TECHNICAL FIELD

The present invention generally relates to the field of connectors for converter stations, and more particularly to a connector for connecting valve arrangements of a high-voltage direct current converter.

BACKGROUND

A high-voltage direct current (HVDC) converter station is a type of station adapted to convert high voltage direct current (DC) to alternating current (AC) or the reverse. An HVDC converter station may comprise a plurality of elements such as the converter itself (or a plurality of converters connected in series or in parallel), an alternating current switch gear, transformers, capacitors, filters, a direct current switch gear and other auxiliary elements. Electronic converters may be categorized as line-commuted converters using for example thyristors as switches, or voltage source converters using transistors, such as insulated gate bipolar transistors (IGBTs), as switches. A plurality of solid-state semiconductor devices, such as thyristors or IGBTs, may be connected to each other, for instance in series, to form a building block or a valve arrangement of an HVDC converter. The valve arrangement may also be referred to as a valve tower, indicating a substantially vertical orientation.

A challenge in the construction and design of an HVDC converter station is the electrical connection between the different parts of the HVDC converter station, and in particular the electrical connection between the valve arrangements. Generally, the valve arrangements are physically separated from each other for electrical insulation purposes and may further be supported by insulators mounted on the floor or suspended from the ceiling of a valve hall. In some applications flexible joints may be employed to allow the valve towers to sway with an earthquake. A relative displacement between the valve towers may also be caused by transportation or movement of the converter, for example to offshore locations. The movement or displacement of the valve towers presents a challenge to the electrical connections of the valve towers, which risk inflicting damage to the equipment or result in electrical disconnection.

Thus, there is a need for improved connectors for HVDC converter stations in general, and for the interconnection of valve arrangements in particular.

SUMMARY

It would be advantageous to achieve a technique overcoming or at least alleviating at least some of the above-mentioned drawbacks. In particular, it would be desirable to enable an improved connector for interconnecting a first and a second valve arrangement of an HVDC converter.

To better address one or more of these concerns, a connector having the features defined in the independent claims is provided. Preferable embodiments are defined in the dependent claims.

Hence, according to a first aspect, a connector is provided, which is configured to electrically interconnect a first and a second valve arrangement of an HVDC converter. The connector comprises a first housing part adapted to be coupled to a terminal of the first valve arrangement and a second housing part adapted to be coupled to a terminal of the second valve arrangement. The first housing part may be adapted to slide along the second housing part to form an extendable and retractable housing. The connector further comprises a conductor arrangement, which may be at least partly accommodated in the housing and comprise a flexible conductor and a guiding means for guiding the flexible conductor. A first portion of the flexible conductor may be coupled to the first housing part and a second portion of the flexible conductor may be coupled to the second housing part for electrically interconnecting the first and second housing parts. Further, the conductor arrangement may be foldable to allow a reciprocating movement of the first housing part relative to the second housing part as the valve arrangements move relative to each other.

According to a second aspect, an HVDC converter is provided, comprising a first and a second valve arrangement and a connecter according to the first aspect, wherein the connector may be coupled between a respective terminal of the first and second valve arrangements.

Several advantages are associated with the present disclosure. The extendable and retractable housing formed by the first and second housing parts makes it possible for the connector to follow a relative motion between the valve arrangements, such that the connector may extend its length as the valve arrangements move away from each other and reduce its length in response to the valve arrangements move towards each other. Further, by arranging the first housing part to slide along the second housing part, for example in a telescopic manner, the housing may be relatively rigid and allow motion primarily along its length direction.

The flexible conductor may be coupled between the housing parts to provide an electrical current path between the two housing parts. The flexibility of the conductor allows for the conductor to move with the housing parts. Thus, the current may pass in a relatively safe and reliable way between the housing parts regardless of any resistance or poor conduction that may be caused by the moving/sliding interface between the two housing parts.

Further, the conductor may be supported by the guiding means, which may provide mechanical support and stability during repeated extension and retraction of the connector housing. The conductor arrangement, formed by the flexible conductor and the guiding means, may be adapted to fold over itself so that one portion of the conductor arrangement at least partly covers another portion of the conductor arrangement. The folding movement allows for the conductor arrangement to absorb the differences in length caused by the relative movement of the housing parts.

