Fuel cell system

Abstract

To detect fastening of a relay in a fuel cell system without utilizing a load.SOLUTION: A fuel cell system comprises a fuel cell stack, a battery, a relay, a first voltage sensor for detecting voltage of the fuel cell stack, a second voltage sensor for detecting voltage of the battery, and a controller. The controller is configured to be capable of executing relay fastening detection processing. The fastening detection processing includes: processing of giving the relay a closing command; processing of starting power generation of the fuel cell stack after giving the relay the closing command; processing of giving the relay an opening command when voltage acquired from the first voltage sensor after starting power generation becomes equal to or higher than voltage acquired from the second voltage sensor; and detection processing of determining that the relay is fastened when voltage acquired from the first voltage sensor after giving the relay the opening command is equal to voltage acquired from the second voltage sensor.SELECTED DRAWING: Figure 2

Description

Technical Field

[0001] The technology disclosed in this specification relates to a fuel cell system.

Background Art

[0002] Patent Document 1 describes a fuel cell system. This fuel cell system includes a fuel cell stack, a load connected in parallel with the fuel cell stack, a relay provided between the fuel cell stack and the load, a voltage sensor that detects the voltage of the load, and a control device that acquires the voltage detected by the voltage sensor and controls the opening and closing of the relay.

[0003] Relays such as the above may become inoperable while remaining in the closed state due to their lifespan or excessive current flowing through them causing the relay to weld. In this specification, such an abnormality of the relay is expressed as sticking. In this regard, the control device of Patent Document 1 is configured to be able to execute a process of detecting whether the relay is stuck.

Prior Art Documents

Patent Documents

[0004]

Patent Document Ⅰ

Summary of the Invention

Problems to be Solved by the Invention

[0005] In the technology of Patent Document 1, in order to detect the sticking of the relay, it is necessary to control not only the fuel cell system but also the operation of the load. In order to realize a highly versatile fuel cell system that allows combinations with various loads, a technology that can detect the sticking of the relay without using the load is required.

[0006] In view of the above situation, this specification provides a technology for detecting the sticking of a relay in a fuel cell system without using a load.

Means for Solving the Problem

[0007] The technology disclosed in this specification is embodied in a fuel cell system. This fuel cell system includes a fuel cell stack, a battery connected in parallel with the fuel cell stack and having a maximum output voltage lower than the open-circuit voltage of the fuel cell stack, a relay provided between the fuel cell stack and the battery, a first voltage sensor provided between the relay and the fuel cell stack for detecting the voltage of the fuel cell stack, a second voltage sensor provided between the relay and the battery for detecting the voltage of the battery, and a control device for acquiring the voltages detected from each of the first voltage sensor and the second voltage sensor and controlling the opening and closing of the relay. The control device is configured to be able to execute a stuck detection process for the relay. The stuck detection process includes a process of giving a closing command to the relay, a process of starting the power generation of the fuel cell stack after giving the closing command to the relay, a process of giving an opening command to the relay when the voltage acquired from the first voltage sensor becomes equal to or higher than the voltage acquired from the second voltage sensor after starting the power generation, and a detection process of determining that the relay is stuck when the voltage acquired from the first voltage sensor is equal to the voltage acquired from the second voltage sensor after giving the opening command to the relay.

[0008] In the fuel cell system described above, a stuck detection process of a relay interposed between the fuel cell stack and the battery is executed. In this stuck detection process, first, a closing command is given to the relay, and the fuel cell stack is connected in parallel with the battery via the relay. Then, when the power generation of the fuel cell stack is started, the voltage of the fuel cell stack increases. However, since the fuel cell stack is connected in parallel with the battery, the voltage of the fuel cell stack becomes equal to the voltage of the battery. Since the maximum output voltage of the battery is lower than the open-circuit voltage of the fuel cell stack, the voltage of the battery is lower than the open-circuit voltage of the fuel cell stack. When the voltage of the fuel cell stack becomes equal to the voltage of the battery, an opening command is given to the relay. At this time, if the relay is not stuck, the relay is opened, and the voltage of the fuel cell stack that is continuously generating power becomes higher than the voltage of the battery. On the other hand, if the relay is stuck, the relay is not opened and remains in the closed state, and the voltage of the fuel cell stack is maintained equal to the voltage of the battery despite continuous power generation. In this way, the fuel cell system can detect the sticking of the relay by monitoring the voltage of the fuel cell stack and the voltage of the battery after an opening command is given to the relay. That is, the fuel cell system can detect the sticking of the relay without using a load.

[0009] In a second aspect, in the first aspect, when the state in which the voltage acquired from the first voltage sensor becomes equal to the voltage acquired from the second voltage sensor continues for a predetermined time, it may be determined that the relay is stuck. According to such a configuration, it is possible to accurately detect that the relay is stuck.

