Offshore wind power direct current conveying device

Abstract

An offshore wind power direct-current conveying device comprises an offshore wind power unit, an offshore converter station, a terminal conversion station, a receiving end converter station and a load center alternating-current power grid. The alternating current side of the offshore converter station is electrically connected with the offshore wind turbine generator through an alternating current collection submarine cable, the direct current side of the offshore converter station is electrically connected with the terminal conversion station through a direct current submarine cable, and the terminal conversion station is electrically connected with the receiving end converter station through a direct current overhead line. The receiving end converter station is electrically connected with the load center alternating current power grid through an alternating current line; wherein the offshore converter station adopts a diode rectification unit topological structure, and the receiving end converter station adopts a flexible direct current conversion unit with a half-bridge MMC structure; and the terminal conversion station comprises a first direct current circuit breaker configured on the direct current submarine cable and a direct current energy consumption device bridged on the direct current submarine cable. Compared with the prior art, loss, weight, size and manufacturing cost of the offshore converter station can be remarkably reduced.

Description

Technical Field

[0001] The utility model relates to the technical field of offshore wind power transmission engineering, in particular to an offshore wind power direct current transmission device. Background Art

[0002] At present, my country's offshore wind power DC transmission projects usually adopt flexible DC transmission technology, and use DC submarine cables to land, invert into AC power nearby, and then transmit to the load center through AC overhead lines. Foreign offshore wind power DC transmission projects usually use DC submarine cables to land, convert into DC land cables, and transmit them directly to the load center through long-distance DC land cables, and then invert into AC power to access the grid. With the development of offshore wind power towards large bases, scale, and deep sea, if the previous methods of transmission and access to the grid at home and abroad continue to be used, there will be difficulties in absorbing offshore wind power, insufficient land resources on the coastline of coastal cities near offshore wind farms, insufficient onshore transmission corridors, excessive short-circuit current in the power grid in the load center area, great challenges to the safety and stability of the power grid, and high costs of DC land cables.

[0003] In response to the above problems, the Chinese patents "CN117526394A Offshore Wind Power DC System" and "CN117526396A Offshore Wind Power DC System" propose to use a half-bridge MMC or full half-bridge MMC configuration for offshore converter stations, and a full half-bridge hybrid MMC topology configuration for onshore converter stations to clear DC overhead line faults. However, the offshore converter stations of the above two solutions use a half-bridge MMC or full half-bridge MMC topology, which results in a complex topology of the offshore converter station, large size and weight, and high cost. Summary of the invention

[0004] The present application provides an offshore wind power DC transmission device to solve the problem that the existing offshore converter station adopts a half-bridge MMC or full half-bridge MMC topology structure, which leads to a complex topology structure, large size and weight, and high cost of the offshore converter station.

[0005] In order to achieve the above-mentioned purpose, this application adopts the following technical solution.

[0006] An offshore wind power DC transmission device comprises: an offshore wind turbine set, an offshore converter station, a terminal conversion station, a receiving-end converter station and a load center AC power grid; the AC side of the offshore converter station is electrically connected to the offshore wind turbine set through an AC collector submarine cable, the DC side of the offshore converter station is electrically connected to the terminal conversion station through a DC submarine cable, the terminal conversion station is electrically connected to the receiving-end converter station through a DC overhead line, and the receiving-end converter station is electrically connected to the load center AC power grid through an AC line;

[0007] Among them, the offshore converter station adopts a diode rectifier unit topology structure, and the receiving-end converter station adopts a flexible DC converter unit with a half-bridge MMC structure; the terminal conversion station includes a first DC circuit breaker configured on the DC submarine cable and a DC energy consumption device connected across the DC submarine cable.

[0008] The offshore converter station using the diode rectifier unit topology structure in the above scheme has significant advantages such as small size, light weight, low cost, etc. Compared with the offshore converter station using the half-bridge or full-bridge MMC topology structure, the utility model can significantly reduce the loss, weight, size and cost of the offshore converter station.

[0009] In some embodiments, a second DC circuit breaker is configured on the DC overhead line.

[0010] In some embodiments, the terminal conversion station is located near the landing point of the DC submarine cable. As a result, less coastal land resources are occupied and the onshore transmission corridor is less occupied. After the offshore wind power lands, there is no need to build a receiving end converter station near the coast of the offshore wind farm. Only the terminal conversion station needs to be built, thereby significantly reducing the overhead line corridor, significantly improving the utilization efficiency of land space resources, and greatly reducing the land resources required near the coast of the offshore wind farm.

[0011] In some embodiments, an AC filter is configured on the grid side of the diode rectifier unit topology structure.

[0012] In some embodiments, the diode rectifier unit topology adopts a single twelve-pulse diode rectifier.

[0013] In some embodiments, the single twelve-pulse diode rectifier includes two upper and lower six-pulse units, and the AC sides of the upper and lower six-pulse units are respectively connected to a converter transformer, and the connection groups of the two converter transformers are divided into YNy0 and YNd11 connections.

[0014] In some embodiments, the offshore wind turbine generator system is a grid-type wind turbine generator system.

[0015] This application has at least the following technical effects or advantages:

[0016] 1. The offshore converter station using the diode rectifier unit topology has significant advantages such as small size, light weight, and low cost. Compared with the offshore converter station using the half-bridge or full-bridge MMC topology, the utility model can significantly reduce the loss, weight, size, and cost of the offshore converter station.

[0017] 2. The overhead line corridors have been significantly reduced, which has significantly improved the efficiency of land space resource utilization, and the land resources required near the coast of offshore wind farms have been greatly reduced.

