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WO2025061299A1 - Converter leg with low left/right asymmetric currents - Google Patents

Converter leg with low left/right asymmetric currents Download PDF

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Publication number
WO2025061299A1
WO2025061299A1 PCT/EP2023/076277 EP2023076277W WO2025061299A1 WO 2025061299 A1 WO2025061299 A1 WO 2025061299A1 EP 2023076277 W EP2023076277 W EP 2023076277W WO 2025061299 A1 WO2025061299 A1 WO 2025061299A1
Authority
WO
WIPO (PCT)
Prior art keywords
busbar
conductor
converter
semiconductor switch
converter leg
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Pending
Application number
PCT/EP2023/076277
Other languages
French (fr)
Inventor
Joerg Ostrowski
Christoph Winkelmann
Annika BIRTH
Wouter Rens TONNON
Mose PEDUZZI
Jan Frederick EIFERT
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
ABB Schweiz AG
Original Assignee
ABB Schweiz AG
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by ABB Schweiz AG filed Critical ABB Schweiz AG
Priority to PCT/EP2023/076277 priority Critical patent/WO2025061299A1/en
Publication of WO2025061299A1 publication Critical patent/WO2025061299A1/en
Pending legal-status Critical Current
Anticipated expiration legal-status Critical

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Classifications

    • H—ELECTRICITY
    • H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
    • H02M—APPARATUS FOR CONVERSION BETWEEN AC AND AC, BETWEEN AC AND DC, OR BETWEEN DC AND DC, AND FOR USE WITH MAINS OR SIMILAR POWER SUPPLY SYSTEMS; CONVERSION OF DC OR AC INPUT POWER INTO SURGE OUTPUT POWER; CONTROL OR REGULATION THEREOF
    • H02M7/00—Conversion of AC power input into DC power output; Conversion of DC power input into AC power output
    • H02M7/42—Conversion of DC power input into AC power output without possibility of reversal
    • H02M7/44—Conversion of DC power input into AC power output without possibility of reversal by static converters
    • H02M7/48—Conversion of DC power input into AC power output without possibility of reversal by static converters using discharge tubes with control electrode or semiconductor devices with control electrode
    • H02M7/53—Conversion of DC power input into AC power output without possibility of reversal by static converters using discharge tubes with control electrode or semiconductor devices with control electrode using devices of a triode or transistor type requiring continuous application of a control signal
    • H02M7/537—Conversion of DC power input into AC power output without possibility of reversal by static converters using discharge tubes with control electrode or semiconductor devices with control electrode using devices of a triode or transistor type requiring continuous application of a control signal using semiconductor devices only, e.g. single switched pulse inverters
    • H02M7/5387—Conversion of DC power input into AC power output without possibility of reversal by static converters using discharge tubes with control electrode or semiconductor devices with control electrode using devices of a triode or transistor type requiring continuous application of a control signal using semiconductor devices only, e.g. single switched pulse inverters in a bridge configuration
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01L—SEMICONDUCTOR DEVICES NOT COVERED BY CLASS H10
    • H01L23/00—Details of semiconductor or other solid state devices
    • H01L23/48—Arrangements for conducting electric current to or from the solid state body in operation, e.g. leads, terminal arrangements ; Selection of materials therefor
    • H01L23/488—Arrangements for conducting electric current to or from the solid state body in operation, e.g. leads, terminal arrangements ; Selection of materials therefor consisting of soldered or bonded constructions
    • H01L23/492—Bases or plates or solder therefor
    • H—ELECTRICITY
    • H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
    • H02M—APPARATUS FOR CONVERSION BETWEEN AC AND AC, BETWEEN AC AND DC, OR BETWEEN DC AND DC, AND FOR USE WITH MAINS OR SIMILAR POWER SUPPLY SYSTEMS; CONVERSION OF DC OR AC INPUT POWER INTO SURGE OUTPUT POWER; CONTROL OR REGULATION THEREOF
    • H02M1/00—Details of apparatus for conversion
    • H02M1/44—Circuits or arrangements for compensating for electromagnetic interference in converters or inverters
    • H—ELECTRICITY
    • H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
    • H02M—APPARATUS FOR CONVERSION BETWEEN AC AND AC, BETWEEN AC AND DC, OR BETWEEN DC AND DC, AND FOR USE WITH MAINS OR SIMILAR POWER SUPPLY SYSTEMS; CONVERSION OF DC OR AC INPUT POWER INTO SURGE OUTPUT POWER; CONTROL OR REGULATION THEREOF
    • H02M7/00—Conversion of AC power input into DC power output; Conversion of DC power input into AC power output
    • H02M7/003—Constructional details, e.g. physical layout, assembly, wiring or busbar connections
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01L—SEMICONDUCTOR DEVICES NOT COVERED BY CLASS H10
    • H01L23/00—Details of semiconductor or other solid state devices
    • H01L23/34—Arrangements for cooling, heating, ventilating or temperature compensation ; Temperature sensing arrangements
    • H01L23/36—Selection of materials, or shaping, to facilitate cooling or heating, e.g. heatsinks
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01L—SEMICONDUCTOR DEVICES NOT COVERED BY CLASS H10
    • H01L23/00—Details of semiconductor or other solid state devices
    • H01L23/34—Arrangements for cooling, heating, ventilating or temperature compensation ; Temperature sensing arrangements
    • H01L23/46—Arrangements for cooling, heating, ventilating or temperature compensation ; Temperature sensing arrangements involving the transfer of heat by flowing fluids
    • H01L23/473—Arrangements for cooling, heating, ventilating or temperature compensation ; Temperature sensing arrangements involving the transfer of heat by flowing fluids by flowing liquids

Definitions

  • the invention relates to the field of high power converters.
  • the invention relates to a converter leg and to a converter.
  • the current distribution across these devices should be as homogeneous as possible.
  • the root-mean-square-current through each of the semiconductor switches is the same. Otherwise, the semiconductor switches are stressed inhomogeneously, causing a faster degrading of them and lowering a maximal possible load on the converter.
  • the connection of an AC phase input to one of the DC inputs is called a leg.
  • these inputs are provided by busbars, which are in parallel to each other and which carry the semiconductor switches.
  • the busbars may be connected via the semiconductor switches with flexible conducting connectors, sometimes called flexes.
  • the semiconductor switches may be provided on both sides of one of the busbars, which results in flexes forming current loops around a longitudinal direction, in which the busbars extend.
  • This loop may collect magnetic flux and during the commutation of the current from one leg to another, the magnetic flux may change in time and such a change thus induces a circular current in the loop.
