Fuel cell system

Abstract

In a fuel cell system comprising multiple fuel cell modules, this system suppresses noise generation and deterioration of the fuel cell stack. [Solution] In a fuel cell system FCS comprising a plurality of fuel cell modules FCM and a system control unit Cs, each fuel cell module FCM is equipped with an air compressor ACP, a pressure regulating valve ARV, and a module control unit Cm. The target power generation power sent to each module control unit Cm is set so that, during normal power generation control, the output power of the fuel cell system FCS follows the target output power, and during silent power generation control, the output power of the fuel cell system FCS follows the target output power, and the oxidizer gas is not regulated by each pressure regulating valve ARV.

Description

Technical Field

[0001] The present invention relates to a fuel cell system.

Background Art

[0002] As a fuel cell system, in order to achieve higher output, there is a system including a plurality of fuel cell modules. As a related technology, there is Patent Document 1.

[0003] By the way, when increasing the power generation power of the fuel cell stack provided in the fuel cell module, it is necessary to increase the flow rate of the oxidant gas supplied to the fuel cell stack by an air compressor or increase the pressure of the oxidant gas supplied to the fuel cell stack by a pressure regulating valve provided downstream of the fuel cell stack. Further, when increasing the flow rate of the oxidant gas supplied to the fuel cell stack by an air compressor, since the rotational speed of the motor of the air compressor increases, there is a possibility that the noise generated from the motor increases. Further, when increasing the pressure of the oxidant gas supplied to the fuel cell stack by a pressure regulating valve, since the opening degree of the pressure regulating valve becomes relatively small and discharge pulsation occurs when the oxidant gas is discharged from the pressure regulating valve, there is a possibility that the pressure regulating valve and the hose connected to the pressure regulating valve vibrate and noise is generated due to the discharge pulsation of the oxidant gas.

[0004] Therefore, in the above fuel cell system, since it has a configuration including a plurality of fuel cell modules and the motors of the air compressors and the pressure regulating valves are relatively numerous, there is a concern about an increase in noise during high output.

[0005] Further, when the fuel cell stack continues to generate power for a relatively long time, in a part of the region in the fuel cell stack (for example, the region near the inlet where the oxidant gas flows in), the amount of moisture carried away by the oxidant gas exceeds the amount of moisture generated by the electrochemical reaction, resulting in a dry state, and there is a possibility that the fuel cell stack deteriorates.

Prior Art Documents

Patent Documents

[0006] [Patent Document 1] Japanese Patent Publication No. 2004-178877 [Overview of the project] [Problems that the invention aims to solve]

[0007] One aspect of the present invention is to suppress noise generation and deterioration of the fuel cell stack in a fuel cell system comprising multiple fuel cell modules. [Means for solving the problem]

[0008] One embodiment of the present invention is a fuel cell system comprising a plurality of fuel cell modules and a system control unit, wherein each of the plurality of fuel cell modules comprises a fuel cell stack, an air compressor that supplies oxidant gas to the fuel cell stack, a pressure regulating valve that adjusts the pressure of the oxidant gas supplied to the fuel cell stack, and a module control unit that controls the operation of the air compressor so that the power generated by the fuel cell stack follows a target power generated sent from the system control unit, wherein the target power generated sent to each module control unit is set so that, during normal power generation control, the output power of the fuel cell system follows the target output power, and so that, during silent power generation control, the output power of the fuel cell system follows the target output power, and the oxidant gas is not regulated by each pressure regulating valve.

[0009] This suppresses noise generation by preventing the motor speed of each air compressor from becoming relatively high and by preventing the discharge pulsation of the oxidizer gas from each pressure regulating valve during silent power generation control. Furthermore, since the output power of each fuel cell stack does not become relatively high during silent power generation control, the deterioration of each fuel cell stack can be suppressed. In other words, by using each of the multiple fuel cell stacks within the range where pressure regulating valve adjustment is not required, it is possible to achieve both noise reduction and suppression of fuel cell stack deterioration.

[0010] Furthermore, the system control unit may be configured to send the target power generation to each module control unit during silent power generation control and long-life power generation control, such that when the target output power is below a threshold, the output power of the fuel cell system follows the target output power, the oxidizer gas is not regulated by each pressure regulating valve, and each fuel cell stack repeatedly generates and stops power.

[0011] This makes it possible to suppress the relatively high rotational speed of each air compressor motor and the discharge pulsation of the oxidizer gas discharged from each pressure regulating valve during silent power generation control and long-life power generation control, as well as to suppress each fuel cell stack from continuing to generate power for a relatively long time, thereby further suppressing noise generation and deterioration of the fuel cell stack.

[0012] Furthermore, the system control unit may be configured to send the target power generation to each module control unit during silent power generation control so that the output power of the fuel cell system follows the target output power, and the opening degree of each pressure regulating valve is fully open or at or above a predetermined opening degree.

