阅读说明：本技术 燃料电池系统 (Fuel cell system ) 是由 户井田政史 石川智隆 西田裕介 于 2021-04-01 设计创作，主要内容包括：本发明提供一种燃料电池系统,具备：燃料电池；温度取得部,取得燃料电池的温度；单元电压传感器,检测燃料电池单元的电压；及控制部,控制燃料电池系统,控制部在预热运转中个别的燃料电池单元的电压成为预先规定的值以下的情况下,限制燃料电池的输出电流,控制部在燃料电池系统接收到启动请求后,在燃料电池的温度为预先规定的温度以下的情况下执行预热运转,并且控制部在预热运转开始后,在满足停止条件的情况下,停止燃料电池系统的运转,所述停止条件包括：燃料电池单元的电压在预先规定的时间内持续为预先规定的电压值以下。(The present invention provides a fuel cell system, comprising: a fuel cell; a temperature acquisition unit that acquires the temperature of the fuel cell; a cell voltage sensor that detects a voltage of the fuel cell; and a control unit that controls the fuel cell system, wherein the control unit limits an output current of the fuel cell when a voltage of the individual fuel cell unit becomes equal to or less than a predetermined value during the warm-up operation, wherein the control unit executes the warm-up operation when a temperature of the fuel cell becomes equal to or less than a predetermined temperature after the fuel cell system receives a start request, and wherein the control unit stops the operation of the fuel cell system when a stop condition is satisfied after the start of the warm-up operation, the stop condition including: the voltage of the fuel cell continues to be equal to or lower than a predetermined voltage value for a predetermined time.)

1. A fuel cell system is provided with:

a fuel cell including a plurality of fuel cell units stacked together;

a current sensor that obtains an output current of the fuel cell;

a temperature acquisition unit that acquires a temperature of the fuel cell;

a cell voltage sensor that detects a voltage of the fuel cell; and

a control section that controls the fuel cell system,

the control unit limits the output current of the fuel cell when the voltage of the individual fuel cell becomes equal to or less than a predetermined value during warm-up operation,

the control unit executes the warm-up operation when the temperature of the fuel cell is equal to or lower than a predetermined temperature after the fuel cell system receives a start-up request,

the control unit stops the operation of the fuel cell system when a stop condition is satisfied after the warm-up operation is started, the stop condition including that the voltage of the fuel cell unit continues to be equal to or less than a predetermined voltage value for a predetermined time.

2. The fuel cell system according to claim 1,

the control unit sets the predetermined time based on the temperature of the fuel cell acquired by the temperature acquisition unit.

3. The fuel cell system according to claim 1 or 2,

the stop condition includes that a generated charge amount after the fuel cell system receives a start request calculated using an output current of the fuel cell after the start of the warm-up operation is equal to or greater than a predetermined threshold value.

Technical Field

The present disclosure relates to a fuel cell system.

Background

Since the fuel cell generally generates produced water along with power generation, liquid water may be retained in the reactant gas flow path in the fuel cell. When a fuel cell vehicle equipped with a fuel cell is started under a temperature condition of not higher than the freezing point, if liquid water remaining in the fuel cell freezes, the reaction gas cannot sufficiently flow through the fuel cell. This may cause an obstacle to power generation of the fuel cell. In japanese patent laid-open No. 2020-14353, the following technique is proposed: when the temperature of the fuel cell is below the freezing point, the freezing determination of the fuel cell is performed based on the amount of generated electric charge after the fuel cell starts generating electric power.

Disclosure of Invention

As in the technique of japanese patent application laid-open No. 2020-14353, the technique of performing freeze determination based on a phenomenon actually occurring in the fuel cell at the time of low-temperature start of the fuel cell is superior in that freeze determination can be accurately performed, compared to the case of indirectly estimating the frozen state based on the temperature of the refrigerant circulating in the fuel cell or the like. On the other hand, even if it is determined that the reactant gas is not frozen at the time of low-temperature start, it is considered that the reactant gas flow path inside the fuel cell freezes due to a decrease in the outside air temperature, or the liquid water moves to a portion where the temperature in the reactant gas flow path is lower than 0 degrees due to the warm-up operation and freezes, and the reactant gas flow path is blocked, whereby the produced water inside the fuel cell may freeze. Therefore, further improvement is required for the determination of the frozen state based on the phenomenon actually generated in the fuel cell.

The present disclosure can be implemented in the following forms.

