Grounding fault detection system and grounding fault detection method

Abstract

This invention provides a ground fault determination system and a ground fault determination method. The ground fault determination system (20) includes: an acquisition unit (40) that acquires the degradation degree of multiple fuel cell stacks (12) connected in parallel with an inverter (16); a ground fault detection unit (26) that detects the insulation resistance between the inverter and the multiple fuel cell stacks; a first determination unit (422) that simultaneously determines whether a ground fault exists in all fuel cell stacks when the degradation of each fuel cell stack has not progressed; and a second determination unit (423) that sequentially determines whether a ground fault exists for each fuel cell stack when the degradation of at least one fuel cell stack has progressed. Accordingly, it is possible to determine whether a ground fault exists in multiple fuel cell stacks as quickly and accurately as possible.

Description

Technical Field

[0001] This invention relates to a ground fault determination system and method for determining whether a ground fault exists in multiple fuel cell stacks of a fuel cell vehicle connected in parallel. Background Technology

[0002] In recent years, research and development have been conducted on fuel cells that help improve energy efficiency in order to ensure that more people have access to affordable, reliable, sustainable and advanced energy.

[0003] For example, Japanese Patent Publication No. 2014-195372 discloses a fuel cell vehicle. The fuel cell vehicle includes a fuel cell stack (fuel cell), an inverter, and a rotating electric motor. The fuel cell stack supplies current to the rotating electric motor via the inverter. The rotating electric motor is driven using the supplied current. The fuel cell vehicle moves in response to the drive of the rotating electric motor.

[0004] The fuel cell vehicle disclosed in Japanese Patent Publication No. 2014-195372 also includes a ground fault sensor. The ground fault sensor outputs a detection signal corresponding to the insulation resistance between the fuel cell stack and the inverter. Based on this detection signal, it is possible to determine whether a ground fault exists in the fuel cell stack. Summary of the Invention

[0005] Here, assuming multiple fuel cell stacks connected in parallel are mounted on a fuel cell vehicle, the current supplied to the inverter will become very large. As a result, the insulation resistance will decrease, making it difficult to accurately determine whether a grounding fault exists. Japanese Patent Publication No. 2014-195372 does not take these issues into account.

[0006] Considering the above, determining as quickly and accurately as possible whether multiple fuel cell stacks connected in parallel have grounding faults has become a technical problem in fuel cell technology.

[0007] The purpose of this invention is to solve the above-mentioned technical problems.

[0008] The first aspect of the present invention is: a ground fault determination system, which determines whether a ground fault exists in multiple fuel cell stacks connected in parallel with an inverter, characterized in that it has an acquisition unit, a ground fault detection unit, and a ground fault determination unit, wherein the acquisition unit acquires degradation information representing the degradation degree of each fuel cell stack in the plurality of fuel cell stacks; the ground fault detection unit is used to detect the insulation resistance between the inverter and the plurality of fuel cell stacks; the ground fault determination unit determines whether a ground fault exists based on the detection result of the ground fault detection unit, the ground fault determination unit has a first determination unit and a second determination unit, wherein the first determination unit determines whether a ground fault exists in all the fuel cell stacks. If the degradation level of the fuel cell stack is not higher than the specified degradation level, a first determination process is performed; if the degradation level of at least one fuel cell stack is higher than the specified degradation level, a second determination process is performed. The first determination process is based on the detection results of the ground fault detection unit when all fuel cell stacks are connected to the inverter to determine whether all fuel cell stacks have a ground fault. The second determination process is based on the detection results of the ground fault detection unit when multiple fuel cell stacks are sequentially connected to the inverter to determine whether each fuel cell stack has a ground fault.

[0009] The second aspect of the present invention is: a ground fault determination method, wherein a computer determines whether a ground fault exists in a plurality of fuel cell stacks connected in parallel with the inverter based on the detection results of a ground fault detection unit used to detect the insulation resistance between the inverter and a plurality of fuel cell stacks. The method is characterized by comprising: an acquisition step, acquiring degradation information representing the degree of degradation of each of the plurality of fuel cell stacks; a first determination step, performed when the degree of degradation of all the fuel cell stacks is not higher than a predetermined degree, performing a first determination process; and a second determination step, performed when the degree of degradation of at least one fuel cell stack is higher than the predetermined degree, performing a second determination process. The first determination process is performed by the computer based on the detection results of the ground fault detection unit when all the fuel cell stacks are connected to the inverter, determining whether a ground fault exists in all the fuel cell stacks. The second determination process is performed by the computer based on the detection results of the ground fault detection unit when the plurality of fuel cell stacks are sequentially connected to the inverter, determining whether a ground fault exists in each fuel cell stack.

[0010] According to the present invention, it is possible to determine whether multiple fuel cell stacks have grounding faults as quickly and accurately as possible.

[0011] The above-described objectives, features, and advantages should be readily understood through the description of the following embodiments with reference to the accompanying drawings. Attached Figure Description

[0012] Figure 1 This is a structural diagram of the fuel cell vehicle involved in the implementation method.

