Off-grid type new energy hydrogen production system based on flexible direct delivery

Abstract

The invention provides an off-grid new energy hydrogen production system based on flexible direct transmission, which comprises a direct current energy storage unit, a new energy power generation unit, a transmitting end flexible direct current converter, a direct current unit, a receiving end flexible direct current converter and a hydrogen production unit, and is characterized in that the direct current unit comprises a transmitting end direct current bus, a direct current line and a receiving end direct current bus; the new energy power generation unit gathers electric energy to the sending end flexible direct current converter, and the sending end flexible direct current converter is used for converting the electric energy and connecting the converted electric energy to the sending end direct current bus; the hydrogen production unit gathers electric energy to the receiving-end flexible direct current converter, and the receiving-end flexible direct current converter is used for converting the electric energy and connecting the converted electric energy to a receiving-end direct current bus; the sending end direct-current bus is connected with the receiving end direct-current bus through a direct-current line so as to transmit the active power from the sending end to the receiving end; and the direct current energy storage unit is connected in parallel between the sending end direct current bus and the direct current line or between the receiving end direct current bus and the direct current line, and is used for maintaining direct current voltage stability and power balance of the off-grid new energy hydrogen production system.

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 flexible direct current transmission. Background Art

[0002] The power output of new energy is intermittent, random and volatile. If it is directly connected to the public power grid, it will bring great challenges to the frequency regulation, peak regulation and stability of the public power grid. Therefore, in order to meet the stability requirements of the power grid, wind and solar power abandonment often occurs.

[0003] Hydrogen is renewable, has diverse sources, and has a high calorific value. Its utilization product is water, which can truly achieve zero pollution and zero emissions. Therefore, hydrogen is regarded as 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.

[0004] Therefore, the development of new energy hydrogen production technology is conducive to solving the problem of local consumption of new energy, realizing the scale of new energy development and the efficient use of new energy in multiple channels, and 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, some "sand deserts" or coastal areas do not have the objective conditions for access to the power grid; on the other hand, after access to the power grid, the hydrogen production system still needs to rely on non-renewable energy power plants in the power grid to achieve hydrogen production, and it is impossible to achieve completely 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 of the above schemes are only suitable for low-pressure or medium-pressure environments and are not feasible for high-pressure large-scale environments. In addition, there are many conversion links in the above schemes, which require inverters with better performance, which will increase the cost of the inverter 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 flexible 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 flexible direct current transmission, wherein the off-grid new energy hydrogen production system comprises a direct current energy storage unit, a new energy power generation unit, a sending-end flexible direct current converter, a direct current unit, a receiving-end flexible direct current converter and a hydrogen production unit, wherein:

[0011] The DC unit includes a sending-end DC bus, a DC line and a receiving-end DC bus;

[0012] The new energy power generation unit collects electric energy to the sending-end flexible DC converter, and the sending-end flexible DC converter is used to convert the electric energy and then connect it to the sending-end DC bus;

[0013] The hydrogen production unit collects electric energy to the receiving-end flexible DC converter, and the receiving-end flexible DC converter is used to convert the electric energy and then connect it to the receiving-end DC bus;

[0014] The sending-end DC busbar is connected to the receiving-end DC busbar through the DC line to transmit active power from the sending end to the receiving end;

[0015] The DC energy storage unit is connected in parallel between the sending-end DC bus and the DC line or between the receiving-end DC bus and the DC line to maintain DC voltage stability and power balance of the off-grid new energy hydrogen production system.

[0016] For example, in some embodiments of the present application, the new energy power generation unit includes a power generation device, an AC line and a transformer, wherein:

[0017] The power generation device includes at least one of a wind power generation device and a photovoltaic power generation device;

[0018] The power generation device is connected to the AC side of the sending-end flexible DC converter through the AC line and the transformer.

[0019] For example, in some embodiments of the present application, the sending-end flexible DC converter and the receiving-end flexible DC converter both include a flexible DC converter valve, a transformer, a bridge arm reactor, a starting circuit and a switch device, wherein:

[0020] The transformer and the switch device are connected in series to form a first series branch;

[0021] The bridge arm reactor, the flexible DC converter valve and the starting circuit are connected in series to form a second series branch;

[0022] The first series branch is connected to the second series branch.

