operation of fuel cell 10 continues in a state where the amount of supplied fuel gas cannot be guaranteed due to gas depletion. Therefore, it is possible to prevent an excessive load being applied to or imposed on fuel cell 10 due to energy generation in a state where the reactant gas is insufficient. For example, it is possible to prevent malfunctions such as catalyst degradation due to insufficient fuel gas or a reduction in system efficiency due to a decrease in the energy generation efficiency of fuel cell 10.

[0060] Furthermore, in the gas exhaustion process according to the first embodiment, once gas exhaustion has been detected, the main shut-off valve 33 is closed. This prevents the fuel gas from flowing from the tank 31 into the feed pipe 32 and prevents the internal pressure of the tank 31 from decreasing further. Therefore, it prevents the internal pressure of the tank 31 from dropping to a point where a low pressure in the tank 31 would degrade its performance.

[0061] Furthermore, after the execution of the lock processing or halt processing in steps S20 to S30, in step S40 the control unit 101 causes the energy accumulation level measurement unit 88 to measure the amount of energy stored in the secondary battery 68. The measured amount of energy accumulated in the secondary battery 86 is used to determine whether the halt processing should be executed in subsequent steps S50 to S60. In step S50, the control unit 101 determines whether the amount of energy accumulated in the secondary battery 86 is less than a predetermined lower limit of accumulated energy. The lower limit of accumulated energy is an artificially determined lower limit of the amount of accumulated energy and is a conceptual value different from the threshold physically required to maintain the performance of the secondary battery 86.In the first embodiment, the lower limit of accumulated energy is set to a value that can ensure energy that is expected to be consumed in the auxiliary machinery 120, for example, energy required to open the main shut-off valve 33 from the time when the fuel gas is supplied until the time when the operation of the fuel cell 10 continues.

[0062] In step S50, if it is determined that the amount of energy accumulated in the secondary battery 86 is less than the lower limit of accumulated energy, the control unit 101, in step S60, causes the connection unit 92 to electrically disconnect the secondary battery 86 from the auxiliary machinery 120 and the external load device 200. This prevents the energy remaining in the secondary battery 86 from being consumed by the auxiliary machinery 120 or the external load device 200. In step S60, the control unit 101 can notify the user via the notification unit that the operation of the fuel cell 10 cannot continue until the fuel gas is supplied. After the disconnection process is completed, the control unit 101 terminates the gas depletion process.In this case, since the operation of the fuel cell 10 is stopped and the supply of energy from the secondary battery 86 is also stopped, the control unit 101 terminates the operation of the fuel cell system.

[0063] If, in step S50, the amount of energy accumulated in the secondary battery 86 is equal to or greater than the lower limit of accumulated energy, the control unit 101 terminates the gas depletion processing as is. In this case, the control unit 101 initiates a control to continue supplying energy from the secondary battery 86 to the auxiliary machinery 120 and the external load device 200 while the operation of the fuel cell 10 is stopped. During this control, the vehicle can move using the energy in the secondary battery 86. During this control, the control unit 101 can notify the user via the notification unit that the operation of the fuel cell system 100 is continuing using the energy in the secondary battery 86 while the fuel cell 10 is generating energy.

[0064] Furthermore, even when the supply of fuel gas to the fuel cell 10 is stopped by the stop-processing or blocking-processing, the control unit 101 continuously repeats the gas depletion processing while energy in the secondary battery 86 is supplied to the auxiliary machinery 120 or the external load device 200, and the operation of the fuel cell system 100 continues. If fuel gas is supplied during the operation of the fuel cell system 100, and the amount of fuel gas stored in the tank 31 is equal to or greater than the lower storage level, the control unit 101 opens the main shut-off valve 33 and resumes the supply of fuel gas to the fuel cell 10.

[0065] Fig. Figure 3B is a flowchart describing the flow of a commissioning or start-up process that is executed when the fuel cell system 100 is restarted after the separation process in the gas depletion process has been completed. The start-up or commissioning process is executed when the user performs the commissioning operation of the fuel cell system 100 after the separation process in the gas depletion process has been completed and the operation of the fuel cell system 100 has ended. The commissioning process can be executed automatically when the start-up time of the fuel cell system 100, which is predefined in the control unit 101, is reached, and not through direct user operation.

