Water electrolysis system

Abstract

To provide a technology capable of reducing a difference in current flowing through a plurality of water electrolysis stacks, respectively. A water electrolysis system includes a main power supply unit, a plurality of parallel circuits connected in parallel with respect to the main power supply unit, a plurality of water electrolysis stacks provided in the plurality of parallel circuits, respectively, and a sub power supply unit. The sub power supply unit is configured to be electrically provided on a part of the plurality of parallel circuits.

Description

Technical Field

[0001] This specification relates to a water electrolysis system. Background Technology

[0002] Patent Document 1 discloses a water electrolysis system comprising: a power supply unit; multiple parallel circuits connected in parallel with respect to the power supply unit; multiple water electrolysis stacks respectively disposed in the multiple parallel circuits; and a control device.

[0003] Patent Document 1: Japanese Patent Application Publication No. 2023-157554 Summary of the Invention

[0004] When multiple water electrolyzers are connected in parallel with respect to a power unit, the voltages of each water electrolyzer become equal. Furthermore, the IV characteristics of each water electrolyzer vary depending on factors such as the degree of degradation of each electrolyzer. Therefore, when multiple water electrolyzers are connected in parallel with respect to a power unit, the current flowing through each water electrolyzer differs. It is desirable to reduce the difference in current flowing through each of the multiple water electrolyzers.

[0005] This specification provides a technique for reducing the difference in current flowing through multiple water electrolyzers.

[0006] In the first embodiment disclosed in this specification, the water electrolysis system may include: a main power supply unit; multiple parallel circuits connected in parallel with respect to the main power supply unit; multiple water electrolysis stacks respectively disposed in the multiple parallel circuits; and a secondary power supply unit. The secondary power supply unit may be configured to be electrically disposed on a portion of the multiple parallel circuits.

[0007] Based on the aforementioned water electrolysis system, the magnitude of the current flowing through the parallel circuit can be adjusted via the auxiliary power supply unit. Therefore, the difference in current flowing through multiple water electrolysis stacks can be reduced.

[0008] In the second embodiment, in the first embodiment described above, the plurality of water electrolyzers may include a first water electrolyzer with the lowest IV characteristic corresponding to the stack voltage and a second water electrolyzer with the highest IV characteristic corresponding to the stack voltage. The auxiliary power supply unit is electrically connected to a parallel circuit in which the first water electrolyzer is located, and may not be electrically connected to a parallel circuit in which the second water electrolyzer is located.

[0009] According to the above structure, compared to a structure where the auxiliary power supply unit is not electrically connected to the parallel circuit where the first water electrolyzer is located, the current flowing through the first water electrolyzer increases. Consequently, the difference between the current flowing through the first water electrolyzer and the current flowing through the second water electrolyzer decreases. Therefore, it is possible to reduce the difference in current flowing through multiple water electrolyzers.

[0010] In the third embodiment disclosed in this specification, the water electrolysis system may include: a main power supply unit; a plurality of parallel circuits connected in parallel with respect to the main power supply unit; and a plurality of water electrolysis stacks, each disposed in the plurality of parallel circuits, and each of the plurality of water electrolysis stacks having a plurality of units connected in series. Each of the plurality of water electrolysis stacks may be configured to adjust the number of units electrically connected to the parallel circuits in the plurality of units.

[0011] According to the water electrolysis system described above, the magnitude of the current flowing through the parallel circuit can be adjusted by changing the number of units electrically connected to it. Therefore, the difference in current flowing through multiple water electrolysis stacks can be reduced.

[0012] In the fourth embodiment, in the third embodiment described above, each of the plurality of water electrolyzers may further include a first terminal, a second terminal, and a third terminal. All of the plurality of units may be connected in series between the first terminal and the second terminal. A portion of the plurality of units may be connected in series between the first terminal and the third terminal. The remaining portion of the plurality of units may be connected in series between the third terminal and the second terminal. In each of the plurality of parallel circuits, two of the first, second, and third terminals of the water electrolyzers disposed in the parallel circuit may be electrically connected.

[0013] Based on the above structure, if the two terminals electrically connected to the parallel circuit are changed, the magnitude of the current flowing through the water electrolyzer in the parallel circuit will change. Therefore, the magnitude of the current flowing through the water electrolyzer can be easily adjusted.