  • This loop-current adds up to the initial current in one direction on one side and in the other direction on the other side, and the resulting currents on the left and on the right differ from each other. This problem is sometimes called left/right asymmetry or ladder effect.
  • a first aspect of the invention relates to a converter leg.
  • a converter leg may be a part of an electrical converter, which connects one AC input (such as one of three phase inputs) with a DC input (such as a positive DC input and a negative DC input).
  • one phase input is connected via two converter legs with both DC inputs of the electrical converter.
  • a converter leg is adapted for connecting and disconnecting a current from the AC input to the DC input.
  • the converter leg comprises a first busbar and a second busbar arranged in parallel with each other, a plurality of semiconductor switches and a plurality of conductors interconnecting the first busbar with the second busbar via the semiconductor switches.
  • the first busbar and the second busbar which may be elongated metal bars, extend in a longitudinal direction of the converter leg.
  • the semiconductor switches which may be at least one of diodes, transistors and thyristors, for example IGBTs and IGCTs, are connected in parallel. Passive semiconductor switches, such as diodes, may switch the current themselves. Active semiconductor switches, such as transistors and thyristors, may be switched by gate signals, which may be applied simultaneously or staggered in time to all active semiconductor switches of the converter leg.
  • Each of the semiconductor switches is attached to the first busbar and is connected via a conductor with the second busbar, such that the semiconductor switches are connected in parallel; each semiconductor switch is attached and/or bonded to the first busbar with a first electrode and is attached and/or bonded with a second electrode to a first end of the respective conductor. The other, second end of the conductor is attached and/or bonded to the second busbar.
  • the conductors may be elongated metal strips or metal rods, for example made of sheet metal or woven wires. The conductors may be seen as electrical connectors.
  • each pair comprises a first semiconductor switch and a second semiconductor switch, which are attached to opposite sides of the first busbar and are connected via a first conductor and a second conductor with the second busbar.
  • These busbar sides are on different sides of an extension plane defined by the busbars and in particular their longitudinal directional and a further extension direction of the busbars, in which both busbar extend.
  • Each busbar may be arranged symmetrically with respect to the extension plane.
  • the semiconductor switches of a pair of semiconductor switches may be arranged symmetrically with respect to the extension plane or may be staggered.
  • the pairs of semiconductor switches may be arranged with the same distance along the first busbar.
  • pairs of semiconductor switches and also the pairs of conductors, formed by the corresponding first conductor and second conductor, all may have the same relative arrangement, i.e. may be shift symmetric with respect to each other.
  • the first conductor and the second conductor of a pair form an oriented current loop together with the corresponding pair of semiconductor switches and the busbars.
  • This current loop starts at the first busbar and runs via the first semiconductor switch and the first conductor to the second busbar. It runs in the reverse direction through the second conductor and the second semiconductor switch and through the first busbar to the starting point.
  • the first conductor and the second conductor are bent and/or twisted, such that they at least reduce and at best minimize a circular current through the current loop, which is induced by a magnetic field.
  • the first conductor and the second conductor are twisted, such that they, when considered together as an oriented loop and projected onto a plane, form at least one area with positive orientation and at least one area with negative orientation.
  • This plane may be a plane substantially orthogonal to the longitudinal direction of the busbars.
  • the first conductor and the second conductor have at least one intersection, where they change sides, when running from the first busbar to the second busbar. Areas with positive orientation and negative orientation alternate at the intersection(s). These intersections may be arranged between the first busbar and the second busbar and/or the conductors may change side in the plane between the first busbar and the second busbar.
  • An area with orientation may be defined by a ring (i.e. its border) enclosing the area together with a direction around the ring.
  • An area with positive orientation has a clockwise direction around its border.
  • An area with negative orientation has a counter-clockwise direction around its border.
  • the orientation of an area enclosed by the projected oriented loop is defined by a direction of the oriented loop running around the area.
  • a clockwise direction may be associated with a positive orientation and an anti-clockwise direction with a negative orientation.
  • a magnetic flux change in the same direction and orthogonal to the projected loop induces a positive current in the current loop around an area with positive orientation and a negative current in the current loop around an area with negative orientation.
  • the bent and/or twisted conductors of a pair suppress at least partially induction and an asymmetric current distribution.
  • the sum of the areas with positive orientation and the sum of the areas with negative orientation differ from each other no more than 10 %, for example no more than 5 %. This reduces the induced circular current substantially.
  • the areas with negative orientation also may be considered as negative areas.
  • the first conductor and the second conductor are twisted in three dimensions, i.e. they may have sections extending in three different directions, which do not lie in one plane, i.e. are not coplanar. This opens the possibility to have projected areas of different orientations with respect to at least two planes, which planes may be orthogonal to each other.
  • the first conductor and the second conductor are twisted such that they, when projected onto a first plane, form at least one area with positive orientation and at least one area with negative orientation, which differ from each other no more than 10 %, for example no more than 5 %, and when projected onto a second plane, form at least one area with positive orientation and at least one area with negative orientation, which differ from each other no more than 10 %, for example no more than 5 %.
  • the first plane and the second plane may have a common axis and/or common line which is in the extension plane of the first busbar and the second bus bar and/or which is orthogonal to the longitudinal axis of the first busbar and the second busbar.
  • the first plane and the second plane may be orthogonal to each other.
  • the first conductor and the second conductor are attached with second ends to opposite sides of the second busbar. It may be that the second end of a conductor is attached to the same side of the first and second busbars or to an opposite side of the first and second busbar. In the first case, a part or section of the conductor may protrude through the extension plane of the busbars between the busbars. In the second case, the conductor may run through the extension plane between the busbars and may change side with respect to the extension plane.
  • the first conductor and the second conductor are arranged partially between the first busbar and the second busbar, i.e. a section of the first conductor and a section of the second conductor at least may touch or may protrude through the extension plane.
  • the first semiconductor switch and the second semiconductor switch of a pair of semiconductor switches are arranged offset to each other with respect to the first busbar.
  • the first semiconductor switch and the second semiconductor switch may have a distance with respect to each other along the longitudinal direction of the busbars. It may be that the first semiconductor switches are opposite to semiconductor switches of another pair of semiconductor switches.
  • first ends of the conductors may be offset with respect to each other in the longitudinal direction.
  • connection areas of the first conductor and the second conductor to the second busbar, i.e. the second ends, are offset to each other in the longitudinal direction.
  • first ends and/or second ends make it possible to twist the conductors easier, such that the areas with opposite orientations are formed.
  • sections of the first conductor are oriented in all three spatial directions and sections of the second conductor are oriented in all three spatial directions.