(1) According to one aspect of the present disclosure, a fuel cell system is provided. The fuel cell system includes: a fuel cell including a plurality of fuel cell units stacked together; a current sensor that obtains an output current of the fuel cell; a temperature acquisition unit that acquires a temperature of the fuel cell; a cell voltage sensor that detects a voltage of the fuel cell; and a control unit that controls the fuel cell system, wherein the control unit limits an output current of the fuel cell when a voltage of the individual fuel cell unit becomes equal to or less than a predetermined value during a warm-up operation, wherein the control unit executes the warm-up operation when a temperature of the fuel cell is equal to or less than a predetermined temperature after the fuel cell system receives a start request, and wherein the control unit stops the operation of the fuel cell system when a stop condition is satisfied after the start of the warm-up operation, the stop condition including that the voltage of the fuel cell unit continues to be equal to or less than a predetermined voltage value for a predetermined time. When the voltage value of the cell voltmeter is equal to or less than the predetermined voltage value for the predetermined time, freezing that is difficult to thaw by the warm-up operation may occur in the fuel cell. If the warm-up operation of the fuel cell system is continued in this state, electric power equal to or higher than the electric power generated by the power generation is consumed. In the above-described aspect, the control unit stops the operation of the fuel cell system in this case. This can avoid a situation where power equal to or more than the power generated by the power generation is continuously consumed.

(2) In the fuel cell system according to the above aspect, the control unit may set the predetermined time period based on the temperature of the fuel cell acquired by the temperature acquisition unit. In such an aspect, when it is determined that the temperature of the fuel cell acquired by the temperature acquisition unit is a temperature at which freezing in the fuel cell is difficult to thaw even if the warm-up operation is continued, the fuel cell system is stopped as soon as possible, thereby suppressing power consumption of the fuel cell system.

(3) According to the fuel cell system of the above aspect, the stop condition includes that the amount of generated electric charge after the fuel cell system receives a start request, which is calculated using the output current of the fuel cell after the start of the warm-up operation, is equal to or greater than a predetermined threshold value. When the amount of generated electric charge is equal to or greater than a predetermined threshold value, it is considered that the fuel cell generates heat to such an extent that the freezing in the fuel cell can be eliminated. However, when the voltage is equal to or lower than a predetermined voltage value, it is considered that freezing occurs in the fuel cell after the generated charge amount becomes equal to or higher than a predetermined threshold value. In such an aspect, by stopping the operation of the fuel cell system in this case, it is possible to avoid a situation in which power equal to or more than the power generated by the power generation is continuously consumed.

Drawings

Features, advantages, and technical and industrial applicability of exemplary embodiments of the present invention will be described below with reference to the accompanying drawings, in which like reference numerals represent like elements, and in which:

fig. 1 is a schematic configuration diagram of a fuel cell system.

Fig. 2 is a process diagram showing the operation availability determination process executed by the control unit.

Fig. 3 is an explanatory diagram showing a state in which the amount of generated charge of the fuel cell changes after the warm-up operation starts.

Fig. 4 is a process diagram showing a process of determining whether or not the operation is possible, which is executed by the control unit according to the second embodiment.

Fig. 5 is a table showing the freezing determination time according to the temperature of the fuel cell.

Detailed Description

A. First embodiment

Fig. 1 is a schematic configuration diagram of a fuel cell system 10 as a first embodiment. The fuel cell system 10 includes a fuel cell 100, a DC/DC converter 200, a voltage sensor 210, a current sensor 220, a secondary battery 230, a secondary battery converter 240, a load device 250, a DC/AC inverter 260, an operation switch 270, a fuel gas supply/discharge unit 300, an oxidizing gas supply/discharge unit 400, a refrigerant cycle 500, and a control unit 600. In the fuel cell system 10, the fuel cell 100 and the secondary battery 230 are configured to be able to supply electric power to the load device 250 individually, or to be able to supply electric power to the load device 250 simultaneously from both the fuel cell 100 and the secondary battery 230.

The fuel cell 100 and the load device 250 are connected via a DC/DC converter and a wiring 700. DC/DC converter 200 and secondary battery converter 240 are connected in parallel to wiring 700.

The fuel cell 100 is a power generation device that generates dc power by receiving supply of hydrogen gas as a fuel gas and oxygen gas as an oxidizing gas from the outside. The fuel cell 100 has a stack structure in which a plurality of fuel cells 110, which are unit modules for generating electricity, are stacked. In the fuel cell 110, an anode and a cathode are disposed with an electrolyte membrane having proton conductivity interposed therebetween. In the present embodiment, the fuel cell 100 is a polymer electrolyte fuel cell.

The fuel cell 100 is further provided with a plurality of cell voltage sensors 120. The cell voltage sensor 120 is supported by the fuel cell stack via insulating collars disposed at both ends thereof. In the present embodiment, the cell voltage sensor 120 is provided in the fuel cell 100 with respect to the pair of fuel cells 110, and detects the voltage of one fuel cell 110 obtained from the measured voltage. In addition, in fig. 1, one cell voltage sensor is illustrated.