[0013] Figure 2 This is a structural diagram of a ground fault detection device.

[0014] Figure 3 This is a flowchart illustrating the process of the ground fault determination method according to the illustrative implementation.

[0015] Figure 4 This is a flowchart illustrating the process of the first determination step.

[0016] Figure 5A It is a diagram showing the state of each contactor before the contactor control steps are performed. Figure 5B It is a diagram showing the state of each contactor after the contactor control steps are performed.

[0017] Figure 6 This is a flowchart illustrating the process of the second determination step.

[0018] Figure 7A This is a diagram showing the state of each contactor after the first contactor control step. Figure 7B This is a diagram showing the state of each contactor after the second contactor control step.

[0019] Figure 8 This is a structural diagram of the fuel cell vehicle involved in Modification Example 1. Detailed Implementation

[0020] [Implementation Method]

[0021] Figure 1 This is a structural diagram of the fuel cell vehicle 10 involved in the implementation method.

[0022] The fuel cell vehicle 10 has multiple fuel cell stacks 12, multiple voltage regulators 14, inverters 16, rotary motors 18, batteries 19, and a ground fault detection system 20.

[0023] Each of the multiple fuel cell stacks 12 is a power generation device that generates electricity by utilizing the chemical reaction of hydrogen and oxygen. The multiple fuel cell stacks 12 are connected in series with different voltage regulators 14. The multiple fuel cell stacks 12 output power to the connected voltage regulators 14. Furthermore, the power output from each fuel cell stack 12 is direct current (DC).

[0024] also, Figure 1 The fuel cell vehicle 10 is equipped with two fuel cell stacks 12. However, it is also possible to install three or more fuel cell stacks 12 on the fuel cell vehicle 10.

[0025] Each of the plurality of voltage regulators 14 is a mechanical component used to regulate the current (voltage) input from the corresponding fuel cell stack 12. Each of the plurality of voltage regulators 14 includes, for example, an FCVCU (fuel cell boost converter).

[0026] Multiple voltage regulators 14 are connected in parallel with each other and connected to inverter 16. Therefore, multiple fuel cell stacks 12 are connected in parallel with inverter 16 via multiple voltage regulators 14. Figure 1 Point P in the diagram is the point where the output current of all fuel cell stacks 12 converges.

[0027] Inverter 16 is connected to multiple voltage regulators 14 and rotary motor 18. Direct current (DC) is input to inverter 16 from multiple fuel cell stacks 12 via multiple voltage regulators 14. Inverter 16 converts the input DC to alternating current (AC) and outputs it to rotary motor 18.

[0028] The rotary motor 18 rotates using alternating current input from the inverter 16. The rotational force of the rotary motor 18 is transmitted to the drive wheels of the fuel cell vehicle 10 via a transmission mechanism such as a gearbox. Accordingly, the drive wheels rotate, causing the fuel cell vehicle 10 to move. Illustrations of the transmission mechanism and drive wheels are omitted.

[0029] The rotary motor 18 can also perform regenerative braking to decelerate the fuel cell vehicle 10. In this case, the rotary motor 18 uses the rotational force of the drive wheels to generate electricity.

[0030] Battery 19 is a secondary battery connected between the multiple fuel cell stacks 12 and the inverter 16. Battery 19 stores electricity output from the multiple fuel cell stacks 12 or the rotary motor 18 as needed. Additionally, battery 19 supplies the stored electricity to the rotary motor 18 as needed. The electricity from battery 19 is supplied to the rotary motor 18 via inverter 16.

[0031] The ground fault determination system 20 has multiple contactors 22 (221, 222), a current and voltage detection unit 24, a ground fault detection unit 26, and a ground fault determination device 28.

[0032] Multiple contactors 22 are disposed between multiple fuel cell stacks 12 and the inverter 16. Here, at least one contactor 22 is correspondingly disposed on each of the multiple fuel cell stacks 12. Alternatively, multiple contactors 22 may be correspondingly disposed on a single fuel cell stack 12 (see also...). Figure 8 Each of the multiple contactors 22 is connected in series with its corresponding fuel cell stack 12.

[0033] Furthermore, in the direction of the output current flow of the fuel cell stack 12, Figure 1 Each of the illustrated contactors 22 is positioned upstream of the voltage regulator 14. However, contactors 22 may also be positioned downstream of the voltage regulator 14 (see also...). Figure 8 ).

[0034] Each of the multiple contactors 22 can be controlled by the ground fault detection device 28 to switch to an on or off state. The ground fault detection device 28 will be described in more detail later.

[0035] The "on" state refers to the state in which contactor 22 connects inverter 16 and the corresponding fuel cell stack 12. Figure 1 The illustrated contactor 222 is in the ON state. Each fuel cell stack 12 in the plurality of fuel cell stacks 12 can input current to the inverter 16 when its corresponding contactor 222 is in the ON state.

[0036] During the operation of the fuel cell vehicle 10, all contactors 22 are in the ON state.