[0018] 3. The transmission cost of onshore DC overhead lines is significantly lower than that of DC land cables and also lower than that of AC overhead lines of the same capacity.

[0019] 4. As flexible DC has reactive power support capability, the flexible DC converter unit with half-bridge MMC structure adopted in the receiving-end converter station can participate in the construction of AC power grid in the load center and improve the safe and stable operation level of the power grid. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] Figure 1 This is a structural schematic diagram of an offshore wind power DC transmission device in one embodiment of the present application;

[0021] Figure 2 Schematic diagram of the structure of a single twelve-pulse diode rectifier in one embodiment of the present application. DETAILED DESCRIPTION

[0022] In order to better understand the above technical solution, the above technical solution will be described in detail below in conjunction with the accompanying drawings and specific implementation methods.

[0023] Embodiment 1

[0024] See also Figure 1 and Figure 2 An offshore wind power DC transmission device includes: an offshore wind turbine 1, an offshore converter station 2, a terminal conversion station 3, a receiving end converter station 4 and a load center AC power grid 5. The offshore wind turbine can be a grid-forming wind turbine, and can independently construct an offshore AC power grid system.

[0025] The AC side of the offshore converter station 2 is electrically connected to the offshore wind turbine 1 through the AC collector cable 6, the DC side of the offshore converter station 2 is electrically connected to the terminal conversion station 3 through the DC cable 7, the terminal conversion station 3 is electrically connected to the receiving end converter station 4 through the DC overhead line 8, and the receiving end converter station 4 is electrically connected to the load center AC power grid 5 through the AC line 9. The terminal conversion station 3 is located near the landing point of the DC cable 7.

[0026] The receiving end converter station 4 adopts a flexible DC converter unit with a half-bridge MMC structure. The DC submarine cable 7 includes a positive and a negative DC submarine cable, and the terminal conversion station 3 includes a DC energy dissipation device 10 connected between the positive and negative DC submarine cables, which is used to perform fault crossing when the DC overhead line 8 fails. The DC overhead line 8 also includes a positive and a negative DC overhead line. A DC circuit breaker DCCB is configured on each of the positive and negative lines of the DC submarine cable 7 and the DC overhead line 8 to cut off the DC overhead line fault.

[0027] The offshore converter station 2 adopts a diode rectifier unit (DRU) topology structure, and an AC filter is configured on the grid side of the diode rectifier unit topology structure. Figure 2As shown, the diode rectifier unit topology structure can adopt a single twelve-pulse diode rectifier, including upper and lower six-pulse units. The AC sides of the upper and lower six-pulse units are respectively connected to a converter transformer, and the connection groups of the two converter transformers are divided into YNy0 and YNd11 connections.

[0028] Through the above device, the electric energy generated by the offshore wind turbine is connected to the AC side of the offshore converter station through the AC collector cable, and after being rectified into DC, it is landed through the DC submarine cable. A terminal conversion station is built near the DC submarine cable landing point to convert the DC submarine cable into a DC overhead line, which is transmitted to the receiving end converter station at the load center, and is connected to the AC power grid at the load center after being inverted into AC. The utility model has a positive effect on reducing the size and weight of the offshore converter station, reducing the investment cost of the offshore converter station, and reducing the routing of the DC land cable or AC overhead line.

[0029] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the utility model, rather than to limit it. Although the utility model has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the aforementioned embodiments, or make equivalent replacements for some of the technical features therein. However, these modifications or replacements do not deviate the essence of the corresponding technical solutions from the spirit and scope of the technical solutions of the various embodiments of the utility model.

Claims

1. An offshore wind power DC transmission device, characterized in that: include: An offshore wind turbine generator set, an offshore converter station, a terminal conversion station, a receiving-end converter station and an AC power grid at a load center; the AC side of the offshore converter station is electrically connected to the offshore wind turbine generator set via an AC collector submarine cable, the DC side of the offshore converter station is electrically connected to the terminal conversion station via a DC submarine cable, the terminal conversion station is electrically connected to the receiving-end converter station via a DC overhead line, and the receiving-end converter station is electrically connected to the AC power grid at the load center via an AC line; Among them, the offshore converter station adopts a diode rectifier unit topology structure, and the receiving-end converter station adopts a flexible DC converter unit with a half-bridge MMC structure; the terminal conversion station includes a first DC circuit breaker configured on the DC submarine cable and a DC energy consumption device connected across the DC submarine cable.

2. The offshore wind power DC transmission device according to claim 1, characterized in that: A second DC circuit breaker is arranged on the DC overhead line.

3. The offshore wind power DC transmission device according to claim 1 or 2, characterized in that: The terminal conversion station is located near the landing point of the DC submarine cable.

4. The offshore wind power DC transmission device according to claim 1 or 2, characterized in that: An AC filter is configured on the grid side of the diode rectifier unit topology structure.

5. The offshore wind power DC transmission device according to claim 1 or 2, characterized in that: The diode rectifier unit topology adopts a single twelve-pulse diode rectifier.

6. The offshore wind power DC transmission device according to claim 5, characterized in that: The single twelve-pulse diode rectifier comprises an upper and a lower six-pulse unit, the AC sides of the upper and the lower six-pulse unit are respectively connected to a converter transformer, and the connection groups of the two converter transformers are divided into YNy0 and YNd11 connections.

7. The offshore wind power DC transmission device according to claim 1 or 2, characterized in that: The offshore wind turbine generator set is a grid-type wind turbine generator set.

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