An offshore wind power transmission system

Abstract

This invention provides a deep-sea wind power transmission system, comprising: a wind turbine series subsystem, a diode rectifier series subsystem, a submarine DC cable, and an onshore converter; the wind turbine series subsystem, the diode rectifier series subsystem, the submarine DC cable, and the onshore converter are connected in series to form the deep-sea wind power transmission system; the wind turbine series subsystem is composed of several wind power generation units connected in series. Compared with traditional offshore wind power DC transmission systems, the high-voltage, high-capacity deep-sea wind power transmission system based on wind turbines and diode rectifiers in series eliminates the need for offshore booster stations and half of the offshore converter stations, resulting in significant economic advantages; the high-voltage, high-capacity deep-sea wind power transmission system based on wind turbines and diode rectifiers in series solves the problems of high output voltage and difficult insulation design of high-potential wind turbines in wind turbine series schemes, which helps to realize the application of high-voltage, high-capacity deep-sea wind power transmission.

Description

Technical Field

[0001] This invention belongs to the field of power conversion technology, specifically relating to an offshore wind power transmission system. Background Technology

[0002] Offshore wind power boasts advantages such as stable wind resources, high power generation utilization hours, no land occupation, and suitability for large-scale development. The focus of wind power development has shifted from onshore to offshore. With vast global coastlines and abundant offshore wind energy resources, the future large-scale development of offshore wind power will trend towards long-distance, deep-sea, and larger turbine units. DC transmission is more suitable for long-distance offshore wind power transmission.

[0003] Traditional offshore wind power DC transmission systems mainly consist of wind turbines, offshore booster stations, offshore converter stations, and onshore converter stations. Offshore converter stations often adopt a modular multilevel converter (MMC) topology, with a large number of cascaded sub-modules. As the DC voltage level and transmission power gradually increase, the technical and economic problems caused by the excessive size and weight of converter valves are becoming increasingly prominent. Therefore, it is urgent to carry out research on high-voltage, high-capacity offshore DC transmission schemes suitable for offshore wind power.

[0004] The diode rectifier series scheme consists of a diode rectifier and an MMC voltage source converter connected in series. It combines the advantages of both diode rectifiers and MMC voltage source converters, and some scholars have proposed this scheme as an alternative to traditional offshore wind power DC transmission schemes. Diode rectifiers offer advantages such as small size, low cost, and simple operation and control. The MMC can provide starting power and synchronization voltage for the wind farm, provide reactive power to both the wind farm and the diode rectifier, and absorb harmonic currents generated by the diode rectifier. Although the diode series scheme eliminates the need for an offshore booster station, reducing construction costs, the increasing DC voltage levels and transmission power still necessitate the construction of larger offshore converter stations and their platforms.

[0005] The series connection scheme for wind turbines eliminates the need for offshore booster stations and converter stations, further reducing the construction cost of offshore wind power. Some scholars have proposed that the series connection scheme replace the traditional DC transmission scheme for offshore wind power. However, the series connection scheme has problems such as high output voltage of high-potential wind turbines and difficulties in insulation design, making it impossible to achieve high-voltage, high-capacity, long-distance offshore wind power transmission. Summary of the Invention

[0006] To overcome the limitations of the prior art, the present invention provides an offshore wind power transmission system, comprising: a wind turbine series subsystem, a diode rectifier series subsystem, a submarine DC cable, and an onshore converter;

[0007] The wind turbine series subsystem, the diode rectifier series subsystem, the submarine DC cable and the onshore converter are connected in series to form the offshore wind power transmission system.

[0008] The wind turbine series subsystem consists of several wind power generation units connected in series.

[0009] Preferably, the wind turbine series subsystem, the diode rectifier series subsystem, the submarine DC cable, and the onshore converter are connected in series to form an offshore wind power transmission system, including:

[0010] One end of the onshore converter's DC side is connected to the offshore DC cable. The submarine DC cable is connected in series with one end of the diode rectifier series subsystem. The other end of the diode rectifier series subsystem is connected in series with one end of the wind turbine series subsystem. The other end of the wind turbine series subsystem is connected in series with one end of the diode rectifier series subsystem. The other end of the diode series subsystem is connected to the other end of the onshore converter's DC side via the submarine DC cable.

