Converter Valve Assembly

Abstract

Disclosed herein is a converter valve assembly (20) for a power grid system, comprising two or more equal groups (6a, 6b, 6c) of prismatic converter cells (3a-j), each group (6a, 6b, 6c) arranged in a respective plane (7a, 7b, 7c) of a plurality of parallel planes spaced apart along a horizontal axis (8). The converter cells (3a-j) in a group (6a) are connected in series, and the groups (6a, 6b, 6c) are connected in series along the axis (8). The prismatic converter cells (3a-j) in a group (6a) are arranged such that, during operation of the converter valve assembly (20), a corresponding voltage difference exists between each converter cell (3a-j) in the group (6a) and its corresponding converter cell (3k-t) in the adjacent group (6b) that is spatially closest to the converter cell (3a-j). Therefore, spacing between the groups can be reduced, thereby reducing the overall volume of the converter valve assembly.

Description

[Technical Field]

[0001] The present disclosure relates to power systems, and more particularly to converter valve assemblies for power grid systems and methods for manufacturing converter valve assemblies.

[0002] background Power distribution networks include converters that are operated to convert an input power supply voltage (e.g., from a power generation means such as a wind turbine) into an output grid voltage for distribution to the power grid. In some cases, the converters can also convert an alternative current (AC) input to a direct current (DC) output, e.g., for a high-voltage DC (HVDC) portion of the power grid, or vice versa, e.g., for an AC portion of the power grid.

[0003] The converter comprises valve assemblies (also called "valves"), each of which comprises multiple converter cells. Each converter cell typically comprises a full-bridge or half-bridge inverter circuit and contributes a unit of voltage toward the converter's total possible output voltage. The number of valve assemblies and / or converter cells may be selected based on the output voltage required for the converter.

[0004] These valve assemblies are typically housed in valve holes. In high-voltage applications, such as power grid applications, high voltages may be present within the valve holes, and it is therefore important to ensure that the risk of electrical arcing within the valve holes is contained. Furthermore, the size of the valve holes may be limited. This is particularly true for offshore wind, where the cost per unit volume of offshore platforms is typically much higher than for onshore valve holes. Therefore, the valve assemblies may need to be arranged as close together as possible.

[0005] Taking these limitations into account, it is desirable to optimize the arrangement of converter valves within the valve hole.

[0006] overview As part of this disclosure, it is recognized that optimized, or at least improved, converter valve arrangements may be achieved at least in part by improving the relative arrangement of converter cells to reduce or equalize voltage differences between spatially adjacent components, and the term "spatially" is used to distinguish from "electrically" adjacent components.

[0007] Each converter cell in the valve assembly is connected in series and has the same voltage unit V for the total converter output voltage. cell Each converter cell can be thought of as contributing a V to the previous converter cell connected in series with it. cell There is a voltage difference ΔV.

[0008] As part of this disclosure, it is recognized that when determining the spatial arrangement of the converter cells, it is preferable to minimize this ΔV in order to reduce the risk of electrical arcing between the converter cells and to allow the converter cells to be arranged as close to each other as possible, thereby minimizing (or at least reducing) the overall volume of the valve assembly.

[0009] Additionally, it is recognized as part of this disclosure that uniform distribution of voltage differences between spatially adjacent converter cells also reduces the risk of electrical arcing between converter cells within the valve assembly.

[0010] Thus, according to one aspect of the present disclosure, a converter valve assembly for a power grid system is provided that includes two or more equal groups of prismatic converter cells. That is, each group (or at least two groups) of prismatic converter cells in the converter valve assembly includes the same number N of prismatic converter cells. As used herein, a "prismatic" converter cell is a converter cell having a three-dimensional form factor having a length, a width, and a height, and including a pair of parallel faces separated by the shortest dimension of the length, width, and height. For example, the prismatic form factor may include a rectangular parallelepiped form factor, a triangular prism form factor, or a cylindrical form factor.

[0011] Each of the two or more groups is arranged (i.e., spatially arranged) in a respective one of a plurality of parallel planes spaced apart along a horizontal axis. The converter cells may be arranged and held in place by any suitable support structure, preferred configurations of such support structures are described below.

[0012] It will be appreciated that the "plane" in which the converter cells are arranged may be defined after and only by said arrangement, i.e., two or more converter cells may be arranged relative to one another such that a plane is defined that intersects all of said two or more converter cells.

[0013] Moreover, although reference is made to "parallel" planes, it will be understood that some tolerance outward from perfect parallelism is acceptable without significantly degrading the advantageous properties of the converter valve arrangement of the present disclosure.