[0010] In a third aspect, in the first or second aspect, the control device may execute the stuck detection process when the fuel cell stack is started. According to such a configuration, it is possible to execute the stuck detection process of the relay prior to the operation of the fuel cell stack.

[0011] In a fourth aspect, in any one of the first to third aspects, the control device may execute a sticking detection process at the end of the operation of the fuel cell stack and store the result of the sticking detection process until the next start-up of the fuel cell stack. According to such a configuration, the processes executed at the start-up of the fuel cell stack can be reduced.

[0012] In a fifth aspect, in any one of the first to fourth aspects, the fuel cell system may further include a diode that prevents current from flowing from the battery to the fuel cell stack. According to such a configuration, when the voltage of the fuel cell stack is lower than the voltage of the battery, the current flowing from the battery to the fuel cell stack can be prevented. Thereby, the voltage of the fuel cell stack immediately after the start of power generation can be accurately detected using the first voltage sensor provided between the relay and the fuel cell stack.

Brief Description of the Drawings

[0013]

Figure 1

Figure 2

Figure 3

Embodiments for Carrying Out the Invention

[0014] With reference to the drawings, the fuel cell system 10 of this embodiment will be described. The fuel cell system 10 of this embodiment functions as a power source for supplying power to the outside. Although it is an example, the fuel cell system 10 is a stationary fuel cell system and is fixedly arranged at a predetermined position. However, as another embodiment, the fuel cell system 10 may be mounted on a moving body such as a fuel cell vehicle and function as a power source for supplying power to a traveling motor. The fuel cell system 10 of this embodiment has high versatility and can be used in combination with various loads.

[0015] As shown in FIG. 1, the fuel cell system 10 includes a fuel cell stack 12. The fuel cell stack 12 has a structure in which a plurality of fuel cells are stacked. The fuel cell stack 12 generates electricity by causing a chemical reaction between a fuel gas and an oxidizing gas in the plurality of fuel cells. Although it is an example, in the fuel cell system 10 of this embodiment, hydrogen gas is used as the fuel gas, and air is used as the oxidizing gas. Note that the cooling method of the fuel cell system 10 is not particularly limited, and it may be an air cooling method using ambient air as a refrigerant, or a water cooling method in which cooling water is circulated.

[0016] As shown in FIG. 1, the fuel cell system 10 further includes a control device 14. The control device 14 is a computer device having a processor, a memory, and the like. The control device 14 is communicably connected to the fuel cell stack 12 and can control and monitor the operation of the fuel cell stack 12. The control device 14 calculates the required power to the fuel cell stack 12 based on the required power from the outside. Based on the calculated required power, the control device 14 controls the pressure of the hydrogen gas and the pressure of the air supplied to the fuel cell stack 12, and controls the output power from the fuel cell stack 12. Note that the control device 14 may be configured by a single computer device, or may be configured by a combination of a plurality of computer devices.

[0017] As shown in FIG. 1, the fuel cell system 10 further includes a battery 16 and a relay 18. The battery 16 incorporates a plurality of secondary battery cells, such as, for example, lithium-ion battery cells, nickel-metal hydride battery cells, or all-solid-state battery cells. The maximum output voltage of the battery 16 is lower than the open-circuit voltage VA of the fuel cell stack 12. The battery 16 is connected in parallel with the fuel cell stack 12. The relay 18 is provided between the fuel cell stack 12 and the battery 16. The opening and closing of the relay 18 are controlled by the control device 14. The control device 14 can electrically connect and disconnect the fuel cell stack 12 and the battery 16 by closing and opening the relay 18. Although not particularly limited, the control device 14 is communicably connected to the battery 16 and can control and monitor the operation of the battery 16.

[0018] As shown in FIG. 1, the fuel cell system 10 further includes a first voltage sensor 20, a second voltage sensor 22, and a diode 24. The first voltage sensor 20 is electrically connected to both ends of the fuel cell stack 12. Thereby, the first voltage sensor 20 can detect the voltage V1 of the fuel cell stack 12. The anode of the diode 24 is connected to the positive electrode of the fuel cell stack 12. The cathode of the diode 24 is electrically connected to the positive electrode of the battery 16 via the relay 18. That is, the diode 24 conducts the current flowing from the fuel cell stack 12 to the battery 16 while blocking the current flowing from the battery 16 to the fuel cell stack 12. Therefore, even when the voltage V1 of the fuel cell stack 12 is lower than the voltage V2 of the battery 16 when the fuel cell stack 12 is connected in parallel with the battery 16, no current flows from the battery 16 to the fuel cell stack 12. Thereby, even immediately after starting the power generation of the fuel cell stack 12 in a state where the fuel cell stack 12 is connected in parallel with the battery 16, the first voltage sensor 20 can accurately detect the voltage V1 of the fuel cell stack 12.

