WO2013000512A1

WO2013000512A1 - A rack for a modular voltage source converter and an insulation device

Info

Publication number: WO2013000512A1
Application number: PCT/EP2011/060916
Authority: WO
Inventors: Mauro Monge
Original assignee: ABB Technology AG
Current assignee: ABB Technology AG
Priority date: 2011-06-29
Filing date: 2011-06-29
Publication date: 2013-01-03
Anticipated expiration: 2013-12-29
Also published as: CN204290748U; DE212011100212U1

Abstract

The invention relates to a rack 13 for a modular voltage source converter 11 comprising one or more converter modules 12₁..., 12n. The rack 13 comprises a housing 15 for accommodating the one or more converter modules 12₁..., 12_n, and an insulation device 10 comprising: a first electrically conducting layer 16, comprising a first connection means 19 for connection to an enclosure 14 housing the rack 13; a second electrically conducting layer 17, comprising a second connection means 20 for connection to one converter module 12₁ of the one or more converter modules 12₁,..., 12_n; and an insulating layer 18 separating the first electrically conducting layer 16 and the second electrically conducting layer 17. The invention also relates to an insulation device 10.

Description

A rack for a modular voltage source converter and an insulation device

Field of the invention

The invention relates generally to the field of voltage source converters, and in particular to converter racks, insulation and protection thereof.

Background of the invention

Voltage Source Converters (VSC) , also called STATCOM, are today a valuable solution for enhancing the power quality of an electrical power grid and for assuring the compliance with Grid Codes in case of integration of stochastic generation (i.e. wind power, solar power) . The need to cut system costs is driving the technology towards standard solutions and, with reference to figure 1,

multilevel converters 1 are often built by a series/parallel connection of standard converter modules 2 _{l r} ... , 2_n, (also denoted converter cells, converter links or valves) . These standard

converter modules 2 _{l r} ... , 2_n, are stacked in mechanical racks 3. The multilevel converter 1 is typically connected to medium/high voltage and the converter phases need to be sufficiently insulated from a housing 4, for example may be a container, within which the

multilevel converter 1 is placed. Such insulation is accomplished by means of insulators and adequate air distances to walls, floor and ceiling of the housing, as indicated in the figure by two-headed arrows .

Enough air distances between the racks and the housing must thus be assured for the electrical insulation, which limits the compactness of the solution and heavily affects the system costs when the voltage source converter 1 is directly connected to distribution and transmission voltage levels. The air insulation distances limit the size and the number of racks which may be installed in standard containers, leading to an increased number of needed containers for hosting the voltage source converter.

US 3,805,140 discloses a solution wherein an insulating barrier is fastened onto the inner wall of a metal container housing a AC-DC convertor. To arrange such insulating barrier on the container walls may be cumbersome and the manufacture of such insulating barrier for a whole container is both costly and difficult.

Besides the above solutions of dimensioning the housing so as to provide enough air distances, and the lining of the housing with insulating material, solutions using insulation oil or vacuum insulation are known.

The above mentioned known solutions suffer from one or more

disadvantages such as high material, production and installation costs, requirements for large footprint, constituting a hazard for the environment. Further, high maintenance costs are high,

particularly for oil or gas insulated structures, and mechanical costs for assuring sealing of all parts are very high.

Summary of the invention

In view of the above, it is an object of the invention to provide cost-efficient and compact insulation means for converter module assemblies .

The object is according to a first aspect of the invention achieved by a rack for a modular voltage source converter comprising one or more converter modules. The rack comprises a housing for

accommodating the one or more converter modules; and an insulation device comprising: a first electrically conducting layer, comprising a first connection means for connection to an enclosure housing the rack, a second electrically conducting layer, comprising a second connection means for connection to one converter module of the one or more converter modules, and an insulating layer separating the first electrically conducting layer and the second electrically conducting layer.

The invention provides a compact insulation solution for modular converter systems, enabling the reduction of size and number of enclosures for hosting the converter modules. The invention thereby also enables reduced system costs. The reduced size requirement of the enclosures can instead be exploited by introducing additional converter modules for applications wherein such need may arise. Further still, the solution of the invention may be standardized and is suitable for mass production, again allowing compact system at low cost. The low footprint required by the inventive rack and insulation device renders them particularly suitable for e.g. offshore wind power platforms .

The object is according to a second aspect of the invention achieved by an insulation device for a rack accommodating a modular voltage source converter comprising one or more converter modules. The insulation device comprises a first electrically conducting layer, comprising a first connection means for connection to an enclosure housing the rack. The insulation device further comprises a second electrically conducting layer, comprising a second connection means for connection to one converter module of the one or more converter modules. The insulation device further comprises an insulating layer separating the first electrically conducting layer and the second electrically conducting layer. Features corresponding to the above are achieved also for this aspect of the invention.