[0014] Advantageously, more groups can be included in a converter valve arrangement so that the converter valve assembly can comprise an entire arm of the converter by arranging the groups in a plane along a horizontal axis. As used herein, it will be understood that a "horizontal" axis refers to an axis that is substantially perpendicular to the action of gravity.

[0015] Thus, by arranging the groups along a horizontal axis, a single structure can be formed, eliminating the need for additional spacing between multiple structures. Furthermore, all level points on such a single structure will be subject to the same gravitational stresses, and therefore it is advantageously simple to scale such converter valve assemblies without adapting support structures, as may be required, for example, for vertical structures that may be subject to increased gravitational stresses at higher levels as more groups are added.

[0016] The converter cells within a group are (electrically) connected in series with each other. The electrical connection between the converter cells may be performed by any suitable means, and the groups are then connected in series, for example along an axis, using similar such means for electrical connection.

[0017] In some examples, the converter cells may be arranged with their shortest dimension perpendicular to the plane. The shortest dimension of a prismatic converter cell may be either the length, width, or height of the three-dimensional converter cell having the smallest dimension. For example, if the converter cells have a cubic form factor with a length of 30 centimeters (cm), a width of 20 cm, and a height of 10 cm, the converter cells according to the converter valve assembly of the present disclosure are arranged with their height perpendicular to the plane, i.e., the plane defined by the relative arrangement of the converter cells. In this example, the length and width of the converter cells extend parallel to the plane.

[0018] The relative arrangement of converter cells in a plane with respect to other groups in parallel planes can be advantageously configured to normalize voltage differences between the planes of each group, such that the prismatic converter cells in a group are arranged such that, during operation of the converter valve assembly, there is a corresponding voltage difference (i.e., the same or substantially similar) between each converter cell in a group and each corresponding converter cell in its spatially nearest adjacent group.

[0019] Viewed another way, each converter cell in a group has a corresponding converter cell in an adjacent group that is spatially closest to said converter cell, and the voltage difference between each converter cell in a group and its corresponding converter cell in an adjacent group is the same during operation of the converter valve assembly. That is, the prismatic converter cells in a group are arranged such that there is a corresponding voltage difference between any pair of converter cells, the first converter cell of the pair being the converter cell of said group, and the second converter cell of the pair being the corresponding converter cell in an adjacent group that is spatially closest to said first converter cell during operation of the converter valve assembly.

[0020] Such an arrangement may be achieved, for example, by connecting each group in series from the first converter cell to the last converter cell of the group according to a cell arrangement common to all groups, in which case the last converter cell of a group may be connected to the first converter cell of an adjacent group.

[0021] The distance between different groups of converter cells arranged in different adjacent planes can be determined based at least in part on the risk of electrical arc discharge between conductors in different groups having different potential differences. (For example, during operation of a converter valve assembly), the greater the potential difference between conductors, the greater the distance to be provided between the conductors to reduce the said risk of electrical arc discharge between the conductors.

[0022] Thus, during operation of a converter valve assembly, by arranging and configuring the converter cells such that there is a corresponding voltage difference (i.e., the same or substantially the same) between each converter cell within a group and each corresponding converter cell within the adjacent group that is spatially closest to the said each converter cell, the distance between adjacent groups can be reduced (or optimized), and space is not wasted within the converter valve assembly.

[0023] Furthermore, by arranging and configuring the converter cells such that the shortest dimension of the converter cell is perpendicular to the plane, it can be ensured that the distance between groups (along an axis perpendicular to the plane) is less restricted by the dimensions of the converter cell itself. For example, the distance S may be determined based on the voltage difference between converter cells in adjacent groups, and this voltage difference may be substantially the same and uniform across the entire plane in which the converter cells are arranged and configured.

[0024] For example, the distance S may be the minimum distance between groups that reduces the risk of electrical arc discharge between the said groups. The distance S may be less than the longest dimension L of the converter cell such that H < S < L, provided that it is greater than the shortest dimension H of the converter cell. Thus, by arranging and configuring the converter cell with the shortest dimension H perpendicular to the plane, the distance between groups (i.e., between planes) can be reduced based on electrical rather than spatial limitations.

[0025] However, it will be appreciated that the second shortest dimension (such as width W) of the converter cell can also satisfy W < S < L. That is, the converter cells may be arranged in a dimension smaller than their longest dimension parallel to the plane and still benefit from the advantageous effects of the present method.

[0026] By optimizing the volume occupied by the converter valve assembly, the overall footprint of the converter station can be reduced. This can be particularly beneficial when the converter station is installed in an offshore wind facility due to the very high costs and space limitations associated with such installations.

