Off-grid new energy hydrogen production system based on direct current transmission

Abstract

The invention provides an off-grid new energy hydrogen production system based on direct current transmission, and the system comprises a transmitting-end power grid which comprises a new energy power generation unit, an energy storage unit and a diode converter, and the energy storage unit is coordinated with the new energy power generation unit and is used for supporting the voltage and frequency of the transmitting-end power grid; the receiving end power grid comprises a flexible direct current converter and a hydrogen production unit, and the hydrogen production unit collects electric energy to the flexible direct current converter; the direct current unit comprises a sending end direct current bus, a direct current line and a receiving end direct current bus; the diode converter is used for converting electric energy and then accessing the converted electric energy to the sending end direct current bus, and the flexible direct current converter is used for converting electric energy and then accessing the converted electric energy to the receiving end direct current bus; and the sending end direct current bus is connected with the receiving end direct current bus through the direct current line so as to transmit active power from the sending end power grid to the receiving end power grid.

Description

Technical Field

[0001] The present application relates to the technical field of renewable energy power generation and hydrogen production, and more specifically, to an off-grid renewable energy hydrogen production system based on direct current transmission. Background Art

[0002] Hydrogen is renewable, has diverse sources, and has high calorific value. In addition, the byproduct of hydrogen is water, which can achieve true pollution-free and zero emission. Therefore, hydrogen is considered to be one of the most promising clean energy sources, and electrolysis hydrogen production technology is also regarded as a green and environmentally friendly hydrogen production technology.

[0003] The power output of renewable energy is intermittent, random and volatile. If renewable energy is directly connected to the public power grid, it will bring huge challenges to the frequency regulation, peak regulation and stability of the power grid. Therefore, in order to meet the stability requirements of the power grid, wind and solar power are often abandoned.

[0004] However, the development of new energy hydrogen production technology will help solve the problem of local consumption of new energy, realize the scale of new energy development and multi-channel efficient utilization, thereby supporting the large-scale development of renewable energy.

[0005] However, due to the real-time fluctuation of the output power of new energy, it is difficult to achieve real-time matching between new energy and hydrogen production units. At present, new energy hydrogen production technology still needs to be connected to the public power grid to achieve power balance and system stability, but there are also some problems: on the one hand, in some "sand deserts" or coastal areas, the objective conditions for connecting to the power grid cannot be met; on the other hand, after the hydrogen production system is connected to the power grid, it still needs to rely on non-renewable energy power plants in the power grid for hydrogen production, and it is impossible to fully achieve green and low-carbon.

[0006] CN114481179A proposes a medium-voltage DC collection type renewable energy power generation and hydrogen production system and its working method, which collects and connects the renewable energy power generation unit, hydrogen production unit and energy storage unit through a medium-voltage DC bus; CN212114804U proposes an off-grid wind power hydrogen production system, which connects the wind turbine, battery energy storage and electrolytic hydrogen production device through a DC bus; CN114389310B proposes a large-capacity off-grid wind-solar complementary hydrogen production DC microgrid and its control method, which collects the medium-voltage AC subnet, hydrogen production unit and low-voltage AC distribution network through a medium-voltage DC distribution board.

[0007] The hydrogen production systems in the above schemes are only applicable to low-pressure or medium-pressure environments, and are not applicable to high-pressure large-scale scenarios. In addition, these schemes involve many conversion links and require high-performance converters, which will increase the cost of the converters and are not economical in large-scale systems.

[0008] The above information disclosed in the Background section is only for enhancement of understanding of the background of the present application and therefore it may contain information that does not constitute the prior art that is already known to a person of ordinary skill in the art. Summary of the invention

[0009] In order to solve at least one of the above problems, the present application proposes an off-grid new energy hydrogen production system based on direct current transmission.

[0010] According to the first aspect of the present application, at least one embodiment of the present application provides an off-grid new energy hydrogen production system based on direct current transmission, comprising:

[0011] A sending-end power grid, comprising a new energy power generation unit, an energy storage unit and a diode converter, wherein the energy storage unit coordinates with the new energy power generation unit to support the voltage and frequency of the sending-end power grid;

[0012] A receiving-end power grid includes a flexible DC converter and a hydrogen production unit, wherein the hydrogen production unit collects electric energy to the flexible DC converter; and

[0013] A DC unit, including a sending-end DC bus, a DC line and a receiving-end DC bus;

[0014] The diode converter is used to convert the electric energy and connect it to the sending-end DC bus, and the flexible DC converter is used to convert the electric energy and connect it to the receiving-end DC bus; the sending-end DC bus and the receiving-end DC bus are connected through the DC line to transmit active power from the sending-end power grid to the receiving-end power grid.

