Offshore energy island power supply system and working method thereof

Abstract

The invention discloses an offshore energy island power supply system and a working method thereof, and the system comprises an offshore wind power flexible DC sending-out device which is used for transmitting the offshore wind power to an onshore power grid through a submarine cable; the on-island hydrogen production ammonia alcohol power supply device comprises a direct current power supply device and an alternating current power supply device, and the direct current power supply device comprises an energy storage type MMC converter, a direct current side capacity type energy storage device, a direct current side power type energy storage device, a direct current side PEM electrolytic cell, a direct current side alkaline electrolytic cell, a distributed photovoltaic device, a distributed energy storage device and a hydrogen production device which are connected with a direct current bus. The alternating-current power supply device comprises an alternating-current side alkaline electrolytic cell, an alternating-current side PEM electrolytic cell and an alternating-current side capacity type energy storage and ammonia alcohol preparation device which are respectively connected with an alternating-current bus; the on-island hydrogen production ammonia alcohol power supply device is used for carrying out hydrogen production ammonia alcohol operation through offshore wind power and photovoltaic power. According to the embodiment, the utilization rate of offshore wind power is increased, the power supply efficiency is improved, and the service life of energy storage equipment is prolonged.

Description

Technical Field

[0001] The present invention relates to the technical field of energy utilization, and particularly to an offshore energy island power supply system and its working method. Background Art

[0002] This section aims to provide background or context for the embodiments of the present invention described. The descriptions herein are not admitted to be prior art merely by virtue of being included in this section.

[0003] In the current energy environment, COSCO Shipping Wind Power is an important resource to be developed. However, there are many problems in the traditional grid-connected development mode of offshore wind power, such as the isolated operation of the industry, large power fluctuations in deep-sea and far-sea wind power resources, difficult consumption, and low utilization rate, resulting in a large amount of offshore wind power that cannot be fully developed and utilized. Establishing an offshore energy island can create an island-type energy system with multi-format integration, improve the autonomous capabilities of wind power collection, energy storage, and green hydrogen and alcohol production, stabilize the operation of deep-sea and far-sea offshore wind power bases, and can also utilize surrounding photovoltaic resources to reduce the demand for onshore power grids. However, currently, offshore wind power is directly grid-connected, and there are deficiencies in the research on AC-DC hybrid power supply methods, energy storage configuration, power coordination control, etc. in the existing technologies. For example, the power supply schemes of wind-solar power generation and hydrogen production systems mostly adopt AC grid connection. For the application scenarios of offshore energy islands, problems such as direct grid connection of wind power, partial interconnection of AC and DC, energy storage configuration, and coordination control have not been deeply studied, which affects the development of offshore wind power energy islands.

[0004] Specifically, the fluctuations of offshore wind power are large, the utilization rate of the offshore wind-soft DC system is low, and it is difficult to consume. The traditional grid connection mode cannot effectively handle the fluctuating energy; the new energy hydrogen production adopts a unified AC power supply form. For the PV, energy storage, and hydrogen production at the DC port, an AC link needs to be added, which affects the efficiency; the new energy off-grid hydrogen production only adopts capacitive electrochemical energy storage, and its frequent charging and discharging in response to new energy fluctuations will affect the service life. For the AC-DC interconnected system, there is a lack of a reasonable energy coordination control strategy that comprehensively considers the energy storage type and the characteristics of the hydrogen production electrolyzer, and the energy utilization rate of the system is low. Summary of the Invention

[0005] Embodiments of the present invention provide an offshore energy island power supply system to improve the utilization rate of offshore wind power, increase the power supply efficiency through an AC-DC hybrid power supply method, extend the service life of energy storage devices, and reduce the maintenance cost. The offshore energy island power supply system includes:

[0006] An offshore wind power flexible DC transmission device for transmitting offshore wind power through a submarine cable to an onshore power grid;

[0007] Island hydrogen production, ammonia production, and power supply device, including a DC power supply device and an AC power supply device, where: The DC power supply device includes an energy storage type MMC converter, a DC side capacitive energy storage, a DC side power type energy storage, a DC side PEM electrolyzer, a DC side alkaline electrolyzer, distributed photovoltaic, distributed energy storage, and a hydrogen production device, which are respectively connected to the DC bus; the energy storage type MMC converter is used to balance the power difference between wind power and load during the increase of wind power; The AC power supply device includes an AC side alkaline electrolyzer, an AC side PEM electrolyzer, an AC side capacitive energy storage, and an ammonia and alcohol production device, which are respectively connected to the AC bus; The island hydrogen production, ammonia production, and power supply device is used to perform hydrogen production, ammonia production, and alcohol production operations through offshore wind power and photovoltaic power transmitted by distributed photovoltaic and distributed energy storage.

[0008] An embodiment of the present invention also provides a working method for a power supply system of an offshore energy island, which is used to improve the utilization rate of offshore wind power, improve the power supply efficiency through an AC-DC hybrid power supply method, extend the service life of energy storage equipment, and reduce maintenance costs. The method includes:

[0009] Real-time detection of the wind power of wind power and the photovoltaic power of the photovoltaic power transmitted by distributed photovoltaic in the DC power supply device;

[0010] When it is detected that the growth data of wind power exceeds the first preset value, increase the power of different devices in the island hydrogen production, ammonia production, and power supply device in the first preset order;

[0011] When it is detected that the decrease data of wind power exceeds the second preset value, decrease the power of different devices in the island hydrogen production, ammonia production, and power supply device in the first preset order;

[0012] When it is detected that the growth data of photovoltaic power exceeds the third preset value, increase the power of different devices in the island hydrogen production, ammonia production, and power supply device in the second preset order;

[0013] When it is detected that the decrease data of photovoltaic power exceeds the fourth preset value, decrease the power of different devices in the island hydrogen production, ammonia production, and power supply device in the second preset order.

[0014] An embodiment of the present invention provides an offshore energy island power supply system, comprising: an offshore wind power flexible DC transmission device, used to transmit offshore wind power to an onshore power grid through a submarine cable; an island hydrogen ammonia alcohol power supply device, including a DC power supply device and an AC power supply device, wherein: the DC power supply device includes an energy storage type MMC converter, a DC side capacity type energy storage, a DC side power type energy storage, a DC side PEM electrolyzer, a DC side alkaline electrolyzer, distributed photovoltaic, distributed energy storage and a hydrogen production device, which are respectively connected to the DC bus; the energy storage type MMC converter is used to balance the power difference between wind power and load during the increase of wind power; the AC power supply device includes an AC side alkaline electrolyzer, an AC side PEM electrolyzer, an AC side capacity type energy storage and an ammonia alcohol production device, which are respectively connected to the AC bus; the island hydrogen ammonia alcohol power supply device is used to perform hydrogen ammonia alcohol operations through the offshore wind power transmitted by the offshore wind power flexible DC transmission device and the distributed photovoltaic and distributed energy storage transmitted photovoltaic power. The embodiment of the present invention combines an offshore wind power flexible DC transmission device with an island hydrogen ammonia power supply device to use offshore wind power for hydrogen ammonia operations, which can effectively utilize fluctuating energy, change the situation of difficult absorption and low utilization rate caused by direct grid connection of traditional offshore wind power, solve the problem of large fluctuations in offshore wind power and low utilization rate of flexible DC system, and improve the utilization rate of offshore wind power; adopt an island hydrogen ammonia power supply system including a DC power supply device and an AC power supply device, and the photovoltaic, energy storage and hydrogen production parts of the DC port can be directly powered by DC, avoiding the disadvantage of traditional new energy hydrogen production using a unified AC power supply form and the need to add additional AC links, and adopts an AC / DC hybrid power supply method, and the DC power supply part is adapted to the photovoltaic, energy storage and hydrogen production parts of the DC port. The DC port equipment such as volts, energy storage and hydrogen production eliminates the AC conversion link and significantly improves the power supply efficiency. At the same time, energy can be exchanged between AC and DC, which effectively guarantees the power supply reliability. It is equipped with DC side capacity energy storage, DC side power energy storage and AC side capacity energy storage, and uses energy storage type MMC converter to balance the difference between wind power and load, which changes the traditional way of only using electrochemical energy storage to deal with new energy fluctuations. It adopts a combination of power energy storage and capacity energy storage, so that fast and frequent fluctuations are responded to by power energy storage, and long-term power changes are responded to by capacity energy storage, which effectively extends the use time of electrochemical energy storage and solves the problem of frequent charging and discharging affecting the service life of energy storage in the scenario of new energy power generation and hydrogen production. BRIEF DESCRIPTION OF THE DRAWINGS

[0015] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the following briefly introduces the drawings required for use in the embodiments or the prior art descriptions. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without creative work. In the drawings:

[0016] Figure 1 It is a schematic structural diagram of a power supply system for an offshore energy island in an embodiment of the present invention;

[0017] Figure 2 It is a specific example diagram of a power supply system for an offshore energy island in an embodiment of the present invention;

[0018] Figure 3 It is a flow example diagram of a working method of a power supply system for an offshore energy island in an embodiment of the present invention;

[0019] Figure 4 It is a specific example diagram of a working method of a power supply system for an offshore energy island in an embodiment of the present invention;

[0020] Figure 5 It is a specific example diagram of a working method of a power supply system for an offshore energy island in an embodiment of the present invention;

[0021] Figure 6 It is a specific example diagram of a working method of a power supply system for an offshore energy island in an embodiment of the present invention;

[0022] Figure 7 It is a specific example diagram of a working method of a power supply system for an offshore energy island in an embodiment of the present invention. Detailed implementation manners

[0023] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer and more understandable, the embodiments of the present invention will be further described in detail below with reference to the accompanying drawings. Here, the illustrative embodiments of the present invention and their descriptions are used to explain the present invention, but not to limit the present invention.

[0024] The term "and / or" in this article merely describes an associated relationship and indicates that there can be three relationships. For example, A and / or B can represent: A exists alone, A and B exist simultaneously, and B exists alone. In addition, the term "at least one" in this article means any one of multiple or any combination of at least two of multiple. For example, including at least one of A, B, and C can represent including any one or more elements selected from the set composed of A, B, and C.

[0025] In the description of this specification, terms such as "including", "comprising", "having", "containing", etc. are all open-ended terms, meaning including but not limited to. The description with reference to terms such as "one embodiment", "one specific embodiment", "some embodiments", "for example", etc. means that the specific features, structures or characteristics described in connection with the embodiment or example are included in at least one embodiment or example of the present application. In this specification, the schematic expressions of the above terms do not necessarily refer to the same embodiment or example. Moreover, the specific features, structures or characteristics described can be combined in a suitable manner in any one or more embodiments or examples. The order of steps involved in each embodiment is used to schematically illustrate the implementation of the present application, and the order of steps is not limited and can be adjusted appropriately as needed.

[0026] In the technical solution of the present application, the acquisition, storage, use, processing, etc. of data all comply with the relevant regulations of relevant laws and regulations. The information collected in the present application is information and data authorized by the user or fully authorized by all parties, and the processing of relevant data, such as collection, storage, use, processing, transmission, provision, disclosure and application, all comply with relevant laws and regulations and standards, take necessary confidentiality measures, do not violate public order and good customs, and provide corresponding operation entrances for users to choose to authorize or refuse.

[0027] It should be noted that in the embodiments of the present application, some industry-existing solutions such as certain software, components, models, etc. may be mentioned. For example, some existing software tools, components, algorithm models or other well-known solutions in other technical fields may be cited. They should be regarded as exemplary, and their purpose is only to illustrate the feasibility in the implementation of the technical solution of the present application. These mentions should be understood as typical examples, and their core purpose is to elaborate and verify the rationality and feasibility of the technical solution proposed by the present application. However, it does not mean that the applicant has already or necessarily used this solution. Such a citation does not imply that the applicant has actually adopted these existing solutions, or will necessarily adopt these methods in the process of implementing its technology in the future. In other words, these mentions are only for illustrative purposes, to help understand the association and superiority of the innovation point of the present application over the existing technology, and do not constitute an endorsement or reliance statement on specific existing technology products.

