Offshore wind power transmission system, method and equipment and storage medium

Abstract

The invention belongs to the field of wind power, and discloses an offshore wind power transmission system, method and device and a storage medium, the system comprises an offshore wind turbine group, an offshore current conversion module, an onshore current conversion module and an onshore power grid which are connected in sequence, and the offshore current conversion module comprises a DRU current conversion sub-module and an offshore MMC current conversion sub-module. The DRU current conversion sub-module, the offshore MMC current conversion sub-module and the land current conversion module form a series circuit; the onshore current conversion module is used for charging the offshore MMC current conversion sub-module according to the reverse direct current voltage; the offshore MMC current conversion sub-module is used for modulating and generating alternating current voltage; the land converter module is cooperated to invert the reverse direct-current voltage into the forward direct-current voltage; the offshore wind turbine group is used for starting frequency modulation and outputting alternating current to the DRU current conversion sub-module after frequency modulation is completed; and the DRU current conversion sub-module is used for converting alternating current output by the offshore wind turbine group into direct current, transmitting the direct current to the onshore current conversion module and further transmitting the direct current to an onshore power grid.

Description

Technical Field

[0001] The present invention belongs to the field of wind power, relates to a transmission method, and in particular to a transmission system, method, equipment and storage medium for offshore wind power. Background Art

[0002] Under the national dual carbon goals, the development of new energy will enter a rapid and concentrated period. Offshore wind power has the advantages of stable wind power, large reserves, and high wind power density, which is very suitable for the centralized operation of large-capacity units. On the other hand, coastal economically developed areas are often power load centers. Therefore, offshore wind power has a specific and significant strategic significance for our energy and power transformation.

[0003] In related technologies, offshore wind power is generally transmitted by AC transmission, and then connected to the grid after being transmitted to land. However, AC transmission has problems such as short transmission distance, the need for reactive power compensation equipment, and large line loss, which restrict the development of offshore large-capacity wind power. Summary of the invention

[0004] In view of this, the present invention discloses an offshore wind power transmission system, method, device and storage medium, which can solve the deficiencies in the related technology.

[0005] To achieve the above purpose, the present invention discloses the following technical solutions: According to a first aspect of the present invention, a transmission system for offshore wind power is proposed, the system comprising an offshore wind turbine group, an offshore converter module, an onshore converter module, and an onshore power grid connected in sequence, the offshore converter module comprising a DRU converter module and an offshore MMC converter module, the DRU converter module, the offshore MMC converter module, and the onshore converter module forming a series circuit; wherein the DRU converter module is composed of one or more DRU converters, and the offshore MMC converter module and the onshore converter module are composed of one or more MCC converters; The onshore converter module is used to charge the offshore MMC converter module according to the reverse DC voltage when the onshore power grid charges the onshore converter module to a first rated capacitance through an AC current; The offshore MMC converter module is used to: when charged to the second rated capacitance by the onshore converter module, modulate and generate an AC voltage to provide voltage and frequency conditions for the offshore wind turbine group to be connected to the grid; cooperate with the onshore converter module to reverse the reverse DC voltage to a forward DC voltage, so that the DRU converter module is disconnected during the process of the offshore wind turbine group being connected to the grid; The offshore wind turbine group is used to: start frequency modulation when the AC voltage generated by the offshore MMC commutation submodule is detected, and output AC power to the DRU commutation submodule after the frequency modulation is completed, so as to turn on the DRU commutation submodule; The DRU commutation submodule is used to convert the alternating current output by the offshore wind turbine group into direct current, and transmit it to the onshore commutation module, and then transmit it to the onshore power grid.

[0006] According to a second aspect of the present invention, a transmission method for offshore wind power is proposed, which is applied to a control module of an offshore wind power transmission system, wherein the system comprises an offshore wind turbine group, an offshore converter module, an onshore converter module, and an onshore power grid connected in sequence, wherein the offshore converter module comprises a DRU converter module and an offshore MMC converter module, wherein the DRU converter module, the offshore MMC converter module, and the onshore converter module form a series circuit; wherein the DRU converter module is composed of one or more DRU converters, and the offshore MMC converter module and the onshore converter module are composed of one or more MCC converters; the method comprises: The offshore wind turbine group is controlled to transmit electric energy to the onshore power grid.