[0013] Furthermore, one embodiment of the present invention is a fuel cell system comprising a plurality of fuel cell modules and a system control unit, wherein each fuel cell module comprises a fuel cell stack which is a main unit, an auxiliary unit for generating power for the fuel cell stack, and a module control unit which controls the operation of the auxiliary unit so that the power generated by the fuel cell stack follows a target power generated by the system control unit, wherein during normal power generation control, the system control unit sends the target power generated to each module control unit so that the output power of the fuel cell system follows the target output power, and during long-life power generation control, the system control unit sends the target power generated to each module control unit so that the output power of the fuel cell system follows the target output power and each fuel cell stack repeatedly generates and stops power.

[0014] This makes it possible to suppress the continuous power generation of each fuel cell stack for a relatively long period of time during long-life power generation control, thereby suppressing the deterioration of each fuel cell stack.

[0015] Furthermore, the system control unit may be configured to send the target power generation to each module control unit during the long-life power generation control so that the output power of the fuel cell system follows the target output power, and so that at least one of the fuel cell stacks generates power for a first hour while the remaining second fuel cell stacks are stopped for the first hour, followed by the first fuel cell stacks being stopped for a second hour while the second fuel cell stacks generate power for a second hour, and so on. [Effects of the Invention]

[0016] According to the present invention, in a fuel cell system comprising multiple fuel cell modules, it is possible to suppress noise generation and deterioration of the fuel cell stack. [Brief explanation of the drawing]

[0017] [Figure 1]It is a diagram showing an example of a fuel cell system according to an embodiment. [Figure 2] It is a flowchart showing the operation of the system control unit in the first embodiment. [Figure 3] It is a diagram showing an example of information indicating the correspondence relationship between the target output power and the target power generation power. [Figure 4] It is a flowchart showing the operation of the system control unit in the second embodiment. [Figure 5] It is a diagram showing an example of each target power generation power during long-life power generation control. [Figure 6] It is a flowchart showing the operation of the system control unit in the third embodiment.

Mode for Carrying Out the Invention

[0018] Hereinafter, the embodiments will be described in detail based on the drawings.

[0019] FIG. 1 is a diagram showing an example of a fuel cell system according to an embodiment.

[0020] The fuel cell system FCS shown in FIG. 1 is, for example, a stationary generator such as an industrial stationary generator, a household stationary generator, or an emergency stationary generator, and supplies power to a load Lo such as industrial machinery and household appliances.

[0021] Further, the fuel cell system FCS includes a fuel cell module FCMα (first fuel cell module), a fuel cell module FCMβ (second fuel cell module), a relay Re, a power storage device B, a DCDC converter CNVs, a DCAC inverter INV, and a system control unit Cs, and the fuel cell modules FCMα, FCMβ and the power storage device B cooperate to supply desired power to the load Lo. Note that at least one of the power storage device B, the DCDC converter CNVs, and the DCAC inverter INV may be provided outside the fuel cell system FCS.

[0022] If fuel cell module FCMα and fuel cell module FCMβ are not distinguished, they will simply be referred to as fuel cell module FCM. Furthermore, although the fuel cell system FCS shown in Figure 1 has a configuration with two fuel cell modules FCM, it may also be configured with three or more fuel cell modules FCM.

[0023] Relay Re is composed of, for example, an electromagnetic relay, and its open / closed state is controlled by the system control unit Cs. When relay Re is closed, the fuel cell modules FCMα and FCMβ are connected to the energy storage device B and DC-DC converter CNVs, and power can be supplied from fuel cell modules FCMα and FCMβ to the energy storage device B and DC-DC converter CNVs. When relay Re is open, the fuel cell modules FCMα and FCMβ are disconnected from the energy storage device B and DC-DC converter CNVs, and power cannot be supplied from fuel cell modules FCMα and FCMβ to the energy storage device B and DC-DC converter CNVs.

[0024] Energy storage device B is composed of, for example, a lithium-ion capacitor and is connected between relay Re and DC-DC converter CNVs, supplying power to load Lo in cooperation with fuel cell modules FCMα and FCMβ. When power is supplied from energy storage device B to fuel cell modules FCMα, FCMβ or load Lo, energy storage device B is discharged and its charge rate (the ratio of remaining capacity to the full charge capacity of energy storage device B [%]) decreases. Conversely, when power is supplied from fuel cell modules FCMα and FCMβ to energy storage device B, energy storage device B is charged and its charge rate increases.

[0025] The DC-DC converters (CNVs) convert the voltage output from the fuel cell modules FCMα and FCMβ into a predetermined voltage. The power output from the DC-DC converters (CNVs) is then input to the DC-DC inverter (INV).

[0026] The DC-AC inverter (INV) converts the DC power output from the DC-DC converters (CNVs) into AC power and supplies it to the load (Lo).