Further features and advantages of the invention will become clear upon reading the following description and the accompanying

drawings .

Brief description of the drawings

Figure 1 illustrates a prior art converter rack.

Figure 2 illustrates a converter rack and insulation device

according to the invention.

Figure 3 illustrates a detail of figure 2.

Figure 4 illustrates the invention for a delta connected voltage source converter.

Figure 5 illustrates an advantage obtained by means of the

invention .

Detailed description of embodiments In the following description, for purposes of explanation and not limitation, specific details are set forth such as particular architectures, interfaces, techniques, etc. in order to provide a thorough understanding of the invention. However, it will be apparent to those skilled in the art that the invention may be practiced in other embodiments that depart from these specific details. In other instances, detailed descriptions of well-known devices, circuits, and methods are omitted so as not to obscure the description of the invention with unnecessary detail. Same reference numerals refer to like elements throughout the description.

With reference to figure 2, a mechanical rack 13, also denoted converter rack, in accordance with an embodiment of the invention is shown. The rack 13 is intended for a modular voltage source

converter 11, and could comprise a standardized mechanical converter rack with the adaptations that will be described. The modular voltage source converter 11 comprises one or more converter modules 12i,..., 12_n (hence modular) .

As an example, the voltage source converter 11 could be adapted for use at a connection voltage of 33 kV, the voltage source converter 11 could then comprise e.g. 80 converter modules. Each phase of the voltage source converter 11 may thus require several racks 13 for housing the converter modules that are needed for the particular voltage level (see also figure 4) .

The rack 13 comprises a housing 15 for accommodating the one or more converter modules 12i,..., 12_n. The housing 15 may for example be made of metal or plastics. The housing 15 comprises means for receiving the converter modules, for example fittings or mountings by means of which a converter module that is inserted into the rack housing 15 is fastened thereto. The converter modules are then interconnected to each other by cabling, thus together providing the desired voltage level.

The rack 13 further comprises an insulation device 10 comprising a first electrically conducting layer 16 and a second electrically conducting layer 17. The electrically conducting layers 16, 17 are separated by an electrically insulating layer 18. The insulation device 10 is illustrated in more detail in figure 3.

The first electrically conducting layer 16 comprises a first connection means 19, suitable for connection to e.g. an enclosure 14, which houses the rack 13. Typically, the rack 13 (or a number of racks) is (are) housed within a standard sized container, and the enclosure 14 may comprise such a container. As another example, the enclosure 14 may be a concrete housing with internal metal

structures (i.e. to limit electro-magnetic emission) . The first electrically conducting layer 16 should comprise connection means 19 for being connectable to such enclosure, which enclosure is

typically grounded. Alternatively, the first electrically conducting layer 16 could be connectable to some other ground potential. The first connection means 19 may comprise welded connections, i.e. the first conducting layer 16 is connected to the enclosure 14 by welding. Another example comprises removable electrical terminals applied by mechanical pressure and by means of which the first connection means 19 connects to the enclosure 14. Yet further examples comprise bolts and/or screws. The second electrically conducting layer 17 comprises a second connection means 20 for connection to one converter module 12i of the one or more converter modules 12i,..., 12_n. The second connection means 20 is typically connected to an active part having the highest electrical potential (relative to e.g. ground potential) in the direction of the insulation distance that is to be reduced, i.e. in the illustrated case vertically towards the ceiling of the enclosure 14, and vertically towards the floor of the enclosure 14. The second connection means 20 could be identical to the first connection means, for example comprising an electrical terminal, welded connection, bolts or screws.

The insulating layer 18 is arranged between the first and second electrically conducting layers 16, 17 and thus separates the first electrically conducting layer 16 from the second electrically conducting layer 17. The insulating layer 18 may comprise a solid insulating material, preferably having a high dielectric constant, such as plastic or rubber.

In an embodiment, the insulation layer 18 is dimensioned so as to provide the insulation device 10 with a capacitance for protection of the modular voltage source converter 11 against fast transient inrush currents. That is, the insulation layer 18 may be dimensioned so as to provide the insulation device 10 with a capacitance suitable for its intended use. The insulation device 10 then functions as a distributed extra shunt capacitance along the voltage source converter 11. The material of the insulation layer 18 may additionally or alternatively be chosen so as to provide the insulation device 10 with the desired capacitance for protection of the modular voltage source converter 11 against such fast transient inrush currents. When designing and producing the insulation device 10, it should be ensured that the first electrically conducting layer 16, the second conducting layer 17 and the insulating layer 18 are produced and interconnected such as to eliminate any air them between. Thereby partial discharges are avoided. Further, each of the first

electrically conducting layer 16, the second conducting layer 17 and the insulating layer 18 should be ensured to be void of air.