[0014] In the fifth embodiment, in the fourth embodiment described above, the plurality of water electrolyzers may include a first water electrolyzer having the lowest IV characteristic corresponding to the stack voltage and a second water electrolyzer having the highest IV characteristic corresponding to the stack voltage. The first water electrolyzer may be electrically connected to the parallel circuit using the first terminal and the second terminal. The second water electrolyzer may be electrically connected to the parallel circuit using the second terminal and the third terminal.

[0015] According to the above structure, compared to the structure in which the first and second water electrolyzers are connected to a parallel circuit using terminals 1 and 2 or terminals 2 and 3, the difference between the current flowing through the first and second water electrolyzers can be reduced. Therefore, the difference between the currents flowing through multiple water electrolyzers can be reduced. Attached Figure Description

[0016] Figure 1This is a schematic diagram showing the water electrolysis system 2 in the state where the battery 22 is not electrically connected to the parallel circuits 14A to 14C in the first embodiment.

[0017] Figure 2 This is a schematic diagram showing the water electrolysis system 2 in the state where the battery 22 is electrically connected to the parallel circuit 14A in the first embodiment.

[0018] Figure 3 This is a flowchart of the preparation process performed by the control device 40.

[0019] Figure 4 This is a diagram showing an example of IV characteristics 50A to 50C.

[0020] Figure 5 This is a schematic diagram showing the water electrolysis system 2 in the state where the parallel circuits 14A to 14C are not electrically connected to the intermediate terminal 234 in the second embodiment.

[0021] Figure 6 This is a schematic diagram showing the water electrolysis system 2 in the state where the parallel circuit 14A and the intermediate terminal 234 are electrically connected in the second embodiment. Detailed Implementation

[0022] (First embodiment)

[0023] like Figure 1 As shown, the water electrolysis system 2 includes a power supply unit 10, a rectifier 12, multiple parallel circuits 14A-14C, multiple water electrolysis stacks 16A-16C, multiple current sensors 18A-18C, multiple voltage sensors 20A-20C, a battery 22, and a control device 40. The water electrolysis system 2 is a system for producing hydrogen by electrolyzing water.

[0024] Power supply unit 10 supplies AC power. As an example, power supply unit 10 is a device that converts commercial power or renewable energy into AC power.

[0025] One end of the rectifier 12 is connected to the power supply unit 10. The other end of the rectifier 12 is connected to a plurality of parallel circuits 14A to 14C. The rectifier 12 converts the AC power supplied from the power supply unit 10 into DC power. Furthermore, the rectifier 12 adjusts the power supplied to the plurality of parallel circuits 14A to 14C.

[0026] Multiple parallel circuits 14A to 14C are connected in parallel with respect to rectifier 12.

[0027] Multiple water electrolysis reactors 16A to 16C are respectively arranged in multiple parallel circuits 14A to 14C. Although not shown in the diagram, water is supplied to the multiple water electrolysis reactors 16A to 16C. The multiple water electrolysis reactors 16A to 16C electrolyze the supplied water to produce hydrogen. The water electrolysis reactors 16A to 16C have multiple units C connected in series, a positive terminal 30, and a negative terminal 32. All the multiple units are connected in series between the positive terminal 30 and the negative terminal 32. The positive terminal 30 and the negative terminal 32 of each of the multiple water electrolysis reactors 16A to 16C are electrically connected to the corresponding parallel circuits 14A to 14C.

[0028] Multiple current sensors 18A to 18C are respectively installed in multiple parallel circuits 14A to 14C. Each of the multiple current sensors 18A to 18C detects the current flowing through the multiple parallel circuits 14A to 14C, that is, the current flowing through the multiple water electrolysis stacks 16A to 16C. Furthermore, multiple voltage sensors 20A to 20C are each installed in the multiple parallel circuits 14A to 14C. Each of the multiple voltage sensors 20A to 20C detects the stack voltage of the multiple water electrolysis stacks 16A to 16C. Hereinafter, the current flowing through the water electrolysis stack and the voltage of the water electrolysis stack will sometimes be referred to as "stack current" and "stack voltage," respectively.

