Hydrogen production power supply system and control method thereof

Abstract

The invention provides a hydrogen production power supply system and a control method thereof, and the system comprises an AC transformation device which is configured to carry out the transformation of a first AC voltage inputted by an AC power grid, and then distributes and outputs a second AC voltage; the voltage regulating branch is configured to convert and regulate the second alternating current voltage to obtain second direct current voltage; the constant-voltage branch is configured to convert the second alternating-current voltage into first direct-current voltage; the switching device is configured to connect the output end of the voltage regulating branch with the output end of the constant voltage branch in series to form total output voltage and output the total output voltage to the electrolytic bath; the energy storage device is configured to access the total output voltage and is connected with the electrolytic bath in parallel; the switching device is further configured to adjust the number of the connected voltage regulating branches and / or constant voltage branches according to the working voltage of the electrolytic cell. By means of the scheme, the hydrogen production power supply system can input the corresponding number of constant-voltage branches and voltage-regulating branches according to the load condition of the electrolytic cell, and the operation efficiency of the hydrogen production power supply is improved.

Description

Technical Field

[0001] The present application relates to the technical field of hydrogen production, and in particular to a hydrogen production power supply system and a control method thereof. Background Art

[0002] Hydrogen energy is a clean, carbon-free, flexible, efficient, and richly applicable secondary energy and an important industrial raw material. Using new energy sources for power supply, water electrolysis to produce hydrogen is a relatively convenient method for producing hydrogen. It is green, environmentally friendly, flexible in production, and high in purity. It is an ideal green hydrogen production method. As the core equipment connecting the electrolyzer and the new energy grid, the control performance and reliability of the hydrogen power supply will directly affect the efficiency and safety of the entire hydrogen production system.

[0003] At the same time, with the continuous improvement of the process and technology level of electrolyzer manufacturers, the hydrogen production of alkaline electrolyzers has gradually increased from 1000Nm 3 / h increased to 3000Nm 3 / h、5000Nm 3 / h, the DC voltage and current specifications of the electrolyzer are constantly increasing, and the output voltage and current levels of the hydrogen production power supply compatible with the electrolyzer also need to be improved accordingly.

[0004] In the relevant technology, the technical solution for hydrogen production power supply will adopt three forms: thyristor rectification, diode rectification + insulated gate bipolar transistor (IGBT) chopping, and full IGBT rectification + chopping. Among them, thyristor rectification is a one-level topology structure, and the other two are two-level topologies. When the thyristor solution is used for rectification and power supply, in addition to injecting a large amount of low-order harmonics into the AC power grid and absorbing a large amount of reactive power, its output DC voltage regulation speed is slow and contains a large amount of current ripple, which affects the efficiency of hydrogen production by the electrolyzer and is not suitable for application in the field of green electricity hydrogen production. When a two-stage topology circuit is used for rectification and power supply, multiple branches are usually required to be connected in parallel to meet the current and voltage requirements of the electrolyzer. The two-stage topology circuit has two energy change links: AC to DC (AC-DC) and fixed DC voltage converted into variable DC voltage (DC-DC). Multiple branches are powered at the same time, which affects the overall efficiency of the hydrogen production power supply, especially under conditions where the hydrogen production of the electrolyzer is low.

[0005] In view of this, in order to promote the popularization and application of large-capacity electrolyzers in the field of green hydrogen, it is urgent to study new hydrogen production power supply topology solutions to meet the needs of green electricity hydrogen production systems for hydrogen production power supplies with high response speed, high efficiency, high power factor, wide output voltage and current range and excellent grid-related characteristics. Summary of the invention

[0006] The embodiments of the present application provide a hydrogen production power supply system and a control method thereof to solve the problem in the related art that multiple branches are used to supply power to meet the use requirements of the electrolyzer, which affects the overall efficiency of the hydrogen production power supply.

[0007] To solve the above problems, the technical solutions provided by this application are as follows: In a first aspect, the present application provides a hydrogen production power supply system, comprising: An AC transformer, configured to transform a first AC voltage input from an AC power grid and distribute the transformed voltage to output a second AC voltage; A voltage regulating branch, electrically connected to the AC transformer, the voltage regulating branch being configured to convert and adjust the second AC voltage to obtain a second DC voltage; a constant voltage branch, electrically connected to the AC transformer, the constant voltage branch being configured to convert the second AC voltage into a first DC voltage; A switching device configured to connect the output end of the voltage regulating branch and the output end of the constant voltage branch in series to form a total output voltage to be output to the electrolytic cell; and an energy storage device configured to be connected to the total output voltage and connected in parallel with the electrolyzer; Wherein, the switching device is also configured to adjust the number of the connected voltage regulating branches and / or constant voltage branches according to the working voltage of the electrolytic cell.

[0008] In one embodiment, the hydrogen production power supply system includes one voltage regulating branch or two voltage regulating branches, and the voltage regulating branch includes: a first AC-DC converter configured to convert the second AC voltage into an initial DC voltage; and A DC transformer is electrically connected to the first AC-DC converter, and the DC transformer is configured to adjust the initial DC voltage to obtain the second DC voltage.

[0009] In one embodiment, the DC transformer comprises: a chopper circuit configured to access and regulate the initial DC voltage; and a discharge circuit, electrically connected to the chopper circuit, the discharge circuit being configured to release electrical energy of the chopper circuit; Wherein, the discharge circuit includes an insulated gate bipolar transistor and a power resistor connected in series.

[0010] In one embodiment, the hydrogen production power supply system includes a plurality of constant voltage branches, and the constant voltage branches include: The second AC / DC converter is configured to convert the second AC voltage into a first DC voltage.

[0011] In one embodiment, the switching device includes a plurality of switching circuits, the plurality of switching circuits are connected in series with the electrolytic cell, and each of the voltage regulating branches and each of the constant voltage branches is connected with a switching circuit; The switching circuit comprises a positive input terminal, a negative input terminal, a positive output terminal and a negative output terminal; In adjacent switching circuits, the negative output terminal of one switching circuit is connected to the positive output terminal of another switching circuit.