[0023] For example, in some embodiments of the present application, the flexible direct current converter valve includes a two-level, three-level or multi-level three-phase bridge inverter circuit, wherein:

[0024] The three-phase bridge inverter circuit includes a fully controlled power electronic device.

[0025] For example, in some embodiments of the present application, the DC unit includes a pseudo bipolar system DC unit or a true bipolar system DC unit.

[0026] For example, in some embodiments of the present application, the DC line includes an overhead line or a cable.

[0027] For example, in some embodiments of the present application, the hydrogen production unit includes a hydrogen production electrolyzer, a transformer and an AC line, wherein:

[0028] The hydrogen production electrolyzer is connected to the AC side of the receiving-end flexible DC converter through the transformer and the AC line.

[0029] For example, in some embodiments of the present application, the DC energy storage unit includes an energy storage element, a converter valve, a reactor, a starting circuit and a switch device, wherein:

[0030] After being connected in parallel with the converter valve, the energy storage element is connected in series with the starting circuit, the reactor and the switch device.

[0031] For example, in some embodiments of the present application, the energy storage element includes a battery energy storage element or a supercapacitor energy storage element.

[0032] For example, in some embodiments of the present application, the converter valve includes a DC conversion circuit, wherein:

[0033] The DC conversion circuit includes a fully controlled power electronic device.

[0034] Through the above exemplary embodiments, the present application provides an off-grid new energy hydrogen production system based on flexible direct current transmission, which realizes power balance between new energy and hydrogen production unit by connecting a DC energy storage device in parallel to the DC line, and maintains system stability, reduces the commutation link, and reduces system cost. In addition, the new energy and hydrogen production unit do not need to be connected to the power grid, which can achieve true green and low-carbon.

[0035] 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

[0036] 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.

[0037] Figure 1 A schematic diagram of an off-grid new energy hydrogen production system based on flexible direct current transmission is shown according to an exemplary embodiment;

[0038] Figure 2 Another embodiment of an exemplary off-grid new energy hydrogen production system based on flexible direct current transmission is shown;

[0039] Figure 3 Another embodiment of an exemplary off-grid new energy hydrogen production system based on flexible direct current transmission is shown;

[0040] Figure 4 Another embodiment of an exemplary off-grid new energy hydrogen production system based on flexible direct current transmission is shown;

[0041] Figure 5 Another embodiment of an exemplary off-grid new energy hydrogen production system based on flexible direct current transmission is shown;

[0042] Figure 6 Another embodiment of an exemplary off-grid new energy hydrogen production system based on flexible direct current transmission is shown;

[0043] Figure 7 A schematic diagram of a sending-end flexible DC converter is shown according to an exemplary embodiment;

[0044] Figure 8 A schematic diagram of a DC energy storage device according to an exemplary embodiment is shown. DETAILED DESCRIPTION

[0045] 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.

[0046] 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.

[0047] 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.

[0048] 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.

[0049] 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.

[0050] Figure 1 A schematic diagram of an off-grid new energy hydrogen production system based on flexible direct current transmission is shown according to an exemplary embodiment.

[0051] like Figure 1 As shown, the off-grid new energy hydrogen production system based on flexible direct current transmission includes a direct current energy storage unit 15, a new energy power generation unit 101, a sending-end flexible direct current converter 6, a direct current unit 102, a receiving-end flexible direct current converter 10 and a hydrogen production unit 103.

[0052] According to the exemplary embodiment, the new energy power generation unit 101, the sending-end flexible DC converter 6, the DC unit 102, the receiving-end flexible DC converter 10 and the hydrogen production unit 103 are sequentially connected in series.

[0053] According to some embodiments, the DC unit 102 includes a sending-end DC bus 7, a DC line 8 and a receiving-end DC bus 9, and the sending-end DC bus 7 and the receiving-end DC bus 9 are connected through the DC line 8 to transmit active power from the sending end to the receiving end.