Another design aspect related to such partial discharges is the shape of the first electrically conducting layer 16, the second electrically conducting layer 17 and the insulating layer 18. In particular, they should be shaped so as to evenly distribute an electric field, for example giving the layers smoothed (rounded) edges .

The insulation device 10 may be arranged at a top part 21 of the housing 15 and/or at a bottom part 22 of the housing 15. The first electrically conducting layers 16 of each insulation device 10 are connected to the enclosure 14, thus typically being connected to ground potential, as the enclosure is typically grounded. The second electrically conducting layers 17 are connected to the terminals of the neighbor converter module. In the illustrated case, this would be to the uppermost converter module of a stack of converter modules and the lowest placed converter module of the stack of modules, respectively. The second electrically conducting layers 17 thus assume the same potential as these converter modules.

The insulation device 10 may be fastened to the rack 13 in various ways. A first example comprises using electrically insulating fastening means, for example co-operating engagement members such as male and female coupling means. That is, the rack housing 15 may be provided with female coupling means, into which male coupling means, provided on the insulation device 10, are inserted. If the rack housing 15 is made of an electrically conducting

material, such as metal, and the housing 15 is connected to the highest converter module (converter module 12i in the illustrated case) , then the housing 15 would be at the same potential as the second electrically conducting layer 17. The insulation device 10, and in particular the second electrically conducting layer 17 thereof, could then be fastened to the rack 13 simply by metal screws or the like.

The invention also encompasses the insulation device 10 for a rack 13 as described. That is, a rack 13 accommodating a modular voltage source converter 11 comprising one or more converter modules 12_lr...,

12_n. The insulation device 10 is designed bearing in mind the aspects which have already been described. The insulation device 10

comprises a first electrically conducting layer 16, a second

electrically conducting layer 17 and an insulating layer 18

separating them.

In an embodiment, the first electrically conducting layer 16, the second conducting layer 17 and the insulating layer 18 are

interconnected such as to eliminate any air them between.

Preferably, it is also ensured that each layer 16, 17, 18 is void of air.

In an embodiment, the first electrically conducting layer 16, the second electrically conducting layer 17 and the insulating layer 18 are shaped so as to comprise smoothed corner, whereby an electrical field is evenly distributed. In an embodiment, the insulating layer 18 comprises a solid insulating material having a high dielectric constant, such as plastic or rubber.

In an embodiment, the insulation layer 18 is dimensioned so as to provide the insulation device 10 with a capacitance for protection of the modular voltage source converter 11 against fast transient inrush currents.

In an embodiment, a mater

as to provide the insulat

protection of the modular

transient inrush currents

In an embodiment, the fir

connection means 20 compr

electrical terminals.

In an embodiment, the fir

ground potential, and the

an active part of the modular voltage source converter 11 having highest electrical potential.

Although some particular embodiment of the insulation device 10 are described above, the insulation device 10 may be provided with any combination of features that have already been described when describing the rack 13.

Figure 4 illustrates a delta connected voltage source converter 11, thus having three phase legs LI, L2, L3. As mentioned earlier, the rack 13 (or a number of racks) is (are) housed within a standard sized container, the enclosure 14 comprising such a container. This is convenient for a number of reasons; much of the cabling can for example be performed at one and the same place for all converters. The containers are then shipped to its intended place of operation, which shipping is facilitated by the containers having standard sizes .

It is noted that the delta connection of the voltage source converter is provided purely as an example, and other types of connections may also benefit from the teachings of the invention, such as for example star (why) connected voltage source converter or single phase converter.

Figure 5 illustrates the briefly mentioned aspect of providing a distributed extra shunt capacitance along the voltage source converter 11. This is a natural protection against fast transient inrush currents, which may derive e.g. from lightning phenomena (as illustrated by the leftmost arrow) . Such lightning phenomena are potentially damaging for the converter modules. As mentioned, the capacitance value of the insulation device 10 can be chosen by varying the insulting material (having different dielectric

constants) and/or by adapting the insulating thickness. The

insulation device (s) 10 thus provides distributed surge capacitances that protect the converter modules .

By means of the invention, the electric insulation provided by the insulation device 10 can be assured with a limited distance, leading to a much more compact converter system as compared to prior art. The insulation device 10 can be integrated with the mechanical rack 13 holding the converter modules. The production costs are reduced, even minimized, thanks to a solution that can make use of

standardized racks.