[0037] The disconnected state refers to the state in which contactor 22 disconnects inverter 16 from the corresponding fuel cell stack 12. Figure 1 The illustrated contactor 221 is in the open state. With each fuel cell stack 12 in the plurality of fuel cell stacks 12 in the open state, it cannot supply current to the inverter 16.

[0038] During the period when the fuel cell vehicle 10 is stopped (igniter off), all contactors 22 are in the open state.

[0039] The current and voltage detection unit 24 includes, for example, multiple voltage sensors and multiple current sensors, wherein the multiple voltage sensors are used to detect the voltage of each fuel cell stack 12; and the multiple current sensors are used to detect the current of each fuel cell stack 12. The detection results of the current and voltage detection unit 24 are input to the ground fault determination device 28.

[0040] The ground fault detection unit 26 includes, for example, a ground fault sensor for detecting insulation resistance. The ground fault detection unit 26 is connected between point P and inverter 16. The detection result of the ground fault detection unit 26 is input to the ground fault determination device 28.

[0041] Figure 2This is a structural diagram of the ground fault detection device 28.

[0042] The ground fault determination device 28 is a computer that determines whether a ground fault exists in each of the multiple fuel cell stacks 12 based on the detection results of the ground fault detection unit 26. The ground fault determination device 28 has a storage unit 30 and a processing unit 32.

[0043] The storage unit 30 has a storage circuit. The storage circuit includes one or more memory devices, such as RAM (Random Access Memory) and ROM (Read Only Memory).

[0044] The storage unit 30 stores the ground fault determination program 34. The ground fault determination program 34 is a program for implementing the ground fault determination method according to this embodiment.

[0045] Furthermore, the data stored in the storage unit 30 is not limited to the ground fault determination procedure 34. The storage unit 30 can store various types of data as needed. Some of the various types of data stored in the storage unit 30 will be explained later.

[0046] The arithmetic unit 32 has processing circuitry. This processing circuitry may include, for example, one or more processors. However, the processing circuitry of the arithmetic unit 32 may include integrated circuits, such as ASICs (Application-Specific Integrated Circuits), FPGAs (Field-Programmable Gate Arrays), etc. Alternatively, the processing circuitry of the arithmetic unit 32 may include discrete devices.

[0047] The arithmetic unit 32 includes a contactor control unit 36, a start determination unit 38, an acquisition unit 40, a ground fault determination unit 42, and an inhibit unit 44. The contactor control unit 36, the start determination unit 38, the acquisition unit 40, the ground fault determination unit 42, and the inhibit unit 44 are implemented by the processor of the arithmetic unit 32 executing the ground fault determination program 34.

[0048] However, the aforementioned integrated circuits, discrete devices, etc., can realize at least some of the functions of the contactor control unit 36, the start determination unit 38, the acquisition unit 40, the ground fault determination unit 42, and the prohibition unit 44.

[0049] The contactor control unit 36 ​​controls multiple contactors 22, switching each contactor 22 between an on and off state. The contactor control unit 36 ​​controls the multiple contactors 22 in response to a request from the ground fault determination unit 42. The ground fault determination unit 42 will be described in more detail later.

[0050] The start-up determination unit 38 determines whether the fuel cell vehicle 10 has started (igniter on). The fuel cell vehicle 10 is started, for example, by operating the ignition switch provided on the fuel cell vehicle 10. Therefore, the start-up determination unit 38 can determine whether the fuel cell vehicle 10 has started based on whether the ignition switch has been operated.

[0051] The fuel cell vehicle 10 can also be started remotely. For example, the driver holds a terminal capable of communicating with the fuel cell vehicle 10. This terminal is, for example, a smartphone. A start command is sent from the terminal to the fuel cell vehicle 10. The fuel cell vehicle 10 can start in response to the start command. In this case, the start determination unit 38 can determine whether the fuel cell vehicle 10 has started based on whether the fuel cell vehicle 10 has received the start command sent from the terminal.

[0052] The acquisition unit 40 acquires information on degradation and insulation resistance.

[0053] The degradation information indicates the degree of degradation of each fuel cell stack 12. The acquisition unit 40 acquires the degradation information based on the current-voltage characteristics of each fuel cell stack 12. That is, the current-voltage characteristics of each fuel cell stack 12 change as the degradation of the fuel cell stack 12 progresses. Therefore, the degradation progress of the fuel cell stack 12 can be inferred based on the current-voltage characteristics of each fuel cell stack 12.

[0054] The current-voltage characteristics of the fuel cell stack 12 are calculated based on the output voltage of the fuel cell stack 12 and the current output from the fuel cell stack 12 according to the output voltage. The acquisition unit 40 calculates the current-voltage characteristics of each fuel cell stack 12 based on the detection results of the current-voltage detection unit 24 (voltage sensor, current sensor).