By connector is generally meant an electrical connector, and preferably a connector for HVDC applications. The connector may also be referred to as a busbar. It will be appreciated that the actual material composition and cross-sectional size of the connector, and in particular the housing parts forming the housing, may be selected based on the maximum amount of current that should be safely carried. The connector may comprise end terminals or portions adapted to provide both an electrical and a mechanical coupling to a terminal of a respective valve arrangement, such that the connector can be reliably secured and electrically connected between the valve arrangements.

The housing parts may be fitted with each other such that one of the housing parts can slide into (or onto) the other housing part along a length direction of the housing. An increase of the total length of the connector may be understood as an extension, whereas a shortening of the total length may be understood as a retraction of the housing. The length direction of the housing may at least partly correspond to the current path between provided by the connector when interconnecting the valve arrangements. The movement of the housing parts may also be referred to as a reciprocating movement, in which the predominant motion of the housing parts may be along the length direction of the housing.

It should be noted that the housing may not necessarily be limited to two housing parts. Other examples of the present disclosure may include more than two housing parts as well.

In case the housing parts are designed to slide into one another, the housing may be referred to as a telescopic housing.

The valve arrangement may also be referred to as a valve tower and may generally comprise a plurality of preferably stacked switches or valves that are connected to each other. In some examples, the switches may be stacked above each other in a substantially vertical direction. The valve arrangement may for example be arranged in a valve hall of a substation, or form part of an underwater substation.

By the term “folding” is, for the purpose of the present disclosure, understood the ability of something flexible and generally relatively flat to bend over itself to that one part of is arranged above, but not necessarily directly on, another part.

According to an embodiment, the flexible conductor may be formed of, or comprise, a plurality of crossing electrical wires. In some examples the plurality of electrical wires may be braided or woven. The braided or woven configuration of the conductor may enhance its ability to conduct electrical currents and allow for an improved mechanical strength and endurance in response a repeated movement of the conductor.

Alternatively, the flexible conductor is formed of one or several flexible metallic sheets, such as for example aluminium sheets, configured to follow the motion of the guiding means as the housing extends and retracts.

In an example, the flexible conductor is formed of copper or an alloy comprising copper.

According to an embodiment, the guiding means comprises a plurality of linked elements arranged to extend at least partly along the flexible conductor. Thus, the linked elements may be arranged sequentially along a length extension of the flexible conductor to form a supporting chain. Preferably, the elements may be connected to each other by revolute joints forming a planar linkage, in which the movement of the linked elements may be constrained to substantially parallel planes. The resulting chain may hence be be arcuated in a first plane while counteracting bending movements in other planes. Further, the linked configuration allows for the guiding means to be folded in a way that may reduce the risk of plastic deformation and fatigue of the material of the guiding means.

According to an embodiment, the flexible conductor may be at least partly accommodated within the guiding means. In an example the links of the chains may form a channel or passage in which the flexible conductor may be arranged. Alternatively, the flexible conductor may be secured to one side of the guiding means by protrusions, ridges or tongues, which may form an attachment means that may be integrally formed with the links. By arranging the flexible conductor within at least some of the links of the chain, and/or attaching the flexible conductor to at least some of the links, the flexible conductor may be allowed to be guided by, and closely follow, the motion of the chain. Advantageously, the present embodiment may provide a well- controlled and precise folding movement of the flexible conductor, preventing sharp folds and edges that may impair the current conduction capability and increase the mechanical endurance of the conductor.

According to an embodiment, the guiding means may be formed of, or at least comprise, an electrically insulating material allowing a major portion of the current passing between the housing parts to be conducted through the flexible connector.

According to an embodiment, the first and second housing parts may be adapted to be electrically conducting and form part of an electrical conduction path between the first and second valve arrangements. Thus, the electrical current may be transported through the walls forming the housing.

The first and second housing parts may for example be formed of aluminium, or by an alloy comprising aluminium.

According to an embodiment, the first and second housing parts may be tubular. The cross section may for example be circular or polygonal. In case of a polygonal cross section, the edges of the cross section may be rounded, with a relatively large radius, to reduce the electrical field generated at the edges as the current passes though the housing. The circular crosssection, or rounded edges of the cross-section, allows for the connector to handle the relatively high currents associated with HVDC converters.