[0028] In the current energy environment, the offshore wind power of COSCO SHIPPING Wind Energy has become an important resource that urgently needs to be developed. However, the traditional industrial isolated operation mode of offshore wind power grid connection has problems such as large power fluctuations in deep-sea and far-sea wind resources, difficult power consumption, and low utilization rate, resulting in a large amount of offshore wind power that cannot be fully developed and utilized.

[0029] In combination with the above aspects, by establishing an offshore energy island with the characteristics of an offshore energy resource supply and conversion hub, we can create an island-type energy system that integrates multiple business formats, which can greatly enhance the autonomy of large-scale wind power collection, energy storage, and green electricity hydrogen production, and effectively enhance the stable operation capacity of large-scale deep-sea offshore wind power bases. At the same time, we can utilize the surrounding photovoltaic resources, greatly reduce the demand and constraints on the onshore power grid capacity configuration, and provide a large amount of green hydrogen ammonia to achieve three-dimensional development of marine resources.

[0030] At present, offshore wind power is generally connected to the grid through flexible DC transmission. Due to the volatility of offshore wind power, it is difficult to absorb offshore wind, which seriously affects the progress of offshore wind development. At the same time, the power supply scheme of wind and solar power generation green hydrogen ammonia alcohol system generally adopts AC grid connection scheme. For the application scenario of offshore energy island, the existing technology has many problems:

[0031] First, offshore wind power is directly connected to the grid. Second, the offshore integrated energy island brings together renewable energy sources such as offshore wind power and photovoltaics. Wind power is more suitable for AC collection, while photovoltaics, energy storage, and hydrogen production are all in DC form. Using DC power supply can eliminate the AC / DC conversion link, improve efficiency, and reduce size.

[0032] Therefore, the traditional all-AC power supply method is no longer suitable, and the AC / DC hybrid method is more suitable for offshore energy islands.

[0033] There has been no in-depth research on the AC / DC hybrid power supply mode, how to interconnect the AC / DC parts, how to configure energy storage, what form of energy storage is more suitable for renewable energy power generation and hydrogen production scenarios, how to coordinate power control of different sources, loads, storage and DC grid-connected parts when renewable energy fluctuates, etc. For the deep sea energy island power supply system, the above problems need to be solved urgently.

[0034] In order to solve the above technical problems, an embodiment of the present invention provides an offshore energy island power supply system to improve the utilization rate of offshore wind power, improve power supply efficiency through AC / DC hybrid power supply, extend the service life of energy storage equipment, and reduce maintenance costs. Figure 1 The structure diagram of an offshore energy island power supply system in an embodiment of the present invention is shown, and the offshore energy island power supply system includes:

[0035] Offshore wind power flexible DC transmission device, used to transmit offshore wind power to the onshore power grid through submarine cables;

[0036] Island hydrogen production, ammonia production, and power supply device, including a DC power supply device and an AC power supply device, where: The DC power supply device includes an energy storage type MMC converter, a DC side capacitive energy storage, a DC side power type energy storage, a DC side PEM electrolyzer, a DC side alkaline electrolyzer, distributed photovoltaic, distributed energy storage, and a hydrogen production device, which are respectively connected to the DC bus; The energy storage type MMC converter is used to balance the power difference between wind power and load during the increase of wind power; The AC power supply device includes an AC side alkaline electrolyzer, an AC side PEM electrolyzer, an AC side capacitive energy storage, and an ammonia and alcohol production device, which are respectively connected to the AC bus; The island hydrogen production, ammonia production, and power supply device is used to perform hydrogen production, ammonia production, and alcohol production operations through the offshore wind power transmitted by the offshore wind power flexible DC transmission device, distributed photovoltaic, and photovoltaic power transmitted by distributed energy storage.

[0037] In the embodiment of the present invention, by combining the offshore wind power flexible DC transmission device with the island hydrogen production, ammonia production, and power supply device, and using the offshore wind power for hydrogen production, ammonia production, and alcohol production operations, the fluctuating energy can be effectively utilized, changing the situation of difficult consumption and low utilization rate caused by the traditional direct grid connection of offshore wind power, solving the problems of large fluctuations in offshore wind power and low utilization rate of the flexible DC system, and improving the utilization rate of offshore wind power; The island hydrogen production, ammonia production, and power supply system including a DC power supply device and an AC power supply device can directly utilize DC power for the photovoltaic, energy storage, and hydrogen production parts of the DC port, avoiding the disadvantages of the traditional new energy hydrogen production using a unified AC power supply form and requiring additional AC links. Adopting an AC-DC hybrid power supply method, the DC power supply part is adapted to DC port devices such as photovoltaic, energy storage, and hydrogen production, eliminating the AC conversion link, significantly improving the power supply efficiency, and at the same time, energy can be interchanged between AC and DC, effectively ensuring the power supply reliability; Capacitive energy storage on the DC side, power type energy storage on the DC side, and capacitive energy storage on the AC side are configured, and the energy storage type MMC converter is used to balance the difference between wind power and load, changing the traditional method of only using electrochemical energy storage to cope with new energy fluctuations. Adopting a combination of power type energy storage and capacitive energy storage, the fast and frequent fluctuations are responded by the power type energy storage, and the long-term power changes are responded by the capacitive energy storage, effectively extending the service life of the electrochemical energy storage, and solving the problem of the influence of frequent charging and discharging on the service life of energy storage in the new energy power generation and hydrogen production scenario.

[0038] In the embodiment, the offshore wind power flexible DC transmission device undertakes the important responsibility of transmitting offshore wind power to the onshore power grid. Through the medium of submarine cables, it constructs a connection channel between offshore wind power and onshore energy utilization, enabling the rich offshore wind power resources to be effectively collected and transmitted to the onshore power grid, laying a foundation for subsequent energy conversion and utilization. The island hydrogen production, ammonia production, and power supply device is one of the core components of the entire system, and it is further divided into a DC power supply device and an AC power supply device.

[0039] Among them, the DC power supply device covers multiple key components such as an energy storage type MMC converter, a DC side capacitive energy storage, a DC side power type energy storage, a DC side PEM electrolyzer, a DC side alkaline electrolyzer, distributed photovoltaics, distributed energy storage, and a hydrogen production device, which are respectively connected to the DC bus. Among them, the DC bus, as an important carrier for power transmission, provides a stable path for power distribution and transmission among components. When the wind power increases, the energy storage type MMC converter can accurately balance the power difference between the wind power and the load, ensuring the stable operation of the system. Through its internal control mechanism and energy storage unit, it effectively regulates the input and output of electric energy, avoiding system overload or instability caused by sudden increases in wind power.

[0040] The DC side capacitive energy storage and the DC side power type energy storage cooperate with each other to perform energy storage and energy release operations according to different power fluctuation characteristics and time scales. The power type energy storage can quickly respond to the frequent small fluctuations of wind power and use its fast charge and discharge ability to adjust the system power balance in a short time; while the capacitive energy storage focuses on dealing with long-term power changes and provides stable electric energy storage and release in the case of continuous changes in wind power or large fluctuations in other energy inputs, ensuring continuous and stable power supply of the system. The DC side PEM electrolyzer and the DC side alkaline electrolyzer are key devices for converting electric energy into hydrogen energy. They use the electric energy provided by the DC power supply device to decompose water into hydrogen and oxygen, providing raw materials for ammonia and alcohol production. Distributed photovoltaics make full use of the solar energy resources on the island, convert solar energy into electric energy and input it into the DC power supply system, increasing the diversity and supply stability of energy. Distributed energy storage further enhances the energy storage capacity and flexibility of electric energy regulation of the system. When the energy supply is excessive or insufficient, it can effectively store or release electric energy, optimizing the energy management of the system.

[0041] The AC power supply device includes an AC side alkaline electrolyzer, an AC side PEM electrolyzer, an AC side capacitive energy storage, and an ammonia and alcohol production device, which are respectively connected to the AC bus. The AC bus also serves as a key path for power transmission, connecting each AC power supply device. The AC side alkaline electrolyzer and the AC side PEM electrolyzer use AC electric energy for chemical reactions during the production of hydrogen, ammonia, and alcohol, converting electric energy into chemical energy and participating in the production process of hydrogen, ammonia, and alcohol. The AC side capacitive energy storage can be used to balance the power fluctuations on the AC side and provide stable electric energy support when the AC load changes or other energy inputs are unstable, ensuring the reliability of AC power supply. The ammonia and alcohol production device uses electric energy and raw materials such as hydrogen generated during the hydrogen production process to synthesize important chemical products such as ammonia and alcohol through a series of chemical reactions, realizing the deep conversion and comprehensive utilization of energy.

[0042] Overall, the hydrogen, ammonia, and alcohol power supply device on the island realizes the collaborative utilization and efficient conversion of multiple energy sources by integrating the offshore wind power transmitted by the flexible DC transmission device of offshore wind power, distributed photovoltaic power, and photovoltaic power transmitted by distributed energy storage. It converts electrical energy into energy products with important application values such as hydrogen, ammonia, and alcohols, providing strong support for the energy self-sufficiency and sustainable development of the offshore energy island.

[0043] In one embodiment, the AC bus includes: a high-voltage AC bus and a medium-voltage AC bus; the DC bus includes a medium-voltage DC bus and a low-voltage DC bus; the system further includes: an AC-DC conversion device configured between the low-voltage DC bus and the medium-voltage AC bus for providing two power supply sources. The two power sources provide power supplies from two different sources to ensure that there is a backup power supply in case one power supply fails.

[0044] In one embodiment, the low-voltage DC bus is interconnected by a bus switch or forms a ring network.

[0045] In the above embodiment, in the architecture design of the offshore energy island power supply system, the AC bus is divided into a high-voltage AC bus and a medium-voltage AC bus according to the voltage level. The high-voltage AC bus mainly undertakes the tasks of transmitting and distributing electrical energy with large capacity and high voltage level in the system. It can stably transmit electrical energy to large electrical equipment or power distribution nodes with high voltage requirements, ensuring the normal operation of these key equipment. The medium-voltage AC bus, on the one hand, receives the electrical energy distribution from the high-voltage AC bus, and on the other hand, supplies electrical energy to some medium-voltage electrical equipment and other components of the AC power supply device, ensuring the coherence and stability of the AC power supply network.

[0046] The DC bus includes a medium-voltage DC bus and a low-voltage DC bus. The medium-voltage DC bus is in a key position in the DC power supply device. It is responsible for collecting the DC electrical energy from equipment such as offshore wind power, distributed photovoltaic power, and energy storage type MMC converters, and distributing it to various electrical equipment and energy storage devices on the DC side. Its relatively high voltage level helps to reduce the loss during the electrical energy transmission process, improve the electrical energy transmission efficiency, and ensure the stable operation of the DC power supply system. The low-voltage DC bus mainly provides electrical energy support for some DC equipment with lower voltage requirements, such as some distributed energy storage devices and small DC electrical equipment. At the same time, the low-voltage DC bus and the medium-voltage DC bus cooperate with each other to form a complete DC power supply network, ensuring the reasonable distribution and efficient utilization of DC electrical energy in the system.

