A hydrogen production system and method for producing hydrogen by electrolysis of water

Abstract

The application discloses a hydrogen production system and method for electrolyzing water, comprising an isolation transformer, a power electronic converter, a main control unit, a first electrolytic cell, a second electrolytic cell, an electrolyte circulating pump, a frequency converter, a hydrogen-liquid separation device, a hydrogen purification device, an electrolyte tank, a heat exchanger, a water supply system, a cooling system, an oxygen-liquid separation device, a first flow sensor, a second flow sensor, a first temperature acquisition module and a second temperature acquisition module. The application also discloses a hydrogen production method for electrolyzing water, which can realize the control of active power and reactive power, and a control method for rapidly heating the electrolytic cell is provided. The application is favorable for reducing the cost of the power electronic converter, reducing the cable cost and cable loss, and can realize the rapid heating and starting of the electrolytic cell through control.

Description

Technical Field

[0001] This application pertains to the field of hydrogen energy, specifically to a water electrolysis hydrogen production system and method. Background Technology

[0002] In existing water electrolysis hydrogen production technologies, the electrolyzer consists of multiple stacked electrolysis cells. The more cells there are, the higher the rated voltage. However, due to limitations in overall weight and manufacturing processes, the number of cells in the electrolyzer is often limited. To achieve higher power levels, the area of ​​the cell electrode plates needs to be increased, which requires a larger current to drive the electrolyzer. Low voltage and high current result in low efficiency of the hydrogen production power supply and high cost of cables or copper busbars.

[0003] The voltage in the small cell of the electrolyzer is higher when it is cold than when it is hot. In order to prevent overvoltage during the cold start-up process of a conventional electrolyzer, the current needs to be gradually increased. The electrolyte can only work normally after it is heated to the optimal temperature. The start-up time is too long and cannot meet the requirements of rapid start-up of large-scale hydrogen production systems. Summary of the Invention

[0004] This application proposes an electrolysis water hydrogen production system and method, which can reduce the amount of cables used, improve system efficiency, and enable rapid start-up of the electrolysis water hydrogen production system.

[0005] To achieve the above objectives, this application provides the following solution:

[0006] An electrolytic water hydrogen production system includes: an isolation transformer, a power electronic converter, a main control unit, a first electrolyzer, a second electrolyzer, an electrolyte circulation pump, a frequency converter, a hydrogen-liquid separation device, a hydrogen purification device, an electrolyte tank, a heat exchanger, a water replenishment system, a cooling system, an oxygen-liquid separation device, a first flow sensor, a second flow sensor, a first temperature acquisition module, and a second temperature acquisition module.

[0007] The isolation transformer is connected to the power electronic converter, and the isolation transformer is used for voltage reduction and isolation.

[0008] The main control unit is used to receive hydrogen production quantity or hydrogen production power commands and to issue control commands to the power electronic converter.

[0009] The first electrolytic cell and the second electrolytic cell are electrically connected in series. The positive terminal of the first electrolytic cell is connected to the positive output terminal of the power electronic converter, and the negative terminal of the first electrolytic cell is connected to the positive terminal of the second electrolytic cell, with this connection point grounded. The negative terminal of the second electrolytic cell is connected to the negative output terminal of the power electronic converter. The liquid inlet, hydrogen mixture outlet, and oxygen mixture outlet of the first electrolytic cell are all located at its negative terminal, and the liquid inlet, hydrogen mixture outlet, and oxygen mixture outlet of the second electrolytic cell are all located at its positive terminal.

[0010] The first electrolytic cell and the second electrolytic cell are connected in parallel in the electrolyte circulation loop. The electrolyte supply pipeline is divided into two branches, one of which supplies electrolyte to the first electrolytic cell and the other branch supplies electrolyte to the second electrolytic cell. The hydrogen mixture outlets of the first electrolytic cell and the second electrolytic cell are combined and connected to the hydrogen-liquid separation device. The oxygen mixture outlets of the first electrolytic cell and the second electrolytic cell are combined and connected to the oxygen-liquid separation device.

[0011] The frequency converter is connected to the electrolyte circulation pump and is used to receive the speed command from the main control unit, control the motor of the electrolyte circulation pump to reach the given speed value, and the frequency converter is used to adjust the flow rate of the electrolyte.

