Power losses in voltage sourced converter (VSC) valves for high-voltage direct current (HVDC) systems - Part 2: Modular multilevel converters

IEC 62751-2:2014 gives the detailed method to be adopted for calculating the power losses in the valves for an HVDC system based on the "modular multi-level converter", where each valve in the converter consists of a number of self-contained, two-terminal controllable voltage sources connected in series. It is applicable both for the cases where each modular cell uses only a single turn-off semiconductor device in each switch position, and the case where each switch position consists of a number of turn-off semiconductor devices in series (topology also referred to as "cascaded two-level converter"). The main formulae are given for the two-level "half-bridge" configuration but guidance is also given as to how to extend the results to certain other types of MMC building block configuration.

Bestimmung der Leistungsverluste in Spannungszwischenkreis-Stromrichtern (VSC) für Hochspannungsgleichstrom(HGÜ)-Systeme - Teil 2: Modulare Mehrpunkt-Stromrichter

Pertes de puissance dans les valves à convertisseur de source de tension (VSC) des systèmes en courant continu à haute tension (CCHT) - Partie 2: Convertisseurs multiniveaux modulaires

L'IEC 62571-2:2014 donne la méthode détaillée à adopter pour calculer les pertes de puissance dans les valves d'un système CCHT doté d'un "convertisseur multiniveaux modulaire" dont chaque valve est composée d'un certain nombre de sources de tension indépendantes commandables à deux bornes connectées en série. Elle s'applique lorsque chaque cellule modulaire n'utilise qu'un seul dispositif à semi-conducteur blocable dans chaque position de commutation, et lorsque chaque position de commutation est composée d'un certain nombre de dispositifs à semi-conducteur blocables en série (cette topologie étant également appelée "convertisseur à deux niveaux monté en cascade"). Les principales formules sont données pour la configuration "en demi-pont" à deux niveaux. Des lignes directrices sont également données pour indiquer l'étendue des résultats de certains autres types de configurations de bloc module MMC.

Ugotavljanje izgub moči v napetostnih pretvorniških ventilih za visokonapetostne enosmerne sisteme - 2. del: Modularni večnivojski pretvorniki (IEC 62751-2:2014)

Ta del standarda IEC 62751 podaja podrobno metodo, ki naj bi se sprejela za izračun izgub moči v ventilih za sistem HVDC na osnovi »modularnega večnivojskega pretvornika«, pri katerem je vsak ventil v pretvorniku sestavljen iz številnih zaporedno vezanih samostojnih, krmiljenih napetostnih virov z dvema priključkoma. Uporablja se v primerih, kjer je posamezna modularna celica uporablja samo eno izklopno polprevodniško napravo pri vsakem stikalnem položaju, in v primerih, kjer posamezni stikalni položaj vsebuje več zaporedno vezanih izklopnih polprevodniških naprav (topologija: imenovan tudi »kaskadni dvonivojski pretvornik«). Glavne formule so podane za dvonivojsko »pol mostično« konfiguracijo, vendar so v dodatku A podane tudi smernice, kako rezultate razširiti na določene druge vrste konfiguracije gradnikov MMC. Standard je zapisan zlasti za bipolarne tranzistorje z izoliranimi vrati (IGBT), vendar se lahko uporablja tudi za navodila v primeru, da se uporabljajo druge vrste izklopnih polprevodniškh naprav.
Izgube moči v drugih elementih opreme v napravi HVDC, razen pretvorniških ventilov, so izključene iz področja uporabe tega standarda. Ta standard se ne uporablja za pretvorniške ventile za sisteme HVDC s pretvorniki z linijsko komutacijo.