[0055] The insulation resistance is obtained based on the detection results of the ground fault detection unit 26. The obtained insulation resistance is the insulation resistance between the inverter 16 and the fuel cell stack 12 connected to the inverter 16. The fuel cell stack 12 connected to the inverter 16 refers to the fuel cell stack 12 connected to the inverter 16 via the contactor 22 in the on state. Fuel cell stacks disconnected from the inverter 16 via the contactor 22 in the off state are not considered fuel cell stacks connected to the inverter 16.

[0056] The ground fault determination unit 42 determines whether a ground fault exists in each fuel cell stack 12 based on the detection results of the ground fault detection unit 26. That is, the ground fault determination unit 42 determines whether a ground fault exists in each fuel cell stack 12 based on the detection results of the ground fault detection unit 26. The ground fault determination unit 42 includes a processing selection unit 421, a first determination unit 422, and a second determination unit 423.

[0057] The processing selection unit 421 selects either the first determination unit 422 or the second determination unit 423 based on the degradation information. Here, the processing selection unit 421 determines whether the degradation level of at least one fuel cell stack 12 is higher than a predetermined degradation level based on the degradation information. The predetermined degradation level can be pre-stored in the storage unit 30.

[0058] If the degradation level of all fuel cell stacks 12 is not higher than a predetermined degradation level, the processing selection unit 421 calls out the first determination unit 422. On the other hand, if the degradation level of at least one fuel cell stack 12 is higher than a predetermined degradation level, the processing selection unit 421 calls out the second determination unit 423.

[0059] The first determination unit 422 determines whether a ground fault exists in the plurality of fuel cell stacks 12 based on the first determination process. The first determination process is the process of determining whether a ground fault exists in all fuel cell stacks 12 based on the detection results of the ground fault detection unit 26 when all fuel cell stacks 12 are turned on with the inverter 16 (see also...). Figure 4 ).

[0060] In order to perform the first determination process, the first determination unit 422 requests the contactor control unit 36 ​​to put all contactors 22 into the energized state. In response to the request of the first determination unit 422, the contactor control unit 36 ​​puts all contactors 22 into the energized state.

[0061] For example, if the insulation resistance detected by the ground fault detection unit 26 is below a threshold when all fuel cell stacks 12 are connected to the inverter 16, the first determination unit 422 determines that a ground fault exists. That is, if the insulation resistance detected by the ground fault detection unit 26 is below a threshold when all fuel cell stacks 12 are outputting current to the inverter 16, the first determination unit 422 determines that all fuel cell stacks 12 have a ground fault. The threshold can be pre-stored in the storage unit 30.

[0062] According to the first determination process, it is possible to simultaneously determine whether all fuel cell stacks 12 connected in parallel have a grounding fault. Therefore, regardless of the number of fuel cell stacks 12, it is possible to determine whether all fuel cell stacks 12 have a grounding fault in a short time.

[0063] The second determination unit 423 determines whether a ground fault exists in the plurality of fuel cell stacks 12 based on the second determination process. The second determination process is based on the detection results of the ground fault detection unit 26 when the plurality of fuel cell stacks 12 are sequentially turned on by the inverter 16, and determines whether a ground fault exists in each fuel cell stack 12 (see also [reference]). Figure 6 ).

[0064] In order to perform the second determination process, (1) the second determination unit 423 selects one of the multiple fuel cell stacks 12 and requests the contactor control unit 36 ​​to turn on only the contactor 22 corresponding to the selected fuel cell stack 12. The contactor control unit 36 ​​appropriately controls the multiple contactors 22 to turn on the contactor 22 corresponding to the selected fuel cell stack 12 and to turn off the contactor 22 corresponding to the unselected fuel cell stack 12. Accordingly, among the multiple fuel cell stacks 12, only the selected fuel cell stack 12 is connected to the inverter 16.

[0065] Next, (2) the second determination unit 423 determines whether the fuel cell stack 12 has a ground fault based on the insulation resistance detected when only the selected fuel cell stack 12 and the inverter 16 are turned on. For example, if the insulation resistance detected by the ground fault detection unit 26 when only the selected fuel cell stack 12 and the inverter 16 are turned on is below a threshold, the second determination unit 423 determines that the fuel cell stack 12 has a ground fault.

[0066] The second determination unit 423 repeatedly performs (1) and (2) above while changing the fuel cell pack 12 to be selected. There is no particular limitation on the order in which multiple fuel cell packs 12 are selected.

[0067] According to the second determination process, even if the deterioration of at least one of the multiple fuel cell stacks 12 progresses, it is possible to accurately determine whether each fuel cell stack 12 has a grounding fault.

[0068] That is, the insulation resistance of the fuel cell stack 12 decreases as the fuel cell stack 12 deteriorates. When multiple fuel cell stacks 12 are connected in parallel, because the insulation resistance of at least one fuel cell stack 12 decreases, the insulation resistance detected by the ground fault detection unit 26 tends to decrease when all fuel cell stacks 12 are turned on with the inverter 16. As a result, in the determination method based on the first determination process, a fuel cell stack 12 that is not considered to have a ground fault may be mistakenly determined to have one. However, according to the second determination process, it is possible to determine whether a ground fault exists for each fuel cell stack 12. Therefore, regardless of the degree of deterioration of each fuel cell stack 12, it is possible to accurately determine whether a ground fault exists.

