Hydrogen production system

Abstract

This application relates to a hydrogen production system. It includes: a modular multilevel converter (MMC), with its three-phase AC side connected to a three-phase power grid; a photovoltaic module connected to the DC side of the MMC; each arm of the MMC consists of multiple sub-modules connected in series; among the multiple sub-modules, at least one first sub-module is connected to an electrolyzer unit via a DC-DC converter, and at least one second sub-module is connected to an energy storage unit via a DC-DC converter, wherein the first and second sub-modules are different sub-modules among the multiple sub-modules. This hydrogen production system can adapt to changes in power demand under different scenarios and provide a stable power supply to the electrolyzer.

Description

Technical Field

[0001] This application relates to the field of new energy technology, and in particular to a hydrogen production system. Background Technology

[0002] With the expanding application of hydrogen energy in the clean energy field, the demand for stable power supply in water electrolysis hydrogen production technology is becoming increasingly urgent. Currently, most mainstream hydrogen production systems adopt a topology of direct connection between photovoltaic cells and electrolyzers.

[0003] However, the above-mentioned topology suffers from significant power fluctuations in photovoltaic output due to the influence of sunlight and weather, resulting in unstable input current in the electrolyzer. This not only reduces hydrogen production efficiency but also accelerates the aging of the electrolyzer equipment. Furthermore, when it is necessary to increase the scale of hydrogen production or the amount of photovoltaic installations, the system topology needs to be significantly reconstructed, making it difficult to achieve modular expansion and adapt to changes in power demand under different scenarios. Utility Model Content

[0004] Therefore, it is necessary to provide a hydrogen production system that can adapt to changes in power demand under different scenarios and provide stable power supply to the electrolyzer, addressing the aforementioned technical problems.

[0005] In a first aspect, this application provides a hydrogen production system, comprising:

[0006] A modular multilevel converter (MMC) is provided, wherein the three-phase AC side of the MMC is connected to a three-phase power grid.

[0007] A photovoltaic module, wherein the photovoltaic module is connected to the DC side of the MMC;

[0008] Each arm of the MMC consists of multiple sub-modules connected in series; among the multiple sub-modules, at least one first sub-module is connected to an electrolytic cell unit through a DC-DC converter, and at least one second sub-module is connected to an energy storage unit through a DC-DC converter, wherein the first sub-module and the second sub-module are different sub-modules among the multiple sub-modules.

[0009] In one embodiment of the hydrogen production system, a first submodule includes a capacitor, and the two ends of the capacitor in the at least one first submodule are respectively connected in parallel to an electrolyzer unit through a DC-DC converter. The electrolyzer unit is used to discharge the capacitor in the at least one first submodule during operation.

[0010] In one embodiment of the hydrogen production system, the second submodule includes a capacitor, and the two ends of the capacitor in the at least one second submodule are respectively connected in parallel to an energy storage unit through a DC-DC converter. The energy storage unit is used to charge or discharge the capacitor in the at least one second submodule.

[0011] In one embodiment of the hydrogen production system, the photovoltaic module is used to transmit electrical energy to the MMC during operation.

[0012] In one embodiment of the hydrogen production system, the difference between the capacitor voltage of the first submodule and the capacitor voltage of the second submodule is within a preset range.

[0013] In one embodiment of the hydrogen production system, the first submodule and the second submodule have the same proportion.

[0014] In one embodiment of the hydrogen production system, each of the submodules supports both a positive capacitive reference voltage and a zero voltage output.

[0015] In one embodiment of the hydrogen production system, the plurality of submodules include: a half-bridge submodule, or a full-bridge submodule.

[0016] In one embodiment of the hydrogen production system, the system further includes:

[0017] The sampling module is connected to the capacitors of each submodule, each arm of the MMC, the electrolytic cell unit, the energy storage unit, the photovoltaic module, and the three-phase power grid, respectively, and is used to collect the capacitor voltage and arm current of each submodule, the operating parameters of the electrolytic cell unit and the energy storage unit, the operating parameters of the photovoltaic module, and the power grid data of the three-phase power grid.