[0012] In one embodiment, the switching circuit is a mechanical switching circuit; or The switching circuit is an electronic switching circuit that realizes switching by controlling the on and off of an insulated gate bipolar transistor.

[0013] In one embodiment, the switching circuit further includes: a bypass switch connected between the positive input terminal and the positive output terminal of the switching circuit, and / or connected between the negative input terminal and the negative output terminal of the switching circuit; and A bipolar switch, wherein a first end of the bipolar switch is connected between a positive output end and a negative output end of the switching circuit.

[0014] In one embodiment, the bypass switch and the bipolar switch have different switch states.

[0015] In one embodiment, the first DC voltage and the second DC voltage satisfy: Udc1=Udc2=Udc / (N+1), Udc≥Ups: Among them, Udc1 is the constant value of the first DC voltage, Udc2 is the maximum value of the second DC voltage, Udc is the maximum value of the total output voltage, N is the number of the constant voltage branches, and Ups is the working voltage of the electrolytic cell.

[0016] In a second aspect, the present application provides a control method for a hydrogen production power supply system, which is implemented by the hydrogen production power supply system of any embodiment of the first aspect, including: Boost control: increasing the total output voltage of the hydrogen production power supply system from 0 to the working voltage of the electrolyzer; Voltage reduction control: reducing the total output voltage of the hydrogen production power system from the operating voltage of the electrolyzer to 0; and Voltage regulation control: adjust the output voltage of the hydrogen production power supply from the initial operating voltage of the electrolyzer to the target operating voltage.

[0017] In one embodiment, the voltage regulating branch includes a first voltage regulating branch and a second voltage regulating branch.

[0018] In one embodiment, the step of boost control includes: All the voltage regulating branches and the constant voltage branches are in the withdrawn state; When Ups ≤ Udc2: Unlock the first AC-DC converter and the DC transformer of the first voltage regulating branch or the second voltage regulating branch. The voltage regulating branch in the unlocked state is put into operation, and the voltage across the electrolytic cell is gradually increased from 0 to Ups. When Ups > Udc2 and Ups ≤ 2Udc2: Unlock the first AC-DC converter and the DC transformer of the first voltage regulating branch and the second voltage regulating branch respectively. The output voltages of the first voltage regulating branch and the second voltage regulating branch are 0. Then unlock one of the constant voltage branches, and the output voltage is Udc2. Then put the first voltage regulating branch into operation, and gradually increase the voltage across the electrolytic cell from 0 to Udc2. Then withdraw the first voltage regulating branch, put one of the constant voltage branches and the second voltage regulating branch in the unlocked state into operation. One of the constant voltage branches in the unlocked state outputs a constant voltage Udc2, and the second voltage regulating branch gradually increases its output voltage from 0 to Ups - Udc2, and increases the voltage across the electrolytic cell from Udc2 to Ups. Block the chopper circuit in the DC transformer of the first voltage regulating branch, and reduce the output voltage of the first voltage regulating branch to 0 through the discharge circuit. When Ups > m * Udc2 and Ups ≤ (m + 1) * Udc2 (1 < m ≤ N, m is an integer), in accordance with the method of putting the constant voltage branches into operation and the method of switching and putting the voltage regulating branches into and out of operation when Ups > Udc2 and Ups ≤ 2Udc2, put all the constant voltage branches into operation and one of the voltage regulating branches into operation in sequence, and gradually increase the voltage across the electrolytic cell from 0 to Ups.

[0019] In one embodiment, the step-down control is to reduce the output voltage of the hydrogen production power supply from the voltage Ups corresponding to the current working condition of the electrolytic cell to 0. The steps of the step-down control include: When Ups ≤ Udc2: Assume that the first voltage regulating branch is in the unlocked and put-in state, and adjust the output voltage of the first voltage regulating branch to gradually reduce the voltage across the electrolytic cell from Ups to 0. When Ups > Udc2 and Ups ≤ 2Udc2, assume that the second voltage regulating branch and one of the constant voltage branches are in the unlocked and put-in state; First, unlock the first voltage regulating branch and output a voltage Udc2; Second, reduce the output voltage of the second voltage regulating branch from Ups - Udc2 to 0, and reduce the voltage across the electrolytic cell from Ups to Udc2; Then withdraw one of the constant voltage branches and the second voltage regulating branch in the unlocked and put-in state, and put the first voltage regulating branch into operation; Then adjust the output voltage of the first voltage regulating branch to reduce the voltage across the electrolytic cell from Udc2 to 0. When Ups > m * Udc2 and Ups ≤ (m + 1) * Udc2 (1 < m ≤ N, m is an integer), in accordance with the method of withdrawing the constant voltage branch and the method of switching, putting into operation and withdrawing the voltage regulating branch as described when Ups > Udc2 and Ups ≤ 2Udc2, withdraw the constant voltage branches m to 1 in sequence and put into operation one of the voltage regulating branches, and gradually reduce the voltage at both ends of the electrolytic cell from Ups to 0.

[0020] In one embodiment, the steps of the voltage regulation control include: Assume that the number of the constant voltage branches put into operation when the hydrogen production power supply outputs the current voltage Ups1 is y, y = floor(Ups1 / Udc2), and determine that the number of the constant voltage branches required to be put into operation when the hydrogen production power supply outputs the target voltage Ups2 is z, z = floor(Ups2 / Udc2), where floor is the floor function operator; When z = y, adjust the output voltage of the voltage regulating branch that is currently in the unlocked state, and adjust the voltage at both ends of the electrolytic cell from Ups1 to Ups2; When z > y, in accordance with the method of putting into operation the constant voltage branches and the method of switching, putting into operation, withdrawing and adjusting the voltage regulating branch in the boost control, gradually increase the number of the constant voltage branches put into operation from y to z, and adjust the output voltage of the voltage regulating branch that is in the unlocked state to raise the voltage at both ends of the electrolytic cell to Ups2; When z < y, in accordance with the method of withdrawing the constant voltage branches and the method of switching, putting into operation, withdrawing and adjusting the voltage regulating branch in the buck control, gradually reduce the number of the constant voltage branches put into operation from y to z, and adjust the output voltage of the voltage regulating branch that is in the unlocked state to reduce the voltage at both ends of the electrolytic cell to Ups2.

