Fuel cell system and control method thereof

Abstract

To provide a fuel cell system that can appropriately manage the insulation resistance of the entire system.SOLUTION: In a fuel cell system having a plurality of fuel cell devices whose outputs are connected in parallel, each of the plurality of fuel cell devices includes a power generation unit having a fuel cell stack, and a cooling unit that supplies a coolant to the power generation unit for cooling the fuel cell stack and removes ions contained in the coolant, and the fuel cell system measures at least one of the conductivity of the coolant in each of the plurality of fuel cell devices and the insulation resistance value of the entire fuel cell system.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present disclosure relates to a fuel cell system and a method for controlling a fuel cell system. [Background technology]

[0002] Patent Document 1 discloses a fuel cell system including an adjustment unit that adjusts the conductivity of a cooling medium for cooling a fuel cell, a measurement unit that measures the insulation resistance between the fuel cell system and ground, and a control unit. Patent Document 1 discloses that the control unit in the fuel cell system controls the operation of the adjustment unit so that the conductivity of the cooling medium becomes a predetermined conductivity or less when the insulation resistance is equal to or less than a threshold value during operation of the fuel cell system. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] JP 2023-062300 A Summary of the Invention [Problem to be solved by the invention]

[0004] In a fuel cell system in which a plurality of fuel cell devices are connected in parallel, the insulation resistance decreases as the number of connected fuel cell devices increases.

[0005] The present disclosure provides a fuel cell system that can appropriately manage the insulation resistance of the entire system. [Means for solving the problem]

[0006] According to one aspect of the present disclosure, there is provided a fuel cell system having a plurality of fuel cell devices whose outputs are connected in parallel, each of the plurality of fuel cell devices comprising a power generation unit having a fuel cell stack, and a cooling unit that supplies a coolant to the power generation unit for cooling the fuel cell stack and removes ions contained in the coolant, and the fuel cell system measures at least one of the conductivity of the coolant in each of the plurality of fuel cell devices and the insulation resistance value of the entire fuel cell system. Effect of the Invention

[0007] According to the fuel cell system of the present disclosure, the insulation resistance of the entire system can be appropriately controlled. [Brief description of the drawings]

[0008] [Figure 1] FIG. 1 is a diagram showing an outline of the configuration of a fuel cell system according to a first embodiment. [Diagram 2] FIG. 2 is a flow diagram illustrating the first process in the fuel cell system according to the first embodiment. [Diagram 3] FIG. 3 is a flow diagram illustrating the second process in the fuel cell system according to the first embodiment. [Figure 4] FIG. 4 is a diagram illustrating the operation of the fuel cell system according to the first embodiment. [Diagram 5] FIG. 5 is a diagram illustrating the operation of the fuel cell system according to the first embodiment. [Figure 6] FIG. 6 is a diagram illustrating the output in the fuel cell system according to the first embodiment. [Figure 7] FIG. 7 is a diagram illustrating the refresh operation in the fuel cell system according to the first embodiment. [Figure 8] FIG. 8 is a diagram illustrating the refresh operation in the fuel cell system according to the first embodiment. [Figure 9]FIG. 9 is a diagram showing an outline of the configuration of a modified example of the fuel cell system according to the first embodiment. [Figure 10] FIG. 10 is a flow chart illustrating the operation of a modified example of the fuel cell system according to the first embodiment. [Figure 11] FIG. 11 is a diagram showing an outline of the configuration of a fuel cell system according to the second embodiment. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0009] Hereinafter, embodiments will be described with reference to the accompanying drawings. Note that the present disclosure is not limited to these examples, but is defined by the claims, and is intended to include all modifications within the meaning and scope of the claims.

[0010] In addition, in the description of the specification and drawings of each embodiment, components having substantially the same or corresponding functional configurations may be denoted by the same reference numerals to avoid redundant explanation. In addition, in order to facilitate understanding, the scale of each part in the drawings may differ from the actual scale.

[0011] First Embodiment <Fuel cell system> A fuel cell system according to a first embodiment will be described. The fuel cell system according to the first embodiment includes a plurality of fuel cell devices whose outputs are connected in parallel. Each of the plurality of fuel cell devices included in the fuel cell system according to the first embodiment includes a power generation unit having a fuel cell stack, and a cooling unit that supplies a coolant for cooling the fuel cell stack to the power generation unit and removes ions contained in the coolant. The fuel cell system according to the first embodiment measures at least one of the electrical conductivity of the coolant in each of the plurality of fuel cell devices and the insulation resistance value of the entire fuel cell system.

[0012] The fuel cell system according to the first embodiment will be described with reference to the drawings. Fig. 1 is a diagram showing an outline of the configuration of a fuel cell system 100, which is an example of the fuel cell system according to the first embodiment.

[0013] The fuel cell system 100 is a system that generates power using a plurality of fuel cell devices 1. The fuel cell system 100 supplies the generated power to a supply destination EX.

[0014] The fuel cell system 100 includes multiple fuel cell devices 1, a storage battery 110, an insulation resistance meter 120, and a control unit 130. Note that, although the fuel cell system 100 includes two fuel cell devices 1 in Fig. 1, the number of fuel cell devices in the fuel cell system according to the first embodiment is not limited to two. For example, the fuel cell system according to the first embodiment may include three or more fuel cell devices.