[0007] As a preferred solution, the controlling the offshore wind turbine group to transmit electric energy to the onshore power grid includes: When the onshore power grid charges the onshore converter module to a first rated capacitance through an alternating current, the onshore converter module is controlled to generate a reverse direct current voltage and charge the offshore MMC converter module; When the onshore converter module charges the onshore converter module to a second rated capacitance, the offshore MMC converter module is controlled to modulate and generate an AC voltage to provide voltage and frequency conditions for the offshore wind turbine group to be connected to the grid; Controlling the offshore MMC converter module to cooperate with the onshore converter module to reverse the reverse DC voltage to a forward DC voltage, so that the DRU converter module is disconnected during the grid connection process of the offshore wind turbine group; When the AC voltage generated by the offshore MMC converter module is detected, the offshore wind turbine group is controlled to start frequency modulation, and after the frequency modulation is completed, AC power is output to the DRU converter module to turn on the DRU converter module; The DRU converter module is controlled to convert the AC power output by the offshore wind turbine group into DC power, and transmit the DC power to the onshore converter module, and then to the onshore power grid.

[0008] According to a third aspect of the present invention, an electronic device is provided, comprising: processor; a memory for storing processor-executable instructions; The processor implements the steps of the method described in the second aspect by running the executable instructions.

[0009] According to a fourth aspect of the present invention, a computer-readable storage medium is provided, on which computer instructions are stored, and when the instructions are executed by a processor, the steps of the method described in the second aspect are implemented.

[0010] It can be seen from the above technical solutions that the offshore wind power transmission method disclosed in the present invention, on the one hand, realizes direct current transmission of offshore wind power through DRU converters, and flexible direct current transmission reduces the transmission cost and reduces the loss during the transmission process; on the other hand, the topological structure of wind power transmission composed of offshore wind turbine groups, offshore converter modules, onshore converter modules, and onshore power grids adopts a phased start-up strategy to avoid the complex network control of multiple wind turbines, and does not require additional equipment such as bypass switches, thereby reducing the complexity of the system; in addition, the cascade structure of small-capacity MMC and large-capacity DRU significantly reduces equipment costs, taking into account both economy and flexibility. BRIEF DESCRIPTION OF THE DRAWINGS

[0011] Figure 1 It is a structural schematic diagram of an offshore wind power transmission system provided by an exemplary embodiment.

[0012] Figure 2 is a schematic diagram of a reverse DC voltage provided by an exemplary embodiment.

[0013] Figure 3 is a schematic diagram of a reverse voltage provided by an exemplary embodiment.

[0014] Figure 4 It is a schematic diagram of transmitting wind power provided by an exemplary embodiment.

[0015] Figure 5 is a schematic diagram of a bridge module provided by an exemplary embodiment.

[0016] Figure 6 It is a flow chart of a method for transmitting offshore wind power provided by an exemplary embodiment.

[0017] Figure 7 It is a schematic structural diagram of a device provided by an exemplary embodiment.

[0018] Figure 8 It is a block diagram of an offshore wind power transmission device provided by an exemplary embodiment. DETAILED DESCRIPTION

[0019] Exemplary embodiments will be described in detail herein, examples of which are shown in the accompanying drawings. When the following description refers to the drawings, the same numbers in different drawings represent the same or similar elements unless otherwise indicated. The embodiments described in the following exemplary embodiments do not represent all embodiments consistent with one or more embodiments of the present invention. Instead, they are merely examples of devices and methods consistent with some aspects of one or more embodiments of the present invention as detailed in the appended claims.

[0020] It should be noted that: in other embodiments, the steps of the corresponding method are not necessarily performed in the order shown and described in the present invention. In some other embodiments, the steps included in the method may be more or less than those described in the present invention. In addition, a single step described in the present invention may be decomposed into multiple steps for description in other embodiments; and multiple steps described in the present invention may be combined into a single step for description in other embodiments.

[0021] To further illustrate the present invention, the following examples are provided: Under the national dual carbon goals, the development of new energy will enter a rapid and concentrated period. Offshore wind power has the advantages of stable wind power, large reserves, and high wind power density, which is very suitable for the centralized operation of large-capacity units. On the other hand, coastal economically developed areas are often power load centers. Therefore, offshore wind power has a specific and significant strategic significance for our energy and power transformation.

