EP1338083A1 - Appareil permettant de convertir une tension alternative en tension directe - Google Patents

Appareil permettant de convertir une tension alternative en tension directe

Info

Publication number
EP1338083A1
EP1338083A1 EP01976990A EP01976990A EP1338083A1 EP 1338083 A1 EP1338083 A1 EP 1338083A1 EP 01976990 A EP01976990 A EP 01976990A EP 01976990 A EP01976990 A EP 01976990A EP 1338083 A1 EP1338083 A1 EP 1338083A1
Authority
EP
European Patent Office
Prior art keywords
voltage
midpoint
units
series connection
direct
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.)
Withdrawn
Application number
EP01976990A
Other languages
German (de)
English (en)
Inventor
Kjell Svensson
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 AB
Original Assignee
Asea Brown Boveri AB
ABB AB
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 Asea Brown Boveri AB, ABB AB filed Critical Asea Brown Boveri AB
Publication of EP1338083A1 publication Critical patent/EP1338083A1/fr
Withdrawn legal-status Critical Current

Links

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
    • H02M7/483—Converters with outputs that each can have more than two voltages levels
    • 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
    • H02M7/483—Converters with outputs that each can have more than two voltages levels
    • H02M7/4837—Flying capacitor converters
    • 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
    • H02M1/0095—Hybrid converter topologies, e.g. NPC mixed with flying capacitor, thyristor converter mixed with MMC or charge pump mixed with buck
    • 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
    • H02M7/483—Converters with outputs that each can have more than two voltages levels
    • H02M7/487—Neutral point clamped inverters