[0012] The electrolyte tank is connected to the heat exchanger, which is used to dissipate heat from the electrolyte; the heat exchanger is also connected to the water replenishment system, and the electrolyte tank is also connected to the cooling system.

[0013] The hydrogen purification device is connected to the hydrogen-liquid separation device;

[0014] The first flow sensor is installed at the electrolyte inlet of the first electrolytic cell and is used to measure the flow rate of the electrolyte in the first electrolytic cell. The second flow sensor is installed at the electrolyte inlet of the second electrolytic cell and is used to measure the flow rate of the electrolyte in the second electrolytic cell.

[0015] The first temperature acquisition module is installed at the outlet of the hydrogen mixture in the first electrolyzer, and the first temperature acquisition module is used to measure the outlet temperature of the electrolyte in the first electrolyzer.

[0016] The second temperature acquisition module is installed at the outlet of the hydrogen mixture in the second electrolyzer, and is used to measure the outlet temperature of the electrolyte in the second electrolyzer.

[0017] Preferably, the power electronic converter has a three-phase AC input and a DC output, and has two modes: output current closed-loop control and output constant voltage current limiting control. It also has a reactive power regulation function on the input side.

[0018] Preferably, the main control unit includes a first communication module, a second communication module, a third communication module, and a signal acquisition module; the first communication module communicates with the upper-level energy management system to receive hydrogen production quantity or hydrogen production power commands; the second communication module communicates with the power electronic converter and provides the output current and voltage limit values ​​of the power electronic converter through communication; the third communication module communicates with the frequency converter; the signal acquisition module acquires the voltage of the first electrolyzer, the voltage of the second electrolyzer, the output current of the power electronic converter, the electrolyte flow rate of the first electrolyzer, the electrolyte flow rate of the second electrolyzer, pressure, and temperature signals.

[0019] Preferably, the power electronic converter includes: an input-side three-phase LC filter, multiple power electronic switches, a control board, a sampling board, and a DC filter capacitor bank.

[0020] Preferably, the control board has a communication unit that communicates with the main control unit, receives control commands, and performs current closed-loop control and voltage closed-loop control.

[0021] Preferably, the sampling board is used to collect input voltage, input current, output voltage, and output current.

[0022] Preferably, the first temperature acquisition module includes a temperature sensor, an electrical isolation circuit, a communication circuit, and a power supply circuit.

[0023] Preferably, the second temperature acquisition module includes a temperature sensor, an electrical isolation circuit, a communication circuit, and a power supply circuit.

[0024] A method for producing hydrogen by water electrolysis, used in a water electrolysis hydrogen production system as described above, includes the following steps:

[0025] Obtain instructions from the upper-level energy management platform, as well as the voltage of the first electrolytic cell, the voltage of the second electrolytic cell, the output current of the power electronic converter, the electrolyte flow rate of the first electrolytic cell, the electrolyte flow rate of the second electrolytic cell, the temperature of the first electrolytic cell, and the temperature of the second electrolytic cell;

[0026] Determine whether the electrolyte in the electrolytic cell has reached the optimal temperature. If it has not reached the optimal temperature, execute rapid temperature rise control.

[0027] Based on the active power or hydrogen production command, the output current setting value of the power electronic converter is given, and the frequency converter is controlled to adjust the electrolyte flow rate so that the flow rate matches the current of the electrolyzer.

[0028] According to the reactive power command, the corresponding reactive power value is issued to the power electronic converter, which then controls the output of the corresponding reactive power.

[0029] Preferably, the rapid temperature rise control includes:

[0030] Temperature judgment: When the temperature of the first electrolytic cell is lower than the optimal operating temperature and the temperature of the second electrolytic cell is lower than the optimal operating temperature, rapid temperature control is initiated.

[0031] Constant voltage and current limiting control: The power electronic converter performs constant voltage and current limiting control. At this time, the output voltage is used as the closed loop to control the output voltage to the rated voltage of the electrolytic cell. When the current does not reach the rated current, the current is not controlled. When the current reaches the rated current, the current is limited to not exceed the rated current by control.