[0022] In related technologies, offshore wind power is generally transmitted by AC transmission, and then connected to the grid after being transmitted to land. However, AC transmission has problems such as short transmission distance, the need for reactive power compensation equipment, and large line loss, which restrict the development of offshore large-capacity wind power.

[0023] In order to solve the deficiencies existing in the related art, the present invention proposes an offshore wind power transmission system.

[0024] Figure 1 FIG. 1 is a schematic diagram of a structure of an offshore wind power transmission system provided by an exemplary embodiment. Figure 1 As shown, the system includes an offshore wind turbine group 11, an offshore converter module 12, an onshore converter module 13, and an onshore power grid 14 which are connected in sequence.

[0025] The offshore converter module 12 includes a DRU converter submodule 121 and an offshore MMC converter submodule 122 , and the DRU converter submodule 121 and the offshore MMC converter submodule 122 are respectively connected to the offshore wind turbine group 11 .

[0026] The DRU converter module 121, the offshore MMC converter module 122 and the onshore converter module 13 form a series circuit, and the three are connected by a high-voltage DC cable 15. The DRU converter module 121 is composed of one or more DRU converters, and the offshore MMC converter module 122 and the onshore converter module 13 are composed of one or more MCC converters.

[0027] DRU is a rectifier based on diodes (uncontrollable semiconductor devices) to convert alternating current (AC) into direct current (DC). Its core feature is that it has no active control capability and only relies on external voltage conditions to achieve unidirectional conduction or shutdown. Figure 1 As shown, when the voltage of the DRU converter module 121 connected to the offshore wind turbine group or the offshore MMC converter module 122 is higher than the voltage of the onshore converter module 13, the diode is naturally turned on, that is, the DRU converter module 121 is turned on. Otherwise, the diode is automatically turned off, and the DRU converter module 121 is not turned on.

[0028] The MMC (Modular Multilevel Converter) converter is a voltage source converter (VSC) based on submodule cascade. It realizes high-voltage and high-power power conversion (AC / DC or DC / AC) through modular design and is the core equipment of modern flexible direct current transmission (HVDC). Its basic unit is the submodule (SM), and common types include half-bridge submodule (HBSM) and full-bridge submodule (FBSM).

[0029] The DRU converter is extremely economical and suitable for large-capacity, fixed-direction power transmission (such as offshore wind power transmission). It also has a simple structure and is suitable for high salt fog and high humidity environments at sea. However, the operation of the DRU converter depends on the cooperation of controllable converters such as the MMC converter (such as black start and fault ride-through), and cannot be used in scenarios that require bidirectional power flow (such as grid energy storage access). The MMC converter has a strong regulation capability, but requires a large number of IGBTs, which puts great cost pressure.

[0030] The present invention adopts a cascade design of MMC and DRU, which not only brings into play the flexible control capability of MMC (such as black start and voltage reversal), but also reduces the overall cost through DRU.

[0031] The onshore converter module 13 is used to charge the offshore MMC converter module according to the reverse DC voltage when the onshore power grid charges the onshore converter module to a first rated capacitance through AC current.

[0032] like Figure 2As shown, when the onshore converter module 13 is charged to the first rated capacitance, a reverse DC voltage is generated, that is, the side where the onshore converter module 13 is connected to the offshore MMC converter module 122 is a positive voltage, and the side where the onshore converter module 13 is connected to the DRU converter module 121 is a negative voltage (UD2 is positive, UD1 is negative). At this time, the voltage on the side where the DRU converter module 121 is connected to the offshore MMC converter module 122 is higher than the voltage on the side where the DRU converter module 121 is connected to the onshore converter module 13, and the DRU converter module 121 is turned on.

[0033] The offshore MMC converter module 122 is used to modulate and generate an AC voltage when it is charged to the second rated capacitance by the onshore converter module 13 to provide voltage and frequency conditions for the offshore wind turbine group to be connected to the grid.

