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

Abstract

To provide a technology that can prevent a fuel cell from overheating and continue generating power in the fuel cell. The fuel cell system includes an inverter capable of outputting electric power, a fuel cell that generates electric power supplied to the inverter based on the electric power output by the inverter, a heat exchanger that cools a refrigerant that cools the fuel cell, and a control valve that controls the flow rate of the refrigerant supplied to the heat exchanger by changing the opening of the control valve. The control method for the fuel cell system includes regulating the electric power output by the inverter based on the opening of the control valve.

Description

[Technical Field]

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

[0002] A cogeneration system equipped with a gas engine is known as a conventional technology (see, for example, Patent Document 1). [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Patent No. 6321484 Summary of the Invention [Problem to be solved by the invention]

[0004] In recent years, from the viewpoint of carbon neutrality, there has been a demand for power generation devices (e.g., monogeneration devices) that use fuel cell systems equipped with fuel cells. In addition to the fuel cell, the fuel cell system is provided with an inverter for interconnecting the system to, for example, a commercial power grid. The inverter is supplied with power generated by the fuel cell.

[0005] Fuel cells generate heat during power generation, and may require cooling with a refrigerant (e.g., cooling water). In this case, a fuel cell system is provided with a heat exchanger that cools the refrigerant and a control valve that controls the flow rate of the refrigerant flowing through the heat exchanger to control the temperature of the refrigerant. However, if the amount of heat generated increases due to deterioration of the fuel cell, or if the cooling performance decreases due to deterioration of the heat exchanger, it may become impossible to control the temperature of the refrigerant (the refrigerant temperature may continue to rise) even if the opening of the control valve is adjusted to increase the amount of refrigerant supplied to the heat exchanger. As a result, the fuel cell may overheat, causing the fuel cell to stop generating power.

[0006] The present invention has been made to solve the above problems, and its purpose is to provide a technology that can prevent overheating of a fuel cell and allow the fuel cell to continue generating electricity. [Means for solving the problem]

[0007] A control method for a fuel cell system according to one aspect of the present invention is a control method for a fuel cell system comprising an inverter capable of outputting electric power, a fuel cell that generates electric power to be supplied to the inverter based on the electric power output by the inverter, a heat exchanger that cools a refrigerant that cools the fuel cell, and a control valve that controls the flow rate of the refrigerant supplied to the heat exchanger by its opening degree, and includes regulating the electric power output by the inverter based on the opening degree of the control valve.

[0008] A control program for a fuel cell system according to another aspect of the present invention causes at least one arithmetic device to execute the above control method.

[0009] A fuel cell system according to another aspect of the present invention includes an inverter capable of outputting electric power, a fuel cell that generates electric power to be supplied to the inverter based on the electric power output by the inverter, a heat exchanger that cools a refrigerant that cools the fuel cell, and a control valve that controls the flow rate of the refrigerant supplied to the heat exchanger by its opening, and further includes a power regulation unit that regulates the electric power output by the inverter based on the opening of the control valve.

[0010] A monogeneration system according to another aspect of the present invention includes the above fuel cell system. [Effects of the Invention]

[0011] According to the above configuration, overheating of the fuel cell can be prevented, and the fuel cell can continue to generate electricity. [Brief explanation of the drawings]

[0012] [Figure 1]1 is a block diagram showing a schematic configuration of a monogeneration device according to an embodiment of the present invention; [Figure 2] FIG. 2 is a block diagram showing a schematic configuration of a cooling system of a fuel cell system provided in the monogeneration device. [Figure 3] 6 is a flowchart showing a flow when the output power of an inverter included in the fuel cell system is regulated. [Figure 4] 10 is an explanatory diagram illustrating the restriction of the output power of the inverter when the conductivity of the refrigerant in the cooling system is high. FIG. [Figure 5] 10 is a flowchart showing a flow when the output power of the inverter is regulated when the temperature of the refrigerant is relatively low. [Figure 6] 10 is an explanatory diagram illustrating the regulation of the output power of the inverter when the temperature of the refrigerant is relatively low. FIG. [Figure 7] 10 is a flowchart showing a modified example of the flow when the output power of the inverter is regulated. DETAILED DESCRIPTION OF THE INVENTION

[0013] The following describes an embodiment of the present invention with reference to the drawings.

[0014] [1. Outline of monogeneration device] 1 is a block diagram showing a schematic configuration of a monogeneration system 1 according to one embodiment of the present invention. The monogeneration system 1 includes a fuel cell system 2 and is connected to a commercial power grid (not shown).

[0015] The fuel cell system 2 generates power using a fuel gas and an oxidant gas supplied from outside the monogeneration device 1. In this embodiment, an example will be described in which hydrogen gas is used as the fuel gas and air is used as the oxidant gas. However, the fuel gas is not limited to hydrogen gas and may be, for example, a gas containing methane as a main component. Furthermore, the oxidant gas is not limited to air and may be any gas containing oxygen. Therefore, the monogeneration device 1 generates power. More specifically, the monogeneration device 1 simply has a power generation function. In other words, for example, a waste heat recovery function for recovering waste heat generated during power generation is excluded from the monogeneration device 1.

[0016] The above-mentioned commercial power system includes a commercial power source (not shown) and supplies commercial power generated by the commercial power source. A load (not shown) is connected to the commercial power system. That is, the above-mentioned load is electrically connected to the fuel cell system 2. The load is, for example, a motor, a pump, etc. The power demand (power consumption) of the load is met by the power generated by the monogeneration device 1 (fuel cell system 2) and the commercial power supplied from the commercial power system. Note that the configuration related to the power supply to the load is not limited to the above. For example, the load may be configured to be directly connected to the monogeneration device 1 without being connected to the commercial power system. In this case, the power demand of the load is met by the power generated by the monogeneration device 1.

[0017] The fuel cell system 2 includes a fuel cell module 21, a battery 22, an inverter 23, and a control device 24. In this embodiment, one fuel cell module 21, one inverter 23, and one control device 24 are provided, and multiple batteries 22 are provided. However, FIG. 1 illustrates only one battery 22 as an example. The numbers of fuel cell modules 21, batteries 22, inverters 23, and control devices 24 are not limited to those described above. For example, there may be multiple fuel cell modules 21, multiple inverters 23, and multiple control devices 24, or there may be only one battery 22. The fuel cell module 21, battery 22, inverter 23, and control device 24 are each disposed inside the monogeneration device 1.

[0018] The fuel cell module 21 has a fuel cell 21a, a boost converter 21b, a compressor 21c, and a fuel cell control unit 21d. That is, the fuel cell system 2 includes the fuel cell 21a, the boost converter 21b, the compressor 21c, and the fuel cell control unit 21d.

[0019] The fuel cell 21a (also called a fuel cell stack) is composed of a plurality of stacked cells. Each cell includes a solid polymer electrolyte membrane, an anode, a cathode, and a pair of separators. The anode and cathode sandwich the solid polymer electrolyte membrane. The anode is a negative electrode (fuel electrode) and includes an anode catalyst layer and a gas diffusion layer. The cathode is a positive electrode (air electrode) and includes a cathode catalyst layer and a diffusion layer. The anode, solid polymer electrolyte membrane, and cathode form a membrane electrode assembly (MEA). The pair of separators sandwich the membrane electrode assembly. Each separator has a plurality of grooves. Each groove in one separator forms a flow path for hydrogen gas. Each groove in the other separator forms a flow path for air.

[0020] At the anode, hydrogen is decomposed into hydrogen ions and electrons by a catalyst. The hydrogen ions pass through the solid polymer electrolyte membrane and move to the cathode. Meanwhile, the electrons pass through an external circuit and move to the cathode. This generates an electric current (electricity is generated). At the cathode, oxygen contained in the air combines with the electrons that have flowed through the external circuit and the hydrogen ions that have passed through the solid polymer electrolyte membrane to produce water. The produced water is contained in the exhaust gas and discharged outside the monogeneration device 1.

[0021] The electric power generated by the fuel cell 21a is boosted by the boost converter 21b and supplied to the inverter 23. That is, the fuel cell 21a generates the electric power to be supplied to the inverter 23. Note that the electric power generated by the fuel cell 21a and boosted by the boost converter 21b may be supplied to the battery 22 in addition to the inverter 23.

[0022] The fuel cell 21a generates heat during power generation. More specifically, the amount of heat generated by the fuel cell 21a increases as the amount of power generated by the fuel cell 21a increases. When the fuel cell 21a generates heat, the temperature of the fuel cell 21a itself rises, and the fuel cell 21a may overheat. In this case, the power generation of the fuel cell 21a is stopped to protect the fuel cell 21a. More specifically, the fuel cell control unit 21d stops the power generation of the fuel cell 21a. To prevent the power generation of the fuel cell 21a from being stopped, the fuel cell system 2 is provided with a cooling system 200 (see FIG. 2), which will be described later, for suppressing the rise in temperature of the fuel cell 21a, i.e., for cooling the fuel cell 21a.

[0023] However, even if the cooling system 200 cools the fuel cell 21a, if it is difficult to suppress the temperature rise of the fuel cell 21a, that is, if there is a high possibility that the fuel cell 21a will overheat, the power output by the inverter 23 is regulated. A control method for the fuel cell system 2 related to the regulation of the power output by the inverter 23 will be described later. Note that, hereinafter, "power output by the inverter 23" may also be referred to as "output power of the inverter 23."

[0024] The compressor 21c is provided to take in air to be supplied to the fuel cell 21a from outside the monogeneration device 1. The air taken in from outside the monogeneration device 1 by the compressor 21c flows into the fuel cell 21a via multiple filters (none of which are shown) provided inside the monogeneration device 1.

[0025] The fuel cell control unit 21d controls each part of the fuel cell module 21. For example, the fuel cell control unit 21d controls the power generation of the fuel cell 21a, the drive of the compressor 21c, etc. The fuel cell control unit 21d is connected to be able to communicate with the control device 24. Communication between the fuel cell control unit 21d and the control device 24 is performed by, for example, CAN communication, but the communication method is not limited to CAN communication.

[0026] The battery 22 is formed of, for example, a lithium ion battery, and stores the power supplied to the inverter 23. The battery 22 may be formed by unitizing a plurality of battery cells, or may be formed by a single battery cell. As described above, the battery 22 may be supplied with power generated by the fuel cell 21a. The battery 22 is charged by the power supplied from the fuel cell 21a to the battery 22.