According to an embodiment, the housing comprises at least one opening for allowing a heat-transfer fluid to flow therethrough. The fluid may for example be a cooling liquid or a gas, such as for example ambient air. One or several openings may be arranged at positions in the housing which facilitate the generation of a passive cooling flow during use of the connector. The position of the openings may for example be selected based on the orientation of the connector between the valve arrangement, such that a first opening for example may be arranged at a higher vertical level than a second opening, thereby facilitating a thermally induced flow of air rising through the housing.

In an example, the connector may be coupled to a top terminal of a first valve tower and a bottom terminal of a second valve tower such that the connector is arranged in an inclining manner relative to the direction of gravity and thereby facilitates a thermally induced air flow.

Other objects, features and advantages of the enclosed embodiments will be apparent from the following detailed description, from the attached dependent claims as well as from the drawings. Those skilled in the art realise that different features of the present invention, even if recited in different claims, can be combined in embodiments other than those described in the following.

BRIEF DESCRIPTION OF DRAWINGS

Exemplifying embodiments will now be described in more detail with reference to the following appended drawings, on which:

Figure 1 is a perspective view of a portion of a connector according to an embodiment;

Figure 2 shows cross sections of a portion of a connector according to an embodiment, in which the connector is arranged in three different positions;

Figure 3 is a perspective view of a guiding means according to an embodiment;

Figure 4 is a perspective view of a flexible conductor according to an embodiment;

Figure 5 is a perspective view of a conductor according to an embodiment; and

Figure 6 schematically illustrates an HVDC converter comprising a first and a second valve tower and an interconnecting connector according to an embodiment.

As illustrated in the figures, the sizes of the elements and regions may be exaggerated for illustrative purposes and, thus, are provided to illustrate the general structures of the embodiments. Like reference numerals refer to like elements throughout.

DETAILED DESCRIPTION

Exemplifying embodiments will now be described more fully hereinafter with reference to the accompanying drawings, in which currently preferred embodiments are shown. The invention may, however, be embodied in many different forms and should not be construed as limited to the embodiments set forth herein; rather, these embodiments are provided for thoroughness and completeness, and fully convey the scope of the invention to the skilled person. With reference to figure 1 , a connector 100 according to an embodiment will now be described. The connector 100, which may be configured to electrically interconnect a first and a second valve arrangement (not shown in the present figure) of a HVDC converter, may comprise an housing that is extendable and retractable (with reference to its length direction) so as to follow a relative motion between the valve arrangements. The relative motion may for example be caused by the valve arrangements swaying due to an earthquake.

The housing may be formed of a first housing part 112 and a second housing part 114 adapted to slide along each other, wherein the first housing part 112 for example may be adapted to slide into the second housing part 114 so as to allow the total length of the housing to be varied accordingly. In the present example, the first and second housing parts 112, 114 are tubular and fitted with each other in a manner that allows for a telescopic movement of the housing parts 112, 114. The tubular cross section may, as indicated in the figure, be substantially polygonal with rounded edges for reducing electrical field concentrations when used in high-voltage applications. The housing may hence be formed of an electrically conducting material, such as for example aluminum or an aluminum-based alloy.

Each housing part 112, 114 may further comprise a respective terminal or coupling means 111 , 113 (shown in figure 5) for coupling the connector 100 to a respective terminal of the first and second valve arrangements. The coupling may preferably be provided both for mechanical and electrical purposes so as to ensure a good electrical interconnection of the valve arrangements as well as a secure mechanical attachment that can withstand relative movement between the valve arrangements.