[0034] Grid connection refers to connecting the electricity generated by the offshore wind turbine group to the onshore power grid through the converter station and the transmission system, so that wind power can be transmitted to the user end. The offshore MMC converter module 122 establishes modulation to generate a stable AC voltage, providing the voltage and frequency conditions required for grid connection for the wind turbine group. After the offshore wind turbine group detects the AC voltage provided by the offshore MMC converter module 122, it adjusts its own output to synchronize with it and connects to the AC bus of the offshore converter module 12 through a transformer. After the wind turbine is connected to the grid, it starts to generate electricity, and the electric energy is converted into DC through the DRU and MMC, and sent to the onshore converter station via the high-voltage DC line.

[0035] The offshore MMC converter module 122 is also used to cooperate with the onshore converter module 13 to invert the reverse DC voltage into a forward DC voltage, so that the DRU converter module 121 is disconnected during the grid-connection process of the offshore wind turbine group.

[0036] Specifically, Figure 3 As shown, the onshore MMC and the offshore MMC can be coordinated to gradually adjust the voltage and slowly reduce the reverse voltage amplitude (such as from -80kV→-40kV→0kV). Then the forward voltage is established (such as from 0kV→+40kV→±100kV). At this time, the DRU state is switched, and when the DC voltage turns to the forward direction (UD1=+100kV, UD2=-100kV), the DRU diode is naturally disconnected.

[0037] The offshore wind turbine group 11 is used to: start frequency modulation when detecting the AC voltage generated by the offshore MMC inverter module 122, and output AC power to the DRU inverter module 121 after the frequency modulation is completed, so as to turn on the DRU inverter module 121.

[0038] like Figure 4As shown, when the frequency modulation of the offshore wind turbine group is completed and the frequency and voltage are adjusted to synchronization, AC power is output to the DRU inverter module 121. The voltage of the AC power is higher than the voltage on the side where the DRU inverter module 121 is connected to the onshore inverter module 13. At this time, the DRU inverter module 121 is turned on.

[0039] The DRU converter module 13 is used to convert the AC power output by the offshore wind turbine group into DC power, and transmit it to the onshore converter module, and then transmit it to the onshore power grid.

[0040] In this embodiment, on the one hand, direct current transmission of offshore wind power is realized through DRU converters, and flexible direct current transmission reduces transmission costs and reduces losses during transmission; on the other hand, the topological structure of wind power transmission composed of offshore wind turbines, offshore converter modules, onshore converter modules, and onshore power grids adopts a phased start-up strategy to avoid complex network control of multiple wind turbines, and does not require additional equipment such as bypass switches, thereby reducing system complexity; in addition, the cascade structure of small-capacity MMC and large-capacity DRU significantly reduces equipment costs, taking into account both economy and flexibility.

[0041] In one embodiment, the offshore MMC converter module 122 is further used to control its own voltage to 0 when the DRU converter module 121 transmits the output of the offshore wind turbine group. This can reduce the complexity of system control.

[0042] In one embodiment, the rated DC voltage of the offshore MMC converter module is 40 kV, and the first rated capacitance is 20 MW; the rated DC voltage of the DRU converter module is 100 kV, and its third rated capacitance is 100 MW; the rated DC voltage of the onshore converter module is 100 kV, and the second rated capacitance is 100 MW.

[0043] In one embodiment, the AC voltage is 66 kV, and the offshore MMC converter module is connected to the offshore wind turbine group based on a 66 kV submarine cable.

[0044] In one embodiment, the MMC converter of the offshore MMC converter submodule is composed of a full-bridge submodule, and the MMC converter of the onshore converter module is composed of a full-bridge submodule and a half-bridge submodule.

[0045] As mentioned above, the basic unit of the MMC converter is the submodule, and common types include half-bridge submodule and full-bridge submodule. Figure 5As shown, the full-bridge submodule includes 4 IGBTs and 1 capacitor, and the half-bridge submodule includes 2 IGBTs and 1 capacitor. Compared with the half-bridge submodule, the full-bridge submodule is more flexible, but the cost is higher. Specifically, the composition ratio of the MMC converter of the onshore converter module can be 55% for the full-bridge submodule and 45% for the half-bridge submodule.

[0046] In this embodiment, since the MMC converter of the offshore MMC converter module is directly connected to the offshore wind turbine group, higher flexibility is required, so all of them need to be set as full-bridge submodules. The flexibility requirements of the MMC converter of the onshore converter module are relatively low. In order to control costs, a hybrid bridge submodule can be used.

