Modular multilevel converter valve tower structure and intermediate frequency MMC converter valve

Abstract

The invention discloses a modular multi-level converter valve tower structure and an intermediate frequency MMC converter valve, the valve tower structure comprises at least one valve layer and an insulator used for supporting the valve layer, the valve layer is formed by connecting a plurality of valve sections in series, each valve section is formed by cascading a plurality of sub-modules, and each sub-module comprises a power unit; the valve layer comprises three rows of valve sections, the three rows of valve sections are arranged in parallel, power units in the first row of valve sections and the third row of valve sections are oppositely arranged, and the second row of valve sections are arranged between the first row of valve sections and the third row of valve sections; a first maintenance platform is arranged between the first column valve section and the second column valve section, and a second maintenance platform is arranged between the second column valve section and the third column valve section; the first column valve section inlet sub-module or the third column valve section inlet sub-module is connected with a valve layer inlet wire, and the second column valve section outlet sub-module is connected with a valve layer outlet wire. The power density of the valve tower can be improved, and the development requirement of a modern electric power system is met.

Description

Technical Field

[0001] This invention belongs to the field of power transmission equipment technology, and particularly relates to a modular multilevel converter valve tower structure and a medium-frequency modular multilevel converter (MMC) converter valve, which is especially suitable for offshore wind power transmission applications. Background Technology

[0002] In the field of modern power transmission, modular multilevel converter (MMC) valves are key components, playing a vital role in high-voltage direct current (HVDC) transmission and flexible alternating current transmission systems (FACTS). MMC valves achieve power conversion and transmission through the cascading of multiple sub-modules, and the design of their valve tower structure has a crucial impact on the valve's performance, ease of maintenance, and power density.

[0003] Currently, the existing MMC converter valve tower structure typically adopts a two-row encircling form with a maintenance passage in the middle to facilitate the inspection and maintenance of submodules. This structure meets basic usage requirements to a certain extent, but as the performance requirements of power systems for converter valves continue to increase, its limitations are becoming increasingly apparent. The main limitation is the insufficient space utilization of the two-row encircling structure, making it difficult to further increase the number of submodules within a limited space.

[0004] In addition, with the deepening of research on intermediate frequency technology, the capacitance and size of sub-modules have been greatly reduced, and the valve tower with two rows of encircling structures has been reduced in size in one dimension. However, due to the limitation that the valve tower structure cannot accommodate more sub-modules, the overall size reduction is not significant. Summary of the Invention

[0005] The purpose of this invention is to provide a modular multilevel converter valve tower structure and a medium-frequency MMC converter valve, which can improve the power density of the valve tower and meet the development needs of modern power systems.

[0006] To achieve the above objectives, the solution of the present invention is:

[0007] A modular multilevel converter valve tower structure is disclosed. The valve tower structure includes at least one valve layer and insulators for supporting the valve layer. The valve layer is composed of multiple valve segments connected in series, and each valve segment is composed of multiple sub-modules cascaded together. Each sub-module includes a power unit. The valve layer contains three rows of valve segments arranged in parallel. The power units in the first and third rows of valve segments are arranged opposite each other, and the second row of valve segments is arranged between the first and third rows of valve segments. A first maintenance platform is provided between the first and second rows of valve segments, and a second maintenance platform is provided between the second and third rows of valve segments. A sub-module at the inlet of the first or third row of valve segments is connected to the valve layer inlet line, and a sub-module at the outlet of the second row of valve segments is connected to the valve layer outlet line.

[0008] The valve tower structure described above includes multiple valve layers. In odd-numbered valve layers, the second column of valve segments is arranged in the forward direction, and in even-numbered valve layers, the second column of valve segments is arranged in the reverse direction. Specifically, in the forward arrangement of the second column of valve segments, the power unit of the second column of valve segment submodule faces the first column of valve segments, and in the reverse arrangement of the second column of valve segments, the power unit of the second column of valve segment submodule faces the third column of valve segments.

[0009] The electrical connection sequence of the above-mentioned odd-numbered valve layers is as follows: the valve layer inlet line is connected to the submodule at the inlet of the third column valve section; the submodule at the outlet of the third column valve section is connected to the submodule at the inlet of the first column valve section; the submodule at the outlet of the first column valve section is connected to the submodule at the inlet of the second column valve section; and the submodule at the outlet of the second column valve section is connected to the valve layer outlet line.