[0027] The system control unit Cs is composed of, for example, a microcomputer, and sends target power generation power corresponding to the power demanded from the load Lo to the fuel cell modules FCMα and FCMβ, respectively, and controls the operation of the relay Re, DC-DC converters CNVs, and DC-AC inverter INV.

[0028] For example, when the system control unit Cs starts the fuel cell system FCS upon receiving a power generation start request from a user or the like, it assigns fuel cell module FCMα as the fuel cell module FCM for power generation and fuel cell module FCMβ as the standby fuel cell module FCM. Until it receives a power generation stop request from a user or the like, it sends the target power generation amount, determined by the power requested from the load Lo, to fuel cell module FCMα and sends a target power generation amount of zero to fuel cell module FCMβ.

[0029] Furthermore, when the system control unit Cs restarts the fuel cell system FCS upon receiving the next power generation start request, it assigns fuel cell module FCMβ as the fuel cell module FCM for power generation and fuel cell module FCMα as the standby fuel cell module FCM. Until it receives a power generation stop request, it sends the target power generation amount, determined by the power requested from the load Lo, to fuel cell module FCMβ, and sends a target power generation amount of zero to fuel cell module FCMα.

[0030] In other words, the system control unit Cs may be configured to alternately switch between the fuel cell module FCM for power generation and the fuel cell module FCM for standby each time the fuel cell system FCS is started.

[0031] Furthermore, if three or more fuel cell modules (FCMs) are provided in a fuel cell system (FCS), the system may be configured to allocate a number of FCMs corresponding to the required power as power generation modules, and to allocate the remaining FCMs as standby modules.

[0032] The fuel cell modules FCMα and FCMβ each consist of a main unit, the fuel cell stack FC, and several types of auxiliary equipment for generating power from the fuel cell stack FC.

[0033] In other words, the fuel cell module (FCM) is equipped with hydrogen gas system auxiliary equipment such as an injector (INJ) and a hydrogen circulation pump (HP).

[0034] Furthermore, the fuel cell module (FCM) is equipped with air system auxiliary equipment such as an air compressor (ACP) and a pressure regulating valve (ARV).

[0035] Furthermore, the fuel cell module (FCM) is equipped with cooling system auxiliary components such as a water pump (WP), a radiator (R), and a temperature sensor (St).

[0036] Furthermore, the fuel cell module (FCM) is equipped with a DC-DC converter (CNVm) as an electrical auxiliary component.

[0037] Furthermore, the fuel cell module (FCM) also includes a module control unit (Cm).

[0038] A fuel cell stack (FC) consists of multiple fuel cell cells connected in series with each other, and generates electricity through an electrochemical reaction between hydrogen contained in hydrogen gas and oxygen contained in an oxidizing gas (air). The fuel cell cells are, for example, polymer electrolyte fuel cells (PEFCs).

[0039] The injector (INJ) adjusts the flow rate of hydrogen gas supplied from the hydrogen supply unit (HS, such as a cradle) located outside the fuel cell system (FCS) to the fuel cell module (FCM).

[0040] The hydrogen circulation pump (HP) resupplies hydrogen gas discharged from the fuel cell stack (FC) back into the fuel cell stack (FC).

[0041] The air compressor (ACP) compresses the oxidizer gas obtained from outside the fuel cell module (FCM) and supplies it to the fuel cell stack (FC). It should be noted that the noise level increases as the rotational speed of the air compressor (ACP) motor increases.

[0042] The pressure regulating valve (ARV) adjusts the pressure and flow rate of the oxidizer gas supplied to the fuel cell stack (FC). When the pressure of the oxidizer gas supplied to the fuel cell stack (FC) is regulated by the pressure regulating valve (ARV), the smaller the opening of the ARV (the more it is restricted), the higher the pressure of the oxidizer gas. Generally, when the opening of the ARV is relatively small, there is a risk of discharge pulsation occurring in the oxidizer gas passing through the ARV. However, when the opening of the ARV is relatively large, for example, when the ARV is fully open, the oxidizer gas can be discharged from the ARV without generating discharge pulsation. Furthermore, discharge pulsation of the oxidizer gas discharged from the ARV may cause vibration of the ARV and the hoses connected to it, potentially generating noise. In the embodiments described later, the state in which the oxidizing gas is regulated by the pressure regulating valve ARV is defined as a state in which the opening degree of the pressure regulating valve ARV is relatively small, and there is a risk of discharge pulsation occurring in the oxidizing gas discharged from the pressure regulating valve ARV. Also, in the embodiments described later, the state in which the oxidizing gas is not regulated by the pressure regulating valve ARV is defined as a state in which the opening degree of the pressure regulating valve ARV is relatively large, and there is no risk of discharge pulsation occurring in the oxidizing gas discharged from the pressure regulating valve ARV.

[0043] The radiator R exchanges heat with the outside air for cold soot (e.g., water) discharged from the fuel cell stack FC, and then sends it to the water pump WP.