[0015] In the fuel cell system 100, a circuit breaker 50 is provided between the output of each of the plurality of fuel cell devices 1 and the output wiring WL in the fuel cell system 100.

[0016] [Fuel cell device 1] The fuel cell device 1 generates electricity by, for example, causing a chemical reaction between hydrogen and oxygen. The fuel cell device 1 includes a power generation unit 10 and a cooling unit 20. The fuel cell device 1 further includes a conductivity meter 30.

[0017] (Power Generation Section 10) The power generation unit 10 generates electricity by generating power. The power generation unit 10 includes a fuel cell stack 11. The fuel cell stack 11 generates electricity by causing a chemical reaction between supplied hydrogen and oxygen contained in the air. The fuel cell stack 11 is, for example, a polymer electrolyte fuel cell (PEFC). The fuel cell stack 11, which is a polymer electrolyte fuel cell, has a stack structure in which a large number of unit cells are stacked.

[0018] A single cell in the fuel cell stack 11, which is a solid polymer electrolyte fuel cell, includes a membrane electrode assembly (MEA) including a polymer electrolyte membrane and a pair of electrodes provided on both sides of the polymer electrolyte membrane. The polymer electrolyte membrane selectively transports hydrogen ions. Each electrode is formed of a porous material. Each of the pair of electrodes includes a catalyst layer mainly composed of carbon powder supporting a platinum-based metal catalyst (electrode catalyst), and a gas diffusion layer having both air permeability and electronic conductivity. Furthermore, the single cell includes a pair of separators that sandwich the membrane electrode assembly (MEA) from both sides.

[0019] The electricity generated by the fuel cell stack 11 is boosted and output to the outside.

[0020] (Cooling section 20) The fuel cell stack 11 generates heat, for example, when hydrogen and oxygen react to generate electricity. Therefore, the fuel cell stack 11 needs to be cooled. The cooling unit 20 supplies the power generation unit 10 with a coolant RF1 that cools the fuel cell stack 11. The cooling unit 20 also removes ions contained in the coolant RF1.

[0021] The cooling unit 20 includes a pump 21, a heat exchanger 22, an ion exchanger 23, and a three-way valve 24.

[0022] [Pump 21] The pump 21 discharges the coolant RF1 and supplies it to the power generation section 10. The pump 21 is, for example, an axial flow pump.

[0023] [Heat exchanger 22] The heat exchanger 22 exchanges heat between the coolant RF1 and a coolant RF2 supplied from an external cooling device 60. In the heat exchanger 22, the coolant RF1, whose temperature has increased by cooling the fuel cell stack 11, is cooled by heat exchange between the coolant RF1 and the coolant RF2.

[0024] [Ion exchanger 23] The ion exchanger 23 removes impurity ions contained in the coolant RF1 that cools the fuel cell stack 11. By removing ions from the coolant RF1 using the ion exchanger 23, the electrical conductivity of the coolant RF1 can be reduced. By reducing the electrical conductivity of the coolant RF1, electrical interference between the fuel cell stack 11 and the coolant RF1 can be reduced. Furthermore, by reducing the electrical conductivity of the coolant RF1, a decrease in the insulation resistance in the fuel cell device 1 can be suppressed.

[0025] [Three-way valve 24] The three-way valve 24 adjusts the flow rate of the coolant RF1 flowing through the heat exchanger 22 and the flow rate of the coolant RF1 flowing through the ion exchanger 23. Specifically, when the fuel cell device 1 is generating power, the fuel cell device 1 adjusts the three-way valve 24 so that more coolant RF1 flows through the heat exchanger 22. In addition, when the conductivity of the coolant RF1 is high, the fuel cell device 1 adjusts the three-way valve 24 so that more coolant RF1 flows through the ion exchanger 23.

[0026] The three-way valve 24 is a control valve that opens and closes by air or electricity. The opening degree of the three-way valve 24 is controlled by the control unit 130.

[0027] (Conductivity meter 30) The conductivity meter 30 measures the conductivity of the coolant RF1. The result of the measurement by the conductivity meter 30 is output to the control unit 130.

[0028] [Circuit Breaker 50] The circuit breaker 50 switches between connection and disconnection between the multiple fuel cell devices 1 and the output wiring WL in the fuel cell system 100. The circuit breaker 50 is controlled by the control unit 130. The control unit 130 controls the circuit breaker 50 to switch between connection and disconnection of the electric circuit.

[0029] [Storage battery 110] The storage battery 110 stores electricity generated by the multiple fuel cell devices 1 at the output of the fuel cell system 100, and discharges the stored electricity when the output is insufficient. The storage battery 110 is connected to the output of the fuel cell system 100.

[0030] The storage battery 110 is, for example, a lithium ion battery, a lithium ion capacitor, or an electric double layer capacitor. The storage battery 110 may be configured by connecting a plurality of storage batteries in parallel or in series.

[0031] [Insulation Resistance Tester 120] The insulation tester 120 measures the insulation resistance at the output of the fuel cell system 100 between the fuel cell system 100 and ground.

[0032] [Control unit 130] The control unit 130 controls the fuel cell system 100. The control unit 130 controls each of the multiple fuel cell devices 1 and each of the multiple circuit breakers 50. The control unit 130 also acquires the results of measurements made by the multiple conductivity meters 30 and insulation resistance meters 120.