[0018] In one embodiment of the hydrogen production system, the system further includes:

[0019] The control module is connected to the sampling module, the power switches of each sub-module in the MMC, and the DC-DC converters connected to each sub-module. It is used to analyze the parameters collected by the sampling module, output on / off commands for the power switches of the sub-modules in the MMC, and output current adjustment commands for each DC-DC converter.

[0020] The aforementioned hydrogen production system includes: a modular multilevel converter (MMC), whose three-phase AC side is connected to a three-phase power grid; a photovoltaic module connected to the DC side of the MMC; each arm of the MMC consists of multiple sub-modules connected in series; among the multiple sub-modules, at least one first sub-module is connected to an electrolyzer unit via a DC-DC converter, and at least one second sub-module is connected to an energy storage unit via a DC-DC converter, wherein the first and second sub-modules are different sub-modules among the multiple sub-modules. Through this scheme, the collaborative architecture of the modular multilevel converter (MMC) with the photovoltaic module, electrolyzer unit, and energy storage unit has significant advantages in adapting to changes in power demand and ensuring stable power supply to the electrolyzer. From the perspective of power demand adaptability, the photovoltaic module in the system provides energy for hydrogen production, and its output can dynamically respond to changes in sunlight through maximum power point tracking. The energy storage unit flexibly charges and discharges through the DC-DC converter of the second submodule, storing energy when photovoltaic output is excessive and releasing energy when photovoltaic output is insufficient or the power demand of the electrolyzer suddenly increases. With the interaction and regulation between the MMC and the grid, the system power can be balanced in real time, effectively adapting to power demand fluctuations in different scenarios (such as fluctuations in sunlight, adjustments in hydrogen production load, and changes in grid power supply). In terms of stable power supply, the electrolyzer unit is connected through an independent DC-DC converter of the first submodule, which can obtain independent current and voltage control, and is not directly affected by fluctuations in energy storage unit or photovoltaic output. At the same time, the multi-submodule series structure of the MMC can maintain the stability of DC side voltage. Combined with the active power support of the grid, it provides a continuous and stable DC power supply to the electrolyzer, avoiding the decrease in electrolysis efficiency or equipment damage caused by voltage or current fluctuations. Ultimately, it achieves stable power supply to the electrolyzer and dynamic adaptation of system power under complex operating conditions. Attached Figure Description

[0021] To more clearly illustrate the technical solutions in the embodiments or related technologies of this application, the accompanying drawings used in the description of the embodiments or related technologies will be briefly introduced below. Obviously, the accompanying drawings described below are only some embodiments of this application. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0022] Figure 1 This is a schematic diagram of the architecture of a hydrogen production system in one embodiment;

[0023] Figure 2 This is a schematic diagram of the MMC topology in one embodiment;

[0024] Figure 3 This is a schematic diagram illustrating the integration method of EL-SM and ES-SM in a bridge arm in one embodiment;

[0025] Figure 4This is a schematic diagram of an SM connecting an independent EL unit in one embodiment;

[0026] Figure 5 This is a schematic diagram of multiple SM outputs connected in parallel to the same EL unit in one embodiment;

[0027] Figure 6 This is a schematic diagram of an SM connecting an independent ES unit in one embodiment;

[0028] Figure 7 This is a schematic diagram of multiple SM outputs connected in parallel to the same ES unit in one embodiment. Detailed Implementation

[0029] To make the objectives, technical solutions, and advantages of this application clearer, the following detailed description is provided in conjunction with the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the scope of this application.

[0030] With the widespread application of hydrogen energy as a clean energy carrier, water electrolysis for hydrogen production has become an important means of achieving carbon neutrality. However, traditional photovoltaic-driven electrolyzer systems suffer from power fluctuations. Because photovoltaic output is significantly affected by sunlight and weather, the input current to the electrolyzer is unstable, reducing hydrogen production efficiency and accelerating equipment aging.

[0031] To address these issues, many related technologies employ hybrid photovoltaic (PV) and energy storage systems, using energy storage units to mitigate power fluctuations. However, some PV and energy storage hybrid systems utilize centralized or multi-port topologies, resulting in drawbacks such as low modularity, poor fault tolerance, and limited voltage expansion capabilities. Furthermore, the control methods in these technologies struggle to simultaneously achieve power balance when different renewable energy sources or loads are connected and to ensure stable power supply to the electrolytic cell under multi-source dynamic interaction scenarios.