[0044] The water pump WP supplies cold soot cooled by the radiator R to the fuel cell stack FC. The temperature of the fuel cell stack FC is regulated by the cold soot supplied to it.

[0045] The temperature sensor St detects the temperature of the cold soot and sends the detected temperature to the module control unit Cm.

[0046] The DC-DC converter CNVm converts the voltage output from the fuel cell stack FC to a predetermined voltage. The power output from the DC-DC converter CNVm is supplied to each auxiliary device, DC-DC converter CNVs, and energy storage device B.

[0047] The module control unit Cm is composed of, for example, a microcomputer, and controls the operation of each auxiliary device so that the power generated by the fuel cell stack FC follows the target power generation sent from the system control unit Cs. The module control units Cm and the module control units Cm and the system control unit Cs are connected using the same or different communication standards (for example, the CAN (Controller Area Network) communication standard). Furthermore, if the target power generation is zero, the fuel cell stack FC will not generate power, and if the target power generation is greater than zero, the fuel cell stack FC will generate power.

[0048] For example, during normal power generation control, the module control unit Cm determines the stoichiometric ratio of the oxidizer gas corresponding to the target power generation (the ratio of the flow rate of oxidizer gas actually supplied to the fuel cell stack FC to the theoretical flow rate of oxidizer gas required to output the desired current from the fuel cell stack FC), and controls the operation of the inverter circuit that drives the air compressor ACP motor so that the motor speed follows the rotational speed command value corresponding to the determined stoichiometric ratio.

[0049] Furthermore, during normal power generation control, the module control unit Cm determines the stoichiometric ratio of hydrogen gas corresponding to the target power generation (the ratio of the flow rate of hydrogen gas actually supplied to the fuel cell stack FC to the theoretical flow rate of hydrogen gas required to output the desired current from the fuel cell stack FC), and controls the operation of the injector INJ and the inverter circuit that drives the motor of the hydrogen circulation pump HP so that the pressure of the hydrogen gas supplied to the fuel cell stack FC follows the pressure corresponding to the determined stoichiometric ratio.

[0050] Furthermore, as the target power generation increases, the commanded rotation speed of the air compressor (ACP) motor increases, resulting in increased motor noise and a higher noise level perceived by the user. Conversely, as the target power generation decreases, the commanded rotation speed of the air compressor (ACP) motor decreases, resulting in decreased motor noise and a lower noise level perceived by the user. Additionally, when the target power generation is relatively high, the opening of the pressure regulating valve (ARV) becomes relatively small, potentially generating noise from the ARV and hoses. Conversely, when the target power generation is relatively low, the opening of the ARV becomes relatively large, suppressing noise generation from the ARV and hoses.

[0051] <Example 1> Figure 2 is a flowchart showing an example of the operation of the system control unit Cs in Example 1.

[0052] First, when the system control unit Cs receives a power generation start request from a user or the like (step S11: Yes), it switches relay Re from the open state to the closed state, sends a power generation start instruction to each fuel cell module FCM (step S12), and determines whether or not it has received a silent power generation request from a user or the like (step S13). For example, when the "Silent Power Generation Mode" start button displayed on an unillustrated touch panel provided on the fuel cell system FCS is pressed, or when an unillustrated "Silent Power Generation Mode" push button provided on the fuel cell system FCS is pressed by a user, the system control unit Cs enters a state where it has received a silent power generation request. Subsequently, when the "Silent Power Generation Mode" end button displayed on the touch panel is pressed, or when the "Silent Power Generation Mode" push button is pressed again by a user, the system control unit Cs enters a state where it has not received a silent power generation request.

[0053] Next, if the system control unit Cs determines that it has not received a request for silent power generation (step S13: No), it sends a target power generation power to each fuel cell module FCM's module control unit Cm so that the output power of the fuel cell system FCS follows the target output power determined from the requested power from the load Lo, etc., as normal power generation control (step S14).

[0054] On the other hand, when the system control unit Cs determines that it has received a request for silent power generation (step S13: Yes), it sends the target power generation to the module control unit Cm of each fuel cell module FCM so that the output power of the fuel cell system FCS follows the target output power, and so that the oxidizer gas is not regulated by the pressure regulating valve ARV of each fuel cell module FCM (for example, so that the opening degree of each pressure regulating valve ARV is fully open or greater than a predetermined opening degree) (step S15). The predetermined opening degree is, for example, the minimum opening degree of the pressure regulating valve ARV when the oxidizer gas discharge from the pressure regulating valve ARV does not produce pulsation. In other words, as silent power generation control, the system control unit Cs sets the target power generation to each fuel cell module FCM so that the output power of each pressure regulating valve ARV falls within the output range where pressure regulating is not required, and sends the set target power generation to each module control unit Cm.

[0055] Then, if the system control unit Cs has not received a request to stop power generation from a user or the like (step S16: No), it repeats the processes from steps S13 to S16. If it has received a request to stop power generation (step S16: Yes), it sends a power generation stop instruction to the module control unit Cm of each fuel cell module FCM, switches the relay Re from the closed state to the open state, and terminates the power supply from the fuel cell system FCS to the load Lo (step S17).