Definitions

  • the invention relates to an apparatus for converting alternating voltage into direct voltage and conversely, which comprises a VSC-converter arranged between two poles, a positive and a negative, of a direct voltage side of the apparatus and having a series connection of at least four units each comprising a semi- conductor device and a diode connected in anti-parallel therewith, an alternating voltage phase line connected to a first midpoint, called phase output, of the series connection between two units while dividing the series connection in two equal parts, the two poles of the direct voltage side being put on substantially the same voltage but with different signs with respect to a zero voltage level of the direct voltage side, said apparatus comprising a second midpoint between two said units of one part of the series connection and which is through a flying capacitor connected to a second midpoint of the other part of the series con- nection corresponding to the second midpoint first mentioned with respect to the phase output, and an arrangement for controlling the semiconductor devices of the units to generate a train of pulses with determined amplitudes according to a pulse
  • Such apparatuses may be used in all types of situations, where direct voltage is to be converted into alternating voltage and conversely, in which examples of such uses are in stations of HVDC-plants (High Voltage Direct Current) in which direct volt- age normally is converted into a three-phase alternating voltage or conversely or in so-called back-to-back stations, where the alternating voltage is firstly converted into direct voltage and this is then converted into alternating voltage as well as in SVCs (Static Var Compensator), where the direct voltage side consists of one or more capacitors hanging freely.
  • HVDC-plants High Voltage Direct Current
  • SVCs Static Var Compensator
  • the invention is not restricted to any voltage or power levels, but it is particularly adapted for voltages on the direct voltage side between 10 and 500 kV.
  • An advantage of using such so-called multilevel converters i.e. converters in which at least three different voltage levels may be "presented" on said phase output with respect to so-called two level bridges, is that the semiconductor devices of said units may be switched with a considerably lower frequency for ob- taining an alternating voltage on the alternating voltage phase line of a determined frequency and quality, so that the losses in the converter apparatus may be reduced considerably. More exactly, the switching frequency of the semiconductor devices in a three level converter may be reduced to about A compared with a two level converter with the same generation of harmonics.
  • the voltage across the so-called outer valves of the converter may be that high that these valves have to be heavily overdimensioned, which usually is achieved by increasing the number of semiconductor devices connected in series therein. This may for example mean that the number has to be increased by about 50% above what is required in normal operation of the converter. This means of course that the costs are increased both with respect to pure component costs as well as the cost for control equipment associated therewith with respect to a need of a lower number of semiconductor devices.
  • the object of the present invention is to provide an apparatus of the type defined in the introduction, which makes it possible to solve the problems discussed above of occurrence of high voltages over said units of the converter in fault cases to a large extent.
  • This object is according to the invention obtained by providing an apparatus of the type defined in the introduction, in which each second midpoint is connected to ground through a rectifying member each with the rectifying member connected to the second midpoint closest to the positive pole with the conducting direction from ground to the second midpoint and with the rectifying member connected to the second midpoint closest to the negative pole with the conducting direction from the second midpoint to ground.
  • the voltage across the opposite outer unit will by this always receive a given value, which substantially corresponds to the po- tential difference between the pole connected thereto and zero, since the connection of ground through the rectifying member, such as a second diode, to the second midpoint will mean that the second midpoint in such a case has a potential being close to zero.
  • the voltage across the outer unit will then be completely independent of the voltage over the flying capacitor and considerably lower than otherwise would be the case, so that the number of semiconductor devices connected in series of the outer unit may be reduced and by that costs may be saved.
  • a current will now instead flow from ground through the second diode to this second midpoint and then further to the flying capacitor and the diode of the opposite part of the phase output while charging the flying capacitor and keeping the potential of the second midpoint close to ground.
  • a voltage limiting member adapted to conduct current if the voltage thereacross exceeds a determined voltage level is connected in series between each of said rectifying members and ground.
  • said voltage level of the voltage limiting member is between 5% and 20% of the voltage across the flying capacitor in normal operation of the apparatus, and more particularly about 10%.
  • Such a voltage level on the voltage limiting member means that it is reliably ensured that the other diodes will not conduct any current in normal operation, but the reduction of the voltage across the outer units (valves) will nevertheless be considerable in the fault case.
  • said semiconductor devices are IGBTs, which is advantageous, since these are suitable to connect in series and to control to turn-on and turn-off simultaneously with a high reliability, so that the semiconductor devices connected in series and included in such a unit may function as would they be one single device.
  • said direct voltage side of the apparatus is formed by a direct voltage network for transmitting high voltage direct current (HVDC) and the alternating voltage phase line belongs to an alternating voltage phase network, but it is also advantageous that the apparatus is designed to be a part of a SVC (Static Var Compensa- tor) with the direct voltage side formed by capacitors hanging freely and the alternating voltage phase line belonging to an alternating voltage phase network.
  • HVDC high voltage direct current
  • Fig 1 is a simplified circuit diagram illustrating an apparatus according to a preferred embodiment of the invention.
  • the converter apparatus is a so-called VSC-converter, which has four units 1 -4, usually called transistor valves or alternatively thyristor valves, connected in series between the two poles 5, 6 of a direct voltage side of the apparatus.
  • Two capacitors 7, 8 connected in series are arranged between said two poles, and a point 9 therebetween is usually connected to ground, so that the potentials + U/2 and - U/2 are in this way provided for the respective pole, in which U is the voltage between the two poles 5, 6. 5 is here the positive pole, while 6 is the negative pole.