[0011] Preferably, the wind power generation unit includes a wind turbine generator, an isolation transformer, and a wind turbine converter;

[0012] The wind turbine generator and the isolation transformer are connected in series. The isolation transformer is connected in series with the AC terminal of the wind turbine converter, and the DC terminal of the wind turbine converter is connected to the submarine DC cable.

[0013] Preferably, the wind turbine converter includes: a rectifier, a capacitor, and a DC transformer;

[0014] The DC side of the rectifier is connected to the DC transformer, the capacitor is connected across the connection between the rectifier and the DC transformer, the AC side of the rectifier is connected to the isolation transformer, and one end of the DC transformer is connected to the submarine DC cable.

[0015] Preferably, the diode rectifier series subsystem includes: a wind farm, a submarine AC cable, and an offshore converter station;

[0016] The wind farm, the submarine AC cable, and the offshore converter station are connected sequentially on their AC sides, and the offshore converter station's DC side is connected to the submarine DC cable.

[0017] Preferably, the offshore converter station includes: a filter, a rectifier transformer, a converter transformer, a diode rectifier, and a voltage source converter;

[0018] One side of the rectifier transformer is connected to the AC side of the diode rectifier, and the other side is connected to the submarine AC cable.

[0019] One side of the converter transformer is connected to the AC side of the voltage source converter, and the other side is connected to the submarine AC cable.

[0020] One side of the filter is connected to the submarine AC cable, and the other side is grounded.

[0021] The DC side of the diode rectifier is connected in series with the DC side of the voltage source converter to form the DC side of the offshore converter station.

[0022] Preferably, the voltage source converter includes multiple bridge arms;

[0023] The bridge arm includes an upper bridge arm and a lower bridge arm. One end of multiple upper bridge arms is connected together to form the positive DC side of the voltage source converter. One end of multiple lower bridge arms is connected together to form the negative DC side of the voltage source converter. The other ends of multiple upper bridge arms and multiple lower bridge arms are respectively connected to form the voltage source converter.

[0024] Preferably, the bridge arm is composed of a bridge arm inductor and a full-bridge submodule connected in series. One end of the bridge arm inductor serves as the AC side of the voltage source converter, and one end of the full-bridge submodule serves as the DC side.

[0025] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0026] This invention provides a deep-sea wind power transmission system, comprising: a wind turbine series subsystem, a diode rectifier series subsystem, a submarine DC cable, and an onshore converter; the wind turbine series subsystem, the diode rectifier series subsystem, the submarine DC cable, and the onshore converter are connected in series to form the deep-sea wind power transmission system; the wind turbine series subsystem is composed of several wind power generation units connected in series. Compared with traditional offshore wind power DC transmission systems, the high-voltage, high-capacity deep-sea wind power transmission system based on wind turbines and diode rectifiers in series eliminates the need for offshore booster stations and half of the offshore converter stations, resulting in significant economic advantages; the high-voltage, high-capacity deep-sea wind power transmission system based on wind turbines and diode rectifiers in series solves the problems of high output voltage and difficult insulation design of high-potential wind turbines in wind turbine series schemes, which helps to realize the application of high-voltage, high-capacity deep-sea wind power transmission. Attached Figure Description

[0027] Figure 1 A schematic diagram of a offshore wind power transmission system provided by the present invention;

[0028] Figure 2 for Figure 1 Schematic diagram of the series subsystem of the medium-sized wind turbine;

[0029] Figure 3 for Figure 1 A schematic diagram of the series-connected diode rectifier subsystem. Detailed Implementation

[0030] The purpose of this invention is to design a deep-sea wind power transmission system that fully leverages the technical and economic advantages of the diode rectifier series scheme and the wind turbine series scheme to achieve high-voltage, high-capacity deep-sea wind power transmission.

[0031] To achieve the above objectives, the present invention provides the following technical solution:

[0032] This invention provides an offshore wind power transmission system, comprising: a wind turbine series subsystem, a diode rectifier series subsystem, a submarine DC cable, and an onshore converter; the wind turbine series subsystem, the diode rectifier series subsystem, the submarine DC cable, and the onshore converter are connected in series to form the offshore wind power transmission system; the wind turbine series subsystem is composed of several wind power generation units connected in series.