[0021] An embodiment of the present application provides a hydrogen production power supply system and a control method thereof, wherein the hydrogen production power supply system includes an AC transformer, configured to distribute and output a second AC voltage after transforming a first AC voltage input from an AC power grid; a constant voltage branch, electrically connected to the AC transformer, wherein the constant voltage branch is configured to convert the second AC voltage to obtain a first DC voltage; a voltage regulating branch, electrically connected to the AC transformer, wherein the voltage regulating branch is configured to convert and adjust the second AC voltage to obtain a second DC voltage; a switching device, configured to connect in series the output end of the voltage regulating branch and the output end of the constant voltage branch to form a total output voltage to be output to an electrolyzer; and an energy storage device, configured to be connected to the total output voltage and connected in parallel to the electrolyzer; wherein the switching device is further configured to adjust the number of the connected voltage regulating branches and / or constant voltage branches according to the working voltage of the electrolyzer. Through the above scheme, the present application divides the output power capacity of the hydrogen production power supply equally according to the resistance load characteristics of the electrolyzer, and invests different numbers of power branches according to the operating conditions of the electrolyzer, thereby improving the operating efficiency of the hydrogen production power supply and helping to meet the demand for large-capacity electrolyzer hydrogen production power supplies in the field of green electricity hydrogen production. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] In order to more clearly illustrate the technical solutions in the embodiments of the present application, the drawings required for use in the description of the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present application. For those skilled in the art, other drawings can be obtained based on these drawings without creative work.

[0023] Attached Figure 1 This is a schematic diagram of an optional hydrogen production power source in an embodiment of the present application; Attached Figure 2 This is a schematic diagram of another optional hydrogen production power source in the embodiment of the present application; Attached Figure 3 is a schematic diagram of a two-level three-phase bridge circuit of an AC-DC converter in an embodiment of the present application; Attached Figure 4 is a schematic diagram of a three-level three-phase bridge circuit of an AC-DC converter in an embodiment of the present application; Attached Figure 5 This is a circuit schematic diagram of a DC transformer based on a two-level three-phase AC side parallel chopper circuit in an embodiment of the present application; Attached Figure 6 Schematic diagram of a circuit of a DC transformer based on a three-phase bridge diode rectifier chopper circuit in an embodiment of the present application; Attached Figure 7 1 is a circuit schematic diagram of a DC transformer based on a dual active bridge resonant chopper circuit in an embodiment of the present application; Attached Figure 8Schematic diagram of the circuit structure of the constant voltage branch in the embodiment of the present application; Attached Fig. 9 Schematic diagram of the circuit structure of the voltage regulating branch in the embodiment of the present application; Attached Fig.10 It is a schematic diagram of a single two-level electronic switching circuit in an embodiment of the present application; Attached Fig.11 A schematic diagram of a plurality of two-level electronic switching circuits connected in parallel in an embodiment of the present application; Attached Fig.12 It is a schematic diagram of a single three-level electronic switching circuit in an embodiment of the present application; Attached Fig.13 A schematic diagram of a plurality of three-level electronic switching circuits connected in parallel in an embodiment of the present application; Attached Fig.14 A connection diagram of a two-level AC / DC converter and a switching circuit in an embodiment of the present application; Attached Fig.15 A connection diagram of a three-level AC / DC converter and a switching circuit in an embodiment of the present application; Attached Fig.16 A diagram showing the connection relationship between the voltage regulating branch and the switching circuit in the embodiment of the present application; Attached Fig.17 This is a circuit schematic diagram of multiple modules of AC / DC converters connected in parallel in an embodiment of the present application; Attached Fig.18 This is a circuit schematic diagram of multiple modules of DC transformers connected in parallel in an embodiment of the present application.

[0024] Description of reference numerals in the figures: 1. Hydrogen production power system; 100. AC transformer; 200, constant voltage branch; 210, second AC / DC converter; 300, voltage regulating branch; 310, first AC / DC converter; 320, DC transformer; 321, chopper circuit; 322, discharge circuit; 400, switching device; 410, switching circuit; 411, bypass switch; 412, bipolar switch; 500. Energy storage device. DETAILED DESCRIPTION

[0025] The technical solutions in the embodiments of the present application will be described clearly and completely below in conjunction with the drawings in the embodiments of the present application. Obviously, the described embodiments are only part of the embodiments of the present application, rather than all of the embodiments. Based on the embodiments in the present application, all other embodiments obtained by those skilled in the art without creative work are within the scope of protection of the present application.

[0026] The terms "include" and "comprising" used in the specification and claims of the present application indicate the presence of described features, integers, steps, operations, elements and / or components, but do not exclude the presence or addition of one or more other features, integers, steps, operations, elements, components and / or collections thereof.

[0027] Reference Figure 1 and Figure 2 As shown, according to the first aspect of the present application, a hydrogen production power supply system 1 is provided, which can be applicable to a large-capacity electrolyzer. The hydrogen production power supply system 1 includes an AC transformer 100, a voltage regulating branch 300, a constant voltage branch 200, a switching device 400 and an energy storage device 500.

[0028] Among them, the AC transformer 100 is configured to transform the first AC voltage input from the AC power grid and distribute it to output a second AC voltage. In some specific examples, the AC transformer 100 uses a multi-winding transformer, the primary winding of the multi-winding transformer is connected to the AC power grid, and each group of secondary windings is respectively connected to a voltage regulating branch 300 or a constant voltage branch 200.

[0029] The voltage regulating branch 300 is electrically connected to the AC transformer 100, and the voltage regulating branch 300 is configured to convert and adjust the second AC voltage to obtain a second DC voltage. Specifically, the voltage regulating branch 300 includes a first AC-DC converter 310 and a DC transformer 320. The first AC-DC converter 310 is configured to convert the second AC voltage into an initial DC voltage; the DC transformer 320 is electrically connected to the first AC-DC converter 310, and the DC transformer 320 is configured to adjust the initial DC voltage to obtain a second DC voltage. In addition to converting AC current into DC power with a constant voltage, the first AC-DC converter 310 can also perform reactive power compensation and harmonic suppression on the AC power grid, and the DC transformer 320 can convert the initial DC voltage with a constant voltage output from the first AC voltage conversion into a second DC voltage with a variable voltage amplitude. Refer to Figure 3 or Figure 4 As shown, in some embodiments of the present application, the circuit of the first AC-DC converter 310 is a two-level three-phase bridge circuit or a three-level three-phase bridge circuit based on insulated gate bipolar transistor pulse width modulation (Insulated Gate Bipolar Transistor Pulse-Width Modulation, insulated gate bipolar transistor PWM) rectification.