[0027] The battery 22 is controlled by a battery control unit 22a. The battery control unit 22a is also called a BMU (Battery Management Unit), and controls, for example, the input and output of the battery 22. The battery control unit 22a also calculates a state of charge (SOC) of the battery 22 (described later) based on information (e.g., the voltage, current, temperature, etc. of the battery 22) acquired via various sensors (not shown) provided in the battery 22 (see FIG. 3). The state of charge S of the battery 22 means the ratio of the remaining charge capacity (at that time) to the charge capacity when fully charged.

[0028] The battery control unit 22a is communicably connected to the control device 24. Communication between the battery control unit 22a and the control device 24 is performed, for example, by CAN communication, but the communication method is not limited to CAN communication. The battery control unit 22a transmits, for example, information about the battery 22 (including the charging rate S calculated by the battery control unit 22a) to the control device 24 via CAN communication.

[0029] The inverter 23 is configured by mounting various electrical components (e.g., diodes, capacitors, power transistors, etc.) on a substrate (none of which are shown). The inverter 23 converts DC power supplied from the fuel cell 21a into AC power and outputs it. That is, the inverter 23 is capable of outputting power. More specifically, the inverter 23 converts DC voltage power supplied from the fuel cell 21a, or from the fuel cell 21a and the battery 22, into AC voltage power and supplies it to the load. Specifically, the inverter 23 supplies AC power to the load in accordance with the power demand of the load. For example, when the power demand of the load increases, the inverter 23 increases the AC power supplied to the load, and when the power demand of the load decreases, the inverter 23 reduces the AC power supplied to the load.

[0030] In the following, the voltage supplied to the inverter 23 may be referred to as the link voltage. The voltage (of power) generated by the fuel cell 21a and boosted by the boost converter 21b follows the link voltage. Therefore, the link voltage is the same as the voltage (of power) output from the battery 22.

[0031] The inverter 23 is connected to the control device 24 so as to be able to communicate with it. Communication between the inverter 23 and the control device 24 is performed, for example, by CAN communication, but the communication method is not limited to CAN communication. The inverter 23 transmits information about the inverter 23 to the control device 24 via CAN communication.

[0032] The inverter 23 is provided with an inverter temperature sensor 23a that detects the temperature of the inverter 23. The temperature of the inverter 23 detected by the inverter temperature sensor 23a includes the temperature of the substrate (substrate temperature). Note that the temperature of the inverter 23 may include the temperature of at least one of various electrical components included in the inverter 23, instead of or in addition to the substrate temperature.

[0033] A cooling member 25 is attached to the inverter 23. The cooling member 25 is provided to cool the inverter 23. The cooling member 25 is, for example, a heat sink. The heat sink serving as the cooling member 25 cools the inverter 23 by radiating (diffusing) heat generated when the inverter 23 converts DC power into AC power to the outside of the inverter 23. In other words, the fuel cell system 2 includes a cooling member 25 that cools the inverter 23. A cooling member temperature sensor 25a that detects the temperature of the cooling member 25 is attached to the cooling member 25.

[0034] The inverter temperature sensor 23a and the cooling member temperature sensor 25a are each connected to the control device 24 so as to be able to input signals thereto. This enables the inverter temperature sensor 23a and the cooling member temperature sensor 25a to output detected information (the temperature of the inverter 23 and the temperature of the cooling member 25) to the control device 24.

[0035] The control device 24 controls each part of the fuel cell system 2. In addition to the fuel cell system 2, the control device 24 may also control devices other than the fuel cell system 2 that the monogeneration device 1 includes.

[0036] The control device 24 is, for example, a computer device including an arithmetic device 24a, a storage unit 24b, and an input / output unit (not shown). The arithmetic device 24a is, for example, a processor or a microprocessor. In FIG. 1, as an example, one arithmetic device 24a is illustrated in the control device 24, but the number of arithmetic devices 24a may be two or three or more.

[0037] The storage unit 24b is a main storage device such as a read-only memory (ROM) or a random access memory (RAM). The storage unit 24b may further include an auxiliary storage device such as a hard disk drive (HDD) or a solid state drive (SSD). The storage unit 24b stores various programs, data, and the like. The various programs include a control program 24b1 related to regulating the output power of the inverter 23. For example, the arithmetic unit 24a reads the control program 24b1 from the storage unit 24b and executes arithmetic processing in accordance with the control program 24b1. The programs stored in the storage unit 24b may be provided, for example, by a computer-readable nonvolatile recording medium. As another example, the programs may be provided from a program providing server via a communication line such as the Internet.

[0038] The above-described hardware and software work together to cause the control device 24 to operate as a target power determination unit 24c, a power regulation unit 24d, and a rotation control unit 24e. That is, the fuel cell system 2 includes the target power determination unit 24c, the power regulation unit 24d, and the rotation control unit 24e. The control device 24 may be configured as a single piece of hardware, or may be configured as multiple pieces of hardware that can communicate with each other.

[0039] As described above, the functional units 24c to 24e included in the control device 24 may be realized by causing the arithmetic unit 24a to execute arithmetic processing according to a program, i.e., by software, but may also be realized by other methods. At least one of the functional units 24c to 24e may be realized using, for example, an application-specific integrated circuit (ASIC) or a field-programmable gate array (FPGA). That is, at least one of the functional units 24c to 24e may be realized by hardware using a dedicated IC or the like. Also, at least one of the functional units 24c to 24e may be realized by a combination of software and hardware. Note that the functional units 24c to 24e are conceptual structures. Therefore, the function performed by one component may be distributed among multiple components, or the functions of multiple components may be integrated into one component.

[0040] The target power determination unit 24c determines the target power of the fuel cell 21a based on the power (also called actual power) being output by the inverter 23. More specifically, the target power determination unit 24c first calculates the target power of the fuel cell 21a by correcting the power being output by the inverter 23 with the conversion efficiency of the inverter 23. For example, the target power of the fuel cell 21a is calculated by dividing the power being output by the inverter 23 by the conversion efficiency of the inverter 23.

[0041] Next, the target power determination unit 24c adjusts the calculated target power of the fuel cell 21a by an adjustment value corresponding to the charging rate S of the battery 22, and determines the target power of the fuel cell 21a. Specifically, if the charging rate S of the battery 22 is the same as the target charging rate of the battery 22, the target power determination unit 24c determines the calculated target power of the fuel cell 21a (as is) as the target power of the fuel cell 21a. If the charging rate S of the battery 22 is lower than the target charging rate of the battery 22, the target power determination unit 24c determines the target power of the fuel cell 21a by adding a predetermined first adjustment value to the calculated target power of the fuel cell 21a. If the charging rate S of the battery 22 is higher than the target charging rate of the battery 22, the target power determination unit 24c determines the target power of the fuel cell 21a by subtracting a predetermined second adjustment value from the calculated target power of the fuel cell 21a. In this embodiment, the target charging rate of the battery 22, the first adjustment value, and the second adjustment value are set in advance and stored in the storage unit 24b.

[0042] The target power determination unit 24c instructs the fuel cell control unit 21d to cause the fuel cell 21a to generate power at the determined target power for the fuel cell 21a. Based on this instruction, the fuel cell control unit 21d controls the fuel cell 21a so that the power output from the fuel cell 21a becomes the target power. In other words, the fuel cell 21a generates power based on the power output by the inverter 23.

[0043] If the power demand of the load electrically connected to the inverter 23 suddenly fluctuates, the power generated by the fuel cell 21a may be insufficient or excessive relative to the power that should be supplied to the inverter 23 so that the inverter 23 outputs the same power as the power demand of the load. For example, if the power demand of the load suddenly increases, the power generated by the fuel cell 21a may be insufficient relative to the power that should be supplied to the inverter 23 so that the inverter 23 outputs the same power as the power demand of the load. In this case, the battery 22 discharges to make up for the shortage of power that should be supplied to the inverter 23.

[0044] On the other hand, if the power demand of the load suddenly decreases, the power generated by the fuel cell 21a becomes excessive with respect to the power that should be supplied to the inverter 23 so that the inverter 23 outputs the same power as the power demand of the load. In this case, the battery 22 is charged and functions as a supply destination for the surplus power generated by the fuel cell 21a. In other words, the battery 22 has the function of assisting the power supply from the fuel cell 21a to the inverter 23.

[0045] The power regulation unit 24d changes (controls) a regulation value 23R (see FIG. 3, etc.) of the inverter 23, which will be described later, based on the temperature of the inverter 23, the temperature of the cooling member 25, an opening degree VO (see FIG. 3) of a control valve 215 (see FIG. 2), which will be described later, etc. The rotation control unit 24e controls the rotation of a first fan 213a and a second fan 224a (both of which are shown in FIG. 2), which will be described later.

[0046] [2. Configuration of the cooling system of the fuel cell system] 2 is a block diagram that schematically shows the configuration of a cooling system 200 of the fuel cell system 2. The cooling system 200 has a first cooling system 210 that cools the fuel cell 21a, and a second cooling system 220 that cools the compressor 21c (see FIG. 1) and the like.

[0047] The first cooling system 210 includes a first refrigerant circulation path 211, a first refrigerant pump 212, a first heat exchanger 213, an ion exchanger 214, a control valve 215, an intake air cooler 216, a plurality of first refrigerant temperature sensors 217, and an electrical conductivity sensor 218. The first refrigerant pump 212, the control valve 215, the intake air cooler 216, and some of the first refrigerant temperature sensors 217 are included in the fuel cell module 21.

[0048] In this embodiment, the first heat exchanger 213 is also referred to as a heat exchanger HE. Furthermore, the first refrigerant temperature sensor 217 is also referred to as a first temperature sensor TS1. That is, the fuel cell system 2 includes a heat exchanger HE (the first heat exchanger 213 in this embodiment) and a first temperature sensor TS1 (the first refrigerant temperature sensor 217 in this embodiment).

[0049] In addition, in this embodiment, the inverter temperature sensor 23a (see FIG. 1) is also referred to as the second temperature sensor TS2. As described above, the inverter temperature sensor 23a detects the temperature of the inverter 23 (see FIG. 1). That is, the fuel cell system 2 includes the second temperature sensor TS2 (inverter temperature sensor 23a in this embodiment) that detects the temperature of the inverter 23. Furthermore, the cooling member temperature sensor 25a (see FIG. 1) is also referred to as the third temperature sensor TS3. As described above, the cooling member temperature sensor 25a detects the temperature of the cooling member 25 (see FIG. 1). That is, the fuel cell system 2 includes the third temperature sensor TS3 (cooling member temperature sensor 25a in this embodiment) that detects the temperature of the cooling member 25.

[0050] The first refrigerant circulation path 211 is a flow path for circulating a refrigerant. In this embodiment, cooling water is used as the refrigerant, but this is not limiting, and for example, cooling oil or cooling gas may be used as the refrigerant.