[0027] In some examples, the cell arrangement may be, for example, a helical arrangement when viewed with respect to the electrical connections between cells within a group and between groups, for example, a horizontal helix where the axis of the helix extends horizontally. In other words, the cell arrangement can include arranging the converter cells within a group around an axis and connecting the converter cells within the group in order according to their radial positions around the axis, thereby forming an open loop from the first converter cell to the last converter cell of the group. Each open loop can be viewed as forming a helical-shaped "turn".

[0028] According to such an arrangement, the conductors used to connect the cells within a group and interconnect the groups can be shortened. Further, the electromagnetic field configuration during the operation of the converter valve assembly can be made more uniform, for example, to further reduce the risk of electric arc discharge along the path of a concentrated electric field.

[0029] Furthermore, according to some examples, each converter cell within a group may be positionally aligned with a corresponding converter cell in an adjacent group, and the corresponding converter cells have the same position within the cell arrangement.

[0030] Therefore, not only is the spacing along the axis reduced, but also perpendicular to the axis, so the overall volume of the converter valve assembly can be further reduced, thereby reducing or minimizing the absolute distance between corresponding pairs of converter cells (having the same respective positions within the arrangement).

[0031] As discussed above, the parallel planes may be spaced apart along the axis by a distance corresponding to the voltage difference between each converter cell in a group and each corresponding converter cell in an adjacent group, i.e., a minimum "safe" distance may be calculated based on the voltage difference between corresponding converter cells in adjacent groups, and the groups may be spaced apart by this minimum safe distance, thereby reducing the overall volume of the converter valve assembly.

[0032] As part of this disclosure, it is understood that seismic-related events, such as earthquakes, pose significant risks to converter valve assemblies. Thus, according to some examples, each group may be rigidly mounted to its respective substructure. Thus, during a seismic-related event, converter cells within the same group are prevented from moving relative to each other, thereby reducing the risk of electrical arcing within the group or adversely affecting the operation of the group of converter cells.

[0033] According to some further examples, each substructure can be rigidly connected along an axis, thereby forming a support structure for the converter valve assembly. Therefore, during an earthquake-related event, different groups are prevented from moving relative to each other, thereby reducing the risk of electrical arcing between groups or otherwise adversely affecting the operation of the converter valve assembly. The substructures may be rigidly connected by insulating members to further enhance electrical isolation between groups.

[0034] The converter valve assembly may further include a mounting assembly for a support structure. The mounting assembly may include a suspension assembly for suspending the support structure from a ceiling or a stand assembly for elevating the support structure from the floor.

[0035] By suspending the support structure from the ceiling of the valve hall, earthquake-related events can pose less risk to the structure of the converter valve assembly because seismic motion can be absorbed or mitigated by swaying or other compensating motion of the suspended support structure.

[0036] On the other hand, if the support structure is attached to a stand assembly, installation may be simplified and access to the converter valve assembly may be improved.

[0037] Such a stand assembly may include multiple posts configured to provide electrical isolation from the floor, and each substructure may be mounted to a respective one or more posts, or alternatively, multiple substructures may be mounted via a common mounting structure.

[0038] To reduce the risk of electrical arcing or other electromagnetic interference between the converter valve assembly and external hazards (e.g., walls, pillars, other electrical components, etc.), a shielding structure such as a corona shield may be provided.

[0039] According to some examples, the shielding structures may be provided in groups arranged in a plane, which may advantageously reduce the overall amount of shielding required to shield the converter valve assembly from the external environment, and vice versa.

[0040] In a preferred embodiment, the converter valve assembly can constitute an arm of the converter. That is, two or more groups of converter cells that make up the converter valve assembly can include all of the converter cells in an entire arm of the converter. Thus, the arm can advantageously be formed as a single unit and thus have a single structure. Compared to comparative examples in which multiple separate structures, each forming a "sub-arm," are used to constitute the converter arm, a system that is advantageously robust is provided, particularly with respect to earthquake-related events. The converter can be, for example, a modular multilevel converter configured to supply power to a power grid.

[0041] According to a further aspect of the present disclosure, there is provided a method of manufacturing a converter valve assembly substantially as described above, the method including arranging two or more equal groups of prismatic converter cells, each group arranged in a respective one of a plurality of parallel planes spaced apart along an axis, such that as a result of such arrangement, the converter cells within a group are connected in series, each group being connected in series along the axis, and the arrangement of the prismatic converter cells within a group is configured such that, during operation of the converter valve assembly, a corresponding voltage difference exists between each converter cell within a group and each corresponding converter cell in an adjacent group that is spatially closest to said converter cell.