[0033] 1. Offshore wind power transmission system

[0034] This invention provides a offshore wind power transmission system, such as Figure 1 As shown, it consists of multiple wind farms, a series-connected wind turbine subsystem, a series-connected diode rectifier subsystem, submarine DC cables, and onshore converters. The series-connected wind turbine subsystems form a low-potential DC voltage on their DC sides, while the series-connected diode rectifier subsystems form a high-potential DC voltage on their DC sides. These two parts, connected in series, constitute the DC voltage for the offshore wind power transmission side. The series-connected wind turbine subsystem lacks an offshore converter station and an offshore substation. The series-connected diode rectifier subsystem lacks an offshore substation, but has an offshore converter station, which is located on an offshore platform.

[0035] 2. Fan series subsystem

[0036] Wind turbine series subsystem such as Figure 2 As shown, each wind turbine generator is connected to the AC side of the wind turbine converter via an isolation transformer, and the DC side of the wind turbine converter is connected in series to form the DC voltage of the wind turbine series subsystem. The isolation transformer isolates the wind turbine and the converter, ensuring that the wind turbine is at a low potential.

[0037] A wind turbine converter consists of a rectifier (AC / DC), a DC transformer (DC / DC), and a capacitor (C). The capacitor (C) is connected across the DC terminals of the rectifier (AC / DC). The rectifier (AC / DC) controls the active power of the wind turbine generator, converting the alternating current generated by the wind turbine into direct current, while the DC transformer (DC / DC) controls the DC voltage output.

[0038] 3. Diode rectifier series subsystem

[0039] Diode rectifier series subsystem such as Figure 3 As shown, the wind farm is connected to a submarine AC cable and a rectifier transformer (T). DR The wind farm is connected to the AC side of the diode rectifier (DR) via a submarine AC cable and a converter transformer (T). VSCThe wind farm is connected to the filter via a submarine AC cable, and the AC side of the voltage source converter (WFVSC) is connected in series with the filter. The diode rectifier (DR) is connected in series with the DC side of the voltage source converter (WFVSC).

[0040] Rectifier transformer (T) DR Diode rectifier (DR), converter transformer (T) VSC The voltage source converter (WFVSC) and filters are placed on the offshore platform.

[0041] The voltage source converter (WFVSC) consists of six bridge arms, each of which is composed of a bridge arm inductor (L) and multiple submodules (SM) connected in series. Each submodule (SM) consists of four IGBTs and one capacitor (C). sm This constitutes a full-bridge submodule. One end of each of the three upper bridge arms is connected together as the positive DC terminal of the voltage source converter (WFVSC), and one end of each of the three lower bridge arms is connected together as the negative DC terminal of the voltage source converter (WFVSC). The other ends of the three upper bridge arms and the other ends of the three lower bridge arms are respectively connected as the three-phase AC terminals of the voltage source converter (WFVSC). The DC side of the voltage source converter (WFVSC) is connected to the external circuit via a bypass switch (Sb) and an isolating switch (Si).

[0042] 4. System Control Strategy

[0043] The onshore converter station controls the DC current, and both the wind turbine series subsystem and the diode rectifier series subsystem control the power by controlling the DC voltage.

[0044] Those skilled in the art will understand that embodiments of the present invention can be provided as methods, systems, or computer program products. Therefore, the present invention can take the form of a completely hardware embodiment, a completely software embodiment, or an embodiment combining software and hardware aspects. Furthermore, the present invention can take the form of a computer program product embodied on one or more computer-usable storage media (including, but not limited to, disk storage, CD-ROM, optical storage, etc.) containing computer-usable program code.

[0045] This invention is described with reference to flowchart illustrations and / or block diagrams of methods, apparatus (systems), and computer program products according to embodiments of this application. It will be understood that each block of the flowchart illustrations and / or block diagrams, and combinations of blocks in the flowchart illustrations and / or block diagrams, can be implemented by computer program instructions. These computer program instructions can be provided to a processor of a general-purpose computer, special-purpose computer, embedded processor, or other programmable data processing apparatus to produce a machine, such that the instructions, which execute via the processor of the computer or other programmable data processing apparatus, generate instructions for implementing the flowchart illustrations and / or block diagrams. Figure 1One or more processes and / or boxes Figure 1 A device that provides the functions specified in one or more boxes.

[0046] These computer program instructions may also be stored in a computer-readable storage medium that can direct a computer or other programmable data processing device to function in a particular manner, such that the instructions stored in the computer-readable storage medium produce an article of manufacture including instruction means, which are implemented in a process Figure 1 One or more processes and / or boxes Figure 1 The function specified in one or more boxes.