[0054] According to the exemplary embodiment, the new energy power generation unit 101 collects electric energy to the sending-end flexible direct current converter 6. The sending-end flexible direct current converter 6 is used to convert the electric energy and then connect it to the sending-end direct current bus 7.

[0055] According to the exemplary embodiment, the hydrogen production unit 103 collects the electric energy to the receiving-end flexible DC converter 10. The receiving-end flexible DC converter 10 is used to convert the electric energy and then connect it to the receiving-end DC bus 9.

[0056] According to the exemplary embodiment, the DC energy storage unit 15 is connected in parallel between the sending-end DC bus 7 and the DC line 8 to maintain the DC voltage stability and power balance of the off-grid new energy hydrogen production system.

[0057] According to some embodiments, the DC energy storage unit 15 can also be connected in parallel between the receiving end DC bus 9 and the DC line 8 to maintain the DC voltage stability and power balance of the off-grid new energy hydrogen production system, such as Figure 6 This application is only taken as an example, but the application is not limited to this.

[0058] According to some embodiments, the DC energy storage device 15 includes an energy storage element 1501, a converter valve 1502, a reactor 1503, a starting circuit 1504, and a switch device 1505. The energy storage element includes a battery energy storage element or a supercapacitor energy storage element. The converter valve includes a DC conversion circuit composed of fully controlled power electronic devices. The fully controlled power electronic device may include a submodule. The converter valve may use a half-bridge submodule or a full-bridge submodule. The DC energy storage device 15 is connected in series to the DC bus 8 through a plurality of submodules to maintain the stability of the DC voltage and play a role of "peak shaving and valley filling".

[0059] According to some embodiments, the energy storage element 1501 is connected in parallel with the converter valve 1502, and then connected in series with the start-up circuit 1504, the reactor 1503 and the switch device 1505. Figure 8 shown.

[0060] The sending-end flexible DC converter is used to control the voltage and frequency of the power grid where the new energy power generation unit is located so that the power grid can operate independently. The receiving-end flexible DC converter is used to control the voltage and frequency of the power grid where the hydrogen production unit is located so that the power grid can operate independently. The DC energy storage device is used to control the DC voltage to achieve DC voltage stability in the off-grid new energy hydrogen production system. And when there is a power deviation between the power grid where the new energy power generation unit is located and the power grid where the hydrogen production unit is located, the DC energy storage device is also used to consume the power deviation on both sides to achieve power balance.

[0061] According to some embodiments, the sending-end flexible direct current converter 6 includes a flexible direct current converter valve 601, a transformer 602, a bridge arm reactor 603, a starting circuit 604 and a switch device 605. The flexible direct current converter valve includes a two-level, three-level or multi-level 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 two-level converter, a three-level converter or a modular multi-level converter.

[0062] According to some embodiments, the transformer 602 and the switch device 605 are connected in series to form a first 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 second series branch. The first series branch is connected to the second series branch. Figure 7 shown.

[0063] According to some embodiments, the receiving-end flexible DC converter 10 includes a flexible DC converter valve, a transformer, a bridge arm reactor, a starting circuit and a switching device.

[0064] According to some embodiments, the DC cell 102 includes a pseudo bipolar system DC cell or a true bipolar system DC cell.

[0065] In the pseudo bipolar system DC unit, 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.

[0066] In a true bipolar system DC unit, the DC unit 102 needs to add a metal return busbar and a metal 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 flexible direct current transmission.

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

[0068] The present application provides an off-grid new energy hydrogen production system based on flexible direct current transmission. By connecting a DC energy storage device in parallel to the DC line, the DC energy storage device achieves power balance between the new energy and the hydrogen production unit, maintains system stability, reduces the commutation link, and reduces system costs. In addition, the new energy and the hydrogen production unit do not need to be connected to the power grid, which can achieve true green and low-carbon.

[0069] Figure 2 Another exemplary embodiment of an off-grid new energy hydrogen production system based on flexible direct current transmission is shown.