[0042] The method can be carried out by any manual or automated means, such as the use of a computer-controlled manipulator, which can provide greater precision than can be achieved manually.

[0043] In any event, it will be appreciated that providing a converter valve assembly formed as a series of parallel planes that can be spaced apart from one another according to a voltage difference common to all corresponding pairs of converter cells in adjacent groups provides many advantages, some of which have been described above and some of which will become apparent below in further description of particular embodiments of the present disclosure.

[0044] BRIEF DESCRIPTION OF THE DRAWINGS One or more embodiments will now be described, by way of example only, and with reference to the accompanying drawings. [Brief explanation of the drawings]

[0045] [Figure 1] FIG. 1 is an electrical schematic diagram of an exemplary modular multilevel converter (MMC). [Figure 2] FIG. 2 is an electrical schematic diagram of an exemplary converter cell configured as a full-bridge sub-module. [Figure 3] 1 is a schematic perspective view of a prismatic converter cell according to an embodiment of the present disclosure; [Figure 4a] FIG. 1 is a perspective view of a portion of a prior art converter valve assembly. [Figure 4b] FIG. 1 is a top view of a portion of a prior art converter valve assembly. [Figure 5a] FIG. 1 is an exploded perspective view of a converter valve assembly according to one embodiment of the present disclosure. [Figure 5b] FIG. 5b is a top view of one of the group of converter cells shown in FIG. 5a. [Figure 6] FIG. 1 is a perspective view of a converter valve assembly according to one embodiment of the present disclosure. [Figure 7] FIG. 1 is a perspective view of a converter valve assembly having a shield structure and a mounting assembly according to one embodiment of the present disclosure. [Figure 8a]10A-10C illustrate possible alternative configurations of a mounting assembly according to an embodiment of the present disclosure. [Figure 8b] 10A-10C illustrate possible alternative configurations of a mounting assembly according to an embodiment of the present disclosure. [Figure 9] FIG. 2 is a perspective view of a portion of a support structure for a converter valve assembly according to one embodiment of the present disclosure. [Figure 10] FIG. 1 is a perspective view of a converter valve assembly that forms an arm of a converter according to one embodiment of the present disclosure. [Figure 11] 1 illustrates, as an exemplary step flow, a method for manufacturing a converter valve assembly according to one embodiment of the present disclosure. DETAILED DESCRIPTION OF THE INVENTION

[0046] Detailed Description The present disclosure will now be described with some illustrative examples, which it will be understood are provided for purposes of illustration and description only and are not intended to limit the scope of the present disclosure.

[0047] The use of the same reference number in different figures may indicate that the referenced component or element is the same or similar, at least in terms of function, in the different figures, and therefore, a discussion of such the same or similar component or element may not be repeated with respect to all figures in which the component or element appears.

[0048] 1 shows an electrical diagram of an exemplary modular multilevel converter (MMC) 1. The MMC 1 may act as a voltage source converter for a power grid and accepts a source voltage V, which may be alternating current (AC) or direct current (DC). S , the grid voltage V, which may be AC ​​or DC gFor example, the power grid in which the MMC1 is installed may be a high-voltage DC (HVDC) power grid.

[0049] Power supply voltage V S may come from any suitable source of generated and / or stored electrical energy. For example, a power supply voltage V S may be supplied from one or more wind turbines and / or one or more energy storage systems comprising storage capacitors and / or batteries. g can have a predetermined magnitude and frequency based on the desired characteristics of the power grid in which the MMC1 is installed. Thus, the MMC1 can be g The illustrated MMC1 can be operated to provide a voltage source in accordance with these desired characteristics of the grid voltage V g as (n approximate) sine waves with frequency and amplitude.

[0050] The MMC 1 includes a plurality of arms 2a, 2b, and 2c, which may be collectively or generally referred to as "arms 2." Each arm 2 is connected to an output grid voltage V S Different phases of V a , V b , V c As a result, the three arms 2 are connected to the three-phase grid voltage V g , with each phase separated by substantially 120 degrees phase.

[0051] Each arm 2 of the MMC 1 comprises a number of converter cells 3, sometimes referred to as "sub-modules 3." Each converter cell 3 comprises a half-bridge or full-bridge switching circuit arranged around a capacitor. An example of a full-bridge converter cell 3 is shown in Figure 2, where a number of semiconductor switches 4 are arranged in a full-bridge configuration around a capacitor 5.