[0032] To improve the power supply stability of the electrolyzer, this application provides a hydrogen production system and a hydrogen production system control method applied to the hydrogen production system.

[0033] In one exemplary embodiment, Figure 1 This is a schematic diagram of the architecture of a hydrogen production system in one embodiment. Figure 1The hydrogen production system shown includes: a Modular Multilevel Converter (MMC), the three-phase AC side of which is connected to a three-phase power grid 12; a photovoltaic module 11, which is connected to the DC side of the MMC; each arm of the MMC consists of multiple sub-modules connected in series; among the multiple sub-modules, at least one first sub-module is connected to an electrolyzer unit via a DC-DC converter, and at least one second sub-module is connected to an energy storage unit via a DC-DC converter, wherein the first sub-module and the second sub-module are different sub-modules among the multiple sub-modules. The first sub-module connected to the electrolyzer unit can be referred to as EL-SM, and the second sub-module connected to the energy storage unit can be referred to as ES-SM.

[0034] The aforementioned three-phase power grid 12 is connected to the AC side of the MMC, enabling grid-connected operation and supporting bidirectional energy flow. Photovoltaic modules 11 are centrally connected to the DC side of the MMC, providing renewable energy input to the system. These photovoltaic modules 11 are used to transmit electrical energy to the MMC during operation. Each arm of the MMC integrates an EL-SM and an ES-SM. That is, each phase arm consists of multiple sub-modules connected in series. The sub-modules in the arm include an EL-SM for powering the electrolyzer and an ES-SM for connecting the energy storage unit.

[0035] in, Figure 1 middle , and These represent the three-phase currents flowing into or out of the MMC from the power grid. This represents the voltage on the DC side of the MMC, i.e., the DC bus voltage. This indicates the output current of photovoltaic module 11, which is the DC current output by the photovoltaic module.

[0036] In some embodiments, a first submodule is connected to an electrolytic cell unit via a DC-DC converter, or multiple first submodules are connected to an electrolytic cell unit via their respective DC-DC converters.

[0037] In some embodiments, a second submodule is connected to an energy storage unit via a DC-DC converter, or multiple second submodules are connected to an energy storage unit via their respective DC-DC converters.

[0038] For example, Figure 2 This is a schematic diagram of the MMC topology in one embodiment. For example... Figure 2 As shown, the MMC includes 6 bridge arms, and each bridge arm integrates EL-SM and ES-SM. Figure 2 middle , and These represent the three-phase currents flowing into or out of the MMC from the power grid; the upper bridge arms are represented by A1, B1, and C1, and the lower bridge arms are represented by A2, B2, and C2, respectively. , , These represent the voltages of the three-phase upper arms of the MMC bridge. , , These represent the voltages of the three-phase lower bridge arms of the MMC; , , This indicates the current in the upper arm of the three-phase MMC bridge. , , This indicates the current in the lower arm of the three-phase MMC bridge. This represents the total DC current on the DC side of the MMC.

[0039] Figure 3 This is a schematic diagram illustrating the integration of EL-SM and ES-SM in one embodiment of a bridge arm. It can be seen that each bridge arm includes not only multiple EL-SMs but also multiple ES-SMs.

[0040] From a power demand adaptability perspective, the aforementioned MMC architecture features a photovoltaic module that provides energy for hydrogen production. Its output can dynamically respond to changes in sunlight through maximum power point tracking (MPPT). The energy storage unit flexibly charges and discharges via the DC-DC converter in the second submodule, storing energy when photovoltaic output is excessive and releasing energy when photovoltaic output is insufficient or when the electrolyzer's power demand suddenly increases. Combined with the interactive regulation between the MMC and the grid, it can balance system power in real time, effectively adapting to power demand fluctuations under different scenarios (such as sunlight fluctuations, hydrogen production load adjustments, and grid power supply changes). Regarding stable power supply, the electrolyzer unit is connected via an independent DC-DC converter in the first submodule, enabling independent current and voltage control, unaffected by direct interference from energy storage units or photovoltaic output fluctuations. Simultaneously, the multi-submodule series structure of the MMC maintains stable DC-side voltage. Combined with the grid's active power support, it provides a continuous and stable DC power supply to the electrolyzer, preventing electrolysis efficiency degradation or equipment damage due to voltage or current fluctuations. Ultimately, it achieves stable power supply to the electrolyzer and dynamic power adaptation to the system under complex operating conditions.