[0015] For example, in some embodiments of the present application, the new energy power generation unit includes:

[0016] A power generation device, comprising at least one of a wind power generation device and a photovoltaic power generation device; and

[0017] An AC line and a transformer, wherein the power generation device is connected to the AC side of the diode converter through the AC line and the transformer.

[0018] For example, in some embodiments of the present application, the energy storage unit includes:

[0019] Energy storage elements, including electrochemical energy storage elements, supercapacitor energy storage elements or flywheel energy storage elements; and

[0020] An AC line and a transformer, wherein the energy storage element is connected to the AC side of the diode converter through the AC line and the transformer.

[0021] For example, in some embodiments of the present application, the diode converter includes:

[0022] Switchgear;

[0023] A filter and a transformer connected in series with the switch device to form a first series branch;

[0024] Diode commutated valves; and

[0025] The smoothing reactor and the starting circuit are connected in series with the diode converter valve to form a second series branch;

[0026] The first series branch is connected to the second series branch.

[0027] For example, in some embodiments of the present application, the diode-converter valve includes a three-phase bridge rectifier circuit, and the three-phase bridge rectifier circuit includes a diode.

[0028] For example, in some embodiments of the present application, the flexible direct current converter includes:

[0029] Switchgear;

[0030] A transformer connected in series with the switch device to form a third series branch;

[0031] Start the circuit; and

[0032] The bridge arm reactor and the flexible DC converter valve are connected in series with the starting circuit to form a fourth series branch;

[0033] Wherein, the third series branch is connected to the fourth series branch.

[0034] For example, in some embodiments of the present application, the flexible direct current converter valve includes a three-phase bridge inverter circuit, wherein:

[0035] The three-phase bridge inverter circuit includes a fully controlled power electronic device.

[0036] For example, in some embodiments of the present application, the DC line includes an overhead line or a cable.

[0037] For example, in some embodiments of the present application, the DC unit includes a pseudo bipolar system or a true bipolar system.

[0038] For example, in some embodiments of the present application, the hydrogen production unit includes:

[0039] Transformers and AC lines; and

[0040] The hydrogen production electrolyzer is connected to the AC side of the flexible DC converter through the transformer and the AC line.

[0041] The present application provides an off-grid new energy hydrogen production system based on direct current transmission. By connecting an energy storage unit in parallel to the new energy power generation unit, the voltage and frequency of the power grid at the sending end are supported by the energy storage unit and the new energy power generation unit. The receiving end power grid is supported by a flexible direct current converter, so that the hydrogen production unit is connected to the receiving end power grid, making the off-grid new energy hydrogen production system stable. The off-grid new energy hydrogen production system commutation link is reduced, and the system cost is reduced. In addition, the new energy and hydrogen production unit no longer need to be connected to the power grid, which can achieve true green and low-carbon.

[0042] It should be understood that the foregoing general description and the following detailed description are exemplary only and are not restrictive of the present application. BRIEF DESCRIPTION OF THE DRAWINGS

[0043] By describing in detail exemplary embodiments thereof with reference to the accompanying drawings, the above and other objects, features and advantages of the present application will become more apparent. The accompanying drawings described below are only some embodiments of the present application, and are not intended to limit the present application.

[0044] Figure 1 A schematic diagram of an off-grid new energy hydrogen production system based on direct current transmission is shown according to an exemplary embodiment;

[0045] Figure 2 Another embodiment of an exemplary off-grid new energy hydrogen production system based on direct current transmission is shown;

[0046] Figure 3 Another embodiment of an exemplary off-grid new energy hydrogen production system based on direct current transmission is shown;

[0047] Figure 4 Another embodiment of an exemplary off-grid new energy hydrogen production system based on direct current transmission is shown;

[0048] Figure 5 Another embodiment of an exemplary off-grid new energy hydrogen production system based on direct current transmission is shown;

[0049] Figure 6 A schematic diagram of a diode converter showing an exemplary embodiment;

[0050] Figure 7 A schematic diagram of a flexible DC converter according to an exemplary embodiment is shown. DETAILED DESCRIPTION

[0051] Example embodiments will now be described more fully with reference to the accompanying drawings. However, example embodiments can be implemented in many forms and should not be construed as limited to the embodiments set forth herein; rather, these embodiments are provided so that this application will be comprehensive and complete and will fully convey the concepts of the example embodiments to those skilled in the art. The same reference numerals in the figures represent the same or similar parts, and thus their repeated description will be omitted.