  • the conductor may have a three- dimensional design to generate areas with opposite orientations with respect to more than one projection plane.
  • the first conductor is connected via the first semiconductor switch with a first end to a first side of the first busbar, crosses the extension plane defined by the first busbar and the second busbar and is connected with a second end to a second side of the second busbar, which second side is oriented opposite to the first side of the first busbar.
  • the second conductor is connected via the second semiconductor switch with a first end to a second side of the first busbar, crosses the extension plane defined by the first busbar and the second busbar and is connected with a second end to a first side of the second busbar, which first side is oriented opposite to the second side of the first busbar.
  • the ends of one conductor are on different sides of the extension plane. In such a way, both conductors may cross the extension plane to form the areas with opposite orientations.
  • the first conductor is connected via the first semiconductor switch with a first end to a first side of the first busbar, protrudes beyond and/or through the extension plane defined by the first busbar and the second busbar and is connected with a second end to a first side of the second busbar, which first side faces in the same direction as the first side of the first busbar.
  • the second conductor is connected via the second semiconductor switch with a first end to a second side of the first busbar, protrudes beyond and/or through the extension plane defined by the first busbar and the second busbar and is connected with a second end to a second side of the second busbar, which second side faces in the same direction as the second side of the first busbar.
  • the ends of one conductor are on the same side of the extension plane. This is a further possibility to form the areas with opposite orientations.
  • each conductor is a bent metal strip.
  • Each conductor may be made of sheet metal and/or of woven wires.
  • the conductors may be flexible.
  • the converter leg further comprises a plurality of fuses attached to the second busbar, wherein each semiconductor switch is connected via a conductor with a fuse. These fuses also may be seen as parts of the conductor loop.
  • a cooling body is attached to each semiconductor switch opposite to the first busbar and the respective conductor and in particular its first end is attached to the cooling body.
  • the cooling bodies may be seen as parts of the conductor loop.
  • the cooling bodies may be water cooled and/or may have cooling channels for a cooling fluid.
  • the first busbar is a DC busbar and the second busbar is an AC busbar. It may be that the semiconductor devices are all attached to the DC busbar.
  • a further aspect of the invention relates to an electrical converter.
  • a converter may be a rectifier, for example with diodes, and/or may be an active converter inverter with active semiconductor switches.
  • the converter comprises: at least two converter legs such as described herein. Two of the at least two converter legs, forming a pair of converter legs, are connected in series between a DC+ output and a DC- output of the converter and provide an AC output between them. It may be that the converter is a three-phase or multi-phase converter and has three pairs or a plurality of pairs of such converter legs.
  • Fig. 1 schematically shows a converter according to an embodiment of the invention.
  • Fig. 2a to 2c show three-dimensional views of a converter leg according to an embodiment of the invention.
  • Fig. 3 a to 3c show three-dimensional views of a converter leg according to a further embodiment of the invention.
  • Fig. 4a to 4e show views of a conductor arrangement used in a converter leg according to a further embodiment of the invention.
  • Fig. 5a to 5e show views of a conductor arrangement used in a converter leg according to a further embodiment of the invention.
  • Fig. 6a to 6e show views of a conductor arrangement used in a converter leg according to a further embodiment of the invention.
  • Fig. 7a to 7e show views of a conductor arrangement used in a converter leg according to a further embodiment of the invention.
  • Fig. 8a to 8e show views of a conductor arrangement used in a converter leg according to a further embodiment of the invention.
  • Fig. 1 shows a converter 10, which is composed of six converter legs 12. Each of the converter legs 12 interconnects a phase input 14 with one of the DC+ input or DC- input.
  • the diode symbol in each of the converter legs 12 represents a plurality of parallel connected semiconductor switches 16, which may be diodes, transistors and/or thyristors.
  • the converter 10 may be a rectifier that transforms an AC current into a DC current.
  • the AC side with the phase inputs it may be connected to one or more 3- phase transformers, and on the DC side with DC+ input or DC- input it may be connected to the load.
  • Fig. 2a to 2c show a converter leg 12 in more detail from different directions.
  • Fig. 2a is a view showing the complete leg 12
  • Fig. 2b is a view along a longitudinal direction of the converter leg 12
  • Fig. 2c is a partial view of the converter leg 12.
  • the converter leg 12 comprises a first, DC busbar 18 and a second, AC busbar 20.
  • the busbars 18, 20 are two elongated metal rods with a substantially box-shaped body.
  • the busbars are arranged in parallel in a longitudinal direction L.
  • Each of the busbars 18, 20 is arranged symmetrically to a symmetry plane P (see Fig. 2b).
  • a plurality of semiconductor switches 16a, 16b are attached to both sides of the DC busbar 18.
  • a cooling body 22 is attached on each semiconductor switch 16a, 16b.
  • a plurality of fuses 24a, 24b is attached to both sides of the AC busbar 20.
  • a cooling body 22 is attached on each fuse 24a, 24b.
  • Each cooling body 22 on a semiconductor switch 16a, 16b is connected via a conductor 26a, 26b with a cooling body 22 on a fuse 24a, 24b.
  • each conductor 26a, 26b is connected with a first end 28a to the first busbar 18 and with a second end 28b to the second busbar 20.
  • the conductors 26a, 26b may be bent metal sheets, but also may be bent metal rods or made of woven metal wires.
  • the semiconductor switches 16a, 16b are arranged in pairs, wherein each pair comprises a first semiconductor switch 16a and a second semiconductor switch 16b, which are attached to opposite sides of the first busbar 18 and are connected via a first conductor 26a and a second conductor 26b with the second busbar 20.
  • the first conductor 26a and the second conductor 26b are attached with their ends 28b to opposite sides of the second busbar 20. Furthermore, the ends 28a, 28b of one conductor 26a, 26b are arranged on different sides of the symmetry plane P. The conductors 26a, 26b cross the plane P between the first busbar 18 and the second busbar 20 and change side.
  • a loop 30 (indicated by the arrows in Fig. 2b) in the form of an 8- shape is formed, in which the induced electric fields along the current path compensate themselves.
  • the loop 30 and accordingly the current path is twisted such that induced loop currents are avoided.
  • the left/right-asymmetry may be removed or at least reduced.
  • the areas 32a have the same size as the area 32b.
  • each of the conductors 26a, 26b starts and ends at the same side of the symmetry plane P of the busbars 18, 20. However, both conductors 26a, 26b protrude through the symmetry plane between the busbars 18, 20.
