JP7379832B2 - fuel cell system - Google Patents

Description

The present invention relates to a fuel cell system.

A fuel cell system can obtain electric power through an electrochemical reaction between fuel gas and oxidant gas in a fuel cell. A fuel cell system can be used, for example, as a power supply device that supplies electric power to a drive motor of a vehicle that runs using a drive motor that generates power. In fuel cell systems, deterioration of membrane electrode assemblies (referred to as "MEAs") as power generating bodies included in multiple cells (hereinafter also referred to as "single cells") constituting a fuel cell is suppressed. It is desirable to improve the durability of fuel cells.

In Patent Document 1, the current-voltage characteristics of a fuel cell are measured, and based on the measurement results, it is determined whether the performance deterioration is recoverable or irreversible. Regarding this, a technique has been disclosed that improves the durability of fuel cells by performing appropriate recovery processing.

Japanese Patent Application Publication No. 2009-21194

Here, when the voltage of the single cell becomes lower than a certain low voltage (for example, 0.6V), the catalyst of the cathode of the membrane electrode assembly is exposed. Further, when the voltage of a single cell becomes a high voltage exceeding the redox voltage (for example, 0.85 V), melting of the exposed catalyst at the cathode occurs. Therefore, the cell voltage generated by power generation repeatedly fluctuates between the low voltage and the high voltage, which accelerates deterioration of the cathode catalyst and accelerates deterioration of the single cell. In order to suppress such deterioration of the single cell and ensure desired durability, for example, the cell voltage of the single cell may be set to a lower operating limit voltage Vcl (for example, 0.65V to 0.6V) higher than the above-mentioned low voltage. Durability control is performed within a range from 7V) to an operating upper limit voltage Vcu (for example, 0.8V to 0.85V) below the oxidation-reduction voltage. However, the following problems occur in this durability control.

When performance deterioration occurs in the fuel cell, whether it is recoverable performance deterioration or irreversible performance deterioration, if the above durability control is carried out, the drop in operating voltage will be limited and the required level for the fuel cell system will be reduced. The amount of power generation (specifically, the amount of current) that can actually be output from the fuel cell may be lower than the amount of power generation. In this case, the amount of output (specifically, the amount of current) from the secondary battery included in the fuel cell system is increased to compensate for the lack of output from the fuel cell. When the amount of output from the secondary battery increases, a temperature rise occurs in the secondary battery. A secondary battery generally has a limit on its possible output amount depending on its own temperature rise. For this reason, when the temperature of the secondary battery rises, it becomes impossible for the secondary battery to compensate for the shortfall in the output of the fuel cell, and the fuel cell system may not be able to output power corresponding to the required output. . As a result, in a device equipped with a fuel cell system, the output of the device may be limited.

Note that in the fuel cell system of Patent Document 1, it is possible to reduce the possibility of the above problem occurring by attempting to recover from recoverable performance deterioration of the fuel cell. However, in the case of irreversible performance deterioration, the possibility of the above problem occurring cannot be reduced. Therefore, the technology described in Patent Document 1 is insufficient to solve the above problem, and regardless of whether or not it is possible to recover the deteriorated performance of the fuel cell, the fuel cell system will be damaged due to the performance deterioration of the fuel cell. It is desired to improve the problem of not being able to output power corresponding to the required output.

The present disclosure can be realized as the following forms.
A fuel cell system,
a fuel cell stack having a plurality of fuel cells that generate electricity by receiving a reaction gas;
a current measuring unit that measures the output current of the fuel cell stack;
a voltage measuring unit that measures the output voltage of the fuel cell stack;
a secondary battery that compensates for the shortfall in the amount of power generated by the fuel cell stack relative to the amount of power generated required for the fuel cell system;
a temperature measurement unit that measures the temperature of the secondary battery;
a power supply circuit that supplies the power output by the fuel cell stack and the power output by the secondary battery to a load;
The power output by the fuel cell stack is controlled so that the cell voltage represented by the output voltage of the fuel cell stack is equal to or higher than the lower limit voltage, and the temperature of the secondary battery is lower than the upper limit temperature. a control unit that controls the power output by the secondary battery and controls the power supplied from the power supply circuit to the load;
an output acquisition unit that acquires an average value of the output of the secondary battery at regular time intervals;
Equipped with
The control unit resets the value of the lower limit voltage when the average value of the output of the secondary battery is larger than the previous average value of the output of the secondary battery, and in the reset, the lower limit voltage The value is set such that the larger the average value of the output of the secondary battery is , the lower the value is set .
fuel cell system.

According to one aspect of the present disclosure, a fuel cell system is provided. This fuel cell system includes a fuel cell stack having a plurality of cells of fuel cells that receive supply of a reaction gas and generate electricity, a current measuring section that measures an output current of the fuel cell stack, and an output voltage of the fuel cell stack. a voltage measurement unit that measures the temperature of the secondary battery; a temperature measurement unit that measures the temperature of the secondary battery; and a power source that supplies the power output by the fuel cell stack and the power output by the secondary battery to a load. control the power output by the fuel cell stack so that the cell voltage represented by the output voltage of the fuel cell stack is equal to or higher than the lower limit voltage, and the temperature of the secondary battery is lower than the upper limit temperature. a control unit configured to control the power output by the secondary battery so as to control the power supplied from the power supply circuit to the load; and one of an output state of the fuel cell stack and an output state of the secondary battery. a deterioration detection section that detects the degree of deterioration of the fuel cell stack from one side, and the value of the lower limit voltage is set lower as the determined degree of deterioration of the fuel cell stack is greater.
According to this type of fuel cell system, the greater the degree of deterioration of the fuel cell stack, the lower the lower limit voltage value can be lowered to control the power output by the fuel cell stack. The amount of generation can be suppressed. Thereby, it is possible to suppress the temperature of the secondary battery from increasing due to an increase in the output power from the secondary battery. In addition, it is possible to prevent the fuel cell system from being unable to output power corresponding to the power required by the load due to the inability of the secondary battery to compensate for the insufficient output of the fuel cell stack.
The present disclosure can also be implemented in various forms. For example, it can be realized in the form of a fuel cell vehicle equipped with a fuel cell system, a method of controlling the fuel cell system, a computer program for realizing this control method, a storage medium that stores this program, and the like.