General Information

Status
Published
Publication Date
30-Oct-2014
Technical Committee
Drafting Committee
Current Stage
6060 - Document made available
Due Date
31-Oct-2014
Completion Date
31-Oct-2014

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SLOVENSKI STANDARD
SIST EN 62751-2:2014
01-december-2014
8JRWDYOMDQMHL]JXEPRþLYQDSHWRVWQLKSUHWYRUQLãNLKYHQWLOLK]DYLVRNRQDSHWRVWQH
HQRVPHUQHVLVWHPHGHO0RGXODUQLYHþQLYRMVNLSUHWYRUQLNL ,(&
Determination of power losses in voltage sourced converter (VSC) valves for high
voltage direct current (HVDC) systems - Part 2: Modular multilevel converters

Bestimmung der Leistungsverluste in Spannungszwischenkreis-Stromrichtern (VSC) für

Hochspannungsgleichstrom(HGÜ)-Systeme -- Teil 2: Modulare Mehrstufen-Stromrichter

Determination des pertes de puissance dans les valves à convertisseur de source de

tension (VSC) des systemes en courant continu a haute tension (CCHT) -- Partie 2:

Convertisseurs multiniveaux modulaires
Ta slovenski standard je istoveten z: EN 62751-2:2014
ICS:
29.200 8VPHUQLNL3UHWYRUQLNL Rectifiers. Convertors.
6WDELOL]LUDQRHOHNWULþQR Stabilized power supply
QDSDMDQMH
29.240.01 2PUHåMD]DSUHQRVLQ Power transmission and
GLVWULEXFLMRHOHNWULþQHHQHUJLMH distribution networks in
QDVSORãQR general
SIST EN 62751-2:2014 en

2003-01.Slovenski inštitut za standardizacijo. Razmnoževanje celote ali delov tega standarda ni dovoljeno.

---------------------- Page: 1 ----------------------
SIST EN 62751-2:2014
---------------------- Page: 2 ----------------------
SIST EN 62751-2:2014
EUROPEAN STANDARD EN 62751-2
NORME EUROPÉENNE
EUROPÄISCHE NORM
October 2014
ICS 29.200; 29.240
English Version
Power losses in voltage sourced converter (VSC) valves for
high-voltage direct current (HVDC) systems - Part 2: Modular
multilevel converters
(IEC 62751-2:2014)

Pertes de puissance dans les valves à convertisseur de Bestimmung der Leistungsverluste in

source de tension (VSC) des systèmes en courant continu Spannungszwischenkreis-Stromrichtern (VSC) für

à haute tension (CCHT) - Partie 2: Convertisseurs Hochspannungsgleichstrom(HGÜ)-Systeme - Teil 2:

multiniveaux modulaires Modulare Mehrstufen-Stromrichter
(CEI 62751-2:2014) (IEC 62751-2:2014)

This European Standard was approved by CENELEC on 2014-10-01. CENELEC members are bound to comply with the CEN/CENELEC

Internal Regulations which stipulate the conditions for giving this European Standard the status of a national standard without any alteration.

Up-to-date lists and bibliographical references concerning such national standards may be obtained on application to the CEN-CENELEC

Management Centre or to any CENELEC member.

This European Standard exists in three official versions (English, French, German). A version in any other language made by translation

under the responsibility of a CENELEC member into its own language and notified to the CEN-CENELEC Management Centre has the

same status as the official versions.

CENELEC members are the national electrotechnical committees of Austria, Belgium, Bulgaria, Croatia, Cyprus, the Czech Republic,

Denmark, Estonia, Finland, Former Yugoslav Republic of Macedonia, France, Germany, Greece, Hungary, Iceland, Ireland, Italy, Latvia,

Lithuania, Luxembourg, Malta, the Netherlands, Norway, Poland, Portugal, Romania, Slovakia, Slovenia, Spain, Sweden, Switzerland,

Turkey and the United Kingdom.
European Committee for Electrotechnical Standardization
Comité Européen de Normalisation Electrotechnique
Europäisches Komitee für Elektrotechnische Normung
CEN-CENELEC Management Centre: Avenue Marnix 17, B-1000 Brussels

© 2014 CENELEC All rights of exploitation in any form and by any means reserved worldwide for CENELEC Members.