[0066] Steps S70 to S80 are the connection processing of an electrical connection of the secondary battery 86 to the auxiliary machinery 120 when the supply of fuel gas to the tank 31 has been detected. In step S70, the control unit 101 determines whether the supply detection unit 104 has detected the supply of fuel gas to the tank 31 through the supply tube 52 of the supply unit 50 after the separation processing in the gas depletion processing has been carried out. If the supply detection unit 104 has detected the supply of fuel gas to the tank 31 after the separation processing, in step S80 the control unit 101 causes the connection unit 92 to electrically connect the secondary battery 86 to the auxiliary machinery 120 and the external load device 200.

[0067] After the aforementioned connection processing has been carried out, in step S90, the control unit 101 activates the supply of fuel gas from tank 31 to fuel cell 10 by opening the main shut-off valve 33 and starts the operation of the fuel cell system 100. Furthermore, the control unit 101 starts the operation of fuel cell 10 by causing the fuel gas supply and discharge system 20 and the oxidant gas supply and discharge system 60 to start the supply of reaction gas to fuel cell 10.

[0068] In step S70, if there is no history or record of the fuel gas supply to tank 31, the control unit 101 terminates the commissioning process as is. In this case, the fuel cell system 100 is not started, and its operation does not continue. Similarly, if the separation process is performed during the gas depletion process, the fuel cell system 100 cannot be started until the fuel gas is supplied to tank 31 through the supply tube 52 of the supply unit 50.

[0069] As described above, in the fuel cell system 100 according to the first embodiment, when the blocking / stop processing and the disconnect processing are executed in the gas depletion processing, the secondary battery 86 is electrically disconnected from the load device until the supply of fuel gas is detected. Similarly, during the start-up processing in step S90, the energy required to start the operation of the fuel cell 10, which contains the energy in the secondary battery 86 needed to open the main shut-off valve 33, is prevented from becoming insufficient. Therefore, it is prevented that the fuel cell 10 enters a state in which its operation cannot continue due to insufficient energy in the secondary battery 86, even though the fuel gas has been supplied to the tank 31 after the execution of the blocking / stop processing and the disconnect processing.

[0070] Furthermore, in the fuel cell system 100 according to the first embodiment, when the fuel gas is supplied to the tank 31 during the commissioning process after the execution of the blocking or stop processing and the separation processing in the gas exhaustion process, the electrical connection between the secondary battery 86 and the auxiliary machinery 120 is restored by the connection processing. Therefore, it is prevented that the fuel cell 10 falls into a state in which its operation cannot be continued because energy is not supplied from the secondary battery 86 to the auxiliary machinery 120, and the main shut-off valve 33 remains closed after the fuel gas supply.

[0071] Furthermore, in the fuel cell system 100 according to the first embodiment, when gas depletion is detected, i.e., when the amount of fuel gas stored in the tank 31 is less than the minimum storage level, the supply of fuel gas to the fuel cell 10 is stopped, and the operation of the fuel cell 10 is stopped. This prevents the fuel cell 10 from continuing to operate while the amount of fuel gas supplied is insufficient, and thus avoids malfunctions due to fuel gas depletion. Additionally, in the fuel cell system 100 according to the first embodiment, the main shut-off valve 33 is closed in a gas depletion state in which the internal pressure of the tank 31 is less than the minimum pressure. This prevents a situation in which deterioration occurs in the tank 31 because the internal pressure of the tank 31 drops well below the minimum pressure. Second embodiment

[0072] Fig. Figure 4 is a flowchart describing the gas depletion processing flow according to the second embodiment. The configuration of the fuel cell system 100 according to the second embodiment is approximately the same as the configuration described in the first embodiment. The gas depletion processing according to the second embodiment is essentially the same as the gas depletion processing according to the first embodiment, except that steps S52, S54, and S56 are added.

[0073] In the gas depletion processing according to the second embodiment, the control unit 101 performs the processing steps S10 to S50 in a manner comparable to that described in the first embodiment. Furthermore, in the second embodiment, a value for the lower limit of accumulated energy, which is used as a determining condition in step S50, can be set in a pre-estimation of the energy to be consumed by executing a confirmation processing procedure, which will be described below.