FIG. 1 is an explanatory diagram showing a schematic configuration of a fuel cell system in a first embodiment. FIG. 2 is an explanatory diagram showing an example of the relationship between SOC and output limit of a secondary battery. FIG. 3 is an explanatory diagram showing an example of the relationship between the temperature of a secondary battery and output limit. 5 is a flowchart of lower limit voltage control by a lower limit voltage control section. FIG. 3 is an explanatory diagram showing a lower limit voltage set by a lower limit voltage control section. FIG. 2 is a functional block diagram showing a control unit of a fuel cell system in a second embodiment. 5 is a flowchart of lower limit voltage control by a lower limit voltage control section. FIG. 3 is an explanatory diagram showing an example of the relationship between the degree of deterioration and the lower limit voltage. 5 is a flowchart of measuring the lower limit guard count by the lower limit guard count measurement unit. An explanatory diagram showing measurement of the lower limit number of times of guarding. FIG. 3 is a functional block diagram showing a control unit of a fuel cell system in a third embodiment. 5 is a flowchart of lower limit voltage control by a lower limit voltage control section. FIG. 3 is an explanatory diagram showing an example of the relationship between the average output of a secondary battery and a lower limit voltage. 5 is a flowchart of secondary battery output average measurement by a secondary battery output measurement unit.

A. First embodiment:
FIG. 1 is an explanatory diagram showing a schematic configuration of a fuel cell system 10 in the first embodiment. The fuel cell system 10 is mounted on, for example, a vehicle (not shown) (hereinafter also referred to as a "fuel cell vehicle"), and supplies power to auxiliary machines such as a traction motor 20 that generates power for the vehicle and an air compressor 320 (described later). functions as a system for Traction motor 20 is, for example, a three-phase AC motor, and can function as an electric motor or a generator. Traction motor 20 drives the fuel cell vehicle using electric power supplied from fuel cell stack 100 and secondary battery (also referred to as "BAT") 550 via power supply circuit 500, which will be described later.

The fuel cell system 10 includes a fuel cell stack 100, an anode side gas supply/discharge mechanism 200, a cathode side gas supply/discharge mechanism 300, a fuel cell circulation cooling mechanism 400, a power supply circuit 500, a secondary battery 550, and a control system. 700.

The fuel cell stack 100 is a polymer electrolyte fuel cell, and has a cell stack in which a plurality of single cells 110 serving as power generating bodies are stacked. Each unit cell 110 uses a fuel gas supplied to the anode side catalyst electrode layer of the membrane electrode assembly provided with a solid polymer electrolyte membrane in between, and an oxidant gas supplied to the cathode side catalyst electrode layer as reaction gases. The electrochemical reaction used generates electricity. In this embodiment, the fuel gas is hydrogen gas and the oxidant gas is air. The catalyst electrode layer includes a catalyst, for example, carbon particles supporting platinum (Pt) and an electrolyte. In the single cell 110, a gas diffusion layer made of a porous material is arranged outside the catalyst electrode layer on both electrode sides. As the porous body, for example, carbon porous bodies such as carbon paper and carbon cloth, and metal porous bodies such as metal mesh and foamed metal are used. Inside the fuel cell stack 100, a manifold (not shown) for circulating fuel gas, oxidant gas, and cooling medium is formed along the stacking direction. The fuel cell stack 100 includes a pair of electrode plates 111 that sandwich both ends of the cell stack. The pair of electrode plates 111 functions as a general electrode in the fuel cell stack 100.

The anode side gas supply/discharge mechanism 200 corresponds to a "fuel gas supply section" and supplies fuel gas to the fuel cell stack 100, discharges anode off-gas from the fuel cell stack 100, and discharges fuel gas in the anode off-gas. Circulating supply to the fuel cell stack 100 is performed.

The anode side gas supply and discharge mechanism 200 includes a tank 210, a cutoff valve 220, a pressure regulating valve 221, an injector 222, a gas-liquid separator 250, a circulation pump 240, a purge valve 260, and a fuel gas supply channel. 231, a first anode off-gas discharge passage 232, a gas circulation passage 233, a second anode off-gas discharge passage 262, a first pressure sensor 271, a second pressure sensor 272, a third pressure sensor 273, Equipped with

Tank 210 stores high-pressure hydrogen gas as fuel gas. Tank 210 supplies fuel gas to fuel cell stack 100 via fuel gas supply channel 231 . The cutoff valve 220 is arranged near the fuel gas supply port of the tank 210 and switches between execution and stopping of the supply of fuel gas from the tank 210. The pressure regulating valve 221 is arranged downstream of the cutoff valve 220 and upstream of the injector 222 in the fuel gas supply flow path 231 . The pressure regulating valve 221 adjusts its own upstream pressure (also called "primary pressure") to its own downstream pressure (also called "secondary pressure") that is set in advance. The injector 222 is disposed downstream of the pressure regulating valve 221 in the fuel gas supply channel 231 and injects fuel gas into the fuel cell stack 100. At this time, by adjusting the fuel gas injection cycle and injection duty (the ratio of time for injecting hydrogen gas per cycle of the injection cycle) of the fuel gas in the injector 222, the amount of fuel gas supplied to the fuel cell stack 100 and the injection duty are adjusted. Pressure is regulated. Note that the first pressure sensor 271 measures the primary pressure, the second pressure sensor 272 measures the secondary pressure, and the third pressure sensor 273 measures the downstream pressure of the injector 222.

The gas-liquid separator 250 is disposed in the first anode off-gas discharge passage 232, and separates the liquid contained in the anode off-gas discharged from the fuel cell stack 100 and discharges it to the second anode off-gas discharge passage 262. The anode off-gas after the liquid has been separated is discharged into the gas circulation path 233. Further, the gas-liquid separator 250 stores the liquid separated from the anode off-gas, and discharges the stored liquid to the second anode off-gas discharge channel 262 when the purge valve 260 is opened. The liquid contained in the anode off-gas is, for example, water produced on the cathode side by an electrochemical reaction in each unit cell 110, and water that permeates through the electrolyte membrane to the anode side. The anode off-gas after the liquid is separated includes hydrogen gas that was not used in the electrochemical reaction in each unit cell 110 and hydrogen gas that permeates from the cathode side to the anode side through the solid polymer membrane in each unit cell 110. Nitrogen gas may be included.

The circulation pump 240 is arranged in the gas circulation path 233 and sends the anode off-gas discharged from the gas-liquid separator 250 to the fuel gas supply path 231. The purge valve 260 is disposed in the second anode off-gas discharge passage 262 and discharges the liquid separated by the gas-liquid separator 250 to the second anode off-gas discharge passage 262 when opened. At this time, a part of the anode off-gas is also discharged to the second anode off-gas exhaust passage 262 via the purge valve 260.