[0010] The electrical connection sequence of the above even-numbered valve layers is as follows: the valve layer inlet line is connected to the first column valve section inlet submodule; the first column valve section outlet submodule is connected to the third column valve section inlet submodule; the third column valve section outlet submodule is connected to the second column valve section inlet submodule; and the second column valve section outlet submodule is connected to the valve layer outlet line.

[0011] All sub-modules of the aforementioned valve section are located within the valve section frame. The AC terminals of each sub-module are cascaded sequentially, and the AC terminal of the outermost sub-module adjacent to the valve section frame is equipotentially connected to the valve section frame.

[0012] The second valve section mentioned above includes a valve section frame that can accommodate N sub-modules. Nn sub-modules are arranged in the valve section frame starting from the side away from the valve layer outlet line, and a maintenance channel for connecting the first maintenance platform and the second maintenance platform is provided in the empty position on the side near the valve layer outlet line. N and n are natural numbers and N>n.

[0013] The valve segment frame is connected to the first column of valve segments on the side closest to the valve layer outlet; wherein, if the valve layer where the first column of valve segments is located is an odd-numbered layer, the valve segment frame of the second column of valve segments is connected to the inlet module of the first column of valve segments; if the valve layer where the first column of valve segments is located is an even-numbered layer, the valve segment frame of the second column of valve segments is connected to the outlet module of the first column of valve segments.

[0014] An insulation distance is provided between the submodule at the outlet of the second column valve section and the valve section frame.

[0015] The aforementioned submodule also includes a capacitor unit, which can be separated from the power unit.

[0016] A medium-frequency modular multilevel converter (MMC) converter valve, the medium-frequency MMC converter valve including the modular multilevel converter valve tower structure as described above.

[0017] The fundamental AC component of the current flowing through the submodule of the valve tower structure is 100Hz to 500Hz.

[0018] By adopting the above solution, the present invention provides a compact converter valve tower structure, which performs well in terms of power density improvement, maintenance convenience, and technical adaptability.

[0019] (1) Increased power density: By adopting a three-row parallel valve section structure, the space utilization rate is greatly improved compared to the traditional two-row ring structure. More sub-modules can be arranged in a limited space, thereby effectively increasing the power density of the valve tower and meeting the needs of modern power systems for high-capacity and high-efficiency power transmission.

[0020] (2) Optimize maintenance convenience: Two maintenance platforms are set up, and a maintenance passage is set up on the side of the valve layer outlet in the second valve section, so that maintenance personnel can more easily access each sub-module for maintenance and repair. At the same time, the design of the sub-module power unit and capacitor unit can be separated, which further reduces the difficulty of maintenance, shortens the maintenance time, reduces equipment downtime, and reduces operation and maintenance costs.

[0021] (3) Adapting to technological development: With the development of medium frequency technology and the compression of the capacitance and size of sub-modules, the multi-row valve tower structure of the present invention can better utilize the space advantage brought about by the reduction of sub-module size, further optimize the valve tower layout, have greater potential in terms of overall size reduction, and better adapt to the trend of continuous development of power technology. Attached Figure Description

[0022] Figure 1 An electrical schematic diagram of a converter valve in the prior art is shown;

[0023] Figure 2 This illustrates the structure of a ring-type converter valve tower in the prior art;

[0024] Figure 3 The multi-row valve layer structure proposed in this invention is shown;

[0025] Figure 4 This invention illustrates an even-numbered multi-column valve layer structure.

[0026] Figure 5 This invention illustrates an odd-numbered multi-row valve layer structure with maintenance access proposed in this invention;

[0027] Figure 6 This invention demonstrates the optimization of the present invention in terms of floor space compared to the prior art;

[0028] Wherein, (a) is a single bridge arm of an MMC converter, (b) is a single bridge arm of a medium-frequency MMC converter, and (c) is a single bridge arm of a medium-frequency MMC converter of the present invention.