[0047] In one embodiment, the onshore power grid is connected to the onshore converter module via a transformer, and the offshore wind turbine group is connected to the DRU converter module and the offshore MMC converter module via transformers, respectively.

[0048] like Figure 1 As shown, the offshore wind turbine group 11 is connected to the DRU converter module 121 through a transformer 161 , the offshore wind turbine group 11 is connected to the offshore MMC converter module 122 through a transformer 162 , and the onshore power grid 14 is connected to the onshore converter module 13 through a transformer 163 .

[0049] The transformer is the core equipment for realizing voltage level conversion and electrical isolation in the power system. In the process of wind turbine grid connection, the wind turbine outlet is boosted by a 690V / 66kV transformer and sent to the offshore converter module via the submarine cable. It can reduce the current of the collection line and reduce the loss of the submarine cable.

[0050] The present invention also provides a method for transmitting offshore wind power. Figure 6 FIG. 1 is a flow chart of a method for transmitting offshore wind power provided by an exemplary embodiment. Figure 6 As shown, a control module of a transmission system for offshore wind power is applied, the system comprises an offshore wind turbine group, an offshore converter module, an onshore converter module, and an onshore power grid connected in sequence, the offshore converter module comprises a DRU converter module and an offshore MMC converter module, the DRU converter module, the offshore MMC converter module and the onshore converter module form a series circuit; wherein the DRU converter module is composed of one or more DRU converters, the offshore MMC converter module and the onshore converter module are composed of one or more MCC converters; the method may comprise the following steps: The offshore wind turbine group is controlled to transmit electric energy to the onshore power grid.

[0051] In one embodiment, controlling the offshore wind turbine group to transmit electric energy to the onshore power grid includes: Step 601: When the onshore power grid charges the onshore converter module to a first rated capacitance through an alternating current, control the onshore converter module to generate a reverse direct current voltage and charge the offshore MMC converter module; Step 602: When the onshore converter module is charged to a second rated capacitance, the offshore MMC converter module is controlled to modulate and generate an AC voltage to provide voltage and frequency conditions for the offshore wind turbine group to be connected to the grid; Step 603, controlling the offshore MMC converter module to cooperate with the onshore converter module to reverse the reverse DC voltage to a forward DC voltage, so that the DRU converter module is disconnected during the grid-connection process of the offshore wind turbine group; Step 604: When the AC voltage generated by the offshore MMC commutation submodule is detected, the offshore wind turbine group is controlled to start frequency modulation, and after the frequency modulation is completed, AC power is output to the DRU commutation submodule to turn on the DRU commutation submodule; Step 605: Control the DRU commutation submodule to convert the AC power output by the offshore wind turbine group into DC power, and transmit it to the onshore commutation module, and then transmit it to the onshore power grid.

[0052] In this embodiment, on the one hand, direct current transmission of offshore wind power is realized through DRU converters, and flexible direct current transmission reduces transmission costs and reduces losses during transmission; on the other hand, the topological structure of wind power transmission composed of offshore wind turbines, offshore converter modules, onshore converter modules, and onshore power grids adopts a phased start-up strategy to avoid complex network control of multiple wind turbines, and does not require additional equipment such as bypass switches, thereby reducing system complexity; in addition, the cascade structure of small-capacity MMC and large-capacity DRU significantly reduces equipment costs, taking into account both economy and flexibility.

[0053] In one embodiment, the method further includes: when the DRU converter module transmits the output of the offshore wind turbine group, controlling the voltage of the offshore MMC converter module to 0 to reduce the complexity of system control.

[0054] In one embodiment, the rated DC voltage of the offshore MMC converter module is 40 kV, and the first rated capacitance is 20 MW; the rated DC voltage of the DRU converter module is 100 kV, and its third rated capacitance is 100 MW; the rated DC voltage of the onshore converter module is 100 kV, and the second rated capacitance is 100 MW.

[0055] In one embodiment, the AC voltage is 66 kV, and the offshore MMC converter module is connected to the offshore wind turbine group based on a 66 kV submarine cable.