[0047] The AC-DC conversion device is configured between the low-voltage DC bus and the medium-voltage AC bus. This device can achieve the mutual conversion of DC and AC electrical energy, providing two power supply sources for important loads. During actual operation, when the AC power supply system fails or the power quality is unstable, the AC-DC conversion device can convert the DC electrical energy on the low-voltage DC bus into AC electrical energy to continuously supply power to important loads, ensuring their normal operation is not affected. Conversely, when the DC power supply system faces similar problems, it can also convert the AC electrical energy on the medium-voltage AC bus into DC electrical energy to provide backup power for important equipment that relies on DC power supply. In this way, the AC-DC conversion device greatly improves the power supply reliability of important loads, enhances the ability of the entire power supply system to cope with sudden failures, and ensures that the key equipment and production processes of the offshore energy island can operate continuously and stably.

[0048] Regarding the connection method of the low-voltage DC bus, the bus switch interconnection or the formation of a ring network is adopted. The bus tie switch connection method enables the low-voltage DC bus to achieve zonal power supply during normal operation. Each zone can operate independently without interference, improving the operation flexibility and maintainability of the system. When a fault occurs in a certain zone or equipment maintenance is required, the bus tie switch can be operated to isolate the faulty zone and ensure the normal power supply of other zones, avoiding the paralysis of the entire low-voltage DC power supply system due to local faults. The method of forming a ring network further enhances the power supply reliability of the low-voltage DC bus. In the ring network structure, electrical energy can flow to the load from multiple directions. When a certain line fails, the electrical energy can be automatically switched to other paths to achieve uninterrupted power supply, effectively improving the fault tolerance and power supply stability of the system, providing a solid guarantee for the stable operation of the offshore energy island.

[0049] An embodiment of the present invention provides an offshore energy island power supply system, comprising: an offshore wind power flexible DC transmission device, used to transmit offshore wind power to an onshore power grid through a submarine cable; an island hydrogen ammonia alcohol power supply device, including a DC power supply device and an AC power supply device, wherein: the DC power supply device includes an energy storage type MMC converter, a DC side capacity type energy storage, a DC side power type energy storage, a DC side PEM electrolyzer, a DC side alkaline electrolyzer, distributed photovoltaic, distributed energy storage and a hydrogen production device, which are respectively connected to the DC bus; the energy storage type MMC converter is used to balance the power difference between wind power and load during the increase of wind power; the AC power supply device includes an AC side alkaline electrolyzer, an AC side PEM electrolyzer, an AC side capacity type energy storage and an ammonia alcohol production device, which are respectively connected to the AC bus; the island hydrogen ammonia alcohol power supply device is used to perform hydrogen ammonia alcohol operations through offshore wind power and distributed photovoltaics and photovoltaic power transmitted by distributed energy storage. The embodiment of the present invention combines an offshore wind power flexible DC transmission device with an island hydrogen ammonia power supply device to use offshore wind power for hydrogen ammonia operations, which can effectively utilize fluctuating energy, change the situation of difficult absorption and low utilization rate caused by direct grid connection of traditional offshore wind power, solve the problem of large fluctuations in offshore wind power and low utilization rate of flexible DC system, and improve the utilization rate of offshore wind power; adopt an island hydrogen ammonia power supply system including a DC power supply device and an AC power supply device, and the photovoltaic, energy storage and hydrogen production parts of the DC port can be directly powered by DC, avoiding the disadvantage of traditional new energy hydrogen production using a unified AC power supply form and the need to add additional AC links, and adopts an AC / DC hybrid power supply method, and the DC power supply part is adapted to the photovoltaic, energy storage and hydrogen production parts of the DC port. The DC port equipment such as volts, energy storage and hydrogen production eliminates the AC conversion link and significantly improves the power supply efficiency. At the same time, energy can be exchanged between AC and DC, which effectively guarantees the power supply reliability. It is equipped with DC side capacity energy storage, DC side power energy storage and AC side capacity energy storage, and uses energy storage type MMC converter to balance the difference between wind power and load, which changes the traditional way of only using electrochemical energy storage to deal with new energy fluctuations. It adopts a combination of power energy storage and capacity energy storage, so that fast and frequent fluctuations are responded to by power energy storage, and long-term power changes are responded to by capacity energy storage, which effectively extends the use time of electrochemical energy storage and solves the problem of frequent charging and discharging affecting the service life of energy storage in the scenario of new energy power generation and hydrogen production.

[0050] The embodiment of the present invention also provides a working method of an offshore energy island power supply system, which is used to improve the utilization rate of offshore wind power, improve power supply efficiency through AC / DC hybrid power supply, extend the service life of energy storage equipment, and reduce maintenance costs. Figure 3 The flowchart of a working method of an offshore energy island power supply system in an embodiment of the present invention is shown, and the method includes:

[0051] Step 301: Real-time detect the wind power of offshore wind power and the photovoltaic power of photovoltaic power transmitted by distributed photovoltaics in the DC power supply device;

[0052] Step 302: When it is determined through detection that the growth data of the wind power exceeds the first preset value, increase the power of different devices in the hydrogen production, ammonia synthesis and alcohol power supply device on the island in the first preset order;

[0053] Step 303: When it is determined through detection that the decrease data of the wind power exceeds the second preset value, decrease the power of different devices in the hydrogen production, ammonia synthesis and alcohol power supply device on the island in the first preset order;

[0054] Step 304: When it is determined through detection that the growth data of the photovoltaic power exceeds the third preset value, increase the power of different devices in the hydrogen production, ammonia synthesis and alcohol power supply device on the island in the second preset order;

[0055] Step 305: When it is determined through detection that the decrease data of the photovoltaic power exceeds the fourth preset value, decrease the power of different devices in the hydrogen production, ammonia synthesis and alcohol power supply device on the island in the second preset order.

[0056] In the embodiments of the present invention, by accurately monitoring the real-time wind power and adjusting the power of each device in the hydrogen production, ammonia production, and methanol production power supply device on the island in an orderly manner according to its increase or decrease, the fluctuating wind power energy can be effectively and reasonably allocated and converted. For example, when the wind power increases, the excess electric energy is preferentially used for operations such as hydrogen production, ammonia production, and methanol production, avoiding energy waste caused by the inability to consume it, greatly increasing the utilization ratio of offshore wind power in the entire energy system, enabling the offshore wind power, which was originally difficult to fully utilize due to large fluctuations, to be stably integrated into the energy supply system, and enhancing the stability and reliability of the energy supply. By adopting an AC-DC hybrid power supply mode, during the power regulation process, according to the energy source (wind power or photovoltaic) and the characteristics of each device on the DC or AC side, the power of each device in the DC power supply device and the AC power supply device is adjusted in an orderly manner. For example, when the photovoltaic power changes, the power of the relevant electrolyzers on the DC side is preferentially adjusted, reducing unnecessary AC-DC conversion links, reducing energy losses, ensuring that electric energy can be efficiently transmitted and utilized in the system, improving the overall power supply efficiency, and enabling the energy to more accurately meet the various load demands. During the process of coping with power fluctuations, the power-type energy storage and the capacity-type energy storage cooperate according to their different characteristics. For fast and frequent power fluctuations, the power-type energy storage responds quickly, avoiding battery life loss caused by frequent small-scale charging and discharging of the capacity-type energy storage; while for long-term power changes, the capacity-type energy storage undertakes the regulation task, preventing the power-type energy storage from being over-fatigued due to long-term continuous operation. This reasonable regulation mechanism significantly reduces the number of ineffective charge and discharge times and the deep charge and discharge cycles of the energy storage device, effectively extending the overall service life of the energy storage device, and reducing the economic cost and maintenance workload brought by frequent replacement of the energy storage device. Due to the extension of the service life of the energy storage device, the equipment replacement frequency and related maintenance work are reduced, directly reducing the equipment procurement and maintenance costs. Through an efficient energy coordination control strategy, the stability of the system operation is enhanced, the risk of equipment failure caused by power fluctuations is reduced, and the cost of troubleshooting and repair is reduced, comprehensively reducing the long-term maintenance cost of the offshore energy island power supply system from multiple aspects and improving the economic efficiency and operation stability of the system.

[0057] During specific implementation, the wind power of the offshore wind power and the photovoltaic power of the distributed photovoltaic power transmitted in the DC power supply device are detected in real time.

[0058] In the embodiment, during the operation of the offshore energy island power supply system, an important link for the effective management and stable supply of energy is the accurate monitoring of the power. Among them, a special real-time detection mechanism is set for the wind power of the offshore wind power soft power and the photovoltaic power of the distributed photovoltaic power transmitted in the DC power supply device.

[0059] For offshore wind power detection, the detection system is closely connected to the key nodes of the wind power transmission line through a series of high-precision sensors and data acquisition equipment. These sensors can keenly perceive the real-time changes of wind power during transmission and quickly convert the acquired analog signals into digital signals for subsequent data processing and analysis.

[0060] In the distributed photovoltaic aspect of the DC power supply device, a rigorous photovoltaic power detection system is also deployed. Highly sensitive photovoltaic power sensors are installed at various key locations of the distributed photovoltaic array. These sensors can accurately measure the power generated by each photovoltaic module or photovoltaic sub-array, and aggregate these local power data to the distributed photovoltaic power centralized monitoring device.

[0061] In one embodiment, the first preset order is the order of AC side PEM electrolyzer, AC side alkaline electrolyzer, DC side PEM electrolyzer, DC side alkaline electrolyzer, AC side capacity-type energy storage, and DC side capacity-type energy storage; the second preset order is the order of DC side PEM electrolyzer, DC side alkaline electrolyzer, AC side PEM electrolyzer, AC side alkaline electrolyzer, DC side capacity-type energy storage, and AC side capacity-type energy storage.

[0062] In this embodiment, when the system faces changes in wind power, the first preset order followed is the AC-side PEM electrolyzer, the AC-side alkaline electrolyzer, the DC-side PEM electrolyzer, the DC-side alkaline electrolyzer, the AC-side capacitive energy storage, and the DC-side capacitive energy storage. When the wind power increases, the AC-side PEM electrolyzer is considered first. This electrolyzer has a certain degree of power regulation flexibility and can quickly increase the consumption of electrical energy to a certain extent to respond to the increase in wind power. If the AC-side PEM electrolyzer has reached its power regulation upper limit and cannot further increase the load, the AC-side alkaline electrolyzer is then started for power regulation. The AC-side alkaline electrolyzer also undertakes an important power regulation task in the system. It can use its own chemical characteristics to adjust the absorption of electrical energy within a large range, thereby balancing the increase in wind power. When the adjustment means on the AC side have been fully utilized but still cannot completely absorb the increased wind power, the adjustment focus is shifted to the DC side. At this time, the DC-side PEM electrolyzer takes the lead in participating in the adjustment and uses its high-efficiency electrical energy conversion ability in the DC power supply environment to further consume the excess wind power. If the DC-side PEM electrolyzer reaches the adjustment limit, the DC-side alkaline electrolyzer continues to undertake the adjustment task. After the adjustment of the above electrolyzers, if there is still remaining wind power, the AC-side capacitive energy storage is used to store electrical energy to smooth out the power fluctuations. When the AC-side capacitive energy storage approaches or reaches the storage upper limit, the DC-side capacitive energy storage is then used to absorb and store the remaining electrical energy. Through such sequential adjustment, the system can orderly respond to the increase in wind power, ensure the reasonable distribution and utilization of electrical energy among different devices and energy storage units, and maintain the stable operation of the system.