The fuel gas supply channel 231 communicates with a fuel gas supply manifold (not shown) provided within the fuel cell stack 100. The fuel gas supply channel 231 is supplied with fuel gas from the injector 222 and also supplied with anode off gas from the circulation pump 240. The anode off-gas supplied from the circulation pump 240 mainly contains hydrogen gas discharged without being used by each unit cell 110 , and this hydrogen gas is returned to the fuel gas supply channel 231 to be circulated and supplied to the fuel cell stack 100 . By doing so, fuel efficiency can be improved. The first anode off-gas discharge passage 232 communicates with a manifold for discharging anode off-gas (not shown) provided in the fuel cell stack 100, and discharges the anode off-gas discharged from this manifold to the outside of the fuel cell stack 100. , to the gas-liquid separator 250. One end of the second anode off-gas exhaust passage 262 is connected to the purge valve 260, and the other end is connected to a cathode off-gas exhaust passage 331, which will be described later. The second anode off-gas discharge passage 262 supplies liquid water and anode off-gas discharged from the gas-liquid separator 250 to the cathode off-gas discharge passage 331 when the purge valve 260 is opened. As will be described later, the cathode off gas exhaust flow path 331 discharges the cathode off gas mainly consisting of air from the second anode off gas exhaust flow path 262, and the anode off gas containing hydrogen gas is diluted by the cathode off gas. and is discharged to the outside.

The cathode-side gas supply/discharge mechanism 300 corresponds to an "oxidant gas supply section" and supplies an oxidant gas to the fuel cell stack 100 and discharges cathode off-gas from the fuel cell stack 100. The cathode side gas supply and discharge mechanism 300 includes an oxidant gas supply section 391 and a cathode off-gas discharge section 392.

The oxidizing gas supply section 391 supplies air as an oxidizing gas to the fuel cell stack 100. The oxidizing gas supply section 391 includes an oxidizing gas supply channel 330, a temperature sensor 305, an air cleaner 310, an air compressor 320, a cathode bypass channel 333, and an air distribution valve 340.

The oxidizing gas supply channel 330 guides air as an oxidizing gas taken in from the atmosphere to an oxidizing gas supply manifold (not shown) provided in the fuel cell stack 100. Temperature sensor 305 measures the temperature of the air taken into oxidant gas supply portion 391, that is, measures the outside air temperature. The air cleaner 310 is disposed in the oxidizing gas supply channel 330, removes foreign matter such as dust from the air using a filter provided therein, and supplies the air after the foreign matter has been removed to the air compressor 320. The air compressor 320 is arranged in the oxidizing gas supply channel 330, compresses the air supplied from the air cleaner 310, and supplies the compressed air to the downstream side. The cathode bypass channel 333 is connected to the oxidant gas supply channel 330 downstream of the air compressor 320 and upstream of the fuel cell stack 100 in the oxidant gas supply channel 330 . The cathode bypass passage 333 guides at least a portion of compressed air supplied from the air compressor 320 to a cathode off-gas discharge passage 331, which will be described later, depending on the opening degree of the air distribution valve 340. The air distribution valve 340 is arranged at a connection point between the oxidizing gas supply channel 330 and the cathode bypass channel 333. The air distribution valve 340 adjusts the flow rate of the air supplied from the air compressor 320 to the fuel cell stack 100 and the flow rate supplied to the cathode bypass passage 333 .

The cathode offgas exhaust portion 392 includes a cathode offgas exhaust passage 331 , a cathode backpressure valve 350 , and a muffler 360 .

The cathode off-gas discharge passage 331 is connected to a cathode off-gas discharge manifold (not shown) provided in the fuel cell stack 100, and guides cathode off-gas and liquid water discharged from this manifold to the outside. The cathode back pressure valve 350 is arranged upstream of the connection point between the cathode off-gas discharge passage 331 and the above-mentioned cathode bypass passage 333. The cathode back pressure valve 350 adjusts the back pressure on the cathode side of the fuel cell stack 100 by adjusting its opening degree. The muffler 360 is disposed on the downstream side of the connection point with the second anode off-gas exhaust passage 262 in the cathode off-gas exhaust passage 331 . The muffler 360 reduces exhaust noise of the mixed gas.

The fuel cell circulation cooling mechanism 400 adjusts the temperature of the fuel cell stack 100 by circulating a cooling medium through the fuel cell stack 100. In this embodiment, antifreeze is used as the cooling medium, but any medium such as pure water may be used instead of antifreeze. The fuel cell circulation cooling mechanism 400 includes a radiator 410, a temperature sensor 420, a coolant discharge flow path 442, a coolant supply flow path 441, a coolant bypass flow path 443, a coolant distribution valve 444, and a cooling medium distribution valve 444 for circulation. and a pump 430.

The radiator 410 is connected to a cooling medium discharge passage 442 and a cooling medium supply passage 441, and cools the cooling medium flowing from the cooling medium discharge passage 442 by blowing air from an electric fan (not shown). It is discharged to the cooling medium supply channel 441. The temperature sensor 420 is arranged near the connection point with the fuel cell stack 100 in the coolant discharge flow path 442 and measures the temperature of the coolant flowing through the coolant discharge flow path 442 . The temperature measured by temperature sensor 420 may be treated as the temperature of fuel cell stack 100. The coolant discharge passage 442 is connected to a coolant discharge manifold (not shown) provided within the fuel cell stack 100. Further, the coolant discharge flow path 442 is connected to a coolant bypass flow path 443 via a coolant distribution valve 444 . Coolant discharge flow path 442 guides the coolant discharged from fuel cell stack 100 to radiator 410 or coolant bypass flow path 443 . One end of the coolant supply channel 441 is connected to the radiator 410. The other end of the coolant supply channel 441 is connected to a coolant supply manifold (not shown) provided within the fuel cell stack 100. One end of the coolant bypass flow path 443 is connected to the coolant distribution valve 444, and the other end is connected to the coolant supply flow path 441. At least a portion of the coolant discharged from the fuel cell stack 100 is guided to the coolant bypass flow path 443 depending on the opening degree of the coolant distribution valve 444. The coolant distribution valve 444 adjusts the flow rate of the coolant discharged from the fuel cell stack 100 that is supplied to the radiator 410 and the flow rate that is supplied to the coolant bypass flow path 443 . The circulation pump 430 is installed downstream of the connection point with the coolant distribution valve 444 in the coolant supply channel 441 . The circulation pump 430 adjusts the flow rate of the coolant in the coolant circulation channel formed by the radiator 410, the coolant supply channel 441, the coolant channel inside the fuel cell stack 100, and the coolant discharge channel 442. do.

The power supply circuit 500 supplies power to auxiliary equipment such as the traction motor 20 and the air compressor 320 from at least one of the fuel cell stack 100 and the secondary battery 550. Further, the power supply circuit 500 adjusts the output current (hereinafter referred to as "FC current") of the fuel cell stack 100. Further, the power supply circuit 500 controls charging of the secondary battery 550. The power supply circuit 500 includes a fuel cell control converter 530, an inverter (also referred to as "INV") 520, a secondary battery control converter 560, a secondary battery temperature sensor 552, and a secondary battery measurement section ("BAT measurement"). 555, a current measuring section 570, and a cell monitor 580.