[0074] In the second embodiment, if step S50 determines that the amount of energy accumulated in the secondary battery 86 is less than the lower limit of accumulated energy, the control unit 101 suspends an execution of step S60 for a predetermined operator reception period. The operator reception period is a predetermined period of time after the main shut-off valve 33 was closed in step S30. In step S52, the control unit 101 determines whether a predetermined user operation, which triggers the confirmation processing, has been detected within the operator reception period. During the confirmation processing, the main shut-off valve 33 is opened, the pressure of the fuel gas in the feed tube 32 is again detected by the pressure sensing unit 37, it is again confirmed whether gas depletion has occurred, and it is again determined whether the blocking or hold processing is to be executed.In the second embodiment, the predetermined user operation that triggers the confirmation processing is, for example, an operation that commands the operation of the fuel cell 10 to be continued or resumed. This operation can be an operation to start or stop the vehicle, or an operation that commands the amount of fuel gas stored in the tank 31 to be confirmed.

[0075] In step S52, if the user's predetermined operation is detected within the operation reception period, the control unit 101 determines whether the acknowledgment processing in step S54 has already been executed a predetermined number of times after the halt or lock processing in steps S20 to S30. If the number of times the acknowledgment processing has been executed after the first lock or halt processing is less than a predetermined number of times, the control unit 101 executes the acknowledgment processing as follows.

[0076] In step S56, the control unit 101 opens the main shut-off valve 33 and repeats the processing in step S10. In step S10, the storage level sensing unit 102 again detects the fuel gas pressure via the pressure sensing unit 37 and updates the measured value, which represents the amount of fuel gas stored in the tank 31. In step S20, the control unit 101 compares the updated measured value with the lower limit pressure, which is a threshold value corresponding to the lower limit storage level. In step S20, if the determination result has changed, i.e., if it has been determined that the updated measured value is greater than the lower limit pressure, which is the threshold, the control unit 101 terminates the gas depletion processing and resumes normal operation of the fuel cell 10.If, in step S20, it is determined that the updated measured value is less than the lower limit pressure, which is the threshold value, the control unit 101 closes the main shut-off valve 33 again in step S30. After the confirmation processing has been executed, in step S52, if the predetermined user operation is detected again within the operation reception period, and if the number of times the confirmation processing has been executed is less than a predetermined number, the control unit 101 executes the confirmation processing again.

[0077] If, in step S52, the predetermined user operation is not detected within the operation reception period, the control unit 101 electrically disconnects the secondary battery 86 from the auxiliary machinery 120 and the external load device 200 in step S60 and terminates the gas exhaustion processing. If, in step S54, it is determined that the number of times the confirmation processing has been executed is equal to or greater than the predetermined number, the control unit 101 electrically disconnects the secondary battery 86 from the auxiliary machinery 120 and the external load device 200 in S60 and terminates the gas exhaustion processing. Similarly, if the fuel cell system 100 is started after the disconnection processing has been executed, the commissioning or start-up processing, as described in step S54, is terminated. Fig. 3B illustrates that it is carried out in a manner comparable to that described in the first embodiment.

[0078] As described above, in the gas depletion processing according to the second embodiment, after the execution of the blocking or stop processing, a confirmation processing is repeated in which the amount of fuel gas stored in tank 31 is reconfirmed a predetermined number of times each time the user performs the predetermined operation within the operating reception period. Therefore, a situation is avoided in which the operation of the fuel cell 10 remains stopped because the main shut-off valve 33 remains closed due to, for example, a detection error in the measured value representing the amount of fuel gas stored in tank 31, and the like.Furthermore, since the number of times the confirmation processing is executed is limited to a predetermined number, it is possible to avoid a situation in which the confirmation processing is repeated without limitation, thus preventing the energy in the secondary battery 86 from being consumed to such an extent that the operation of the fuel cell 10 cannot be continued or resumed after the fuel gas is supplied. Moreover, with the fuel cell system 100 and its control method according to the second embodiment, various functions and effects comparable to those described in the first embodiment can be achieved. Third example

[0079] Fig. Figure 5 is a flowchart describing the commissioning process flow according to the third embodiment. The configuration of the fuel cell system 100 according to the third embodiment is approximately the same as the configuration described in the first embodiment. The commissioning or start-up process according to the third embodiment is executed when the fuel cell system 100 is started after the execution of the lock-out or stop-up process and the separation process in the gas exhaustion process, in a manner comparable to that described in the second embodiment. The commissioning process according to the third embodiment is approximately the same as the commissioning process described in Fig. 3B is illustrated and described in the first embodiment, except that the processing after the execution of the connection processing is different in steps S70 to S80.

[0080] The control unit 101 electrically connects the secondary battery 86 to the auxiliary machinery 120 and the external load device 200 in step S80, and then opens the main shut-off valve 33 in step S81. Furthermore, during these steps, the control of the feed device 36 and the oxidant gas supply and discharge system 60 of the fuel gas supply and discharge system 20 remains suspended, and the operation of the fuel cell 10 is not continued.