[0029] Battery 22 is a rechargeable secondary battery. Battery 22 is configured to be electrically connected in a portion of the parallel circuits 14A to 14C. For example, as shown... Figure 2 As shown, battery 22 can be electrically installed on a portion of the parallel circuits 14A to 14C. In this embodiment, battery 22 is electrically installed on a portion of the parallel circuits so that the difference in current between the multiple stacks of the multiple water electrolysis stacks 16A to 16C is smaller compared to when battery 22 is not installed in any of the multiple parallel circuits 14A to 14C. The parallel circuits in which battery 22 should be installed are determined through a battery installation process described later (see reference). Figure 3 To determine.

[0030] Figure 1 The control device 40 is a computer composed of CPU, ROM, RAM, etc. The control device 40 controls the operation of each component of the water electrolysis system 2.

[0031] (Preparing for processing;) Figure 3 )

[0032] refer to Figure 3 The preparation process performed by the control device 40 will be described. In this embodiment, the preparation process is for determining the parallel circuit to be installed for battery 22. Upon receiving a processing start operation from an operator, the control device 40 performs... Figure 3The processing can be initiated by the operator at specified intervals after the operating time of the water electrolysis system 2. For example, the specified interval is "10,000 hours".

[0033] In S10, the control device 40 sets the reference voltage Vt (reference voltage). Figure 4 ) is applied to each parallel circuit 14A~14C.

[0034] In S12, the control device 40 determines the largest stack current among multiple stack currents as the reference stack current.

[0035] In S20, the control device 40 determines one of the stack currents that is different from the reference stack current as the target stack current among multiple stack currents.

[0036] In S22, the control device 40 determines whether the difference between the reference stack current and the target stack current, i.e., the current difference, is greater than or equal to a predetermined value. The predetermined value is a threshold used to determine whether to electrically connect the battery 22 to the water electrolysis stack corresponding to the target stack current. Furthermore, the predetermined value is information corresponding to the battery 22. If the current difference is greater than or equal to the predetermined value ("Yes" in S22), the control device 40 proceeds to S24. Conversely, if the current difference is not greater than or equal to the predetermined value ("No" in S22), the control device 40 proceeds to S30.

[0037] In S24, the control device 40 determines the water electrolysis stack corresponding to the target stack current, and determines the parallel circuit with the determined water electrolysis stack as the target parallel circuit.

[0038] In S30, the control device 40 determines whether all checks on one or more fuel cell currents that differ from the reference fuel cell current have been completed. Specifically, the control device 40 uses each of the one or more fuel cell currents that differ from the reference fuel cell current to determine whether the processing in S20 has been performed. If the control device 40 has completed the check on one or more fuel cell currents that differ from the reference fuel cell current ("Yes" in S30), it proceeds to S32. On the other hand, if the control device 40 has not completed the check on one or more fuel cell currents that differ from the reference fuel cell current ("No" in S30), it returns to S20.

[0039] In step S32, the control device 40 determines whether the target parallel circuit has been identified. If the target parallel circuit has been identified ("Yes" in S32), the control device 40 proceeds to step S40. On the other hand, if the target parallel circuit has not been identified ("No" in S32), the control device 40 proceeds to step S50.

[0040] In step S40, the control device 40 displays first circuit information, including information indicating the parallel circuit to be connected, on the display unit of the water electrolysis system 2. This allows the operator to know which parallel circuit of battery 22 should be installed. In this case, the operator electrically installs battery 22 into the parallel circuit. If step S40 ends, the control device 40 terminates. Figure 3 The processing.

[0041] Furthermore, in S50, the control device 40 displays second circuit information indicating that the battery 22 does not need to be electrically connected to all parallel circuits 14A-14C on the display unit. Thus, the operator can know that the battery 22 does not need to be electrically connected in any of the parallel circuits 14A-14C. If S50 ends, the control device 40 terminates. Figure 3 The processing.

[0042] (Specific details;) Figure 4 )

[0043] right Figure 4 Each of the multiple IV characteristics 50A to 50C is described in detail for the specific cases of multiple water electrolysis stacks 16A to 16C. In the initial state of this case, battery 22 is not electrically connected to any parallel circuit 14A to 14C.