[0041] In some embodiments, a first submodule of the hydrogen production system includes a capacitor, and the two ends of the capacitor in the at least one first submodule are respectively connected in parallel to an electrolyzer unit through a DC-DC converter. The electrolyzer unit is used to discharge the capacitor in the at least one first submodule during operation, converting the electrical energy of the capacitor into a constant current required by the electrolyzer.

[0042] The DC-DC converter between the electrolytic cell unit and the capacitor of the first submodule is a unidirectional DC-DC converter, through which the electrolytic cell unit draws power from the capacitor.

[0043] In some embodiments, a first submodule is connected to an electrolytic cell unit via a DC-DC converter. For example, Figure 4 This is a schematic diagram of an SM connected to an independent EL unit in one embodiment. Figure 4 The first DC-DC converter 41 is connected between the two ends of a capacitor in a first submodule 42 and the electrolytic cell unit 40.

[0044] It should be noted that, Figure 4 middle This indicates the current flowing into electrolytic cell unit 40; This indicates the input voltage of electrolytic cell 40.

[0045] In some embodiments, multiple first submodules are connected to an electrolytic cell unit via their respective DC-DC converters. Figure 5 This is a schematic diagram of multiple SM outputs connected in parallel to the same EL unit in one embodiment.

[0046] In some embodiments, a second submodule of the hydrogen production system includes a capacitor, and the two ends of the capacitor in the at least one second submodule are respectively connected in parallel to one of the energy storage units via DC-DC converters. The energy storage unit is used to charge or discharge the capacitor in the at least one second submodule.

[0047] In the second submodule, the DC-DC converter between the capacitor and the energy storage unit is a bidirectional DC-DC converter. The energy storage unit interacts bidirectionally with the capacitor through the bidirectional DC-DC converter (the energy storage unit discharges to replenish energy when the capacitor voltage is low, and charges and unloads when the voltage is high).

[0048] In some embodiments, a second submodule is connected to an energy storage unit via a DC-DC converter.

[0049] For example, Figure 6 This is a schematic diagram of an SM connecting to an independent ES unit in one embodiment. Figure 6 The second DC-DC converter 61 is connected between the two ends of a capacitor in a second submodule 62 and the energy storage unit 60.

[0050] It should be noted that, Figure 6 middle The arrow indicates the input / output current flowing into / out of the energy storage unit 60. The bidirectional nature of the arrow indicates that the current can flow into or out, meaning that the energy storage unit can be charged or discharged. This represents the input voltage of the energy storage unit 60, which is the voltage output from the power electronic converter unit to the intermediate conversion stage.

[0051] In some embodiments, multiple second submodules are connected to an energy storage unit via their respective DC-DC converters. For example, Figure 7 This is a schematic diagram of multiple SM outputs connected in parallel to the same ES unit in one embodiment.

[0052] In this configuration, when the SM is connected to an independent EL unit, the capacitor of the EL-SM supplies power to the EL unit through a unidirectional DC-DC converter; when the SM is connected to an independent ES unit, the capacitor of the EL-SM charges or discharges the ES unit through a bidirectional DC-DC converter. This mode is suitable for applications requiring high reliability and high control precision, enabling refined management of each electrolyzer and energy storage unit, and supporting online maintenance and fault isolation. Furthermore, since each DC-DC converter and submodule operates within a low-power range, soft switching and high-efficiency operation are easily achieved.