[0019] The second voltage sensor 22 is provided between the relay 18 and the battery 16 and is electrically connected to both ends of the battery 16. Thereby, the second voltage sensor 22 can detect the voltage V2 of the battery 16. The control device 14 is communicably connected to each of the voltage sensors 20 and 22 and can monitor the voltages detected by each of the voltage sensors 20 and 22.

[0020] Note that the position of the diode 24 is not limited to the position described in this embodiment. For example, the diode 24 may be provided between the negative electrode of the fuel cell stack 12 and the negative electrode of the battery 16. The diode 24 may be any element that blocks the current flowing from the battery 16 to the fuel cell stack 12 between the first voltage sensor 20 and the second voltage sensor 22. Alternatively, the fuel cell system 10 may have, for example, a switching element instead of the diode 24. In this case, the switching element may be turned off after the fuel cell stack 12 is started until the detection voltage by the first voltage sensor 20 becomes equal to the detection voltage by the second voltage sensor 22. Thereby, the switching element can block the current flowing from the battery 16 to the fuel cell stack 12.

[0021] Next, with reference to FIG. 2, the stuck detection process executed by the control device 14 will be described. In this stuck detection process, when the relay 18 remains in the closed state even after receiving an open command, it is detected that the relay 18 is stuck. The control device 14 in this embodiment is configured to start the stuck detection process when the fuel cell stack 12 is started.

[0022] As shown in FIG. 2, the control device 14 first gives a closing command to the relay 18 (S10). As a result, the relay 18 is closed, and the fuel cell stack 12 is connected in parallel with the battery 16. Thereafter, the control device 14 starts the power generation of the fuel cell stack 12 (S12). As described above, since the diode 24 is interposed between the fuel cell stack 12 and the battery 16, even when the voltage V1 of the fuel cell stack 12 is lower than the voltage V2 of the battery 16, the current flowing from the battery 16 to the fuel cell stack 12 does not flow. Therefore, when the power generation of the fuel cell stack 12 is started, the voltage V1 of the fuel cell stack 12 increases (time T1 in FIG. 3). On the other hand, since the maximum output voltage of the battery 16 is lower than the open-circuit voltage VA of the fuel cell stack 12, the voltage V2 of the battery 16 becomes a predetermined voltage lower than the open-circuit voltage VA of the fuel cell stack 12.

[0023] Next, the control device 14 determines whether or not the voltage V1 of the fuel cell stack 12 is equal to or higher than the voltage V2 of the battery 16 (S14). Here, the voltage V1 of the fuel cell stack 12 is the voltage acquired from the first voltage sensor 20, and the voltage V2 of the battery 16 is the voltage acquired from the second voltage sensor 22. The voltage V1 of the fuel cell stack 12 increases as the power generation of the fuel cell stack 12 progresses. However, when it becomes equal to the voltage V2 of the battery 16 connected in parallel with the fuel cell stack 12, thereafter (i.e., after time T2 in FIG. 3), it shows a constant value.

[0024] If the answer is YES in step S14, the control device 14 gives an open command to the relay 18 (S16), and determines whether the voltage V1 of the fuel cell stack 12 is greater than the voltage V2 of the battery 16 (S18). If the relay 18 is not stuck, the relay 18 is opened (time T3 in FIG. 3). Since the power generation of the fuel cell stack 12 continues, the voltage V1 of the fuel cell stack 12 becomes greater than the voltage V2 of the battery 16. On the other hand, if the relay 18 is stuck, the closed state of the relay 18 is maintained, so the voltage V1 of the fuel cell stack 12 is maintained at a value equal to the voltage V2 of the battery 16 (see the dotted line in FIG. 3). If the answer is NO in step S14, the control device 14 returns to the process of S14. Note that when the relay 18 is opened, the voltage V1 of the fuel cell stack 12 and the voltage V2 of the battery 16 each become the open voltage, which is higher than the closed circuit voltage before the relay 18 is opened. However, in this embodiment, the difference between the open voltage and the closed circuit voltage is very small.

[0025] If the answer is YES in step S18, the control device 14 determines that the relay 18 is not stuck (S20), and ends the stuck determination process shown in FIG. 2. If the answer is NO in step S18, the control device 14 determines whether the state where the voltage V1 of the fuel cell stack 12 is equal to the voltage V2 of the battery 16 has continued for a predetermined time (S22). If the answer is YES in step S22, the control device 14 determines that the relay 18 is stuck (S24), and ends the stuck determination process shown in FIG. 2. If the answer is NO in step S22, the control device 14 returns to the process of step S18.