  • the first conductor 26a is connected via the first semiconductor switch 16a with a first end 28a to a first side of the first busbar 18, protrudes beyond a plane P defined by the first busbar 18 and the second busbar 20 and is connected with a second end 28b to a first side of the second busbar 20, which first side faces in the same direction as the first side of the first busbar 18.
  • the second conductor 26b is connected via the second semiconductor switch 16b with a first end 28a to a second side of the first busbar 18, protrudes beyond the plane defined by the first busbar 18 and the second busbar 20 and is connected with a second end 28b to a second side of the second busbar 20, which second side faces in the same direction as the second side of the first busbar 18.
  • Fig. 8a to 8e show a further embodiment of a conductor loop 30 with two conductors 26a, 26b, which is similar to the embodiment of Fig. 6a to 6e, and which has the same properties as these embodiments.
  • the helixes are made of straight sections.
  • the conductors have straight first sections in parallel to the symmetry plane of the busbars 18, 20 and further straight second sections, which interconnect the first sections into a helix.

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  • Engineering & Computer Science (AREA)
  • Power Engineering (AREA)
  • Physics & Mathematics (AREA)
  • Condensed Matter Physics & Semiconductors (AREA)
  • General Physics & Mathematics (AREA)
  • Computer Hardware Design (AREA)
  • Microelectronics & Electronic Packaging (AREA)
  • Electromagnetism (AREA)
  • Rectifiers (AREA)

Abstract

A converter leg (12) comprises: a first busbar (18) and a second busbar (20) arranged in parallel with each other; a plurality of semiconductor switches (16a, 16b); and a plurality of conductors (26a, 26b) interconnecting the first busbar (18) with the second busbar (20) via the semiconductor switches (16a, 16b). Each of the semiconductor switches (16a, 16b) is attached to the first busbar (18) and is connected via a conductor (26a, 26b) with the second busbar (20), such that the semiconductor switches (16a, 16b) are connected in parallel. At least some of the semiconductor switches (16a, 16b) are arranged in pairs, wherein each pair comprises a first semiconductor switch (16a) and a second semiconductor switch (16b), which are attached to opposite sides of the first busbar (18) and are connected via a first conductor (26a) and a second conductor (26b) with the second busbar (20). The first conductor (26a) and the second conductor (26b) are twisted, such that they, when considered together as an oriented loop (30) and projected onto a plane, form at least one area (32a) with positive orientation and at least one area (32b) with negative orientation.

Description

DESCRIPTION
Converter leg with low left/right asymmetric currents
FIELD OF THE INVENTION
The invention relates to the field of high power converters. In particular, the invention relates to a converter leg and to a converter.
BACKGROUND OF THE INVENTION
In converters with paralleled semiconductor switches, such as diodes, thyristors, IGBTs, and IGCTs, the current distribution across these devices should be as homogeneous as possible. Ideally, the root-mean-square-current through each of the semiconductor switches is the same. Otherwise, the semiconductor switches are stressed inhomogeneously, causing a faster degrading of them and lowering a maximal possible load on the converter.
In a converter, the connection of an AC phase input to one of the DC inputs is called a leg. In some converters, these inputs are provided by busbars, which are in parallel to each other and which carry the semiconductor switches. The busbars may be connected via the semiconductor switches with flexible conducting connectors, sometimes called flexes. The semiconductor switches may be provided on both sides of one of the busbars, which results in flexes forming current loops around a longitudinal direction, in which the busbars extend. This loop may collect magnetic flux and during the commutation of the current from one leg to another, the magnetic flux may change in time and such a change thus induces a circular current in the loop. This loop-current adds up to the initial current in one direction on one side and in the other direction on the other side, and the resulting currents on the left and on the right differ from each other. This problem is sometimes called left/right asymmetry or ladder effect.
DESCRIPTION OF THE INVENTION
It is an objective of the invention to provide a converter leg with low left/right asymmetry. Further objectives of the invention are to provide a converter with small semiconductor degrading and to provide a converter with high utilization of the semiconductor switches.
These objectives are achieved by the subject-matter of the independent claims. Further exemplary embodiments are evident from the dependent claims and the following description.
A first aspect of the invention relates to a converter leg. A converter leg may be a part of an electrical converter, which connects one AC input (such as one of three phase inputs) with a DC input (such as a positive DC input and a negative DC input). Usually, one phase input is connected via two converter legs with both DC inputs of the electrical converter. A converter leg is adapted for connecting and disconnecting a current from the AC input to the DC input.
According to an embodiment of the invention, the converter leg comprises a first busbar and a second busbar arranged in parallel with each other, a plurality of semiconductor switches and a plurality of conductors interconnecting the first busbar with the second busbar via the semiconductor switches. The first busbar and the second busbar, which may be elongated metal bars, extend in a longitudinal direction of the converter leg. The semiconductor switches, which may be at least one of diodes, transistors and thyristors, for example IGBTs and IGCTs, are connected in parallel. Passive semiconductor switches, such as diodes, may switch the current themselves. Active semiconductor switches, such as transistors and thyristors, may be switched by gate signals, which may be applied simultaneously or staggered in time to all active semiconductor switches of the converter leg.
Each of the semiconductor switches is attached to the first busbar and is connected via a conductor with the second busbar, such that the semiconductor switches are connected in parallel; each semiconductor switch is attached and/or bonded to the first busbar with a first electrode and is attached and/or bonded with a second electrode to a first end of the respective conductor. The other, second end of the conductor is attached and/or bonded to the second busbar. The conductors may be elongated metal strips or metal rods, for example made of sheet metal or woven wires. The conductors may be seen as electrical connectors.
At least some of the semiconductor switches are arranged in pairs, wherein each pair comprises a first semiconductor switch and a second semiconductor switch, which are attached to opposite sides of the first busbar and are connected via a first conductor and a second conductor with the second busbar. There may be semiconductor switches on both sides of the first busbar. These busbar sides are on different sides of an extension plane defined by the busbars and in particular their longitudinal directional and a further extension direction of the busbars, in which both busbar extend. Each busbar may be arranged symmetrically with respect to the extension plane.
The semiconductor switches of a pair of semiconductor switches may be arranged symmetrically with respect to the extension plane or may be staggered. The pairs of semiconductor switches may be arranged with the same distance along the first busbar.
The pairs of semiconductor switches and also the pairs of conductors, formed by the corresponding first conductor and second conductor, all may have the same relative arrangement, i.e. may be shift symmetric with respect to each other.
The first conductor and the second conductor of a pair form an oriented current loop together with the corresponding pair of semiconductor switches and the busbars. This current loop starts at the first busbar and runs via the first semiconductor switch and the first conductor to the second busbar. It runs in the reverse direction through the second conductor and the second semiconductor switch and through the first busbar to the starting point.