[0070] like Figure 2 As shown, the new energy power generation unit 101 includes a power generation device 1011, an AC line 4, a transformer 3 and a transformer 5. The power generation device 1011 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 sending-end flexible DC converter 6.

[0071] According to an exemplary embodiment, the power generation device 1011 includes at least one of a wind power generation device and a photovoltaic power generation device. The power generation device 1011 includes a wind power generation device 2 and a photovoltaic power generation device 1, such as Figure 2 As shown; the power generation device 1011 only includes a wind power generation device 2, such as Figure 3 As shown; the power generation device 1011 only includes a photovoltaic power generation device 1, such as Figure 4 shown.

[0072] According to some embodiments, the hydrogen production unit 103 includes a hydrogen production electrolyzer 14, a transformer 13, a transformer 11, and an AC line 12. The hydrogen production electrolyzer 14 is connected in series with the transformer 13, the AC line 12, and the transformer 11, and then connected to the AC side of the receiving-end flexible DC converter 10.

[0073] According to some embodiments, the wind power generation device 1 , the photovoltaic power generation device 2 , and the hydrogen production electrolyzer 104 each include at least two working units.

[0074] 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.

[0075] 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.

[0076] 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 flexible direct current transmission, characterized in that: The off-grid new energy hydrogen production system includes a DC energy storage unit, a new energy power generation unit, a sending-end flexible DC converter, a DC unit, a receiving-end flexible DC converter and a hydrogen production unit, wherein: The DC unit includes a sending-end DC bus, a DC line and a receiving-end DC bus; The new energy power generation unit collects electric energy to the sending-end flexible DC converter, and the sending-end flexible DC converter is used to convert the electric energy and then connect it to the sending-end DC bus; The hydrogen production unit collects electric energy to the receiving-end flexible DC converter, and the receiving-end flexible DC converter is used to convert the electric energy and then connect it to the receiving-end DC bus; The sending-end DC busbar is connected to the receiving-end DC busbar through the DC line to transmit active power from the sending end to the receiving end; The DC energy storage unit is connected in parallel between the sending-end DC bus and the DC line or between the receiving-end DC bus and the DC line to maintain DC voltage stability and power balance of the off-grid new energy hydrogen production system.

2. The off-grid new energy hydrogen production system according to claim 1, characterized in that: The new energy power generation unit includes a power generation device, an AC line and a transformer, wherein: The power generation device includes at least one of a wind power generation device and a photovoltaic power generation device; The power generation device is connected to the AC side of the sending-end flexible DC 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 sending-end flexible DC converter and the receiving-end flexible DC converter both include a flexible DC converter valve, a transformer, a bridge arm reactor, a starting circuit and a switch device, wherein: The transformer and the switch device are connected in series to form a first series branch; The bridge arm reactor, the flexible DC converter valve and the starting circuit are connected in series to form a second series branch; The first series branch is connected to the second series branch.

4. The off-grid new energy hydrogen production system according to claim 3, characterized in that: The flexible direct current converter valve comprises a two-level, three-level or multi-level three-phase bridge inverter circuit, wherein: The three-phase bridge inverter circuit includes a fully controlled power electronic device.

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

6. 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.

7. The off-grid new energy hydrogen production system according to claim 1, characterized in that: The hydrogen production unit comprises a hydrogen production electrolyzer, a transformer and an AC line, wherein: The hydrogen production electrolyzer is connected to the AC side of the receiving-end flexible DC converter through the transformer and the AC line.

8. The off-grid new energy hydrogen production system according to claim 1, characterized in that: The DC energy storage unit includes an energy storage element, a converter valve, a reactor, a starting circuit and a switch device, wherein: After being connected in parallel with the converter valve, the energy storage element is connected in series with the starting circuit, the reactor and the switch device.

9. The off-grid new energy hydrogen production system according to claim 8, characterized in that: The energy storage element includes a battery energy storage element or a supercapacitor energy storage element.

10. The off-grid new energy hydrogen production system according to claim 8, characterized in that: The converter valve includes a DC conversion circuit, wherein: The DC conversion circuit includes a fully controlled power electronic device.

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