[0029] Reference numerals: 1-valve layer, 2-valve section, 10-submodule, 20-valve section frame, 30-valve section insulating beam, 40-maintenance platform, 41-maintenance passage, 50-valve layer inlet line, 60-valve layer outlet line, 101-power unit, 102-capacitor unit. Detailed Implementation

[0030] This invention provides a modular multilevel converter valve tower structure, based on the physical form of an MMC converter, and in conjunction with... Figure 1 and Figure 2 As shown, it includes at least one valve layer 1 and an insulator for supporting the valve layer 1. Each valve layer 1 is composed of multiple valve segments 2 connected in series, and each valve segment 2 is composed of multiple half-bridge and / or full-bridge sub-modules 10 cascaded together. The sub-module 10 mainly consists of a power unit 101 and a capacitor unit 102.

[0031] The improvement of this invention is as follows: Figure 3 As shown, this embodiment of the invention employs a unique valve layer layout, with the valve layer using a parallel structure of three rows of valve sections. Specifically, the power units of the submodules in the first and third rows of valve sections are arranged face-to-face, and the second row of valve sections is positioned between these two rows. A first maintenance platform 40 is provided between the first and second rows of valve sections, and a second maintenance platform 40 is provided between the second and third rows of valve sections. The valve layer inlet line 50 connects to the submodule at the inlet of either the first or third row of valve sections, while the valve layer outlet line 60 connects to the submodule at the outlet of the second row of valve sections.

[0032] To adapt to the application requirements of multi-layer valves, the valve arrangement has been further optimized: the second row of valves can be arranged in two ways: forward and reverse. A forward arrangement means the power units of the second row of valve submodules face the first row of valves, while a reverse arrangement means the power units of the submodules face the third row of valves. When the converter valve tower contains multiple valve layers, odd-numbered valve layers are set to a forward arrangement in the second row of valves, and even-numbered valve layers are set to a reverse arrangement in the second row of valves, using an alternating arrangement of odd and even-numbered valve layers.

[0033] The electrical connection sequence covers different valve layers: For odd-numbered valve layers: the electrical connection sequence is as follows: the valve layer incoming line connects to the submodule at the inlet of the third valve segment; from the submodule at the outlet of the third valve segment, it connects to the submodule at the inlet of the first valve segment; then from the submodule at the outlet of the first valve segment, it connects to the submodule at the inlet of the second valve segment; finally, from the submodule at the outlet of the second valve segment, it connects to the valve layer outgoing line. For even-numbered valve layers: the electrical connection sequence is as follows: the valve layer incoming line connects to the submodule at the inlet of the first valve segment; from the submodule at the outlet of the first valve segment, it connects to the submodule at the inlet of the third valve segment; then from the submodule at the outlet of the third valve segment, it connects to the submodule at the inlet of the second valve segment; finally, from the submodule at the outlet of the second valve segment, it connects to the valve layer outgoing line.

[0034] The invention also specifies the connection details, including equipotential connection between the valve section frame and one of the AC terminals of the adjacent submodule, with the AC terminals of each submodule cascaded in sequence.

[0035] To further facilitate inspection and maintenance, this invention leaves one or more sub-modules vacated on the valve layer outlet side of the second valve section. A maintenance passage 41 is provided at the vacated location, connecting the first and second maintenance platforms. This allows maintenance personnel to freely move between the first and second maintenance platforms on the same valve layer and access different valve layers via vertical ladders. Simultaneously, the valve section frame 20 on the valve layer outlet side of the second valve section is no longer connected to the AC ports of adjacent sub-modules, but instead connects to the inlet module (odd-numbered layers) or outlet module (even-numbered layers) of the first valve section. Furthermore, the outlet module of the second valve section maintains a certain insulating distance from the adjacent frame.

[0036] To facilitate operation, maintenance, and repair, the power unit and capacitor unit of the submodule are designed as separable structures, which facilitate individual maintenance and transportation.

[0037] To make the objectives, technical solutions, and advantages of this invention clearer, the specific embodiments of this invention will be described in detail below with reference to the accompanying drawings. In the description, the principles of comprehensiveness, accuracy, and ease of understanding will be followed so that those skilled in the art can fully grasp the core points and implementation details of this invention.

[0038] Taking a flexible DC converter valve with ±500kV / 3000MW as an example, the implementation effect of the present invention is demonstrated.

[0039] The converter valve tower is equipped with multiple valve layers 1, in conjunction with... Figure 3 As shown, each valve layer 1 is securely supported by insulators. Each valve layer 1 adopts the three-row parallel valve section structure proposed in this invention. In selecting insulators, insulators with high insulation performance and mechanical strength were chosen to ensure electrical insulation between valve layers and the stability of the entire valve tower structure.