The first conductor and the second conductor are bent and/or twisted, such that they at least reduce and at best minimize a circular current through the current loop, which is induced by a magnetic field.
According to an embodiment of the invention, the first conductor and the second conductor are twisted, such that they, when considered together as an oriented loop and projected onto a plane, form at least one area with positive orientation and at least one area with negative orientation. This plane may be a plane substantially orthogonal to the longitudinal direction of the busbars. In the projection, the first conductor and the second conductor have at least one intersection, where they change sides, when running from the first busbar to the second busbar. Areas with positive orientation and negative orientation alternate at the intersection(s). These intersections may be arranged between the first busbar and the second busbar and/or the conductors may change side in the plane between the first busbar and the second busbar.
An area with orientation may be defined by a ring (i.e. its border) enclosing the area together with a direction around the ring. An area with positive orientation has a clockwise direction around its border. An area with negative orientation has a counter-clockwise direction around its border.
The orientation of an area enclosed by the projected oriented loop is defined by a direction of the oriented loop running around the area. A clockwise direction may be associated with a positive orientation and an anti-clockwise direction with a negative orientation.
A magnetic flux change in the same direction and orthogonal to the projected loop induces a positive current in the current loop around an area with positive orientation and a negative current in the current loop around an area with negative orientation. In such a way, the bent and/or twisted conductors of a pair suppress at least partially induction and an asymmetric current distribution.
Such a converter leg provides the possibility to minimize the left-right asymmetry of the root-mean-square-currents through the semiconductor switches. This is achieved by twisting the conductors, i.e., the current path between the DC side and AC side of the converter leg geometrically such that induced loop currents are at least partially eliminated and/or minimized.
Due to the more homogeneous current through the semiconductor switches, it is possible to reduce the number of semiconductor switches for the same current rating, because excess currents do not occur anymore. This reduces the cost of the converter leg and the converter. Moreover, each semiconductor switch ages in the same way because they all carry the same current. This may extend the lifetime of the converter leg and the converter.
According to an embodiment of the invention, the sum of the areas with positive orientation and the sum of the areas with negative orientation differ from each other no more than 10 %, for example no more than 5 %. This reduces the induced circular current substantially. The areas with negative orientation also may be considered as negative areas.
According to an embodiment of the invention, the first conductor and the second conductor are twisted in three dimensions, i.e. they may have sections extending in three different directions, which do not lie in one plane, i.e. are not coplanar. This opens the possibility to have projected areas of different orientations with respect to at least two planes, which planes may be orthogonal to each other.
According to an embodiment of the invention, the first conductor and the second conductor are twisted such that they, when projected onto a first plane, form at least one area with positive orientation and at least one area with negative orientation, which differ from each other no more than 10 %, for example no more than 5 %, and when projected onto a second plane, form at least one area with positive orientation and at least one area with negative orientation, which differ from each other no more than 10 %, for example no more than 5 %. The first plane and the second plane may have a common axis and/or common line which is in the extension plane of the first busbar and the second bus bar and/or which is orthogonal to the longitudinal axis of the first busbar and the second busbar. The first plane and the second plane may be orthogonal to each other.
According to an embodiment of the invention, the first conductor and the second conductor are attached with second ends to opposite sides of the second busbar. It may be that the second end of a conductor is attached to the same side of the first and second busbars or to an opposite side of the first and second busbar. In the first case, a part or section of the conductor may protrude through the extension plane of the busbars between the busbars. In the second case, the conductor may run through the extension plane between the busbars and may change side with respect to the extension plane.
According to an embodiment of the invention, the first conductor and the second conductor are arranged partially between the first busbar and the second busbar, i.e. a section of the first conductor and a section of the second conductor at least may touch or may protrude through the extension plane.
According to an embodiment of the invention, the first semiconductor switch and the second semiconductor switch of a pair of semiconductor switches are arranged offset to each other with respect to the first busbar. The first semiconductor switch and the second semiconductor switch may have a distance with respect to each other along the longitudinal direction of the busbars. It may be that the first semiconductor switches are opposite to semiconductor switches of another pair of semiconductor switches.
In such a way, also the first ends of the conductors may be offset with respect to each other in the longitudinal direction.
According to an embodiment of the invention, connection areas of the first conductor and the second conductor to the second busbar, i.e. the second ends, are offset to each other in the longitudinal direction.
Offset first ends and/or second ends make it possible to twist the conductors easier, such that the areas with opposite orientations are formed. According to an embodiment of the invention, sections of the first conductor are oriented in all three spatial directions and sections of the second conductor are oriented in all three spatial directions. As already mentioned, the conductor may have a three- dimensional design to generate areas with opposite orientations with respect to more than one projection plane.
According to an embodiment of the invention, the first conductor is connected via the first semiconductor switch with a first end to a first side of the first busbar, crosses the extension plane defined by the first busbar and the second busbar and is connected with a second end to a second side of the second busbar, which second side is oriented opposite to the first side of the first busbar. Analogously, the second conductor is connected via the second semiconductor switch with a first end to a second side of the first busbar, crosses the extension plane defined by the first busbar and the second busbar and is connected with a second end to a first side of the second busbar, which first side is oriented opposite to the second side of the first busbar. In this embodiment, the ends of one conductor are on different sides of the extension plane. In such a way, both conductors may cross the extension plane to form the areas with opposite orientations.
According to an embodiment of the invention, the first conductor is connected via the first semiconductor switch with a first end to a first side of the first busbar, protrudes beyond and/or through the extension plane defined by the first busbar and the second busbar and is connected with a second end to a first side of the second busbar, which first side faces in the same direction as the first side of the first busbar. Analogously, the second conductor is connected via the second semiconductor switch with a first end to a second side of the first busbar, protrudes beyond and/or through the extension plane defined by the first busbar and the second busbar and is connected with a second end to a second side of the second busbar, which second side faces in the same direction as the second side of the first busbar. In this embodiment, the ends of one conductor are on the same side of the extension plane. This is a further possibility to form the areas with opposite orientations.
According to an embodiment of the invention, each conductor is a bent metal strip. Each conductor may be made of sheet metal and/or of woven wires. The conductors may be flexible.
According to an embodiment of the invention, the converter leg further comprises a plurality of fuses attached to the second busbar, wherein each semiconductor switch is connected via a conductor with a fuse. These fuses also may be seen as parts of the conductor loop.