[0052] Therefore, each converter cell 3 can be switched on and off according to a switching pattern through coordinated control of the semiconductor switches 4 of each converter cell 3, resulting in a total grid voltage V S For contribution to the capacitor 5 can be discharged in either a positive or negative direction.

[0053] Each converter cell 3, or at least several converter cells 3, can be configured with similar capacitors 5 so that each converter cell 3 has an equal contribution to the total output grid voltage V g or the total output grid voltage V g (thereby forming a substantially sinusoidal output), the capacitor 5 discharge from each converter cell 3 can be said to contribute to the same (or at least substantially the same) voltage. This voltage difference 3 contributed by each converter cell can be referred to as ΔV.

[0054] To more closely approximate a sinusoidal signal, more converter cells 3 can be used per arm 2, with each converter cell 3 contributing a relatively low ΔV. If each arm 2 contains N converter cells 3 to output each phase of the grid voltage Vg, then ΔV is V g may be configured as a value obtained by dividing by N.

[0055] Each arm 2 of the MMC 1 may be constituted by one or more converter valve assemblies.

[0056] Although an MMC is described herein, it will be understood that the present disclosure may relate to virtually any type of converter having multiple converter cells.

[0057] Figure 3 shows a schematic perspective view of a prismatic converter cell 3. The prismatic converter cell has a length L, a width W, and a height H, these labels being arbitrarily assigned and therefore interchangeable.

[0058] In some alternative embodiments of the present disclosure, converter cell 3 may have different shapes, including, for example, triangular faces or circular faces (i.e., cylindrical), i.e., converter cell 3 may have a three-dimensional (3D) form factor with shortest dimensions of height, width, and length, where the shortest dimension may be equal to the longest or second longest dimension.

[0059] The illustrated converter cell 3 is a rectangular parallelepiped and has a height H that is smaller than its width W, which is smaller than its length L. It can therefore be seen that the shortest dimension of the illustrated prismatic converter cell 3 is its height H.

[0060] 4a and 4b show a prior art converter valve assembly arrangement 10 in which a plurality of converter cells 3 are arranged in layers. According to such prior art arrangements, a plurality of such layers can be stacked on top of each other to form part of a converter arm. Thus, a plurality of such stacks can constitute an arm of the converter.

[0061] The 24 converter cells 3 within a layer are arranged and connected in series in two columns, as indicated by the solid arrows, such that the first and last connected cells 3 are adjacent to each other and have a voltage difference of 24ΔV relative to each other. Therefore, the spacing between the two columns must be configured based on this voltage difference to reduce the risk of electrical arcing or other interference effects between the first and last series-connected cells 3. Similar considerations may apply to the spacing between layers within a stack and / or between stacks.

[0062] However, it will be appreciated that such spacing may be wasted space, since not all cells 3 in a layer have this same voltage difference relative to their spatially nearest neighbors. Indeed, at the opposite ends of the columns (i.e., furthest away as shown in FIG. 4a), opposing cells 3 on either side of the columns are directly connected to each other, and therefore do not require spacing between cells configured to prevent electrical arcing between cells 3 with a voltage difference of 24ΔV.

[0063] Furthermore, such vertical stacking of layers may impose structural limitations on the number of cells 3 that can be included in a converter valve assembly. Alternatively, "vertical stacking" can be thought of as arranging prismatic cells with their longest dimension perpendicular to the plane in which they are arranged. Accordingly, multiple such vertically arranged converter valve assemblies (sometimes referred to as "sub-arms") may be required to form an arm of the converter. During a seismic event (e.g., an earthquake), these sub-arms may displace relative to one another, potentially impairing converter operation.

[0064] Therefore, according to one aspect of the present disclosure, a converter valve assembly is provided that overcomes at least some of these problems in prior art converter valve assemblies such as those shown in Figures 4a and 4b.

[0065] 5a and 5b illustrate one embodiment of a converter valve assembly 20 according to one aspect of the present disclosure.

[0066] According to the illustrated embodiment, converter valve assembly 20 includes three equal groups 6a, 6b, and 6c of prismatic converter cells 3a-ad (sometimes commonly referred to as "converter cells 3"). That is, the thirty illustrated converter cells 3 are evenly distributed with ten converter cells 3 arranged within each group 6a, 6b, and 6c. Group 6a includes converter cells 3a-j, group 6b includes converter cells 3l-3t, and group 6c includes converter cells 3u-3ad.

