WO2023050223A1

WO2023050223A1 - Hydrogen production system and control method therefor

Info

Publication number: WO2023050223A1
Application number: PCT/CN2021/121939
Authority: WO
Inventors: 张文平; 姚吉隆
Original assignee: 西门子（中国）有限公司
Priority date: 2021-09-29
Filing date: 2021-09-29
Publication date: 2023-04-06
Also published as: CN117941198A

Abstract

A hydrogen production system (100, 400), comprising: a photovoltaic assembly (102, 402), a power grid (104, 404), at least one modular multilevel converter (106, 406) and a hydrogen electrolyzer (108, 408), the modular multilevel converter (106, 406) comprising at least one phase unit (1062, 4062), each phase unit (1062, 4062) comprising an upper bridge arm (1062-1, 4062-1) and a lower bridge arm (1062-2, 4062-2), and the upper bridge arm (1062-1, 4062-1) and the lower bridge arm (1062-2, 4062-2) each comprising at least one power module (1060, 4060), wherein the photovoltaic assembly (102, 402) is connected to a direct current bus side (DC-BUS) of the modular multilevel converter (106, 406); the power grid (104, 404) is connected to an alternating current bus side (AC-BUS) of the modular multilevel converter (106, 406); and DC side output of the power modules (1060, 4060) of the modular multilevel converter (106, 406) are connected in parallel together to supply power to the hydrogen electrolyzer (108, 408). While the use of photovoltaic power is maximized, the intermittent effect of photovoltaics is eliminated, and the function of supply to the hydrogen electrolyzer (108, 408) is maintained to be stable.

Description

Hydrogen production system and its control method

technical field

The present disclosure generally relates to the technical field of hydrogen production, and more particularly, to a hydrogen production system and a control method thereof.

Background technique

At present, there has been much research on the use of solar photovoltaic (photovoltaic, PV) energy to power electrolyzers to produce hydrogen, which has a very low carbon footprint.

It is very necessary to study the topology of large-scale hydrogen production systems (usually used in industrial production). Since hydrogen electrolyzers are characterized by low voltage and ultra-high current, the converter topology should be able to handle ultra-high current.

As we all know, photovoltaics are intermittent and the power generated is unstable, which will affect the service life of the hydrogen electrolyzer.

One solution to the high-power hydrogen storage topology in the prior art is to connect multiple DC/DC converters in parallel to handle the high current of the hydrogen electrolyzer. In addition, high currents can be further handled by using parallel switches in each module. High-power converters usually use IGBTs. However, the power current sharing problem of parallel IGBTs faces challenges.

In another solution, on the PV side, each PV module has a boost converter. The DC/DC converter then feeds the parallel DC/AC converter which converts the DC to AC. Then, an uncontrolled AC/DC rectifier is connected to power the hydrogen electrolyzer. However, this solution has the following disadvantages:

1) The number of transformation stages is relatively high, which may affect the system efficiency.

2) A power frequency transformer is introduced into this system, which increases the volume of the system.

In yet another solution, each PV module has a DC/DC converter, and the outputs are then connected in series to power the hydrogen electrolyzer. The main disadvantages of this scheme are as follows:

1) Each photovoltaic module has its own DC/DC converter, which brings high costs and is not suitable for high-power systems.

2) The photovoltaic DC/DC converter is connected in series to power the hydrogen electrolyzer, which does not match the low-voltage characteristics of the hydrogen electrolyzer.

In yet another solution, the system is very simple and does not contain power electronic converters. However, in this solution, the voltage and power are not controlled, which affects the efficiency and lifetime of the hydrogen electrolyzer.

Contents of the invention

A brief overview of the invention is given below in order to provide a basic understanding of some aspects of the invention. It should be understood that this summary is not an exhaustive overview of the invention. It is not intended to identify key or critical parts of the invention nor to delineate the scope of the invention. Its purpose is merely to present some concepts in a simplified form as a prelude to the more detailed description that is discussed later.

In view of this, the present invention proposes a hydrogen production system and a control method for the hydrogen production system.

According to one aspect of the present disclosure, a hydrogen production system is provided, including: a photovoltaic module, a power grid, at least one modular multilevel converter, and a hydrogen electrolyzer, and the modular multilevel converter includes at least one Each phase unit includes an upper bridge arm and a lower bridge arm, and the upper bridge arm and the lower bridge arm respectively include at least one power module, wherein the photovoltaic module is connected to the DC bus of the modular multilevel converter side; the grid is connected to the AC bus side of the modular multilevel converter; and the DC side outputs of the power modules of the modular multilevel converter are connected in parallel to supply power to the hydrogen electrolyzer .