[0063] When the system encounters changes in photovoltaic power, the second preset order adopted is the DC-side PEM electrolyzer, the DC-side alkaline electrolyzer, the AC-side PEM electrolyzer, the AC-side alkaline electrolyzer, the DC-side capacitive energy storage, and the AC-side capacitive energy storage. Since photovoltaic power sources are usually connected to DC power supply devices, when the photovoltaic power increases, the DC-side PEM electrolyzer first plays a role. Utilizing its adaptability in the DC environment, it quickly increases the conversion and utilization of photovoltaic electric energy to balance the power growth. When the DC-side PEM electrolyzer cannot fully absorb the increased photovoltaic power, the DC-side alkaline electrolyzer is immediately activated to participate in the regulation. If the regulation ability on the DC side reaches its limit, the regulation range is then extended to the AC side. The AC-side PEM electrolyzer and the AC-side alkaline electrolyzer sequentially participate in the regulation process of photovoltaic power in order to further consume the excess electric energy. After the regulation by the above-mentioned electrolyzers, if there is still unused photovoltaic power, it is first stored by the DC-side capacitive energy storage. When the DC-side capacitive energy storage approaches or reaches its storage upper limit, the AC-side capacitive energy storage is then used to supplement the storage. Through this orderly regulation sequence, the system can make full use of the characteristics of different devices to efficiently respond to changes in photovoltaic power, ensuring the stable operation and reasonable energy distribution of the power supply system of the offshore energy island under different energy inputs.

[0064] During specific implementation, when it is detected that the growth data of wind power exceeds the first preset value, the power of different devices in the hydrogen production, ammonia production, and alcohol production power supply device on the island is increased in the first preset order.

[0065] In one embodiment, when it is detected that the growth data of wind power exceeds the first preset value, increasing the power of different devices in the hydrogen production, ammonia production, and alcohol production power supply device on the island in the first preset order includes:

[0066] When it is detected that the growth data of wind power exceeds the first preset value, determine whether the AC load rate of the AC power supply device is greater than or equal to the first growth threshold;

[0067] If it is less than the first growth threshold, increase the power of the AC-side PEM electrolyzer or the AC-side alkaline electrolyzer; if it is greater than or equal to the first growth threshold, then determine whether the DC load rate of the DC power supply device is greater than or equal to the second growth threshold;

[0068] If it is less than the second growth threshold, increase the power of the DC-side PEM electrolyzer or the DC-side alkaline electrolyzer; if it is greater than or equal to the second growth threshold, then determine whether the AC long-term energy storage of the AC power supply device is greater than or equal to the third growth threshold;

[0069] If it is less than the third growth threshold, increase the charging power of the AC-side capacitive energy storage; if it is greater than or equal to the third growth threshold, then determine whether the DC long-term energy storage of the DC power supply device is greater than or equal to the fourth growth threshold;

[0070] If it is less than the fourth growth threshold, increase the charging power of the DC-side capacitive energy storage; if it is greater than or equal to the fourth growth threshold, increase the DC grid connection power of the DC power supply device or perform wind curtailment.

[0071] In one embodiment, increasing the power of the DC-side PEM electrolyzer or the DC-side alkaline electrolyzer includes:

[0072] Determine whether the load rate of the DC-side PEM electrolyzer is greater than or equal to the fifth growth threshold;

[0073] If it is less than the fifth growth threshold, increase the power of the DC-side PEM electrolyzer; if it is greater than or equal to the fifth growth threshold, increase the power of the DC-side alkaline electrolyzer;

[0074] Increasing the power of the AC-side PEM electrolyzer or the AC-side alkaline electrolyzer includes:

[0075] Determine whether the load rate of the AC-side PEM electrolyzer is greater than or equal to the sixth growth threshold;

[0076] If it is less than the sixth growth threshold, increase the power of the AC-side PEM electrolyzer; if it is greater than or equal to the sixth growth threshold, increase the power of the AC-side alkaline electrolyzer;

[0077] Increasing the DC grid connection power of the DC power supply device or performing wind curtailment includes:

[0078] Determine whether the DC grid connection power of the DC power supply device is greater than or equal to the seventh growth threshold;

[0079] If it is less than the seventh growth threshold, increase the DC grid connection power of the DC power supply device; if it is greater than or equal to the seventh growth threshold, perform wind curtailment.

[0080] In the above embodiment, when it is determined by a dedicated detection system that the growth data of the wind power exceeds the first preset value, the system will quickly activate the corresponding adjustment mechanism. First, the system will accurately judge the AC load rate of the AC power supply device and compare it with the first growth threshold. If the AC load rate is less than the first growth threshold, it indicates that there is still a certain load acceptance space on the AC side. At this time, according to the system command, the power of the AC-side PEM electrolyzer or the AC-side alkaline electrolyzer will be increased accordingly. When increasing the power of the AC-side PEM electrolyzer, it will further judge whether its load rate is less than the sixth growth threshold. If this condition is met, it means that the PEM electrolyzer still has the potential to increase power, and its power will be increased in an orderly manner to consume the excess wind power; if its load rate is greater than or equal to the sixth growth threshold, then the power of the AC-side alkaline electrolyzer will be increased instead, making full use of the characteristics of the alkaline electrolyzer to balance the growth of wind power.

[0081] If the AC load rate of the AC power supply device is greater than or equal to the first growth threshold, it means that the AC side may be close to or reach the load limit. At this time, the system will shift its attention to the DC load rate of the DC power supply device and compare it with the second growth threshold. If the DC load rate is less than the second growth threshold, the system will start to increase the power of the PEM electrolyzer or alkaline electrolyzer on the DC side. In this process, it will also first determine whether the load rate of the PEM electrolyzer on the DC side is less than the fifth growth threshold. If it is less than this threshold, the power of the PEM electrolyzer on the DC side will be increased preferentially; if it is greater than or equal to the fifth growth threshold, the power of the alkaline electrolyzer on the DC side will be increased, so as to achieve effective regulation of wind power.

[0082] When the DC load rate of the DC power supply device is greater than or equal to the second growth threshold, the system will further check the AC long-term energy storage situation of the AC power supply device to determine whether it is greater than or equal to the third growth threshold. If it is less than the third growth threshold, it means that there is still room for the AC side long-term energy storage to accept electrical energy. At this time, the charging power of the capacity-type energy storage on the AC side will be increased to store the excess wind power for subsequent use; if the AC long-term energy storage of the AC power supply device is greater than or equal to the third growth threshold, the system will then determine whether the DC long-term energy storage of the DC power supply device is greater than or equal to the fourth growth threshold. If it is less than the fourth growth threshold, the charging power of the capacity-type energy storage on the DC side will be increased to balance the power using the DC side energy storage; if the DC long-term energy storage of the DC power supply device is greater than or equal to the fourth growth threshold, the system will evaluate the DC grid-connected power of the DC power supply device to determine whether it is greater than or equal to the seventh growth threshold. If it is less than the seventh growth threshold, the DC grid-connected power of the DC power supply device will be increased to transmit part of the wind power to the external grid; if it is greater than or equal to the seventh growth threshold, it means that the system can no longer accept more wind power under the current conditions. At this time, wind curtailment will be adopted to ensure the safe and stable operation of the entire power supply system.

[0083] During this regulation process, due to the mismatch between the power supply and the load, fluctuations in the AC voltage and frequency and fluctuations in the DC voltage will occur. Power balance compensation can be carried out through the energy storage type MMC converter / AC energy storage converter.

[0084] The system can make full use of various devices and energy storage units in the hydrogen production, ammonia production and methanol production power supply device on the island to achieve reasonable distribution, conversion and storage of electrical energy when the wind power increases, ensuring that the power supply system of the offshore energy island can maintain a stable and efficient operation state under different working conditions.

[0085] During specific implementation, when it is detected that the reduction data of the wind power exceeds the second preset value, the power of different devices in the hydrogen production, ammonia production and methanol production power supply device on the island will be reduced in the first preset order.

[0086] In one embodiment, when it is detected that the reduction data of the wind power exceeds a second preset value, the power of different devices in the hydrogen production, ammonia production, and power supply device on the island is reduced in a first preset order, including:

[0087] When it is detected that the reduction data of the wind power exceeds a second preset value, determine whether the AC load rate of the AC power supply device is less than or equal to a first reduction threshold;

[0088] If it is greater than the first reduction threshold, reduce the power of the PEM electrolyzer on the AC side or the alkaline electrolyzer on the AC side; if it is less than or equal to the first reduction threshold, determine whether the DC load rate of the DC power supply device is less than or equal to a second reduction threshold;

[0089] If it is greater than the second reduction threshold, reduce the power of the PEM electrolyzer on the DC side or the alkaline electrolyzer on the DC side; if it is greater than or equal to the second reduction threshold, determine whether the AC long-term energy storage of the AC power supply device is less than or equal to a third reduction threshold;

[0090] If it is greater than the third reduction threshold, increase the discharge power of the capacitive energy storage on the AC side; if it is greater than or equal to the third reduction threshold, determine whether the DC long-term energy storage of the DC power supply device is less than or equal to a fourth reduction threshold;

[0091] If it is greater than the fourth reduction threshold, increase the discharge power of the capacitive energy storage on the DC side; if it is less than or equal to the fourth reduction threshold, reduce the DC grid connection power of the DC power supply device, increase the power of the fuel cell in the hydrogen production device, or stop the hydrogen production operation.

[0092] In one embodiment, reducing the power of the PEM electrolyzer on the DC side or the alkaline electrolyzer on the DC side includes:

[0093] Determine whether the load rate of the PEM electrolyzer on the DC side is less than or equal to a fifth reduction threshold;

[0094] If it is greater than the fifth reduction threshold, reduce the power of the PEM electrolyzer on the DC side; if it is less than or equal to the fifth reduction threshold, reduce the power of the alkaline electrolyzer on the DC side;

[0095] Reducing the power of the PEM electrolyzer on the AC side or the alkaline electrolyzer on the AC side includes:

[0096] Determine whether the load rate of the PEM electrolyzer on the AC side is less than or equal to a sixth reduction threshold;

[0097] If it is greater than the sixth reduction threshold, reduce the power of the PEM electrolyzer on the AC side; if it is less than or equal to the sixth reduction threshold, reduce the power of the alkaline electrolyzer on the AC side;

[0098] Reducing the DC grid connection power of the DC power supply device, increasing the power of the fuel cell in the hydrogen production device, or stopping the hydrogen production operation includes:

[0099] Determining whether the DC grid-connected power of the DC power supply device is less than or equal to a seventh reduction threshold;

[0100] If it is greater than the seventh decrease threshold, the DC grid-connected power of the DC power supply device is reduced; if it is less than or equal to the seventh decrease threshold, it is determined whether the fuel cell power in the hydrogen production device is greater than or equal to the eighth increase threshold;

[0101] If it is less than the eighth growth threshold, the fuel cell power in the hydrogen production device is increased; if it is greater than or equal to the eighth growth threshold, the hydrogen production operation is stopped.

[0102] In the above embodiment, once the detection system determines that the reduction data of wind power exceeds the second preset value, the power of each device in the island's hydrogen-producing ammonia power supply device is adjusted according to the established first preset order.

[0103] First, the system will compare the AC load rate of the AC power supply device with the first reduction threshold. If the AC load rate is greater than the first reduction threshold, this means that there is still a certain amount of power redundancy on the AC side for adjustment. At this time, reduce the power of the PEM electrolyzer on the AC side or the alkaline electrolyzer on the AC side. When reducing the power of the PEM electrolyzer on the AC side, it will first determine whether its load rate is greater than the fifth reduction threshold. If this condition is met, it means that the electrolyzer still has room for power reduction, and its power will be reduced accordingly; if its load rate is less than or equal to the fifth reduction threshold, the power of the alkaline electrolyzer on the AC side will be reduced to balance the reduction in wind power.