[0053] In this case, multiple SMs of the same type can also be connected in parallel to form a centralized EL unit or ES unit, such as... Figure 5 As shown, the capacitors of multiple SMs are each connected to their respective unidirectional DC-DC converters. The outputs of these unidirectional DC-DC converters are connected in parallel to the same EL unit, which can increase the supply current density of the EL unit and improve the hydrogen production efficiency. Figure 7 As shown, the capacitors of multiple SMs are connected to their respective bidirectional DC-DC converters, and the outputs of these bidirectional DC-DC converters are then connected in parallel to the same ES unit, enabling high-power rapid charging and discharging of the ES unit. Since the EL-SM and ES-SM remain functionally independent, the system still possesses the control decoupling capability for hydrogen production and energy storage under this connection method.

[0054] The above Figures 4 to 7 The topology in the illustrated embodiment, combined with the control of a unidirectional or bidirectional DC-DC converter, not only achieves refined management, fault isolation, and online maintenance of the electrolyzer unit and the energy storage unit, but also improves efficiency in low-power scenarios and increases hydrogen production current density and energy storage charging and discharging speed through parallel connection of multiple modules in high-power scenarios, while maintaining the decoupling of hydrogen production and energy storage control, thus taking into account system reliability, efficiency, and functional flexibility.

[0055] In some embodiments, the first submodule and the second submodule in the hydrogen production system have the same proportion.

[0056] In this configuration, the proportions of the first submodule and the second submodule in each bridge arm can be set to be the same.

[0057] For example, suppose a bridge arm includes 4 sub-modules, with a ratio of 1:1, there are 2 first sub-modules and 2 second sub-modules. Each first sub-module is connected to an electrolytic cell unit, and each second sub-module is connected to an energy storage unit.

[0058] For example, suppose a bridge arm includes 4 sub-modules, with a ratio of 1:1, there are 2 first sub-modules and 2 second sub-modules, where the 2 first sub-modules are connected to the same electrolytic cell unit and the 2 second sub-modules are connected to the same energy storage unit.

[0059] In some embodiments, the plurality of submodules in the hydrogen production system include: a half-bridge submodule, or a full-bridge submodule. The half-bridge submodule includes two power devices and one capacitor; the full-bridge submodule includes four power devices and one capacitor.

[0060] In some embodiments, when the submodule is a half-bridge submodule, each of the submodules in the hydrogen production system supports both a positive capacitive reference voltage and a zero voltage output.

[0061] Each half-bridge submodule has two built-in power devices (such as IGBTs) and one capacitor. By controlling the on / off state of the two power devices, the submodule can output two levels: a positive capacitor reference voltage (voltage across the capacitor) and a zero level (the capacitor is short-circuited or there is no voltage output), thereby realizing the basic voltage regulation function of the submodule.

[0062] In the above embodiments, the simple topology of the half-bridge submodule ensures both positive and zero output levels to meet the MMC commutation requirements, while significantly reducing the number and size of the submodule hardware, thus lowering system cost and complexity.

[0063] In some embodiments, the submodule is also a full-bridge submodule, and each of the submodules in the hydrogen production system supports three voltage output levels: positive capacitor reference voltage, negative capacitor reference voltage, and zero.

[0064] In some embodiments, the difference between the capacitor voltage of the first submodule and the capacitor voltage of the second submodule in the hydrogen production system is within a preset range.

[0065] For example, the hydrogen production system described above can be configured based on the following voltage matching principle:

[0066] (1) The operating voltage of a single anion exchange membrane electrolyzer unit (electrolyzer unit) is approximately 1.8–2.2V;

[0067] (2) The voltage of a single 314Ah lithium iron phosphate cell (energy storage unit) is approximately 2.5–3.65V;

[0068] (3) After the units are grouped together, the working voltage range of the electrolytic cell stack (electrolytic cell unit) and the energy storage battery pack (energy storage unit) is similar. Here, unit grouping means that the electrolytic cells form an electrolytic cell stack and the battery cells form an energy storage battery pack.

[0069] (4) The DC capacitor voltage of EL-SM and ES-SM is set to the same value to match the group voltage.

[0070] In particular, the input and output voltages of the DC-DC converters in EL-SM and ES-SM are close, with a voltage transformation ratio close to 1:1, which can significantly reduce conversion losses and improve the overall system efficiency. This setup fully utilizes the common voltage characteristics of electrolytic cells and low-voltage large-cell energy storage, enabling efficient energy conversion.