The connector 100 further comprises a conductor arrangement 120 that may be at least partly accommodated in the housing 100. The conductor arrangement 120 comprises a flexible conductor 130 and a guiding means 140 for guiding the flexible conductor 130. A first portion 132 of the flexible conductor 130 may be coupled to the first housing part 112 and a second portion 134 of the flexible conductor 130 may be coupled to the second housing part 114 so as to electrically interconnect the first and second housing parts 112, 114. Thus, the conductor arrangement 120 may provide an electrical conduction path. The conductor arrangement 120 may be foldable and arranged in such a manner that it allows a reciprocating, or telescopic, movement of the first housing part 112 relative to the second housing part 114 as the valve arrangements move relative to each other, while the conductor arrangement 120 maintains an electrical interconnection between the first and second housing parts 112, 114. The first portion 132 and the second portion 134 of the flexible conductor 130 may hence be coupled to the respective first and second housing part 112, 114 in a way that allows for the flexible conductor 130 to be both mechanically and electrically connected to the housing.

Figure 2 is a schematic illustration of the connector of figure 1 when arranged in three different positions - a first, retracted position illustrated by the upper figure, a second, neutral or intermediate position illustrated by the middle figure, and a third, extended position illustrated by the lower figure. Please note that the central portion of the housing, covering the conductor arrangement 120, has been omitted for illustrative purposes.

The conductor arrangement 120 may be foldable to allow the housing parts 112, 114 to move relative each other in a length direction of the connector. As shown in the illustrated example, the degree of overlap between portions of the conductor arrangement 120 may be varied so as to compensate for, or absorb, differences in length of the connector as the housing parts 112, 114 are moving. It is appreciated that the conductor arrangement 120 may bend over itself so that one part may be arranged above another part.

This configuration of the conductor arrangement 120 has the advantage that an electrical conduction path may be maintained during, and between, all three positions indicated in the present figure. The electrical current may hence pass through a first one of the housing parts 112, 114, be coupled into the flexible conductor 130 of the conductor arrangement 120 via an end portion or attachment point 132, 134 of the flexible conductor 130, pass through the flexible conductor 130, and be coupled to the other one of the housing parts 112, 114 via another end portion or attachment point 132, 134 of the flexible conductor 130.

Figure 3 shows a guiding means 140 of a conductor arrangement 120 according to an embodiment, which may be similarly configured as the embodiments described above with reference to figures 1 and 2. The conductor arrangement 120 may, according to the present example, comprise a plurality of linked elements 142 configured to extending at least partly along a length extension, or current path direction, of the flexible conductor. The plurality of linked elements 142 may be sequentially connected to each other to form a chain 140. The linked elements 142 further be connected to each other by means of revolute joints constraining the linked elements 142 to move in substantially parallel planes. The resulting chain 140 may thus be arcuated in a first plane while being less moveable or flexible in other planes. The guiding means 140 may hence be referred to as a planar linkage, providing mechanical support to the flexible conductor and limiting or reducing movements of the conductor to essentially a single plane.

The guiding means 140 may further comprise one or several attachment means, such as protrusions, ridges or tongues, for securing the flexible conductor to the guiding means 140. In the present figure the attachment means are represented by bars, ribs or elongated plates 144 extending from one side to another side of the guiding means, as seen in a direction orthogonal to the length direction of the flexible conductor. Thus, some or each of the linked elements 142 of the guiding means 140 may be provided with the attachment means 144 for supporting the entire length of the flexible conductor. The guiding means 140 may in some examples comprise two rows of ribs 144, wherein a first row is arranged at an upper side of the guiding means 140 and a second row is arranged at a lower side of the guiding means 140, defining a space between the rows in which the flexible conductor may be accommodated. An example of such a rib or cage structure of the attachment means 144 is shown in figure 3, wherein the flexible conductor can be received between opposing rows of attachment means 144. Alternatively, the guiding means 140 may be considered to be formed of two rows of linked elements 142, extending in parallel and along the length direction of the guiding means 140, wherein the two rows are connected to each other by means of the attachment means 144. In such an embodiment the attachment means 144 thus serves double purposes, i.e. to interconnect the rows of linked elements 142 and provide a mechanical support for the flexible conductor.

The guiding means may for example be formed of an electrically insulating material, such as a plastic material including polyamides and glass fiber.

Figure 4 is an example of a flexible conductor 130 of a conductor arrangement according to an embodiment, which may be similarly configured as the embodiments discussed above in connection with the previous figures. The flexible conductor 130 may also be referred to as a busbar and may be formed of one or several individual conductors 135. In the present example, the flexible conductor 130 is formed of a plurality of braided wires, which for example may be formed of copper.