[0033] The control unit 130 controls, for example, the start and stop of the fuel cell system 100 for each of the multiple fuel cell devices 1. The control unit 130 also controls, for example, the output for each of the multiple fuel cell devices 1.

[0034] In addition, the control unit 130 controls the connection and disconnection of the electric circuit in the circuit breaker 50 .

[0035] Furthermore, the control unit 130 obtains the measurement results from the conductivity meter 30 in each of the plurality of fuel cell devices 1. The control unit 130 also obtains the measurement results from the insulation resistance meter 120.

[0036] It should be noted that the fuel cell system according to this embodiment is not limited to the case where the fuel cell system 100 is controlled by a single control unit in the fuel cell system, such as the control unit 130 in the fuel cell system 100. For example, each of the multiple fuel cell devices may be provided with an individual control unit. For example, the control unit in the fuel cell system may send a command to the control unit provided in each of the multiple fuel cell devices, and the control unit provided in each of the multiple fuel cell devices may acquire a measurement value from a conductivity meter in each of the multiple fuel cell devices. Then, the control unit provided in each of the multiple fuel cell devices may send the acquired measurement value from the conductivity meter in each of the multiple fuel cell devices to the control unit provided in the fuel cell system.

[0037] <Processing of the fuel cell system according to the first embodiment> The processing of the fuel cell system according to the first embodiment will be described using a fuel cell system 100, which is an example of the fuel cell system according to the first embodiment. By describing the processing of the fuel cell system according to the first embodiment, a control method for the fuel cell system according to the first embodiment will be described.

[0038] First, there will be described a first process in the fuel cell system according to the first embodiment. Fig. 2 is a flow diagram illustrating the first process in the fuel cell system 100, which is an example of the fuel cell system according to the first embodiment.

[0039] (Step S10) The control unit 130 in the fuel cell system 100 measures the conductivity of the coolant RF1 that cools the fuel cell stack 11 of each of the multiple fuel cell devices 1 using the conductivity meter 30 in each of the multiple fuel cell devices 1.

[0040] (Step S20) Next, the control unit 130 in the fuel cell system 100 determines whether the measured electrical conductivity of the coolant RF1 that cools the fuel cell stack 11 of each of the multiple fuel cell devices 1 is higher than a first threshold value.

[0041] If the electrical conductivity of the coolant RF1 that cools the fuel cell stack 11 of each of the multiple fuel cell devices 1 is higher than the first threshold value (YES in step S20), the control unit 130 proceeds to step S30. If the electrical conductivity of the coolant RF1 that cools the fuel cell stack 11 of each of the multiple fuel cell devices 1 is equal to or lower than the first threshold value (NO in step S20), the control unit 130 ends the process.

[0042] (Step S30) The control unit 130 in the fuel cell system 100 stops the operation of the fuel cell device 1 in which the conductivity of the coolant RF1 that cools the fuel cell stack 11 is higher than the first threshold value. In addition, the control unit 130 in the fuel cell system 100 shuts off the circuit breaker 50 between the fuel cell device 1 in which the conductivity of the coolant RF1 that cools the fuel cell stack 11 is higher than the first threshold value and the output wiring WL.

[0043] (Step S40) The control unit 130 in the fuel cell system 100 executes an ion exchange process. In other words, the fuel cell system 100 performs an ion exchange process. Specifically, the control unit 130 in the fuel cell system 100 controls the three-way valve 24 in the fuel cell device 1 in which the conductivity of the coolant RF1 that cools the fuel cell stack 11 is higher than a first threshold value so as to increase the flow rate of the coolant RF1 flowing through the ion exchanger 23. In other words, the control unit 130 in the fuel cell system 100 controls the three-way valve 24 in the fuel cell device 1 that has stopped operating so as to increase the flow rate of the coolant RF1 flowing through the ion exchanger 23.

[0044] (Step S50) Next, the control unit 130 in the fuel cell system 100 determines whether or not the electrical conductivity of the coolant RF1 that cools the fuel cell stack 11 in the stopped fuel cell device 1 is lower than a second threshold value.

[0045] If the electrical conductivity of the coolant RF1 that cools the fuel cell stack 11 in the stopped fuel cell device 1 is lower than the second threshold value (YES in step S50), the control unit 130 proceeds to step S60. If the electrical conductivity of the coolant RF1 that cools the fuel cell stack 11 in the stopped fuel cell device 1 is equal to or higher than the second threshold value (NO in step S50), the control unit 130 returns to step S50 and repeats the process.

[0046] (Step S60) Next, the control unit 130 in the fuel cell system 100 starts up the stopped fuel cell device 1. Then, the control unit 130 in the fuel cell system 100 stops the ion exchange process when starting up the stopped fuel cell device 1. Specifically, the control unit 130 in the fuel cell system 100 controls the three-way valve 24 in the fuel cell device 1 to be started up so as to increase the flow rate of the coolant RF1 flowing through the heat exchanger 22.

[0047] Next, a description will be given of the second process in the fuel cell system according to the first embodiment. Fig. 3 is a flow diagram illustrating the second process in the fuel cell system 100, which is an example of the fuel cell system according to the first embodiment.

[0048] (Step S110) A control unit 130 in the fuel cell system 100 measures the insulation resistance in the fuel cell system 100 using an insulation resistance meter 120 .