[0104] If the AC load rate of the AC power supply device is less than or equal to the first reduction threshold, the system will then determine whether the DC load rate of the DC power supply device is less than or equal to the second reduction threshold. If the DC load rate is greater than the second reduction threshold, it indicates that there is adjustable power space on the DC side, and the system will reduce the power of the PEM electrolyzer on the DC side or the alkaline electrolyzer on the DC side. In this process, it will first determine whether the load rate of the PEM electrolyzer on the DC side is greater than the sixth reduction threshold. If it is greater, the power of the PEM electrolyzer on the DC side will be reduced; if it is less than or equal to, the power of the alkaline electrolyzer on the DC side will be reduced.

[0105] When the DC load rate of the DC power supply device is less than or equal to the second reduction threshold, the system will further determine whether the AC long-term energy storage of the AC power supply device is less than or equal to the third reduction threshold. If the AC long-term energy storage is greater than the third reduction threshold, it indicates that the long-term energy storage on the AC side can release electric energy to supplement the power gap. At this time, the discharge power of the capacity-type energy storage on the AC side will be increased; if the AC long-term energy storage of the AC power supply device is less than or equal to the third reduction threshold, the system will then determine whether the DC long-term energy storage of the DC power supply device is less than or equal to the fourth reduction threshold. If the DC long-term energy storage is greater than the fourth reduction threshold, the discharge power of the capacity-type energy storage on the DC side will be increased, and the energy released by the energy storage will be used to maintain the system power balance.

[0106] If the DC long-term energy storage of the DC power supply device is less than or equal to the fourth reduction threshold, the system will evaluate the DC grid-connected power of the DC power supply device to determine whether it is less than or equal to the seventh reduction threshold. If the DC grid-connected power is greater than the seventh reduction threshold, the system will reduce the DC grid-connected power of the DC power supply device to reduce the electric energy output; if the DC grid-connected power is less than or equal to the seventh reduction threshold, the system will further determine whether the fuel cell power in the hydrogen production device is greater than or equal to the eighth increase threshold. If the fuel cell power is less than the eighth increase threshold, the fuel cell power in the hydrogen production device will be increased, and its power generation will be used to supplement the system power; if the fuel cell power is greater than or equal to the eighth increase threshold, the hydrogen production operation will be stopped to avoid system failures due to insufficient energy and ensure the stable and safe operation of the entire offshore energy island power supply system under reduced wind power.

[0107] During this adjustment process, due to the mismatch between the power supply and the load, fluctuations in the AC voltage and frequency and fluctuations in the DC voltage may occur, and power balance compensation can be performed through an energy storage type MMC converter / AC energy storage converter.

[0108] Through such a rigorous adjustment process, the system can make full use of various devices and energy storage units in the hydrogen production, ammonia, and alcohol power supply device on the island, and realize the reasonable distribution, conversion, and supplementation of electric energy when the wind power decreases, maintaining the stable operation state of the system.

[0109] During specific implementation, when it is detected that the growth data of the photovoltaic power exceeds the third preset value, the power of different devices in the hydrogen production, ammonia, and alcohol power supply device on the island is increased in the second preset order.

[0110] In one embodiment, when it is detected that the growth data of the photovoltaic power exceeds the third preset value, increasing the power of different devices in the hydrogen production, ammonia, and alcohol power supply device on the island in the second preset order includes:

[0111] When it is detected that the growth data of the photovoltaic power exceeds the third preset value, it is determined whether the DC load rate of the DC power supply device is greater than or equal to the second increase threshold;

[0112] If it is less than the second growth threshold, increase the power of the DC-side PEM electrolyzer or the DC-side alkaline electrolyzer; if it is greater than or equal to the second growth threshold, determine whether the AC load rate of the AC power supply device is greater than or equal to the first growth threshold.

[0113] If it is less than the first growth threshold, increase the power of the AC-side PEM electrolyzer or the AC-side alkaline electrolyzer; if it is greater than or equal to the first growth threshold, determine whether the DC long-term energy storage of the DC power supply device is greater than or equal to the fourth growth threshold.

[0114] If it is less than the fourth growth threshold, increase the charging power of the DC-side capacitive energy storage; if it is greater than or equal to the fourth growth threshold, determine whether the AC long-term energy storage of the AC power supply device is greater than or equal to the third growth threshold.

[0115] If it is less than the third growth threshold, increase the charging power of the AC-side capacitive energy storage; if it is greater than or equal to the third growth threshold, increase the DC grid connection power of the DC power supply device or perform light curtailment.

[0116] In the above embodiments, during the actual operation of the offshore energy island power supply system, when monitoring the photovoltaic power and finding that its growth data exceeds the third preset value, the system will immediately start the corresponding adjustment mechanism to increase the power of different devices in the hydrogen, ammonia, and methanol power supply device on the island, and follow the second preset order.

[0117] First, the system will judge the DC load rate of the DC power supply device and compare it with the second growth threshold. If the DC load rate is less than the second growth threshold, it means that there is still a certain power acceptance space on the DC side. At this time, the system will preferentially increase the power of the DC-side PEM electrolyzer or the DC-side alkaline electrolyzer. When increasing the power of the DC-side PEM electrolyzer, its operating power will be reasonably increased according to its own operating parameters and performance characteristics, so that it can consume more electric energy for hydrogen production and other operations; if the DC-side PEM electrolyzer reaches its power limit or needs to be adjusted based on the comprehensive judgment of the system, then increase the power of the DC-side alkaline electrolyzer, and use the characteristics of the alkaline electrolyzer to further balance the growth of photovoltaic power.

[0118] If the DC load rate of the DC power supply device is greater than or equal to the second growth threshold, it indicates that the DC side may be close to or reach the load limit. At this time, the system will then determine whether the AC load rate of the AC power supply device is greater than or equal to the first growth threshold. If the AC load rate is less than the first growth threshold, the system will increase the power of the PEM electrolyzer on the AC side or the alkaline electrolyzer on the AC side. For the PEM electrolyzer on the AC side, the system will appropriately increase its power according to its current operating state and adjustable range, so that it can consume more photovoltaic electric energy in the AC power supply environment; if the PEM electrolyzer on the AC side cannot further increase the power, the power of the alkaline electrolyzer on the AC side will be increased to maintain the power balance of the system.

[0119] When the AC load rate of the AC power supply device is greater than or equal to the first growth threshold, the system will then determine whether the DC long-term energy storage of the DC power supply device is greater than or equal to the fourth growth threshold. If it is less than the fourth growth threshold, it means that there is still room for the DC side long-term energy storage to accept electric energy. At this time, the charging power of the capacity-type energy storage on the DC side will be increased to store the excess photovoltaic electric energy for subsequent use; if the DC long-term energy storage of the DC power supply device is greater than or equal to the fourth growth threshold, the system will further determine whether the AC long-term energy storage of the AC power supply device is greater than or equal to the third growth threshold.

[0120] If the AC long-term energy storage of the AC power supply device is less than the third growth threshold, the charging power of the capacity-type energy storage on the AC side will be increased to balance the power using the energy storage on the AC side; if the AC long-term energy storage of the AC power supply device is greater than or equal to the third growth threshold, this means that the energy storage space in the system is also close to saturation. At this time, the system will consider increasing the DC grid connection power of the DC power supply device to transmit part of the photovoltaic electric energy to the external power grid; if the DC grid connection power cannot be further increased or based on the overall operation consideration of the system, the system will take the measure of curtailment of light to ensure the safe and stable operation of the entire power supply system and avoid system failures or unstable situations caused by excessive growth of photovoltaic power.

[0121] Through such an orderly adjustment process, the system can make full use of various devices and energy storage units in the hydrogen production, ammonia production, and alcohol production power supply device on the island, and realize the reasonable distribution, conversion, and storage of electric energy when the photovoltaic power increases, ensuring that the power supply system of the offshore energy island can maintain a stable and efficient operating state under different working conditions.

[0122] Specifically in implementation, when it is detected that the reduction data of the photovoltaic power exceeds the fourth preset value, the power of different devices in the hydrogen production, ammonia production, and alcohol production power supply device on the island is reduced in the second preset order.

[0123] In one embodiment, when it is detected that the reduction data of the photovoltaic power exceeds the fourth preset value, reducing the power of different devices in the hydrogen production, ammonia production, and alcohol production power supply device on the island in the second preset order includes:

[0124] Determine whether the DC load rate of the DC power supply device is less than or equal to the second reduction threshold;

[0125] If it is greater than the second reduction threshold, reduce the power of the PEM electrolyzer on the DC side or the alkaline electrolyzer on the DC side; if it is greater than or equal to the second reduction threshold, determine whether the AC load rate of the AC power supply device is less than or equal to the first reduction threshold;

[0126] If it is greater than the first reduction threshold, reduce the power of the PEM electrolyzer on the AC side or the alkaline electrolyzer on the AC side; if it is less than or equal to the first reduction threshold, determine whether the DC long-term energy storage of the DC power supply device is less than or equal to the fourth reduction threshold;

[0127] If it is greater than the fourth reduction threshold, increase the discharge power of the capacity-type energy storage on the DC side; if it is less than or equal to the fourth reduction threshold, determine whether the AC long-term energy storage of the AC power supply device is less than or equal to the third reduction threshold;

[0128] If it is greater than the third reduction threshold, increase the discharge power of the capacity-type energy storage on the AC side; if it is less than or equal to the third reduction threshold, reduce the DC grid-connected power of the DC power supply device, increase the power of the fuel cell in the hydrogen production device, or stop the hydrogen production operation.

[0129] In the above embodiments, in the actual operation of the offshore energy island power supply system, once the detected reduction data of the photovoltaic power exceeds the fourth preset value, the system will, in accordance with the established procedure, reduce and adjust the powers of different devices in the hydrogen production, ammonia, and alcohol power supply device on the island in the second preset order.

[0130] First, the system will compare the DC load rate of the DC power supply device with the second reduction threshold. If the DC load rate is greater than the second reduction threshold, it means that there is still a certain amount of power redundancy on the DC side that can be adjusted under the current conditions. At this time, the system will start to reduce the power of the PEM electrolyzer on the DC side or the alkaline electrolyzer on the DC side. For the PEM electrolyzer on the DC side, the system will reasonably reduce its working power according to its operating state and performance parameters to adapt to the reduction of the photovoltaic power; if the power of the PEM electrolyzer on the DC side is already at a low level or based on the comprehensive judgment of the system, a switch is needed, then the power of the alkaline electrolyzer on the DC side will be reduced to maintain the power balance of the system.

[0131] If the DC load rate of the DC power supply device is greater than or equal to the second reduction threshold, the system will further determine whether the AC load rate of the AC power supply device is less than or equal to the first reduction threshold. If the AC load rate is greater than the first reduction threshold, the system will reduce the power of the PEM electrolyzer on the AC side or the alkaline electrolyzer on the AC side. For the PEM electrolyzer on the AC side, the system will appropriately reduce its power according to its existing power and adjustable range to reduce the power consumption; if the PEM electrolyzer on the AC side cannot further reduce the power, the power of the alkaline electrolyzer on the AC side will be reduced.

[0132] When the AC load rate of the AC power supply device is less than or equal to the first reduction threshold, the system will then determine whether the DC long-term energy storage of the DC power supply device is less than or equal to the fourth reduction threshold. If the DC long-term energy storage is greater than the fourth reduction threshold, it means that there is still electrical energy available for release in the DC side long-term energy storage. At this time, the discharge power of the capacity-type energy storage on the DC side will be increased to release the stored electrical energy to supplement the system power to cope with the reduction of photovoltaic power; if the DC long-term energy storage of the DC power supply device is less than or equal to the fourth reduction threshold, the system will further determine whether the AC long-term energy storage of the AC power supply device is less than or equal to the third reduction threshold.