[0051] The first refrigerant circulation path 211 is connected to the fuel cell 21a, a first refrigerant pump 212, a first heat exchanger 213, an ion exchanger 214, a control valve 215, and an intake air cooler 216. More specifically, the fuel cell 21a, the first refrigerant pump 212, and the first heat exchanger 213 are connected in series. The ion exchanger 214 is connected in parallel to the first heat exchanger 213. More specifically, the first refrigerant circulation path 211 is provided with a first bypass path 211a that connects a path between the first heat exchanger 213 and the first refrigerant pump 212 and a path between the fuel cell 21a and the first heat exchanger 213. The ion exchanger 214 is connected in parallel to this first bypass path 211a. A control valve 215 is provided at a connection between the path between the fuel cell 21a and the first heat exchanger 213 and the first bypass path 211a.

[0052] The intake air cooler 216 is connected in parallel to the fuel cell 21a. More specifically, the first refrigerant circulation path 211 is provided with a second bypass path 211b that connects a path between the first refrigerant pump 212 and the fuel cell 21a and a path between the fuel cell 21a and the control valve 215. The intake air cooler 216 is connected in series to this second bypass path 211b.

[0053] The first refrigerant temperature sensor 217 is provided in a flow path between the first refrigerant pump 212 and the fuel cell 21a and in a flow path between the fuel cell 21a and the control valve 215. In addition, the first refrigerant temperature sensor 217 is provided in a flow path between the control valve 215 and the first heat exchanger 213 and in a flow path between the first heat exchanger 213 and the first refrigerant pump 212. The first refrigerant temperature sensor 217 detects the temperature of the refrigerant circulating through the first refrigerant circulation path 211. That is, the first temperature sensor TS1 (the first refrigerant temperature sensor 217 in this embodiment) detects the temperature of the refrigerant.

[0054] Hereinafter, the refrigerant temperature detected by the first refrigerant temperature sensor 217 provided in the flow path between the first refrigerant pump 212 and the fuel cell 21a may be referred to as the fuel cell inlet temperature. The refrigerant temperature detected by the first refrigerant temperature sensor 217 provided in the flow path between the fuel cell 21a and the control valve 215 may be referred to as the fuel cell outlet temperature. The refrigerant temperature detected by the first refrigerant temperature sensor 217 provided in the flow path between the control valve 215 and the first heat exchanger 213 may be referred to as the first heat exchanger inlet temperature. The refrigerant temperature detected by the first refrigerant temperature sensor 217 provided in the flow path between the first heat exchanger 213 and the first refrigerant pump 212 may be referred to as the fuel cell module inlet temperature or the first heat exchanger outlet temperature.

[0055] Each first refrigerant temperature sensor 217 is connected to the control device 24 (see FIG. 1) so as to be able to input a signal thereto. This enables each first refrigerant temperature sensor 217 to output detected information (refrigerant temperature) to the control device 24.

[0056] The first refrigerant pump 212 is an electric pump, and is driven by power supplied from the control device 24. When the first refrigerant pump 212 is driven by power supplied from the control device 24, the refrigerant circulates through the first refrigerant circulation path 211. More specifically, the refrigerant discharged from the first refrigerant pump 212 flows into the fuel cell 21a and the intake air cooler 216. The refrigerant that flows into the fuel cell 21a flows inside the fuel cell 21a. Specifically, the refrigerant passes through the multiple cells that make up the fuel cell 21a. This cools the fuel cell 21a. That is, the refrigerant cools the fuel cell 21a. Note that, as the refrigerant passes through the multiple cells in the fuel cell 21a, the refrigerant is in an energized state.

[0057] The intake air cooler 216 cools the air (intake air) supplied to the fuel cell 21a by the compressor 21c. Specifically, the air taken in from outside the cogeneration system 1 by the compressor 21c hits the intake air cooler 216. The air hitting the intake air cooler 216 is cooled by heat exchange with the refrigerant flowing inside the intake air cooler 216.

[0058] The refrigerant discharged from the fuel cell 21a and the intake air cooler 216 flows into the control valve 215. The control valve 215 is configured as, for example, a three-way valve. The control valve 215 controls the flow direction and flow rate of the refrigerant that has flowed into the control valve 215 according to an opening degree VO (see FIG. 3), which will be described later. In this embodiment, when the opening degree VO is 100%, all of the refrigerant that has flowed into the control valve 215 is supplied to the first heat exchanger 213. When the opening degree VO is 50%, half of the refrigerant that has flowed into the control valve 215 is supplied to the first heat exchanger 213, and the remainder (the remaining half) of the refrigerant that has flowed into the control valve 215 is supplied to the first bypass flow path 211a. When the opening degree VO is 0%, all of the refrigerant that has flowed into the control valve 215 is supplied to the first bypass flow path 211a. That is, the fuel cell system 2 includes a control valve 215 that controls the flow rate of the refrigerant supplied to the heat exchanger HE (the first heat exchanger 213 in this embodiment) by the opening degree VO.

[0059] As described above, the first bypass passage 211a is connected to the ion exchanger 214. Therefore, the flow rate of the refrigerant supplied to the ion exchanger 214 is controlled by the opening degree VO of the control valve 215.

[0060] The opening degree VO of the control valve 215 is controlled by the fuel cell control unit 21d (see FIG. 1). Specifically, the fuel cell control unit 21d controls the opening degree VO based on the temperature of the refrigerant circulating through the first refrigerant circulation path 211. For example, the fuel cell control unit 21d increases the opening degree VO as the temperature of the refrigerant increases. This increases the flow rate of the refrigerant supplied to the first heat exchanger 213, and decreases the flow rate of the refrigerant supplied to the first bypass flow path 211a (ion exchanger 214). On the other hand, the fuel cell control unit 21d decreases the opening degree VO as the temperature of the refrigerant decreases. This reduces the flow rate of the refrigerant supplied to the first heat exchanger 213, and increases the flow rate of the refrigerant supplied to the first bypass flow path 211a (ion exchanger 214).

[0061] The first heat exchanger 213 cools the refrigerant by exchanging heat between the air (wind) hitting the first heat exchanger 213 and the refrigerant flowing inside the first heat exchanger 213. That is, the heat exchanger HE (the first heat exchanger 213 in this embodiment) cools the refrigerant.

[0062] The flow of air hitting the first heat exchanger 213 is generated by the first fan 213a. In this embodiment, the first fan 213a is also referred to as the fan FN. That is, the fuel cell system 2 includes the fan FN (the first fan 213a in this embodiment) that generates the flow of air hitting the heat exchanger HE (the first heat exchanger 213 in this embodiment). The first fan 213a is an electric fan, and is driven by power supplied from the control device 24.

[0063] In this embodiment, two first heat exchangers 213 are provided. However, in Fig. 2, as an example, only one first heat exchanger 213 is illustrated. The number of first heat exchangers 213 is not limited to two. For example, the number of first heat exchangers 213 may be one, or three or more.

[0064] A first reserve tank 213b is connected to the first heat exchanger 213. The first reserve tank 213b is connected to the first refrigerant circulation path 211 in addition to the first heat exchanger 213. More specifically, the first reserve tank 213b is connected to a flow path between the first heat exchanger 213 and the first refrigerant pump 212. The first reserve tank 213b is also connected to a flow path between the fuel cell 21a and the control valve 215. The first reserve tank 213b is, for example, a sealed (pressurized) reserve tank, and the refrigerant in the first refrigerant circulation path 211 circulates via the first reserve tank 213b.

[0065] The ion exchanger 214 includes an ion exchange filter and the like. When the refrigerant flows through the ion exchanger 214, impurity ions are removed from the refrigerant. The impurity ions are eluted into the refrigerant, for example, from pipes and the like that constitute the first refrigerant circulation path 211. When the impurity ions eluted into the refrigerant increase, the conductivity K (see FIG. 4) of the refrigerant, which will be described later, increases, and when the impurity ions decrease, the conductivity K of the refrigerant decreases. In other words, the fuel cell system 2 includes the ion exchanger 214, which can reduce the conductivity K of the refrigerant by removing impurity ions from the refrigerant. Note that when the conductivity K of the refrigerant increases, electric shock via the first cooling system 210 becomes more likely.

[0066] The conductivity K of the refrigerant is detected by a conductivity sensor 218 provided in a flow path between first heat exchanger 213 and first refrigerant pump 212. The conductivity sensor 218 is connected to be able to input a signal to control device 24. This enables conductivity sensor 218 to output detected information (conductivity K of the refrigerant) to control device 24.

[0067] The second cooling system 220 includes a second refrigerant circulation path 221, a second refrigerant pump 222, an oil cooler 223, a second heat exchanger 224, and a plurality of second refrigerant temperature sensors 225. The oil cooler 223 and some of the second refrigerant temperature sensors 225 are included in the fuel cell module 21.

[0068] The second refrigerant circulation path 221 is a flow path for circulating a refrigerant different from the refrigerant circulating through the first refrigerant circulation path 211. In this embodiment, cooling water is used as the other refrigerant, but the present invention is not limited thereto, and for example, cooling oil or cooling gas may be used as the other refrigerant.

[0069] Second refrigerant circulation path 221 is connected to second refrigerant pump 222, oil cooler 223, and second heat exchanger 224. More specifically, second refrigerant pump 222, oil cooler 223, and second heat exchanger 224 are connected in series.

[0070] Second refrigerant temperature sensor 225 is provided in a flow path between second heat exchanger 224 and oil cooler 223 and a flow path between oil cooler 223 and second refrigerant pump 222. Second refrigerant temperature sensor 225 detects the temperature of the other refrigerant circulating through second refrigerant circulation path 221.

[0071] Second refrigerant pump 222 is configured as an electric pump and is driven by power supplied from control device 24. When second refrigerant pump 222 is driven by power supplied from control device 24, the other refrigerant circulates in second refrigerant circulation path 221. More specifically, the other refrigerant discharged from second refrigerant pump 222 flows into oil cooler 223 via second heat exchanger 224.

[0072] The oil cooler 223 cools the cooling oil for cooling the compressor 21c (particularly the motor portion of the compressor 21c) and the like included in the fuel cell module 21. Specifically, the cooling oil that has flowed through the compressor 21c and the like flows into the oil cooler 223. The cooling oil that has flowed into the oil cooler 223 is cooled by heat exchange with another refrigerant that flows inside the oil cooler 223 (separate from the cooling oil).