[0044] First, the control device 40 applies a reference voltage Vt to each of the parallel circuits 14A to 14C (S10). In this case, a stack current IA to IC flows through each of the multiple water electrolysis stacks 16A to 16C. Next, the control device 40 determines the largest stack current IC among the multiple stack currents IA to IC as the reference stack current (S12). In addition, in this case, the current difference between the stack current IC and the stack current IB is less than a specified value, and the current difference between the stack current IC and the stack current IA is greater than or equal to a specified value.

[0045] The control device 40 determines the fuel cell stack current IB as the target fuel cell stack current (S20). Next, the control device 40 determines that the current difference between the reference fuel cell stack current and the target fuel cell stack current is not above a specified value ("No" in S22). Next, the control device 40 determines that the check on the fuel cell stack current IA has not been completed ("No" in S30).

[0046] The control device 40 determines the stack current IA as the target stack current (S20). Next, the control device 40 determines that the current difference between the reference stack current and the target stack current is greater than or equal to a predetermined value ("Yes" in S22). In this case, the control device 40 determines the water electrolysis stack 16A corresponding to the target stack current and determines the parallel circuit 14A, which is equipped with the determined water electrolysis stack 16A, as the target parallel circuit (S24). Next, the control device 40 determines that the check of the stack currents IA and IB has been completed ("Yes" in S30). Furthermore, the control device 40 determines that the target parallel circuit has been determined ("Yes" in S32). In this case, the control device 40 displays first circuit information, including information representing the parallel circuit 14A, on the display unit of the water electrolysis system 2 (S40). Thus, as... Figure 2 As shown, the operator electrically connects battery 22 to the parallel circuit 14A. Additionally, the operator can select a battery with a voltage that ensures the difference between the stack voltage Vp corresponding to the stack current IC in characteristic IV 50A and the reference voltage Vt is zero.

[0047] Then, the operator performs the operation to start the water electrolysis system 2. Since battery 22 is electrically connected to parallel circuit 14A, the stack voltage of water electrolysis stack 16A only increases the voltage of battery 22. Therefore, compared to the case where battery 22 is not electrically connected to parallel circuit 14A, the stack current of water electrolysis stack 16A increases. Consequently, compared to the case where battery 22 is not electrically connected to parallel circuit 14A, the difference between the stack current of water electrolysis stack 16C and the stack current of water electrolysis stack 16A decreases.

[0048] As described above, the water electrolysis system 2 includes: a power supply unit 10 (an example of a "main power supply unit"); a plurality of parallel circuits 14A to 14C connected in parallel with respect to the power supply unit 10; a plurality of water electrolysis stacks 16A to 16C respectively disposed in the plurality of parallel circuits 14A to 14C; and a battery 22 (an example of a "secondary power supply unit"). The battery 22 is configured to be electrically disposed on a portion of the parallel circuits 14A to 14C.

[0049] According to the water electrolysis system 2 described above, the current flowing through the parallel circuits 14A to 14C can be adjusted by the battery 22. Therefore, the difference in current flowing through the multiple water electrolysis stacks 16A to 16C can be reduced.

[0050] Furthermore, in Figure 4In the case of multiple water electrolysis reactors 16A to 16C, there is a water electrolysis reactor 16A (an example of "first water electrolysis reactor") with the lowest IV characteristic of 50A corresponding to the stack voltage, and a water electrolysis reactor 16C (an example of "second water electrolysis reactor") with the highest IV characteristic of 50C corresponding to the stack voltage. Figure 2 As shown, battery 22 is electrically connected to parallel circuit 14A, which is equipped with water electrolysis stack 16A, and is not electrically connected to parallel circuit 14C, which is equipped with water electrolysis stack 16C.

[0051] According to the above structure, the current flowing through water electrolysis reactor 16A increases. Consequently, the difference between the current flowing through water electrolysis reactor 16A and the current flowing through water electrolysis reactor 16C decreases. Therefore, it is possible to reduce the difference in current flowing through the multiple water electrolysis reactors 16A to 16C respectively.

[0052] (Second embodiment)

[0053] refer to Figure 5 , Figure 6 The water electrolysis system 202 of the second embodiment will be described below. Furthermore, in the following description, common structures across the embodiments will be labeled with the same symbols and their descriptions will be omitted.