The DC/DC converter 200 has a function of changing the output state of the fuel cell 100 in response to a control signal from the control unit 600. The DC/DC converter 200 receives power of a predetermined voltage from the fuel cell 100, and outputs power obtained by converting current and voltage by switching control in the DC/DC converter 200. Specifically, when the power generated by the fuel cell 100 is supplied to the load device 250, the DC/DC converter 200 boosts the voltage to a voltage that can be used by the load.

The voltage sensor 210 acquires the output voltage of the entire fuel cell 100. The voltage sensor 210 outputs a signal indicating the obtained measured value of the output voltage to the control unit 600. The current sensor 220 obtains the output current of the fuel cell 100.

Secondary battery converter 240 has a function of controlling charging and discharging of secondary battery 230 in response to a control signal from control unit 600. Secondary battery converter 240 receives electric power of a predetermined voltage from DC/DC converter 200 connected to fuel cell 100, and outputs electric power obtained by converting current and voltage by switching control to secondary battery 230. Specifically, when supplying the power generated by the secondary battery 230 to the load device 250, the secondary battery converter 240 boosts the voltage of the power to a voltage usable by the load and supplies the boosted voltage to the load device 250. As a result, the secondary battery converter 240 sets the output-side voltage of the DC/DC converter 200 connected to the fuel cell 100 under the control of the control unit 600, thereby controlling the output voltage of the fuel cell 100 via the DC/DC converter 200.

The secondary battery converter 240 receives power of a predetermined voltage from the secondary battery 230, and outputs the power obtained by converting the current and the voltage by switching control to the DC/AC converter 260 connected to the load device 250. Specifically, when the electric power received from DC/DC converter 200 is supplied to secondary battery 230, secondary battery converter 240 boosts the voltage of the electric power to a voltage that can be charged in secondary battery 230 and supplies the boosted voltage to secondary battery 230. As a result, secondary battery converter 240 adjusts the stored electric power of secondary battery 230 by setting the target voltage on the side of secondary battery 230 under the control of control unit 600. In addition, when the secondary battery 230 does not need to be charged or discharged, the secondary battery converter 240 disconnects the secondary battery 230 from the wiring 700.

The load device 250 operates by electric power supplied from the fuel cell 100 and the secondary battery 230. In the present embodiment, the load device 250 means a driving motor, various auxiliary devices, and the like.

DC/AC converter 260 converts the direct-current power supplied from fuel cell and secondary battery 230 via wiring 700 into three-phase alternating-current power. The DC/AC converter 260 is electrically connected to the load device 250, and supplies three-phase AC power to the load device 250.

The operation switch 270 instructs the control unit 600 to start and stop the fuel cell system 10. In the present embodiment, the operation switch 270 is operated by an operation by a user. When the operation switch 270 is turned on by the user, the fuel cell system 10 receives a start request from the control unit 600, supplies hydrogen gas into the fuel cell 100, and starts power generation.

The fuel gas supply/discharge unit 300 includes a fuel gas supply system 310, a fuel gas circulation system 320, and a fuel gas discharge system 330. The fuel gas supply system 310 supplies hydrogen gas to the fuel cell 100. The fuel gas supply system 310 includes a fuel gas tank 311, a fuel gas supply passage 312, an on-off valve 313, a pressure reducing valve 314, and an injector 315. The fuel gas tank 311 stores hydrogen gas at high pressure. The fuel gas supply path 312 supplies the hydrogen gas in the fuel gas tank 311 to the fuel cell 100. The on-off valve 313 allows the hydrogen gas in the fuel gas tank 311 to flow downstream in the open state. The pressure reducing valve 314 adjusts the pressure of the hydrogen gas on the upstream side of the injector 315 by the control of the control unit 600. The injector 315 is an on-off valve that is electromagnetically driven according to a drive cycle or a valve opening time set by the control unit 600. The injector 315 adjusts the supply amount of the hydrogen gas to be supplied to the fuel cell 100.

The fuel gas circulation system 320 circulates the anode off-gas discharged from the fuel cell 100 to the fuel gas supply passage 312. The fuel gas circulation system 320 includes a fuel gas circulation passage 321, a gas-liquid separator 322, and a circulation pump 323. The fuel gas circulation passage 321 is connected to the fuel cell 100 and the fuel gas supply passage 312. The fuel gas circulation passage 321 is constituted by a pipe through which the anode off-gas flows toward the fuel gas supply passage 312. The gas-liquid separator 322 separates water in a liquid state from the anode off-gas mixed with water. The gas-liquid separator 322 is provided in the fuel gas circulation passage 321. The circulation pump 323 circulates the anode off-gas in the fuel gas circulation passage 321 to the fuel gas supply passage 312 by driving a motor, not shown.