[0067] Each group 6a, 6b, 6c of converter cells 9 is arranged within a respective plane 7a, 7b, 7c. That is, for example, converter cells 3a-3j are arranged such that plane 7a is defined by their relative arrangement, and plane 7a intersects all of converter cells 3a-3j. Planes 7a, 7b, 7c are spaced apart along axis 8, which in this illustrated embodiment is horizontal axis 8. The spacing along axis 8 is exaggerated in FIG. 5a for clarity of illustration.

[0068] Within each group 6a, 6b, 6c, the converter cells 3 are arranged according to an arrangement common to all groups 6a, 6b, 6c, and the converter cells 3 are connected in series. In group 6a, the converter cells 3 are connected in series from the first converter cell 3 of group 6a, i.e., converter cell 3a, to the last converter cell 3 of group 6a, i.e., converter cell 3j. In group 6b, the converter cells 3 are connected from converter cells 3k to 3t, and in group 6c, the converter cells 3 are connected from converter cells 3u to 3ad.

[0069] The groups 6a, 6b, 6c are connected in series along axis 8 such that the last converter cell 3 of a group 6a, 6b, 6c is connected to the first converter cell 3 of the preceding group 6a, 6b, 6c. In Figure 5a, the last converter cell 3j of group 6a is connected to the first converter cell 3k of group 6b, and the last converter cell 3t of group 6b is connected to the first converter cell 3u of group 6c.

[0070] In the illustrated example, the converter cells 3 are arranged such that they form a spiral shape, as indicated by the superimposed arrows in Figure 5a, i.e., as can be seen in Figure 5a, the converter cells 3 of groups 6a, 6b, 6c are arranged around an axis 8 and connected in sequence according to their radial position around the axis 8, thereby forming an open loop from the first converter cell 3 to the last converter cell 3 of the group 6a, 6b, 6c.

[0071] It will be understood that since each of the groups 6a, 6b, 6c has the same arrangement of converter cells 3 in terms of their spatial arrangement and electrical interconnections, the prismatic converter cells 3 of a group, for example, group 6a, are arranged so that during operation of the converter valve assembly 20, a corresponding voltage difference exists between each converter cell 3 of group 6a and each corresponding converter cell 3 of the adjacent group, for example, group 6b, that is spatially closest to said each converter cell 3.

[0072] In other words, each group 6a, 6b, 6c includes respective converter cells 3 at corresponding locations in the cell arrangement. For example, converter cells 3a, 3k, and 3u are corresponding converter cells 3, converter cells 3e, 3o, and 3y are corresponding converter cells 3, etc. Therefore, according to such an arrangement, the voltage difference between converter cells 3a and 3k may correspond to (i.e., may be the same as or substantially similar to) the voltage difference between converter cells 3e and 3o. The same is true for each pair of corresponding converter cells 3 in each adjacent group 6a, 6b, 6c.

[0073] In particular, if each converter cell 3 contributes a voltage of ΔV, it will be appreciated that there is a voltage difference of 10ΔV between converter cells 3a and 3k because there are 10 converter cells connected in series between them (i.e., converter cells 3a-j, all of the converter cells in group 6a). For the same reason, there is also a voltage difference of 10ΔV between converter cells 3b and 3l, 3c and 3m, 3d and 3n, etc.

[0074] Thus, the spacing along axis 8 between groups 6a and 6b can be determined (reduced, preferably minimized) based on the distance required to prevent electrical arcing due to a voltage difference of 10ΔV, which is the voltage difference between all pairs of corresponding converter cells 3 in groups 6a and 6b, and therefore less space is wasted within converter valve assembly 20, thereby reducing the overall volume of the converter valve assembly.

[0075] While Figure 5a shows each converter cell 3 of each group 6a, 6b, 6c aligned parallel to axis 8, it will be appreciated that in some instances groups 6a, 6b, 6c may be displaced a certain amount perpendicular to axis 8. Moreover, while planes 7a, 7b, 7c are shown as perfectly parallel, it will be appreciated that some deviation therefrom can be tolerated while still achieving the beneficial effects of the particular arrangement of converter cells 3 within converter valve apparatus 20.

[0076] In Figure 5a it can be seen that each group 6a, 6b, 6c of converter cells 3 is attached to a respective substructure 9a, 9b, 9c. Figure 5b shows a top view of group 6a, showing the substructure 9a to which the group 6a of converter cells 3a-j is rigidly attached, according to this illustrative example.

[0077] In particular, according to the illustrated embodiment, the substructure 9a comprises a plurality of rigid bars 11 and interconnections 12 configured to facilitate mechanical connection between the interconnections 12 of another substructure, for example, substructure 9b along axis 8 as shown in FIG. 5a.