[0071] The voltage matching settings described above are designed to reduce energy conversion losses and ensure efficient and coordinated operation of the system.

[0072] In terms of equipment characteristic adaptation, although there is a voltage difference between a single anion exchange membrane electrolyzer unit (1.8–2.2V) and a single lithium iron phosphate cell (2.5–3.65V), the working voltage range of the two can be made similar by grouping the units together. This solves the basic voltage compatibility problem between the core hydrogen production equipment and the core energy storage equipment, and avoids the increased difficulty of subsequent conversion due to the large voltage difference after grouping.

[0073] From the perspective of submodule and conversion efficiency optimization, setting the DC capacitor voltages of the EL-SM (electrolyzer submodule) and ES-SM (energy storage submodule) to the same value and matching them as group voltages allows the capacitor voltages of the two types of submodules to maintain coordination with the voltages of the corresponding units (electrolyzer stack or energy storage battery pack). Furthermore, it makes the input and output voltages of the DC-DC converters in the EL-SM and ES-SM close, achieving a voltage ratio close to 1:1. This significantly reduces energy loss during the DC-DC conversion process.

[0074] In some embodiments, the hydrogen production system further includes a sampling module, which is connected to the capacitors of each submodule, each arm of the MMC, the electrolyzer unit, the energy storage unit, the photovoltaic module, and the three-phase power grid, respectively, for collecting the capacitor voltage and arm current of each submodule, the operating parameters of the electrolyzer unit and the energy storage unit, the operating parameters of the photovoltaic module, and the power grid data of the three-phase power grid.

[0075] The sampling module, acting as the sensing center of the hydrogen production system, can collect key operating parameters of the system through connections with submodule capacitors (i.e., the capacitors within the submodules), MMC bridge arms, electrolyzer units, energy storage units, photovoltaic modules, and the three-phase power grid. Specifically, it can capture in real time the capacitor voltages of each submodule (reflecting the energy state of the submodule), bridge arm currents (reflecting the power flow within the MMC), operating parameters of the electrolyzers and energy storage units (such as voltage, current, and temperature, used to monitor hydrogen production and energy storage efficiency), power generation parameters of the photovoltaic modules (such as output power and voltage), and grid data from the three-phase power grid (such as voltage, frequency, and harmonics). These collected parameters provide accurate and real-time raw data support for system control and state assessment, forming the foundation for intelligent system regulation.

[0076] In some embodiments, the hydrogen production system further includes a control module, which is connected to the sampling module, the power switches of each sub-module in the MMC, and the DC-DC converters connected to each sub-module. The control module is used to analyze the parameters collected by the sampling module, output on / off commands for the power switches of the sub-modules in the MMC, and output current adjustment commands for each DC-DC converter.

[0077] The aforementioned control module, through its connection with the sampling module, the power switches of the sub-modules in the MMC, and each DC-DC converter, constructs a closed-loop control logic. First, it receives and analyzes various parameters collected by the sampling module, and, combined with system operating objectives (such as hydrogen production efficiency, energy storage charging and discharging requirements, and grid coordination), generates two types of key commands: one is the on / off command for the power switches of the sub-modules in the MMC, which adjusts the input and output levels of the sub-modules to achieve core functions such as voltage balance and power regulation in the MMC; the other is the current regulation command for each DC-DC converter, which precisely controls the supply current of the electrolyzer unit and the charging and discharging current of the energy storage unit, ensuring stable and efficient hydrogen production and flexible response of the energy storage component. The presence of the control module enables organic collaboration among all components of the system, ensuring the overall safety and economy of operation.

[0078] In the above embodiments, the combination of the sampling module and the control module improves the performance of the hydrogen production system. The comprehensive parameter acquisition capability of the sampling module provides the system with complete data covering energy state (capacitor voltage), power flow (bridge arm current), equipment operation (electrolyzer, energy storage, photovoltaic), and external interactions (grid), avoiding blind control due to information gaps and laying a data foundation for precise regulation. The control module, based on this data, can achieve hierarchical, multi-objective coordinated control. Specifically, the topology stability of the converter can be ensured through submodule switching commands in the MMC, and the energy conversion efficiency of hydrogen production and energy storage can be optimized through DC-DC converter current commands. The combination of these two approaches ensures the stable operation of various internal components of the system (such as submodule capacitor voltage balancing and bridge arm circulating current suppression) while also flexibly responding to external demands (such as photovoltaic power consumption and grid peak shaving).