Optionally, in an example of the above aspect, the power module adopts an isolation topology circuit.

Optionally, in an example of the above aspect, the isolated topology circuit includes a DC/AC and a DC/DC two-stage, wherein the DC/AC is a two-level DC/AC or a three-level DC/AC Any one of, the DC/DC is any one of LLC DC/DC and full-bridge phase-shifted DC/DC.

According to another aspect of the present disclosure, a method for controlling a hydrogen production system is provided, used for controlling the above-mentioned hydrogen production system, the control method includes: adjusting the power of the modular multilevel converter of the hydrogen production system The current on the DC bus side is used to track the maximum power point of the photovoltaic component, and the maximum power of the photovoltaic component is used to supply power to the hydrogen electrolyzer; and when the actual power of the photovoltaic component is less than the power reference value of the hydrogen electrolyzer , the grid provides differential power to the hydrogen electrolyzer to keep the power supplied to the hydrogen electrolyzer constant, wherein the differential power is the difference between the power reference value of the hydrogen electrolyzer and the actual power of the photovoltaic module.

Optionally, in an example of the above aspect, the power on the grid side is bidirectional, and the control method further includes: when the actual power of the photovoltaic module is greater than the power reference value of the hydrogen electrolyzer , feeding the excess power generated by the photovoltaic components to the grid.

According to another aspect of the present disclosure, a hydrogen production system is provided, including: a photovoltaic module, a power grid, at least one modular multilevel converter, a hydrogen electrolyzer, a photovoltaic-side DC/AC converter, and a grid-side DC/AC converter. In an AC converter, the modular multilevel converter includes at least one phase unit, each phase unit includes an upper bridge arm and a lower bridge arm, and the upper bridge arm and the lower bridge arm respectively include at least one power module, wherein the The photovoltaic module is connected to the AC bus side of the modular multilevel converter through the photovoltaic side DC/AC converter; the power grid is connected to the modular multilevel converter through the grid side DC/AC converter The DC bus side of the converter; and the DC side output of the power module of the modular multilevel converter are connected in parallel to supply power to the hydrogen electrolyzer.

Compared with the prior art, the technical solution of the present invention has at least one of the following advantages.

Using grid photovoltaic hybrid power supply, while maximizing the use of photovoltaic power, use the power provided by the grid to eliminate the intermittent impact of photovoltaic, and maintain the stability of the power provided to the hydrogen electrolyzer;

Provide ultra-high current and low voltage output for hydrogen electrolyzer;

Modular design with redundancy;

Using modular multilevel converters, it is easy to configure to match different power ratings of grid, photovoltaic and hydrogen electrolyzer;

High-frequency transformer isolation is adopted, and the system volume is small;

High efficiency, relatively few conversion stages.

Description of drawings

The above and other objects, features and advantages of the present invention will be more easily understood with reference to the following description of the embodiments of the present invention in conjunction with the accompanying drawings. The components in the drawings are only to illustrate the principles of the invention. In the drawings, the same or similar technical features or components will be denoted by the same or similar reference numerals. In the attached picture:

Fig. 1 is an exemplary topological diagram of a hydrogen production system according to an embodiment of the present invention;

2A is a flowchart of an exemplary process of a method for controlling a hydrogen production system according to an embodiment of the present invention;

Fig. 2B is a control schematic diagram of a hydrogen production system according to an embodiment of the present invention;

Fig. 2C is a schematic diagram of specific control of the hydrogen production system according to an embodiment of the present invention;

Fig. 3 is an exemplary topological diagram of a hydrogen production system according to another embodiment of the present invention;

Fig. 4A is an exemplary topological diagram of a hydrogen production system according to yet another embodiment of the present invention;

Fig. 4B is a schematic diagram of the specific control of the hydrogen production system according to another embodiment of the present invention.