[0056] Here, we assume a case where the target output power varies within the range of 2kW to 8kW, and the oxidizer gas is not regulated by the ARV pressure regulating valve when the target power generation is within the range of 2kW to 5kW, but the oxidizer gas is regulated by the ARV pressure regulating valve when the target power generation is within the range of 6kW to 8kW. In other words, we assume a case where the noise level perceived by the user is relatively low when the target power generation is within the range of 2kW to 5kW, and relatively high when the target power generation is within the range of 6kW to 8kW.

[0057] Figure 3(a) shows an example of information indicating the correspondence between target output power and target generated power during normal power generation control, and Figure 3(b) shows an example of information indicating the correspondence between target output power and target generated power during silent power generation control. The information shown in Figures 3(a) and 3(b) is assumed to be pre-stored in the memory provided in the system control unit Cs, for example.

[0058] According to the information shown in Figure 3(a), when the target output power is 2kW to 5kW, the target power generation corresponding to fuel cell module FCMα will be the same as the target output power, 2kW to 5kW, and the target power generation corresponding to fuel cell module FCMβ will be 0kW.

[0059] Furthermore, if the target output power is 6kW to 8kW, the target power generation corresponding to the fuel cell module FCMα will be the same as the target output power, 6kW to 8kW, and the target power generation corresponding to the fuel cell module FCMβ will be 0kW.

[0060] In other words, under normal power generation control, only the fuel cell module FCMα generates electricity. Alternatively, during normal power generation control, the fuel cell modules FCMα and FCMβ may be configured to generate electricity alternately.

[0061] Furthermore, according to the information shown in Figure 3(b), when the target output power is 2kW to 5kW, the target power generation corresponding to the fuel cell module FCMα will be the same as the target output power, 2kW to 5kW, and the target power generation corresponding to the fuel cell module FCMβ will be 0kW.

[0062] Furthermore, if the target output power is 6kW, there are three possible patterns: one where the target power generation for fuel cell module FCMα is 2kW and the target power generation for fuel cell module FCMβ is 4kW; another where the target power generation for fuel cell module FCMα is 3kW and the target power generation for fuel cell module FCMβ is 3kW; and a third where the target power generation for fuel cell module FCMα is 4kW and the target power generation for fuel cell module FCMβ is 2kW.

[0063] Furthermore, if the target output power is 7kW, there are several possible patterns: one where the target power generation for fuel cell module FCMα is 2kW and the target power generation for fuel cell module FCMβ is 5kW; another where the target power generation for fuel cell module FCMα is 3kW and the target power generation for fuel cell module FCMβ is 4kW; another where the target power generation for fuel cell module FCMα is 4kW and the target power generation for fuel cell module FCMβ is 3kW; and a third where the target power generation for fuel cell module FCMα is 5kW and the target power generation for fuel cell module FCMβ is 2kW.

[0064] Furthermore, if the target output power is 8kW, there are three possible patterns: one where the target power generation for fuel cell module FCMα is 3kW and the target power generation for fuel cell module FCMβ is 5kW; another where the target power generation for fuel cell module FCMα is 4kW and the target power generation for fuel cell module FCMβ is 4kW; and a third where the target power generation for fuel cell module FCMα is 5kW and the target power generation for fuel cell module FCMβ is 3kW.

[0065] In other words, during silent power generation control, if the target output power is 2kW to 5kW, only the fuel cell module FCMα generates power. If the target output power is 6kW to 8kW, the fuel cell modules FCMα and FCMβ share the target output power of 6kW to 8kW, with each generating 5kW or less of power, so that the oxidizer gas is not regulated by the pressure regulating valve ARV. This prevents the output power of each fuel cell stack FC from becoming relatively large.

[0066] Thus, in the system control unit Cs of Embodiment 1, the target power generation power sent to each module control unit Cm is set so that, during normal power generation control, the output power of the fuel cell system FCS follows the target output power, and during silent power generation control, the power output from the fuel cell system FCS follows the target output power, and the oxidizer gas is not regulated by each pressure regulating valve ARV.

[0067] This suppresses noise generation by preventing the motor speed of each air compressor (ACP) from becoming relatively high and by preventing discharge pulsation of the oxidizer gas discharged from each pressure regulating valve (ARV) during silent power generation control. Furthermore, since the output power of each fuel cell stack (FC) does not become relatively high during silent power generation control, deterioration of each fuel cell stack (FC) can be suppressed. In other words, by using each of multiple fuel cell stacks (FC) within the range where pressure regulating valve (ARV) is not required, both noise reduction and stack deterioration suppression can be achieved.

[0068] <Example 2> Figure 4 is a flowchart showing an example of the operation of the system control unit Cs in Example 2.