[0049] (Step S120) Next, the control unit 130 in the fuel cell system 100 determines whether the insulation resistance value of the fuel cell system 100 measured in step S110 is lower than a third threshold value.

[0050] If the insulation resistance value in the fuel cell system 100 is lower than the third threshold value (YES in step S120), the control unit 130 proceeds to step S130. If the insulation resistance value in the fuel cell system 100 is equal to or higher than the third threshold value (NO in step S120), the control unit 130 ends the process.

[0051] (Step S130) When the insulation resistance value in the fuel cell system 100 is higher than a first threshold value, the control unit 130 in the fuel cell system 100 stops operation of any of the multiple fuel cell devices 1. In addition, the control unit 130 in the fuel cell system 100 shuts off the circuit breaker 50 between the fuel cell device 1 that has stopped operating and the output wiring WL.

[0052] It should be noted that, for example, among a plurality of fuel cell devices 1, the fuel cell device 1 having the highest conductivity measured by the conductivity meter 30 may be selected as the fuel cell device 1 to be stopped from operating.

[0053] (Step S140) The control unit 130 in the fuel cell system 100 executes an ion exchange step. In other words, the fuel cell system 100 performs an ion exchange process. Specifically, the control unit 130 in the fuel cell system 100 controls the three-way valve 24 in the fuel cell device 1 that has stopped operating so as to increase the flow rate of the coolant RF1 flowing through the ion exchanger 23.

[0054] (Step S150) Next, the control unit 130 in the fuel cell system 100 determines whether or not the electrical conductivity of the coolant RF1 that cools the fuel cell stack 11 in the stopped fuel cell device 1 is lower than a second threshold value.

[0055] If the electrical conductivity of the coolant RF1 that cools the fuel cell stack 11 in the stopped fuel cell device 1 is lower than the second threshold value (YES in step S150), the control unit 130 proceeds to step S160. If the electrical conductivity of the coolant RF1 that cools the fuel cell stack 11 in the stopped fuel cell device 1 is equal to or higher than the second threshold value (NO in step S150), the control unit 130 returns to step S150 and repeats the process.

[0056] (Step S160) Next, the control unit 130 in the fuel cell system 100 starts up the stopped fuel cell device 1. Then, the control unit 130 in the fuel cell system 100 stops the ion exchange process when starting up the stopped fuel cell device 1. Specifically, the control unit 130 in the fuel cell system 100 controls the three-way valve 24 in the fuel cell device 1 to be started up so as to increase the flow rate of the coolant RF1 flowing through the heat exchanger 22.

[0057] In the above example, the insulation resistance of the fuel cell system 100 is measured by the insulation resistance meter 120, but for example, the insulation resistance of the fuel cell system 100 may be estimated based on the measurement results of the conductivity meter 30 in a plurality of fuel cell devices 1. For example, the control unit 130 calculates the insulation resistance of one fuel cell device 1 from a combined resistance when it is assumed that the insulation resistances of the components of the fuel cell device 1 and the insulation resistance of the coolant RF1 are connected in parallel. The control unit 130 may then calculate the calculated insulation resistances of one fuel cell device 1 for each unit, and calculate the combined resistance by assuming that the calculated insulation resistances are connected in parallel, thereby calculating the insulation resistance (insulation resistance value) in the fuel cell system 100.

[0058] For example, if the insulation resistance of a first component device (e.g., a power control unit) that makes up a fuel cell device is RA (unit: megaohms (MΩ)), the insulation resistance of a second component device (e.g., a power conditioner) that makes up the fuel cell device is RB (unit: megaohms (MΩ)), and the insulation resistance of the coolant is RC (unit: megaohms (MΩ)), then the insulation resistance Rfc (unit: megaohms (MΩ)) of one fuel cell device is expressed by Equation 1.

[0059]

number

[0060] The insulation resistance RC of the coolant is calculated, for example, by Equation 2.

[0061]

number

[0062] Here, a, b, and c are each a predetermined constant, and x is electrical conductivity (unit: microsiemens per centimeter (μS / cm)).

[0063] For example, consider a fuel cell system equipped with N fuel cell devices (N is an integer equal to or greater than 2). For each of the N fuel cell devices, the insulation resistance calculated using Equation 1 is Rfc(1), Rfc(2), ..., Rfc(N). If the insulation resistance of the entire fuel cell system is Rs, then the insulation resistance Rs can be calculated using Equation 3.

[0064]

number

[0065] <Operation of the fuel cell system according to the first embodiment> The operation of the fuel cell system according to the first embodiment will be described. Figures 4 and 5 are diagrams for explaining the operation of the fuel cell system 100, which is an example of the fuel cell system according to the first embodiment. Also, Figure 6 is a diagram for explaining the output of the fuel cell system 100, which is an example of the fuel cell system according to the first embodiment.

[0066] FIG. 4 shows the measurement results of the conductivity meter 30 in each of the two fuel cell devices 1 provided in the fuel cell system 100. The horizontal axis of FIG. 4 shows the operating time, and the vertical axis shows the conductivity. Line Lfc1 shows the measurement results of the conductivity meter 30 in one of the two fuel cell devices 1 provided in the fuel cell system 100 (hereinafter referred to as "fuel cell device 1a"). Line Lfc2 shows the measurement results of the conductivity meter 30 in the other of the two fuel cell devices 1 provided in the fuel cell system 100 (hereinafter referred to as "fuel cell device 1b"). The conductivity σs indicates the threshold for starting the ion exchange process (the first threshold in step S20). The conductivity σr indicates the threshold for ending the ion exchange process (the second threshold in step S50 or step S150).