[0133] If the AC long-term energy storage of the AC power supply device is greater than the third reduction threshold, the discharge power of the capacity-type energy storage on the AC side will be increased to balance the power using the AC side energy storage; if the AC long-term energy storage of the AC power supply device is less than or equal to the third reduction threshold, this indicates that the energy storage resources of the system are already relatively tight. At this time, the system will consider reducing the DC grid connection power of the DC power supply device to reduce the electrical energy output to the outside; or increasing the power of the fuel cell in the hydrogen production device to supplement the system power using fuel cell power generation; if the system still cannot meet the system requirements after various adjustment measures, the system will stop the hydrogen production operation to ensure the stable operation of the entire power supply system under the condition of reduced photovoltaic power and avoid system failures or unstable conditions caused by insufficient energy.

[0134] During this adjustment process, fluctuations in AC voltage and frequency and DC voltage may be caused by the mismatch between the power supply and the load, and power balance compensation can be performed through an energy storage type MMC converter / AC energy storage converter.

[0135] The system can make full use of various devices and energy storage units in the hydrogen production, ammonia, methanol, and power supply device on the island to achieve reasonable distribution, conversion, and supplementation of electrical energy when the photovoltaic power is reduced, and maintain the stable operation state of the system.

[0136] In the embodiments of the present invention, by accurately monitoring the real-time wind power and orderly adjusting the power of each device in the hydrogen production, ammonia production and alcohol production power supply device on the island according to its increase or decrease, the fluctuating wind power energy can be effectively and reasonably allocated and converted. For example, when the wind power increases, the excess electric energy is preferentially used for operations such as hydrogen production, ammonia production and alcohol production, avoiding energy waste caused by the inability to consume it, greatly increasing the utilization ratio of offshore wind power in the entire energy system, enabling the offshore wind power, which was originally difficult to fully utilize due to large fluctuations, to be stably integrated into the energy supply system, and enhancing the stability and reliability of the energy supply. Adopting the AC-DC hybrid power supply mode, during the power regulation process, according to the energy source (wind power or photovoltaic) and the characteristics of each device on the DC or AC side, the power of each device in the DC power supply device and the AC power supply device is orderly adjusted. For example, when the photovoltaic power changes, the power of the relevant electrolyzers on the DC side is preferentially adjusted, reducing unnecessary AC-DC conversion links, reducing energy losses, ensuring that electric energy can be efficiently transmitted and utilized in the system, improving the overall power supply efficiency, and enabling the energy to more accurately meet the various load demands. During the process of coping with power fluctuations, the power-type energy storage and the capacity-type energy storage cooperate according to their different characteristics. For fast and frequent power fluctuations, the power-type energy storage responds quickly, avoiding the battery life loss of the capacity-type energy storage caused by frequent small-scale charge and discharge; while for long-term power changes, the capacity-type energy storage undertakes the regulation task, so that the power-type energy storage will not be over-fatigued due to long-term continuous operation. This reasonable regulation mechanism significantly reduces the number of ineffective charge and discharge times and the deep charge and discharge cycles of the energy storage device, effectively extends the overall service life of the energy storage device, and reduces the economic cost and maintenance workload brought by the frequent replacement of the energy storage device. Due to the extension of the service life of the energy storage device, the equipment replacement frequency and related maintenance work are reduced, directly reducing the equipment procurement and maintenance costs. Through the efficient energy coordination control strategy, the stability of the system operation is enhanced, the risk of equipment failure caused by power fluctuations is reduced, the cost of fault troubleshooting and repair is reduced, and the long-term maintenance cost of the offshore energy island power supply system is comprehensively reduced from multiple aspects, improving the economic benefits and operation stability of the system.

[0137] A specific embodiment is given below to illustrate the specific application of the method of the present invention.

[0138] In this embodiment, a power supply system solution for an offshore integrated energy island is proposed, including an offshore wind power flexible DC transmission system and an on-island hydrogen production, ammonia production and alcohol production power supply system. Among them, the offshore converter valve is located on the island, and the electric power generated by the sea breeze is transmitted to the land through submarine cables.

[0139] The DC power supply part and the AC power supply part of the hydrogen production, ammonia production, and power supply system on the island. The AC power supply part includes: high-voltage AC bus, medium-voltage AC bus, AC direct-connected energy storage, alkaline electrolyzer load (ALK), PEM electrolyzer load, power supply part for hydrogen production auxiliary equipment, power supply part for ammonia and alcohol production, auxiliary power supply part, and fuel cell power generation part. Among them, the capacity-type energy storage is generally electrochemical energy storage, which can be a large-capacity one; or it can be a combination of multiple small-capacity converters and electrochemical energy storage.

[0140] The DC power supply part includes: medium-voltage DC bus, low-voltage DC bus, energy storage type MMC converter (power type), DC transformer (SST), distributed photovoltaic, alkaline electrolyzer load (ALK), PEM electrolyzer load, and distributed energy storage. Among them, the energy storage type MMC refers to a converter with power-type energy storage, such as supercapacitors, flywheels and other power-type energy storage.

[0141] An AC-DC conversion device is configured between the low-voltage DC bus and the medium-voltage AC bus to provide two power supply sources for important loads, including power supply for auxiliary equipment, auxiliary power supply, and equipment for ammonia and alcohol production, to ensure the power supply safety of first-level loads.

[0142] The low-voltage DC bus adopts the method of bus switch interconnection or forming a ring network to improve power supply reliability.

[0143] Under normal operating conditions, the system ensures that the power of the flexible DC transmission part is relatively stable, and the upper and lower fluctuation ranges of the power are P rate -dP1~P rate +dP2, where P rate is the rated power, dP1 is the limit value of the power downward fluctuation, and dP2 is the limit value of the power upward fluctuation.

[0144] When the wind power increases, the adjustment of the hydrogen production load on the island is preferentially used to respond to the increase in wind power.

[0145] During this process, the power-type energy storage configured by the MMC stabilizes the frequency and voltage of the system to balance the power difference between the wind power and the load during the increase in wind power. When the wind power increases, the order of power regulation is the AC-side PEM electrolyzer, the AC-side alkaline electrolyzer, the DC-side PEM electrolyzer, the DC-side alkaline electrolyzer, the AC-side capacity-type energy storage, and the DC-side capacity-type energy storage.

[0146] Among them, the MMC is configured with power-type energy storage (such as supercapacitors). Energy is stored in the supercapacitors. Therefore, when there is a power difference between the wind power and the load, these power-type energy storage can release / storage energy through the MMC, so as to balance the power difference. The fluctuations of the system's frequency and voltage are caused by the power difference. Therefore, by compensating the power difference, the fluctuations can be reduced, and the frequency and voltage can be stabilized.

[0147] Figure 2 The connection relationships among the components in [component name] are as follows: Generally, the low-voltage DC bus is connected to the ALK / PEM electrolyzer load, photovoltaic, and capacitive energy storage. The connected voltage level is generally determined according to the characteristics of the load. For example, the port voltage of the ALK electrolyzer is relatively high and is suitable for connecting to a low-voltage DC bus with a relatively high voltage (1800V), while the port voltage of the PEM electrolyzer is relatively low and is suitable for connecting to a low-voltage DC bus with a relatively low voltage (750V). When selecting the capacity of the connected equipment, generally consider the capacity of the upper-level SST.

[0148] When the above adjustment measures still cannot absorb the increasing wind power, it is necessary to increase the grid-connected power of the flexible DC transmission within the power change range of the flexible DC transmission. When all the above measures are adopted and still cannot absorb the increasing wind power, the wind curtailment strategy is adopted. For the specific energy adjustment method, refer to Figure 4 the specific example diagram of the working method of a marine energy island power supply system in the embodiment of the present invention shown in Figure 4 which gives an energy adjustment strategy when the wind power increases.

[0149] When the wind power decreases, the adjustment of the on-island hydrogen production load is preferentially used to respond to the decrease in wind power. During this process, the power-type energy storage configured by the MMC stabilizes the frequency and voltage of the system to balance the power difference between the wind power and the load during the decrease in wind power. When the wind power decreases, the order of power adjustment is the AC-side PEM electrolyzer, the AC-side alkaline electrolyzer, the DC-side PEM electrolyzer, the DC-side alkaline electrolyzer, the AC-side capacitive energy storage, and the DC-side capacitive energy storage. When the above adjustment measures still cannot balance the decreasing wind power, it is necessary to reduce the grid-connected power of the flexible DC transmission within the power change range of the flexible DC transmission.

[0150] Finally, the power of the fuel cell can be increased to balance the decrease in wind power. When all the above measures are adopted and still cannot balance the decreasing wind power, the hydrogen production system shuts down. If the wind power further decreases, the flexible DC system further reduces the power until it shuts down. For the specific energy adjustment method, refer to Figure 5 the specific example diagram of the working method of a marine energy island power supply system in the embodiment of the present invention shown in Figure 5 which gives an energy adjustment strategy when the wind power decreases.

[0151] When the optical power increases, the adjustment of the hydrogen production load on the island is preferentially adopted to respond to the increase in wind power.

[0152] During this process, the power-type energy storage configured by the MMC stabilizes the frequency and voltage of the system, which is used to balance the power difference between the photovoltaic power and the load during the increase of photovoltaic power.

[0153] When the photovoltaic power increases, the order of power regulation is the DC-side PEM electrolyzer, the DC-side alkaline electrolyzer, the AC-side PEM electrolyzer, the AC-side alkaline electrolyzer, the DC-side capacitive energy storage, and the AC-side capacitive energy storage.

[0154] When the above adjustment measures still cannot absorb the increased photovoltaic power, it is necessary to increase the grid-connected power of the flexible DC transmission within the power change range of the flexible DC transmission. When all the above measures are adopted and still cannot absorb the increased photovoltaic power, the curtailment strategy is adopted. For the specific energy adjustment method, refer to Figure 6 the specific example diagram of the working method of a marine energy island power supply system in the embodiment of the present invention shown in Figure 6 which gives an energy adjustment strategy when the optical power increases.

[0155] When the photovoltaic electric power decreases, the adjustment of the hydrogen production load on the island is preferentially adopted to respond to the decrease in photovoltaic power.

[0156] During this process, the power-type energy storage configured by the MMC stabilizes the frequency and voltage of the system, which is used to balance the power difference between the photovoltaic power and the load during the decrease of photovoltaic power.

[0157] When the photovoltaic power decreases, the order of power regulation is the DC-side PEM electrolyzer, the DC-side alkaline electrolyzer, the AC-side PEM electrolyzer, the AC-side alkaline electrolyzer, the DC-side capacitive energy storage, and the AC-side capacitive energy storage.

[0158] When the above adjustment measures still cannot balance the decreased photovoltaic power, it is necessary to reduce the grid-connected power of the flexible DC transmission within the power change range of the flexible DC transmission.

[0159] Finally, the power of the fuel cell can be increased to balance the decrease in photovoltaic electric power.

[0160] When all the above measures are adopted and still cannot balance the decreased photovoltaic power, the hydrogen production system shuts down. If the photovoltaic power further decreases, the flexible DC system further reduces the power until it shuts down. For the specific energy adjustment method, refer to Figure 7 the specific example diagram of the working method of a marine energy island power supply system in the embodiment of the present invention shown in Figure 7 which gives an energy adjustment strategy when the optical power increases.