[0026] As described above, the fuel cell system 10 of this embodiment can execute the stuck detection process of the relay 18 interposed between the fuel cell stack 12 and the battery 16. In this stuck detection process, after an open command is given to the relay 18 (that is, after time T3 in FIG. 3), the stuck of the relay 18 can be detected by monitoring the voltage V1 of the fuel cell stack 12 and the voltage V2 of the battery 16. That is, according to this stuck detection process, the stuck of the relay 18 can be detected without using a load.

[0027] In the above-described embodiment, in the fixing detection process shown in FIG. 2, when the state where the voltage V1 of the fuel cell stack 12 becomes equal to the voltage V2 of the battery 16 continues for a predetermined time (YES in step S22 of FIG. 2), it is determined that the relay 18 is fixed (S24). According to such a configuration, it is possible to accurately detect that the relay 18 is fixed. However, the fixing detection process shown in FIG. 2 does not necessarily need to execute step S22. That is, in the fixing detection process shown in FIG. 2, when it becomes NO in step S18, it may be determined that the relay 18 is fixed (S24).

[0028] In the above-described embodiment, the control device 14 starts the fixing detection process when the fuel cell stack 12 is started. According to such a configuration, it is possible to execute the fixing detection process of the relay 18 prior to the operation of the fuel cell stack 12.

[0029] Alternatively, the control device 14 may execute the fixing detection process at the end of the operation of the fuel cell stack 12 and store the result of the fixing detection process until the next start of the fuel cell stack 12. According to such a configuration, it is possible to reduce the processes executed when the fuel cell stack 12 is started.

[0030] In the above-described embodiment, the fuel cell system 10 includes a diode 24 that prevents the current from flowing from the battery 16 to the fuel cell stack 12. According to such a configuration, when the voltage V1 of the fuel cell stack 12 is lower than the voltage V2 of the battery 16, it is possible to prevent the current from flowing from the battery 16 to the fuel cell stack 12. Thereby, it is possible to accurately detect the voltage V1 of the fuel cell stack 12 immediately after the start of power generation by using the first voltage sensor 20 provided between the relay 18 and the fuel cell stack 12.

[0031] The fuel cell system 10 may have, for example, a switching element instead of the diode 24 described above. In this case, the switching element may be turned off after the fuel cell stack 12 is started until the detected voltage by the first voltage sensor 20 becomes equal to the detected voltage by the second voltage sensor 22. Thereby, the switching element can block the current flowing from the battery 16 to the fuel cell stack 12.

[0032] As described above, several specific examples have been described in detail, but these are merely examples and do not limit the scope of the claims. The technology described in the claims includes various modifications and changes of the specific examples illustrated above. The technical elements described in this specification or the drawings exhibit technical utility alone or in combination.

Explanation of Reference Numerals

[0033] 10: Fuel cell system, 12: Fuel cell stack, 14: Control device, 16: Battery, 18: Relay, 20: First voltage sensor, 22: Second voltage sensor, 24: Diode

Claims

1. A fuel cell stack, a battery connected in parallel with the fuel cell stack and having a maximum output voltage lower than the open-circuit voltage of the fuel cell stack, a relay provided between the fuel cell stack and the battery, a first voltage sensor provided between the relay and the fuel cell stack for detecting the voltage of the fuel cell stack, a second voltage sensor provided between the relay and the battery for detecting the voltage of the battery, a control device that acquires the voltages detected from each of the first voltage sensor and the second voltage sensor and controls the opening and closing of the relay, comprising: the control device is configured to be capable of executing stuck detection processing of the relay, the stuck detection processing includes: a process of giving a closing command to the relay, a process of starting power generation of the fuel cell stack after giving the closing command to the relay, a process of giving an opening command to the relay when the voltage acquired from the first voltage sensor becomes equal to or higher than the voltage acquired from the second voltage sensor after starting the power generation, a detection process of determining that the relay is stuck when the voltage acquired from the first voltage sensor becomes equal to the voltage acquired from the second voltage sensor after giving the opening command to the relay, A fuel cell system including the above.

2. In the stuck detection processing, when the state where the voltage acquired from the first voltage sensor becomes equal to the voltage acquired from the second voltage sensor continues for a predetermined time, it is determined that the relay is stuck. The fuel cell system according to Claim 1.

3. The control device executes the stuck detection processing when starting up the fuel cell stack. The fuel cell system according to Claim 1.

4. The control device executes the stuck detection processing when the operation of the fuel cell stack ends, and stores the result of the stuck detection processing until the next start-up of the fuel cell stack. The fuel cell system according to Claim 1.

5. The fuel cell system according to Claim 1, further comprising a diode for preventing current from flowing from the battery to the fuel cell stack.

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