[0069] First, when the system control unit Cs receives a power generation start request from a user or the like (step S21: Yes), it switches relay Re from the open state to the closed state, sends a power generation start instruction to each fuel cell module FCM (step S22), and determines whether or not it has received a long-life power generation request from a user or the like (step S23). For example, when the "Long Life Power Generation Mode" start button displayed on an unillustrated touch panel provided on the fuel cell system FCS is pressed, or when an unillustrated "Long Life Power Generation Mode" push button provided on the fuel cell system FCS is pressed by a user, the system control unit Cs enters a state where it has received a long-life power generation request. Subsequently, when the "Long Life Power Generation Mode" end button displayed on the touch panel is pressed, or when the "Long Life Power Generation Mode" push button is pressed again by a user, the system control unit Cs enters a state where it has not received a long-life power generation request.

[0070] Next, if the system control unit Cs determines that it has not received a request for long-life power generation (step S23: No), it sends a target power generation power to each fuel cell module FCM's module control unit Cm as normal power generation control, so that the output power of the fuel cell system FCS follows the target output power determined from the requested power from the load Lo, etc. (step S24).

[0071] On the other hand, when the system control unit Cs determines that it has received a request for long-life power generation (step S23: Yes), it sends a target power generation power to the module control unit Cm of each fuel cell module FCM so that the output power of the fuel cell system FCS follows the target output power, and so that the fuel cell stack FC of each fuel cell module FCM repeatedly generates and stops power (step S25). In other words, during long-life power generation control, the system control unit Cs causes each fuel cell stack FC to generate power intermittently. When a fuel cell stack FC switches from a power generation state to a stopped state, the water generated during power generation spreads to the dry areas within the fuel cell stack FC, reducing the dry areas within the fuel cell stack FC. Therefore, by causing each fuel cell stack FC to generate power intermittently, the dry areas within each fuel cell stack FC can be periodically reduced, thereby suppressing deterioration of the fuel cell stack FC due to drying.

[0072] Then, if the system control unit Cs has not received a request to stop power generation from a user or the like (step S26: No), it repeats the processing from steps S23 to S26. If it has received a request to stop power generation (step S26: Yes), it sends a power generation stop instruction to the module control unit Cm of each fuel cell module FCM, switches the relay Re from the closed state to the open state, and terminates the power supply from the fuel cell system FCS to the load Lo (step S27).

[0073] Figure 5(a) shows an example of the target power generation sent to the module control unit Cm of the fuel cell module FCMα during long-life power generation control, and Figure 5(b) shows an example of the target power generation sent to the module control unit Cm of the fuel cell module FCMβ during long-life power generation control. In the two-dimensional coordinates shown in Figures 5(a) and 5(b), the horizontal axis represents time and the vertical axis represents power. The solid line in Figure 5(a) represents the target power generation sent to the module control unit Cm of the fuel cell module FCMα, and the solid line in Figure 5(b) represents the target power generation sent to the module control unit Cm of the fuel cell module FCMβ.

[0074] First, when the system control unit Cs receives a power generation start request at time t1, it calculates a target output power of 8kW based on the power request from the load Lo, and if it determines that it has not received a long-life power generation request, it switches the target power generation sent to the module control unit Cm of the fuel cell module FCMα from 0kW to 8kW, and leaves the target power generation sent to the module control unit Cm of the fuel cell module FCMβ at 0kW.

[0075] Next, when the system control unit Cs determines at time t2 that it has received a request for long-life power generation, it transitions from normal power generation control to long-life power generation control, and at time t3, it switches the target power generation sent to the module control unit Cm of the fuel cell module FCMα from 8kW to 0kW, and switches the target power generation sent to the module control unit Cm of the fuel cell module FCMβ from 0kW to 8kW.

[0076] Next, if the system control unit Cs continues to receive requests for long-life power generation, at time t4, it switches the target power generation sent to the module control unit Cm of the fuel cell module FCMα from 0kW to 8kW, and switches the target power generation sent to the module control unit Cm of the fuel cell module FCMβ from 8kW to 0kW. At time t5, it switches the target power generation sent to the module control unit Cm of the fuel cell module FCMα from 8kW to 0kW, and switches the target power generation sent to the module control unit Cm of the fuel cell module FCMβ from 0kW to 8kW.

[0077] Next, if the system control unit Cs continues to receive requests for long-life power generation, at time t6, it switches the target power generation sent to the module control unit Cm of the fuel cell module FCMα from 0kW to 8kW, and switches the target power generation sent to the module control unit Cm of the fuel cell module FCMβ from 8kW to 0kW. At time t7, it switches the target power generation sent to the module control unit Cm of the fuel cell module FCMα from 8kW to 0kW, and switches the target power generation sent to the module control unit Cm of the fuel cell module FCMβ from 0kW to 8kW.