Wherein, the reference signs are as follows:

100, 300, 400:

hydrogen production system

102, 302, 402: photovoltaic modules

104, 304, 404: power grid 106, 306, 306-1, 306-2, 406: modular

Multilevel Converter

108, 308, 408: hydrogen electrolyzer 1062, 4062: phase unit

1062-1, 4062-1: upper bridge arm 1062-2, 4062-2: lower bridge arm

1060, 4060: power module DC-BUS: DC bus

AC-BUS: AC bus side 200: Control method

S202, S204, S206: step 410: photovoltaic side DC/AC converter

412: Grid side DC/AC converter

Detailed ways

The subject matter described herein will now be discussed with reference to example implementations. It should be understood that the discussion of these implementations is only to enable those skilled in the art to better understand and realize the subject matter described herein, and is not intended to limit the protection scope, applicability or examples set forth in the claims. Changes may be made in the function and arrangement of elements discussed without departing from the scope of the disclosure. Various examples may omit, substitute, or add various procedures or components as needed. For example, the methods described may be performed in an order different from that described, and various steps may be added, omitted, or combined. Additionally, features described with respect to some examples may also be combined in other examples.

As used herein, the term "comprising" and its variants represent open terms meaning "including but not limited to". The term "based on" means "based at least in part on". The terms "one embodiment" and "an embodiment" mean "at least one embodiment." The term "another embodiment" means "at least one other embodiment." The terms "first", "second", etc. may refer to different or the same object. The following may include other definitions, either express or implied. Unless the context clearly indicates otherwise, the definition of a term is consistent throughout the specification.

In view of this, the present invention is based on the consideration of how to maximize the use of PV power while keeping the power of the hydrogen electrolyzer stable to eliminate the intermittent impact of PV. A hydrogen production system powered by a photovoltaic-grid hybrid is proposed. While maximizing the use of photovoltaic power, the power provided by the grid is used to eliminate the intermittent impact of photovoltaics and maintain stable power for the hydrogen electrolyzer.

A hydrogen production system and a control method thereof according to an embodiment of the present disclosure will be described in detail below with reference to the accompanying drawings.

FIG. 1 is an exemplary topological diagram of a hydrogen production system 100 according to an embodiment of the present invention.

As shown in FIG. 1 , the hydrogen production system 100 includes a photovoltaic module 102 , a grid 104 , at least one modular multilevel converter 106 and a hydrogen electrolyzer 108 .

In FIG. 1 , the modular multilevel converter 106 includes three phase units 1062 , each phase unit includes an upper bridge arm and a lower bridge arm, and the upper bridge arm and the lower bridge arm respectively include at least one power module 1060 .

Those skilled in the art can understand that the number of phase units included in the modular multilevel converter 106 may not be limited to three.

In the hydrogen production system 100, the photovoltaic module 102 is connected to the DC bus side DC-BUS of the modular multilevel converter 106; the grid 104 is connected to the AC bus side AC-BUS of the modular multilevel converter 106; The DC side outputs of the power modules of the modular multilevel converter 106 are connected in parallel to supply power to the hydrogen electrolyzer 108 .

In the hydrogen production system 100, since the DC side outputs of all power modules are connected in parallel, the ultra-high current of the hydrogen electrolyzer 108 can be handled; and since the outputs are all connected together, the power modules should adopt an isolated topology circuit. The isolation topology circuit includes DC/AC and DC/DC secondary, DC/AC can be, for example, two-level DC/AC or three-level DC/AC, and DC/DC can be LLC DC/DC or full-bridge phase-shifted DC/ One of a kind in DC. Those skilled in the art can also choose other forms of isolation topology circuits according to needs, and are not limited to the topology forms described here.

For the power balance of each power module, traditional power balance methods can be used, such as CAN-based average current control and droop control.

It can be understood that for high-power converters, redundancy and modular design are very important, even if a module fails, it will not affect the operation of the entire system; in addition, large capacity and scalability are also very important for the system.

The hydrogen production system 100 according to the invention is based on a modular multilevel converter (MMC), thus inheriting the characteristics of the MMC. For example, the number of phase units of the modular multilevel converter can be set according to the power grid, photovoltaic and hydrogen electrolyzer’s rated power, and the number of power modules in each bridge arm can also be determined according to the needs, so The hydrogen production system according to the present invention has redundancy capability; and is easy to expand due to the modular design.

The control method of the hydrogen production system according to the embodiment of the present invention will be described below with reference to FIGS. 2A-2C .

Fig. 2A is a flowchart of an exemplary process of a method 200 for controlling a hydrogen production system according to an embodiment of the present invention.

As shown in Figure 2A, first, in step S202, the current of the DC-BUS of the modular multilevel converter 106 of the hydrogen production system 100 is adjusted to track the maximum power point of the photovoltaic module 102, and the photovoltaic module 102 The maximum power of is supplied to the hydrogen electrolyzer 108.