[0030] Reference Figures 5 to 7As shown, in some embodiments of the present application, the DC transformer 320 includes a chopper circuit 321 and a discharge circuit 322, wherein the chopper circuit 321 is configured to access and adjust the initial DC voltage, the discharge circuit 322 is electrically connected to the chopper circuit 321, and the discharge circuit 322 is configured to release the electric energy of the chopper circuit 321, and the discharge circuit 322 includes an insulated gate bipolar transistor and a power resistor connected in series. Figure 5 As shown, the chopper branch can be a DC-DC converter based on multi-phase bridge arms interleaved in parallel, or it can be a reference Figure 6 The three-phase bridge diode rectifier DC-DC converter shown in Figure 7 In the dual active bridge resonant DC-DC converters shown, in these DC-DC converters, the positive electrode of the output end of the chopper circuit 321 is connected to the positive electrode of the discharge circuit 322, and the negative electrode is connected to the negative electrode of the discharge circuit 322.

[0031] The discharge circuit 322 is composed of an insulated gate bipolar transistor and a power resistor in series, the collector of the insulated gate bipolar transistor is connected to the positive electrode of the discharge circuit 322, the emitter of the insulated gate bipolar transistor is connected to one end of the power resistor, and the other end of the power resistor is connected to the negative electrode of the discharge circuit 322. It should be noted that the insulated gate bipolar transistor acts as a switch in the discharge circuit 322. When it is detected that the voltage at the output end of the chopper circuit 321 is too high or the electric energy needs to be released quickly, the control system will trigger the insulated gate bipolar transistor to turn on. Once the insulated gate bipolar transistor is turned on, the circuit forms a low impedance path so that the current can flow through the power resistor. The power resistor consumes excess electric energy by converting the current into heat energy, thereby reducing the voltage and current in the circuit. Moreover, this process of consuming excess electric energy is fast and controllable, which can ensure that the system responds quickly to overvoltage or overcurrent conditions.

[0032] The constant voltage branch 200 is electrically connected to the AC transformer 100, and the constant voltage branch 200 is configured to convert the second AC voltage to obtain a first DC voltage. It should be noted that in the hydrogen production power supply system 1 of the present application, a plurality of constant voltage branches 200 are provided, and the constant voltage branch 200 includes a second AC-DC converter 210, which is configured to convert the second AC voltage into a first DC voltage. Among them, since the output ends of the voltage regulating branch 300 and the constant voltage branch 200 are connected in series to power the electrolyzer, the current flowing through the output ends of the two are equal, so the voltage regulating branch 300 and the constant voltage branch 200 have the same active output capacity. Therefore, the second AC-DC converter 210 and the first AC-DC converter 310 can have the same circuit structure and effect, and this application will not be repeated here.

[0033] The switching device 400 is configured to connect the output end of the voltage regulating branch and the output end of the constant voltage branch in series to form a total output voltage to be output to the electrolytic cell. The switching device 400 includes a plurality of switching circuits 410, which are connected in series with the electrolytic cell, and each voltage regulating branch 300 and each constant voltage branch 200 are connected to a switching circuit 410.

[0034] Specifically, the switching circuit 410 includes a positive input terminal, a negative input terminal, a positive output terminal and a negative output terminal. In adjacent switching circuits 410, the negative output terminal of one switching circuit 410 is connected to the positive output terminal of another switching circuit 410. Figure 8 As shown, the positive and negative electrodes of the DC input terminal of the switching circuit 410 are respectively connected to the positive and negative electrodes of the DC output terminal of the second AC-DC converter 210, Fig. 9 As shown, the positive and negative DC output terminals of the first AC-DC converter 310 of the voltage regulating branch 300 are respectively connected to the positive and negative DC input terminals of the DC transformer 320, and the positive and negative DC output terminals of the DC transformer 320 are respectively connected to the positive and negative DC input terminals of the switching circuit 410.

[0035] In some embodiments of the present application, the switching circuit 410 is a mechanical switching circuit 410, or the switching circuit 410 is an electronic switching circuit 410 that realizes switching by controlling the on and off of an insulated gate bipolar transistor.

[0036] In some embodiments of the present application, the switching circuit 410 further includes a bypass switch 411 and a bipolar switch 412, wherein the bypass switch 411 is connected between the positive input terminal and the positive output terminal of the switching circuit, and / or between the negative input terminal and the negative output terminal of the switching circuit, and the first end of the bipolar switch 412 is connected between the positive output terminal and the negative output terminal of the switching circuit. Among them, the bypass switch 411 is used to connect the constant voltage branch or the voltage regulating branch to the series circuit connected to the electrolytic cell, and the bipolar switch 412 is used to withdraw the constant voltage branch or the voltage regulating branch from the series circuit connected to the electrolytic cell. It should be noted that although the switching circuit 410 is divided into several switches in the embodiment of the present application, in actual application, it can be a general mechanical switch or an electronic switch composed of multiple IGBTs connected in series and parallel.

[0037] In addition, the switching device 400 is also configured to adjust the number of connected voltage regulating branches and / or constant voltage branches according to the working voltage of the electrolytic cell. According to this function of the switching circuit 410, the bypass switch 411 and the bipolar switch 412 need to have different switching states.