[0069] Furthermore, even if the degradation level of all fuel cell stacks 12 is not higher than the specified degradation level, and the first determination unit 422 determines that a grounding fault exists, the second determination unit 423 will also determine whether a grounding fault exists based on the second determination process.

[0070] Therefore, when the degradation level of all fuel cell stacks 12 does not exceed the specified degradation level, it is possible to more accurately determine whether a grounding fault exists when it is suspected. Furthermore, it is possible to investigate which of the multiple fuel cell stacks 12 has a grounding fault.

[0071] If the determination result of the first determination unit 422 is different from the determination result of the second determination unit 423, the ground fault determination unit 42 will process the determination result of the second determination unit 423 as the correct determination result.

[0072] Therefore, it is assumed that even if the first determination unit 422 makes a wrong determination, the ground fault determination unit 42 can still obtain the correct determination result.

[0073] If the first determination unit 422 determines that a grounding fault exists, and the second determination unit 423 determines that no grounding fault exists, the prohibition unit 44 prohibits the first determination unit 422 from determining whether a grounding fault exists. When the first determination unit 422 is prohibited from determining whether a grounding fault exists, the second determination unit 423 determines whether a grounding fault exists based on the second determination process, regardless of the degree of degradation of all fuel cell stacks 12.

[0074] Therefore, knowing that it is difficult to simultaneously and accurately determine whether all fuel cell stacks 12 have grounding faults, it is possible to determine whether each fuel cell stack 12 has a grounding fault, regardless of the degree of degradation of all fuel cell stacks 12. Thus, it is possible to continue determining whether each fuel cell stack 12 has a grounding fault as quickly and accurately as possible.

[0075] According to the aforementioned ground fault determination system 20, it is possible to determine as quickly as possible whether any of the fuel cell stacks 12 have a ground fault. Furthermore, according to the aforementioned ground fault determination system 20, it is possible to accurately determine whether any of the fuel cell stacks 12 have a ground fault.

[0076] The determination result of the ground fault determination unit 42 (first determination unit 422, second determination unit 423) can be notified to the driver of the fuel cell vehicle 10. Accordingly, the driver can be informed of whether a ground fault exists before the fuel cell vehicle 10 starts.

[0077] The determination result of the ground fault determination unit 42 is displayed, for example, on a display device installed on the fuel cell vehicle 10. This display device is, for example, an LCD screen installed inside the passenger compartment of the fuel cell vehicle 10.

[0078] Figure 3 This is a flowchart illustrating the process of the ground fault determination method according to the illustrative implementation.

[0079] The ground fault detection system 20 is capable of performing... Figure 3 A ground fault determination method is provided. The ground fault determination method includes an initiation determination step S1, an acquisition step S2, a processing selection step S3, a first determination step S4, a second determination step S5, a third determination step S6, and a prohibition step S7.

[0080] In the start-up determination step S1, the start-up determination unit 38 determines whether the fuel cell vehicle 10 has been started. If the fuel cell vehicle 10 has been started, the acquisition step S2 is executed.

[0081] In step S2, the acquisition unit 40 acquires degradation information. The degradation information indicates the degree of degradation of each fuel cell stack 12 in the plurality of fuel cell stacks 12.

[0082] In the processing selection step S3, the processing selection unit 421 determines whether the degradation level of all fuel cell stacks 12 is not higher than a predetermined degradation level. Based on the determination result, the processing selection unit 421 selects either the first determination process or the second determination process.

[0083] If the degradation level of all fuel cell stacks 12 is not higher than a predetermined degradation level (S3: Yes), the processing selection unit 421 selects the first determination process. In this case, the first determination step S4 is executed after the processing selection step S3. If the degradation level of at least one fuel cell stack 12 is higher than a predetermined degradation level (S3: No), the processing selection unit 421 selects the second determination process. In this case, the second determination step S5 is executed after the processing selection step S3.

[0084] In the first determination step S4, the first determination unit 422 performs the first determination process.

[0085] Figure 4 This is a flowchart illustrating the process of the first determination step S4.

[0086] The first determination step S4 includes the contactor control step S41 and the ground fault determination step S42.

[0087] Figure 5A This is a diagram showing the state of each contactor 22 before the contactor control step S41 is performed. Figure 5BThis is a diagram showing the state of each contactor 22 after the contactor control step S41 is performed.

[0088] All contactors 22 are immediately disconnected after the fuel cell vehicle 10 is started. Figure 5A In contactor control step S41, the contactor control unit 36, in response to the request from the first determination unit 422, switches all contactors 22 to the ON state. Figure 5B ).

[0089] In the ground fault determination step S42, the first determination unit 422 determines whether any of the fuel cell stacks 12 have a ground fault. This determination can be made simultaneously based on the insulation resistance detected by the ground fault detection unit 26 when all contactors 22 are in the ON state.