[0067] Fig. 5 shows the measurement results of the insulation resistance meter 120 provided in the fuel cell system 100. The horizontal axis of Fig. 5 shows the operating time, and the vertical axis shows the insulation resistance. A line Lri shows the measurement results of the insulation resistance meter 120 provided in the fuel cell system 100. The insulation resistance value RIs shows the threshold value at which the ion exchange process starts (the third threshold value in step S120).

[0068] FIG. 6 shows the output of each of the two fuel cells provided in the fuel cell system 100. The horizontal axis of FIG. 6 shows the operating time, and the vertical axis shows the output of the fuel cell system 100. Line Lfc1a shows the output in the fuel cell device 1a. Line Lfc2a shows the output in the fuel cell device 1b. Output OPout shows the required output in the fuel cell system 100. Output OP1 shows half the output of the output OPout, and in the fuel cell system 100, each of the fuel cell devices 1a and 1b outputs at the output OP1 during normal operation. Output OP2 shows the power obtained by adding the power required for ion exchange processing to the output OPout. Note that in FIG. 6, the lines Lfc1a and Lfc2a are shifted up and down for ease of viewing.

[0069] When the fuel cell system 100 starts operating, the fuel cell device 1a and the fuel cell device 1b each output an output OP1, as shown by the line Lfc1a and the line Lfc2a, respectively.

[0070] The concentration of ions contained in the coolant RF1 increases as the operating time of the fuel cell system 100 passes. Therefore, as shown by the lines Lfc1 and Lfc2, the electrical conductivity of the coolant RF1 in each of the fuel cell device 1a and the fuel cell device 1b gradually increases as the operating time of the fuel cell system 100 passes.

[0071] 4, at time t1, the electrical conductivity of the coolant RF1 in the fuel cell device 1a becomes higher than the electrical conductivity σs. When the electrical conductivity of the coolant RF1 in the fuel cell device 1a becomes higher than the electrical conductivity σs, the control unit 130 in the fuel cell system 100 stops the operation of the fuel cell device 1a and starts the ion exchange process.

[0072] In the fuel cell system 100, when the operation of the fuel cell device 1a is stopped and the fuel cell device 1a is disconnected from the output by the circuit breaker 50, as shown in FIG. 5, the insulation resistance becomes large at time t1.

[0073] When the operation of the fuel cell device 1a is stopped, the output of the fuel cell device 1b is set to an output OPout that is twice the output OP1 in order to maintain the output in the fuel cell system 100 at the output OPout. In other words, in the fuel cell system 100, the output of the stopped fuel cell device 1a is allocated to the operating fuel cell device 1b. For example, when the fuel cell system according to the first embodiment includes multiple fuel cell devices, the control unit may perform control so as to allocate the output of the stopped fuel cell device to the operating fuel cell device.

[0074] As described later, the fuel cell device 1b may add the power required for the ion exchange process to the output OP2. In other words, in the fuel cell system 100, the power required for the ion exchange process in the stopped fuel cell device may be supplied from the operating fuel cell device. Also, in the fuel cell system 100, the power required for the ion exchange process in the stopped fuel cell device may be supplied from the storage battery 110.

[0075] When the ion exchange process is started in the fuel cell device 1a in the fuel cell system 100, the electrical conductivity of the coolant RF1 in the fuel cell device 1a gradually decreases between time t1 and time t2, as shown by the line Lfc1.

[0076] Then, at time t2, as shown by line Lfc1 in Fig. 4, the electrical conductivity of the coolant RF1 in the fuel cell device 1a becomes lower than the electrical conductivity σr, and the operation of the fuel cell device 1a is resumed. When the output of the fuel cell device 1a is resumed, the insulation resistance decreases, as shown in Fig. 5. Meanwhile, compared to time t1, the insulation resistance at time t2 is higher. When the operation of the fuel cell device 1a is resumed, the outputs of the fuel cell device 1a and the fuel cell device 1b become output OP1, as shown in Fig. 6.

[0077] Furthermore, as shown in Fig. 4, the electrical conductivity of the coolant RF1 in each of the fuel cell device 1a and the fuel cell device 1b gradually increases between time t2 and time t3. When the electrical conductivity of the coolant RF1 in each of the fuel cell device 1a and the fuel cell device 1b increases, the insulation resistance in the entire fuel cell system 100 gradually decreases, as shown by the line Lri in Fig. 5.

[0078] Then, at time t3, the insulation resistance in the fuel cell system 100 becomes lower than the insulation resistance value RIs, as shown by line Lri in Fig. 5. When the insulation resistance in the fuel cell system 100 becomes lower than the insulation resistance value RIs, the control unit 130 in the fuel cell system 100 stops the operation of the fuel cell device 1b, which has high electrical conductivity. Then, the control unit 130 in the fuel cell system 100 stops the operation of the fuel cell device 1b and starts the ion exchange process.