[0038] In some embodiments of the present application, the bypass switch 411 and the bipolar switch 412 are mechanical switches. Specifically, the bypass switch 411 includes a first switch and a second switch, and the bipolar switch 412 includes a third switch. The first switch is connected between the positive input terminal and the positive output terminal of the switching circuit 410, and the second switch is connected between the negative input terminal and the negative output terminal of the switching circuit 410. The first end of the third switch is connected to the connection line between the first switch and the positive output terminal of the switching circuit, and the second end of the third switch is connected to the connection line between the second switch and the negative output terminal of the switching circuit. In this embodiment, it is necessary to make the first switch and the second switch have the same switch state, and the first switch and the third switch have different switch states. The first switch and the second switch are disconnected, the third switch is closed, and the voltage regulating branch 300 or the constant voltage branch 200 is connected to the external circuit; when the mechanical switching circuit 410 exits, the first switch and the second switch are closed, the third switch is disconnected, and the voltage regulating branch 300 or the constant voltage branch 200 is disconnected from the external circuit.

[0039] In some embodiments of the present application, when the switching circuit 410 is an electronic switching circuit 410, the bipolar connection function and the branch bypass function are realized by controlling the on and off of the IGBT.

[0040] Reference Fig.10 As shown, in some embodiments of the present application, a two-level electronic switching circuit 410 is provided. When the relevant branch is switched on, the upper tube Q1 of the IGBT is turned on and the lower tube Q2 is blocked; when the relevant branch is switched off, the upper tube Q1 of the IGBT is blocked and the lower tube Q2 is turned on. In this embodiment, the Q1 tube is the bypass switch 411, and the Q2 tube is the bipolar switch 412. On this basis, referring to Fig.11 As shown, when the branch output current is large, multiple IGBTs can be directly connected in parallel to improve the current carrying capacity of the switching circuit 410.

[0041] Reference Fig.12 As shown, in some embodiments of the present application, a three-level electronic switching circuit 410 is also provided. When the relevant branch is put into operation, Q1 and Q4 are turned on, and Q2 and Q3 are locked; when the relevant branch is withdrawn, Q1 and Q4 are locked, and Q2 and Q3 are turned on. In this embodiment, Q1 and Q4 are bypass switches 411, and Q2 and Q3 are bipolar switches 412. On this basis, referring to Fig.13 As shown, when the branch output current is large, multiple three-level bridge arms can be directly connected in parallel to improve the current-carrying capacity of the switching circuit 410.

[0042] In some embodiments of the present application, reference Fig.14 As shown, when the second AC-DC converter 210 in the constant voltage circuit is a two-level three-phase bridge circuit, it can be connected to the two-level electronic switching circuit 410; Fig.15 As shown, when the second AC-DC converter 210 in the constant voltage circuit is a three-level three-phase bridge circuit, it can be connected to the three-level electronic switching circuit 410 .

[0043] Accordingly, refer to Fig.16 As shown, in the voltage regulation circuit, when the DC transformer 320 includes a two-level three-phase bridge arm interleaved parallel chopper circuit 321 , it can be connected to a two-level electronic switching circuit 410 .

[0044] In addition, in some embodiments of the present application, the first AC-DC converter 310 or the second AC-DC converter 210 may include one or more modules connected in parallel with the same PWM rectifier current circuit for the AC side and the DC side. Fig.17 As shown, when a single PWM rectifier module cannot meet the power demand of the branch, multiple PWM rectifier modules can be connected in parallel on the AC side and the DC side to improve the power transmission capacity of the branch.

[0045] Similarly, in some embodiments of the present application, the DC transformer 320 in the voltage regulation circuit may also include one or more module input sides and output sides respectively connected in parallel and using the same chopper circuit 321. When the DC transformer 320 of the voltage regulation branch 300 needs to increase the transmission power, multiple chopper circuits 321 and the input side and output side of the discharge circuit 322 may be connected in parallel. The specific circuit structure is as follows: Fig.18 shown.

[0046] The energy storage device 500 is configured to be connected to the total output voltage and connected in parallel with the electrolyzer. In some specific examples, the energy storage device 500 is a support capacitor, the positive electrode of the support capacitor is connected to the positive electrode of the electrolyzer, and the negative electrode of the support capacitor is connected to the negative electrode of the electrolyzer. By setting the support capacitor as an instantaneous energy storage device, the impact of power mutation on the system can be buffered, the hydrogen production process can be avoided from being interrupted, and the stability of hydrogen production efficiency can be ensured.

[0047] It should be noted that, in the aforementioned embodiment, the total output voltage uout of the hydrogen production power supply ranges from 0 to Udc, the output voltage of the constant voltage branch 200 is constant at Udc1, the output voltage range of the voltage regulating branch 300 is 0 to Udc2, and the output voltages of the voltage regulating branch 300 and the constant voltage branch 200 satisfy the following relationship: Udc1=Udc2=Udc / (N+1); the maximum voltage Udc output by the hydrogen production power supply is greater than or equal to the working voltage Ups required by the electrolyzer.

[0048] In summary, the present application provides the following two specific embodiments: Example 1 Reference Figure 1As shown, the hydrogen production power supply system 1 includes two voltage regulating branches 300 and N constant voltage branches 200. The AC input end of each branch is connected to a set of secondary windings of a multi-winding isolation transformer, and the positive and negative electrodes of the DC output ends of adjacent branches are connected in series with the positive and negative electrodes of the support capacitor, and the positive and negative electrodes of the support capacitor are connected to the positive and negative terminals of the electrolyzer. When the output voltage of the hydrogen production power supply changes, the first voltage regulating branch and the second voltage regulating branch are alternately put in and out to achieve continuous adjustment of the output voltage.

[0049] In this embodiment, the specific structures of the voltage regulating branch 300, the constant voltage branch 200 and the switching circuit 410 can adopt the circuit combination that can be implemented in the above embodiments, and the present application does not limit it here.

[0050] Example 2 Reference Figure 2 As shown, the hydrogen production power supply includes 1 voltage regulating branch 300 and N constant voltage branches 200, the AC input end of each branch is connected to a set of secondary windings of a multi-winding isolation transformer, and the positive and negative poles of the DC output ends of adjacent branches are connected in series with the positive and negative poles of the support capacitor, and the positive and negative poles of the support capacitor are connected to the positive and negative terminals of the electrolyzer. When the output voltage of the hydrogen production power supply decreases, if the output voltage of the voltage regulating branch 300 reaches 0V, the voltage regulating branch 300 is withdrawn first, and the output voltage of the voltage regulating branch 300 is adjusted to Udc2, and then the voltage regulating branch 300 is put into operation and the number of constant voltage branches 200 put into operation is reduced by 1; when the output voltage of the hydrogen production power supply increases, if the voltage of the voltage regulating branch 300 reaches Udc2, the voltage regulating branch 300 is withdrawn and the number of constant voltage branches 200 put into operation is increased by 1, and the output voltage of the voltage regulating branch 300 is reduced to 0V before being put into operation.