[0052] The described features, structures or characteristics may be combined in one or more embodiments in any suitable manner. In the following description, many specific details are provided to provide a full understanding of the embodiments of the present disclosure. However, those skilled in the art will appreciate that the technical solutions of the present disclosure may be practiced without one or more of these specific details, or other modes, components, materials, devices, etc. may be adopted. In these cases, known structures, methods, devices, implementations, materials or operations will not be shown or described in detail.

[0053] The flowcharts shown in the accompanying drawings are only exemplary and do not necessarily include all the contents and operations / steps, nor must they be executed in the order described. For example, some operations / steps can be decomposed, and some operations / steps can be combined or partially combined, so the actual execution order may change according to actual conditions.

[0054] The terms "first", "second", etc. in the specification and claims of this application and the above-mentioned drawings are used to distinguish different objects, rather than to describe a specific order. In addition, the terms "including" and "having" and any variations thereof are intended to cover non-exclusive inclusions. For example, a process, method, system, product or device that includes a series of steps or units is not limited to the listed steps or units, but optionally includes steps or units that are not listed, or optionally includes other steps or units inherent to these processes, methods, products or devices.

[0055] Those skilled in the art will appreciate that the drawings are merely schematic diagrams of example embodiments, and the modules or processes in the drawings are not necessarily necessary for implementing the present application, and therefore cannot be used to limit the scope of protection of the present application.

[0056] Figure 1 A schematic diagram of an off-grid new energy hydrogen production system based on direct current transmission is shown according to an exemplary embodiment.

[0057] like Figure 1 As shown, the off-grid new energy hydrogen production system based on DC transmission includes a sending-end power grid 101, a DC unit 102 and a receiving-end power grid 103. The sending-end power grid 101 includes a new energy power generation unit 1011, an energy storage unit 1012 and a diode converter 6. The receiving-end power grid 103 includes a flexible DC converter 10 and a hydrogen production unit 1031. The DC unit 102 includes a sending-end DC bus 7, a DC line 8 and a receiving-end DC bus 9.

[0058] According to the exemplary embodiment, the energy storage unit 1012 and the new energy generation unit 1011 are connected in parallel to the diode converter 6. The diode converter 6 is connected in sequence to the sending-end DC bus 7, the DC line 8, the receiving-end DC bus 9 and the flexible DC converter 10. The hydrogen production unit 1031 is connected to the flexible DC converter 10.

[0059] According to the exemplary embodiment, the energy storage unit 1012 is coordinated with the new energy generation unit 1011 to support the voltage and frequency of the sending-end power grid 101. The diode converter 6 is used to convert the electric energy and then connect it to the sending-end DC bus 7.

[0060] According to some embodiments, the hydrogen production unit 1031 collects the electric energy to the flexible DC converter 10. The flexible DC converter 10 is used to convert the electric energy and then connect it to the receiving end DC bus 9.

[0061] According to the exemplary embodiment, the flexible DC converter 10 is used to support the receiving-end grid 103, so that the hydrogen production unit 1031 is connected to the receiving-end grid 103. The new energy generation unit 1011 and the energy storage unit 1012 coordinate to support the voltage and frequency of the sending-end grid 101. The diode converter 6 rectifies the voltage and frequency of the sending-end grid 101 and transmits them to the receiving-end grid 103.

[0062] According to the exemplary embodiment, the sending-end DC bus 7 and the receiving-end DC bus 9 are connected via a DC line 8 to transmit active power from the sending-end grid 101 to the receiving-end grid 103 .