[0032] Electrolyte flow rate limitation control: Given the inverter speed command, reduce the speed of the electrolyte circulation pump and control the flow rate to k times the normal flow rate, where k < 1, and k is a variable value that increases with the increase of temperature. When the temperature reaches the optimal operating temperature point, k = 1.

[0033] The beneficial effects of this application are as follows:

[0034] 1) Compared with conventional water electrolysis hydrogen production schemes, the electrolyzers are connected in series, which reduces the current by half and the amount of cables or copper busbars used by half at the same power.

[0035] 2) The electrolyte circulation loop is connected in parallel, and the two electrolyzers share a set of electrolyte circulation system, hydrogen-liquid separation device, oxygen-liquid separation device, hydrogen purification device and other equipment, which reduces the initial investment;

[0036] 3) During the startup process, the electrolyte flow rate is reduced by control, and the power electronic converter adopts constant voltage and current limiting control to realize the rapid startup of the electrolytic cell from a cold state;

[0037] 4) Real-time monitoring of the voltage and current of the first and second electrolytic cells can provide early warnings when aging or malfunctions occur in the electrolytic cells. Attached Figure Description

[0038] To more clearly illustrate the technical solutions of this application, the drawings used in the embodiments are briefly introduced below. Obviously, the drawings described below are only some embodiments of this application. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0039] Figure 1 This is a schematic diagram of a water electrolysis hydrogen production system according to Embodiment 1 of this application;

[0040] Figure 2 This is a schematic diagram of a water electrolysis hydrogen production method according to Embodiment 2 of this application;

[0041] Figure 3 This is a schematic diagram of another method for producing hydrogen by electrolysis of water, as described in Embodiment 3 of this application.

[0042] Explanation of reference numerals in the attached figures

[0043] 1. Isolation transformer; 2. Power electronic converter; 3. Main control unit; 4. First electrolyzer; 5. Second electrolyzer; 6. Electrolyte circulation pump; 7. Frequency converter; 8. Hydrogen-liquid separation device; 9. Hydrogen purification device; 10. Hydrogen buffer tank; 11. Electrolyte tank; 12. Heat exchanger; 13. Water replenishment system; 14. Cooling system; 15. Oxygen-liquid separation device; 16. Current sensor; 17. First voltage sensor; 18. Second voltage sensor; 19. First flow sensor; 20. Second flow sensor; 21. First temperature acquisition module; 22. Second temperature acquisition module. Detailed Implementation

[0044] The technical solutions of the embodiments of this application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of this application, and not all embodiments. Based on the embodiments of this application, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this application.

[0045] To make the above-mentioned objectives, features and advantages of this application more apparent and understandable, the application will be further described in detail below with reference to the accompanying drawings and specific embodiments.

[0046] Example 1

[0047] like Figure 1 The diagram shown is a schematic of an electrolytic water production system provided in this application. The electrolytic water production system includes: an isolation transformer 1, a power electronic converter 2, a main control unit 3, a first electrolytic cell 4, a second electrolytic cell 5, an electrolyte circulation pump 6, a frequency converter 7, a hydrogen-liquid separation device 8, a hydrogen purification device 9, a hydrogen buffer tank 10, an electrolyte tank 11, a heat exchanger 12, a water replenishment system 13, a cooling system 14, an oxygen-liquid separation device 15, a current sensor 16, a first voltage sensor 17, a second voltage sensor 18, a first flow sensor 19, a second flow sensor 20, a first temperature acquisition module 21, and a second temperature acquisition module 22.

[0048] Isolation transformer 1 steps down the input voltage from 35kV or 10kV to 500V. 900V, its function is to reduce voltage and isolate. To avoid circulating current, the low-voltage side of isolation transformer 1 is not grounded.

[0049] The power electronic converter 2 takes three-phase AC power as input and DC power as output. It has two modes: output current closed-loop control and output constant voltage current limiting control. It also has reactive power regulation function on the input side.