Fuel cell control converter 530 is a DC/DC converter, and boosts the output voltage of fuel cell stack 100. Furthermore, the fuel cell control converter 530 adjusts the FC current by adjusting the switching frequency of the built-in switching element according to instructions from the control unit 700. The current measurement unit 570 measures the FC current flowing through the wiring connecting the electrode plate 111 of the fuel cell stack 100 and the fuel cell control converter 530. The cell monitor 580 corresponds to a "voltage measuring section" and measures the voltage of each single cell 110 (also referred to as "cell voltage") and the voltage of the fuel cell stack 100 (also referred to as "stack voltage").

The secondary battery 550 is constituted by a lithium ion battery, and functions as a power supply source in the fuel cell system 10 together with the fuel cell stack 100. Note that instead of the lithium ion battery, any other type of battery such as a nickel-metal hydride battery may be used.

Secondary battery control converter 560 is a DC/DC converter, and boosts the output voltage of secondary battery 550. Further, the secondary battery control converter 560 reduces the voltage of at least one of the regenerated power of the traction motor 20 and the output power of the fuel cell stack 100 and supplies the voltage to the secondary battery 550 . Inverter 520 is electrically connected to fuel cell stack 100 and secondary battery 550, respectively, and converts the DC voltage output from fuel cell stack 100 and secondary battery 550 into AC voltage. The converted AC voltage is supplied to the traction motor 20. Furthermore, the inverter 520 converts the AC voltage of the regenerated power output from the traction motor 20 into a DC voltage, and outputs the DC voltage to the secondary battery control converter 560.

The secondary battery measurement unit 555 detects the temperature of the secondary battery 550 from the output value of the secondary battery temperature sensor 552. Further, the secondary battery measurement unit 555 measures the current flowing through the wiring connecting the secondary battery 550 and the secondary battery control converter 560, and also measures the voltage between the wirings. The temperature, current, and voltage of the secondary battery 550 measured by the secondary battery measurement unit 555 are supplied to the control unit 700 and used for controlling the secondary battery control converter 560 in the control unit 700. The secondary battery measuring section 555 corresponds to a "temperature measuring section" that measures the temperature of the secondary battery 550.

The control unit 700 is configured as a computer including a microprocessor and a storage device such as a ROM (Read Only Memory) or a RAM (Ramdom Access Memory). The microprocessor operates as a functional unit that controls the operation of the fuel cell system 10 by executing a control program stored in the ROM in advance using the RAM. The control unit 700 includes the above-mentioned shutoff valve 220, pressure sensors 271 to 273, circulation pump 240, purge valve 260, air compressor 320, air distribution valve 340, cathode back pressure valve 350, motor cooling distribution valve 370, and circulation pump 430. , a coolant distribution valve 444, an inverter 520, a fuel cell control converter 530, and a secondary battery control converter 560, respectively, and control these. Further, the control unit 700 is electrically connected to the pressure sensors 271 to 273, the temperature sensor 305, the secondary battery measurement unit 555, the current measurement unit 570, and the cell monitor 580, respectively, and obtains the measured values of these sensors.

Note that FIG. 1 shows a system control section 710, an FC control section 720, a BAT control section 730, an FC characteristic measurement section 740, a lower limit voltage control section 750, and a storage section 760 as functional sections of the control section 700. There is. The storage unit 760 is composed of a nonvolatile rewritable storage device.

The system control unit 710 is a functional unit that controls the entire system, and controls the operations of the FC control unit 720 and the BAT control unit 730.

The FC control unit 720 controls the anode side gas supply/discharge mechanism 200, the cathode side gas supply/discharge mechanism 300, and the fuel cell circulation cooling mechanism 400 to control power generation by the fuel cell stack 100, and also controls the fuel cell control converter 530. control the behavior of More specifically, the FC control unit 720 controls the fuel cell stack 100 so that the voltage of the single cell 110 represented by the output voltage of the fuel cell stack 100 falls within the operating range defined by the lower limit voltage and the upper limit voltage. Controls the power output by.

The BAT control unit 730 controls the secondary battery control converter 560 to control charging and discharging of the secondary battery 550. FIG. 2 is an explanatory diagram showing an example of the relationship between the SOC of the secondary battery 550 and the output limit. FIG. 3 is an explanatory diagram showing an example of the relationship between the temperature of the secondary battery 550 and the output limit. SOC means the state of charge [%] of the secondary battery. Each of these relationships is stored in the storage unit 760 as a table. The BAT control unit 730 acquires the output limit Pbt_soc[W] corresponding to the SOC determined from the voltage, current, and temperature of the secondary battery 550 acquired by the secondary battery measuring unit 555 from the table. The BAT control unit 730 also obtains the output limit Pbt_tmp[W] corresponding to the temperature of the secondary battery 550 from the table. Then, the BAT control unit 730 controls the operation of the secondary battery control converter 560 so that the output of the secondary battery 550 is equal to or less than the smaller value of the acquired output limit Pbt_soc and the output limit Pbt_tmp. . Thereby, the secondary battery 550 is controlled so that its temperature operates below the upper limit temperature.

During the power generation operation of the fuel cell stack 100, the FC characteristic measuring section 740 uses the measured values by the current measuring section 570 and the cell monitor 580 to determine the current-voltage characteristic ("IV characteristic") as the output characteristic of the fuel cell stack 100. (also called). Note that the initial IV characteristics are stored in the storage section 760.

The lower limit voltage control unit 750 controls the lower limit voltage of the fuel cell stack 100 according to the degree of deterioration of the fuel cell stack 100 detected as described below.

FIG. 4 is a flowchart of lower limit voltage control by the lower limit voltage control section 750. For example, the lower limit voltage control unit 750 measures the IV characteristics using the FC characteristic measurement unit 740 at the time of system startup, after a certain period of operation time, etc., and after the measurement results are stored in the storage unit 760, the following steps are performed. Execute the lower limit voltage control described in .