[0161] Specifically, a specific embodiment of the working method in the present invention is given as follows. In this specific embodiment, 1a to 8a respectively represent the first growth threshold to the eighth growth threshold, and 1b to 7b respectively represent the first decrease threshold to the seventh decrease threshold:

[0162] This specific embodiment includes the following steps:

[0163] 1. Configure a reasonable grid connection capacity, hydrogen production, ammonia, and alcohol load, and energy storage capacity according to the capacity and power generation curve of the wind and light resources;

[0164] 2. Determine the voltage level according to the capacity level;

[0165] 3. Determine the power supply system architecture and capacity allocation according to the voltage level and capacity configuration information;

[0166] The power supply system includes an AC power supply part and a DC power supply part. The AC power supply part includes: a high-voltage AC bus, a medium-voltage AC bus, AC directly-connected energy storage, an alkaline electrolyzer load (ALK), a PEM electrolyzer load, a hydrogen production auxiliary power supply part, an ammonia and alcohol production power supply part, an auxiliary power supply part, and a fuel cell power generation part.

[0167] The DC power supply part includes: a medium-voltage DC bus, a low-voltage DC bus, an energy storage type MMC converter, a DC transformer (SST), distributed photovoltaic, an alkaline electrolyzer load (ALK), a PEM electrolyzer load, and distributed energy storage. An AC-DC conversion device is configured between the low-voltage DC bus and the medium-voltage AC bus to provide two power supply sources for important loads, including auxiliary power supply, auxiliary power supply, and power supply for ammonia and alcohol production equipment, to ensure the power supply safety of first-level loads. The low-voltage DC bus adopts a bus switch interconnection or forms a ring network to improve power supply reliability.

[0168] 4. During system operation, the grid-forming control is provided by the energy storage type MMC converter, and the frequent small-range power fluctuations of the wind power / photovoltaic system are also suppressed by the energy storage type MMC converter using the power type energy storage unit.

[0169] The long-term power fluctuations of the wind / solar power are mainly responded to by adjusting the hydrogen production load and the charge and discharge of long-term energy storage. The specific strategy is as follows:

[0170] 1) When the wind power increases, first judge whether the AC load rate is greater than the fixed value 1a of the upper limit. If it is not greater, then preferentially adjust the AC load. When adjusting the AC load, first judge whether the load rate of the PEM electrolyzer is greater than the fixed value 6a. If it is not greater, then first adjust the PEM electrolyzer and increase the power of the PEM electrolyzer. If the PEM electrolyzer has reached the upper limit, then increase the power of the alkaline electrolyzer on the AC side to respond to the increase in wind power. When the AC load rate is greater than the upper limit value 1a, then judge whether the DC load rate is greater than the fixed value 2a of the upper limit. If it is not greater than the upper limit, the power of the electrolyzer on the DC side can be adjusted. Similarly, the power of the PEM electrolyzer is preferentially increased. When the DC load rate also reaches the upper limit, charge the long-term energy storage on the AC side. When the capacity of the long-term energy storage on the AC side reaches the upper limit, charge the long-term energy storage on the DC side. When the capacity of the long-term energy storage on the DC side also reaches the upper limit, the power of the DC grid connection can be appropriately adjusted. When the grid connection power increases to the upper limit, the excess wind resources are abandoned.

[0171] Where:

[0172] The fixed value 1a is the power upper limit of the AC load;

[0173] The fixed value 2a is the power upper limit of the DC load;

[0174] The fixed value 3a is the capacity upper limit of the AC long-term energy storage;

[0175] The fixed value 4a is the capacity upper limit of the DC long-term energy storage;

[0176] The fixed value 5a is the power upper limit of the PEM electrolyzer on the DC side;

[0177] The fixed value 6a is the power upper limit of the PEM electrolyzer on the AC side;

[0178] The fixed value 7a is the power upper limit of the DC grid connection;

[0179] 2) When the wind power decreases, first determine whether the AC load rate is less than the fixed value 1b of the lower limit. If it is not less, then preferentially adjust the AC load. When adjusting the AC load, first determine whether the load rate of the PEM electrolyzer is less than the fixed value 6b. If it is not less, then first adjust the PEM electrolyzer to reduce the power of the PEM electrolyzer. If the PEM electrolyzer has reached the lower limit, then reduce the power of the alkaline electrolyzer on the AC side to respond to the decrease in wind power. When the AC load rate is less than the lower limit 1b, then determine whether the DC load rate is less than the lower limit 2b. If it is not less than the upper limit, the power of the electrolyzer on the DC side can be adjusted. Similarly, the power of the PEM electrolyzer is preferentially reduced. When the DC load rate also reaches the lower limit, discharge the long-term energy storage on the AC side. When the capacity of the long-term energy storage on the AC side reaches the lower limit, discharge the long-term energy storage on the DC side. When the capacity of the long-term energy storage on the DC side also reaches the lower limit, the power of the DC grid connection can be appropriately adjusted. When the power of the grid connection decreases to the lower limit, increase the power of the fuel cell. If the power of the fuel cell has reached the upper limit, the hydrogen production part shuts down.

[0180] Among them:

[0181] The fixed value 1b is the lower limit of the power of the AC load;

[0182] The fixed value 2b is the lower limit of the power of the DC load;

[0183] The fixed value 3b is the lower limit of the capacity of the long-term energy storage on the AC side;

[0184] The fixed value 4b is the lower limit of the capacity of the long-term energy storage on the DC side;

[0185] The fixed value 5b is the lower limit of the power of the PEM electrolyzer on the DC side;

[0186] The fixed value 6b is the lower limit of the power of the PEM electrolyzer on the AC side;

[0187] The fixed value 7b is the lower limit of the power of the DC grid connection;

[0188] The fixed value 8a is the upper limit of the power of the DC grid connection;

[0189] 3) When the photovoltaic power increases, since the photovoltaic is connected to the DC side, the hydrogen production load and energy storage on the DC side need to respond preferentially, so the overall efficiency of the system will be higher. The other parts are similar to the case of increasing wind power. For details, see Figure 6 , which will not be elaborated here.

[0190] 4) When the photovoltaic power decreases, since the photovoltaic is connected to the DC side, the hydrogen production load and energy storage on the DC side need to respond preferentially, so the overall efficiency of the system will be higher. The other parts are similar to the case of decreasing wind power. For details, see Figure 7 , which will not be elaborated here.

[0191] In this specific embodiment, the fluctuating energy part in wind power can be used to prepare green hydrogen, ammonia and alcohol, and the stable part is used for flexible DC power transmission and grid connection, solving the problems of large fluctuations in offshore wind power, low utilization rate of the sea breeze flexible DC system, and difficult consumption. The power supply system of the energy island increases the DC power supply part, which is more friendly to the photovoltaic, energy storage and hydrogen production loads at the DC port, enabling the DC power supply and DC load to not require AC conversion, thus improving efficiency. At the same time, energy can be interchanged between AC and DC, enhancing reliability. The power-type energy storage and capacity-type energy storage are used in combination. The power-type energy storage responds to small frequency changes, and the capacity-type energy storage is mainly used to respond to long-term power differences. This can extend the service life of long-term energy storage. For the AC-DC interconnected system, a reasonable energy coordination control strategy is proposed by integrating different types of energy storage and different types of hydrogen production electrolyzers, improving the energy utilization rate of the system.

[0192] Of course, it can be understood that there can be other variations of the above detailed process, and related variations should all fall within the protection scope of the present invention.

[0193] In the embodiment of the present invention, the offshore energy island power supply system and its working method have significant effects in many aspects:

[0194] 1. Efficient energy utilization and stable supply:

[0195] In terms of offshore wind power, through the coordinated operation of the flexible DC transmission system and the hydrogen production, ammonia and alcohol power supply device on the island, the originally highly fluctuating and difficult-to-effectively utilize wind power resources are successfully converted into stable power supply and high-value-added hydrogen, ammonia and alcohol products. When the wind power fluctuates, the system orderly adjusts the power of each device according to preset rules to ensure the reasonable distribution and consumption of electric energy, greatly improving the utilization rate of offshore wind power, reducing the phenomenon of abandoned wind, enhancing the stability and reliability of energy supply, and providing a solid energy foundation for the continuous operation of the offshore energy island. For distributed photovoltaics, the generated electric energy can also be effectively integrated into the system. By real-time monitoring of the photovoltaic power and targeted power adjustment, the solar energy resources are fully utilized, realizing the comprehensive and efficient utilization of various energies on the island and reducing the dependence on external energy.

[0196] 2. Improvement of power supply efficiency:

[0197] The adoption of AC-DC hybrid power supply mode is a key factor in improving power supply efficiency. The DC power supply device provides a directly adaptable power supply path for devices such as photovoltaic, energy storage, and hydrogen production, avoiding the additional AC conversion link required for DC devices in the traditional AC power supply mode and reducing the energy loss during the conversion process. During the operation of the system, whether the wind power or photovoltaic power changes, the system can quickly respond according to the characteristics of different devices on the AC and DC sides, and preferentially perform power regulation on the DC side or AC side to ensure that electric energy can be transmitted and distributed in the system with the highest efficiency, meet the power consumption needs of various loads, and improve the energy utilization efficiency of the entire power supply system.

[0198] 3. Energy storage optimization and lifespan extension:

[0199] The unique energy storage configuration and control strategy bring significant advantages. The combination of power-type energy storage and capacity-type energy storage gives full play to the advantages of both. The power-type energy storage can quickly respond to the frequent small-amplitude power fluctuations of wind power and photovoltaics, absorb or release electric energy in a short time, maintain the system power balance, and avoid system instability caused by small fluctuations. The capacity-type energy storage focuses on dealing with long-term power changes, storing or releasing large-capacity electric energy in the case of excess or insufficient energy supply. This division of labor and cooperation mode greatly reduces the number of ineffective charge and discharge cycles and deep charge and discharge cycles of energy storage devices, effectively extends the service life of energy storage devices, reduces the economic cost and maintenance workload caused by frequent replacement of energy storage devices, and improves the overall economy and stability of the system.

[0200] 4. Enhanced system reliability:

[0201] At the system architecture level, the reasonable setting of the AC bus and DC bus and the configuration of the AC-DC conversion device provide two reliable power supply sources for important loads. When the power supply on one side fails or becomes unstable, the AC-DC conversion device can quickly switch the power supply mode to ensure the continuous operation of important loads and reduce the risk of system paralysis caused by local failures. The low-voltage DC bus adopts the method of bus switch interconnection or forming a ring network to further enhance the power supply reliability. When some lines fail, electric energy can be transmitted through other paths to achieve uninterrupted power supply, ensuring the stable operation of the offshore energy island power supply system in complex environments and various working conditions, and improving the fault tolerance and emergency response capabilities of the system.

[0202] Those skilled in the art should understand that the embodiments of the present invention can be provided as a method, a system, or a computer program product. Therefore, the present invention can take the form of a complete hardware embodiment, a complete software embodiment, or an embodiment combining software and hardware aspects. Moreover, the present invention can take the form of a computer program product implemented on one or more computer-usable storage media (including but not limited to disk memory, CD-ROM, optical memory, etc.) that contain computer-usable program code.

[0203] The present invention is described with reference to the flowcharts and / or block diagrams of methods, apparatuses (systems), and computer program products according to embodiments of the present invention. It should be understood that each flow and / or block in the flowchart and / or block diagram, and the combination of flows and / or blocks in the flowchart and / or block diagram, can be implemented by computer program instructions. These computer program instructions can be provided to the processor of a general-purpose computer, a special-purpose computer, an embedded processor, or other programmable data processing devices to generate a machine, such that the instructions executed by the processor of the computer or other programmable data processing devices produce means for implementing the functions specified in Figure 1 one flow or multiple flows and / or blocks Figure 1 one block or multiple blocks.

[0204] These computer program instructions can also be stored in a computer-readable memory that can direct a computer or other programmable data processing device to work in a specific manner, such that the instructions stored in the computer-readable memory produce a manufactured article including instruction means that implement the functions specified in Figure 1 one flow or multiple flows and / or blocks Figure 1 one block or multiple blocks.