According to an embodiment of the invention, a cooling body is attached to each semiconductor switch opposite to the first busbar and the respective conductor and in particular its first end is attached to the cooling body. There also may be a cooling body between the second end of the conductor and the fuse. Also the cooling bodies may be seen as parts of the conductor loop. The cooling bodies may be water cooled and/or may have cooling channels for a cooling fluid.
According to an embodiment of the invention, the first busbar is a DC busbar and the second busbar is an AC busbar. It may be that the semiconductor devices are all attached to the DC busbar.
A further aspect of the invention relates to an electrical converter. Such a converter may be a rectifier, for example with diodes, and/or may be an active converter inverter with active semiconductor switches.
According to an embodiment of the invention, the converter comprises: at least two converter legs such as described herein. Two of the at least two converter legs, forming a pair of converter legs, are connected in series between a DC+ output and a DC- output of the converter and provide an AC output between them. It may be that the converter is a three-phase or multi-phase converter and has three pairs or a plurality of pairs of such converter legs.
These and other aspects of the invention will be apparent from and elucidated with reference to the embodiments described hereinafter.
BRIEF DESCRIPTION OF THE DRAWINGS
The subject-matter of the invention will be explained in more detail in the following text with reference to exemplary embodiments which are illustrated in the attached drawings.
Fig. 1 schematically shows a converter according to an embodiment of the invention.
Fig. 2a to 2c show three-dimensional views of a converter leg according to an embodiment of the invention.
Fig. 3 a to 3c show three-dimensional views of a converter leg according to a further embodiment of the invention. Fig. 4a to 4e show views of a conductor arrangement used in a converter leg according to a further embodiment of the invention.
Fig. 5a to 5e show views of a conductor arrangement used in a converter leg according to a further embodiment of the invention.
Fig. 6a to 6e show views of a conductor arrangement used in a converter leg according to a further embodiment of the invention.
Fig. 7a to 7e show views of a conductor arrangement used in a converter leg according to a further embodiment of the invention.
Fig. 8a to 8e show views of a conductor arrangement used in a converter leg according to a further embodiment of the invention.
The reference symbols used in the drawings, and their meanings, are listed in summary form in the list of reference symbols. In principle, identical parts are provided with the same reference symbols in the figures.
DETAILED DESCRIPTION OF EXEMPLARY EMBODIMENTS
Fig. 1 shows a converter 10, which is composed of six converter legs 12. Each of the converter legs 12 interconnects a phase input 14 with one of the DC+ input or DC- input. The diode symbol in each of the converter legs 12 represents a plurality of parallel connected semiconductor switches 16, which may be diodes, transistors and/or thyristors.
For example, the converter 10 may be a rectifier that transforms an AC current into a DC current. On the AC side with the phase inputs it may be connected to one or more 3- phase transformers, and on the DC side with DC+ input or DC- input it may be connected to the load.
Fig. 2a to 2c show a converter leg 12 in more detail from different directions. Fig. 2a is a view showing the complete leg 12, Fig. 2b is a view along a longitudinal direction of the converter leg 12 and Fig. 2c is a partial view of the converter leg 12. The converter leg 12 comprises a first, DC busbar 18 and a second, AC busbar 20. The busbars 18, 20 are two elongated metal rods with a substantially box-shaped body. The busbars are arranged in parallel in a longitudinal direction L. Each of the busbars 18, 20 is arranged symmetrically to a symmetry plane P (see Fig. 2b).
A plurality of semiconductor switches 16a, 16b are attached to both sides of the DC busbar 18. On each semiconductor switch 16a, 16b, a cooling body 22 is attached. A plurality of fuses 24a, 24b is attached to both sides of the AC busbar 20. Also on each fuse 24a, 24b, a cooling body 22 is attached. Each cooling body 22 on a semiconductor switch 16a, 16b is connected via a conductor 26a, 26b with a cooling body 22 on a fuse 24a, 24b.
As shown in Fig. 2b, each conductor 26a, 26b is connected with a first end 28a to the first busbar 18 and with a second end 28b to the second busbar 20. The conductors 26a, 26b may be bent metal sheets, but also may be bent metal rods or made of woven metal wires.
The semiconductor switches 16a, 16b are arranged in pairs, wherein each pair comprises a first semiconductor switch 16a and a second semiconductor switch 16b, which are attached to opposite sides of the first busbar 18 and are connected via a first conductor 26a and a second conductor 26b with the second busbar 20.
As best seen in Fig. 2b, the first conductor 26a and the second conductor 26b are attached with their ends 28b to opposite sides of the second busbar 20. Furthermore, the ends 28a, 28b of one conductor 26a, 26b are arranged on different sides of the symmetry plane P. The conductors 26a, 26b cross the plane P between the first busbar 18 and the second busbar 20 and change side.
Due to the crossing, a loop 30 (indicated by the arrows in Fig. 2b) in the form of an 8- shape is formed, in which the induced electric fields along the current path compensate themselves. The loop 30 and accordingly the current path is twisted such that induced loop currents are avoided. The left/right-asymmetry may be removed or at least reduced.
If a time-varying magnetic field goes through the area that is formed by the loop 30, a circular loop current will be induced in the loop 30. If the loop 30 would be a single ring (in the projection of Fig. 2b), the circular current would amplify an incoming initial current on one side of the converter leg 12 and would weaken it on the other side of the converter leg 12. The resulting current is no longer symmetric on both sides of the converter leg 12. This is the main reason for the left/right asymmetry.
In the case of Fig. 2b, the loop 30 providing the current path is formed by the conductors 26a, 26b in such a way, that the magnetic flux through the area, that is formed by it, does not induce a current. In Fig 2b, this is achieved by twisting the conductors 26a, 26b into a twisted-8-shape. The two loop currents that are induced in the two rings that form the 8-shape compensate themselves at least partially.
In Fig. 2a to 2c, the first semiconductor switch 16a and the second semiconductor switch 16b of a pair of semiconductor switches are arranged offset to each other with respect to the first busbar 18. Also, the fuses 24a, 24b corresponding to a pair are arranged offset to each other with respect to the second busbar 20. In particular, connection areas of the first conductor 26a and the second conductor 26b to the first busbar 18 and second busbar 20 are offset to each other in the longitudinal direction. In such a way, the conductors 26a, 26b can be guided along each other between the first busbar 18 and the second busbar 20, without touching each other.
In general, the twisted-8-shape is just one possible realization of a twisted current path, along which the induced loop current is eliminated or reduced by geometrical construction and orientation of the current path relative to the magnetic field B. The induced voltage U is the integral of the electric field E
Figure imgf000012_0001
along the current path y that circumvents the area Ay that is formed by the twisted conductors 26a, 26b. Minimizing the induced voltage and thereby the induced current may be realized by one or more twists with different orientations. It is also possible to eliminate or reduce loop currents due to magnetic flux changes even in multiple directions, as will be explained with respect to the following figures.