[0063] According to some embodiments, the diode converter 6 includes a diode converter valve 501, a transformer 502, a filter 506, a start-up circuit 503, a smoothing reactor 504, and a switch device 505. The filter 506, the transformer 502, and the switch device 505 are connected in series to form a first series branch. The smoothing reactor 504, the start-up circuit 503, and the diode converter valve 501 are connected in series to form a second series branch. The first series branch is connected to the second series branch. Figure 6 shown.

[0064] The diode commutator valve includes a three-phase bridge rectifier circuit. The three-phase bridge rectifier circuit includes a 6-pulse circuit or a 12-pulse circuit. The three-phase bridge rectifier circuit includes a diode.

[0065] According to some embodiments, the flexible direct current converter 10 includes a flexible direct current converter valve 601, a transformer 602, a bridge arm reactor 603, a start-up circuit 604, and a switch device 605. The flexible direct current converter valve includes a three-phase bridge inverter circuit. The three-phase bridge inverter circuit includes a fully controlled power electronic device. The flexible direct current converter valve includes a dual-level, three-level, or multi-level topology.

[0066] According to some embodiments, the transformer 602 and the switch device 605 are connected in series to form a third series branch. The bridge arm reactor 603, the flexible DC converter valve 601 and the start-up circuit 604 are connected in series to form a fourth series branch. The third series branch is connected to the fourth series branch. Figure 7 shown.

[0067] According to some embodiments, the DC line 8 comprises an overhead line or a cable.

[0068] According to some embodiments, DC unit 102 includes a pseudo bipolar system or a true bipolar system.

[0069] In the pseudo bipolar system, the sending-end DC bus, the receiving-end DC bus and the DC line of the DC unit 102 only need to include positive and negative poles respectively.

[0070] In a true bipolar system, the DC unit 102 needs to add a metallic return busbar and a metallic return line, such as Figure 5 As shown, the sending-end DC bus and the receiving-end DC bus need to include positive and negative poles and metal return busbars, respectively. The DC line needs to include positive and negative poles and metal return lines to connect multiple off-grid new energy hydrogen production systems based on flexible direct current transmission. This application only takes this as an example, but the application is not limited to this. For example, the metal return busbar and metal return line in the DC unit 102 can be increased accordingly according to the number of off-grid new energy hydrogen production systems based on direct current transmission.

[0071] The present application provides an off-grid new energy hydrogen production system based on direct current transmission. By connecting an energy storage unit in parallel to the new energy power generation unit, the voltage and frequency of the power grid at the sending end are supported by the energy storage unit and the new energy power generation unit. The receiving end power grid is supported by a flexible direct current converter, so that the hydrogen production unit is connected to the receiving end power grid, making the off-grid new energy hydrogen production system stable. The off-grid new energy hydrogen production system commutation link is reduced, and the system cost is reduced. In addition, the new energy and hydrogen production unit no longer need to be connected to the power grid, which can achieve true green and low-carbon.

[0072] Figure 2 Another exemplary embodiment of an off-grid new energy hydrogen production system based on direct current transmission is shown.

[0073] like Figure 2 As shown, the new energy power generation unit 1011 includes a power generation device 10111, an AC line 4, a transformer 3 and a transformer 5. The power generation device 10111 is connected in series with the transformer 3, the AC line 4 and the transformer 5 in sequence, and then connected to the AC side of the diode converter 6.

[0074] According to an exemplary embodiment, the power generation device 10111 includes at least one of a wind power generation device and a photovoltaic power generation device. The power generation device 10111 includes a wind power generation device 2 and a photovoltaic power generation device 1, such as Figure 2 As shown; the power generation device 10111 only includes a wind power generation device 2, such as Figure 3 As shown; the power generation device 10111 only includes a photovoltaic power generation device 1, such as Figure 4 shown.

[0075] According to some embodiments, the energy storage unit 1012 includes an energy storage element 15, an AC line 4, and transformers 3 and 5. The energy storage element 15 is sequentially connected in series with the transformer 3, the AC line 4, and the transformer 5, and then connected to the AC side of the diode converter 6.

[0076] According to some embodiments, the energy storage element 15 includes an electrochemical energy storage element, a supercapacitor energy storage element, or a flywheel energy storage element.

[0077] According to some embodiments, the hydrogen production unit 1031 includes a hydrogen production electrolyzer 104, a transformer 13, a transformer 11 and an AC line 12. The hydrogen production electrolyzer 14 is connected to the AC side of the flexible DC converter 10 after being connected in series with the transformer 13, the AC line 12 and the transformer 11 in sequence.