[0078] The particular structure of the substructure 9a can take any suitable form, but all of the converter cells 3a-j of the group 6a are preferably rigidly mounted to the same substructure 9a, so that the converter cells 3a-j can be held in position relative to one another so as to maintain spacing between the converter cells 3a-j and thus proper operation of the group of converter cells 3a-j.

[0079] The converter cells 3a-j are connected in series from converter cell 3a to converter cell 3j using electrical connections 13. It will be appreciated that the length of the electrical connections 13 may advantageously be shorter, as the converter cells 3a-j are connected in series according to their radial position around the axis 8 (i.e. in counterclockwise order as shown in Figure 5b).

[0080] Figure 6 shows a converter valve assembly 30 including multiple groups 6a-6g, each having the same number of converter cells 3 and mounted on a respective substructure 9. The arrangement of the cells 3 within a group may be the same or similar to that described in connection with Figures 5a and 5b.

[0081] The groups 6a-g are arranged in parallel planes and are equally spaced apart along the axis. In the illustrated example, the planes of each group are spaced apart by a distance D. Distance D can be determined based on the voltage difference between each converter cell in a group (e.g., group 6a) and each corresponding converter cell in an adjacent group (e.g., group 6b).

[0082] It will be appreciated that depending on the implementation, the number of cells 3 per group 6a-6g can be increased or decreased. Additionally, the number of groups 6a-6g can be varied. In a preferred embodiment, if a converter arm is intended to have N converter cells 3, the number of cells per n group can be N / n, allowing for some remainder. Thus, the converter valve assembly 30 can constitute an entire arm of the converter.

[0083] 7 shows a converter valve assembly 40 having shield structures 14a-14d and a stand assembly 15 for elevating the support structure from the floor (e.g., the floor of a converter hall). The support structure may be formed by rigidly connecting multiple substructures 9.

[0084] The shielding structures 14a-d include a plurality of shielding elements 14a, 14b, 14c, and 14d arranged around each group in a plane defined by the group. Thus, the group of converter cells 3 can be shielded from external interference, and the external environment can likewise be shielded from electromagnetic effects of the converter valve assembly 40. For example, the shielding structures 14a-d can reduce the risk of electrical arcing between the converter valve assembly 40 and its surrounding environment. The shielding structures 14a-d may be made of any suitable material, preferably a conductive metal.

[0085] The stand assembly 15 includes a plurality of posts 16 formed from and / or coated with an insulating material. Figures 8a and 8b show alternative exemplary configurations of the stand assembly, the configuration shown in Figure 8a corresponding to the configuration shown in Figure 7.

[0086] 7 and 8a, each group 6 of converter cells 3 is attached to a respective substructure 9, and each substructure 9 is held by two insulating posts 16. Thus, the spacing between the groups 6 can be established by the relative arrangement of the posts 16.

[0087] In the illustrated example of Figure 8b, multiple substructures 9, each having a respective group of converter cells 3 mounted thereon, may be collectively mounted on a common mounting structure 17 via an intermediate set of posts 16b, e.g., two posts 16a per substructure. The common mounting structure 17 may then be erected on the posts 16a.

[0088] With such an arrangement, isolation between the groups may be provided by insulating posts in the same manner as in the examples shown in Figures 7 and 8a. However, the risk of relative movement of the substructure caused by, for example, an earthquake-related event displacing different pairs of posts 16a by different amounts is reduced. Thus, the relative positions of the groups of converter cells 3 are advantageously preserved with such an arrangement.

[0089] FIG. 9 shows a perspective view of a portion of a converter valve assembly support structure 18 according to an exemplary embodiment of the present disclosure.

[0090] The support structure 18 comprises a plurality of substructures 9a-e similar to those described above, supported by a plurality of posts 16 similar to post 16 (or 16a), as described above in relation to Figures 7, 8a, and 8b.

[0091] The support structure 18 is further configured such that each substructure is rigidly connected to one another by one or more rigid insulating connections 19. Thus, a rigid, continuous structure can be formed, and fewer vertical supports 16 may be required to raise the support structure 18 off the floor.

[0092] Thus, the same advantageous resilience as described in relation to Figure 8b can be achieved, for example in the event of an earthquake-related event. Furthermore, the construction of the support structure 18 can be advantageously simplified.

[0093] 10 shows a perspective view of a converter arm 70 formed entirely as a single converter valve assembly 60 supported on a stand assembly 15. It will be appreciated that the amount of shield structure 14 is significantly less than that required for multiple vertically arranged sub-arms, such as the arrangement described in connection with FIGS. 4a and 4b.