In Fig. 2a to 2c, the conductors 26a, 26b are solely bent in two dimensions (spatial directions).
Fig. 3a to 3c show an embodiment, in which the conductors 26a, 26b are bent in three dimensions. Due to reasons of clarity, solely the semiconductor switch 16a, 16b of a pair together with the corresponding fuses 24a, 24b, conductors 26a, 26b and cooling bodies 22 are provided with reference numerals.
As best seen in Fig. 3 c, the first semiconductor switch 16a and the first fuse 24a are at the same longitudinal height with respect to the busbars 18, 20. Analogously, the second semiconductor switch 16b and the second fuse 24b are at the same longitudinal height with respect to the busbars 18, 20, however, offset with respect to the first semiconductor switch 16a and the first fuse 24a. The first conductor 26a connects the first semiconductor switch 16a with the second fuse 24b, which is arranged offset to the first semiconductor switch 16a. The second conductor 26b connects the second semiconductor switch 16b with the first fuse 24a, which is arranged offset to the second semiconductor switch 16b. As in Fig. 2a to 2c, the first conductor 26a and the second conductor 26b are arranged partially between the first busbar 18 and the second busbar 20. The sections of the conductors 26a, 26b between the first busbar 18 and the second busbar 20 run inclined with respect to the longitudinal direction L and the plane P. In particular, the first conductor 26a and the second conductor 26b are oriented in all three spatial directions and are bent as a three-dimensional curve.
With the embodiment of Fig. 3 a to 3 c, not only loop currents around the longitudinal direction L, but also loop currents around a direction orthogonal to the plane P may be reduced or eliminated.
Fig. 4a to 4e show the conductors 26a, 26b of one semiconductor pair of Fig. 2a to 2c in a more abstract way. The conductors 26a, 26b and the busbars 18, 20 are represented by lines. The other parts of the converter leg are not shown. Solely the conductor loop 30 and the corresponding current path are shown.
Fig. 4a shows a view along the x-axis. Fig. 4b shows a view along the y-axis. Fig. 4e shows a view along the z-axis, which corresponds to the longitudinal direction L. Fig. 4c and 4d are views, which are inclined with 30° and 60° with respect to the z-axis.
As shown in Fig. 4a, the two conductors 26a, 26b cross the plane defined by the busbars 18, 20 between the busbars 18, 20 and change side. Fig. 4e shows the projection of the conductor loop 30 onto the plane defined by the x- and y-axis. It can be seen that the conductors 26a, 26b are twisted, such that they, when considered together as an oriented loop 30 and projected onto the plane defined by the x- and y-axis, form an area 32a with positive orientation and an area 32b with negative orientation. The orientations are indicated by the round arrows.
The areas 32a, 32b have the same size and therefore the current induced by a substantially homogeneous magnetic field orthogonal to the plane defined by the x- and y- axis is substantially 0. It has to be understood that the conductors 26a, 26b can be deformed with respect to Fig. 4e as long as the areas 32a, 32b substantially have the same size. For example, the conductors 26a, 26b need not be formed of half-circles, but can have kinks or sharp bends, such as in Fig. 2a to 2c.
Fig. 5a to 5e show the conductors 26a, 26b of one semiconductor pair of Fig. 3a to 3c in a more abstract way. Fig. 5a to 5e are similar to Fig. 4a to 4e.
It can be seen that the conductors 26a, 26b are additionally bent with respect to the z- axis and/or longitudinal direction. The ends of the conductors 26a, 26b are offset with respect to the longitudinal direction. As can be seen in Fig. 5b, this results in a further plane (here the plane defined by the x- and z-axis), in which the projected current loop 30 has two areas 32c, 32d of different orientation but substantially the same size. The difference of the size of the areas may be smaller than 10 %.
Fig. 6a to 6e show a further embodiment of a conductor loop 30 with two conductors 26a, 26b. Each of the conductors 26a, 26b is shaped as a helix. The first conductor 26a and the second conductor 26b are twisted, such that the corresponding oriented loop 30 projected onto any plane, which comprises the x-axis, forms areas 32a with positive orientation and areas 32b with negative orientation, wherein the sum of the areas 32a with positive orientation and the sum of the areas 32b with negative orientation differ from each other no more than 10 % and in particular are equal.
As for example depicted in Fig. 6e, the areas 32a have the same size as the area 32b.
Fig. 7a to 7e show a further embodiment of a conductor loop 30 with two conductors 26a, 26b. Each of the conductors 26a, 26b is shaped as two mirror-symmetric helixes, which are connected in the middle. In a first section, each of the conductors 26a, 26b winds in a first direction and in a second section, winds in the opposite direction. Each of the conductors 26a, 26b is mirror symmetric with respect to a middle plane between the busbars 18, 20.
As in Fig. 6a to 6e, the conductors 26a, 26b are twisted, such that the corresponding oriented loop 30 projected onto any plane, which comprises the x-axis, forms areas 32a with positive orientation and areas 32b with negative orientation, wherein the sum of the areas 32a with positive orientation and the sum of the areas 32b with negative orientation differ from each other no more than 10 % and in particular are equal.
Additionally to this property, due to the change in the turning sense of the conductors 26a, 26b, there is not even a voltage induced by a changing magnetic flux in x-direction.
In Fig. 7a to 7e, each of the conductors 26a, 26b starts and ends at the same side of the symmetry plane P of the busbars 18, 20. However, both conductors 26a, 26b protrude through the symmetry plane between the busbars 18, 20.
The first conductor 26a is connected via the first semiconductor switch 16a with a first end 28a to a first side of the first busbar 18, protrudes beyond a plane P defined by the first busbar 18 and the second busbar 20 and is connected with a second end 28b to a first side of the second busbar 20, which first side faces in the same direction as the first side of the first busbar 18. The second conductor 26b is connected via the second semiconductor switch 16b with a first end 28a to a second side of the first busbar 18, protrudes beyond the plane defined by the first busbar 18 and the second busbar 20 and is connected with a second end 28b to a second side of the second busbar 20, which second side faces in the same direction as the second side of the first busbar 18.
Fig. 8a to 8e show a further embodiment of a conductor loop 30 with two conductors 26a, 26b, which is similar to the embodiment of Fig. 6a to 6e, and which has the same properties as these embodiments. In Fig. 8a to 8e, however, the helixes are made of straight sections. The conductors have straight first sections in parallel to the symmetry plane of the busbars 18, 20 and further straight second sections, which interconnect the first sections into a helix.