[0050] The first electrolytic cell 4 and the second electrolytic cell 5 are electrically connected in series, which improves the voltage level of the system. The rated voltage after series connection can exceed 1000V. The positive terminal of the first electrolytic cell 4 is connected to the positive output terminal of the power electronic converter 2, and the negative terminal of the first electrolytic cell 4 is connected to the positive terminal of the second electrolytic cell 5. This connection point is grounded. The negative terminal of the second electrolytic cell 5 is connected to the negative output terminal of the power electronic converter 2.

[0051] The inlet, outlet of hydrogen mixture, and outlet of oxygen mixture of the first electrolytic cell 4 are all located at the negative electrode, while the inlet, outlet of hydrogen mixture, and outlet of oxygen mixture of the second electrolytic cell 5 are all located at the positive electrode. During operation, the negative electrode of the first electrolytic cell 4 and the positive electrode of the second electrolytic cell 5 are at the same potential as the ground, thus avoiding the risk of electric shock caused by the potential of the electrolyte circulation system to the ground.

[0052] The first electrolytic cell 4 and the second electrolytic cell 5 are connected in parallel in the electrolyte circulation loop. The electrolyte supply pipeline is divided into two branches, one of which supplies electrolyte to the first electrolytic cell 4 and the other branch supplies electrolyte to the second electrolytic cell 5. Each branch is equipped with a flow sensor to measure the electrolyte flow rate. The hydrogen mixture outlets of the first electrolytic cell 4 and the second electrolytic cell 5 are combined and connected to the hydrogen-liquid separator 8. The oxygen mixture outlets of the first electrolytic cell 4 and the second electrolytic cell 5 are combined and connected to the oxygen-liquid separator 15.

[0053] The current sensor 16 is connected in series with the output cable or copper busbar of the power electronic converter 2 to measure the output current.

[0054] The first voltage sensor 17 is connected in parallel with the first electrolytic cell 4 and is used to measure the voltage of the first electrolytic cell 4; the second voltage sensor 18 is connected in parallel with the second electrolytic cell 5 and is used to measure the voltage of the second electrolytic cell 5.

[0055] The first flow sensor 19 is installed at the electrolyte inlet of the first electrolytic cell 4 to measure the flow rate of the electrolyte in the first electrolytic cell 4. The second flow sensor 20 is installed at the electrolyte inlet of the second electrolytic cell 5 to measure the flow rate of the electrolyte in the second electrolytic cell 5.

[0056] The main control unit 3 includes a first communication module, a second communication module, a third communication module, and a signal acquisition module. The first communication module communicates with the upper-level energy management system and receives hydrogen production quantity or hydrogen production power commands. The second communication module communicates with the power electronic converter 2 and provides the output current and voltage limit values ​​of the power electronic converter through communication. The third communication module communicates with the frequency converter 7. The signal acquisition module acquires the voltage of the first electrolyzer 4, the voltage of the second electrolyzer 5, the output current of the power electronic converter 2, the electrolyte flow rate of the first electrolyzer 4, the electrolyte flow rate of the second electrolyzer 5, pressure, and temperature signals.

[0057] The power electronic converter 2 includes: an input-side three-phase LC filter, multiple power electronic switches, a control board, a sampling board, and a DC filter capacitor bank. The control board has a communication unit that communicates with the main control unit, receives control commands, performs current closed-loop control, and can limit the maximum output voltage. The sampling board is used to collect input voltage, input current, output voltage, and output current. The power electronic converter 2 uses a three-level topology, and the power electronic switches are IGBTs.

[0058] The first temperature acquisition module 21 includes a temperature sensor, an electrical isolation circuit, a communication circuit, and a power supply circuit. The first temperature acquisition module 21 is installed at the outlet of the hydrogen mixture in the first electrolytic cell and is used to measure the outlet temperature of the electrolyte in the first electrolytic cell 4. The second temperature acquisition module 22 includes a temperature sensor, an electrical isolation circuit, a communication circuit, and a power supply circuit. The second temperature acquisition module is installed at the outlet of the hydrogen mixture in the second electrolytic cell and is used to measure the outlet temperature of the electrolyte in the second electrolytic cell 5.

[0059] The output of the frequency converter 7 is connected to the motor of the electrolyte circulation pump 6. The frequency converter 7 receives the speed command from the main control unit 3 and controls the motor of the electrolyte circulation pump 6 to reach the given speed value. The purpose is to adjust the flow rate of the electrolyte.