[0054] like Figure 5 As shown, the water electrolysis system 202 does not have a battery. Furthermore, the water electrolysis stacks 216A to 216C each have multiple units C connected in series, a positive terminal 30, a negative terminal 32, and an intermediate terminal 234. The intermediate terminal 234 is the positive terminal. Alternatively, in a modified example, the intermediate terminal 234 can be the negative terminal. All of the multiple units C are connected in series between the positive terminal 30 and the negative terminal 32. A portion of the multiple units C are connected in series between the positive terminal 30 and the intermediate terminal 234. The remaining portion of the multiple units C is connected in series between the intermediate terminal 234 and the negative terminal 32. In this embodiment, the number of units C connected in series between the positive terminal 30 and the intermediate terminal 234 is less than the number of units C connected in series between the intermediate terminal 234 and the negative terminal 32. In the parallel circuits 14A to 14C, two electrical connections are provided among the positive terminal 30, the negative terminal 32, and the intermediate terminal 234 of the water electrolysis stack in the parallel circuit. Specifically, for example, in the parallel circuits 14A to 14C, the positive terminal 30 and negative terminal 32 of the water electrolyzers 216A to 216C or the intermediate terminal 234 and negative terminal 32 of the water electrolyzers 216A to 216C are electrically connected.

[0055] (Preparing for processing;) Figure 3 )

[0056] The control device 40 in this embodiment also performs... Figure 3Preparation processing. In this embodiment, the preparation processing is for determining the parallel circuit that should utilize the intermediate terminal 234. Figure 3 In the initial state, each of the multiple parallel circuits 14A to 14C is electrically connected to the intermediate terminal 234 and the negative terminal 32 of the water electrolysis stack disposed in the parallel circuit.

[0057] In this embodiment, the first circuit information in S40 is information used to notify the operator that the water electrolyzer should be used at the positive terminal 30. Therefore, the operator who checks the first circuit information electrically connects the target parallel circuit to the positive terminal 30 and the negative terminal 32 of the water electrolyzer corresponding to the target parallel circuit. Furthermore, each of one or more parallel circuits other than the target parallel circuit is electrically connected to the intermediate terminal 234 and the negative terminal 32 of the water electrolyzer provided in that parallel circuit.

[0058] Furthermore, in this embodiment, the second circuit information in S50 indicates that the intermediate terminal 234 should be used for all parallel circuits. Therefore, the operator who checks the second circuit information electrically connects each of the multiple parallel circuits 14A to 14C to the positive terminal 30 and negative terminal 32 of the water electrolysis reactor provided in the parallel circuit. According to this structure, the operating efficiency of the water electrolysis system 2 can be improved compared to the structure in which each of the multiple parallel circuits 14A to 14C is electrically connected to the intermediate terminal 234 and negative terminal 32 of the water electrolysis reactor provided in the parallel circuit.

[0059] (Specific details;) Figure 4 )

[0060] right Figure 4 Each of the multiple IV characteristics 50A to 50C is described in detail for the multiple water electrolyzers 216A to 216C. In the initial state of this case, each of the multiple parallel circuits 14A to 14C is electrically connected to the intermediate terminal 234 and the negative terminal 32 of the water electrolyzer provided in the parallel circuit.

[0061] Similar to the case in the first embodiment, the control device 40 identifies the parallel circuit 14A as the target parallel circuit.

[0062] Then, the control device 40 displays the first circuit information, including information representing the parallel circuit 14A, on the display unit of the water electrolysis system 2 (S40). Thus, as... Figure 6 As shown, the operator electrically connects the parallel circuit 14A to the positive terminal 30 and the negative terminal 32 of the water electrolyzer 216A, and electrically connects the parallel circuits 14B and 14C to the intermediate terminal 234 and the negative terminal 32 of the water electrolyzers 216B and 216C.

[0063] Then, the operator performs the operation to start the water electrolysis system 2. Parallel circuit 14A is electrically connected to the positive terminal 30 and the negative terminal 32, therefore, compared to the structure where parallel circuit 14A is electrically connected to the intermediate terminal 234 and the negative terminal 32, the stack current of water electrolysis stack 216A is larger. Consequently, the difference between the stack current of water electrolysis stack 216C and the stack current of water electrolysis stack 216A becomes smaller.