[0051] In this embodiment, the specific structures of the voltage regulating branch 300, the constant voltage branch 200 and the switching circuit 410 may also adopt the circuit combination that can be implemented in the aforementioned embodiments, and the present application does not limit this.

[0052] In a second aspect, the present application also provides a control method for a hydrogen production power supply system 1, including voltage boost control, voltage drop control and voltage regulation control.

[0053] Taking Example 1 as an example, the boost control is to raise the DC voltage output by the hydrogen production power supply from 0 to the voltage Ups required by the target working condition of the electrolyzer. The steps of the boost control include: 1) All voltage regulating branches 300 and constant pressure branches 200 are in the exit state; 2) When Ups≤Udc2: unlock the first AC / DC converter 310 and the DC transformer 320 of the first voltage regulating branch or the second voltage regulating branch. At this time, the output voltage of the first voltage regulating branch or the second voltage regulating branch is 0; the voltage regulating branch 300 in the unlocked state is put into operation to gradually raise the voltage at both ends of the electrolytic cell from 0 to Ups; 3) When \(U_{ps}>U_{dc2}\) and \(U_{ps}\leq2U_{dc2}\): First, unlock the first AC-DC converter 310 and the DC transformer 320 of the first voltage regulating branch and the second voltage regulating branch respectively. At this time, the output voltage of the voltage regulating branch 300 is 0. Secondly, unlock the required constant voltage branch 200. It should be noted that the number of unlocked constant voltage branches 200 can be one, and it can be the first constant voltage branch adjacent to the voltage regulating branch. This constant voltage branch 200 is denoted as the first constant voltage branch, and the subsequent connected constant voltage branches 200 are denoted as the second to the Nth constant voltage branches in sequence. At this time, the output voltage of the first constant voltage branch is \(U_{dc2}\). Then, put the first voltage regulating branch into operation, and gradually raise the voltage at both ends of the electrolytic cell from 0 to \(U_{dc2}\). Next, withdraw the first voltage regulating branch, put the first constant voltage branch and the second voltage regulating branch into operation. The first constant voltage branch outputs a constant voltage \(U_{dc2}\), and the second voltage regulating branch gradually raises its output voltage from 0 to \(U_{ps}-U_{dc2}\), and raises the voltage at both ends of the electrolytic cell from \(U_{dc2}\) to \(U_{ps}\). In addition, lock the chopper circuit 321 in the DC transformer 320 of the first voltage regulating branch, and reduce the output voltage of the first voltage regulating branch to 0 through the discharge circuit 322. 4) When \(U_{ps}>mU_{dc2}\) and \(U_{ps}\leq(m + 1)U_{dc2}\) (\(1<m\leq N\), \(m\) is an integer), according to the input method of the constant voltage branch 200 and the switching and input / output methods of the voltage regulating branch when \(U_{ps}>U_{dc2}\) and \(U_{ps}\leq2U_{dc2}\), input the 1st to the mth constant voltage branches 200 and one voltage regulating branch in sequence, and gradually raise the voltage at both ends of the electrolytic cell from 0 to \(U_{ps}\).

[0054] Taking Embodiment 1 as an example, the step-down control is to reduce the output voltage of the hydrogen production power supply from the voltage \(U_{ps}\) corresponding to the current working condition of the electrolytic cell to 0. The steps of the step-down control include: 1) When \(U_{ps}\leq U_{dc2}\): Assume that the first voltage regulating branch is in the unlocked and input state, and adjust the output voltage of the first voltage regulating branch to gradually reduce the voltage at both ends of the electrolytic cell from \(U_{ps}\) to 0. 2) When \(U_{ps}>U_{dc2}\) and \(U_{ps}\leq2U_{dc2}\), assume that the second voltage regulating branch and the first constant voltage branch are in the unlocked and input state; First, unlock the first voltage regulating branch and output the voltage \(U_{dc2}\); Secondly, reduce the output voltage of the second voltage regulating branch from \(U_{ps}-U_{dc2}\) to 0, and reduce the voltage at both ends of the electrolytic cell from \(U_{ps}\) to \(U_{dc2}\); Then, withdraw the first constant voltage branch and the second voltage regulating branch, and input the first voltage regulating branch; Next, adjust the output voltage of the first voltage regulating branch to reduce the voltage at both ends of the electrolytic cell from \(U_{dc2}\) to 0; It should be noted that the constant voltage branch in the unlocked and input state can be the first constant voltage branch or any other constant voltage branch 200.

[0055] 3) When Ups > m * Udc2 and Ups ≤ (m + 1) * Udc2 (1 < m ≤ N, m is an integer), in accordance with the disconnection method of the constant voltage branch 200 and the switching, connection, and disconnection methods of the voltage regulation branch when Ups > Udc2 and Ups ≤ 2Udc2, disconnect the (m - 1)th to 1st constant voltage branches 200 in sequence and connect one voltage regulation branch, gradually reducing the voltage across the electrolytic cell from Ups to 0.

[0056] Taking Embodiment 1 as an example, the voltage regulation control is to adjust the output voltage of the hydrogen production power supply from the voltage Ups1 corresponding to the current operating condition of the electrolytic cell to the voltage Ups2 corresponding to the target operating condition. The steps of the voltage regulation control include: 1) Assume that the number of constant voltage branches 200 connected when the hydrogen production power supply outputs the current voltage Ups1 is y, y = floor(Ups1 / Udc2), and determine that the number of constant voltage branches 200 required to be connected when the hydrogen production power supply outputs the target voltage Ups2 is z, z = floor(Ups2 / Udc2), where floor is the floor function operator; 2) When z = y, adjust the output voltage of the voltage regulation branch 300 that is currently in the unlocked state, and adjust the voltage across the electrolytic cell from Ups1 to Ups2; 3) When z > y, in accordance with the connection method of the constant voltage branch 200 and the switching, connection, disconnection, and adjustment methods of the voltage regulation branch 300 in the boost control, gradually increase the number of connected constant voltage branches 200 from y to z, and adjust the output voltage of the voltage regulation branch 300 that is in the unlocked state to raise the voltage across the electrolytic cell to Ups2; 4) When z < y, in accordance with the disconnection method of the constant voltage branch 200 and the switching, connection, disconnection, and adjustment methods of the voltage regulation branch in the buck control, gradually reduce the number of connected constant voltage branches 200 from y to z, and adjust the output voltage of the voltage regulation branch 300 that is in the unlocked state to reduce the voltage across the electrolytic cell to Ups2.