[0060] The gas separated by the hydrogen-liquid separator 8 enters the hydrogen purification unit 9, and the separated liquid flows into the electrolyte tank 11. The liquid separated by the oxygen-liquid separator 15 flows into the electrolyte tank 11. The electrolyte tank 11 stores the prepared electrolyte and also has a water inlet connected to the water replenishment system 13.

[0061] The hydrogen purification device 9 is connected to the hydrogen-liquid separation device 8. The main function of the hydrogen purification device 9 is to further dehydrate and remove oxygen from the hydrogen. The purified hydrogen enters the hydrogen buffer tank 10.

[0062] The main function of the heat exchanger 12 is to dissipate heat from the electrolyte and transfer the heat to the cooling system 14.

[0063] Example 2

[0064] like Figure 2 The image shows a method for producing hydrogen by water electrolysis provided in this application, comprising the following steps:

[0065] Execute commands to obtain information from the upper-level energy management platform: start / stop commands, active power or hydrogen production commands, reactive power commands; and the voltage of the first electrolyzer, the voltage of the second electrolyzer, the output current of the power electronic converter, the electrolyte flow rate of the first electrolyzer, the electrolyte flow rate of the second electrolyzer, the temperature of the first electrolyzer, and the temperature of the second electrolyzer.

[0066] Determine whether the electrolyte in the electrolytic cell has reached the optimal temperature. If it has not reached the optimal temperature, execute rapid temperature rise control.

[0067] 1) Temperature judgment: When the temperature of the first electrolytic cell is lower than the optimal operating temperature and the temperature of the second electrolytic cell is lower than the optimal operating temperature, rapid temperature control is initiated.

[0068] 2) Constant voltage and current limiting control: The power electronic converter performs constant voltage and current limiting control. At this time, the output voltage is used as the closed loop, and the output voltage is controlled to be the rated voltage of the electrolytic cell. At this time, the current is not controlled, but the current must be limited to not exceed the rated current.

[0069] 3) Electrolyte flow limit: Given the inverter speed command, reduce the speed of the electrolyte circulation pump and control the flow rate to k times the normal flow rate, where k < 1. k is a variable value that increases with the temperature. When the temperature reaches the nearest operating temperature point, k = 1.

[0070] Based on the active power or hydrogen production command, the output current setting value of the power electronic converter is given, and the frequency converter is controlled to adjust the electrolyte flow rate so that the flow rate matches the current of the electrolyzer.

[0071] According to the reactive power command, the corresponding reactive power value is issued to the power electronic converter, and the power electronic converter controls the output of the corresponding reactive power.

[0072] Fault detection and protection: The system determines whether the system status is normal based on the collected signals. If the system status is abnormal, the system will execute a shutdown protection.

[0073] Fault detection and protection include: voltage imbalance detection and protection between the first and second electrolytic cells, overvoltage protection for the first and second electrolytic cells, overcurrent detection and protection, undercurrent detection and protection, hydrogen leakage detection and protection, temperature imbalance detection and protection, and electrolyte flow imbalance detection and protection. Voltage imbalance detection and protection between the first and second electrolytic cells is triggered when the absolute value of the voltage difference between the first and second voltage sensors exceeds a preset protection limit, automatically executing a shutdown operation. Temperature imbalance detection and protection is triggered when the absolute value of the temperature difference between the first and second temperature acquisition modules exceeds a preset protection limit, automatically executing a shutdown operation. Electrolyte flow imbalance detection and protection is triggered when the absolute value of the difference between the flow rate detected by the first and second flow sensors exceeds a preset protection limit, automatically executing a shutdown operation.

[0074] Example 3

[0075] like Figure 3 As shown, the double-split transformer 1 reduces the high voltage (35kV or 10kV) to a low voltage. Its output has two sets of windings, which are respectively connected to the first power electronic converter 2 and the second power electronic converter 322. The first power electronic converter 2 and the second power electronic converter 322 respectively control a set of electrolytic cells connected in series.