  • the units 1 -4 are each formed by a semiconductor device 10-13 of turn-off type, such as an IGBT or a GTO, and a rectifying diode 14-17 connected in anti-parallel therewith, a so-called free wheeling diode.
  • a semiconductor device 10-13 of turn-off type such as an IGBT or a GTO
  • a rectifying diode 14-17 connected in anti-parallel therewith, a so-called free wheeling diode.
  • IGBT or GTO per unit is shown this may represent an amount of IGBTs or GTOs connected in series and controlled simultaneously, which also is the case, since a comparatively high number of such semiconductor devices are required for holding the voltage to be held by each unit in the blocking state.
  • a first midpoint 18 of the series connection between the two units 2 and 3, to which the phase output 19 is connected, is connected to an alternating voltage phase line 20 through an inductor 21.
  • Said series connection is in this way divided into equal parts with two units 1 , 2 and 3, 4, respectively, of each such part.
  • a tuned filter 23 consisting of ca- pacitors, reactors and resistors is connected to the alternating voltage phase line for extinguishing harmonics, which may be created on the alternating voltage phase line 20 as a consequence of the switchings of the valves.
  • a transformer 25 is also arranged for enabling a step-up or a step-down transformation of the level of the voltage out from the converter on the alternating voltage side thereof.
  • a breaker 26 is adapted to enable connection and disconnection of the alternating voltage network on the alternating voltage side downstream of the converter to and from, respectively, the converter.
  • a second midpoint 27 between two said units of one part of the series connection is through a flying capacitor 28 connected to a second midpoint 29 of the second part of the series connection corresponding to the other second midpoint with respect to the phase output.
  • the apparatus has also an arrangement 30 adapted to control the different semiconductor devices of the units 1 -4 and by that ensure that said phase output is connected to and receives the same potential as the pole 5, the pole 6 or any of said second midpoints 27 and 29, respectively, which for the midpoint 27 means the potential of the pole 6 added by the voltage across the capacitor 28 and for the midpoint 29 the voltage of the pole 5 subtracted by the voltage across the capacitor 28.
  • This arrangement 30 and the arrangement thereof is very simplified illustrated here, and a separate such arrangement would probably in the practice be arranged on high potential at each individual unit and these will then receive control signals from a control arrangement arranged on ground level.
  • a se- ries connection of a rectifying member in the form of a second diode 31 , 32 and a voltage limiting member in the form of a di- verter 33, 34 is connected with one end thereof to each said second midpoint 27, 29, while the other end of the series connection is connected to ground 35, 36.
  • the second diode of the second midpoint 27 closest to the positive pole 5 has the conducting direction from ground to the second midpoint 27, while the second diode 32 connected to the second midpoint 29 closest to the negative pole 6 has its conducting direction from the second midpoint 29 to ground.
  • the voltage level, at which the two diverters 33, 34 start to conduct is preferably about 10% of the voltage normally present between the ground point 9 and the respective pole 5, 6 in normal operation of the apparatus, i.e. for example 15 kV, would the pole voltage be 150 kV.
  • + U/2 may be obtained on the phase output by making the two units 1 , 2 conducting by turning the semiconductor devices 10 and 1 1 on, while - U/2 may be connected to the phase output by the fact that the ar- rangement 30 makes the two units 3, 4 conducting by turning the semiconductor devices 12, 13 on.
  • a voltage being substantially zero may be obtained on the phase output in two different ways, namely either by connecting the second midpoint 27 to the phase output, which is made by the fact that the ar- rangement 30 ensures that the units 2 and 4 are conducting, or by connecting the second midpoint 29 to the phase output by the fact that the control arrangement ensures that the units 1 and 3 are conducting.
  • the diodes 31 or 32 may be brought to conduct, which is not desired.
  • a voltage of -10 kV would be obtained at the second midpoint 27 when bringing the units 2 and 4 in conducting state for obtaining a zero voltage on the phase output 19, which would mean that in absence of the diverter 33 the diode 31 would be forward biased with a voltage of -10 kV and conduct current and charge the flying capacitor 28.
  • the diverter 34 has the corresponding function with respect to the diode 32.
  • the voltage of the pole conductor 5 in normal operation is 150 kV and of the pole conductor 6 -150 kV.
  • the protection voltage level of these pole conductors is +270 kV and -270 kV, respectively.
  • the potential of the two second midpoints 27 and 29 will be dependent upon which unit is conducting when the blocking takes place.
  • the series connections 31 -36 according to the invention not be there, the voltage across the outer units 1 or 4 of the units in the series connection could be twice the protection level minus the voltage across the capacitor. This would for example mean that at a voltage across the flying capacitor 28 of 150 kV when the nega- tive pole 6 is connected to the phase output, i.e. -270 kV is put thereon, the potential of the second midpoint 27 gets -120 kV, which would mean that a voltage of 390 kV would be across the outer valve 1 . The reality could then be still worse by a lower capacitor voltage then intended in any fault case.
  • the voltage across the outer valves may be reduced considerably in such a fault case. More exactly, in the fault case just described the diode 31 will start to conduct, if the negative potential of the second midpoint 27 is lower than -15 kV, so that a charging of the flying capacitor 28 takes place, so that the potential of the second midpoint 27 in such a fault case gets exactly -15 kV, which means a voltage across the outer valve 1 of 285 kV, which is to be compared with 390 kV according to above. The corresponding is achieved by the second series connection connected to the second midpoint 29 with respect to the reduction of the maximum voltage across the outer valve 4 closest to the negative pole 6.
  • Another advantage of the arrangement according to the invention of the two ground connections of the two second midpoints 27, 29 through the series connection of a second diode and a diverter is that the flying capacitor 28 will be charged very rap- idly through the diodes 15, 32 or 31 , 16 when the breaker 26 is closed for providing the converter with voltage from the alternating voltage side after operation interruption.
  • the points 35, 36 and 9 may advantageously be connected to each other and float freely.
  • the invention is particularly directed to a so-called three-level converter, it is pointed out that it is not restricted to that number of levels, but it would also be possible that the series connection comprises 2 n units, in which n is an integer > 3, and the converter has then n-1 said second midpoints located in corresponding positions with respect to the phase output on each side thereof and connected to each other through a flying capacitor.