[0078] In other words, during long-life power generation control, the system control unit Cs sends target power generation to the module control units Cm of fuel cell modules FCMα and FCMβ so that the power output from the fuel cell system FCS follows the target output power, and so that the fuel cell stack FC (first fuel cell stack) of fuel cell module FCMα generates power for the first hour (for example, from time t4 to time t5) and the fuel cell stack FC (second fuel cell stack) of fuel cell module FCMβ stops for the first hour, then the fuel cell stack FC of fuel cell module FCMα stops for the second hour (for example, from time t5 to time t6) and the fuel cell stack FC of fuel cell module FCMβ generates power for the second hour, and so on. This process is repeated. This allows each fuel cell stack FC to generate power intermittently.

[0079] Then, at time t8, when the system control unit Cs no longer receives requests for long-life power generation, it transitions from long-life power generation control to normal power generation control, and at time t9, it keeps the target power generation sent to the module control unit Cm of the fuel cell module FCMα at 8kW and the target power generation sent to the module control unit Cm of the fuel cell module FCMβ at 0kW.

[0080] Thus, in the system control unit Cs of Embodiment 2, during normal power generation control, the system control unit Cs sends target power generation to each module control unit Cm so that the output power of the fuel cell system FCS follows the target output power, and during long-life power generation control, the system control unit Cs sends target power generation to each module control unit Cm so that the output power of the fuel cell system FCS follows the target output power and each fuel cell stack FC repeatedly generates and stops power.

[0081] This makes it possible to suppress the continuous power generation of each fuel cell stack (FC) for a relatively long period of time during long-life power generation control, thereby suppressing the degradation of each fuel cell stack (FC).

[0082] <Example 3> Figure 6 is a flowchart showing an example of the operation of the system control unit Cs in Example 3.

[0083] First, when the system control unit Cs receives a power generation start request (step S31: Yes), it switches relay Re from the open state to the closed state, sends a power generation start instruction to each fuel cell module FCM (step S32), and determines whether it has received at least one of the silent power generation request and the long-life power generation request (steps S33 to S35).

[0084] Next, if the system control unit Cs determines that it has not received any requests for silent power generation or long-life power generation (step S33: No, step S34: No, step S35: No), it sends a target power generation power to each fuel cell module FCM's module control unit Cm so that the output power of the fuel cell system FCS follows the target output power determined by the power request from the load Lo, etc. (step S36).

[0085] Furthermore, when the system control unit Cs determines that it has received a request for silent power generation (step S33: Yes), it sends the target power generation to the module control unit Cm of each fuel cell module FCM so that the output power of the fuel cell system FCS follows the target output power, and so that the oxidizer gas is not regulated by the pressure regulating valve ARV of each fuel cell module FCM (for example, so that the opening degree of each pressure regulating valve ARV is fully open or above a predetermined opening degree) as silent power generation control (step S37). In other words, as silent power generation control, the system control unit Cs sets the target power generation of each fuel cell module FCM so that the output power of each pressure regulating valve ARV falls within the output range where pressure regulating is not required, and sends the set target power generation to each module control unit Cm.

[0086] Furthermore, if the system control unit Cs determines that it has received a request for long-life power generation (step S33: No, step S34: Yes), it sends a target power generation power to the module control unit Cm of each fuel cell module FCM so that the output power of the fuel cell system FCS follows the target output power, and so that the fuel cell stack FC of each fuel cell module FCM repeatedly generates and stops power (step S38).

[0087] Furthermore, if the system control unit Cs determines that it has received a request for quiet power generation and a request for long-life power generation (step S33: No, step S34: No, step S35: Yes), it determines whether the target output power is below a threshold (step S39). For example, the threshold is the maximum value of the target power generation sent to the module control unit Cm when the oxidizer gas is not regulated by the pressure regulating valve ARV, and in the example shown in Figure 3, it is 5kW.

[0088] Next, if the system control unit Cs determines that the target output power is greater than the threshold (step S39: No), it sends the target power generation to the module control unit Cm of each fuel cell module FCM so that the output power of the fuel cell system FCS follows the target output power and the fuel cell stack FC of each fuel cell module FCM repeatedly generates and stops power (step S38). In other words, if the system control unit Cs determines that the target output power will activate at least one of the pressure regulating valves ARV of each fuel cell module ARV, it will not perform silent power generation control and will only perform long-life power generation control.

[0089] On the other hand, when the system control unit Cs determines that the target output power is below a threshold (step S39: Yes), it sends the target power generation to the module control unit Cm of each fuel cell module FCM as silent power generation control and long-life power generation control, so that the output power of the fuel cell system FCS follows the target output power, the oxidizer gas is not regulated by the pressure regulating valve ARV of each fuel cell module FCM (for example, so that the opening degree of each pressure regulating valve ARV is fully open or above a predetermined opening degree), and the fuel cell stack FC of each fuel cell module FCM repeatedly generates and stops power (step S40). For example, if the target output power is 5kW, the system control unit Cs sends a target power generation of 5kW to the module control unit Cm of fuel cell module FCMα and a target power generation of 0kW to the module control unit Cm of fuel cell module FCMβ, and then repeatedly sends a target power generation of 0kW to the module control unit Cm of fuel cell module FCMα and a target power generation of 5kW to the module control unit Cm of fuel cell module FCMβ.