The fuel gas discharge system 330 discharges the anode off-gas and water generated by the power generation of the fuel cell 100 to the atmosphere. The fuel gas discharge system 330 has a discharge water discharge path 331 and a discharge water discharge valve 332. The exhaust water discharge passage 331 is a pipe that connects the discharge port of the gas-liquid separator 322 for discharging water to an oxidizing gas discharge passage 422 described later. The gas/water discharge valve 332 opens and closes the gas/water discharge passage 331. The gas/water discharge valve 332 is disposed in the gas/water discharge passage 331. The gas/water discharge valve 332 is opened by receiving an instruction at a predetermined timing by the control unit 600. Thereby, the gas/water discharge valve 332 is opened, and nitrogen gas as an impurity gas contained in the anode off gas is discharged to the outside through the gas/water discharge passage 331 and the oxidizing gas discharge passage 422 together with water. The predetermined timing is, for example, a timing at which the stored water amount in the gas-liquid separator 322 becomes equal to or more than a predetermined liquid water amount.

The oxidizing gas supply/discharge unit 400 supplies oxygen to the fuel cell 100 and discharges the cathode off-gas from the fuel cell 100. The oxidizing gas supply/discharge unit 400 includes an oxidizing gas supply system 410 and an oxidizing gas discharge system 420. The oxidizing gas supply system 410 supplies oxygen to the fuel cell 100. The oxidizing gas supply system 410 includes an oxidizing gas supply passage 411, an air cleaner 412, a compressor 413, and a flow dividing valve 414.

The oxidizing gas supply passage 411 supplies oxygen gas to the fuel cell 100. The oxidizing gas supply passage 411 is a pipe disposed upstream of the fuel cell 100 and communicating the outside with the cathode side of the fuel cell 100. The air cleaner 412 removes foreign matters in the oxygen gas supplied to the fuel cell 100. The air cleaner 412 is provided on the upstream side of the compressor 413 in the oxidizing gas supply passage 411. The compressor 413 discharges the compressed air to the cathode side of the fuel cell 100 in response to an instruction from the control unit 600. The compressor 413 is provided on the upstream side of the fuel cell 100. Compressor 413 is driven by a motor, not shown, that operates in response to an instruction from control unit 600. The shunt valve 414 can allow or stop the supply of oxygen to the fuel cell 100. The flow dividing valve 414 adjusts the opening degree to adjust the flow rate of the oxidizing gas from the oxidizing gas supply passage 411 to the fuel cell 100 and the flow rate of the oxidizing gas that branches from the oxidizing gas supply passage 411 and does not flow through a bypass passage 421 of the fuel cell 100, which will be described later. The oxygen gas flowing through the bypass passage 421 is discharged to the atmosphere through an oxidizing gas discharge passage 422 described later.

The oxidizing gas discharge system 420 discharges the oxidizing gas. The oxidizing gas discharge system 420 includes a bypass 421, an oxidizing gas discharge 422, and a pressure regulating valve 423. The oxidizing gas discharge passage 422 discharges the cathode off gas containing the oxygen gas discharged from the fuel cell 100 and the oxygen gas flowing through the bypass passage 421 to the atmosphere. The pressure regulating valve 423 regulates the opening degree to regulate the back pressure of the flow path on the cathode side of the fuel cell 100. The pressure regulating valve 423 is provided in the oxidizing gas discharge passage 422 on the upstream side of a connection point with the bypass passage 421.

The refrigerant cycle portion 500 supplies the fuel cell 100 with a refrigerant for cooling the fuel cell 100 that generates heat by power generation. The temperature of the fuel cell 100 is maintained within a predetermined range by the refrigerant circulating through the refrigerant cycle 500. The refrigerant cycle 500 includes a refrigerant pipe 501, a radiator 502, a refrigerant pump 503, and a refrigerant temperature sensor 504. The refrigerant pipe 501 is a pipe for circulating a refrigerant for cooling the fuel cell 100. The radiator 502 has a fan 505 that takes in outside air, and cools the refrigerant by exchanging heat between the refrigerant in the refrigerant pipe 501 and the outside air. The refrigerant pump 503 is driven in accordance with an instruction from the controller 600, and sends the refrigerant to the fuel cell 100. The refrigerant temperature sensor 504 detects the temperature of the refrigerant discharged from the fuel cell 100 after circulating through the fuel cell 100. In the present embodiment, the refrigerant temperature sensor 504 functions as a temperature acquisition unit that acquires the temperature of the fuel cell 100. In the present specification, the temperature of the fuel cell 100 refers to the temperature obtained by the temperature sensor 504 for the refrigerant. As the temperature acquisition unit, for example, a sensor that directly detects the internal temperature of the fuel cell 100 may be used.