[0079] In the fuel cell system 100, when the operation of the fuel cell device 1b is stopped and the fuel cell device 1b is disconnected from the output by the circuit breaker 50, as shown in FIG. 5, at time t3, the insulation resistance becomes large.

[0080] When the operation of the fuel cell device 1b is stopped, in order to maintain the output of the fuel cell system 100 at the output OPout, the output of the fuel cell device 1a is set to an output OP2, which is twice the output OP1, plus the power required for the ion exchange process. By setting the output to OP2, the output required by the fuel cell system 100 in the fuel cell device 1a is ensured, and the power required for the ion exchange process is also ensured.

[0081] When the ion exchange process is started in the fuel cell device 1b in the fuel cell system 100, the electrical conductivity of the coolant RF1 in the fuel cell device 1b gradually decreases between time t3 and time t4, as shown by the line Lfc2.

[0082] Then, at time t4, as shown by line Lfc2 in Fig. 4, the electrical conductivity of the coolant RF1 in the fuel cell device 1b becomes lower than the electrical conductivity σr, and so operation of the fuel cell device 1b is resumed. When the output of the fuel cell device 1b is resumed, the insulation resistance decreases, as shown in Fig. 5. Meanwhile, compared to time t3, the insulation resistance at time t4 is higher. When the operation of the fuel cell device 1b is resumed, the outputs of the fuel cell device 1a and the fuel cell device 1b become output OP1, as shown in Fig. 6.

[0083] In a fuel cell device equipped with a fuel cell stack, the power generation performance of the fuel cell may deteriorate due to long-term operation. When the power generation performance of the fuel cell device deteriorates, a refresh operation is performed. The refresh operation may be performed to prevent the power generation performance from deteriorating. Since the fuel cell system according to the first embodiment is equipped with multiple fuel cell devices, the multiple fuel cell devices are stopped in sequence to perform the refresh process, thereby enabling the refresh process to be performed while maintaining the output of the fuel cell system.

[0084] 7 and 8 are diagrams illustrating the refresh operation in the fuel cell system 100, which is an example of the fuel cell system according to the first embodiment.

[0085] Each of Figures 7 and 8 shows the output of each of the two fuel cells provided in the fuel cell system 100. The horizontal axis of each of Figures 7 and 8 shows operating time, and the vertical axis shows the output of the fuel cell system 100. Line Lfc1a shows the output of fuel cell device 1a. Line Lfc2a shows the output of fuel cell device 1b. Output OPout shows the required output of fuel cell system 100. Output OP1 shows an output that is half the output OPout, and in the fuel cell system 100, each of fuel cell device 1a and fuel cell device 1b outputs at output OP1 during normal operation.

[0086] During period P1, i.e., from time t11 to time t12, the fuel cell system 100 performs a refresh process on the fuel cell device 1a. During period P2, i.e., from time t13 to time t14, the fuel cell system 100 performs a refresh process on the fuel cell device 1b. The fuel cell system 100 may perform an ion exchange process in addition to the refresh process during each of periods P1 and P2.

[0087] In addition, when the fuel cell device 1a or the fuel cell device 1b is stopped for the refresh process, the control unit 130 may measure the conductivity of the coolant RF1 and determine whether or not to perform the ion exchange process during the refresh process based on the measured conductivity.

[0088] 8, for example, if the electrical conductivity of the coolant RF1 in the fuel cell device 1b does not drop sufficiently during the period P2, the refresh process and the ion exchange process may be extended from time t14 to time t24. In other words, if the electrical conductivity of the coolant RF1 in the fuel cell device 1b does not drop sufficiently during the period P2, the fuel cell system 100 may extend the period P2 to a period P21 and perform the refresh process and the ion exchange process.

[0089] If the conductivity of the coolant RF1 does not decrease even after the ion exchange process is performed, the control unit 130 in the fuel cell system 100 may output a warning or the like to a higher-level system.

[0090] <Modifications of the fuel cell system according to the first embodiment> A modified example of the ion exchange process in the fuel cell system according to the first embodiment will be described.

[0091] Fig. 9 is a diagram showing an outline of the configuration of a modified example of the fuel cell system according to embodiment 1. Specifically, Fig. 9 is a diagram illustrating a fuel cell device 1A which is a modified example of the fuel cell device 1 in the fuel cell system 100 which is an example of the fuel cell system according to embodiment 1.

[0092] The fuel cell apparatus 1A obtains power for the pump 21 and the three-way valve 24 from the output of the fuel cell system 100. The fuel cell apparatus 1A includes a circuit breaker 51 and a circuit breaker 52 in the fuel cell apparatus 1.

[0093] The following describes the operation of the fuel cell system according to the modified embodiment of the first embodiment. Fig. 10 is a flow chart illustrating the operation of the fuel cell system according to the modified embodiment of the first embodiment.

[0094] (Step S210) The control unit 130 in the fuel cell system 100 measures the conductivity of the coolant RF1 that cools the fuel cell stack 11 of each of the plurality of fuel cell devices 1A, using the conductivity meter 30 in each of the plurality of fuel cell devices 1A.

[0095] (Step S220) Next, the control unit 130 in the fuel cell system 100 determines whether the measured electrical conductivity of the coolant RF1 that cools the fuel cell stack 11 of each of the plurality of fuel cell devices 1A is higher than a first threshold value.