In step S204 , when the power of the photovoltaic module 102 is less than the required power of the hydrogen electrolyzer 108 , the power grid 104 provides differential power to the hydrogen electrolyzer 108 to keep the power supplied to the hydrogen electrolyzer 108 constant.

The differential power here refers to the difference between the power required by the hydrogen electrolyzer 108 and the power provided by the photovoltaic module 102 .

Fig. 2B is a schematic diagram of controlling the hydrogen production system according to an embodiment of the present invention, and Fig. 2C is a schematic diagram of controlling the voltage of each bridge arm of the hydrogen production system.

In Figures 2B and 2C, abc/dq0 represents the transformation from abc coordinates to dq0 coordinates, _PG * represents the given power on the grid side (also called reference value, the same below), and P _H2 * represents the given power of the hydrogen electrolyzer, P _PV * means photovoltaic power reference, _PG means grid side power feedback (also called actual value, the same below), _igd * means grid side d-axis current setting, _igd means grid side d-axis current feedback, d _d * means d-axis duty cycle setting, i _gq * means grid side q-axis current setting, i _gq means grid side q-axis current feedback, d _q * means q-axis duty cycle setting, i _g0 *: Indicates the 0-axis current setting on the grid side, i _g0 indicates the 0-axis current feedback on the grid side, d ₀ * indicates the 0-axis duty cycle setting, P _MPPT * indicates the photovoltaic maximum power tracking command, P _PV indicates photovoltaic power feedback, i _dc * indicates the current setting of the DC side, i _dc indicates the current feedback of the DC side, d _dc * indicates the corresponding duty cycle setting of the DC side, i _loop1 * indicates the current setting of the loop1 of the circulation loop, and i _loop1 indicates the current feedback of the loop1 of the circulation loop, d _loop1 * indicates that the circulating current loop loop1 generates the corresponding duty ratio setting, i _loop2 * indicates the circulating current loop loop2 current setting, i _loop2 indicates the circulating current loop loop2 current feedback, d _loop2 * indicates that the circulating current loop loop2 generates the corresponding duty ratio setting, V _ap means ap bridge arm voltage, V _ap * means ap bridge arm voltage given, V _bp means bp bridge arm voltage, V _bp * means bp bridge arm voltage given, V _cp means cp bridge arm voltage, V _cp * means cp bridge arm voltage given, V _an means an bridge arm voltage, V _an * means an bridge arm voltage given, V _bn means bn bridge arm voltage, V _bn * means bn bridge arm voltage given, V _cn means cn bridge arm voltage Arm voltage, V _cn * means cn bridge arm voltage given, 210 means branch energy balance loop.

It can be understood that maximum power point tracking (Maximum Power Point Tracking (MPPT)) of photovoltaics can be realized by controlling the current i _dc of the DC-BUS of the modular multilevel converter 106 of the hydrogen production system 100 . Therefore, the MTTP loop output is set to be the reference current i _dc * of i _dc .

Through the control method shown in Figure 2C, the maximum power point of the photovoltaic module can be tracked, and the hydrogen electrolyzer can be supplied with the maximum power of the photovoltaic module.

The grid-side power reference is set to the power reference of the hydrogen electrolyzer minus the power feedback of the photovoltaic module, that is, _PG *= _PH2 *-P _PV.

Those skilled in the art can understand the specific process of controlling the hydrogen production system according to the present invention with reference to FIGS. 2A-2C , which will not be described in detail here.

In this way, the power provided to the hydrogen electrolyzer can be kept constant, thereby eliminating the impact of PV intermittent on the hydrogen production system.

Preferably, the power on the grid side can also be bidirectional. The control method 200 may further include step S206 , when the power feedback of the photovoltaic assembly 102 is greater than the given power of the hydrogen electrolyzer 108 , the excess power generated by the photovoltaic assembly 102 may be fed to the grid 104 .

In this way, the hydrogen production system according to the present invention can maximize the utilization rate of the electric energy generated by the photovoltaic module, and at the same time ensure that the electric energy supplied to the hydrogen electrolyzer remains stable.

FIG. 3 shows an exemplary topology diagram of a hydrogen production system 300 according to another embodiment of the present invention.

The hydrogen production system 300 in FIG. 3 includes a photovoltaic module 302 , a grid 304 and a hydrogen electrolyzer 308 .

The structures and functions of the photovoltaic module 302, the grid 304, and the hydrogen electrolyzer 308 are similar to those of the photovoltaic module 102, the grid 104, and the hydrogen electrolyzer 108 described above with reference to FIG. 1 , and will not be repeated here.