The flexible conductor 130 may have a shape and configuration that allows it to be fitted with the attachment means 144 of the guiding means 140 as discussed above. The present embodiment may for example be configured to be accommodated within the guiding means 140, between the opposing rows of ribs 144 extending across the length direction of the guiding means 140.

The flexible conductor 130 may further comprise terminal portions, or coupling means 132, 134 at its end portions. The coupling means 132, 143 may be attached to the remaining parts of the flexible conductor 130 to ensure a reliable electrical and mechanical connection and may further be configured to be secured to the first and second housing part, respectively. The coupling means 132, 134 may for example be fixated to the first and second housing parts by means of a screw connection.

Figure 5 is a perspective view of a connector according to an embodiment, which may be similarly configured as the connectors shown in figures 1 to 4. The connector 100 may comprise a housing 110 formed of a first housing part 112 having an end portion 111 which can be coupled to a terminal of a first valve arrangement, and a second housing part 114 having an end portion 113 which can be coupled to a terminal of a second valve arrangement. Further, the connector 100 may comprise one or several openings 115 arranged in the first and/or second housing parts 112, 114 for allowing a heat-transfer fluid to flow therethrough. The heat-transfer fluid may for example be ambient air, which may enter the interior of the housing 110 through a first one of the openings 115 and flow through the interior of the housing 110 towards a second one of the openings 115, through which the air may flow out to the surroundings. The flow, which also may be referred to as a cooling flow, may be passive or active. In case of being passive, the flow may be thermally induced between openings 115 arranged at different vertical levels of the connector. In case of a being active, the flow may be assisted by a fan or the like.

Figure 6 shows an HVDC converter 10, or at least a part of such converter, comprising a first valve arrangement or tower 20 and a second valve arrangement or tower 30. Further, a connector 100 as outlined in the above-mentioned examples may be arranged to provide an electrical interconnection between the valve arrangements 20, 30. The first valve arrangement 20 may comprise a top terminal 22, to which the connector 100 may be coupled via a first coupling mechanism 111 at an end portion of the connector 100 as discussed in connection with figure 5. Similarly, the second valve arrangement 30 may comprise a bottom terminal 32, to which the connector 100 may be coupled via a second coupling mechanism 113 at another end portion 113 of the connector 100. The coupling mechanisms 111 , 113 may be configured to allow a rotational movement between the connector 100 and the valve arrangements 20, 30 to make it easier for the connector 100 to follow a relative motion between the valve arrangements 20, 30. The connector 100 may compensate for a relative displacement or movement of the valve arrangements 20, 30, should that for example happen during an earthquake, by telescopically adjusting its length and rotate around the coupling points to the terminals of the valve arrangements 20, 30. The valve arrangements 20, 30 may in some examples be suspended from the ceiling of a valve hall of the converter station or be mounted on flexible joints on the floor so as to allow the valve arrangements 20, 30 to sway in response to earthquakes and other external movements. In further examples the valve arrangements 20, 30 and their associated support structures may be designed to avoid, or at least reduce, swaying in response to for example quakes. Thus, the valve arrangements 20, 30 may be designed to be relatively rigid or stiff compared to solutions in which the valve arrangements 20, 30 are suspended or mounted on flexible joints. However, since it for practical reasons tend to be difficult to completely eliminate any movements of the valve towers 20, 30, the connector according to the above- mentioned embodiments may be employed to provide a flexible connection also for the rigid, or stiff, designs as set out above.

It should be noted that the connector 100 according to the present example may be arranged to incline relative to the direction of gravity, which may facilitate a cooling flow through openings arranged in the housing as discussed above.

While the present disclosure has been described with reference to exemplary embodiments, it will be appreciated that the present invention is not limited to what has been described above. For example, it will be appreciated that the dimension of the parts may be varied as needed. Further, the connector is not limited to only two housing parts. On the contrary, the housing may be formed of three or more housing parts, of which some or all may be slidable relative to each other to allow the housing to vary its length in response to a varying distance or separation between the valve arrangements. Accordingly, it is intended that the present embodiments may be limited only by the scope of the claims appended hereto.