[0096] If the electrical conductivity of the coolant RF1 that cools the fuel cell stack 11 of each of the fuel cell devices 1A is higher than the first threshold value (YES in step S220), the control unit 130 proceeds to step S40. If the electrical conductivity of the coolant RF1 that cools the fuel cell stack 11 of each of the fuel cell devices 1A is equal to or lower than the first threshold value (NO in step S220), the control unit 130 returns to step S210 and repeats the process.

[0097] (Step S230) The control unit 130 in the fuel cell system 100 shuts off the circuit breaker 50 connected to the power generation unit 10 in the fuel cell apparatus 1A in which the conductivity of the coolant RF1 is higher than the first threshold value. When the circuit breaker 50 is shut off, a portion of the fuel cell apparatus 1A is disconnected from the output, and the insulation resistance in the fuel cell system 100 increases.

[0098] (Step S240) The control unit 130 in the fuel cell system 100 determines whether the insulation resistance in the fuel cell system 100 is lower than the fourth threshold. If the insulation resistance in the fuel cell system 100 is lower than the fourth threshold (YES in step S240), the control unit 130 proceeds to step S250. If the insulation resistance in the fuel cell system 100 is equal to or higher than the fourth threshold (NO in step S240), the control unit 130 proceeds to step S270.

[0099] The fourth threshold may be, for example, the same value as the third threshold in step S130, or may be a value greater than the third threshold so as to ensure safety.

[0100] (Step S250) If the insulation resistance in the fuel cell system 100 is lower than the fourth threshold value (YES in step S240), the fuel cell system 100 has no margin for insulation resistance, so the control unit 130 shuts off the circuit breakers 51 and 52. When the circuit breakers 51 and 52 are shut off, the fuel cell device 1A is completely disconnected from the output, so the insulation resistance in the fuel cell system 100 further increases.

[0101] (Step S260) The fuel cell system 100 is supplied with power from an external source to carry out the ion exchange process.

[0102] (Step S270) If the insulation resistance in the fuel cell system 100 is equal to or greater than the fourth threshold value (NO in step S240), the fuel cell system 100 has a margin of insulation resistance, and therefore performs the ion exchange process by being internally powered. Specifically, the fuel cell system 100 is supplied with power for the ion exchange process from the fuel cell device 1 or the storage battery 110 in operation.

[0103] According to the fuel cell system of the first embodiment, the insulation resistance of the entire system can be appropriately managed by measuring at least one of the conductivity of the coolant in each of multiple fuel cell devices and the insulation resistance value of the entire fuel cell system.

[0104] Second Embodiment <Fuel cell system> A fuel cell system according to the second embodiment will be described. The fuel cell system according to the second embodiment includes a plurality of power generation units each having a fuel cell stack whose outputs are connected in parallel, and a cooling unit to which the plurality of power generation units are connected, which supplies a coolant for cooling the fuel cell stack and removes ions contained in the coolant. The fuel cell system according to the second embodiment measures at least one of the electrical conductivity of the coolant and the insulation resistance value of the entire fuel cell system.

[0105] The fuel cell system according to the second embodiment will be described with reference to the drawings. Fig. 11 is a diagram showing an outline of the configuration of a fuel cell system 200, which is an example of the fuel cell system according to the second embodiment.

[0106] The fuel cell system 200 is a system that generates power using a fuel cell device 2 that includes a plurality of power generation units 10. The fuel cell system 200 supplies the generated power to a supply destination EX.

[0107] The fuel cell system 200 includes a fuel cell device 2 including multiple power generation units 10, a storage battery 110, an insulation resistance meter 120, and a control unit 130. In Fig. 11, the fuel cell system 200 includes two power generation units 10, but the number of power generation units is not limited to two in the fuel cell system according to the second embodiment. For example, the fuel cell system according to the second embodiment may include three or more power generation units.

[0108] In the fuel cell system 200, a circuit breaker 50 is provided between the output of each of the multiple power generation units 10 and the output wiring WL in the fuel cell system 100. The outputs of the multiple power generation units 10 are connected in parallel.

[0109] For configurations common to the fuel cell system 100, the description of the fuel cell system 100 should be referred to, and detailed description thereof will be omitted here.

[0110] [Fuel cell device 2] The fuel cell device 2 generates electricity by, for example, causing a chemical reaction between hydrogen and oxygen. The fuel cell device 2 includes a plurality of power generation units 10 and a cooling unit 20A. The fuel cell device 2 further includes a conductivity meter 30.

[0111] A plurality of power generation units 10 are connected in series to the cooling unit 20A. Each of the plurality of power generation units 10 includes a shutoff valve 25, a shutoff valve 26, and a shutoff valve 27. The plurality of power generation units 10 may be connected in parallel to the cooling unit 20A, or some of the power generation units 10 may be connected in series and some of the power generation units 10 may be connected in parallel.

[0112] In the fuel cell system 200, when any of the multiple power generating units 10 is operated, the shutoff valves 25 and 26 are opened, and the shutoff valve 27 is closed. On the other hand, when any of the multiple power generating units 10 is stopped in the fuel cell system 200, the shutoff valves 25 and 26 are closed, and the shutoff valve 27 is opened. In other words, when any of the multiple power generating units 10 is stopped in the fuel cell system 200, the coolant RF1 is bypassed in the power generating unit 10 that is stopped. By bypassing the coolant RF1 in the power generating unit 10 that is stopped, the insulation resistance in the fuel cell system 200 can be increased.