[0057] In the related technology, the hydrogen production power supply technology solution will adopt three forms: thyristor rectification, diode rectification + insulated gate bipolar transistor (IGBT) chopping, and full IGBT rectification + chopping. Among them, thyristor rectification is a one-level topology structure, and the other two are two-level topologies. When the thyristor solution is used for rectification and power supply, since the thyristor rectifier is a nonlinear load and adjusts the output voltage by controlling the conduction angle, this control method will cause the current waveform to deviate from the sinusoidal waveform and generate harmonics. And because the thyristor starts to conduct after the voltage passes through zero, the current lags behind the voltage, and this phase difference will cause the absorption of reactive power. In addition to injecting a large amount of low-order harmonics into the AC power grid and absorbing a large amount of reactive power, its output DC voltage has a slow adjustment speed and contains a large amount of current ripple, which affects the efficiency of hydrogen production in the electrolyzer and is not suitable for application in the field of green electricity hydrogen production. When a two-stage topology circuit is used for rectification and power supply, multiple branches are usually required to supply power in parallel to meet the current and voltage requirements of the electrolyzer. The two-stage topology circuit has two energy change links: AC-DC conversion and fixed DC voltage conversion into variable DC voltage (DC-DC). Multiple branches supply power at the same time, which affects the overall efficiency of the hydrogen production power supply. However, the present application divides the output power capacity of the hydrogen production power supply equally according to the resistance load characteristics of the electrolyzer, and invests different numbers of power branches according to the operating conditions of the electrolyzer, thereby improving the operating efficiency of the hydrogen production power supply. At the same time, the present application connects the voltage regulating branch 300 based on the two-stage topology circuit with a voltage regulating function in series with the output end of the constant voltage branch 200 based on the primary topology circuit that outputs a constant voltage, thereby providing a large-capacity electrolyzer with a hydrogen production power supply solution with fast response speed, excellent grid-related characteristics, and high overall efficiency, meeting the demand for large-capacity electrolyzer hydrogen production power supply in the field of green electricity hydrogen production.

[0058] In summary, although the present application has been disclosed as above with preferred embodiments, the above preferred embodiments are not intended to limit the present application. Ordinary technicians in this field can make various changes and modifications without departing from the spirit and scope of the present application. Therefore, the scope of protection of the present application shall be based on the scope defined in the claims.

Claims

1. A hydrogen production power supply system, characterized in that: include: An AC transformer, configured to transform a first AC voltage input from an AC power grid and distribute the transformed voltage to output a second AC voltage; a constant voltage branch, electrically connected to the AC transformer, the constant voltage branch being configured to convert the second AC voltage into a first DC voltage; A voltage regulating branch, electrically connected to the AC transformer, the voltage regulating branch being configured to convert and adjust the second AC voltage to obtain a second DC voltage; A switching device is configured to connect the output end of the voltage regulating branch and the output end of the constant voltage branch in series to form a total output voltage to be output to the electrolytic cell; as well as an energy storage device configured to be connected to the total output voltage and connected in parallel with the electrolyzer; Wherein, the switching device is also configured to adjust the number of the connected voltage regulating branches and / or constant voltage branches according to the working voltage of the electrolytic cell.

2. The hydrogen production power supply system according to claim 1, characterized in that: The hydrogen production power supply system includes one voltage regulating branch or two voltage regulating branches, and the voltage regulating branch includes: a first AC-DC converter configured to convert the second AC voltage into an initial DC voltage; and A DC transformer is electrically connected to the first AC-DC converter, and the DC transformer is configured to adjust the initial DC voltage to obtain the second DC voltage.

3. The hydrogen production power supply system according to claim 2, characterized in that: The DC transformer comprises: a chopper circuit configured to access and regulate the initial DC voltage; and a discharge circuit, electrically connected to the chopper circuit, the discharge circuit being configured to release electrical energy of the chopper circuit; Wherein, the discharge circuit includes an insulated gate bipolar transistor and a power resistor connected in series.

4. The hydrogen production power supply system according to claim 2, characterized in that: The hydrogen production power supply system comprises a plurality of constant voltage branches, and the constant voltage branches comprise: The second AC / DC converter is configured to convert the second AC voltage into a first DC voltage.

5. The hydrogen production power supply system according to claim 4, characterized in that: The switching device comprises a plurality of switching circuits, the plurality of switching circuits are connected in series with the electrolytic cell, and each of the voltage regulating branches and each of the constant voltage branches is connected with a switching circuit; The switching circuit comprises a positive input terminal, a negative input terminal, a positive output terminal and a negative output terminal; In adjacent switching circuits, the negative output terminal of one switching circuit is connected to the positive output terminal of another switching circuit.

6. The hydrogen production power supply system according to claim 5, characterized in that: The switching circuit is a mechanical switching circuit; or The switching circuit is an electronic switching circuit that realizes switching by controlling the on and off of an insulated gate bipolar transistor.

7. The hydrogen production power supply system according to claim 6, characterized in that: The switching circuit also includes: a bypass switch connected between the positive input terminal and the positive output terminal of the switching circuit, and / or connected between the negative input terminal and the negative output terminal of the switching circuit; and A bipolar switch, wherein a first end of the bipolar switch is connected between a positive output end and a negative output end of the switching circuit.

8. The hydrogen production power supply system according to claim 7, wherein the bypass switch and the bipolar switch have different switch states.