The control unit 600 is a so-called microcomputer including a CPU, a ROM, a RAM, and the like that execute logical operations. The control unit 600 acquires detection signals from various sensors provided in the fuel cell system 10, and performs various controls related to the fuel cell system 10. For example, the control unit 600 outputs a drive signal to each unit to obtain electric power corresponding to electric power required by a load from at least one of the fuel cell 100 and the secondary battery 230. Specifically, when electric power is obtained from the fuel cell 100, the amounts of reactant gas supplied from the fuel gas supply and exhaust unit 300 and the oxidizing gas supply and exhaust unit 400 are controlled so that desired electric power is obtained from the fuel cell 100. Further, control unit 600 controls DC/DC converter 200 and secondary battery converter 240 to supply desired electric power from at least one of fuel cell 100 and secondary battery 230 to load device 250. The control unit 600 further includes a timer, and is capable of measuring an elapsed time after various signals are input or various processes are executed.

Further, when the fuel cell system 10 is started up under low temperature conditions, the control unit 600 determines whether or not the flow path of the reactant gas in the fuel cell 100 is frozen while performing the warm-up operation, and determines whether or not the fuel cell system 10 is operable based on the result. This is because, if the fuel cell 100 generates power in a state where the reactant gas flow field is frozen, the reactant gas cannot sufficiently flow through the fuel cell 100, and therefore, there is a possibility that the power generation is hindered.

Fig. 2 is a process diagram showing the operation availability determination process executed by the control unit 600. The determination process of the operability is executed when the fuel cell system 10 receives a start request. In the present embodiment, the fuel cell system 10 receives a start request from the control unit 600 by turning on the operation switch 270. When the fuel cell system 10 receives a start-up request, the operation of the fuel cell 100 using the secondary battery 230 is started.

In step S100, the control unit 600 determines whether or not the temperature of the fuel cell 100 is equal to or lower than a predetermined temperature. In the present embodiment, the predetermined temperature is 0 ℃. When the fuel cell system 10 is used in a highland where the atmospheric pressure is lower, the predetermined temperature can be changed according to the atmospheric pressure of the use environment. The atmospheric pressure in the use environment may be directly detected by providing an atmospheric pressure sensor in the fuel cell system 10, or may be estimated from the altitude of the place where the fuel cell system 10 is located, based on the positional information of the fuel cell system 10.

When it is determined in step S100 that the temperature of the fuel cell 100 is higher than 0 ℃, the process proceeds to step S110. When it is determined that the temperature of the fuel cell 100 is 0 degrees or less, the process proceeds to step S200.

In step S110, the control unit 600 executes a normal operation of the fuel cell system 10, and the process is terminated. The normal operation of the fuel cell system 10 in the present embodiment refers to the following operating state: the operation of the fuel cell system 10 is performed by the power generation of the fuel cell 100 without performing the warm-up operation.

In step S200, the warm-up operation is started. The warm-up operation means an operation state in which: the temperature of the fuel cell 100 is actively raised so that the temperature of the fuel cell 100 reaches a temperature range predetermined as a steady state. When the temperature of the fuel cell 100 at the time of starting the fuel cell system 10 is 0 degrees or less, first, the warm-up operation is performed so that the temperature of the fuel cell 100 exceeds a predetermined temperature, that is, 0 degrees. After the temperature of the fuel cell 100 exceeds 0 degrees by the warm-up operation, the warm-up operation is performed so that the temperature of the fuel cell 100 reaches a temperature range predetermined as a steady state. After the temperature of the fuel cell 100 exceeds 0 degrees, more electric power can be output from the fuel cell 100 than in the warm-up operation performed when the fuel cell 100 is 0 degrees or less.

As the warm-up operation, for example, the following method can be employed: by controlling the flow rate of oxygen to be supplied to the fuel cell 100, the power generation loss of the fuel cell 100 is increased, and the temperature of the fuel cell 100 is raised by self-heating, as compared with the normal operation of the fuel cell system 10 in which it is determined that the fuel cell 100 is not frozen. The warm-up operation is executed by the control unit 600.

In step S300, the control unit 600 determines whether or not the generated charge amount is equal to or greater than a predetermined threshold value. The amount of generated electric charge of the fuel cell 100 is calculated by the control portion 600 using the output current of the current sensor 220 of the fuel cell. The amount of generated electric charge of the fuel cell 100 can be obtained by integrating the product of the time after the fuel cell system 10 receives a start request and starts and the output current of the fuel cell 100. In the present embodiment, the charge amount B is used as a predetermined threshold value used for the determination in step S300. The charge amount B is the amount of generated electric charge obtained from the fuel cell 100 before heat of a degree capable of eliminating freezing in the fuel cell 100 is generated.