[0113] The fuel cell system 200 may stop one of the multiple power generation units 10 based on, for example, the measurement results of the insulation resistance meter 120. The fuel cell system 200 may also estimate the insulation resistance of the fuel cell system 200 based on, for example, the measurement results of the conductivity meter 30, and stop one of the multiple power generation units 10.

[0114] According to the fuel cell system of the second embodiment, by measuring at least one of the electrical conductivity of the coolant and the insulation resistance value of the entire fuel cell system, the insulation resistance of the entire system can be appropriately managed.

[0115] The embodiments disclosed herein should be considered as illustrative and not restrictive in all respects. The above-described embodiments may be omitted, substituted, or modified in various forms without departing from the scope and spirit of the appended claims. [Explanation of symbols]

[0116] 1, 1A, 2 fuel cell device 10 Power Generation Section 11 Fuel Cell Stack 20, 20A cooling section 21 Pump 22 Heat exchanger 23 Ion exchanger 24 Three-way valve 30 Conductivity meter 50 Circuit Breaker 60 Cooling device 100, 200 Fuel Cell System 110 Storage battery 120 Insulation Tester 130 Control section RF1, RF2 Coolant WL output wiring

Claims

1. A fuel cell system including a plurality of fuel cell devices whose outputs are connected in parallel, Each of the plurality of fuel cell devices is a power generation unit including a fuel cell stack; a cooling unit that supplies a coolant to the power generation unit to cool the fuel cell stack and removes ions contained in the coolant; Equipped with measuring at least one of the electrical conductivity of the coolant in each of the plurality of fuel cell devices and an insulation resistance value in the entire fuel cell system; Fuel cell system.

2. A control unit is further provided, When the electrical conductivity of the coolant in any one of the plurality of fuel cell devices is higher than a first threshold value, the control unit performs control so as to stop the fuel cell device in which the electrical conductivity of the coolant is higher than the first threshold value. The fuel cell system according to claim 1 .

3. the control unit controls the stopped fuel cell device to start up when the conductivity of the coolant in the stopped fuel cell device is lower than a second threshold value. The fuel cell system according to claim 2 .

4. A control unit is further provided, the control unit controls one of the plurality of fuel cell devices to be stopped when an insulation resistance value in the fuel cell system is lower than a third threshold value. The fuel cell system according to claim 1 .

5. the control unit acquires the conductivity of the coolant in each of the plurality of fuel cell devices, and controls the fuel cell device having the highest conductivity among the acquired conductivity values ​​to be stopped. The fuel cell system according to claim 4 .

6. A control unit is further provided, the control unit estimates an insulation resistance value of the entire system based on the electrical conductivity of the coolant in each of the plurality of fuel cell devices, and controls one of the plurality of fuel cell devices to be stopped based on the estimated insulation resistance value. The fuel cell system according to claim 1 .

7. the control unit calculates the insulation resistance value from a combined resistance of the insulation resistance of the fuel cell device and the insulation resistance of the cooling liquid. The fuel cell system according to claim 6.

8. The control unit controls the fuel cell device to perform an ion exchange process. The fuel cell system according to any one of claims 2 to 7.

9. The power required for the ion exchange process is supplied from the fuel cell device in operation. The fuel cell system according to claim 8 .

10. a storage battery connected to the output; The power required for the ion exchange process is supplied from the storage battery in operation. The fuel cell system according to claim 8 .

11. The control unit controls the fuel cell device to perform an ion exchange process when the fuel cell device is stopped for a refresh process. The fuel cell system according to claim 8 .

12. the control unit performs control so as to determine whether or not to perform an ion exchange process based on the conductivity of the coolant when the fuel cell device is stopped for a refresh process. The fuel cell system of claim 11.

13. the control unit controls, when stopping the fuel cell device for a refresh process, to extend a period of the stop based on the conductivity of the coolant when performing an ion exchange process. The fuel cell system of claim 11.

14. the control unit controls, when shutting down the fuel cell device, to distribute an output of the fuel cell device to the fuel cell device in operation. The fuel cell system according to any one of claims 2 to 7.

15. The control unit outputs a warning to a host system when the electrical conductivity of the cooling liquid does not decrease even after the ion exchange process. The fuel cell system according to any one of claims 2 to 7.

16. A plurality of power generating units each having a fuel cell stack and whose outputs are connected in parallel; a cooling unit connected to the plurality of power generation units, supplying a cooling liquid for cooling the fuel cell stack and removing ions contained in the cooling liquid, measuring at least one of the electrical conductivity and the overall insulation resistance of the cooling liquid; Fuel cell system.

17. A method for controlling a fuel cell system having a plurality of fuel cell devices whose outputs are connected in parallel, comprising the steps of: Each of the plurality of fuel cell devices is a power generation unit including a fuel cell stack; a cooling unit that supplies a coolant to the power generation unit to cool the fuel cell stack and removes ions contained in the coolant; Equipped with measuring at least one of the electrical conductivity of the coolant in each of the plurality of fuel cell devices and an insulation resistance value in the entire fuel cell system; A method for controlling a fuel cell system.

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