[0090] Then, if the system control unit Cs has not received a power generation stop request (step S41: No), it repeats the processing from steps S33 to S41. If it has received a power generation stop request (step S41: Yes), it sends a power generation stop instruction to the module control unit Cm of each fuel cell module FCM, switches relay Re from the closed state to the open state, and terminates the power supply from the fuel cell system FCS to load Lo.

[0091] Thus, in Embodiment 3, the system control unit Cs is configured to send the target power generation to each module control unit Cm so that, when silent power generation control and long-life power generation control are performed and the target output power is below a threshold, the output power of the fuel cell system FCS follows the target output power, the oxidizer gas is not regulated by each pressure regulating valve ARV, and each fuel cell stack FC repeatedly generates and stops power.

[0092] This makes it possible to suppress the relatively high rotational speed of the motors of each air compressor (ACP) and the discharge pulsation of the oxidizer gas discharged from each pressure regulating valve (ARV) during silent power generation control and long-life power generation control, as well as to suppress each fuel cell stack (FC) from generating power for a relatively long time, thereby further suppressing noise generation and deterioration of the fuel cell stack (FC). In particular, if power is generated for a long time with each pressure regulating valve (ARV) fully open, the fuel cell stack (FC) may become excessively dry, but by repeatedly generating power and stopping it, it is possible to balance noise generation and deterioration of the fuel cell stack (FC).

[0093] It should be noted that the present invention is not limited to the embodiments described above, and various improvements and modifications are possible without departing from the spirit of the invention.

[0094] For example, in the above embodiment, silent power generation control and long-life power generation control are performed for two fuel cell modules (FCMs), but it is also possible to configure the system to perform silent power generation control and long-life power generation control for three or more fuel cell modules (FCMs). [Explanation of Symbols]

[0095] FCS Fuel Cell System FCMα, FCMβ Fuel Cell Modules Lo load FC fuel cell stack HS Hydrogen Supply Department INJ Injector HP Hydrogen Circulation Pump ACP Air Compressor ARV pressure regulating valve R Radiator WP Water Pump CNVs, CNVm DC-DC converters B Energy storage device INV DC-AC Inverter St temperature sensor Cs System Control Unit Cm Module Control Unit

Claims

1. A fuel cell system comprising multiple fuel cell modules and a system control unit, Each of the plurality of fuel cell modules comprises a fuel cell stack, an air compressor that supplies oxidant gas to the fuel cell stack, a pressure regulating valve that adjusts the pressure of the oxidant gas supplied to the fuel cell stack, and a module control unit that controls the operation of the air compressor so that the power generated by the fuel cell stack follows a target power generated sent from the system control unit. Each of the target power generation values ​​sent to each module control unit is set such that, during normal power generation control, the output power of the fuel cell system follows the target output power, and during silent power generation control, the output power of the fuel cell system follows the target output power, and the oxidizer gas is not regulated by the pressure regulating valves. Fuel cell system.

2. A fuel cell system according to claim 1, During silent power generation control and long-life power generation control, if the target output power is below a threshold, the system control unit sends the target power generation to each module control unit so that the output power of the fuel cell system follows the target output power, the oxidizer gas is not regulated by each pressure regulating valve, and each fuel cell stack repeatedly generates and stops power. Fuel cell system.

3. A fuel cell system according to claim 1 or claim 2, The system control unit sends the target power generation power to each module control unit so that, during silent power generation control, the output power of the fuel cell system follows the target output power, and the opening of each pressure regulating valve is fully open or at a predetermined opening or greater. Fuel cell system.

4. A fuel cell system comprising multiple fuel cell modules and a system control unit, Each of the fuel cell modules comprises a main fuel cell stack, an auxiliary unit for generating power for the fuel cell stack, and a module control unit that controls the operation of the auxiliary unit so that the power generated by the fuel cell stack follows a target power generation sent from the system control unit. The aforementioned system control unit, During normal power generation control, the target power generation is sent to each module control unit so that the output power of the fuel cell system follows the target output power. During long-life power generation control, the target power generation is sent to each module control unit so that the output power of the fuel cell system follows the target output power, and so that each fuel cell stack repeatedly generates and stops power. Fuel cell system.

5. A fuel cell system according to claim 4, During the long-life power generation control, the system control unit sends the target power generation to each module control unit so that the output power of the fuel cell system follows the target output power, and so that at least one of the fuel cell stacks generates power for a first hour while the remaining second fuel cell stacks are stopped for the first hour, followed by the first fuel cell stacks being stopped for a second hour while the second fuel cell stacks generate power for the second hour, and so on. Fuel cell system.

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