[0205] These computer program instructions can also be loaded onto a computer or other programmable data processing device, such that a series of operation steps are executed on the computer or other programmable device to generate a computer-implemented process, and thus the instructions executed on the computer or other programmable device provide steps for implementing the functions specified in Figure 1 one flow or multiple flows and / or blocks Figure 1 one block or multiple blocks.

[0206] The specific embodiments described above further elaborate on the purpose, technical solution, and beneficial effects of the present invention. It should be understood that the above are only specific embodiments of the present invention and are not used to limit the protection scope of the present invention. Any modifications, equivalent replacements, improvements, etc. made within the spirit and principle of the present invention should be included in the protection scope of the present invention.

Claims

1. An offshore energy island power supply system, characterized in that, Including: A flexible HVDC transmission device for offshore wind power, which is used to transmit offshore wind power to the onshore power grid through submarine cables; An island hydrogen production, ammonia production and power supply device, including a DC power supply device and an AC power supply device, where: the DC power supply device includes an energy storage type MMC converter, a DC side capacitive energy storage, a DC side power type energy storage, a DC side PEM electrolyzer, a DC side alkaline electrolyzer, distributed photovoltaic, distributed energy storage and a hydrogen production device respectively connected to the DC bus; the energy storage type MMC converter is used to balance the power difference between wind power and load during the increase of wind power; the AC power supply device includes an AC side alkaline electrolyzer, an AC side PEM electrolyzer, an AC side capacitive energy storage and an ammonia production and alcohol production device respectively connected to the AC bus; the island hydrogen production, ammonia production and power supply device is used to perform hydrogen production, ammonia production and alcohol production operations on the offshore wind power, the photovoltaic power transmitted by distributed photovoltaic and distributed energy storage.

2. The system according to claim 1, wherein The AC bus includes: a high-voltage AC bus and a medium-voltage AC bus; the DC bus includes a medium-voltage DC bus and a low-voltage DC bus; The system further includes: an AC-DC conversion device, configured between the low-voltage DC bus and the medium-voltage AC bus, for providing two power supply sources.

3. The system according to claim 2, wherein The low-voltage DC bus is interconnected by a bus switch or forms a ring network.

4. A working method of a power supply system for an offshore energy island, characterized in that, Applied to the offshore energy island power supply system as described in any one of claims 1 to 3, the method includes: Real-time detection of the wind power of wind power and the photovoltaic power of the photovoltaic power transmitted by distributed photovoltaic in the DC power supply device; When it is detected that the growth data of the wind power exceeds a first preset value, increasing the power of different devices in the island hydrogen production, ammonia production and power supply device in a first preset order; When it is detected that the decrease data of the wind power exceeds a second preset value, decreasing the power of different devices in the island hydrogen production, ammonia production and power supply device in a first preset order; When it is detected that the growth data of the photovoltaic power exceeds a third preset value, increasing the power of different devices in the island hydrogen production, ammonia production and power supply device in a second preset order; When it is detected that the decrease data of the photovoltaic power exceeds a fourth preset value, decreasing the power of different devices in the island hydrogen production, ammonia production and power supply device in a second preset order.

5. The method according to claim 4, wherein The first preset order is the order of the AC side PEM electrolyzer, the AC side alkaline electrolyzer, the DC side PEM electrolyzer, the DC side alkaline electrolyzer, the AC side capacitive energy storage, and the DC side capacitive energy storage; the second preset order is the order of the DC side PEM electrolyzer, the DC side alkaline electrolyzer, the AC side PEM electrolyzer, the AC side alkaline electrolyzer, the DC side capacitive energy storage, and the AC side capacitive energy storage.

6. The method according to claim 4, wherein When it is detected that the growth data of the wind power exceeds a first preset value, increasing the power of different devices in the island hydrogen production, ammonia production and power supply device in a first preset order, including: When it is detected that the growth data of the wind power exceeds a first preset value, determining whether the AC load rate of the AC power supply device is greater than or equal to a first growth threshold; If it is less than the first growth threshold, increase the power of the AC-side PEM electrolyzer or the AC-side alkaline electrolyzer; if it is greater than or equal to the first growth threshold, determine whether the DC load rate of the DC power supply device is greater than or equal to the second growth threshold; If it is less than the second growth threshold, increase the power of the DC-side PEM electrolyzer or the DC-side alkaline electrolyzer; if it is greater than or equal to the second growth threshold, determine whether the AC long-term energy storage of the AC power supply device is greater than or equal to the third growth threshold; If it is less than the third growth threshold, increase the charging power of the AC-side capacitive energy storage; if it is greater than or equal to the third growth threshold, determine whether the DC long-term energy storage of the DC power supply device is greater than or equal to the fourth growth threshold; If it is less than the fourth growth threshold, increase the charging power of the DC-side capacitive energy storage; if it is greater than or equal to the fourth growth threshold, increase the DC grid connection power of the DC power supply device or take curtailment of wind power measures.

7. The method according to claim 6, characterized in that, Increasing the power of the DC-side PEM electrolyzer or the DC-side alkaline electrolyzer includes: Determine whether the load rate of the DC-side PEM electrolyzer is greater than or equal to the fifth growth threshold; If it is less than the fifth growth threshold, increase the power of the DC-side PEM electrolyzer; if it is greater than or equal to the fifth growth threshold, increase the power of the DC-side alkaline electrolyzer; Increasing the power of the AC-side PEM electrolyzer or the AC-side alkaline electrolyzer includes: Determine whether the load rate of the AC-side PEM electrolyzer is greater than or equal to the sixth growth threshold; If it is less than the sixth growth threshold, increase the power of the AC-side PEM electrolyzer; if it is greater than or equal to the sixth growth threshold, increase the power of the AC-side alkaline electrolyzer; Increasing the DC grid connection power of the DC power supply device or taking curtailment of wind power measures includes: Determine whether the DC grid connection power of the DC power supply device is greater than or equal to the seventh growth threshold; If it is less than the seventh growth threshold, increase the DC grid connection power of the DC power supply device; if it is greater than or equal to the seventh growth threshold, take curtailment of wind power measures.

8. The method according to claim 4, wherein When it is detected that the reduction data of the wind power exceeds the second preset value, reduce the power of different devices in the hydrogen production, ammonia, and methanol power supply device on the island in the first preset order, including: When it is detected that the reduction data of the wind power exceeds the second preset value, determine whether the AC load rate of the AC power supply device is less than or equal to the first reduction threshold; If it is greater than the first reduction threshold, reduce the power of the AC-side PEM electrolyzer or the AC-side alkaline electrolyzer; if it is less than or equal to the first reduction threshold, determine whether the DC load rate of the DC power supply device is less than or equal to the second reduction threshold; If it is greater than the second reduction threshold, reduce the power of the DC-side PEM electrolyzer or the DC-side alkaline electrolyzer; if it is greater than or equal to the second reduction threshold, determine whether the AC long-term energy storage of the AC power supply device is less than or equal to the third reduction threshold; If it is greater than the third reduction threshold, increase the discharge power of the AC-side capacitive energy storage; if it is greater than or equal to the third reduction threshold, determine whether the DC long-term energy storage of the DC power supply device is less than or equal to the fourth reduction threshold; If it is greater than the fourth decreasing threshold, increase the discharge power of the DC-side capacitive energy storage; if it is less than or equal to the fourth decreasing threshold, reduce the DC grid-connection power of the DC power supply device, increase the power of the fuel cell in the hydrogen production device, or stop the hydrogen production operation.

9. The method according to claim 8, wherein Reduce the power of the PEM electrolyzer or alkaline electrolyzer on the DC side, including: Determine whether the load rate of the PEM electrolyzer on the DC side is less than or equal to the fifth decreasing threshold; If it is greater than the fifth decreasing threshold, reduce the power of the PEM electrolyzer on the DC side; if it is less than or equal to the fifth decreasing threshold, reduce the power of the alkaline electrolyzer on the DC side; Reduce the power of the PEM electrolyzer or alkaline electrolyzer on the AC side, including: Determine whether the load rate of the PEM electrolyzer on the AC side is less than or equal to the sixth decreasing threshold; If it is greater than the sixth decreasing threshold, reduce the power of the PEM electrolyzer on the AC side; if it is less than or equal to the sixth decreasing threshold, reduce the power of the alkaline electrolyzer on the AC side; Reduce the DC grid-connection power of the DC power supply device, increase the power of the fuel cell in the hydrogen production device, or stop the hydrogen production operation, including: Determine whether the DC grid-connection power of the DC power supply device is less than or equal to the seventh decreasing threshold; If it is greater than the seventh decreasing threshold, reduce the DC grid-connection power of the DC power supply device; if it is less than or equal to the seventh decreasing threshold, determine whether the power of the fuel cell in the hydrogen production device is greater than or equal to the eighth increasing threshold; If it is less than the eighth increasing threshold, increase the power of the fuel cell in the hydrogen production device; if it is greater than or equal to the eighth increasing threshold, stop the hydrogen production operation.

10. The method according to claim 4, wherein When it is detected that the growth data of the photovoltaic power exceeds the third preset value, increase the power of different devices in the hydrogen production, ammonia, and alcohol power supply device on the island in the second preset order, including: When it is detected that the growth data of the photovoltaic power exceeds the third preset value, determine whether the DC load rate of the DC power supply device is greater than or equal to the second increasing threshold; If it is less than the second increasing threshold, increase the power of the PEM electrolyzer or alkaline electrolyzer on the DC side; if it is greater than or equal to the second increasing threshold, determine whether the AC load rate of the AC power supply device is greater than or equal to the first increasing threshold; If it is less than the first increasing threshold, increase the power of the PEM electrolyzer or alkaline electrolyzer on the AC side; if it is greater than or equal to the first increasing threshold, determine whether the DC long-term energy storage of the DC power supply device is greater than or equal to the fourth increasing threshold; If it is less than the fourth increasing threshold, increase the charging power of the DC-side capacitive energy storage; if it is greater than or equal to the fourth increasing threshold, determine whether the AC long-term energy storage of the AC power supply device is greater than or equal to the third increasing threshold; If it is less than the third increasing threshold, increase the charging power of the AC-side capacitive energy storage; if it is greater than or equal to the third increasing threshold, increase the DC grid-connection power of the DC power supply device or perform light curtailment treatment.

11. The method according to claim 4, characterized in that, When it is detected that the decrease data of the photovoltaic power exceeds the fourth preset value, reduce the power of different devices in the hydrogen production, ammonia, and alcohol power supply device on the island in the second preset order, including: Determine whether the DC load rate of the DC power supply device is less than or equal to the second decreasing threshold; If it is greater than the second decreasing threshold, reduce the power of the DC-side PEM electrolyzer or the DC-side alkaline electrolyzer; if it is greater than or equal to the second decreasing threshold, determine whether the AC load rate of the AC power supply device is less than or equal to the first decreasing threshold; If it is greater than the first decreasing threshold, reduce the power of the AC-side PEM electrolyzer or the AC-side alkaline electrolyzer; if it is less than or equal to the first decreasing threshold, determine whether the DC long-term energy storage of the DC power supply device is less than or equal to the fourth decreasing threshold; If it is greater than the fourth decreasing threshold, increase the discharge power of the DC-side capacitive energy storage; if it is less than or equal to the fourth decreasing threshold, determine whether the AC long-term energy storage of the AC power supply device is less than or equal to the third decreasing threshold; If it is greater than the third decreasing threshold, increase the discharge power of the AC-side capacitive energy storage; if it is less than or equal to the third decreasing threshold, reduce the DC grid-connected power of the DC power supply device, increase the power of the fuel cell in the hydrogen production device, or stop the hydrogen production operation.

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