While the invention has been illustrated and described in detail in the drawings and foregoing description, such illustration and description are to be considered illustrative or exemplary and not restrictive; the invention is not limited to the disclosed embodiments. Other variations to the disclosed embodiments can be understood and effected by those skilled in the art and practising the claimed invention, from a study of the drawings, the disclosure, and the appended claims. In the claims, the word “comprising” does not exclude other elements or steps, and the indefinite article “a” or “an” does not exclude a plurality. A single processor or controller or other unit may fulfil the functions of several items recited in the claims. The mere fact that certain measures are recited in mutually different dependent claims does not indicate that a combination of these measures cannot be used to advantage. Any reference signs in the claims should not be construed as limiting the scope.
LIST OF REFERENCE SYMBOLS
10 converter
12 converter leg
14 phase input
DC+ DC+ input
DC- DC- input
16 semiconductor switch
16a first semiconductor switch
16b second semiconductor switch
18 first, DC busbar
20 second, AC busbar
P symmetry plane
L longitudinal direction
22 cooling body
24a first fuse
24b second fuse
26a first conductor
26b second conductor
28a first end
28b second end
30 current / conductor loop
32a area of first orientation
32b area of second orientation
32c area of first orientation
32d area of second orientation

Claims

1. A converter leg (12), comprising: a first busbar (18) and a second busbar (20) arranged in parallel with each other; a plurality of semiconductor switches (16a, 16b); a plurality of conductors (26a, 26b) interconnecting the first busbar (18) with the second busbar (20) via the semiconductor switches (16a, 16b); wherein each of the semiconductor switches (16a, 16b) is attached to the first busbar (18) and is connected via a conductor (26a, 26b) with the second busbar (20), such that the semiconductor switches (16a, 16b) are connected in parallel; wherein at least some of the semiconductor switches (16a, 16b) are arranged in pairs, wherein each pair comprises a first semiconductor switch (16a) and a second semiconductor switch (16b), which are attached to opposite sides of the first busbar (18) and are connected via a first conductor (26a) and a second conductor (26b) with the second busbar (20); wherein the first conductor (26a) and the second conductor (26b) are twisted, such that they, when considered together as an oriented loop (30) and projected onto a plane, form at least one area (32a) with positive orientation and at least one area (32b) with negative orientation.
2. The converter leg (12) of claim 1, wherein the sum of the areas (32a) with positive orientation and the sum of the areas (32b) with negative orientation differ from each other no more than 10 %.
3. The converter leg (12) of claim 1 or 2, wherein the first conductor (26a) and the second conductor (26b) are twisted in three dimensions, such that they, when projected onto a first plane, form at least one area (32a) with positive orientation and at least one area (32b) with negative orientation, which differ from each other no more than 10 %, and when projected onto a second plane, form at least one area (32c) with positive orientation and at least one area with negative orientation (32d), which differ from each other no more than 10 %.
4. The converter leg (12) of one of the previous claims, wherein the first conductor (26a) and the second conductor (26b) are attached with ends (28b) to opposite sides of the second busbar (20).
5. The converter leg (12) of one of the previous claims, wherein the first conductor (26a) and the second conductor (26b) are arranged partially between the first busbar (18) and the second busbar (20).
6. The converter leg (12) of one of the previous claims, wherein the first semiconductor switch (16a) and the second semiconductor switch (16b) of a pair of semiconductor switches are arranged offset to each other with respect to the first busbar (18); and/or wherein connection areas of the first conductor (26a) and the second conductor (26b) to the second busbar (20) are offset to each other.
7. The converter leg (12) of one of the previous claims, wherein sections of the first conductor (26a) are oriented in all three spatial directions and wherein sections of the second conductor (26b) are oriented in all three spatial directions.
8. The converter leg (12) of one of the previous claims, wherein the first conductor (26a) is connected via the first semiconductor switch (16a) with a first end (28a) to a first side of the first busbar (18), crosses a plane (P) defined by the first busbar (18) and the second busbar (20) and is connected with a second end (28b) to a second side of the second busbar (20), which second side is oriented opposite to the first side of the first busbar (18); wherein the second conductor (26b) is connected via the second semiconductor switch (16b) with a first end (28a) to a second side of the first busbar (18), crosses the plane (P) defined by the first busbar (18) and the second busbar (20) and is connected with a second end (28b) to a first side of the second busbar (20), which first side is oriented opposite to the second side of the first busbar (18).
9. The converter leg (12) of one of claims 1 to 7, wherein the first conductor (26a) is connected via the first semiconductor switch (16a) with a first end (28a) to a first side of the first busbar (18), protrudes beyond a plane (P) defined by the first busbar (18) and the second busbar (20) and is connected with a second end (28b) to a first side of the second busbar (20), which first side faces in the same direction as the first side of the first busbar (18); wherein the second conductor (26b) is connected via the second semiconductor switch (16b) with a first end (28a) to a second side of the first busbar (18), protrudes beyond the plane defined by the first busbar (18) and the second busbar (20) and is connected with a second end (28b) to a second side of the second busbar (20), which second side faces in the same direction as the second side of the first busbar (18).
10. The converter leg (12) of one of the previous claims, wherein each conductor (26a, 26b) is a bent metal strip; and/or wherein each conductor (26a, 26b) is made of sheet metal.
11. The converter leg (12) of one of the previous claims, further comprising: a plurality of fuses (24a, 24b) attached to the second busbar (20); wherein each semiconductor switch (16a, 16b) is connected via a conductor (26a, 26b) with a fuse (24a, 24b).
12. The converter leg (12) of one of the previous claims, wherein a cooling body (22) is attached to each semiconductor switch (16a, 16b) opposite to the first busbar (18) and the respective conductor (26a, 26b) is attached to the cooling body (22).
13. The converter leg (12) of one of the previous claims, wherein the semiconductor switches (16a, 16b) are at least one of diodes, transistors and thyristors.
14. The converter leg (12) of one of the previous claims, wherein the first busbar (18) is a DC busbar and the second busbar (20) is an AC busbar.
15. A converter ( 10), compri sing : at least two converter legs (12) according to one of the previous claims; wherein two of the at least two converter legs (12) are connected in series between a DC+ output and a DC- output of the converter (10) and provide an AC output (14) between them.
PCT/EP2023/076277 2023-09-22 2023-09-22 Converter leg with low left/right asymmetric currents Pending WO2025061299A1 (en)

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