[0047] These computer program instructions may also be loaded onto a computer or other programmable data processing equipment to cause a series of operational steps to be performed on the computer or other programmable equipment to produce a computer-implemented process, thereby providing instructions that execute on the computer or other programmable equipment for implementing the process. Figure 1 One or more processes and / or boxes Figure 1 The steps of the function specified in one or more boxes.

[0048] The above are merely embodiments of the present invention and are not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention are included within the scope of the claims of the present invention pending approval.

Claims

1. An offshore wind power transmission system, characterized in that, include: Wind turbine series subsystem, diode Rectifier series subsystem, submarine DC cable and onshore converter; The wind turbine series subsystem, diode rectifier series system, submarine DC cable and onshore converter The devices are connected in series to form an offshore wind power transmission system; The wind turbine series subsystem consists of several wind power generation units connected in series; Each wind turbine is connected to the AC side of the wind turbine converter via an isolation transformer, and the DC side of the wind turbine converter is connected in series to form the DC voltage of the wind turbine series subsystem. The isolation transformer isolates the wind turbine and the wind turbine converter to ensure that the wind turbine is at a low potential. The diode rectifier series subsystem includes: a wind farm, a submarine AC cable, and an offshore converter station; The wind farm is connected to the AC side of the diode rectifier via a submarine AC cable and a rectifier transformer. The wind farm is also connected to the AC side of the voltage source converter via a submarine AC cable and a converter transformer. The wind farm is connected to the filter via a submarine AC cable. The diode rectifier and the voltage source converter are connected in series on the DC side to form a high-potential DC voltage. The series connection of the wind turbine subsystem on the DC side forms a low-potential DC voltage, and the series connection of the diode rectifier subsystem on the DC side forms a high-potential DC voltage. The two parts are connected in series to form the DC voltage of the offshore wind power transmission side.

2. The system of claim 1, wherein, The wind turbine series subsystem, diode The rectifier series subsystem, submarine DC cable, and onshore converter are connected in series to form the offshore wind power transmission system, including: One end of the onshore converter's DC side is connected to the offshore DC cable. The submarine DC cable is connected in series with one end of the diode rectifier series subsystem. The other end of the diode rectifier series subsystem is connected in series with one end of the wind turbine series subsystem. The other end of the wind turbine series subsystem is connected in series with one end of the diode rectifier series subsystem. The other end of the diode series subsystem is connected to the other end of the onshore converter's DC side via the submarine DC cable.

3. The system as described in claim 2, characterized in that, The wind power generation unit includes wind power. Generators, isolation transformers, and wind turbine converters; The wind turbine generator and the isolation transformer are connected in series. The isolation transformer is connected in series with the AC terminal of the wind turbine converter, and the DC terminal of the wind turbine converter is connected to the submarine DC cable.

4. The system as described in claim 3, characterized in that, The wind turbine converter includes: a rectifier, a capacitor, and a DC transformer; The DC side of the rectifier is connected to the DC transformer, the capacitor is connected across the connection between the rectifier and the DC transformer, the AC side of the rectifier is connected to the isolation transformer, and one end of the DC transformer is connected to the submarine DC cable.

5. The system as described in claim 1, characterized in that, The offshore converter station includes: a filter, a rectifier transformer, a converter transformer, a diode rectifier, and a voltage source converter; One side of the rectifier transformer is connected to the AC side of the diode rectifier, and the other side is connected to the submarine AC cable. One side of the converter transformer is connected to the AC side of the voltage source converter, and the other side is connected to the submarine AC cable. One side of the filter is connected to the submarine AC cable, and the other side is grounded. The DC side of the diode rectifier is connected in series with the DC side of the voltage source converter to form the DC side of the offshore converter station.

6. The system as described in claim 5, characterized in that, The voltage source converter includes multiple bridge arms; The bridge arm includes upper bridge arms and lower bridge arms. One end of multiple upper bridge arms is connected together to form the positive DC side of the voltage source converter. One end of multiple lower bridge arms is connected together to form the negative DC side of the voltage source converter. The other ends of multiple upper bridge arms and multiple lower bridge arms are respectively connected to form the AC side of the voltage source converter. The DC side of the voltage source converter is connected to the submarine DC cable through a bypass switch and a disconnect switch.

7. The system as described in claim 6, characterized in that, The bridge arm is composed of a bridge arm inductor and a full-bridge submodule connected in series. One end of the bridge arm inductor serves as the AC side of the voltage source converter, and one end of the full-bridge submodule serves as the DC side.

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