[0079] The aforementioned hydrogen production system integrates EL-SM (electrolyzer submodule) and ES-SM (energy storage submodule) through the MMC architecture. It is equipped with unidirectional or bidirectional DC-DC converters to achieve flexible connection between the submodule and the electrolyzer unit and energy storage unit. Combined with the selection of half-bridge or full-bridge submodules and voltage matching, it not only solves the problem of unstable power supply to the electrolyzer caused by photovoltaic power fluctuations, but also improves the modularity, fault tolerance and energy conversion efficiency of the system. It achieves decoupling of hydrogen production and energy storage control, refined management and efficient coordination with the power grid, and takes into account reliability, economy and scenario adaptability.

[0080] The technical features of the above embodiments can be combined in any way. For the sake of brevity, not all possible combinations of the technical features in the above embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

[0081] The embodiments described above are merely illustrative of several implementation methods of this application, and while the descriptions are specific and detailed, they should not be construed as limiting the scope of this application. It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of this application, and these all fall within the protection scope of this application. Therefore, the protection scope of this application should be determined by the appended claims.

Claims

1. A hydrogen production system, characterized in that, include: A modular multilevel converter (MMC) is provided, wherein the three-phase AC side of the MMC is connected to a three-phase power grid. A photovoltaic module, wherein the photovoltaic module is connected to the DC side of the MMC; Each arm of the MMC consists of multiple sub-modules connected in series; among the multiple sub-modules, at least one first sub-module is connected to an electrolytic cell unit via a DC-DC converter, and at least one second sub-module is connected to an energy storage unit via a DC-DC converter, wherein the first sub-module and the second sub-module are different sub-modules among the multiple sub-modules.

2. The hydrogen production system according to claim 1, characterized in that, The first submodule includes a capacitor, and the two ends of the capacitor in the at least one first submodule are respectively connected in parallel to an electrolytic cell unit through a DC-DC converter. The electrolytic cell unit is used to discharge the capacitor in the at least one first submodule during operation.

3. The hydrogen production system according to claim 1, characterized in that, The second submodule includes a capacitor. The two ends of the capacitor in the at least one second submodule are respectively connected in parallel to one of the energy storage units through a DC-DC converter. The energy storage unit is used to charge the capacitor in the at least one second submodule or to discharge the capacitor in the second submodule.

4. The hydrogen production system according to claim 1, characterized in that, The photovoltaic module is used to transmit electrical energy to the MMC during operation.

5. The hydrogen production system according to any one of claims 1 to 4, characterized in that, The difference between the capacitor voltage of the first submodule and the capacitor voltage of the second submodule is within a preset range.

6. The hydrogen production system according to any one of claims 1 to 4, characterized in that, The first submodule and the second submodule have the same proportion.

7. The hydrogen production system according to any one of claims 1 to 4, characterized in that, Each of the submodules supports both positive capacitive reference voltage and zero voltage output.

8. The hydrogen production system according to any one of claims 1 to 4, characterized in that, The plurality of submodules include: a half-bridge submodule, or a full-bridge submodule.

9. The hydrogen production system according to any one of claims 1 to 4, characterized in that, Also includes: The sampling module is connected to the capacitors of each submodule, each arm of the MMC, the electrolytic cell unit, the energy storage unit, the photovoltaic module, and the three-phase power grid, respectively, and is used to collect the capacitor voltage and arm current of each submodule, the operating parameters of the electrolytic cell unit and the energy storage unit, the operating parameters of the photovoltaic module, and the power grid data of the three-phase power grid.

10. The hydrogen production system according to claim 9, characterized in that, Also includes: The control module is connected to the sampling module, the power switches of each sub-module in the MMC, and the DC-DC converters connected to each sub-module. The control module is used to analyze the parameters collected by the sampling module, output on / off commands for the power switches of the sub-modules in the MMC, and output current adjustment commands for each DC-DC converter.

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