[0040] Each valve section 2 is composed of multiple cascaded sub-modules 10. The sub-modules 10 are mounted on the valve section insulating beam 30. The sub-modules 10 utilize a mix of half-bridge and full-bridge sub-modules to meet power transmission requirements. The power units 101 of the sub-modules in the first and third valve sections are installed in a strictly relative arrangement, with the second valve section positioned in the middle. For the second valve section, in odd-numbered valve layers, the sub-module power units face the first valve section; in even-numbered valve layers, the sub-module power units face the third valve section, in coordination with... Figure 4 As shown, the staggered arrangement of odd-numbered valve layers and even-numbered valve layers is achieved.

[0041] During the arrangement of sub-modules, the electrical clearance between each sub-module is strictly controlled to ensure that the insulation requirements under the 500kV voltage level are met. At the same time, a compact arrangement is adopted to maximize space utilization.

[0042] The electrical connections for odd-numbered valve layers strictly follow this sequence: valve layer inlet line 50 connects to the submodule at the inlet of the third valve segment; from the submodule at the outlet of the third valve segment, it connects to the submodule at the inlet of the first valve segment; then from the submodule at the outlet of the first valve segment, it connects to the inlet of the second valve segment; finally, from the outlet of the second valve segment, it connects to the valve layer outlet line 60. The electrical connection sequence for even-numbered valve layers is similar, starting with the valve layer inlet line connecting to the submodule at the inlet of the first valve segment, and sequentially connecting the submodules between each valve segment to the valve layer outlet line 60.

[0043] The valve section frame 20 is equipotentially connected to one of the AC terminals of the adjacent submodule via a copper busbar, ensuring stable electrical performance. The valve tower is equipped with a maintenance passage 41 for a double-row maintenance platform 40: On the second row of valve sections near the valve layer outlet, two submodules are left vacant based on actual maintenance space requirements, and a maintenance passage is built in the vacant area, connecting the first and second maintenance platforms. The valve section frame on the second row of valve sections near the valve layer outlet is designed not to connect to the AC ports of adjacent submodules. It connects to the inlet module of the first row of valve sections on odd-numbered floors and to the outlet module of the first row of valve sections on even-numbered floors. Simultaneously, the outlet module of the second row of valve sections maintains sufficient insulation distance from the adjacent frame to ensure electrical safety.

[0044] The power unit and capacitor unit of the submodule are designed for easy disassembly. In actual maintenance, maintenance personnel can easily separate the two for separate maintenance and transportation, which improves maintenance efficiency.

[0045] When the AC side frequency is 50Hz, such as Figure 6 As shown in (a), the single bridge arm occupies an area of ​​177.6m². 2 The converter valve, comprising six bridge arms, has a total area of ​​1644.4 m². 2 The double-headed arrows indicate the insulation distance; when the AC side frequency is increased to 150Hz, such as Figure 6 As shown in (b), the single bridge arm occupies an area of ​​139m². 2 (Reduced by 21.7%), converter valve area 1412.8m² 2 (Reduced by 14.08%); The valve tower structure proposed in this invention, such as... Figure 6 As shown in (c), the single bridge arm occupies an area of ​​129m². 2 (Reduced by 27.4%), converter valve area 1145.8m² 2 (Reduced by 30.3%), it has a clear advantage in terms of land area.

[0046] Through the above specific implementation methods, this invention significantly improves the power density of the valve tower, arranges more sub-modules within a limited space, and meets the demand for higher capacity power transmission; it greatly optimizes maintenance convenience, allowing maintenance personnel to quickly reach the location of each sub-module through dual maintenance platforms and maintenance channels, and the separable design of the sub-modules further shortens maintenance time and reduces operation and maintenance costs; it better adapts to the development trend of medium frequency technology, optimizes the layout by utilizing the advantage of reduced sub-module size, and achieves significant results in reducing the overall size; it ensures stable electrical performance, and the reasonable electrical connection and valve section frame connection method reduces the probability of electrical faults and improves the operational stability of the converter valve.

[0047] This invention also provides a medium-frequency modular multilevel converter (MMC) converter valve, which includes the modular multilevel converter valve tower structure described above, wherein the fundamental AC component of the current flowing through the sub-module in the valve tower structure is 100Hz to 500Hz.