Fig. 3 is an explanatory diagram showing a state in which the amount of generated charge of the fuel cell 100 changes after the warm-up operation of the fuel cell 100 is started. The horizontal axis represents time, and the vertical axis represents the generated charge amount. The time when the fuel cell system 10 is started is represented as time t 1. The control unit determines whether or not the generated charge amount exceeds the charge amount B from a time T1, which is a power generation start time, to a time T2 when a predetermined elapsed time T1 has elapsed.

When hydrogen gas flows through the fuel cell 100, the amount of generated electric charge of the fuel cell 100 increases with time (see L1 in fig. 3). On the other hand, since freezing occurs inside the fuel cell 100, when hydrogen gas is not supplied to the fuel cell 100, the amount of generated charge increases before the amount of generated charge reaches the charge amount a, as in the case of hydrogen gas flowing, but the degree of increase in the amount of generated charge is suppressed to a large extent thereafter (see L2 in fig. 3). The charge amount a is an amount of charge that can be generated by using hydrogen gas remaining in the fuel cell 100 at the time of starting the fuel cell system 10. In the case of L2, after power generation is performed using hydrogen gas remaining inside the fuel cell 100, the amount of hydrogen gas supplied to the anode is insufficient due to freezing. In this case, the output current of the fuel cell 100 is limited by the control portion 600, and the degree of increase in the amount of generated charge is suppressed. The limitation of the output current of the fuel cell 100 will be described later.

When the generated charge amount reaches the charge amount B or more within the elapsed time T1, the process proceeds to step S400 (see L1 in fig. 3). If not, the process proceeds to step S600 (see L2 in fig. 3).

In step S400, it is determined whether or not the voltage value of one or more fuel cells 110 is equal to or less than a predetermined voltage value P before the temperature of the fuel cell 100 becomes higher than an arbitrary temperature due to the warm-up operation. If the voltage value of one or more fuel cells 110 becomes equal to or less than the predetermined voltage value P before the temperature of the fuel cell 100 becomes higher than an arbitrary temperature due to the warm-up operation, the process proceeds to step S500 at this point in time. Otherwise, the warm-up operation is ended, and the control unit 600 ends the processing.

During the warm-up operation, as described above, the target voltage and the target current of the fuel cell 100 are set so that the self-heating of the fuel cell 100 is increased. Further, if the flow path of hydrogen gas freezes in any of the fuel cells 110 in the fuel cell 100 during the warm-up operation, the hydrogen gas supplied to the anode becomes insufficient in the fuel cell 110, and the power generation reaction is suppressed. Even in such a case, since the power generation reaction continues in the other fuel cell 110, the fuel cell 110, which is deficient in hydrogen generation, may function as a resistor in the fuel cell 100, and a negative voltage may be generated. If the warm-up operation is continued in such a state, there is a possibility that the fuel cell 100 may be damaged.

Therefore, in the present embodiment, when the voltage value of the individual fuel cell 110 is equal to or less than a predetermined value, the control unit 600 limits the output current to suppress the amount of power generation of the fuel cell 100. In the present embodiment, when the voltage value of the individual fuel cell 110 becomes a negative voltage, the control unit 600 limits the output current. The output current is limited to a current value to the extent that the electric power for the operation of the fuel cell system 10 cannot be supplied. The limit value of the output current is determined based on the voltage value detected by the battery voltage sensor 120. Thereby, damage of the fuel cell 100 is suppressed.

Here, a case where a negative voltage is generated even after it is determined that the generated charge amount is larger than the charge amount B due to the warm-up operation will be described (see step S400 in fig. 2). For example, the outside air temperature drops after step S300, and the flow path of the hydrogen gas in the fuel cell 110 inside the fuel cell 100 freezes, and a negative voltage is generated. In addition, consider the following: the generated water thawed by the warm-up operation moves to a portion having a temperature lower than 0 ℃ in the hydrogen gas flow path and is frozen again, and the hydrogen gas flow path is blocked, thereby generating a negative voltage.

In step S500, if the voltage value of one or more fuel cells 110 continues to be equal to or less than the predetermined voltage value P for the predetermined time period T2, the process proceeds to step S600. If the voltage value P, which is a predetermined voltage value, is exceeded before the predetermined time T2 elapses, there is a possibility that the freezing in the fuel cell 100 is eliminated. Therefore, in these cases, the process shifts to step S400, whereby the warm-up operation is continued. Again in step S400, determination is made again as to whether or not the voltage value of the fuel cell 110 has become equal to or less than the voltage value P before the temperature of the fuel cell 100 becomes higher than an arbitrary temperature. If the voltage value of one or more fuel cells 110 does not become equal to or less than the predetermined voltage value P before the temperature of the fuel cell 100 becomes higher than the arbitrary temperature in step S400 again, the process ends.

If the determination result in step S500 is yes, it is considered that it is difficult to defrost the freeze inside the fuel cell 100 by the warm-up operation. When the control unit 600 determines that the stop condition of the fuel cell system 10 is satisfied, the control unit 600 stops the fuel cell system 10 in step S600, and the process ends.