[0076] In this embodiment, the electrolyte circulation loops of the first electrolytic cell 4, the second electrolytic cell 5, the third electrolytic cell 324, and the fourth electrolytic cell 325 are connected in parallel and share a set of auxiliary equipment system 31. The auxiliary equipment system 31 includes: frequency converter 7, electrolyte circulation pump 6, heat exchanger 12, electrolyte tank 11, water replenishment system 13, hydrogen-liquid separation device 8, hydrogen purification device 9, hydrogen buffer tank 10, oxygen-liquid separation device 15, and cooling system 14.

[0077] The first power electronic converter 2 and the second power electronic converter 322 share a main control unit 3. The main control unit 3 receives instructions from the upper-level energy management system and issues control instructions to the two power electronic converters respectively.

[0078] In this embodiment, the first power electronic converter 2 and the second power electronic converter 322 can be started independently to control the operation of the connected electrolytic cell.

[0079] Although this application has been described in conjunction with some embodiments, it is not intended to be limited to the specific forms set forth herein. Rather, the scope of this application is limited only by the appended claims. Additionally, although individual features may be included in different claims, these may be advantageously combined, and inclusion in different claims does not imply that such a combination of features is not feasible and / or advantageous. The order of features in the claims does not imply that the features must be in any particular order of their operation. Furthermore, in the claims, the word "comprising" does not exclude other elements, and the terms "a" or "an" do not exclude a plurality. Reference numerals in the claims are provided only by way of explicit example and should not be construed as limiting the scope of the claims in any way.

[0080] The embodiments described above are merely preferred embodiments of this application and are not intended to limit the scope of this application. Any modifications and improvements made to the technical solutions of this application by those skilled in the art without departing from the spirit of this application shall fall within the protection scope defined by the claims of this application.

Claims

1. A water electrolysis hydrogen production system, characterized in that, include: Isolation transformer, power electronic converter, main control unit, first electrolytic cell, second electrolytic cell, electrolyte circulation pump, frequency converter, hydrogen-liquid separation device, hydrogen purification device, electrolyte tank, heat exchanger, water replenishment system, cooling system, oxygen-liquid separation device, first flow sensor, second flow sensor, first temperature acquisition module, second temperature acquisition module; The isolation transformer is connected to the power electronic converter, and the isolation transformer is used for voltage reduction and isolation. The main control unit is used to receive hydrogen production quantity or hydrogen production power commands and to issue control commands to the power electronic converter. The first electrolytic cell and the second electrolytic cell are electrically connected in series. The positive terminal of the first electrolytic cell is connected to the positive output terminal of the power electronic converter, and the negative terminal of the first electrolytic cell is connected to the positive terminal of the second electrolytic cell. This connection point is grounded. The negative terminal of the second electrolytic cell is connected to the negative output terminal of the power electronic converter. The first electrolytic cell and the second electrolytic cell are connected in parallel in the electrolyte circulation loop. The electrolyte supply pipeline is divided into two branches, one of which supplies electrolyte to the first electrolytic cell and the other branch supplies electrolyte to the second electrolytic cell. The hydrogen mixture outlets of the first electrolytic cell and the second electrolytic cell are combined and connected to the hydrogen-liquid separation device. The oxygen mixture outlets of the first electrolytic cell and the second electrolytic cell are combined and connected to the oxygen-liquid separation device. The frequency converter is connected to the electrolyte circulation pump and is used to receive the speed command from the main control unit, control the motor of the electrolyte circulation pump to reach the given speed value, and the frequency converter is used to adjust the flow rate of the electrolyte. The first flow sensor is installed at the electrolyte inlet of the first electrolytic cell and is used to measure the flow rate of the electrolyte in the first electrolytic cell. The second flow sensor is installed at the electrolyte inlet of the second electrolytic cell and is used to measure the flow rate of the electrolyte in the second electrolytic cell. The power electronic converter has a three-phase AC input and a DC output. It has two modes: output current closed-loop control and output constant voltage current limiting control. It also has a reactive power regulation function on the input side. The constant voltage and current limiting control method includes: the power electronic converter performs constant voltage and current limiting control. At this time, the output voltage is used as a closed loop, and the output voltage is controlled to be the rated voltage of the electrolytic cell. When the current does not reach the rated current, the current is not controlled. When the current reaches the rated current, the current is limited to not exceed the rated current by control.