[0064] As described above, the water electrolysis system 202 includes: a power supply unit 10; a plurality of parallel circuits 14A to 14C connected in parallel with respect to the power supply unit 10; and a plurality of water electrolysis stacks 216A to 216C, each disposed in the plurality of parallel circuits 14A to 14C, and each of the plurality of water electrolysis stacks 216A to 216C having a plurality of units C connected in series. Each of the plurality of water electrolysis stacks 216A to 216C is configured to allow adjustment of the number of units C electrically connected to the parallel circuits 14A to 14C.

[0065] According to the water electrolysis system 202 described above, the magnitude of the current flowing through the parallel circuit can be adjusted by changing the number of units C electrically connected to the parallel circuits 14A to 14C. Therefore, the difference in current flowing through the multiple water electrolysis stacks 216A to 216C can be reduced.

[0066] Furthermore, each of the plurality of water electrolyzers 216A to 216C also includes a positive terminal 30 (an example of a "first terminal"), a negative terminal 32 (an example of a "second terminal"), and an intermediate terminal (an example of a "third terminal"). All of the plurality of units C are connected in series between the positive terminal 30 and the negative terminal 32. A portion of the plurality of units C is connected in series between the positive terminal 30 and the intermediate terminal 234. The remaining portion of the plurality of units C is connected in series between the intermediate terminal 234 and the negative terminal 32. In each of the plurality of parallel circuits 14A to 14C, two electrical connections are provided between the positive terminal 30, the negative terminal 32, and the intermediate terminal 234 of the water electrolyzer in that parallel circuit.

[0067] Based on the above structure, if the two terminals connected to the parallel circuits 14A to 14C are changed, the magnitude of the current flowing through the water electrolyzer in the parallel circuit will change. Therefore, the magnitude of the current flowing through the water electrolyzer can be easily adjusted.

[0068] Furthermore, in Figure 4 , Figure 6In this case, multiple water electrolyzers 216A to 216C include water electrolyzer 216A having the lowest IV characteristic 50A corresponding to the stack current and water electrolyzer 216C having the highest IV characteristic 50C corresponding to the stack current. Water electrolyzer 216A is connected to parallel circuit 14A using positive terminal 30 and negative terminal 32. Water electrolyzer 216C is connected to parallel circuit 14C using negative terminal 32 and intermediate terminal 234.

[0069] According to the above structure, compared to the structure in which water electrolyzers 216A and 216C are connected to a parallel circuit using a positive terminal 30 and a negative terminal 32, or a negative terminal 32 and an intermediate terminal 234, the difference between the current flowing through water electrolyzer 216A and the current flowing through water electrolyzer 216C can be reduced. Therefore, the difference between the currents flowing through multiple water electrolyzers 216A to 216C can be reduced.

[0070] The above provides a detailed description of specific examples of the technology disclosed in this specification. However, these are merely illustrative and do not limit the scope of the claims. The technology described in the claims includes technologies derived from various modifications and alterations of the specific examples illustrated above.

[0071] (First Modification) In the first and second embodiments, the number of parallel circuits, water electrolysis stacks, etc. can be two or more.

[0072] (Second Modification) In the first embodiment, the water electrolysis system 2 may have a switching mechanism for switching between a connected state where the battery 22 is electrically connected to the parallel circuit and a disconnected state where the battery 22 is not electrically connected to the parallel circuit. Although this is an example, the switching mechanism is a relay. In this modification, the control device 40 may... Figure 3 After the preparation process S30, the switching mechanism corresponding to the parallel circuit of the target is switched to the connected state, and the switching mechanism corresponding to the parallel circuit other than the target is switched to the disconnected state. In this variant example, the switching mechanism can be omitted. Figure 3 The S40 and S50.

[0073] (3rd variation) In the first embodiment, the battery 22 may be configured to be electrically connected to two parallel circuits.

[0074] (4th Modification) In the 1st and 2nd embodiments, the following can be omitted. Figure 3 S14 to S30. In this modified example, the control device 40 can determine the parallel circuit of the water electrolyzer other than the water electrolyzer that is equipped with a current corresponding to the reference stack as the target parallel circuit.

[0075] (Fifth variation) In the first embodiment, the water electrolysis system 2 may have multiple batteries.