[0090] Therefore, when performing the first determination step S4, regardless of the number of fuel cell stacks 12, it is possible to determine whether all fuel cell stacks 12 have grounding faults in a short time.

[0091] The result of the ground fault determination step S42 is processed as the result of the first determination step S4. In the ground fault determination step S42, if it is determined that none of the fuel cell stacks 12 have a ground fault (S4: No), the ground fault determination method ends. In the ground fault determination step S42, if it is determined that all fuel cell stacks 12 have a ground fault (S4: Yes), the third determination step S6 is executed after the first determination step S4.

[0092] In the second determination step S5, the second determination unit 423 performs the second determination process.

[0093] Figure 6 This is a flowchart illustrating the process of the second determination step S5.

[0094] The second determination step S5 includes the battery pack selection step S51, the contactor control step S52, the ground fault determination step S53, and the determination end step S54.

[0095] In the battery pack selection step S51, the second determination unit 423 selects a fuel cell pack 12 as the object to determine whether a grounding fault exists. For example, fuel cell pack 121 is selected first.

[0096] Figure 7A This is a diagram showing the state of each contactor 22 after the contactor control step S52 (first time) is performed. Furthermore, the state of each contactor 22 before the contactor control step S52 (first time) is also shown. Figure 5A same.

[0097] In the contactor control step S52, the contactor control unit 36 ​​responds to the request of the second determination unit 423 by switching the contactor 221 corresponding to the selected fuel cell stack 121 to the on state.

[0098] In the ground fault determination step S53, the second determination unit 423 determines whether the selected fuel cell stack 12 has a ground fault.

[0099] In the determination end step S54, the second determination unit 423 determines whether a grounding fault has been determined for all fuel cell stacks 12.

[0100] If there are still fuel cell stacks 12 that have not been determined to have a grounding fault (S5: No), the battery stack selection step S51 to the grounding fault determination step S53 are executed again. However, in the re-executed battery stack selection step S51, the fuel cell stack 12 that has not been determined to have a grounding fault is selected (122).

[0101] Figure 7B This is a diagram showing the state of each contactor 22 after the contactor control step S52 (second time) is performed.

[0102] In the contactor control step S52 performed after the second time, the contactor control unit 36 ​​switches the contactor 22 corresponding to the newly selected fuel cell stack 122 to the on state.

[0103] However, in the contactor control step S52 performed after the second time, the contactor control unit 36 ​​also controls the contactor 22 (221) that was switched to the on state in the previous contactor control step S52 to the off state again. Accordingly, in the contactor control step S52 after the second time, only the selected fuel cell stack 12 among the multiple fuel cell stacks 12 is connected to the inverter 16.

[0104] If all fuel cell stacks 12 have been checked for grounding faults (S54: Yes), the second determination step S5 ends. If at least one fuel cell stack 12 is determined to have a grounding fault, the determination result of the second determination step S5 is that a grounding fault exists (S5: Yes).

[0105] By performing the second determination step S5, even if at least one of the multiple fuel cell stacks 12 experiences deterioration, it is possible to accurately determine whether each fuel cell stack 12 has a ground fault. When the second determination step S5 ends, the ground fault determination method terminates.

[0106] In the third determination step S6, the second determination unit 423 performs the second determination process, which is the same as in the second determination step S5 (see also...). Figure 7A , Figure 7B Therefore, when the degradation level of all fuel cell stacks 12 does not exceed the specified degradation level, it is possible to more accurately determine whether a grounding fault exists when a grounding fault is suspected.

[0107] If the determination result of the third determination step S6 is the same as the determination result of the first determination step S4, the ground fault determination method ends. That is, in the third determination step S6, if it is determined that all fuel cell stacks 12 have ground faults, the ground fault determination method ends.

[0108] On the other hand, if the determination result of the third determination step S6 is different from the determination result of the first determination step S4, the prohibition step S7 is executed after the third determination step S6. That is, in the third determination step S6, if it is determined that at least one fuel cell stack 12 does not have a grounding fault, the prohibition step S7 is executed.

[0109] In the prohibition step S7, the prohibition unit 44 prohibits the execution of the first determination step S4 during subsequent ground fault determination methods. In this case, during subsequent ground fault determination methods, only the second determination step S5 of the first determination step S4 and the second determination step S5 is performed. In this case, since the processing selection unit 421 does not select the first processing step, the processing selection step S3 can be skipped.

[0110] By executing the prohibition step S7, it is possible to accurately continue to determine whether each fuel cell stack 12 has a grounding fault.

[0111] Furthermore, after executing the prohibition step S7, the process of performing a second determination process (S6) after the first determination process (S4) is prohibited. That is, the determination process is prohibited from being re-executed. Accordingly, the time required for the ground fault determination method that starts after executing the prohibition step S7 can be shortened.