9. The hydrogen production power supply system according to claim 1, wherein the first DC voltage and the second DC voltage satisfy: Udc1 = Udc2 = Udc / (N + 1), Udc ≥ Ups: wherein, Udc1 is the constant value of the first DC voltage, Udc2 is the maximum value of the second DC voltage, Udc is the maximum value of the total output voltage, N is the number of constant voltage branches, and Ups is the working voltage of the electrolyzer.

10. A control method for a hydrogen production power supply system, implemented based on the hydrogen production power supply system of any one of claims 1 to 9, characterized in that: It includes: Boost control: raising the total output voltage of the hydrogen production power supply system from 0 to the working voltage of the electrolyzer; Buck control: lowering the total output voltage of the hydrogen production power supply system from the working voltage of the electrolyzer to 0; and Voltage regulation control: regulating the output voltage of the hydrogen production power supply from the initial working condition voltage of the electrolyzer to the target working condition voltage.

11. The control method according to claim 10, characterized in that: The voltage regulation branch includes a first voltage regulation branch and a second voltage regulation branch.

12. The control method according to claim 11, characterized in that: The steps of the boost control include: All the voltage regulation branches and the constant voltage branches are in the withdrawn state; When Ups ≤ Udc2: unlocking the first AC-DC converter and the DC transformer of the first voltage regulation branch or the second voltage regulation branch, putting the voltage regulation branch in the unlocked state into operation, and gradually raising the voltage across the electrolyzer from 0 to Ups; When Ups > Udc2 and Ups ≤ 2Udc2: unlocking the first AC-DC converter and the DC transformer of the first voltage regulation branch and the second voltage regulation branch respectively, the output voltages of the first voltage regulation branch and the second voltage regulation branch are 0; then unlocking one of the constant voltage branches, the output voltage is Udc2; then putting the first voltage regulation branch into operation, gradually raising the voltage across the electrolyzer from 0 to Udc2; then withdrawing the first voltage regulation branch, putting one of the constant voltage branches in the unlocked state and the second voltage regulation branch into operation, one of the constant voltage branches in the unlocked state outputs a constant voltage Udc2, and the second voltage regulation branch gradually raises the output voltage from 0 to Ups - Udc2, raising the voltage across the electrolyzer from Udc2 to Ups; locking the chopper circuit in the DC transformer of the first voltage regulation branch, and reducing the output voltage of the first voltage regulation branch to 0 through the discharge circuit; When Ups > m*Udc2 and Ups ≤ (m + 1)*Udc2 (1 < m ≤ N, m is an integer), according to the method of putting the constant voltage branches into operation and the method of switching and putting in and out the voltage regulation branches when Ups > Udc2 and Ups ≤ 2Udc2, put all the constant voltage branches into operation and one of the voltage regulation branches into operation in sequence, and gradually raise the voltage across the electrolyzer from 0 to Ups.

13. The control method according to claim 12, characterized in that: The buck control is to lower the output voltage of the hydrogen production power supply from the voltage Ups corresponding to the current working condition of the electrolyzer to 0, and the steps of the buck control include: When \(U_{ps}\leq U_{dc2}\): Assume that the first voltage regulating branch is unlocked and put into operation, and regulate the output voltage of the first voltage regulating branch to gradually reduce the voltage across the electrolyzer from \(U_{ps}\) to 0; When \(U_{ps}>U_{dc2}\) and \(U_{ps}\leq 2U_{dc2}\), assume that the second voltage regulating branch and one of the constant voltage branches are unlocked and put into operation; First, unlock the first voltage regulating branch and output voltage \(U_{dc2}\); Second, reduce the output voltage of the second voltage regulating branch from \(U_{ps}-U_{dc2}\) to 0, and reduce the voltage across the electrolyzer from \(U_{ps}\) to \(U_{dc2}\); Then, withdraw the one constant voltage branch and the second voltage regulating branch that are in the unlocked and put-into-operation state, and put the first voltage regulating branch into operation; Next, regulate the output voltage of the first voltage regulating branch to reduce the voltage across the electrolyzer from \(U_{dc2}\) to 0; When \(U_{ps}>mU_{dc2}\) and \(U_{ps}\leq(m + 1)U_{dc2}\) (\(1 < m\leq N\), \(m\) is an integer), in accordance with the method of withdrawing the constant voltage branches and the method of switching, putting into and withdrawing the voltage regulating branches when \(U_{ps}>U_{dc2}\) and \(U_{ps}\leq 2U_{dc2}\), gradually withdraw \(m\) constant voltage branches and put one voltage regulating branch into operation in sequence, and gradually reduce the voltage across the electrolyzer from \(U_{ps}\) to 0.

14. The control method according to claim 13, characterized in that: The steps of the voltage regulation control include: Assume that the number of constant voltage branches put into operation when the hydrogen production power supply outputs the current voltage \(U_{ps1}\) is \(y\), \(y = \lfloor U_{ps1} / U_{dc2}\rfloor\), and determine that the number of constant voltage branches required to be put into operation when the hydrogen production power supply outputs the target voltage \(U_{ps2}\) is \(z\), \(z=\lfloor U_{ps2} / U_{dc2}\rfloor\), where \(\lfloor\ \rfloor\) is the floor operator; When \(z = y\), regulate the output voltage of the voltage regulating branch that is currently in the unlocked state to regulate the voltage across the electrolyzer from \(U_{ps1}\) to \(U_{ps2}\); When \(z>y\), in accordance with the method of putting the constant voltage branches into operation and the method of switching, putting into and withdrawing, and regulating the voltage regulating branch in the boost control, gradually increase the number of constant voltage branches put into operation from \(y\) to \(z\), and regulate the output voltage of the voltage regulating branch that is in the unlocked state to raise the voltage across the electrolyzer to \(U_{ps2}\); When \(z<y\), in accordance with the method of withdrawing the constant voltage branches and the method of switching, putting into and withdrawing, and regulating the voltage regulating branch in the buck control, gradually reduce the number of constant voltage branches put into operation from \(y\) to \(z\), and regulate the output voltage of the voltage regulating branch that is in the unlocked state to reduce the voltage across the electrolyzer to \(U_{ps2}\).

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