[0073] The second heat exchanger 224 cools the other refrigerant by exchanging heat between the air (wind) hitting the second heat exchanger 224 and the other refrigerant flowing inside the second heat exchanger 224. The flow of air hitting the second heat exchanger 224 is generated by the second fan 224a.

[0074] The second fan 224a is an electric fan and is driven by power supplied from the control device 24. In this embodiment, the second fan 224a generates an air flow that hits the second heat exchanger 224, and also generates an air flow that hits the first heat exchanger 213. More specifically, a portion of the first heat exchanger 213 is disposed between the second heat exchanger 224 and the second fan 224a. Therefore, the air flow generated by the second fan 224a passes through the first heat exchanger 213 in addition to the second heat exchanger 224.

[0075] A second reserve tank 224b is connected to the second heat exchanger 224. The second reserve tank 224b is, for example, an open-type reserve tank, and stores another refrigerant. When the other refrigerant circulating through the second refrigerant circulation path 221 becomes insufficient, the other refrigerant is replenished from the second reserve tank 224b.

[0076] [3. Control method for regulating inverter output power] 3 is a flowchart showing the flow when the output power of the inverter 23 is regulated. In step S0, it is assumed that a regulation value 23R of the inverter 23, which will be described later, is set to a predetermined value 23R0 that is the same as the rated power (also called rated output).

[0077] In step S1, the power regulation unit 24d (see FIG. 1) determines whether the opening degree VO of the control valve 215 is equal to or greater than the opening degree threshold VOt. In this embodiment, the opening degree threshold VOt is provided to determine the limit of the cooling performance of the first cooling system 210 (see FIG. 2). The opening degree threshold VOt is set in advance and stored in the storage unit 24b (see FIG. 1) of the control device 24. If the opening degree VO is equal to or greater than the opening degree threshold VOt (Yes in step S1), the process proceeds to the next step S2. If the opening degree VO is not equal to or greater than the opening degree threshold VOt (No in step S1), the process proceeds to step S6.

[0078] In step S2, the power regulation unit 24d determines whether the temperature of the coolant (circulating through the first coolant circulation path 211) is equal to or higher than the first coolant temperature threshold RTt1. In this embodiment, the coolant temperature used in the above determination is the fuel cell module inlet temperature (the coolant temperature detected by the first coolant temperature sensor 217 provided in the flow path between the first heat exchanger 213 and the first coolant pump 212). The coolant temperature used in the determination is not limited to the fuel cell module inlet temperature. For example, the coolant temperature used in the determination may be at least one of the fuel cell inlet temperature, the fuel cell outlet temperature, and the first heat exchanger inlet temperature instead of or in addition to the fuel cell module inlet temperature. In this embodiment, the first coolant temperature threshold RTt1 is set to determine whether the coolant temperature is high. The first coolant temperature threshold RTt1 is set in advance and stored in the storage unit 24b.

[0079] If the coolant temperature (in this embodiment, the fuel cell module inlet temperature) is equal to or greater than the first coolant temperature threshold RTt1 (Yes in step S2), the process proceeds to the next step S3. If the coolant temperature is not equal to or greater than the first coolant temperature threshold RTt1 (No in step S2), the process proceeds to step S6.

[0080] In step S3, the rotation control unit 24e (see FIG. 1) sets the target rotation speed TR (also referred to as the rotation speed command value) of the first fan 213a to the maximum rotation speed Rmax (of the first fan 213a). Therefore, the control method for the fuel cell system 2 of this embodiment includes executing the following process when the temperature of the refrigerant detected by the first temperature sensor TS1 (the first refrigerant temperature sensor 217 in this embodiment) is equal to or higher than the first refrigerant temperature threshold RTt1. That is, the control method includes setting the target rotation speed TR of the fan FN (the first fan 213a in this embodiment) to the maximum rotation speed Rmax. When the target rotation speed TR of the first fan 213a is set to the maximum rotation speed Rmax, the rotation control unit 24e controls the first fan 213a so that the first fan 213a rotates at the maximum rotation speed Rmax. When the target rotation speed TR of the first fan 213a is set to the maximum rotation speed Rmax, the process proceeds to the next step S4.

[0081] When the refrigerant temperature is equal to or higher than first refrigerant temperature threshold RTt1, rotation control unit 24e sets target rotation speed TR of first fan 213a to maximum rotation speed Rmax, and also sets target rotation speed TR of first fan 213a based on opening degree VO of control valve 215. For example, rotation control unit 24e increases target rotation speed TR of first fan 213a as opening degree VO of control valve 215 increases.

[0082] In step S4, power regulation unit 24d determines whether target rotation speed TR of first fan 213a is equal to or greater than maximum rotation speed Rmax. As shown in step S3, target rotation speed TR of first fan 213a is set to maximum rotation speed Rmax when the refrigerant temperature is equal to or greater than first refrigerant temperature threshold RTt1. However, the cases in which target rotation speed TR of first fan 213a is equal to or greater than maximum rotation speed Rmax are not limited to the above. For example, when opening degree VO of control valve 215 is equal to or greater than a predetermined threshold (even if the refrigerant temperature is not equal to or greater than first refrigerant temperature threshold RTt1), target rotation speed TR of first fan 213a may be set to equal to or greater than maximum rotation speed Rmax.

[0083] If the target rotation speed TR of the first fan 213a is equal to or greater than the maximum rotation speed Rmax (Yes in step S4), the process proceeds to step S5. If the target rotation speed TR of the first fan 213a is not equal to or greater than the maximum rotation speed Rmax, that is, if the target rotation speed TR of the first fan 213a is less than the maximum rotation speed Rmax (No in step S4), the process proceeds to step S6.

[0084] In step S5, the power regulating unit 24d reduces the regulated value 23R of the inverter 23 from a preset value 23R0 (rated power in this embodiment). When the regulated value 23R of the inverter 23 is reduced from the predetermined value 23R0, the output power of the inverter 23 is regulated. More specifically, the inverter 23 is prohibited from outputting power greater than the regulated value 23R. That is, the inverter 23 is capable of outputting power equal to or less than the regulated value 23R. In other words, the regulated value 23R regulates the power output by the inverter 23. For example, if the regulated value 23R is set to the predetermined value 23R0, which is the same as the rated power, the inverter 23 is capable of outputting power equal to or less than the rated power, and therefore the output power of the inverter 23 is in an unregulated state (not regulated). On the other hand, when the regulated value 23R is smaller than the predetermined value 23R0, which is the same as the rated power, the inverter 23 is unable to output the rated power, and therefore the output power of the inverter 23 is regulated.

[0085] Therefore, the control method for the fuel cell system 2 of this embodiment includes regulating the power output by the inverter 23 when the opening VO of the control valve 215 is equal to or greater than the opening threshold VOt. In particular, the control method for the fuel cell system 2 includes regulating the power output by the inverter 23 when the opening VO of the control valve 215 is equal to or greater than the opening threshold VOt and the refrigerant temperature is equal to or greater than the first refrigerant temperature threshold RTt1. Furthermore, the control method for the fuel cell system 2 includes regulating the power output by the inverter 23 when the opening VO of the control valve 215 is equal to or greater than the opening threshold VOt and the target rotation speed TR of the fan FN is equal to or greater than the maximum rotation speed Rmax.

[0086] In this embodiment, the power regulating unit 24d reduces (slightly decreases) the regulated value 23R from the predetermined value 23R0 by a first predetermined amount (e.g., 1 kW) at intervals of a first predetermined time (e.g., 60 seconds). This gradually reduces the regulated value 23R, and gradually regulates the output power of the inverter 23. That is, the control method for the fuel cell system 2 of this embodiment includes gradually reducing the regulated value 23R when regulating the power output by the inverter 23. When the regulated value 23R is reduced, the process returns to step S1.

[0087] Note that when the output power of the inverter 23 is regulated, for example, if the target rotation speed TR of the first fan 213a becomes less than the maximum rotation speed Rmax (if the determinations in both step S6 and step S7 described below are negative), the following occurs: That is, the process is prevented from proceeding to step S5, and the reduction of the regulation value 23R is stopped. That is, the regulation of the output power of the inverter 23 is lifted. Therefore, the control method of the fuel cell system 2 includes lifting the regulation of the power output by the inverter 23 when the target rotation speed TR of the fan FN (first fan 213a in this embodiment) becomes less than the maximum rotation speed Rmax.

[0088] From the viewpoint of reliably realizing the lifting of the restriction on the output power of the inverter 23 in a simple manner, the following configuration is desirable: That is, as in this embodiment, the control method for the fuel cell system 2 desirably includes lifting the restriction on the power output by the inverter 23 when the target rotation speed TR becomes less than the maximum rotation speed Rmax.

[0089] Similarly, when the output power of the inverter 23 is regulated, if the opening degree VO of the control valve 215 becomes less than the opening degree threshold value VOt, or if the temperature of the refrigerant becomes less than the first refrigerant temperature threshold value RTt1, the regulation of the output power of the inverter 23 is released.

[0090] In step S6, the power regulation unit 24d determines whether the temperature of the cooling member 25 (see FIG. 1) is equal to or higher than the cooling member temperature threshold 25Tt. As described above, the temperature of the cooling member 25 is detected by the cooling member temperature sensor 25a (see FIG. 1) and output from the cooling member temperature sensor 25a to the control device 24. In this embodiment, the cooling member temperature threshold 25Tt is provided to determine whether the cooling member 25 is overheated. More specifically, the cooling member temperature threshold 25Tt is set so that when the temperature of the cooling member 25 is equal to or higher than the cooling member temperature threshold 25Tt, the cooling member 25 is determined to be overheated. The cooling member temperature threshold 25Tt is set in advance and stored in the storage unit 24b.

[0091] If the temperature of the cooling member 25 is equal to or higher than the cooling member temperature threshold 25Tt (Yes in step S6), the process proceeds to step S5. That is, the output power of the inverter 23 is regulated. That is, the control method of the fuel cell system 2 includes regulating the power output by the inverter 23 when the temperature of the cooling member 25 detected by the third temperature sensor TS3 (in this embodiment, the cooling member temperature sensor 25a) is equal to or higher than the cooling member temperature threshold 25Tt.