[0081] In step S82, the storage level sensing unit 102 obtains the pressure in the feed tube 32, which is detected by the pressure sensing unit 37 after the main shut-off valve 33 is opened, as a measured value representing the amount of fuel gas stored in the tank 31. In step S83, the control unit 101 determines whether the measured value obtained in step S82 is less than a predetermined allowable value. The allowable value is greater than the threshold corresponding to the lower limit storage level used in step S20. The allowable value is defined as a value representing an amount of stored fuel gas at which the operation of the fuel cell 10 can continue for a certain period of time after the fuel cell 10 resumes operation.

[0082] If the measured value recorded in step S82 is equal to or greater than the permissible value, the control unit 101 starts the supply of fuel gas to the fuel cell 10 and starts the operation of the fuel cell 10 in step S91. If the measured value recorded in step S82 is less than the permissible value, the control unit 101 prevents the supply of fuel gas to the fuel cell 10 from starting by closing the main shut-off valve 33 again in step S88. In addition, the control unit 101 causes the connection unit 92 to electrically disconnect the secondary battery 86 from the auxiliary machinery 120 and the external load device 200. Accordingly, the start of the operation of the fuel cell 10 is prohibited, and the fuel cell system 10 enters a standby state in which it waits for the supply of fuel gas to the tank 31.Afterwards, if the user performs the commissioning operation of the fuel cell system 100 or if a preset commissioning time of the fuel cell system 100 is reached, the commissioning processing or start processing is executed again.

[0083] As described above, in the fuel cell system 100 according to the third embodiment, even if the supply of fuel gas to the tank 31 is detected after the separation process in the gas depletion process, the operation of the fuel cell 10 is prohibited or forbidden, even if the supply level is insufficient. Therefore, a situation is avoided in which the amount of energy accumulated in the secondary battery 86 is reduced due to insufficient stored fuel gas and the operation of the fuel cell 10 is stopped within a short time.Furthermore, in the fuel cell system 100 according to the third embodiment, if the fuel gas does not flow sufficiently from the tank 31 to the feed tube 32 due to a fault in the main shut-off valve 33, for example, even if the supply of fuel gas to the tank 31 is detected after the separation process, the start of operation of the fuel cell 10 is also prohibited. Therefore, it is avoided that the operation of the fuel cell 10 is started while the supply of fuel gas to the fuel cell 10 cannot be carried out without problems. In addition, the fuel cell system 100 and its control method according to the third embodiment can achieve various functions and effects described in the first and second embodiments. Fourth embodiment

[0084] Fig.Figure 6 is a flowchart describing the commissioning process flow according to the fourth embodiment. The configuration of the fuel cell system 100 according to the fourth embodiment is approximately the same as the configuration described in the first embodiment. The commissioning or start-up process according to the fourth embodiment is executed when the fuel cell system 100 is started after the execution of the lock-out or stop-up process and the disconnect-out process in the gas exhaustion process, in a manner comparable to that described in the second embodiment. The commissioning process according to the fourth embodiment is approximately the same as the commissioning process according to the third embodiment, except that the commissioning process is added in steps S85 and S86.

[0085] During the commissioning process according to the fourth embodiment, if in step S83 it is determined that the measured value acquired in step S82 is equal to or greater than the permissible value, the control unit 101 further determines the amount of energy accumulated in the secondary battery 86 in steps S85 and S86. In step S85, the control unit 101 causes the energy accumulation level sensing unit 88 to detect the current amount of energy accumulated in the secondary battery 86. Subsequently, in step S86, the control unit 101 determines whether the amount of accumulated energy detected in step S85 is less than the predetermined threshold for the amount of accumulated energy.This level of accumulated energy threshold is a predetermined value as the minimum limit of energy accumulated in the secondary battery 86 that can allow the resumption of operation of the fuel cell 10, and is less than the lower limit of accumulated energy used in step S50.

[0086] If the amount of accumulated energy detected in step S85 is equal to or greater than the accumulated energy threshold, the control unit 101 starts the supply of fuel gas to the fuel cell 10 and starts the operation of the fuel cell 10 in step S91. If the amount of accumulated energy detected in step S85 is less than the accumulated energy threshold, the control unit 101 prevents the supply of fuel gas to the fuel cell 10 from starting by closing the main shut-off valve 33 again in step S88. Furthermore, the control unit 101 causes the connection unit 92 to electrically disconnect the secondary battery 86 from the auxiliary machinery 120 and the external load device 200. Accordingly, the operation of the fuel cell 10 is prevented until the secondary battery 86 is charged.