Ref. No. EN 62751-2:2014 E
---------------------- Page: 3 ----------------------
SIST EN 62751-2:2014
EN 62751-2:2014 - 2 -
Foreword

The text of document 22F/303/CDV, future edition 1 of IEC 62751-2, prepared by SC 22F "Power

electronics for electrical transmission and distribution systems", of IEC/TC 22 "Power electronic

systems and equipment" was submitted to the IEC-CENELEC parallel vote and approved by

CENELEC as EN 62751-2:2014.
The following dates are fixed:
– latest date by which the document has to be implemented at (dop) 2015-07-01
national level by publication of an identical national
standard or by endorsement
– latest date by which the national standards conflicting with (dow) 2017-10-01
the document have to be withdrawn

Attention is drawn to the possibility that some of the elements of this document may be the subject of

patent rights. CENELEC [and/or CEN] shall not be held responsible for identifying any or all such

patent rights.
Endorsement notice

The text of the International Standard IEC 62751-2:2014 was approved by CENELEC as a European

Standard without any modification.

In the official version, for Bibliography, the following note has to be added for the standard indicated:

IEC 61803:1999 NOTE Harmonised as EN 61803:1999.
---------------------- Page: 4 ----------------------
SIST EN 62751-2:2014
- 3 - EN 62751-2:2014
Annex ZA
(normative)
Normative references to international publications
with their corresponding European publications

The following documents, in whole or in part, are normatively referenced in this document and are

indispensable for its application. For dated references, only the edition cited applies. For undated

references, the latest edition of the referenced document (including any amendments) applies.

NOTE 1 When an International Publication has been modified by common modifications, indicated by (mod),

the relevant EN/HD applies.

NOTE 2 Up-to-date information on the latest versions of the European Standards listed in this annex is

available here: www.cenelec.eu.
Publication Year Title EN/HD Year
IEC 60633 - Terminology for high-voltage direct current EN 60633 -
(HVDC) transmission
IEC 62747 - Terminology for voltage-sourced EN 62747 -
converters (VSC) for high-voltage direct
current (HVDC) systems
IEC 62751-1 2014 Determination of power losses in voltage EN 62751-1 2014
sourced converter (VSC) valves for high-
voltage direct current (HVDC) systems --
Part 1: General requirements
ISO/IEC Guide 98-3 - Uncertainty of measurement -- Part-3: - -
Guide to the expression of uncertainty in
measurement (GUM:1995)
---------------------- Page: 5 ----------------------
SIST EN 62751-2:2014
---------------------- Page: 6 ----------------------
SIST EN 62751-2:2014
IEC 62751-2
Edition 1.0 2014-08
INTERNATIONAL
STANDARD
NORME
INTERNATIONALE
colour
inside
Power losses in voltage sourced converter (VSC) valves for high-voltage direct
current (HVDC) systems –
Part 2: Modular multilevel converters
Pertes de puissance dans les valves à convertisseur de source de tension (VSC)
des systèmes en courant continu à haute tension (CCHT) –
Partie 2: Convertisseurs multiniveaux modulaires
INTERNATIONAL
ELECTROTECHNICAL
COMMISSION
COMMISSION
ELECTROTECHNIQUE
PRICE CODE
INTERNATIONALE
CODE PRIX XA
ICS 29.200; 29.240 ISBN 978-2-8322-1836-5

Warning! Make sure that you obtained this publication from an authorized distributor.

Attention! Veuillez vous assurer que vous avez obtenu cette publication via un distributeur agréé.