Besides, in the hydrogen production system 300 in FIG. 3 , two modular multilevel converters 306-1 and 306-2 are included.

When the power of the hydrogen electrolyzer increases, the input voltage of the hydrogen electrolyzer also increases. In order to match the higher voltage of the hydrogen electrolyzer, another solution of the hydrogen production system as shown in Fig. 3 is provided. In the hydrogen production system shown in Figure 3, two modular multilevel converters are used, and the number of phase units is increased from three to six. The parallel output voltages of the power modules of the two modular multilevel converters are connected together in series to match the higher voltage of the hydrogen electrolyzer.

Those skilled in the art can also set more modular multilevel converters according to the power requirements of the hydrogen electrolyzer, not limited to the two modular multilevel converters shown in FIG. 3 .

The hydrogen production system according to this embodiment can be applied to hydrogen electrolyzers with higher power, and the number of modular multilevel converters, the number of phase units, and The number of power modules will not be described in detail here.

Fig. 4 shows an exemplary topology diagram of a hydrogen production system 400 according to yet another embodiment of the present invention.

As shown in FIG. 4 , the hydrogen production system 400 includes a photovoltaic module 402 , a grid 404 , at least one modular multilevel converter 406 and a hydrogen electrolyzer 408 .

Among them, the structure and function of the photovoltaic assembly 402, the grid 404, the modular multilevel converter 406 and the hydrogen electrolyzer 408 are the same as those of the photovoltaic assembly 102, the grid 104, at least one modular multilevel converter described above with reference to FIG. The current flow device 106 is similar to the hydrogen electrolyzer 108, and will not be repeated here.

In addition, the hydrogen production system 400 also includes a photovoltaic side DC/AC converter 410 and a grid side DC/AC converter 412, and the photovoltaic module 402 is connected to a modular multilevel converter via the photovoltaic side DC/AC converter 410 The AC bus side of 406; the power grid 404 is connected to the DC bus side of the modular multilevel converter 406 via the grid side DC/AC converter 412; the DC side outputs of the power modules of the modular multilevel converter 406 are connected in parallel together supply power to the hydrogen electrolyzer 408 .

In the hydrogen production system according to this embodiment of the present invention, the connection positions of the grid and the photovoltaic modules are exchanged, providing a different topology. Those skilled in the art can select an appropriate topology of the hydrogen production system according to needs.

In the topology of the hydrogen production system shown in Figure 4, those skilled in the art can also set up two MMCs or more MMCs as required, and the specific connection mode and operation process of multiple MMCs are the same as the hydrogen production described in Figure 3 The system is similar and will not be repeated here.

Fig. 4B is a control diagram for the hydrogen production system topology shown in Fig. 4A.

In Figures 4A and 4B, _id * represents the d-axis current setting on the photovoltaic inverter side, _id represents the d-axis current feedback on the photovoltaic inverter side, and i _q * represents the q-axis current setting on the photovoltaic inverter side , i _q represents the q-axis current feedback on the PV inverter side, i ₀ * represents the 0-axis current setting on the PV inverter side, i ₀ represents the 0-axis current feedback on the PV inverter side, and i _dc * represents the bus current on the grid side Given, i _dc represents the grid-side bus current feedback, and the meanings of other variables are the same as those shown in Figs. 2A-2C , and will not be repeated here.

Those skilled in the art can control the hydrogen production system shown in FIG. 4A according to the control schematic diagram shown in FIG. 4B, so as to realize power supply to the hydrogen electrolyzer with the maximum power of the photovoltaic module, and provide the differential power to the hydrogen electrolyzer from the power grid. In order to keep the power supplied to the hydrogen electrolyzer constant, it will not be described in detail here.

Provide ultra-high current and low voltage output for hydrogen electrolyzer;

Modular design with redundancy;

High-frequency transformer isolation, small size;

High efficiency, relatively few conversion stages.

It should be understood that each embodiment in this specification is described in a progressive manner, and the same or similar parts of each embodiment can be referred to each other, and each embodiment focuses on the difference with other embodiments. the difference.

Not all units in the above system structure diagrams are necessary, and some units can be ignored according to actual needs. The device structures described in the above embodiments may be physical structures or logical structures, that is, some units may be implemented by the same physical entity, or some units may be respectively implemented by multiple physical entities, or may be implemented by multiple physical entities. Certain components in individual devices are implemented together.