[0087] As described above, during the commissioning process according to the fourth embodiment, even if the fuel gas can be supplied to the fuel cell 10 after the separation process in the gas depletion process, if the amount of energy accumulated in the secondary battery 86 is insufficient, the operation of the fuel cell 10 is prohibited from continuing or resuming. Therefore, a situation is avoided in which energy cannot be supplied to the auxiliary machinery 120 because the amount of energy accumulated in the secondary battery 86 is insufficient immediately after the fuel cell 10 resumes operation, thus preventing the operation of the fuel cell 10 from being stopped or interrupted.Furthermore, a situation is avoided in which the performance of the secondary battery 86 deteriorates because the amount of energy accumulated in the secondary battery 86 becomes zero. Moreover, the fuel cell system 100 and its control method according to the fourth embodiment can achieve various functions and effects described in each of the preceding embodiments. Other examples of implementation

[0088] The various configurations described in the preceding embodiments can be modified, for example, as shown below. Similar to each of the preceding embodiments, all of the other embodiments described below are examples of aspects for implementing the technology of the present invention. First alternative embodiment

[0089] In the gas exhaustion process in each of the preceding embodiments, the valve closing process of closing the main shut-off valve 33 in step S30 can be omitted. In step S30, the control unit 101 can simply stop the actuation or drive of the feed device 36 to stop the supply of fuel gas to the fuel cell 10. Second other embodiment

[0090] The storage level measurement unit 102 can calculate the measured value representing the current level of fuel gas stored in tank 31 using the known capacity of tank 31, the measurement result from the pressure measurement unit 37, and the temperature measurement unit 316. Furthermore, the storage level measurement unit 102 can determine the measured value representing the level of fuel gas stored in tank 31 using a method different from a method using the measured result of the pressure in the supply pipe by the pressure measurement unit 37.For example, the storage level measurement unit 102 can measure the measured value representing the extent of the fuel gas stored in the tank 31 by calculating an estimated value of the extent of fuel gas consumption from a value obtained by integrating the energy output from the fuel cell 10 after the fuel gas has been supplied to the tank 31. Third other embodiment

[0091] In the fuel cell system 100 according to each of the above embodiments described above, the secondary battery 86 does not need to be configured to supply energy to the external load device 200. Fourth other embodiment

[0092] In the fuel cell system 100 according to the third and fourth embodiments, the gas exhaustion process described in the first embodiment can be performed instead of the gas exhaustion process described in the second embodiment. Furthermore, the processing in steps S82 and S83 during the commissioning process according to the fourth embodiment can be omitted. Fifth other embodiment

[0093] In each of the foregoing embodiments, after the separation processing in the gas exhaustion processing has been carried out, although not at the time of commissioning or starting of the fuel cell system, the control unit 101 can carry out the connection processing when the start of the supply of the fuel gas to the tank 31 through the supply tube 52 is detected. Sixth other embodiment

[0094] In each of the foregoing embodiments, the fuel cell system 100 need not be mounted on the vehicle. For example, the fuel cell system 100 can be provided as an energy source at a fixed installation such as a building. In each of the foregoing embodiments, the vehicle can include a higher-level control unit that controls the operation of the vehicle, separate from the control unit 101 that performs the gas exhaust processing. Other

[0095] In the above embodiments, some or all of the functions and processes implemented by software can be implemented by hardware. Furthermore, some or all of the functions and processes implemented by hardware can be implemented by software. The hardware can consist of various circuits, such as an integrated circuit, a discrete circuit, or a combined circuit module.

[0096] The technology of the present invention is not limited to the foregoing embodiments and can be implemented with various configurations within a range that does not deviate from the scope of the present invention. For example, the technical features in the embodiments can be suitably replaced or combined according to the technical features in any aspect described in the abstract of the invention. Furthermore, the technical features can be suitably removed in a case where they are not described as essential or substantial in the present specification, as well as in a case where they are described as non-essential or inessential.