® Registered trademark of the International Electrotechnical Commission
Marque déposée de la Commission Electrotechnique Internationale
---------------------- Page: 7 ----------------------
SIST EN 62751-2:2014
– 2 – IEC 62751-2:2014 © IEC 2014
CONTENTS

FOREWORD ........................................................................................................................... 5

1 Scope .............................................................................................................................. 7

2 Normative references ...................................................................................................... 7

3 Terms, definitions, symbols and abbreviated terms .......................................................... 7

3.1 Terms and definitions .............................................................................................. 8

3.2 Symbols and abbreviated terms .............................................................................. 9

3.2.1 Valve and simulation data ................................................................................ 9

3.2.2 Semiconductor device characteristics ............................................................ 10

3.2.3 Other component characteristics.................................................................... 10

3.2.4 Operating parameters .................................................................................... 10

3.2.5 Loss parameters ............................................................................................ 11

4 General conditions......................................................................................................... 11

4.1 General ................................................................................................................. 11

4.2 Principles for loss determination ........................................................................... 12

4.3 Categories of valve losses .................................................................................... 12

4.4 Loss calculation method ........................................................................................ 13

4.5 Input parameters ................................................................................................... 13

4.5.1 General ......................................................................................................... 13

4.5.2 Input data for numerical simulations .............................................................. 13

4.5.3 Input data coming from numerical simulations ............................................... 14

4.5.4 Converter station data ................................................................................... 14

4.5.5 Operating conditions ...................................................................................... 15

5 Conduction losses ......................................................................................................... 15

5.1 General ................................................................................................................. 15

5.2 IGBT conduction losses ........................................................................................ 16

5.3 Diode conduction losses ....................................................................................... 17

5.4 Other conduction losses ........................................................................................ 18

6 DC voltage-dependent losses ........................................................................................ 19

7 Losses in d.c. capacitors of the valve ............................................................................ 19

8 Switching losses ............................................................................................................ 20

8.1 General ................................................................................................................. 20

8.2 IGBT switching losses ........................................................................................... 20

8.3 Diode switching losses .......................................................................................... 21

9 Other losses .................................................................................................................. 21

9.1 Snubber circuit losses ........................................................................................... 21

9.2 Valve electronics power consumption.................................................................... 22

9.2.1 General ......................................................................................................... 22

9.2.2 Power supply from off-state voltage across each IGBT .................................. 23

9.2.3 Power supply from the d.c. capacitor ............................................................. 23

10 Total valve losses per HVDC substation ........................................................................ 24

Annex A (informative) Description of power loss mechanisms in MMC valves ...................... 26

A.1 Introduction to MMC Converter topology ............................................................... 26

A.2 Valve voltage and current stresses ....................................................................... 29

A.2.1 Simplified analysis with voltage and current in phase ..................................... 29

A.2.2 Generalised analysis with voltage and current out of phase ........................... 30

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SIST EN 62751-2:2014
IEC 62751-2:2014 © IEC 2014 – 3 –

A.2.3 Effects of third harmonic injection .................................................................. 31

A.3 Conduction losses in MMC building blocks ............................................................ 32

A.3.1 Description of conduction paths ..................................................................... 32

A.3.2 Conduction losses in semiconductors ............................................................ 38

A.3.3 MMC building block d.c. capacitor losses ....................................................... 42

A.3.4 Other conduction losses ................................................................................ 42

A.4 Switching losses ................................................................................................... 42

A.4.1 Description of state changes .......................................................................... 42

A.4.2 Analysis of state changes during cycle .......................................................... 44

A.4.3 Worked example of switching losses .............................................................. 44

A.5 Other losses ......................................................................................................... 47

A.5.1 Snubber losses .............................................................................................. 47

A.5.2 DC voltage-dependent losses ........................................................................ 47

A.5.3 Valve electronics power consumption ............................................................ 50

A.6 Application to other variants of valve..................................................................... 52

A.6.1 General ......................................................................................................... 52

A.6.2 Two-level full-bridge MMC building block ....................................................... 52

A.6.3 Multi-level MMC building blocks ..................................................................... 53

Bibliography .......................................................................................................................... 55

Figure 1 – Two basic versions of MMC building block designs .............................................. 15

Figure 2 – Conduction paths in MMC building blocks ............................................................ 16