2. The water electrolysis hydrogen production system according to claim 1, characterized in that, The inlet, outlet of hydrogen mixture, and outlet of oxygen mixture of the first electrolytic cell are all located at its negative electrode, while the inlet, outlet of hydrogen mixture, and outlet of oxygen mixture of the second electrolytic cell are all located at its positive electrode. The electrolyte tank is connected to the heat exchanger, which is used to dissipate heat from the electrolyte; the heat exchanger is also connected to the water replenishment system, and the electrolyte tank is also connected to the cooling system. The hydrogen purification device is connected to the hydrogen-liquid separation device; The first temperature acquisition module is installed at the outlet of the hydrogen mixture in the first electrolyzer, and the first temperature acquisition module is used to measure the outlet temperature of the electrolyte in the first electrolyzer. The second temperature acquisition module is installed at the outlet of the hydrogen mixture in the second electrolyzer, and is used to measure the outlet temperature of the electrolyte in the second electrolyzer.

3. The water electrolysis hydrogen production system according to claim 1, characterized in that, The main control unit includes a first communication module, a second communication module, a third communication module, and a signal acquisition module; the first communication module communicates with the upper-level energy management system to receive hydrogen production quantity or hydrogen production power commands; the second communication module communicates with the power electronic converter and provides the output current and voltage limit values ​​of the power electronic converter through communication; the third communication module communicates with the frequency converter. The signal acquisition module acquires the voltage of the first electrolytic cell, the voltage of the second electrolytic cell, the output current of the power electronic converter, the electrolyte flow rate of the first electrolytic cell, the electrolyte flow rate of the second electrolytic cell, pressure, and temperature signals.

4. The water electrolysis hydrogen production system according to claim 1, characterized in that, The power electronic converter includes: an input-side three-phase LC filter, multiple power electronic switches, a control board, a sampling board, and a DC filter capacitor bank.

5. The water electrolysis hydrogen production system according to claim 4, characterized in that, The control board has a communication unit that communicates with the main control unit, receives control commands, and performs current closed-loop control and voltage closed-loop control.

6. The water electrolysis hydrogen production system according to claim 4, characterized in that, The sampling board is used to collect input voltage, input current, output voltage, and output current.

7. The water electrolysis hydrogen production system according to claim 1, characterized in that, The first temperature acquisition module includes a temperature sensor, an electrical isolation circuit, a communication circuit, and a power supply circuit.

8. The water electrolysis hydrogen production system according to claim 1, characterized in that, The second temperature acquisition module includes a temperature sensor, an electrical isolation circuit, a communication circuit, and a power supply circuit.

9. A method for producing hydrogen by water electrolysis, used in the hydrogen production operation of the water electrolysis system according to any one of claims 1-8, characterized in that, Includes the following steps: Obtain instructions from the upper-level energy management platform, as well as the voltage of the first electrolytic cell, the voltage of the second electrolytic cell, the output current of the power electronic converter, the electrolyte flow rate of the first electrolytic cell, the electrolyte flow rate of the second electrolytic cell, the temperature of the first electrolytic cell, and the temperature of the second electrolytic cell; Determine whether the electrolyte in the electrolytic cell has reached the optimal temperature. If it has not reached the optimal temperature, execute rapid temperature rise control. Based on the active power or hydrogen production command, the output current setting value of the power electronic converter is given, and the frequency converter is controlled to adjust the electrolyte flow rate so that the flow rate matches the current of the electrolyzer. According to the reactive power command, the corresponding reactive power value is issued to the power electronic converter, which then controls the output of the corresponding reactive power.

10. A method for producing hydrogen by electrolysis of water according to claim 9, characterized in that, The rapid temperature rise control includes: Temperature judgment: When the temperature of the first electrolytic cell is lower than the optimal operating temperature and the temperature of the second electrolytic cell is lower than the optimal operating temperature, rapid temperature control is initiated. Electrolyte flow rate limitation control: Given the inverter speed command, reduce the speed of the electrolyte circulation pump and control the flow rate to k times the normal flow rate, where k < 1, and k is a variable value that increases with the increase of temperature. When the temperature reaches the optimal operating temperature point, k = 1.

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