[0112] The ground fault determination method ends upon completion of the prohibition step S7. Furthermore, the determination result of the ground fault determination method after the prohibition step S7 is performed is based on the determination result of the third determination step S6.

[0113] [Variation Example]

[0114] The following describes variations of the embodiments described above. However, in the following description, descriptions that are repeated in the embodiments described above will be omitted as much as possible. Structural elements described in the embodiments above will be marked with the same reference numerals as in the embodiments described above, unless otherwise specified.

[0115] (Variation Example 1)

[0116] Figure 8 This is a structural diagram of the ground fault determination system 20 involved in Modified Example 1.

[0117] Multiple contactors 22 can be connected in series on each of the multiple fuel cell stacks 12. In this case, the multiple contactors 22 may include a contactor 22 configured between the fuel cell stack 12 and the voltage regulator 14 and a contactor 22 configured between the voltage regulator 14 and the inverter 16.

[0118] According to this variation, for example, even if one of the multiple contactors 22 corresponding to the same fuel cell stack 12 becomes uncontrollable in the connected state, it is possible to determine whether a grounding fault exists by switching the other contactors 22 to the disconnected state.

[0119] (Variation Example 2)

[0120] The timing for the ground fault determination system 20 to determine whether a ground fault exists in multiple fuel cell stacks 12 is not limited to when the fuel cell vehicle 10 has been started.

[0121] For example, the ground fault detection system 20 can determine whether a ground fault exists in multiple fuel cell stacks 12 when the fuel cell vehicle 10 is parked (igniter off). Whether the fuel cell vehicle 10 is parked can be determined based on whether the ignition switch is operated.

[0122] According to this variation, the presence of grounding faults in each fuel cell stack 12 is determined when the fuel cell vehicle 10 starts, and is also determined when the fuel cell vehicle 10 stops. Therefore, grounding faults in each fuel cell stack 12 can be detected as early as possible.

[0123] (A combination of multiple variations)

[0124] The aforementioned variations can be appropriately combined within a non-contradictory range.

[0125] [Technical solutions obtained from implementation methods]

[0126] The following describes the technical solutions that can be obtained from the above embodiments and variations.

[0127] <First Technical Solution>

[0128] The first technical solution is: a ground fault determination system (20) that determines whether a ground fault exists in a plurality of fuel cell stacks (12) connected in parallel with an inverter (16). The system is characterized by having an acquisition unit (40), a ground fault detection unit (26), and a ground fault determination unit (42). The acquisition unit acquires degradation information representing the degree of degradation of each fuel cell stack in the plurality of fuel cell stacks. The ground fault detection unit detects the insulation resistance between the inverter and the plurality of fuel cell stacks. The ground fault determination unit determines whether a ground fault exists based on the detection result of the ground fault detection unit. The ground fault determination unit has a first determination unit (422) and a second determination unit (423). The first determination unit performs a first determination process when the degradation level of all the fuel cell stacks is not higher than a predetermined degradation level; the second determination unit performs a second determination process when the degradation level of at least one fuel cell stack is higher than the predetermined degradation level. The first determination process is based on the detection results of the ground fault detection unit when all the fuel cell stacks are connected to the inverter to determine whether there is a ground fault in all the fuel cell stacks. The second determination process is based on the detection results of the ground fault detection unit when multiple fuel cell stacks are sequentially connected to the inverter to determine whether there is a ground fault in each fuel cell stack.

[0129] Therefore, it is possible to determine whether multiple fuel cell stacks have grounding faults as quickly and accurately as possible.

[0130] When the first determination unit determines that a ground fault exists, even if the degradation level of all the fuel cell stacks is not higher than the predetermined degradation level, the second determination unit can still determine whether a ground fault exists based on the second determination process. Therefore, when the degradation level of all the fuel cell stacks is not higher than the predetermined degradation level, a ground fault can be more accurately determined when it is suspected.

[0131] If the determination results of the first determination unit and the second determination unit differ, the ground fault determination unit can take the determination result of the second determination unit as the correct determination result. Therefore, it is assumed that even if the first determination unit makes a mistake, a correct determination result can still be obtained.

[0132] The first technical solution may include a prohibition unit (44). When the first determination unit determines that a ground fault exists, and the second determination unit determines that a ground fault does not exist, the prohibition unit prohibits the first determination unit from determining whether a ground fault exists. When the first determination unit is prohibited from determining whether a ground fault exists, the second determination unit determines whether a ground fault exists based on the second determination process, regardless of the degree of degradation of all the fuel cell stacks. Accordingly, it is possible to accurately continue determining whether each fuel cell stack has a ground fault. Furthermore, since re-execution of the determination process is prohibited, the time required until the final determination result of whether each fuel cell stack has a ground fault can be shortened.

[0133] The first technical solution can be: the ground fault determination system is installed in a fuel cell vehicle (10), the fuel cell vehicle has the inverter and multiple fuel cell stacks, and the ground fault determination system determines whether there is a ground fault in the multiple fuel cell stacks when the fuel cell vehicle is started. Accordingly, it is possible to determine whether there is a ground fault in the multiple fuel cell stacks before the fuel cell vehicle starts.