First, in step S<b>101 , the lower limit voltage control unit 750 sets the maximum output power Pmax of the fuel cell stack 100 stored in advance in the storage unit 760 and the maximum output power Pmax of the fuel cell stack 100 that is stored in the storage unit 760 after being acquired during the previous IV characteristic measurement. The maximum value of the FC current (hereinafter also referred to as “FC maximum current”) Ibmax is read from the storage unit 760. Note that hereinafter, the FC maximum current Ibmax acquired during the previous IV characteristic measurement is also referred to as "previous FC maximum current Ibmax(p)." Further, the maximum output power Pmax is the output when the initially set lower limit voltage VLo and the output voltage Vfc are the lower limit voltage VLo in an initial state where the fuel cell stack 100 has no deterioration before the start of operation of the fuel cell system 10. It is the product of the current Ifc and the value Iomax (also referred to as "initial FC maximum current Iomax"). Further, the initial value of the previous FC maximum current Ibmax(p) is the initial FC maximum current Iomax. Note that the output voltage Vfc of the fuel cell stack 100 is the voltage of one single cell 110 of the fuel cell stack 100 (also referred to as "cell voltage"). This cell voltage is an average value obtained by dividing the voltage between the electrode plates 111 of the fuel cell stack 100 measured by the cell monitor 580 (see FIG. 1) by the number of single cells 110, and is usually 0.65V. -0.85V. Further, the lower limit voltage VL is the lower limit voltage of the cell voltage, and is usually set within the range of 0.65V to 0.7V. The initial lower limit voltage VLo is normally set to 0.7V.

Next, in step S102, the lower limit voltage control unit 750 sets the maximum output power Pmax to The corresponding output current Ifc is obtained as the current maximum output current Ibmax (also referred to as "current FC maximum current Ibmax") (step S102).

Here, the fact that the current FC maximum current Ibmax is larger than the previous FC maximum current Ibmax(p) (step S103: YES) means that the degree of deterioration of the fuel cell stack 100 is increasing. Therefore, in this case, the lower limit voltage control unit 750 divides the maximum output power Pmax by the current FC maximum current Ibmax indicating the degree of deterioration of the fuel cell stack 100 in step S104, thereby determining the current FC maximum current Ibmax. The value of the output voltage Vfc of the fuel cell stack 100 that can be outputted is calculated as the lower limit voltage VL. Then, in step S105, the lower limit voltage control section 750 stores the calculated lower limit voltage VL in the storage section 760, and ends the process. On the other hand, if the current FC maximum current Ibmax is less than or equal to the previous FC maximum current Ibmax(p) (step S103: NO), the degree of deterioration of the fuel cell stack 100 has not become large, so the lower limit voltage control unit 750 The process ends without calculating the lower limit voltage VL.

FIG. 5 is an explanatory diagram showing the lower limit voltage VL set by the lower limit voltage control section 750. The upper graph in FIG. 5 is a graph showing the IV characteristics of the fuel cell stack 100, and the lower graph in FIG. 5 is a graph showing the IP characteristics calculated from the upper IV characteristics. Note that the IV characteristic CIVo and the IP characteristic CIPo shown by solid lines in FIG. 5 indicate characteristics in an initial state, and are stored in advance in the storage unit 760. Further, the IV characteristic CIVb shown by the dashed line in FIG. 5 shows an example of the IV characteristic measured by the FC characteristic measuring section 740 in a state where the fuel cell system 10 is operated and the fuel cell stack 100 is deteriorated. Further, the IP characteristic CIPb indicated by the dashed line indicates the IP characteristic calculated from the IV characteristic CIVb. Note that the measurement of the IV characteristic by the FC characteristic measurement unit 740 is performed by measuring a plurality of output voltages Vfc and output current Ifc in close time periods while the fuel cell stack 100 is generating power. . At this time, the output voltage Vfc lower than the currently set lower limit voltage VL and the corresponding output current Ifc are calculated using an extrapolation method.

As the deterioration of the fuel cell stack 100 progresses, the output performance decreases as compared to the IV characteristic CIVo and the IP characteristic CIPo in the initial state, as shown in the IV characteristic CIVb and the IP characteristic CIPb shown in FIG. Therefore, the fuel cell stack 100 was able to output the initial FC maximum current Iomax and the maximum output power Pmax at the lower limit voltage VLo in the initial state, but at the lower limit voltage VLo in the degraded state, the initial FC maximum Current Iomax and maximum output power Pmax cannot be output.

Therefore, in the lower limit voltage control of the first embodiment (see FIG. 4), the current FC maximum current Ibmax corresponding to the maximum output power Pmax is determined based on the IP characteristic CIPb of the fuel cell stack 100 in a deteriorated state. Then, the value VLb of the output voltage Vfc that makes it possible to output the maximum output power Pmax and the current FC maximum current Ibmax is determined and set as the lower limit voltage VL. Thereby, even if the deterioration of the fuel cell stack 100 progresses, the lower limit voltage VL can be set lower as the degree of deterioration increases. As a result, by limiting the output voltage Vfc by the lower limit voltage VL, it is possible to reduce the occurrence and amount of insufficient output of the fuel cell stack 100. In order to compensate for the shortfall in the output of the fuel cell stack 100, it is possible to reduce the need for the secondary battery 550 to increase and output electric power corresponding to the shortfall. Thereby, it is possible to suppress a rise in temperature of the secondary battery 550 that occurs due to an increase in the output of the secondary battery 550. As a result, the temperature of the secondary battery 550 rises, causing an output restriction of the secondary battery 550 (see FIG. 3), making it impossible for the secondary battery 550 to compensate for the output shortfall of the fuel cell stack 100. Therefore, it is possible to prevent the fuel cell system 10 from being unable to output the electric power required by the load such as the traction motor 20. This makes it possible to suppress the deterioration in drivability felt by the driver.

Note that, as explained in the assignment, the value of the lower limit voltage VL is set in order to prevent the voltage from falling below a certain low voltage (for example, 0.6 V) at which exposure of the catalyst of the cathode of the membrane electrode assembly occurs. Considering the margin, the initial value VLo of the lower limit voltage VL is set to about 0.7V. Therefore, even if the value of the lower limit voltage VL is lower than the initial value VLo, as long as the value is higher than the constant low voltage, the influence on the deterioration of the cathode catalyst can be suppressed. Therefore, as described above, by setting the lower limit voltage VL to a value lower than the initial value VLo depending on the degree of deterioration, the above-described effect can be obtained although the margin of the lower limit voltage VL becomes smaller.

Note that in the first embodiment described above, the control section 700, more specifically, the FC control section 720 and the BAT control section 730 correspond to the "control section". Further, the lower limit voltage control section 750 corresponds to a "deterioration detection section", and the FC maximum current Ibmax corresponds to "an output state of the fuel cell stack".

B. Second embodiment:
FIG. 6 is a functional block diagram showing a control unit 700B of a fuel cell system 10B in the second embodiment. In FIG. 6, the configuration other than the control unit 700B is the same as the fuel cell system 10 of the first embodiment (see FIG. 1), so illustration and description will be omitted.