[0076] (Sixth Modification) In the second embodiment, the water electrolysis system 2 may have a switching mechanism for switching between a first connection state where the parallel circuit is electrically connected to the positive terminal 30 and the negative terminal 32, and a second connection state where the parallel circuit is electrically connected to the intermediate terminal 234 and the negative terminal 32. In this modification, the control device 40 may... Figure 3 After the preparation process S30, the switching mechanism corresponding to the parallel circuit of the target is switched to the first connection state, and the switching mechanism corresponding to the parallel circuit other than the target parallel circuit is switched to the second connection state. In this variant example, the following can be omitted. Figure 3 The S40 and S50.

[0077] (7th variation) In the second embodiment, each water electrolysis stack 216A to 216C may have more than 4 terminals.

[0078] (Eighth Modification) In the second embodiment, the positive terminal 30 and the negative terminal 32 can be configured to change the number of units C connected in series between the positive terminal 30 and the negative terminal 32. In this modification, the intermediate terminal 234 can be omitted.

[0079] (9th variation) In the second embodiment, the operator who sees the second connection information can electrically connect each of the plurality of parallel circuits 14A to 14C to the intermediate terminal 234 and the negative terminal 32 of the water electrolyzer provided in the parallel circuit.

[0080] (10th variation) In the first and second embodiments, the operator can use multiple stack currents relative to a reference voltage to determine the object parallel circuit.

[0081] Furthermore, the technical elements described in this specification or drawings are technically useful individually or in various combinations, and are not limited to the combinations recited in the claims at the time of application. Moreover, the technologies illustrated in this specification or drawings can achieve multiple objectives simultaneously, and each of these objectives is technically useful in itself.

[0082] Symbol Explanation

[0083] 2-Water electrolysis system, 10-Power supply unit, 12-Rectifier, 14A~14C-Parallel circuit, 16A~16C-Water electrolysis reactor, 18A~18C-Current sensor, 20A~20C-Voltage sensor, 22-Battery, 30-Positive terminal, 32-Negative terminal, 40-Control device, 202-Water electrolysis system, 216A~216C-Water electrolysis reactor, 234-Intermediate terminal.

Claims

1. A water electrolysis system, characterized in that, have: Main power supply unit; Multiple parallel circuits are connected in parallel with each other relative to the main power supply unit; Multiple water electrolysis reactors are respectively arranged in the multiple parallel circuits; and Auxiliary power supply unit, The auxiliary power supply unit is configured to be electrically installed on a portion of the parallel circuits among the plurality of parallel circuits.

2. The water electrolysis system according to claim 1, characterized in that, The plurality of water electrolyzers includes a first water electrolyzer with the lowest IV characteristic corresponding to the stack voltage and a second water electrolyzer with the highest IV characteristic corresponding to the stack voltage. The auxiliary power supply unit is electrically connected to the parallel circuit where the first water electrolyzer is located, but is not electrically connected to the parallel circuit where the second water electrolyzer is located.

3. A water electrolysis system, characterized in that, have: Main power supply unit; Multiple parallel circuits are connected in parallel with each other relative to the main power supply unit; and Multiple water electrolyzers are respectively arranged in the multiple parallel circuits, and each of the multiple water electrolyzers has multiple units connected in series. Each of the plurality of water electrolyzers is configured to adjust the number of units electrically connected to the parallel circuit in the plurality of units.

4. The water electrolysis system according to claim 3, characterized in that, Each of the plurality of water electrolysis reactors further comprises a first terminal, a second terminal, and a third terminal. All of the plurality of units are connected in series between the first terminal and the second terminal. A portion of the plurality of units is connected in series between the first terminal and the third terminal. The remaining portion of the plurality of units is connected in series between the third terminal and the second terminal. In each of the plurality of parallel circuits, two electrical connections are provided in the first terminal, the second terminal, and the third terminal of the water electrolysis reactor in the parallel circuit.

5. The water electrolysis system according to claim 4, characterized in that, The plurality of water electrolyzers includes a first water electrolyzer with the lowest IV characteristic corresponding to the stack voltage and a second water electrolyzer with the highest IV characteristic corresponding to the stack voltage. The first water electrolysis reactor is electrically connected to the parallel circuit using the first terminal and the second terminal. The second water electrolysis reactor is electrically connected to the parallel circuit using the second terminal and the third terminal.

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