According to the fuel cell system 10 of the present embodiment configured as described above, the warm-up operation is started when the temperature of the fuel cell 100 is equal to or lower than a predetermined temperature. If the amount of generated electric charge from the start of the electric generation of the fuel cell 100 reaches the amount of electric charge B or more within the elapsed time T1, the warm-up operation is continued. Even when the generated charge amount is equal to or greater than the charge amount B, the flow path of the hydrogen gas in the fuel cell 100 may freeze due to, for example, a decrease in the outside air temperature, and the voltage may become equal to or less than a predetermined voltage value P. If the voltage continues to be equal to or lower than the predetermined voltage value P for the predetermined time T2, freezing that is difficult to thaw by the warm-up operation may occur in the fuel cell 100. If the warm-up operation of the fuel cell system 10 is continued in this state, electric power equal to or higher than the electric power generated by the power generation is consumed. In this case, the operation of the fuel cell system 10 is stopped by the control unit 600. This can avoid a situation where power equal to or more than the power generated by the power generation is continuously consumed. As a result, the electric power for the next start-up of the fuel cell system 10 can be reserved.

B. Second embodiment

Fig. 4 is a process diagram showing the operation availability determination process executed by the control unit 600 according to the second embodiment. The fuel cell system 10 of the second embodiment has the same configuration as the fuel cell system 10 shown in fig. 1, and therefore the same reference numerals are used and detailed description thereof is omitted. In the process diagram of the second embodiment shown in fig. 4, steps common to those in fig. 2 are assigned the same step numbers, and detailed description thereof is omitted. The second embodiment differs from the first embodiment in that a predetermined time T2 is set by the control unit 600 in accordance with the temperature of the fuel cell 100.

Fig. 5 is a table showing the freezing determination time according to the temperature of the fuel cell 100. In the first embodiment, the predetermined time T2 in step S500 is constant regardless of the temperature of the fuel cell 100. In step S500B of the second embodiment, a predetermined time T2 is set in accordance with the temperature of the fuel cell 100 acquired by the temperature sensor 504 for the refrigerant.

When the temperature of the fuel cell 100 is a temperature at which freezing in the fuel cell 100 is likely to be thawed, the freezing in the fuel cell 100 is likely to be thawed by continuing the warm-up operation. Therefore, the control unit 600 sets the predetermined time T2 to be long. On the other hand, when the temperature of the fuel cell 100 is a temperature at which the possibility of freezing and thawing is low, the thawed state may not be eliminated even if the warm-up operation is continued. Therefore, the predetermined time T2 is set to be shorter than the time when thawing is possible. This can suppress power consumption. In the present embodiment, the temperature at which freezing is possible is higher than 10 degrees, and the temperature at which freezing is less possible is 10 degrees or lower. The temperature at which the fuel cell 100 may freeze or thaw may be a temperature different from that of the present embodiment, such as a temperature higher than 11 degrees celsius or a temperature higher than 12 degrees celsius, depending on the environment in which the fuel cell system 10 is disposed.

In step S500B of fig. 4, when the temperature of the fuel cell 100 is 9 degrees, the fuel cell system 10 continues the warm-up operation for 10 seconds in accordance with the instruction of the control unit 600 (see fig. 5). If the voltage value of one or more fuel cells 110 does not continue to be equal to or lower than the voltage value P for 10 seconds, the freeze may be eliminated by continuing the warm-up operation. In this case, the warm-up operation is continued, and the process proceeds to step S400 again.

If it is determined yes again in step S400, the process proceeds to step S500B again. Again in step S500B, when the temperature of the fuel cell 100 acquired by the refrigerant temperature sensor 504 has increased to 10.5 degrees, the warm-up operation is continued, and there is a possibility that the freezing in the fuel cell 100 will be thawed. Therefore, the predetermined time T2 is set to 100 seconds longer than the previous 10 seconds. Then, the warm-up operation was continued for a period of 100 seconds. Further, the control unit 600 determines whether or not the voltage value measured by the cell voltage sensor 120 continuously exceeds the voltage value P.

In step S500B, when the temperature of the fuel cell is 10 degrees or less, the predetermined time T2 is 10 seconds, and when it exceeds 10 degrees, it is 100 seconds. The predetermined time T2 may be 100 seconds when it is 10 degrees or more, or 10 seconds when it is less than 10 degrees.

In this way, when the temperature of the fuel cell 100 measured by the refrigerant temperature sensor 504 is a temperature at which freezing in the fuel cell 100 is likely to be thawed by continuing the warm-up operation, the control unit 600 can extend the predetermined time T2. As a result, the warm-up operation is continued, and therefore the possibility of freezing and thawing inside the fuel cell 100 increases.