The control section 700B includes a lower limit voltage control section 750B in place of the lower limit voltage control section 750 of the control section 700 of the first embodiment, and also includes a lower limit guard frequency measuring section 755B. The lower limit guard count measuring unit 755B measures the number of times the output voltage of the fuel cell stack 100 is limited by the lower limit voltage (hereinafter also referred to as "lower limit guard count"), as described below. The lower limit voltage control unit 750B controls the lower limit voltage of the fuel cell stack 100 according to the degree of deterioration of the fuel cell stack 100 detected from the lower limit guard count, as described below.

FIG. 7 is a flowchart of lower limit voltage control by the lower limit voltage control section 750B. The lower limit voltage control unit 750B executes the lower limit voltage control described below, for example, at the time of system startup or at a fixed time period.

First, in step S111, the lower limit voltage control unit 750B selects the operating time Td stored in the storage unit 760 and the previous degree of deterioration Kg( p) and are read from the storage unit 760.

Next, if the system is in the system activation state meaning that power can be supplied from the fuel cell stack 100 (step S112: YES), the lower limit voltage control unit 750B controls the operating time Td for a certain period of time dt in step S113. is added, and the operation time Td after the addition is stored in the storage unit 760. The lower limit voltage control unit 750B then measures the operating time Td in steps S112 to S114 until the operating time Td becomes larger than the predetermined value Tr (step S115: NO). The predetermined value Tr is a value determined depending on the deterioration rate of the fuel cell stack 100, and is set to a time at which the progress of deterioration appears as a change in the IV characteristics. This predetermined value Tr depends on the structure of the single cell 110 and the operating method of the fuel cell system 10.

When the operating time Td becomes larger than the predetermined value Tr (step S115: YES), in step S116, the lower limit voltage control unit 750B reads the lower limit guard number Nt from the storage unit 760, and in step S117, the lower limit guard number Nt By dividing by the operating time Td, the value of the lower limit guard count per unit time is calculated as the current degree of deterioration Kg. Note that the lower limit guard number Nt will be explained later in the lower limit guard number measurement by the lower limit guard number measurement unit 755B.

Here, the fact that the current degree of deterioration Kg is greater than the previous degree of deterioration Kg(p) (step S118: YES) means that the degree of deterioration of the fuel cell stack 100 is increasing. Therefore, in this case, the lower limit voltage control section 750B determines the lower limit voltage VL corresponding to the current degree of deterioration Kg in step S119 using a table stored in advance in the storage section 760.

FIG. 8 is an explanatory diagram showing an example of the relationship between the degree of deterioration Kg and the lower limit voltage VL. Information indicating this relationship is stored in advance in the storage unit 760 as a table. The lower limit voltage control unit 750B can use a table to determine, for example, the value VLb of the lower limit voltage VL corresponding to the value Kgb of the current degree of deterioration Kg.

Next, in step S120, the lower limit voltage control unit 750B stores the calculated current degree of deterioration Kg as the previous degree of deterioration Kg(p) in the storage unit 760, and also stores the determined lower limit voltage VL in the storage unit 760. . Then, the lower limit voltage control unit 750B turns on the lower limit voltage determination flag in step S121, resets the operating time Td stored in the storage unit 760 in step S122, and ends the process.

On the other hand, if the current degree of deterioration Kg is less than or equal to the previous degree of deterioration Kg(p) (step S118: NO), the degree of deterioration of the fuel cell stack 100 has not become large. The unit 750B performs steps S121 and S122 without performing steps S119 and S120, and ends the process.

FIG. 9 is a flowchart of the lower limit guard count measurement by the lower limit guard count measurement unit 755B. The lower limit guard number measuring unit 755B executes the lower limit guard number measurement, which will be described below, at a fixed time period, for example.

First, in step S131, the lower limit guard count measuring unit 755B reads the lower limit guard count Nt stored in the storage unit 760. Then, the lower limit guard number measuring unit 755B determines whether the required power Pfcrq for the fuel cell stack 100 is larger than the predetermined value Pfcr and until the output voltage Vfc of the fuel cell stack 100 becomes less than the guard determination voltage Vd (step S132 :NO), wait. Then, the lower limit guard count measuring unit 755B waits until the output voltage Vfc of the fuel cell stack 100 becomes larger than the guard determination voltage Vd (step S133: NO). Then, when the output voltage Vfc of the fuel cell stack 100 becomes larger than the guard determination voltage Vd (step S133: YES), the lower limit guard number measuring unit 755B adds the number 1 to the lower limit guard number Nt in step S134. , in step S135, the lower limit guard count Nt is stored in the storage unit 760.

FIG. 10 is an explanatory diagram showing the measurement of the lower limit guard count. The guard determination voltage Vd is a voltage obtained by adding the margin voltage Vα to the currently set lower limit voltage VL. When the output voltage Vfc becomes lower than the guard determination voltage Vd, this indicates that the voltage is limited by the lower limit voltage VL. If the output voltage Vfc becomes larger than the guard determination voltage Vd after this state continues, this indicates that the output voltage Vfc has escaped from the state where it is limited by the lower limit voltage VL. Note that the margin voltage Vα is a margin for eliminating erroneous determination due to voltage variations that may occur depending on the control response while the output voltage Vfc is limited by the lower limit voltage VL. Therefore, in steps S132 to S134 in FIG. 9, when the output voltage Vfc becomes less than the guard judgment voltage Vd and then becomes larger than the guard judgment voltage Vd, the output voltage Vfc is limited by the lower limit voltage VL. This is to measure that the condition has occurred once.

Note that the condition that the required power Pfcrq is larger than the predetermined value Pfcr in step S132 excludes the following conditions. That is, in a state where there is no request for power supply to the load such as the traction motor 20 (see FIG. 1), for example, intermittently in order to maintain the output voltage Vfc of the fuel cell stack 100 within a certain voltage range. This excludes a decrease in the output voltage Vfc that occurs in a state of intermittent operation in which a small amount of power generation is executed. For example, the predetermined value Pr is set to a power larger than the power of minute power generation in order to exclude the power of minute power generation performed in intermittent operation.

Then, the lower limit guard number measuring unit 755B repeats steps S131 to S135 until the lower limit voltage determination flag is turned ON in step S121 of FIG. 7 (step S136: NO) to measure the lower limit guard number Nt. Execute. On the other hand, when the lower limit voltage determination flag is turned ON (step S136: YES), the lower limit guard count measurement unit 755B resets the lower limit guard count Nt stored in the storage unit 760 in step S137, and The voltage determination flag is turned OFF and the process ends.

As described above, in the second embodiment, the lower limit guard count that occurs per unit time is determined as the degree of deterioration Kg, and the lower limit voltage VL corresponding to the degree of deterioration Kg is determined (see FIG. 8). Thereby, even if the deterioration of the fuel cell stack 100 progresses, the lower limit voltage VL can be set lower as the degree of deterioration increases. This makes it possible to obtain the same effects as in the first embodiment.