Claims

[1] Fuel cell system (100) with: a fuel cell (10) which is configured to generate energy by receiving a supply of a fuel gas and an oxidant gas, an auxiliary machine (120) used for the operation of the fuel cell (10), a tank (31) which is configured to store the fuel gas, wherein the tank (31) is configured to supply the fuel gas stored in the tank (31) to the fuel cell (10) through a supply tube (32) and to receive the fuel gas supplied through a supply tube (52), a storage volume measurement unit (102) which is configured to record a measured value representing a volume of the fuel gas stored in the tank (31), a secondary battery (86) designed to supply energy to the auxiliary machinery (120), an energy accumulation level measurement unit (88) which is configured to measure the level of energy accumulated in the secondary battery (86), a feed detection unit (104) which is designed to detect a feed of fuel gas to the tank (31) through the feed tube (52), and a control unit (101) which is designed to control the operation of the fuel cell (10) and the supply of energy from the secondary battery (86) to the auxiliary machinery (120), the control unit (101) is configured to: if the measured value detected by the storage level measurement unit (102) is less than a threshold value corresponding to a predetermined lower limit of the fuel gas stored in the tank (31), a stop processing of a stop of the supply of the fuel gas from the tank (31) to the fuel cell (10) is to be carried out, when the halting process is executed and the amount of energy accumulated in the secondary battery (86) is less than a predetermined lower limit of accumulated energy, to execute a disconnect process of electrically disconnecting the secondary battery (86) from the auxiliary machinery (120), and After the separation process has been carried out and the supply of fuel gas to the tank (31) has been detected by the supply detection unit (104), a connection process of electrically connecting the secondary battery (86) to the auxiliary machinery (120) is to be carried out. [2] Fuel cell system (100) according to claim 1, further comprising: a pressure sensing unit (37) which is configured to detect the pressure of the fuel gas flowing from the tank (31) to the feed tube (32), wherein the pressure sensing unit (37) is provided in the feed tube (32), wherein: the auxiliary machinery (120) comprises a main shut-off valve (33) which is configured to control an outflow of the fuel gas from the tank (31) to the feed tube (32) by opening and closing under control of the control unit (101), the main shut-off valve (33) being provided in the feed tube (32), the storage level measurement unit (102) is configured to obtain as the measured value the pressure of the fuel gas, which is measured by the pressure measurement unit (37), and The stop processing is a processing of a stop of the supply of fuel gas to the fuel cell (10) by closing the main shut-off valve (33) when the pressure of the fuel gas obtained by the storage level sensing unit (102) is less than a predetermined lower limit pressure, wherein the predetermined lower limit pressure is the threshold value. [3] Fuel cell system (100) according to claim 2, wherein the control unit (101) is configured to perform, after execution of the stop processing, a confirmation processing of a re-determination of whether the stop processing is to be carried out a number of times by opening the main shut-off valve (33) in response to an operation by a user and re-sensing the pressure of the fuel gas by the pressure sensing unit (37). [4] Fuel cell system (100) according to one of claims 1 to 3, wherein the control unit (101) is configured to prohibit the operation of the fuel cell (10) and to electrically disconnect the secondary battery (86) from the auxiliary machinery (120) when, after connection processing, the measured value detected by the storage level detection unit (102) is less than a predetermined allowable value that is greater than the threshold value. [5] Fuel cell system (100) according to one of claims 1 to 4, wherein the control unit (101) is configured to shut down the operation of the fuel cell (10) and electrically disconnect the secondary battery (86) from the auxiliary machinery (120) after connection processing when the amount of energy accumulated in the secondary battery (86) is less than a predetermined threshold of the amount of accumulated energy which is less than the lower limit of the amount of accumulated energy. [6] Method of controlling a fuel cell system (100), wherein the fuel cell system comprises a fuel cell (10) configured to generate energy by receiving a supply of fuel gas stored in a tank (31) and a secondary battery (86) configured to supply energy to an auxiliary machine (120) used to operate the fuel cell (10), wherein the method comprises: a recording of a measured value representing an extent of the fuel gas stored in the tank (31), a measurement of the amount of energy accumulated in the secondary battery (86), an execution of a halt processing of a halting of the supply of fuel gas to the fuel cell (10) when the measured value is less than a threshold value corresponding to a predetermined lower limit of the stored fuel gas, a disconnect operation involving electrical disconnection of the secondary battery (86) from the auxiliary machinery (120) when the stop operation has been performed and the amount of energy accumulated in the secondary battery (86) is less than a predetermined lower limit of accumulated energy, and a connection processing operation involving an electrical connection of the secondary battery (86) to the auxiliary machinery (120) after the disconnection process has been carried out and a supply of fuel gas to the tank (31) has been recorded.

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