On the other hand, in step S500B, when the temperature of the fuel cell 100 is 10 degrees or less, it may be difficult to thaw the freeze in the fuel cell 100 even if the warm-up operation is continued. In this case, it is determined whether or not the voltage value of one or more fuel cells 110 continues to be equal to or lower than the voltage value P for a period T2 without making the predetermined time T2 longer than 10 seconds. Extending the predetermined time T2 to continue the warm-up operation causes consumption of electric power of the fuel cell system 10. Therefore, when the freezing of the fuel cell 100 is difficult to thaw, the operation of the fuel cell system 10 is stopped at an early stage, and thus the consumption of the electric power of the fuel cell system 10 can be suppressed.

C. Other embodiments

C1) In the above embodiment, the fuel cell 100 is a polymer electrolyte fuel cell. However, for example, the fuel cell may be a solid oxide fuel cell, or a fuel cell other than a polymer electrolyte fuel cell may be used.

C2) In the above embodiment, the cell voltage sensor 120 is provided in the fuel cell 100 with respect to the pair of fuel cells 110, and detects the voltage of one fuel cell 110 obtained from the measured voltage. However, for example, the cell voltage sensor may detect the output voltage of each fuel cell. Alternatively, one cell voltage sensor may be provided to detect the voltage of a representative part of the fuel cell cells.

C3) In the above embodiment, when the voltage value of the individual fuel cell 110 is equal to or less than a predetermined value, the control unit 600 limits the output current to suppress the amount of power generation of the fuel cell 100. In the above embodiment, the voltage value of an individual fuel cell 110 is a voltage value of one fuel cell 110 obtained from the voltage measured by the voltage sensor 120 provided for the pair of fuel cells 110. However, for example, the voltage value of an individual fuel cell may be the voltage value of any one of all the fuel cells. The voltage value of any one of the representative fuel cell units may be referred to.

C4) In the above embodiment, in step S400, it is determined whether or not the voltage value of one or more fuel cells 110 is equal to or less than a predetermined voltage value P before the temperature of the fuel cell 100 becomes higher than an arbitrary temperature due to the warm-up operation. The arbitrary temperature is a temperature determined by the control unit to be able to end the warm-up operation, and is a temperature at which freezing and thawing in the fuel cell are possible. Any temperature may be 15 ℃ or 20 ℃. For example, an arbitrary temperature may be set to be 5 degrees higher than the temperature for thawing, which is different from the temperature for thawing the frozen state in the fuel cell. For example, in step S400, it may be determined whether or not the voltage value of one or more fuel cells 110 is equal to or less than a predetermined voltage value P before a time sufficient for the temperature of the fuel cell to be higher than an arbitrary temperature by the warm-up operation elapses. The time sufficient for the temperature of the fuel cell to be higher than any temperature may be 30 minutes or 1 hour.

In the above embodiment, at the time point at which the voltage value of one or more fuel cells 110 becomes equal to or less than the predetermined voltage value P in step S400, the process proceeds to step S500. However, for example, the process may be shifted to step S500 at a time point when the voltage value of the fuel cell of 10% or more becomes equal to or less than the predetermined voltage value P.

C5) In the above embodiment, when the voltage value of one or more fuel cells 110 continues to be equal to or less than the predetermined voltage value P for the predetermined time period T2 in step S500, the process proceeds to step S600. However, for example, when the voltage value of the fuel cell 110 of 10% or more continues to be equal to or lower than the predetermined voltage value P for the predetermined time T2, the process may proceed to step S600.

C6) In the above embodiment, the stop condition includes: after the warm-up operation is started, the generated charge amount is equal to or greater than a predetermined threshold value. However, for example, the stop condition may include that the temperature of the fuel cell is equal to or higher than a certain temperature after the start of the warm-up operation, excluding whether or not the generated charge amount is equal to or higher than a predetermined threshold value. The certain temperature may be any temperature, such as 2 degrees or 5 degrees, etc.

C7) In the second embodiment, the predetermined time T2 is 10 seconds at 10 degrees or less, and 100 seconds if it is greater than 10 degrees. However, for example, the predetermined time T2 may be 20 seconds at 11 degrees or less, or 50 seconds at a time higher than 11 degrees. For example, the predetermined time T2 may be increased by 10 seconds each time the temperature of the fuel cell increases by 5 degrees from 10 degrees.

The present disclosure is not limited to the above-described embodiments, and can be implemented in various configurations without departing from the scope of the present disclosure. For example, in order to solve a part or all of the above-described problems or to achieve a part or all of the above-described effects, the technical features of the embodiments corresponding to the technical features of the respective embodiments described in the section of the summary of the invention may be appropriately replaced or combined. In addition, if the technical feature is not described as a necessary technical feature in the present specification, it may be appropriately deleted.