[0056] In one embodiment, the MMC converter of the offshore MMC converter module is composed of a full-bridge submodule, and the MMC converter of the onshore converter module is composed of a full-bridge submodule and a half-bridge submodule. In this embodiment, since the MMC converter of the offshore MMC converter module is directly connected to the offshore wind turbine group, a higher flexibility is required, so all of them need to be set as full-bridge submodules, while the flexibility requirements of the MMC converter of the onshore converter module are relatively low, and a hybrid bridge submodule can be used to control costs.

[0057] In one embodiment, the onshore power grid is connected to the onshore converter module via a transformer, and the offshore wind turbine group is connected to the DRU converter module and the offshore MMC converter module via transformers, respectively.

[0058] Figure 7 is a schematic structural diagram of a device provided by an exemplary embodiment. Figure 7 At the hardware level, the device includes a processor 702, an internal bus 704, a network interface 706, a memory 708, and a non-volatile memory 710, and may also include hardware required for other functions. One or more embodiments of the present invention may be implemented based on software, such as the processor 702 reading the corresponding computer program from the non-volatile memory 710 into the memory 708 and then running it. Of course, in addition to the software implementation, one or more embodiments of the present invention do not exclude other implementations, such as logic devices or a combination of software and hardware, etc., that is, the execution subject of the following processing flow is not limited to each logic unit, but may also be hardware or logic devices.

[0059] Please refer to Figure 8 , an offshore wind power transmission device can be used for Figure 4 In the device shown, in order to implement the technical solution of the present invention, a control module of a transmission system for offshore wind power is applied, the system comprises an offshore wind turbine group, an offshore converter module, an onshore converter module, and an onshore power grid connected in sequence, the offshore converter module comprises a DRU converter module and an offshore MMC converter module, the DRU converter module, the offshore MMC converter module and the onshore converter module form a series circuit; wherein the DRU converter module is composed of one or more DRU converters, the offshore MMC converter module and the onshore converter module are composed of one or more MCC converters; the device may include: The charging unit 802 is used to control the onshore converter module to generate a reverse DC voltage and charge the offshore MMC converter module when the onshore power grid charges the onshore converter module to a first rated capacitance through an AC current; The generating unit 804 is used to control the offshore MMC converter module to modulate and generate an AC voltage when the onshore converter module is charged to a second rated capacitance, so as to provide voltage and frequency conditions for the offshore wind turbine group to be connected to the grid; The reversing unit 806 is used to control the offshore MMC converter module to cooperate with the onshore converter module to reverse the reverse DC voltage to a forward DC voltage, so that the DRU converter module is disconnected during the grid connection process of the offshore wind turbine group; The frequency modulation unit 808 is used to control the offshore wind turbine group to start frequency modulation when the AC voltage generated by the offshore MMC converter module is detected, and output AC power to the DRU converter module after the frequency modulation is completed, so as to turn on the DRU converter module; The transmission unit 810 is used to control the DRU converter module to convert the AC power output by the offshore wind turbine group into DC power, and transmit it to the onshore converter module, and then transmit it to the onshore power grid.

[0060] Optionally, also include: The control unit 812 is used to control the voltage of the offshore MMC converter module to 0 when the DRU converter module transmits the output of the offshore wind turbine group.

[0061] Optionally, the rated DC voltage of the offshore MMC converter module is 40kV, and the first rated capacitance is 20MW; the rated DC voltage of the DRU converter module is 100kV, and its third rated capacitance is 100MW; the rated DC voltage of the onshore converter module is 100kV, and the second rated capacitance is 100MW.

[0062] Optionally, the AC voltage is 66 kV, and the offshore MMC converter module is connected to the offshore wind turbine group based on a 66 kV submarine cable.

[0063] Optionally, the MMC converter of the offshore MMC converter submodule is composed of a full-bridge submodule, and the MMC converter of the onshore converter module is composed of a full-bridge submodule and a half-bridge submodule.

[0064] Optionally, the onshore power grid is connected to the onshore converter module via a transformer, and the offshore wind turbine group is connected to the DRU converter submodule and the offshore MMC converter submodule via transformers, respectively.