[0092] If the output power of the inverter 23 is restricted, the heat generated when the inverter 23 converts DC power to AC power is reduced. As a result, even if the temperature of the cooling member 25 that cools the inverter 23 is equal to or higher than the cooling member temperature threshold 25Tt and the cooling member 25 is overheated, that is, even if it is difficult for the cooling member 25 to cool the inverter 23, overheating of the inverter 23 is prevented. Therefore, the inverter 23 is prevented from being unable to output (power). In other words, when the temperature of the cooling member 25 is equal to or higher than the cooling member temperature threshold 25Tt, it is desirable to restrict the output power of the inverter 23. From this perspective, in a configuration in which the fuel cell system 2 includes the cooling member 25 that cools the inverter 23 and the third temperature sensor TS3 (cooling member temperature sensor 25a in this embodiment) that detects the temperature of the cooling member 25, the following configuration is desirable. That is, as in this embodiment, it is desirable that the control method of the fuel cell system 2 includes regulating the power output by the inverter 23 when the temperature of the cooling member 25 detected by the third temperature sensor TS3 is equal to or higher than the cooling member temperature threshold 25Tt.

[0093] If the temperature of the cooling member 25 is not equal to or higher than the cooling member temperature threshold 25Tt (No in step S6), the process proceeds to step S7. Note that when the temperature of the cooling member 25 is equal to or higher than the cooling member temperature threshold 25Tt and the output power of the inverter 23 is restricted because the temperature of the cooling member 25 is equal to or higher than the cooling member temperature threshold 25Tt, if the temperature of the cooling member 25 falls below the cooling member temperature threshold 25Tt (if the determination in step S7 is negative), the following process is executed. That is, the process does not proceed to step S5, and the restriction on the output power of the inverter 23 is lifted.

[0094] In step S7, the power regulation unit 24d determines whether the temperature of the inverter 23 is equal to or higher than the inverter temperature threshold 23Tt. As described above, the temperature of the inverter 23 is detected by the inverter temperature sensor 23a (see FIG. 1) and output from the inverter temperature sensor 23a to the control device 24. In this embodiment, the inverter temperature threshold 23Tt is provided to determine whether the inverter 23 is overheating. More specifically, the inverter temperature threshold 23Tt is set so that the inverter 23 is determined to be overheating when the temperature of the inverter 23 is equal to or higher than the inverter temperature threshold 23Tt. The inverter temperature threshold 23Tt is set in advance and stored in the storage unit 24b.

[0095] If the temperature of the inverter 23 is equal to or higher than the inverter temperature threshold value 23Tt (Yes in step S7), the process proceeds to step S5. That is, the output power of the inverter 23 is regulated. In other words, the control method of the fuel cell system 2 includes regulating the power output by the inverter 23 when the temperature of the inverter 23 detected by the second temperature sensor TS2 (in this embodiment, the inverter temperature sensor 23a) is equal to or higher than the inverter temperature threshold value.

[0096] When the fuel cell system 2 is configured to include a second temperature sensor TS2 (in this embodiment, an inverter temperature sensor 23a) that detects the temperature of the inverter 23, the following configuration is desirable from the viewpoint of preventing overheating of the inverter 23 and protecting the inverter 23. That is, as in this embodiment, the control method for the fuel cell system 2 desirably includes regulating the power output by the inverter 23 when the temperature of the inverter 23 detected by the second temperature sensor TS2 is equal to or higher than the inverter temperature threshold value 23Tt.

[0097] If the temperature of the inverter 23 is not equal to or higher than the inverter temperature threshold 23Tt (No in step S7), the process proceeds to step S8. Note that when the temperature of the inverter 23 is equal to or higher than the inverter temperature threshold 23Tt and the output power of the inverter 23 is restricted, if the temperature of the inverter 23 falls below the inverter temperature threshold 23Tt, the following process is executed. That is, the process does not proceed to step S5, and the restriction on the output power of the inverter 23 is lifted.

[0098] In step S8, the power regulator 24d determines whether the regulated value 23R is equal to the predetermined value 23R0. If the regulated value 23R is equal to the predetermined value 23R0 (Yes in step S8), the regulated value 23R is returned to the state before the regulation, and the flow chart ends. If the regulated value 23R is not equal to the predetermined value 23R0 (No in step S8), the process proceeds to step S9.

[0099] In step S9, the power regulation unit 24d increases the regulation value 23R of the inverter 23 (which was reduced from the predetermined value 23R0 in the process of step S5). In this embodiment, the power regulation unit 24d increases (slightly increases) the regulation value 23R, which was reduced from the predetermined value 23R0, by a second predetermined amount (e.g., 1 kW) at intervals of a second predetermined time (e.g., 60 seconds). This gradually increases the regulation value 23R.

[0100] When the regulated value 23R increases, the process returns to step S1. Therefore, when the regulation of the output power of the inverter 23 is released, the processes of steps S8 and S9 are repeated (the regulated value 23R gradually increases) until the regulated value 23R becomes equal to the predetermined value 23R0. As a result, the output power of the inverter 23 gradually returns to the state before the regulation. In other words, the control method of the fuel cell system 2 includes gradually increasing the regulated value 23R when the regulation of the power output by the inverter 23 is released.

[0101] As described above, the power regulation unit 24d and the like are realized by having the arithmetic device 24a (see FIG. 1) of the control device 24 execute arithmetic processing in accordance with the control program 24b1. Therefore, the control method for the fuel cell system 2, which is related to the various processes in the flowchart shown in FIG. 3 and which is executed by the power regulation unit 24d and the like, is also realized by having the arithmetic device 24a execute arithmetic processing in accordance with the control program 24b1. In this embodiment, as described above, one arithmetic device 24a executes the above arithmetic processing, but if there are two or more arithmetic devices 24a, the arithmetic processing may be implemented by two or more arithmetic devices 24a. In other words, the control program 24b1 for the fuel cell system 2 in this embodiment is a program that causes at least one arithmetic device 24a to execute the control method for the fuel cell system 2.

[0102] As described above, the control method for the fuel cell system 2 of this embodiment includes regulating the power output by the inverter 23 based on the opening degree VO of the control valve 215. In addition, the power regulating unit 24d included in the fuel cell system 2 regulates the power output by the inverter 23 based on the opening degree VO of the control valve 215.

[0103] When the fuel cell 21a included in the fuel cell system 2 deteriorates, the amount of heat generated by the fuel cell 21a increases. More specifically, even if the same amount of power is generated, the amount of heat generated by the fuel cell 21a after deterioration is greater than the amount of heat generated by the fuel cell 21a before deterioration. Furthermore, when the heat exchanger HE (in this embodiment, the first heat exchanger 213) deteriorates, the cooling performance of the heat exchanger HE decreases. Furthermore, when the outside air temperature becomes high, the cooling performance of the heat exchanger HE decreases (compared to when the outside air temperature is low). In such cases, the temperature of the refrigerant that cools the fuel cell 21a increases.

[0104] When the temperature of the refrigerant rises, the control valve 215 increases the opening degree VO, making it easier for the refrigerant that has flowed into the control valve 215 to be supplied to the heat exchanger HE (increasing the flow rate of the refrigerant supplied to the heat exchanger HE), thereby lowering the temperature of the refrigerant. However, if the amount of heat generated by the fuel cell 21a is too great or the cooling performance of the heat exchanger HE has deteriorated too much, the temperature of the refrigerant may continue to rise even if the control valve 215 increases the opening degree VO, and it may become impossible for the refrigerant to cool the fuel cell 21a.

[0105] In this case, that is, even if the control valve 215 increases the opening degree VO but the refrigerant cannot cool the fuel cell 21a, the above configuration can restrict the power output by the inverter 23 to prevent the fuel cell 21a from overheating. More specifically, since the fuel cell 21a generates power based on the power (actual power) output by the inverter 23, restricting (reducing) the power output by the inverter 23 based on the opening degree VO of the control valve 215 can reduce the power generated by the fuel cell 21a. This can suppress the heat generation (heat generation amount) of the fuel cell 21a. Reducing the heat generation of the fuel cell 21a can suppress an increase in the temperature of the fuel cell 21a, preventing overheating of the fuel cell 21a. This can prevent the fuel cell 21a from stopping power generation, allowing the fuel cell 21a to continue power generation. As described above, overheating of the fuel cell 21a can be prevented, and power generation by the fuel cell 21a can be continued.

[0106] If the output power of the inverter 23 is restricted, the power supplied to the load from the inverter 23 will be reduced, and there is a risk that the power demand of the load will not be met. Therefore, in order to reliably meet the power demand of the load, it is desirable to restrict the output power of the inverter 23 only when necessary.

[0107] For example, when the opening degree VO of the control valve 215 is less than the opening degree threshold VOt, increasing the opening degree VO to equal to or greater than the opening degree threshold VOt increases the flow rate of the refrigerant supplied to the heat exchanger HE (the first heat exchanger 213 in this embodiment). This cools the refrigerant, facilitating cooling of the fuel cell 21a. Therefore, when the opening degree VO is less than the opening degree threshold VOt, it is not necessary to restrict the output power of the inverter 23. Therefore, it is desirable to restrict the output power of the inverter 23 when the opening degree VO is equal to or greater than the opening degree threshold VOt. From this perspective, as in this embodiment, the control method for the fuel cell system 2 desirably includes restricting the power output by the inverter 23 when the opening degree VO of the control valve 215 is equal to or greater than the opening degree threshold VOt.

[0108] In a configuration in which the fuel cell system 2 includes a first temperature sensor TS1 (first refrigerant temperature sensor 217 in this embodiment) that detects the temperature of the refrigerant, the first temperature sensor TS1 can detect the temperature of the refrigerant. When the temperature of the refrigerant detected by the first temperature sensor TS1 is less than the first refrigerant temperature threshold RTt1, the opening degree VO is equal to or greater than the opening degree threshold VOt. In other words, even if further cooling of the refrigerant is difficult, the refrigerant temperature itself is low, so cooling of the fuel cell 21a is sufficient. Therefore, when the opening degree VO is equal to or greater than the opening degree threshold VOt, and the refrigerant temperature is less than the first refrigerant temperature threshold RTt1, it is not necessary to restrict the output power of the inverter 23. Therefore, when the opening degree VO is equal to or greater than the opening degree threshold VOt, it is desirable to restrict the output power of the inverter 23 when the refrigerant temperature is equal to or greater than the first refrigerant temperature threshold RTt1. From this perspective, as in this embodiment, it is desirable that the control method for the fuel cell system 2 includes regulating the power output by the inverter 23 when the opening VO of the control valve 215 is equal to or greater than the opening threshold VOt and the refrigerant temperature is equal to or greater than the first refrigerant temperature threshold RTt1.

[0109] In a configuration in which the fuel cell system 2 includes a fan FN (first fan 213a in this embodiment) that generates a flow of air that hits a heat exchanger HE (first heat exchanger 213 in this embodiment), when the amount of air (air volume) generated by the fan FN increases, the following occurs. That is, heat exchange in the heat exchanger HE is promoted (the cooling performance of the heat exchanger HE is improved), and the refrigerant flowing inside the heat exchanger HE is more easily cooled. In particular, if the fan FN rotates at the maximum rotation speed Rmax, the refrigerant is reliably cooled. Therefore, in order to reliably cool the refrigerant, it is desirable to set the target rotation speed TR of the fan FN to the maximum rotation speed Rmax.