Figure A.1 – Phase unit of the modular multi-level converter (MMC) in basic half-

bridge, two-level arrangement, with submodules ................................................................... 27

Figure A.2 – Phase unit of the cascaded two-level converter (CTL) in half-bridge form ......... 28

Figure A.3 – Basic operation of the MMC converters ............................................................. 29

Figure A.4 – MMC converters showing composition of valve current ..................................... 30

Figure A.5 – Phasor diagram showing a.c. system voltage, converter a.c. voltage and

converter a.c. current ............................................................................................................ 31

Figure A.6 – Effect of 3 harmonic injection on converter voltage and current ..................... 32

Figure A.7 – Two functionally equivalent variants of a “half-bridge”, two-level MMC

building block ........................................................................................................................ 33

Figure A.8 – Conducting states in “half-bridge”, two-level MMC building block ...................... 34

Figure A.9 – Typical patterns of conduction for inverter operation (left) and rectifier

operation (right) .................................................................................................................... 35

Figure A.10 – Example of converter with only one MMC building block per valve to

illustrate switching behaviour ................................................................................................ 36

Figure A.11 – Inverter operation example of switching events ............................................... 36

Figure A.12 – Rectifier operation example of switching events .............................................. 37

Figure A.13 – Valve current and mean rectified valve current ................................................ 39

Figure A.14 – IGBT and diode switching energy as a function of collector current ................. 43

Figure A.15 – Valve voltage, current and switching behaviour for a hypothetical MMC

valve consisting of 5 submodules .......................................................................................... 45

Figure A.16 – Power supply from IGBT terminals .................................................................. 50

Figure A.17 – Power supply from IGBT terminals in cell ........................................................ 51

Figure A.18 – Power supply from d.c. capacitor in submodule ............................................... 52

Figure A.19 – One “full-bridge”, two-level MMC building block .............................................. 52

---------------------- Page: 9 ----------------------
SIST EN 62751-2:2014
– 4 – IEC 62751-2:2014 © IEC 2014

Figure A.20 – Four possible variants of three-level MMC building block ................................ 54

Table 1 – Contributions to valve losses in different operating modes .................................... 25

Table A.1 – Hard switching events ........................................................................................ 42

Table A.2 – Soft switching events ......................................................................................... 44

Table A.3 – Summary of switching events from Figure A.15 .................................................. 46

---------------------- Page: 10 ----------------------
SIST EN 62751-2:2014
IEC 62751-2:2014 © IEC 2014 – 5 –
INTERNATIONAL ELECTROTECHNICAL COMMISSION
____________
POWER LOSSES IN VOLTAGE SOURCED
CONVERTER (VSC) VALVES FOR HIGH-VOLTAGE
DIRECT CURRENT (HVDC) SYSTEMS –
Part 2: Modular multilevel converters
FOREWORD

1) The International Electrotechnical Commission (IEC) is a worldwide organization for standardization comprising

all national electrotechnical committees (IEC National Committees). The object of IEC is to promote

international co-operation on all questions concerning standardization in the electrical and electronic fields. To

this end and in addition to other activities, IEC publishes International Standards, Technical Specifications,

Technical Reports, Publicly Available Specifications (PAS) and Guides (hereafter referred to as “IEC

Publication(s)”). Their preparation is entrusted to technical committees; any IEC National Committee interested

in the subject dealt with may participate in this preparatory work. International, governmental and non-

governmental organizations liaising with the IEC also participate in this preparation. IEC collaborates closely

with the International Organization for Standardization (ISO) in accordance with conditions determined by

agreement between the two organizations.

2) The formal decisions or agreements of IEC on technical matters express, as nearly as possible, an international

consensus of opinion on the relevant subjects since each technical committee has representation from all

interested IEC National Committees.

3) IEC Publications have the form of recommendations for international use and are accepted by IEC National

Committees in that sense. While all reasonable efforts are made to ensure that the technical content of IEC

Publications is accurate, IEC cannot be held responsible for the way in which they are used or for any

misinterpretation by any end user.