Note that in the second embodiment described above, the control unit 700B, more specifically, the FC control unit 720 and the BAT control unit 730 correspond to the “control unit”. Further, the lower limit voltage control section 750B corresponds to a "deterioration detection section", and the lower limit guard number Nt corresponds to "an output state of the fuel cell stack".

C. Third embodiment:
FIG. 11 is a functional block diagram showing a control unit 700C of a fuel cell system 10C in the third embodiment. In FIG. 11, the configuration other than the control unit 700C is the same as the fuel cell system 10 of the first embodiment (see FIG. 1), so illustration and description will be omitted.

The control unit 700C includes a lower limit voltage control unit 750C in place of the lower limit voltage control unit 750 of the control unit 700 of the first embodiment, and also includes a secondary battery output measurement unit 758C. The secondary battery output measurement unit 758C measures the average secondary battery output that indicates the output state of the secondary battery 550, as described below. The lower limit voltage control unit 750C controls the lower limit voltage of the fuel cell stack 100 according to the degree of deterioration of the fuel cell stack 100 detected from the average output of the secondary battery, as described below.

FIG. 12 is a flowchart of lower limit voltage control by the lower limit voltage control section 750C. The lower limit voltage control unit 750C executes the lower limit voltage control described below, for example, at the time of system startup or at a fixed time period.

First, in step S141, the lower limit voltage control unit 750C selects the operating time Td stored in the storage unit 760 and the previous secondary battery output acquired when the previous lower limit voltage control was executed and stored in the storage unit 760. The average Pbm(p) is read from the storage unit 760.

Next, when the system is in the startup state (step S142: YES), the lower limit voltage control unit 750C adds a certain time dt to the operating time Td in step S143, and stores the added operating time Td in the storage unit 760. to be memorized. The lower limit voltage control unit 750B then measures the operating time Td in steps S142 to S144 until the operating time Td becomes larger than the predetermined value Tr (step S145: NO). Note that the system startup state and the predetermined value Tr are the same as in the second embodiment.

When the operating time Td becomes larger than the predetermined value Tr (step S145: YES), the lower limit voltage control unit 750C reads the secondary battery output average Pbm from the storage unit 760 in step S146. The secondary battery output average Pbm will be explained in the secondary battery output average measurement by the secondary battery output measuring section 758C, which will be described later.

Here, the fact that the current average secondary battery output Pbm is larger than the previous average secondary battery output Pbm(p) (step S147: YES) means that the degree of deterioration of the fuel cell stack 100 is increasing. do. Therefore, in this case, the lower limit voltage control section 750C determines the lower limit voltage VL corresponding to the current average secondary battery output Pbm in step S148 using a table stored in advance in the storage section 760.

FIG. 13 is an explanatory diagram showing an example of the relationship between the secondary battery output average Pbm and the lower limit voltage VL. Information indicating this relationship is stored in advance in the storage unit 760 as a table. The lower limit voltage control unit 750C can use a table to determine, for example, the value VLb of the lower limit voltage VL corresponding to the value Pbmb of the current secondary battery output average Pbm.

Next, in step S149 of FIG. 12, the lower limit voltage control unit 750C stores the current secondary battery output average Pbm as the previous secondary battery output average Pbm(p) in the storage unit 760, and also sets the determined lower limit voltage VL. It is stored in the storage unit 760. Then, the lower limit voltage control unit 750C turns on the lower limit voltage determination flag in step S150, resets the operating time Td stored in the storage unit 760 in step S151, and ends the process.

On the other hand, if the current average secondary battery output Pbm is less than or equal to the previous average secondary battery output Pbm(p) (step S147: YES), the degree of deterioration of the fuel cell stack 100 has not become large, so in this case In this case, the lower limit voltage control section 750C performs steps S150 and S151 without performing steps S148 and S149, and ends the process.

FIG. 14 is a flowchart of secondary battery output average measurement by the secondary battery output measurement unit 758C. The secondary battery output measurement unit 758C executes secondary battery output average measurement, which will be described below, at a fixed time period, for example.

First, in step S161, the secondary battery output measurement unit 758C reads the average secondary battery output Pbm stored in the storage unit 760. Then, when the required power Prq for the fuel cell system 10 is larger than the predetermined value Pr (step S162: YES), the secondary battery output measurement unit 758C calculates the average secondary battery output Pbm in step S163, and calculates the average secondary battery output Pbm in step S164. The average secondary battery output Pbm calculated in is stored in the storage unit 760 as the current average secondary battery output Pbm. Then, the secondary battery output measurement unit 758C repeats steps S161 to S164 until the lower limit voltage determination flag is turned ON in step S150 of FIG. 12 (step S165: NO), and calculates the average secondary battery output Pb Perform measurements. On the other hand, when the lower limit voltage determination flag is set to ON (step S136: YES), the secondary battery output measuring unit 758C calculates the current average secondary battery output Pbm stored in the storage unit 760 in step S166. At the same time, the lower limit voltage determination flag is turned OFF, and the process ends.

Here, the secondary battery output average Pbm in step S163 is determined by the time taken until the lower limit voltage determination flag is turned ON, that is, the time taken until the progress of deterioration of the fuel cell stack 100 appears as a change in the IV characteristics. , is the average value of power output from the secondary battery 550. For example, if the output from the secondary battery 550 is 10 kW, 10 kW, 10 kW, 10 kW, 10 kW, 20 kW, 20 kW, 20 kW, 20 kW, 20 kW during the operation time Td of 160 msec with a calculation cycle of 16 msec, then The average output Pbm of the next battery is calculated to be 15 kW.

Further, the condition that the requested power Prq is larger than the predetermined value Pr in step S162 is based on the following reason. In other words, the average secondary battery output is calculated based on a state in which the fuel cell system 10 supplies more power to the load, the fuel cell stack 100 becomes insufficient in output, and the output from the secondary battery 550 increases. This is because it needs to be carried out. This is because unless this is done, it is difficult to determine whether the secondary battery output has increased due to deterioration of the fuel cell stack 100 based on the calculated average secondary battery output. For example, if the secondary battery output is averaged even during idling operation where the secondary battery output does not increase, the average secondary battery output will become smaller during operation with a lot of idling, and this will become an indicator of deterioration of the fuel cell stack 100. Must not be. From the above, the predetermined value Pr is set to, for example, the output power when the fuel cell stack 100 generates power at the lower limit voltage VL.