[0065] The systems, devices, modules or units described in the above embodiments may be implemented by computer chips or entities, or by products with certain functions. A typical implementation device is a computer, which may be in the form of a personal computer, a laptop computer, a cellular phone, a camera phone, a smart phone, a personal digital assistant, a media player, a navigation device, an email transceiver, a game console, a tablet computer, a wearable device or a combination of any of these devices.

[0066] In a typical configuration, a computer includes one or more processors (CPU), input / output interfaces, network interfaces, and memory.

[0067] Memory may include non-permanent storage in a computer-readable medium, in the form of random access memory (RAM) and / or non-volatile memory, such as read-only memory (ROM) or flash RAM. Memory is an example of a computer-readable medium.

[0068] Computer-readable media include permanent and non-permanent, removable and non-removable media that can be used to store information by any method or technology. Information can be computer-readable instructions, data structures, program modules or other data. Examples of computer storage media include, but are not limited to, phase change memory (PRAM), static random access memory (SRAM), dynamic random access memory (DRAM), other types of random access memory (RAM), read-only memory (ROM), electrically erasable programmable read-only memory (EEPROM), flash memory or other memory technology, compact disc read-only memory (CD-ROM), digital versatile disc (DVD) or other optical storage, magnetic cassettes, disk storage, quantum memory, graphene-based storage media or other magnetic storage devices or any other non-transmission media that can be used to store information that can be accessed by a computing device. As defined herein, computer-readable media does not include temporary computer-readable media (transitory media), such as modulated data signals and carrier waves.

[0069] With respect to the computer-readable medium (or computer-readable storage medium) as described above or in any other form, computer instructions may be stored thereon, and when the instructions are executed by a processor, one or more of the above-mentioned embodiments are implemented, thereby realizing the technical solution of the present invention.

[0070] The present invention also proposes a computer program, which, when executed by a processor, implements one or more of the above embodiments, thereby realizing the technical solution of the present invention. The computer program may be specifically recorded in the above or any other form of computer-readable medium, and the present invention is not limited thereto.

[0071] It should also be noted that the terms "include", "comprises" or any other variations thereof are intended to cover non-exclusive inclusion, so that a process, method, commodity or device including a series of elements includes not only those elements, but also other elements not explicitly listed, or also includes elements inherent to such process, method, commodity or device. In the absence of more restrictions, the elements defined by the sentence "comprises a ..." do not exclude the existence of other identical elements in the process, method, commodity or device including the elements.

[0072] The above describes specific embodiments of the present invention. Other embodiments are within the scope of the appended claims. In some cases, the actions or steps recorded in the claims can be performed in an order different from that in the embodiments and still achieve the desired results. In addition, the processes depicted in the accompanying drawings do not necessarily require the specific order or continuous order shown to achieve the desired results. In some embodiments, multitasking and parallel processing are also possible or may be advantageous.

[0073] The terms used in one or more embodiments of the present invention are only for the purpose of describing specific embodiments, and are not intended to limit one or more embodiments of the present invention. The singular forms of "a", "said" and "the" used in one or more embodiments of the present invention and the appended claims are also intended to include plural forms, unless the context clearly indicates other meanings. It should also be understood that the term "and / or" used herein refers to and includes any or all possible combinations of one or more associated listed items.

[0074] It should be understood that although the terms first, second, third, etc. may be used to describe various information in one or more embodiments of the present invention, these information should not be limited to these terms. These terms are only used to distinguish the same type of information from each other. For example, without departing from the scope of one or more embodiments of the present invention, the first information may also be referred to as the second information, and similarly, the second information may also be referred to as the first information. Depending on the context, the word "if" as used herein may be interpreted as "at the time of" or "when" or "in response to determining".

[0075] The above description is merely a preferred embodiment of one or more embodiments of the present invention and is not intended to limit one or more embodiments of the present invention. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of one or more embodiments of the present invention shall be included in the scope of protection of one or more embodiments of the present invention.