[0134] <Second Technical Solution>

[0135] The second technical solution is: a ground fault determination method, wherein a computer determines whether a ground fault exists in the plurality of fuel cell stacks connected in parallel with the inverter based on the detection results of a ground fault detection unit (26) used to detect the insulation resistance between the inverter (16) and the plurality of fuel cell stacks (12), characterized in that it includes: an acquisition step (S2), acquiring degradation information representing the degradation degree of each of the plurality of fuel cell stacks; a first determination step (S4), performing the first determination process if the degradation degree of all the fuel cell stacks is not higher than a predetermined degradation degree; and a second determination step (S5). The determination step (S5) is performed when the degradation level of at least one of the fuel cell stacks is higher than the predetermined degradation level. A second determination process is then performed. The first determination process is performed by the computer based on the detection results of the ground fault detection unit when all the fuel cell stacks are connected to the inverter to determine whether there is a ground fault in all the fuel cell stacks. The second determination process is performed by the computer based on the detection results of the ground fault detection unit when multiple fuel cell stacks are sequentially connected to the inverter to determine whether there is a ground fault in each fuel cell stack.

[0136] Therefore, it is possible to determine whether multiple fuel cell stacks have grounding faults as quickly and accurately as possible.

[0137] Furthermore, the present invention is not limited to the above description, and various structures may be adopted without departing from the spirit of the present invention.

Claims

1. A ground fault determination system (20) for determining whether a ground fault exists in a plurality of fuel cell stacks (12) connected in parallel with an inverter (16), characterized in that, It has an acquisition unit (40), a ground fault detection unit (26), and a ground fault determination unit (42), wherein, The acquisition unit acquires degradation information representing the degree of degradation of each fuel cell stack in the plurality of fuel cell stacks; The grounding fault detection unit is used to detect the insulation resistance between the inverter and the multiple fuel cell stacks; The ground fault determination unit determines whether a ground fault exists based on the detection results of the ground fault detection unit. The ground fault determination unit has a first determination unit (422) and a second determination unit (423), wherein, The first determination unit performs a first determination process if the degree of degradation of all the fuel cell stacks does not exceed a predetermined degree of degradation. The second determination unit performs a second determination process if the degradation level of at least one of the fuel cell stacks exceeds the predetermined degradation level. The first determination process is based on the detection results of the ground fault detection unit when all the fuel cell stacks are connected to the inverter, to determine whether any of the fuel cell stacks have a ground fault. The second determination process is based on the detection results of the ground fault detection unit when the multiple fuel cell stacks are sequentially connected to the inverter, to determine whether a ground fault exists for each fuel cell stack.

2. The grounding fault determination system according to claim 1, characterized in that, When the first determination unit determines that the grounding fault exists, even if the degradation level of all the fuel cell stacks is not higher than the specified degradation level, the second determination unit will still determine whether the grounding fault exists based on the second determination process.

3. The grounding fault determination system according to claim 2, characterized in that, If the determination results of the first determination unit and the second determination unit are different, the ground fault determination unit shall take the determination result of the second determination unit as the correct determination result.

4. The grounding fault determination system according to claim 3, characterized in that, It also includes a prohibition unit (44), which, when the first determination unit determines that the grounding fault exists, and when the second determination unit determines that the grounding fault does not exist, prohibits the first determination unit from determining whether the grounding fault exists. In the absence of the first determination unit determining whether the ground fault exists, the second determination unit determines whether the ground fault exists based on the second determination process, regardless of the degree of degradation of all the fuel cell stacks.

5. The ground fault determination system according to any one of claims 1 to 4, characterized in that, The ground fault determination system is installed in a fuel cell vehicle (10), which has the inverter and multiple fuel cell stacks. The grounding fault determination system determines whether a grounding fault exists in any of the multiple fuel cell stacks when the fuel cell vehicle is started.

6. A ground fault determination method, wherein a computer determines whether a ground fault exists in the plurality of fuel cell stacks connected in parallel with the inverter based on the detection results of a ground fault detection unit (26) used to detect the insulation resistance between the inverter (16) and the plurality of fuel cell stacks (12). Its features are, Includes: a step (S2) of obtaining degradation information representing the degree of degradation of each of the plurality of fuel cell stacks; The first determination step (S4) is performed if the degradation level of all the fuel cell stacks does not exceed a predetermined degradation level, thus performing the first determination process; and The second determination step (S5) is performed when the degradation level of at least one of the fuel cell stacks exceeds the predetermined degradation level, thus conducting a second determination process. The first determination process involves the computer determining whether any of the fuel cell stacks have a ground fault based on the detection results of the ground fault detection unit when all the fuel cell stacks are connected to the inverter. The second determination process is a process in which the computer determines whether a ground fault exists for each fuel cell stack based on the detection results of the ground fault detection unit when the multiple fuel cell stacks are sequentially connected to the inverter.

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