[0048] Although the preferred embodiments of the present invention have been described, those skilled in the art may make additional changes and modifications to these embodiments once they have learned the basic creative concept. Therefore, the appended claims are intended to be interpreted as including the preferred embodiments and all changes and modifications that fall within the scope of the present invention.

[0049] Obviously, those skilled in the art can make various modifications and variations to this invention without departing from its spirit and scope. Therefore, if these modifications and variations fall within the scope of the claims of this invention and their equivalents, this invention also intends to include these modifications and variations.

Claims

1. A modular multilevel converter valve tower structure, the valve tower structure comprising at least one valve layer and insulators for supporting the valve layer, the valve layer being composed of multiple valve sections connected in series, each valve section being composed of multiple sub-modules cascaded, each sub-module comprising a power unit; characterized in that: The valve layer comprises three rows of valve sections arranged in parallel. The power units in the first and third rows of valve sections are arranged face-to-face, and the second row of valve sections is located between the first and third rows of valve sections. A first maintenance platform is provided between the first and second rows of valve sections, and a second maintenance platform is provided between the second and third rows of valve sections. The submodule at the inlet of the first or third row of valve sections is connected to the valve layer inlet line, and the submodule at the outlet of the second row of valve sections is connected to the valve layer outlet line.

2. The modular multilevel converter valve tower structure as described in claim 1, characterized in that: The valve tower structure includes multiple valve layers. In odd-numbered valve layers, the second column of valve segments is arranged in the forward direction, and in even-numbered valve layers, the second column of valve segments is arranged in the reverse direction. Specifically, in the forward arrangement of the second column of valve segments, the power unit of the second column of valve segment submodule faces the first column of valve segments, and in the reverse arrangement of the second column of valve segments, the power unit of the second column of valve segment submodule faces the third column of valve segments.

3. The modular multilevel converter valve tower structure as described in claim 2, characterized in that: The electrical connection sequence of the odd-numbered valve layers is as follows: the valve layer inlet line is connected to the third column valve section inlet submodule; the third column valve section outlet submodule is connected to the first column valve section inlet submodule; the first column valve section outlet submodule is connected to the second column valve section inlet submodule; and the second column valve section outlet submodule is connected to the valve layer outlet line.

4. The modular multilevel converter valve tower structure as described in claim 2, characterized in that: The electrical connection sequence of the even-numbered valve layers is as follows: the valve layer inlet line is connected to the first column valve section inlet submodule; the first column valve section outlet submodule is connected to the third column valve section inlet submodule; the third column valve section outlet submodule is connected to the second column valve section inlet submodule; and the second column valve section outlet submodule is connected to the valve layer outlet line.

5. The modular multilevel converter valve tower structure as described in claim 1, characterized in that: All sub-modules of the valve section are located in the valve section frame. The AC terminals of each sub-module are cascaded in sequence, and the AC terminal of the outermost sub-module adjacent to the valve section frame is equipotentially connected to the valve section frame.

6. The modular multilevel converter valve tower structure as described in claim 1, characterized in that: The second valve section includes a valve section frame capable of accommodating N sub-modules. Nn sub-modules are arranged in the valve section frame starting from the side away from the valve layer outlet, and a maintenance channel for connecting the first maintenance platform and the second maintenance platform is provided in the empty position on the side near the valve layer outlet. N and n are natural numbers and N>n.

7. The modular multilevel converter valve tower structure as described in claim 6, characterized in that; The valve segment frame is connected to the first column of valve segments on the side near the valve layer outlet; wherein, if the valve layer where the first column of valve segments is located is an odd-numbered layer, the valve segment frame of the second column of valve segments is connected to the inlet module of the first column of valve segments; if the valve layer where the first column of valve segments is located is an even-numbered layer, the valve segment frame of the second column of valve segments is connected to the outlet module of the first column of valve segments.

8. The modular multilevel converter valve tower structure as described in claim 6, characterized in that; An insulation distance is provided between the submodule at the outlet of the second column valve section and the valve section frame.

9. The modular multilevel converter valve tower structure as described in claim 1, characterized in that; The submodule also includes a capacitor unit, which can be separated from the power unit.

10. A medium-frequency modular multilevel converter (MMC) converter valve, characterized in that: The medium-frequency MMC converter valve includes the modular multilevel converter valve tower structure as described in any one of claims 1 to 9.

Images