As described above, in the third embodiment, the average secondary battery output Pbm is determined, and the lower limit voltage VL corresponding to the average secondary battery output Pbm is determined. An increase in the average secondary battery output Pbm indicates that the deterioration of the fuel cell stack 100 progresses and that the output shortage of the fuel cell stack 100 increases. Therefore, even if the deterioration of the fuel cell stack 100 progresses and the degree of deterioration increases, the lower limit voltage VL can be set lower as the average secondary battery output Pbm increases. This makes it possible to obtain the same effects as in the first and second embodiments.

Note that in the third embodiment described above, the control section 700C, more specifically, the FC control section 720 and the BAT control section 730 correspond to the "control section". Further, the lower limit voltage control section 750C corresponds to a "deterioration detection section", and the secondary battery output average Pbm corresponds to "the output state of the secondary battery".

D. Other embodiments:
(1) In the lower limit voltage control of the first embodiment (see FIG. 4), the process of detecting deterioration of the fuel cell stack 100 in step S103 is omitted, and the process of reading the previous FC maximum current Ibmax(p) in step S101 is omitted. It may be omitted. In the lower limit voltage control of the second embodiment (see FIG. 7), the process of detecting the deterioration of the fuel cell stack 100 in step S118 is omitted, and the process of reading the previous degree of deterioration Kg(p) in step S111 and the process in step S120 The process of storing the degree of deterioration Kg as the previous degree of deterioration Kg(p) may be omitted. In the lower limit voltage control of the third embodiment (see FIG. 12), the process of detecting deterioration of the fuel cell stack 100 in step S147 is omitted, and the process of reading the previous average secondary battery output Pbm(p) in step S141 Also, the process of storing the secondary battery output average Pbm in step S149 as the previous secondary battery output average Pbm(p) may be omitted.

(2) In the above embodiment, the average cell voltage of the plurality of single cells 110 of the fuel cell stack 100 (see FIG. 1) is described as the output voltage Vfc of the fuel cell stack 100, but it is measured by the cell monitor 580. Among the cell voltages, the lowest cell voltage may be set as the output voltage Vfc of the fuel cell stack 100.

(3) In the above embodiment, a vehicle equipped with one fuel cell system is described as an example, but a vehicle equipped with a plurality of fuel cell systems may be used. In this case, the lower limit voltage may be set in each fuel cell system depending on the degree of deterioration of the fuel cell stack.

(4) In the above embodiment, a fuel cell system installed in a vehicle was explained as an example, but the invention is not limited to this, and various types of systems that use electric power as a power source for a power generation device (for example, a drive motor) are described. It is also applicable to fuel cell systems mounted on moving bodies. Moreover, it is applicable not only to fuel cell systems mounted on moving bodies but also to stationary fuel cell systems.

(5) In the above embodiment, a part of the configuration realized by hardware may be replaced with software, or conversely, a part of the configuration realized by software may be replaced by hardware. Good too. For example, at least part of the functions of the control unit 700 may be realized by an integrated circuit, a discrete circuit, or a module that is a combination of these circuits. Furthermore, if part or all of the functions of the present disclosure are realized by software, the software (also referred to as a "computer program") can be provided in a form stored in a computer-readable recording medium. . "Computer-readable recording media" is not limited to portable recording media such as flexible disks and CD-ROMs, but also various internal storage devices in computers such as RAM and ROM, and fixed devices such as hard disks. It also includes external storage devices. That is, the term "computer-readable recording medium" has a broad meaning including any recording medium on which data packets can be fixed rather than temporarily.

The present invention is not limited to the embodiments described above, and can be realized in various configurations without departing from the spirit thereof. For example, the technical features in the embodiment that correspond to the technical features in the form described in the summary column of the invention may be used to solve some or all of the above-mentioned problems, or to achieve some of the above-mentioned effects. Alternatively, in order to achieve all of the above, it is possible to perform appropriate replacements or combinations. Further, unless the technical feature is described as essential in this specification, it can be deleted as appropriate.

DESCRIPTION OF SYMBOLS 10... Fuel cell system, 20... Traction motor, 100... Fuel cell stack, 110... Single cell, 111... Electrode plate, 200... Anode side gas supply and discharge mechanism, 210... Tank, 220... Shutoff valve, 221... Pressure regulating valve, 222... Injector, 231... Fuel gas supply channel, 232... First anode off-gas discharge channel, 233... Gas circulation channel, 240... Circulation pump, 250... Gas-liquid separator, 260... Purge valve, 262... Second Anode off-gas discharge channel, 271...first pressure sensor, 272...second pressure sensor, 273...third pressure sensor, 300...cathode side gas supply/discharge mechanism, 305...temperature sensor, 310...air cleaner, 320...air compressor, 330... Oxidizing gas supply channel, 331... Cathode off gas discharge channel, 333... Cathode bypass channel, 340... Air distribution valve, 350... Cathode back pressure valve, 360... Muffler, 391... Oxidizing gas supply section, 392... Cathode off gas discharge section, 400...Fuel cell circulation cooling mechanism, 410...Radiator, 420...Temperature sensor, 430...Circulation pump, 441...Cooling medium supply channel, 442...Cooling medium discharge channel, 443...Cooling medium bypass flow 444...Cooling medium distribution valve, 500...Power supply circuit, 520...Inverter, 530...Fuel cell control converter, 550...Secondary battery, 560...Secondary battery control converter, 570...Current measurement unit, 580...Cell monitor , 700...control unit, 710...system control unit, 720...FC control unit, 730...BAT control unit, 740...FC characteristic measurement unit, 750, 750B, 750C...lower limit voltage control unit, 755B...lower limit guard frequency measurement unit, 758C... Secondary battery output measuring section, 760... Storage section

Claims (1)

A fuel cell system,
a fuel cell stack having a plurality of fuel cells that generate electricity by receiving a reaction gas;
a current measuring unit that measures the output current of the fuel cell stack;
a voltage measuring unit that measures the output voltage of the fuel cell stack;
a secondary battery that compensates for the shortfall in the amount of power generated by the fuel cell stack relative to the amount of power generated required for the fuel cell system;
a temperature measurement unit that measures the temperature of the secondary battery;
a power supply circuit that supplies the power output by the fuel cell stack and the power output by the secondary battery to a load;
The power output by the fuel cell stack is controlled so that the cell voltage represented by the output voltage of the fuel cell stack is equal to or higher than the lower limit voltage, and the temperature of the secondary battery is lower than the upper limit temperature. a control unit that controls the power output by the secondary battery and controls the power supplied from the power supply circuit to the load;
an output acquisition unit that acquires an average value of the output of the secondary battery at regular time intervals;
Equipped with
The control unit resets the value of the lower limit voltage when the average value of the output of the secondary battery is larger than the previous average value of the output of the secondary battery, and in the reset, the lower limit voltage The value is set such that the larger the average value of the output of the secondary battery is , the lower the value is set .
fuel cell system.

Images