Claims

1. An offshore wind power transmission system, characterized in that: The system comprises an offshore wind turbine group, an offshore converter module, an onshore converter module, and an onshore power grid connected in sequence, wherein the offshore converter module comprises a DRU converter module and an offshore MMC converter module, wherein the DRU converter module, the offshore MMC converter module, and the onshore converter module form a series circuit; wherein the DRU converter module is composed of one or more DRU converters, and the offshore MMC converter module and the onshore converter module are composed of one or more MCC converters; The onshore converter module is used to charge the offshore MMC converter module according to the reverse DC voltage when the onshore power grid charges the onshore converter module to a first rated capacitance through an AC current; The offshore MMC converter module is used to: when charged to the second rated capacitance by the onshore converter module, modulate and generate an AC voltage to provide voltage and frequency conditions for the offshore wind turbine group to be connected to the grid; cooperate with the onshore converter module to reverse the reverse DC voltage to a forward DC voltage, so that the DRU converter module is disconnected during the process of the offshore wind turbine group being connected to the grid; The offshore wind turbine group is used to: start frequency modulation when the AC voltage generated by the offshore MMC commutation submodule is detected, and output AC power to the DRU commutation submodule after the frequency modulation is completed, so as to turn on the DRU commutation submodule; The DRU commutation submodule is used to convert the alternating current output by the offshore wind turbine group into direct current, and transmit it to the onshore commutation module, and then transmit it to the onshore power grid.

2. The system according to claim 1, characterized in that The offshore MMC commutation submodule is also used for: When the DRU converter module transmits the output of the offshore wind turbine group, its own voltage is controlled to 0.

3. The system according to claim 1, characterized in that The rated DC voltage of the offshore MMC converter module is 40 kV, and the first rated capacitance is 20 MW; the rated DC voltage of the DRU converter module is 100 kV, and its third rated capacitance is 100 MW; the rated DC voltage of the onshore converter module is 100 kV, and the second rated capacitance is 100 MW.

4. The system according to claim 1, characterized in that The AC voltage is 66 kV, and the offshore MMC converter module is connected to the offshore wind turbine group based on a 66 kV submarine cable.

5. The system according to claim 1, characterized in that The MMC converter of the offshore MMC converter submodule is composed of a full-bridge submodule, and the MMC converter of the onshore converter module is composed of a full-bridge submodule and a half-bridge submodule.

6. The system according to claim 1, characterized in that The onshore power grid is connected to the onshore converter module via a transformer, and the offshore wind turbine group is connected to the DRU converter submodule and the offshore MMC converter submodule via transformers respectively.

7. A method for transmitting offshore wind power, characterized in that: A control module for a transmission system for offshore wind power, the system comprising an offshore wind turbine group, an offshore converter module, an onshore converter module, and an onshore power grid connected in sequence, the offshore converter module comprising a DRU converter module and an offshore MMC converter module, the DRU converter module, the offshore MMC converter module, and the onshore converter module forming a series circuit; wherein the DRU converter module is composed of one or more DRU converters, and the offshore MMC converter module and the onshore converter module are composed of one or more MCC converters; the method comprising: The offshore wind turbine group is controlled to transmit electric energy to the onshore power grid.

8. The method according to claim 7, characterized in that The controlling the offshore wind turbine group to transmit electric energy to the onshore power grid comprises: When the onshore power grid charges the onshore converter module to a first rated capacitance through an alternating current, the onshore converter module is controlled to generate a reverse direct current voltage and charge the offshore MMC converter module; When the onshore converter module charges the second rated capacitance, the offshore MMC converter module is controlled to modulate and generate an AC voltage to provide voltage and frequency conditions for the offshore wind turbine group to be connected to the grid; Controlling the offshore MMC converter module to cooperate with the onshore converter module to reverse the reverse DC voltage to a forward DC voltage, so that the DRU converter module is disconnected during the grid connection process of the offshore wind turbine group; When the AC voltage generated by the offshore MMC converter module is detected, the offshore wind turbine group is controlled to start frequency modulation, and after the frequency modulation is completed, AC power is output to the DRU converter module to turn on the DRU converter module; The DRU converter module is controlled to convert the AC power output by the offshore wind turbine group into DC power, and transmit the DC power to the onshore converter module, and then to the onshore power grid.

9. An electronic device, characterized in that: include: processor; a memory for storing processor-executable instructions; The processor implements the steps of the method as described in claims 7-8 by running the executable instructions.

10. A computer-readable storage medium having computer instructions stored thereon, characterized in that: When the instruction is executed by the processor, the steps of the method as claimed in claims 7-8 are implemented.

Images