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  • Engineering & Computer Science (AREA)
  • Power Engineering (AREA)
  • Rectifiers (AREA)
  • Inverter Devices (AREA)

Abstract

L'invention concerne un appareil permettant de convertir une tension alternative en tension directe et inversement. Cet appareil comprend un redresseur VSC qui est implanté entre deux pôles (5, 6), un pôle positif et un pôle négatif, du côté tension directe de l'appareil et qui a un montage série d'au moins quatre unités (1-4), comportant chacune un dispositif semi-conducteur (10-13) de type mise hors tension, une diode (14-17) montée antiparallèle à ce dernier et une ligne de phase tension alternative (20) raccordée à un premier point central (18), appelé sortie de phase, de la liaison série entre deux unités, ce qui divise la liaison série en deux sections égales. Les deux pôles sont, côté tension directe, sensiblement à la même tension mais avec des signes opposés par rapport à un niveau de tension zéro du côté tension directe. L'appareil a également un deuxième point central (29) qui est placé entre deux unités citées d'une section de la liaison série et qui est relié par un condensateur volant (28) à un deuxième point central correspondant de la deuxième section de la liaison série, par rapport à la sortie de phase. Chaque deuxième point central est relié à la terre respectivement par son élément redresseur (31, 32), l'élément redresseur étant relié au deuxième point central le plus proche du pôle positif avec la direction de conduction allant de la terre au deuxième point central et l'élément redresseur étant relié au deuxième point central le plus proche du pôle négatif avec la direction de conduction allant du deuxième point central à la terre.
EP01976990A 2000-11-06 2001-10-17 Appareil permettant de convertir une tension alternative en tension directe Withdrawn EP1338083A1 (fr)

Applications Claiming Priority (3)

Application Number Priority Date Filing Date Title
SE0004028 2000-11-06
SE0004028A SE519957C2 (sv) 2000-11-06 2000-11-06 Anordning för omvandling av växelspänning till likspänning
PCT/SE2001/002251 WO2002037658A1 (fr) 2000-11-06 2001-10-17 Appareil permettant de convertir une tension alternative en tension directe

Publications (1)

Publication Number Publication Date
EP1338083A1 true EP1338083A1 (fr) 2003-08-27

Family

ID=20281692

Family Applications (1)

Application Number Title Priority Date Filing Date
EP01976990A Withdrawn EP1338083A1 (fr) 2000-11-06 2001-10-17 Appareil permettant de convertir une tension alternative en tension directe

Country Status (3)

Country Link
EP (1) EP1338083A1 (fr)
SE (1) SE519957C2 (fr)
WO (1) WO2002037658A1 (fr)

Families Citing this family (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
DE112010005212B4 (de) 2010-02-01 2019-06-19 Mitsubishi Electric Corp. Dc/dc-spannungswandlervorrichtung
DE102012206955B4 (de) 2012-04-26 2016-09-22 Osram Oled Gmbh Verfahren zum Herstellen einer Streuschicht für elektromagnetische Strahlung
DE102014109048B4 (de) * 2014-06-27 2022-02-10 Sma Solar Technology Ag Schaltungsanordnung mit einer Mehrfachniveau-Halbbrückenanordnung

Family Cites Families (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
FR2752343B1 (fr) * 1996-08-09 1998-09-11 Gec Alsthom Transport Sa Dispositif electronique de conversion de l'energie electrique
DE69940533D1 (de) * 1998-07-30 2009-04-23 Koninkl Philips Electronics Nv Leistungsverstärker mit sanfter Umschaltung und Mehrpegel-Schaltzellen

Non-Patent Citations (1)

* Cited by examiner, † Cited by third party
Title
See references of WO0237658A1 *

Also Published As

Publication number Publication date
SE519957C2 (sv) 2003-04-29
SE0004028D0 (sv) 2000-11-06
SE0004028L (sv) 2002-05-07
WO2002037658A1 (fr) 2002-05-10

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