4) In order to promote international uniformity, IEC National Committees undertake to apply IEC Publications

transparently to the maximum extent possible in their national and regional publications. Any divergence

between any IEC Publication and the corresponding national or regional publication shall be clearly indicated in

the latter.

5) IEC itself does not provide any attestation of conformity. Independent certification bodies provide conformity

assessment services and, in some areas, access to IEC marks of conformity. IEC is not responsible for any

services carried out by independent certification bodies.

6) All users should ensure that they have the latest edition of this publication.

7) No liability shall attach to IEC or its directors, employees, servants or agents including individual experts and

members of its technical committees and IEC National Committees for any personal injury, property damage or

other damage of any nature whatsoever, whether direct or indirect, or for costs (including legal fees) and

expenses arising out of the publication, use of, or reliance upon, this IEC Publication or any other IEC

Publications.

8) Attention is drawn to the Normative references cited in this publication. Use of the referenced publications is

indispensable for the correct application of this publication.

9) Attention is drawn to the possibility that some of the elements of this IEC Publication may be the subject of

patent rights. IEC shall not be held responsible for identifying any or all such patent rights.

International Standard IEC 62751-2 has been prepared by subcommittee 22F: Power

electronics for electrical transmission and distribution systems, of IEC technical committee 22:

Power electronic systems and equipment.
The text of this standard is based on the following documents:
CDV Report on voting
22F/303/CDV 22F/322A/RVC

Full information on the voting for the approval of this standard can be found in the report on

voting indicated in the above table.

This publication has been drafted in accordance with the ISO/IEC Directives, Part 2.

---------------------- Page: 11 ----------------------
SIST EN 62751-2:2014
– 6 – IEC 62751-2:2014 © IEC 2014

A list of all parts in the IEC 62751series, published under the general title Power losses in

voltage sourced converter (VSC) valves for high-voltage direct current (HVDC) systems, can

be found on the IEC website.

The committee has decided that the contents of this publication will remain unchanged until

the stability date indicated on the IEC web site under "http://webstore.iec.ch" in the data

related to the specific publication. At this date, the publication will be
• reconfirmed,
• withdrawn,
• replaced by a revised edition, or
• amended.

IMPORTANT – The 'colour inside' logo on the cover page of this publication indicates

that it contains colours which are considered to be useful for the correct

understanding of its contents. Users should therefore print this document using a

colour printer.
---------------------- Page: 12 ----------------------
SIST EN 62751-2:2014
IEC 62751-2:2014 © IEC 2014 – 7 –
POWER LOSSES IN VOLTAGE SOURCED
CONVERTER (VSC) VALVES FOR HIGH-VOLTAGE
DIRECT CURRENT (HVDC) SYSTEMS –
Part 2: Modular multilevel converters
1 Scope

This part of IEC 62751 gives the detailed method to be adopted for calculating the power

losses in the valves for an HVDC system based on the “modular multi-level converter”, where

each valve in the converter consists of a number of self-contained, two-terminal controllable

voltage sources connected in series. It is applicable both for the cases where each modular

cell uses only a single turn-off semiconductor device in each switch position, and the case

where each switch position consists of a number of turn-off semiconductor devices in series

(topology also referred to as “cascaded two-level converter”). The main formulae are given for

the two-level “half-bridge” configuration but guidance is also given in Annex A as to how to

extend the results to certain other types of MMC building block configuration.

The standard is written mainly for insulated gate bipolar transistors (IGBTs) but may also be

used for guidance in the event that other types of turn-off semiconductor devices are used.

Power losses in other items of equipment in the HVDC station, apart from the converter

valves, are excluded from the scope of this standard.