[0110] However, as the rotation speed of the fan FN increases, the noise of the fan FN increases. For this reason, it is desirable to set the target rotation speed TR of the fan FN to the maximum rotation speed Rmax only when necessary. For example, it is desirable to set the target rotation speed TR of the fan FN to the maximum rotation speed Rmax when the refrigerant is at a high temperature, specifically when the temperature of the refrigerant is equal to or higher than the first refrigerant temperature threshold RTt1. From this perspective, as in this embodiment, it is desirable that the control method for the fuel cell system 2 includes setting the target rotation speed TR of the fan FN to the maximum rotation speed Rmax when the temperature of the refrigerant detected by the first temperature sensor TS1 is equal to or higher than the first refrigerant temperature threshold RTt1.

[0111] When the target rotation speed TR is set smaller than the maximum rotation speed Rmax, even if the opening VO of the control valve 215 is equal to or greater than the opening threshold VOt, setting the target rotation speed TR to equal to or greater than the maximum rotation speed Rmax enables (further) cooling of the refrigerant. Therefore, when the opening VO is equal to or greater than the opening threshold VOt, it is not necessary to restrict the output power of the inverter 23 when the target rotation speed TR is less than the maximum rotation speed Rmax. Therefore, when the opening VO is equal to or greater than the opening threshold VOt, it is desirable to restrict the output power of the inverter 23 when the target rotation speed TR is equal to or greater than the maximum rotation speed Rmax. From this perspective, as in this embodiment, it is desirable that the control method for the fuel cell system 2 includes restricting the power output by the inverter 23 when the opening VO of the control valve 215 is equal to or greater than the opening threshold VOt and the target rotation speed TR is equal to or greater than the maximum rotation speed Rmax.

[0112] From the viewpoint of gradually regulating the output power of the inverter 23 to satisfy the power demand of the load with the power output by the inverter 23 and avoiding overheating of the fuel cell 21a at the same time, the following configuration is desirable: That is, as in this embodiment, the control method for the fuel cell system 2 desirably includes gradually reducing the regulation value 23R that regulates the power output by the inverter 23 when regulating the power output by the inverter 23.

[0113] If the restriction value 23R is immediately returned (increased) to the state before the restriction (predetermined value 23R0 in this embodiment) when the restriction on the output power of the inverter 23 is released, heat generation in the fuel cell 21a resumes, for example, before the refrigerant temperature sufficiently drops below the first refrigerant temperature threshold RTt1. Then, the refrigerant temperature again (instantly) reaches the first refrigerant temperature threshold RTt1, and the restriction on the output power of the inverter 23 is initiated (resumes). That is, switching between restriction and release of the restriction on the output power of the inverter 23 is repeated in a short period of time. Repeated switching in a short period of time reduces the stability of control in the fuel cell system 2. Therefore, it is desirable to prevent repeated switching between restriction and release of the restriction on the output power of the inverter 23 in a short period of time, thereby improving the stability of control in the fuel cell system 2. From this perspective, it is desirable that the control method for the fuel cell system 2, as in this embodiment, gradually increase the restriction value 23R when the restriction on the power output by the inverter 23 is released.

[0114] As described above, when the opening degree VO is large, the flow rate of the refrigerant supplied to the first heat exchanger 213 is large, and the flow rate of the refrigerant supplied to the ion exchanger 214 connected to the first bypass flow path 211a is small. If this state continues, the conductivity K of the refrigerant gradually increases. Below, we will explain how to restrict the output power of the inverter 23 when the conductivity K of the refrigerant is high.

[0115] FIG. 4 is an explanatory diagram illustrating the regulation of the output power of the inverter 23 when the conductivity K of the refrigerant is high. The regulation of the output power of the inverter 23 is performed when the conductivity K of the refrigerant detected by the conductivity sensor 218 (see FIG. 2) is equal to or greater than the conductivity threshold Kt. That is, the control method for the fuel cell system 2 of this embodiment includes regulating the power output by the inverter 23 when the conductivity K of the refrigerant is equal to or greater than the conductivity threshold Kt. More specifically, when the conductivity K is less than the conductivity threshold Kt, the regulation value 23R of the inverter 23 is set to, for example, a predetermined value 23R0 that is the same as the rated power. Therefore, in this case, the output power of the inverter 23 is not regulated (not regulated).

[0116] On the other hand, when the conductivity K is equal to or greater than the conductivity threshold Kt, the regulation value 23R decreases as the conductivity K increases. That is, the output power of the inverter 23 is regulated. For example, the regulation value 23R when the first conductivity K1 is equal to or greater than the conductivity threshold Kt is compared with the regulation value 23R when the second conductivity K2 is equal to or greater than the conductivity threshold Kt and higher than the first conductivity K1. The second regulation value 23R2 when the second conductivity K2 is equal to or greater than the conductivity threshold Kt is smaller than the first regulation value 23R1 when the first conductivity K1 is used.

[0117] In this embodiment, the conductivity threshold Kt is set to determine an increase in the conductivity K (the likelihood of electric shock). Specifically, the conductivity threshold Kt is set so that when the conductivity K becomes equal to or greater than the conductivity threshold Kt, electric shock becomes more likely to occur via the first cooling system 210 (see FIG. 2). The conductivity threshold Kt is set in advance and stored in the storage unit 24b.

[0118] In a configuration in which the fuel cell system 2 includes an ion exchanger 214 that reduces the electrical conductivity K of the refrigerant and the flow rate of the refrigerant supplied to the ion exchanger 214 is controlled by the opening degree VO of the control valve 215, the electrical conductivity K is reduced by controlling the opening degree VO. More specifically, when the output power of the inverter 23 is regulated, heat generation from the fuel cell 21a is suppressed and the temperature of the refrigerant decreases. Then, the control valve 215 reduces the opening degree VO to reduce the flow rate of the refrigerant supplied to the first heat exchanger 213 and increase the flow rate of the refrigerant supplied to the ion exchanger 214. This reduces the electrical conductivity K and reduces the risk of electric shock. Therefore, when electric shock is likely to occur, such as when the electrical conductivity K is equal to or greater than the electrical conductivity threshold value Kt, it is desirable to regulate the output power of the inverter 23 to reduce the electrical conductivity K. From this perspective, as in this embodiment, the control method for the fuel cell system 2 desirably includes regulating the power output by the inverter 23 when the electrical conductivity K of the refrigerant is equal to or greater than the electrical conductivity threshold value Kt.

[0119] In this embodiment, the output power of the inverter 23 is regulated even when the refrigerant temperature is relatively low (for example, below freezing), such as during cold start-up of the monogeneration system 1. More details are provided below. Figure 5 is a flowchart showing the flow of regulating the output power of the inverter 23 when the refrigerant temperature is relatively low. In step S10, it is assumed that the refrigerant temperature is relatively low and the regulation value 23R of the inverter 23 is set to a predetermined value 23R0 that is the same as the rated power.

[0120] In step S11, power regulation unit 24d (see FIG. 1) determines whether the refrigerant temperature is equal to or lower than second refrigerant temperature threshold RTt2. As described above, the refrigerant temperature is detected by first refrigerant temperature sensor 217 (see FIG. 2). In this embodiment, second refrigerant temperature threshold RTt2 is set in advance and stored in memory unit 24b. If the refrigerant temperature is equal to or lower than second refrigerant temperature threshold RTt2 (Yes in step S11), processing proceeds to the next step S12. If the refrigerant temperature is not equal to or lower than second refrigerant temperature threshold RTt2 (No in step S11), this flowchart ends.

[0121] In step S12, the power regulating unit 24d reduces the regulation value 23R of the inverter 23 from a preset value 23R0 (rated power in this embodiment). That is, the output power of the inverter 23 is regulated. In other words, the control method for the fuel cell system 2 of this embodiment includes regulating the power output by the inverter 23 when the temperature of the refrigerant detected by the first temperature sensor TS1 (first refrigerant temperature sensor 217 in this embodiment) is equal to or lower than the second refrigerant temperature threshold value RTt2. More specifically, this is as follows. FIG. 6 is an explanatory diagram illustrating the regulation of the output power of the inverter 23 when the temperature of the refrigerant is relatively low.

[0122] When the refrigerant temperature is relatively low and the opening degree VO is less than the low-temperature opening threshold VOtL, the power regulating unit 24d reduces the regulated value 23R from the predetermined value 23R0 as the opening degree VO decreases. For example, the regulated value 23R at a first opening degree VO1 less than the low-temperature opening threshold VOtL is compared with the regulated value 23R at a second opening degree VO2 less than the low-temperature opening threshold VOtL and smaller than the first opening degree VO1. The fourth regulated value 23R4 at the second opening degree VO2 is smaller than the third regulated value 23R3 at the first opening degree VO1. When the regulated value 23R is reduced from the predetermined value 23R0, the output power of the inverter 23 is regulated as described above. The power regulating unit 24d increases the (reduced) regulated value 23R as the opening degree VO increases. The low-temperature opening threshold VOtL is preset and stored in the storage unit 24b.

[0123] As described above, the fuel cell control unit 21d (see FIG. 1) increases the opening degree VO as the refrigerant temperature increases. Therefore, even if the refrigerant temperature is relatively low, the opening degree VO increases if the refrigerant temperature increases due to heat generation associated with power generation by the fuel cell 21a, etc. As the opening degree VO increases, the regulating value 23R increases. For example, if the opening degree VO increases from the second opening degree VO2 to the first opening degree VO1, the regulating value 23R increases from the fourth regulating value 23R4 to the third regulating value 23R3. Since the inverter 23 can output more power as the regulating value 23R increases, the regulating value 23R increases, thereby relaxing the restriction on the output power of the inverter 23. In other words, the control method for the fuel cell system 2 of this embodiment includes relaxing the restriction on the power output by the inverter 23 when the refrigerant temperature is equal to or lower than the second refrigerant temperature threshold RTt2 as the opening degree VO of the control valve 215 increases.

[0124] When the temperature of the refrigerant is relatively low and the opening VO is equal to or greater than the low-temperature opening threshold VOtL, the power regulating unit 24d maintains the regulated value 23R at the predetermined value 23R0. Therefore, in this case, the output power of the inverter 23 is not regulated (not regulated).