The specific implementation manner described above in conjunction with the accompanying drawings describes exemplary embodiments, but does not represent all embodiments that can be realized or fall within the protection scope of the claims. As used throughout this specification, the term "exemplary" means "serving as an example, instance, or illustration," and does not mean "preferred" or "advantaged" over other embodiments. The detailed description includes specific details for the purpose of providing an understanding of the described technology. However, the techniques may be practiced without these specific details. In some instances, well-known structures and devices are shown in block diagram form in order to avoid obscuring the concepts of the described embodiments.

The above description of the present disclosure is provided to enable any person of ordinary skill in the art to make or use the present disclosure. Various modifications to this disclosure will be readily apparent to those skilled in the art, and the general principles defined herein can also be applied to other variants without departing from the scope of this disclosure. . Thus, the disclosure is not intended to be limited to the examples and designs described herein but is to be accorded the widest scope consistent with the principles and novel features disclosed herein.

The above descriptions are only preferred embodiments of the present invention, and are not intended to limit the present invention. Any modifications, equivalent replacements, improvements, etc. made within the spirit and principles of the present invention shall be included in the scope of the present invention. within the scope of protection.

Claims

A hydrogen production system (100), comprising: a photovoltaic module (102), a grid (104), at least one modular multilevel converter (106) and a hydrogen electrolyzer (108), the modular multilevel converter The device (106) includes at least one phase unit (1062), each phase unit (1062) includes an upper bridge arm (1062-1) and a lower bridge arm (1062-2), and an upper bridge arm (1062-1) and a lower bridge arm The arms (1062-2) respectively include at least one power module (1060), wherein,

The photovoltaic module (102) is connected to the DC bus side (DC-BUS) of the modular multilevel converter (106);

The grid (104) is connected to the AC bus side (AC-BUS) of the modular multilevel converter (106); and

The DC side outputs of the power modules (1060) of the modular multilevel converter (106) are connected in parallel to supply power to the hydrogen electrolyzer (108).
The hydrogen production system (100) according to claim 1, wherein the power module (1060) adopts an isolated topology circuit.
The hydrogen production system (100) according to claim 2, wherein the isolated topological circuit comprises DC/AC and DC/DC two stages, wherein the DC/AC is two-level DC/AC or three-level Any one of DC/AC, the DC/DC is any one of LLC DC/DC and full-bridge phase-shifted DC/DC.
A control method for a hydrogen production system, used to control the hydrogen production system according to any one of claims 1-3, the control method comprising:

adjusting the current on the DC bus side of the modular multilevel converter of the hydrogen production system to track the maximum power point of the photovoltaic module, and supplying power to the hydrogen electrolyzer with the maximum power of the photovoltaic module; and

In the case that the actual power of the photovoltaic module is less than the power reference value of the hydrogen electrolyzer, the grid provides a balance power to the hydrogen electrolyzer to keep the power supplied to the hydrogen electrolyzer constant, wherein the difference The power is the difference between the power reference value of the hydrogen electrolyzer and the actual power of the photovoltaic module.
The method according to claim 4, wherein the power on the grid side is bidirectional, and the control method further comprises:

In the case that the actual power of the photovoltaic component is greater than the power reference value of the hydrogen electrolyzer, the excess power generated by the photovoltaic component is fed to the grid.
A hydrogen production system (400), including: a photovoltaic module (402), a grid (404), at least one modular multilevel converter (406), a hydrogen electrolyzer (408), a photovoltaic side DC/AC converter (410 ) and a grid-side DC/AC converter (412), the modular multilevel converter (406) includes at least one phase unit (4062), each phase unit includes an upper bridge arm (4062-1) and a lower The bridge arm (4062-2), the upper bridge arm (4062-1) and the lower bridge arm (4062-2) respectively include at least one power module (4060), wherein,

The photovoltaic module (402) is connected to the AC bus side (AC-BUS) of the modular multilevel converter (406) via the photovoltaic side DC/AC converter (410);

The grid is connected to the DC bus side (DC-BUS) of the modular multilevel converter (406) via the grid-side DC/AC converter (412); and

The DC side outputs of the power modules (4060) of the modular multilevel converter (406) are connected in parallel to supply power to the hydrogen electrolyzer (408).
The hydrogen production system (400) according to claim 6, wherein the power module (4060) adopts an isolated topology circuit.
The hydrogen production system (400) according to claim 6, wherein the isolated topological circuit comprises DC/AC and DC/DC two stages, wherein the DC/AC is two-level DC/AC or three-level Any one of DC/AC, the DC/DC is any one of LLC DC/DC and full-bridge phase-shifted DC/DC.