This standard does not apply to converter valves for line-commutated converter HVDC

systems.
2 Normative references

The following documents, in whole or in part, are normatively referenced in this document and

are indispensable for its application. For dated references, only the edition cited applies. For

undated references, the latest edition of the referenced document (including any
amendments) applies.
IEC 60633, Terminology for high-voltage direct-current (HVDC) transmission

IEC 62747, Terminology for voltage-sourced converters (VSC) for high-voltage direct current

(HVDC) systems

IEC 62751-1:2014, Power losses in voltage sourced converter (VSC) valves for high-voltage

direct current (HVDC) systems – Part 1: General requirements

ISO/IEC Guide 98-3, Uncertainty of measurement – Part 3: Guide to the expression of

uncertainty in measurement (GUM:1995)
3 Terms, definitions, symbols and abbreviated terms

For the purposes of this document, the terms and definitions given in IEC 60633, IEC 62747,

IEC 62751-1, as well as the following apply.
---------------------- Page: 13 ----------------------
SIST EN 62751-2:2014
– 8 – IEC 62751-2:2014 © IEC 2014
3.1 Terms and definitions
3.1.1
modular multi-level converter
MMC

multi-level converter in which each VSC valve consists of a number of MMC building blocks

connected in series
Note 1 to entry: This note applies to the French language only.
3.1.2
MMC building block

self-contained, two-terminal controllable voltage source together with d.c. capacitor(s) and

immediate auxiliaries, forming part of a MMC
3.1.3
IGBT-diode pair
arrangement of IGBT and free-wheeling diode connected in inverse parallel
3.1.4
switch position
semiconductor function which behaves as a single, indivisible switch

Note 1 to entry: A switch position may consist of a single IGBT-diode pair or, in the case of the cascaded two

level converter, a series connection of multiple IGBT-diode pairs.
3.1.5
cascaded two-level converter
CTL

modular multi-level converter in which each switch position consists of more than one

IGBT-diode pair connected in series
Note 1 to entry: This note applies to the French language only.
3.1.6
submodule

MMC building block where each switch position consists of only one IGBT-diode pair

3.1.7
cell

MMC building block where each switch position consists of more than one IGBT-diode pair

connected in series
3.1.8
turn-off semiconductor device

controllable semiconductor device which may be turned on and off by a control signal, for

example an IGBT
3.1.9
insulated gate bipolar transistor
IGBT

turn-off semiconductor device with three terminals: a gate terminal (G) and two load terminals

emitter (E) and collector (C)
Note 1 to entry: This note applies to the French language only.
3.1.10
operating state

condition in which the HVDC substation is energized and the converters are de-blocked

---------------------- Page: 14 ----------------------
SIST EN 62751-2:2014
IEC 62751-2:2014 © IEC 2014 – 9 –

Note 1 to entry: Unlike line-commutated converter, VSC can operate with zero active/reactive power output.

3.1.11
no-load operating state

condition in which the HVDC substation is energized but the IGBTs are blocked and all

necessary substation service loads and auxiliary equipment are connected
3.1.12
idling operating state

condition in which the HVDC substation is energized and the IGBTs are de-blocked but with

no active or reactive power output at the point of common connection to the a.c. network

Note 1 to entry: The “idling operating” and “no-load” conditions are similar but from the no-load state, several

seconds may be needed before power can be transmitted, while from the idling operating state, power transmission

may be commenced almost immediately (less than 3 power frequency cycles).

Note 2 to entry: In the idling operating state, the converter is capable of actively controlling the d.c. voltage, in

contrast to the no-load state where the behavior of the converter is essentially “passive”.

Note 3 to entry: Losses will generally be slightly lower in the no-load state than in the idling operating state,

therefore this operating mode is preferred where the arrangement of the VSC system permits it.

3.1.13
modulation index of PWM converters

ratio of the peak line to ground a.c. converter voltage, to half of the converter d.c. terminal to

terminal voltage
2 ⋅U
M =
3 ⋅
where

U is the r.m.s value of the fundamental frequency component of the line-to-line voltage U ;

c1 c
U is the output voltag
...

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