[0125] During cold start-up of the monogeneration system 1, the temperature of the fuel cell 21a itself, like the temperature of the refrigerant, is relatively low (for example, below freezing). Therefore, the fuel cell control unit 21d sets the opening degree VO of the control valve 215 to, for example, 0% in order to quickly increase the temperature of the fuel cell 21a, the temperature of the refrigerant passing through the fuel cell 21a, etc. Then, as described above, all of the refrigerant that flows into the control valve 215 is supplied to the first bypass flow path 211a. Therefore, the refrigerant circulates through the first refrigerant circulation path 211 (see FIG. 2), avoiding the first heat exchanger 213 (see FIG. 2). As a result, the temperature of the refrigerant rises more quickly than when the refrigerant circulates while passing through (being cooled by) the first heat exchanger 213.

[0126] Note that low-temperature (relatively low-temperature) refrigerant remains stagnant in the flow path between control valve 215 and first heat exchanger 213. In addition, low-temperature refrigerant also remains stagnant in the flow path between first heat exchanger 213 and first refrigerant pump 212, a connection portion with first bypass flow path 211a, and the flow path between first heat exchanger 213.

[0127] In this state, for example, if the output power of the inverter 23 increases and the power generated by the fuel cell 21a increases, i.e., the heat generation amount of the fuel cell 21a increases, the temperature of the refrigerant rises. Then, the fuel cell control unit 21d increases the opening degree VO of the control valve 215 to cool the refrigerant (suppress the rise in the refrigerant temperature). As a result, the low-temperature refrigerant that had been stagnating (for example, in the flow path between the control valve 215 and the first heat exchanger 213) flows into the fuel cell module 21 (see FIG. 1) (flows toward the fuel cell 21a). When the low-temperature refrigerant flows in, the temperature of the refrigerant detected by the first refrigerant temperature sensor 217 (for example, provided in the flow path between the first heat exchanger 213 and the first refrigerant pump 212) drops. Therefore, the fuel cell control unit 21d resets the opening degree VO of the control valve 215 to, for example, 0% in order to raise the temperature of the refrigerant. That is, the opening degree VO of the control valve 215 is repeatedly switched in a short period of time. If the opening degree VO of the control valve 215 is repeatedly switched in a short period of time, the stability of control in the fuel cell system 2 will decrease.

[0128] If the output power of the inverter 23 is restricted when the refrigerant temperature is relatively low, specifically, equal to or lower than the second refrigerant temperature threshold RTt2, and this restriction is relaxed as the opening degree VO of the control valve 215 increases, a gradual increase in the refrigerant temperature can be reliably achieved. If the refrigerant temperature increases gradually (gently), the opening degree VO will not be repeatedly switched within a short period of time, improving the stability of control in the fuel cell system 2. From this perspective, as in this embodiment, the control method for the fuel cell system 2 preferably includes restricting the power output by the inverter 23 when the refrigerant temperature detected by the first temperature sensor TS1 is equal to or lower than the second refrigerant temperature threshold RTt2. In addition, the control method for the fuel cell system 2 preferably includes relaxing the restriction on the power output by the inverter 23 when the refrigerant temperature is equal to or lower than the second refrigerant temperature threshold RTt2 as the opening degree VO of the control valve 215 increases.

[0129] When the opening degree VO of the control valve 215 becomes equal to or greater than the low temperature opening degree threshold VOtL, the refrigerant temperature has risen sufficiently, so that even if the restriction on the output power of the inverter 23 is released, the opening degree VO of the control valve 215 will no longer be repeatedly switched in a short period of time.

[0130] [4. Modified example of control method related to regulation of inverter output power] Fig. 7 is a flowchart showing a modified example of the flow when the output power of the inverter 23 is regulated. The flowchart shown in Fig. 7 is the same as the flowchart shown in Fig. 3 except that steps S1A, S1B, and S1C are added between step S1 (step S2, step S3) and step S6. Therefore, the following description will focus on these differences, and a description of the same points will be omitted.

[0131] In step S1A, the power regulation unit 24d (see FIG. 1) determines whether the power difference PD between the output power of the inverter 23 and the power output (generated) by the fuel cell 21a is equal to or greater than a power difference threshold PDt. In this embodiment, the power difference threshold PDt is provided to determine whether power generation is defective in the fuel cell 21a. More specifically, this is as follows. For example, if power generation is defective in the fuel cell 21a, the power output by the fuel cell 21a will decrease. However, even if the power output by the fuel cell 21a decreases, the inverter 23 will be supplied with power output (discharged) by the battery 22 (see FIG. 1). This maintains the output power of the inverter 23. As a result, the power difference PD increases. Therefore, the power difference threshold PDt is set so that a power generation defect occurs in the fuel cell 21a when the power difference PD is equal to or greater than the power difference threshold PDt. The power difference threshold PDt is set in advance and stored in the storage unit 24b.

[0132] If the power difference PD is equal to or greater than the power difference threshold PDt (Yes in step S1A), the process proceeds to step S1B. If the power difference PD is not equal to or greater than the power difference threshold PDt (No in step S1A), the process proceeds to step S6.

[0133] In step S1B, the power regulation unit 24d determines whether the charging rate S of the battery 22 is less than the charging rate threshold St. In this embodiment, the charging rate threshold St is provided to determine whether the battery 22 is in an over-discharged state. More specifically, the charging rate threshold St is set so that the battery 22 is in an over-discharged state when the charging rate S is less than the charging rate threshold St. The charging rate threshold St is set in advance and stored in the storage unit 24b.

[0134] If the charging rate S is less than the charging rate threshold St (Yes in step S1B), the process proceeds to step S5. That is, when the power difference PD is equal to or greater than the power difference threshold PDt, and the charging rate S is less than the charging rate threshold St, the output power of the inverter 23 is regulated. If the charging rate S is not less than the charging rate threshold St, that is, if the charging rate S is equal to or greater than the charging rate threshold St (No in step S1B), the process proceeds to step S1C.

[0135] In step S1C, the power regulation unit 24d determines whether the voltage V of the battery 22 is less than a voltage threshold Vt. In this embodiment, the voltage threshold Vt is set to determine whether the battery 22 is in an over-discharged state. More specifically, the voltage threshold Vt is set so that the battery 22 is in an over-discharged state when the voltage V falls below the voltage threshold Vt. The voltage threshold Vt is set in advance and stored in the storage unit 24b.

[0136] If the voltage V is less than the voltage threshold Vt (Yes in step S1C), the process proceeds to step S5. That is, when the power difference PD is equal to or greater than the power difference threshold PDt, and the voltage V is less than the voltage threshold Vt, the output power of the inverter 23 is regulated.

[0137] However, when the power difference PD is equal to or greater than the power difference threshold PDt, the output power of the inverter 23 may be regulated when both the voltage V is less than the voltage threshold Vt and the charging rate S is less than the charging rate threshold St are satisfied when the power difference PD is equal to or greater than the power difference threshold PDt. That is, the control method for the fuel cell system 2 of this embodiment includes regulating the power output by the inverter 23 when the power difference PD between the power output by the inverter 23 and the power output (generated) by the fuel cell 21a is equal to or greater than the power difference threshold PDt. In particular, the control method for the fuel cell system 2 includes the following. That is, when the power difference PD is equal to or greater than the power difference threshold PDt, the control method for the fuel cell system 2 includes regulating the power output by the inverter 23 when at least one of the charging rate S is less than the charging rate threshold St and the voltage V is less than the voltage threshold Vt is satisfied.

[0138] In order to reliably cover the power demand of the load electrically connected to the inverter 23, it is desirable that the inverter 23 (fuel cell system 2) continue to output power even if a power generation failure occurs in the fuel cell 21a. In other words, it is desirable that the inverter 23 output as much power as possible even if a power generation failure occurs in the fuel cell 21a. From this perspective, as in the modified example, it is desirable that the control method for the fuel cell system 2 includes regulating the power output by the inverter 23 when the power difference PD between the power output by the inverter 23 and the power output by the fuel cell 21a is equal to or greater than a power difference threshold PDt.

[0139] In a configuration in which the fuel cell system 2 includes the battery 22 that assists the power supply from the fuel cell 21a to the inverter 23, even if the fuel cell 21a fails to generate power, the battery 22 can output (discharge) power in place of the fuel cell 21a. In particular, if the state of charge of the battery 22 is good, the power to be supplied to the inverter 23 can be supplied (for a while) by the power output from the battery 22. An example of a state of charge of the battery 22 is when the state of charge S is equal to or greater than the state of charge threshold St and the voltage V is equal to or greater than the voltage threshold Vt. Therefore, when the power difference PD is equal to or greater than the power difference threshold PDt, and the state of charge S is equal to or greater than the state of charge threshold St and the voltage V is equal to or greater than the voltage threshold Vt, there is no need to restrict the output power of the inverter 23.

[0140] As described above, it is desirable to restrict the output power of the inverter 23 only when necessary. Therefore, when the power difference PD is equal to or greater than the power difference threshold PDt, it is desirable to restrict the output power of the inverter 23 when at least one of the following conditions is satisfied: the charging rate S is less than the charging rate threshold St, and the voltage V is less than the voltage threshold Vt. From this perspective, as in the modified example, it is desirable that the control method for the fuel cell system 2 includes the following. That is, it is desirable to include restricting the power output by the inverter 23 when at least one of the following conditions is satisfied: the charging rate S is less than the charging rate threshold St, and the voltage V is less than the voltage threshold Vt, when the power difference PD is equal to or greater than the power difference threshold PDt.

[0141] Note that the voltage V often has a smaller deviation from the actual value than the charging rate S. More specifically, as described above, the charging rate S is calculated by the battery control unit 22a (see FIG. 1) based on the voltage V of the battery 22 and the like. Specifically, the charging rate S increases as the voltage V increases, and decreases as the voltage V decreases. In other words, the charging rate S is an estimated value. In contrast, the voltage V is acquired by a voltage sensor included in the various sensors described above. For this reason, the difference between the voltage V detected by the voltage sensor and the actual voltage is often smaller than the difference between the calculated charging rate S and the actual charging rate.

[0142] [5. Supplementary Information] In this embodiment, an example has been described in which a monogeneration device 1 simply having a power generation function is equipped with a fuel cell system 2, but the fuel cell system 2 may be applied to devices other than the monogeneration device 1. For example, the fuel cell system 2 may be applied to a cogeneration device that generates power and recovers waste heat generated during the power generation, making it possible to use the heat for, for example, hot water supply or heating. Because the fuel cell 21a included in the fuel cell system 2 generates heat during power generation, the fuel cell system 2 is suitable for a cogeneration device.