[0094] The stand assembly 15 is shown as having two posts 16 per substructure 9, each substructure 9 having a group of converter cells 3 mounted thereon, although it will be appreciated that other configurations such as those described in relation to Figure 8b or Figure 9 may be employed.

[0095] FIG. 11 illustrates a method 1100 for manufacturing a converter valve assembly as described above, according to one embodiment of the present disclosure.

[0096] As shown, method 1100 may include arranging two or more equal groups of prismatic converter cells to form a converter valve assembly (step 1110), with each group arranged in a respective one of a plurality of parallel planes spaced apart along an axis.

[0097] According to such an arrangement, the converter cells within a group are connected in series, each group being connected in series along an axis, and the arrangement of the prismatic converter cells within a group is configured such that, during operation of the converter valve assembly, a corresponding voltage difference exists between each converter cell within a group and each corresponding converter cell in its spatially nearest adjacent group. Such a method may be implemented manually or using some robotic manipulator means, depending on the implementation.

[0098] While the present disclosure is susceptible to various modifications and alternative forms, specific embodiments have been shown and described by way of example in connection with the drawings in order to clearly explain various advantageous aspects of the disclosure. However, the detailed description herein and the accompanying drawings are not intended to limit the disclosure to the particular forms disclosed. Rather, the intention is to cover all modifications, equivalents, and alternatives falling within the scope of the appended claims.

Claims

1. 1. A converter valve assembly for a power grid system, comprising: two or more equal groups of prismatic converter cells, each group arranged in a respective one of a plurality of parallel planes spaced apart along a horizontal axis; The converter cells in a group are connected in series, the groups are connected in series along the axis; A converter valve assembly, wherein the prismatic converter cells in a group are arranged and configured such that, during operation of the converter valve assembly, a corresponding voltage difference exists between each converter cell in the group and each corresponding converter cell in an adjacent group that is spatially closest to the each converter cell.

2. 2. The converter valve assembly of claim 1, wherein each group is connected in series from a first converter cell to a last converter cell of the group according to a cell arrangement configuration common to all groups, and the last converter cell of the group is connected to a first converter cell of an adjacent group.

3. 3. The converter valve assembly of claim 2, wherein the cell arrangement includes arranging the converter cells in the group around the axis and connecting the converter cells in the group in order according to their radial position around the axis, thereby forming an open loop from the first converter cell to the last converter cell of the group.

4. 4. A converter valve assembly as claimed in claim 2 or claim 3, wherein each converter cell in a group is aligned with a corresponding converter cell in an adjacent group, the corresponding converter cells having the same position in the cell arrangement.

5. 10. A converter valve assembly as described in any preceding claim, wherein the parallel planes are spaced apart along the axis by intervals corresponding to the voltage difference between each converter cell in the group and each corresponding converter cell in the adjacent group.

6. 10. A converter valve assembly as claimed in any preceding claim, wherein each group is rigidly mounted on a respective substructure.

7. 7. The converter valve assembly of claim 6, wherein each substructure is rigidly connected along said axis, thereby forming a support structure for said converter valve assembly.

8. 8. The converter valve assembly of claim 7, wherein the substructure is rigidly connected by an insulating member.

9. a mounting assembly for the support structure; 9. A converter valve assembly according to claim 7 or claim 8, wherein the mounting assembly comprises a suspension assembly for suspending the support structure from a ceiling or a stand assembly for elevating the support structure from a floor.

10. The converter valve assembly of claim 9 , wherein the stand assembly comprises a plurality of posts configured to provide electrical isolation from the floor.

11. Each substructure is attached to a respective post or posts, or The converter valve assembly of claim 9 wherein multiple substructures are mounted via a common mounting structure.

12. 10. A converter valve assembly as claimed in any preceding claim, further comprising group-wise shield structures arranged in said plane.

13. 10. A converter valve assembly according to any preceding claim, wherein the converter valve assembly has a unitary structure that forms an arm of the converter.

14. 10. A converter valve assembly according to any preceding claim, wherein the converter is a modular multi-level converter configured to supply power to a power grid.

15. 10. A method of manufacturing a converter valve assembly according to any preceding claim, comprising the steps of: Two or more equal groups of prismatic converter cells are arranging the groups so that each group is arranged in a respective one of a plurality of parallel planes spaced apart along a horizontal axis; The converter cells in a group are connected in series, Each group is connected in series along the axis, The method, wherein the arrangement of the prismatic converter cells in a group is configured such that, during operation of the converter valve assembly, a corresponding voltage difference exists between each converter cell in the group and each corresponding converter cell in an adjacent group that is spatially closest to the each converter cell.

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