Claims

1. A rack (13) for a modular voltage source converter (11)

comprising one or more converter modules (12i,..., 12_n) , the rack (13) comprising :

- a housing (15) for accommodating the one or more converter modules

- an insulation device (10) comprising:

- a first electrically conducting layer (16), comprising a first connection means (19) for connection to an enclosure (14) housing the rack (13) ,

- a second electrically conducting layer (17), comprising a second connection means (20) for connection to one converter module (12i) of the one or more converter modules (12i,..., 12_n) , and

- an insulating layer (18) separating the first electrically conducting layer (16) and the second electrically conducting layer (17) .

2. The rack (13) as claimed in claim 1, wherein the first

electrically conducting layer (16), the second conducting layer (17) and the insulating layer (18) are interconnected such as to

eliminate any air them between.

3. The rack (13) as claimed in claim 1 or 2, wherein each of the first electrically conducting layer (16), the second conducting layer (17) and the insulating layer (18) are void of air.

4. The rack (13) as claimed in any of the preceding claims, wherein the first electrically conducting layer (16), the second

electrically conducting layer (17) and the insulating layer (18) are shaped so as to evenly distribute an electric field.

5. The rack (13) as claimed in claim 4, wherein the second

electrically conducting layer (17) and the insulating layer (18) comprise smoothed edges.

6. The rack (13) as claimed in any of the preceding claims, wherein the insulating layer (18) comprises a solid insulating material having a high dielectric constant, such as plastic or rubber.

7. The rack (13) as claimed in any of the preceding claims, wherein the insulation layer (18) is dimensioned so as to provide the insulation device (10) with a capacitance for protection of the modular voltage source converter (11) against fast transient inrush currents .

8. The rack (13) as claimed in any of the preceding claims, wherein a material of the insulation layer (18) is chosen so as to provide the insulation device (10) with a capacitance for protection of the modular voltage source converter (11) against fast transient inrush currents .

9. The rack (13) as claimed in any of the preceding claims, wherein the first connection means (19) and the second connection means (20) comprise welded connections or removable terminals.

10. The rack (13) as claimed in any of the preceding claims, wherein the first connection means (19) is connected to ground potential, and the second connection means (20) is connected to active part of the modular voltage source converter (11) with highest electrical potential .

11. The rack (13) as claimed in any of the preceding claims, wherein the insulation device (10) is arranged at a top part (21) of the housing (15) and/or at a bottom part (22) of the housing (15) .

12. The rack (13) as claimed in any of the preceding claims, wherein the insulation device (10) is fastened to the rack (13) by means of electrically insulating fastening means.

13. An insulation device (10) for a rack (13) accommodating a modular voltage source converter (11) comprising one or more converter modules (12i,..., 12_n) , the insulation device (10) comprising :

- an insulating layer (18) separating the first electrically

conducting layer (16) and the second electrically conducting layer (17) .

14. The insulation device (10) as claimed in claim 13, wherein the first electrically conducting layer (16), the second conducting layer (17) and the insulating layer (18) are interconnected such as to eliminate any air them between.

15. The insulation device (10) as claimed in claim 13 or 12, wherein each of the first electrically conducting layer (16), the second conducting layer (17) and the insulating layer (18) are void of air.

16. The insulation device (10) as claimed in any of claims 13-15, wherein the first electrically conducting layer (16), the second electrically conducting layer (17) and the insulating layer (18) are shaped so as to comprise smoothed corner, whereby an electrical field is evenly distributed.

17. The insulation device (10) as claimed in any of claims 13-16, wherein the insulating layer (18) comprises a solid insulating material having a high dielectric constant, such as plastic or rubber .

18. The insulation device (10) as claimed in any of claims 13-17, wherein the insulation layer (18) is dimensioned so as to provide the insulation device (10) with a capacitance for protection of the modular voltage source converter (11) against fast transient inrush currents .

19. The insulation device (10) as claimed in any of claims 13-18, wherein a material of the insulation layer (18) is chosen so as to provide the insulation device (10) with a capacitance for protection of the modular voltage source converter (11) against fast transient inrush currents.

20. The insulation device (10) as claimed in any of claims 13-19, wherein the first connection means (19) and the second connection means (20) comprise welded connections or removable terminals.

21. The insulation device (10) as claimed in any of claims 13-20, wherein the first connection means (19) is connected to ground potential, and the second connection means (17) is connected to an active part of the modular voltage source converter (11) having highest electrical potential.