[0078] According to some embodiments, the wind power generation device 1 , the photovoltaic power generation device 2 , the energy storage unit 15 and the hydrogen production electrolyzer 104 each include at least two working units.

[0079] It should be clearly understood that the present application describes how to form and use specific examples, but the present application is not limited to any details of these examples. On the contrary, based on the teaching of the content disclosed in the present application, these principles can be applied to many other embodiments.

[0080] In addition, it should be noted that the above figures are only schematic illustrations of the processes included in the method according to the exemplary embodiments of the present application, and are not intended to be limiting. It is easy to understand that the processes shown in the above figures do not indicate or limit the time sequence of these processes. In addition, it is also easy to understand that these processes can be performed synchronously or asynchronously, for example, in multiple modules.

[0081] The exemplary embodiments of the present application are specifically shown and described above. It should be understood that the present application is not limited to the detailed structures, configurations or implementations described herein; on the contrary, the present application is intended to cover various modifications and equivalent configurations included in the spirit and scope of the appended claims.

Claims

1. An off-grid new energy hydrogen production system based on direct current transmission, characterized in that: include: A sending-end power grid, comprising a new energy power generation unit, an energy storage unit and a diode converter, wherein the energy storage unit coordinates with the new energy power generation unit to support the voltage and frequency of the sending-end power grid; The receiving-end power grid includes a flexible direct current converter and a hydrogen production unit, wherein the hydrogen production unit collects electric energy to the flexible direct current converter; as well as A DC unit, including a sending-end DC bus, a DC line and a receiving-end DC bus; The diode converter is used to convert the electric energy and connect it to the sending-end DC bus, and the flexible DC converter is used to convert the electric energy and connect it to the receiving-end DC bus; the sending-end DC bus and the receiving-end DC bus are connected through the DC line to transmit active power from the sending-end power grid to the receiving-end power grid.

2. The off-grid new energy hydrogen production system according to claim 1, characterized in that: The new energy power generation unit comprises: A power generation device, comprising at least one of a wind power generation device and a photovoltaic power generation device; and An AC line and a transformer, wherein the power generation device is connected to the AC side of the diode converter through the AC line and the transformer.

3. The off-grid new energy hydrogen production system according to claim 1, characterized in that: The energy storage unit comprises: Energy storage elements, including electrochemical energy storage elements, supercapacitor energy storage elements or flywheel energy storage elements; and An AC line and a transformer, wherein the energy storage element is connected to the AC side of the diode converter through the AC line and the transformer.

4. The off-grid new energy hydrogen production system according to claim 1, characterized in that: The diode converter comprises: Switchgear; A filter and a transformer connected in series with the switch device to form a first series branch; Diode commutated valves; and The smoothing reactor and the starting circuit are connected in series with the diode converter valve to form a second series branch; The first series branch is connected to the second series branch.

5. The off-grid new energy hydrogen production system according to claim 4, characterized in that: The diode commutator valve includes a three-phase bridge rectifier circuit, and the three-phase bridge rectifier circuit includes a diode.

6. The off-grid new energy hydrogen production system according to claim 1, characterized in that: The flexible direct current converter comprises: Switchgear; A transformer connected in series with the switch device to form a third series branch; Start the circuit; and The bridge arm reactor and the flexible DC converter valve are connected in series with the starting circuit to form a fourth series branch; Wherein, the third series branch is connected to the fourth series branch.

7. The off-grid new energy hydrogen production system according to claim 6, characterized in that: The flexible direct current converter valve comprises a three-phase bridge inverter circuit, wherein: The three-phase bridge inverter circuit includes a fully controlled power electronic device.

8. The off-grid new energy hydrogen production system according to claim 1, characterized in that: The DC line includes an overhead line or a cable.

9. The off-grid new energy hydrogen production system according to claim 1, characterized in that: The DC unit includes a pseudo bipolar system or a true bipolar system.

10. The off-grid new energy hydrogen production system according to claim 1, characterized in that: The hydrogen production unit comprises: Transformers and AC lines; and The hydrogen production electrolyzer is connected to the AC side of the flexible DC converter through the transformer and the AC line.

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