[0143] [6. Notes] The control method, control program 24b1, fuel cell system 2, and monogeneration device 1 of the fuel cell system 2 described in this embodiment can also be expressed as the control method, control program, fuel cell system, and monogeneration device of the fuel cell system shown in the following appendix.

[0144] The control method of the fuel cell system of appendix (1) is an inverter capable of outputting electric power; a fuel cell that generates power to be supplied to the inverter based on the power output by the inverter; a heat exchanger for cooling a refrigerant that cools the fuel cell; a control valve that controls the flow rate of the refrigerant supplied to the heat exchanger by changing the opening degree of the control valve, The control valve is configured to regulate the power output from the inverter based on the opening degree of the control valve.

[0145] A control method for a fuel cell system according to claim (2) is the control method according to claim (1), When the opening of the control valve is equal to or greater than an opening threshold, the power output by the inverter is restricted.

[0146] The control method for a fuel cell system according to Supplementary Note (3) is the control method according to Supplementary Note (2), the fuel cell system includes a first temperature sensor that detects the temperature of the coolant; When the opening of the control valve is equal to or greater than the opening threshold, the temperature of the refrigerant detected by the first temperature sensor is equal to or greater than a first refrigerant temperature threshold, and the power output by the inverter is regulated.

[0147] A control method for a fuel cell system according to claim 4, wherein the control method according to claim 3, the fuel cell system includes a fan that generates a flow of air that hits the heat exchanger; The method includes setting the target rotation speed of the fan to a maximum rotation speed when the temperature of the coolant detected by the first temperature sensor is equal to or higher than the first coolant temperature threshold value.

[0148] The control method for a fuel cell system according to claim 5 further comprises the steps of: When the opening of the control valve is equal to or greater than the opening threshold, the power output by the inverter is regulated when the target rotation speed is equal to or greater than the maximum rotation speed.

[0149] The control method for a fuel cell system according to claim 6 further comprises the steps of: When the target rotation speed becomes less than the maximum rotation speed, the restriction on the power output by the inverter is released.

[0150] The control method for a fuel cell system according to Supplementary Note (7) is the control method according to any one of Supplementary Note (3) to (6), When the temperature of the refrigerant detected by the first temperature sensor is equal to or lower than a second refrigerant temperature threshold, restricting the power output by the inverter; Relaxing the restriction on the power output by the inverter when the temperature of the refrigerant is equal to or lower than the second refrigerant temperature threshold as the opening degree of the control valve increases.

[0151] A control method for a fuel cell system according to claim (8) is the control method according to any one of claims (1) to (7), the fuel cell system includes a second temperature sensor that detects the temperature of the inverter; The method includes restricting the power output by the inverter when the temperature of the inverter detected by the second temperature sensor is equal to or higher than an inverter temperature threshold value.

[0152] The control method for a fuel cell system according to Supplementary Note (9) is the control method according to any one of Supplementary Note (1) to (8), The fuel cell system includes: a cooling member that cools the inverter; a third temperature sensor that detects the temperature of the cooling member; The method includes restricting the power output by the inverter when the temperature of the cooling member detected by the third temperature sensor is equal to or higher than a cooling member temperature threshold value.

[0153] A control method for a fuel cell system according to claim (10) is the control method according to any one of claims (1) to (9), The method includes restricting the power output by the inverter when the power difference between the power output by the inverter and the power output by the fuel cell is equal to or greater than a power difference threshold.

[0154] A control method for a fuel cell system according to claim 11, wherein the control method according to claim 10 further comprises: the fuel cell system includes a battery that assists in supplying power from the fuel cell to the inverter; When the power difference is equal to or greater than the power difference threshold, the method includes regulating the power output by the inverter when at least one of the following conditions is met: the charging rate of the battery is less than the charging rate threshold; and the voltage of the battery is less than a voltage threshold.

[0155] A control method for a fuel cell system according to claim (12) is the control method according to any one of claims (1) to (11), the fuel cell system includes an ion exchanger that reduces the conductivity of the coolant; a flow rate of the refrigerant supplied to the ion exchanger is controlled by the opening degree of the control valve; When the conductivity of the refrigerant is equal to or greater than a conductivity threshold, the power output by the inverter is regulated.

[0156] A control method for a fuel cell system according to claim (13) is the control method according to any one of claims (1) to (12), When the power output by the inverter is regulated, the regulation value for regulating the power output by the inverter is gradually reduced.

[0157] A control method for a fuel cell system according to claim 14, wherein the control method according to claim 13, When the restriction on the power output by the inverter is lifted, the restriction value is gradually increased.

[0158] The control program for the fuel cell system of supplementary note (15) causes at least one arithmetic device to execute the control method according to any one of supplementary notes (1) to (14).

[0159] The fuel cell system of appendix (16) an inverter capable of outputting electric power; a fuel cell that generates power to be supplied to the inverter based on the power output by the inverter; a heat exchanger for cooling a refrigerant that cools the fuel cell; a control valve that controls the flow rate of the refrigerant supplied to the heat exchanger by changing the opening degree of the control valve, The control valve includes a power regulation unit that regulates the power output by the inverter based on the opening degree of the control valve.

[0160] The monogeneration device of appendix (17) includes the fuel cell system of appendix (16).

[0161] Although the embodiments of the present invention have been described above, the scope of the present invention is not limited to these, and the invention can be expanded or modified without departing from the spirit of the invention. [Industrial Applicability]

[0162] The present invention can be used in monogeneration systems for industrial and home use, for example. [Explanation of symbols]

[0163] 1. Monogeneration device 2. Fuel cell system 21a fuel cell 22 Battery 23 Inverter 23R regulation value 23Tt Inverter temperature threshold 24a Arithmetic unit 24b1 control program 24d Electricity Regulation Department 25 Cooling material 25Tt Cooling element temperature threshold 214 Ion Exchanger 215 Control valve FN Fan HE heat exchanger K conductivity Kt Conductivity Threshold PD power difference PDt Power Difference Threshold RTt1 First coolant temperature threshold RTt2 Second coolant temperature threshold Rmax Maximum rotation speed S charging rate St Charging Rate Threshold TR target rotation speed TS1 First temperature sensor TS2 Second temperature sensor TS3 Third temperature sensor V Voltage VO opening VOt opening threshold Vt Voltage Threshold

Claims

1. an inverter capable of outputting electric power; a fuel cell that generates power to be supplied to the inverter based on the power output by the inverter; a heat exchanger for cooling a refrigerant that cools the fuel cell; a control valve that controls the flow rate of the refrigerant supplied to the heat exchanger by changing the opening degree of the control valve, A control method for a fuel cell system, comprising: regulating the power output by the inverter based on the opening degree of the control valve.

2. 2. The control method for a fuel cell system according to claim 1, further comprising restricting the power output by the inverter when the opening of the control valve is equal to or greater than an opening threshold value.

3. the fuel cell system includes a first temperature sensor that detects the temperature of the coolant; 3. The control method for a fuel cell system according to claim 2, further comprising regulating the power output by the inverter when the temperature of the refrigerant detected by the first temperature sensor is equal to or higher than a first refrigerant temperature threshold while the opening of the control valve is equal to or higher than the opening threshold.

4. the fuel cell system includes a fan that generates a flow of air that hits the heat exchanger; 4. The control method for a fuel cell system according to claim 3, further comprising setting the target rotation speed of the fan to a maximum rotation speed when the temperature of the coolant detected by the first temperature sensor is equal to or higher than the first coolant temperature threshold value.

5. 5. The control method for a fuel cell system according to claim 4, further comprising regulating the power output by the inverter when the target rotation speed is equal to or higher than the maximum rotation speed in a case where the opening of the control valve is equal to or higher than the opening threshold value.

6. 6. The method for controlling a fuel cell system according to claim 5, further comprising: canceling the restriction on the power output by the inverter when the target rotation speed becomes less than the maximum rotation speed.

7. restricting the power output by the inverter when the temperature of the refrigerant detected by the first temperature sensor is equal to or lower than a second refrigerant temperature threshold; 4. The control method for a fuel cell system according to claim 3, further comprising: relaxing a restriction on the power output by the inverter when the temperature of the coolant is equal to or lower than the second coolant temperature threshold as the opening degree of the control valve increases.

8. the fuel cell system includes a second temperature sensor that detects the temperature of the inverter; 2. The control method for a fuel cell system according to claim 1, further comprising restricting the power output by the inverter when the temperature of the inverter detected by the second temperature sensor is equal to or higher than an inverter temperature threshold value.

9. The fuel cell system includes: a cooling member that cools the inverter; a third temperature sensor that detects the temperature of the cooling member; 2. The control method for a fuel cell system according to claim 1, further comprising restricting the power output by the inverter when the temperature of the cooling member detected by the third temperature sensor is equal to or higher than a cooling member temperature threshold value.

10. 2. The control method for a fuel cell system according to claim 1, further comprising regulating the power output by the inverter when a power difference between the power output by the inverter and the power output by the fuel cell is equal to or greater than a power difference threshold.

11. the fuel cell system includes a battery that assists in supplying power from the fuel cell to the inverter; 11. The control method for a fuel cell system according to claim 10, further comprising regulating the power output by the inverter when at least one of the following conditions is satisfied: the charging rate of the battery is less than the charging rate threshold; and the voltage of the battery is less than a voltage threshold, when the power difference is equal to or greater than the power difference threshold.

12. the fuel cell system includes an ion exchanger that reduces the conductivity of the coolant; a flow rate of the refrigerant supplied to the ion exchanger is controlled by the opening degree of the control valve; The method for controlling a fuel cell system according to claim 1 , further comprising restricting the power output by the inverter when the conductivity of the coolant is equal to or greater than a conductivity threshold value.

13. 2. The control method for a fuel cell system according to claim 1, further comprising gradually reducing a regulated value for regulating the power output by said inverter when regulating the power output by said inverter.

14. 14. The control method for a fuel cell system according to claim 13, further comprising gradually increasing the regulation value when the regulation of the power output by the inverter is lifted.

15. A control program for a fuel cell system, which causes at least one arithmetic device to execute the control method according to any one of claims 1 to 14.

16. an inverter capable of outputting electric power; a fuel cell that generates power to be supplied to the inverter based on the power output by the inverter; a heat exchanger for cooling a refrigerant that cools the fuel cell; a control valve that controls the flow rate of the refrigerant supplied to the heat exchanger by changing the opening degree of the control valve, a power regulation unit that regulates the power output by the inverter based on the opening degree of the control valve;

17. A monogeneration device comprising the fuel cell system of claim 16.

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