EN 62751-2:2014/A1:2019

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

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.

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

Ugotavljanje izgub moči v napetostnih pretvorniških ventilih za visokonapetostne enosmerne sisteme - 2. del: Modularni večnivojski pretvorniki (IEC 62751-2:2014/A1:2019)

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: 24-Oct-2019
• Withdrawal Date: 26-Sep-2022
• ICS: 29.200 - Rectifiers. Convertors. Stabilized power supply
• ICS: 29.240 - Power transmission and distribution networks
• Technical Committee: CLC/TC 22X - Power electronics
• Drafting Committee: IEC/SC 22F - IEC_SC_22F
• Current Stage: 6060 - Document made available - Publishing
• Start Date: 25-Oct-2019
• Completion Date: 25-Oct-2019
• Ref Project: SIST EN 62751-2:2014/A1:2020 - Power losses in voltage sourced converter (VSC) valves for high-voltage direct current (HVDC) systems - Part 2: Modular multilevel converters (IEC 62751-2:2014/A1:2019)

Relations

• Amends: EN 62751-2:2014 - Power losses in voltage sourced converter (VSC) valves for high-voltage direct current (HVDC) systems - Part 2: Modular multilevel converters
• Effective Date: 13-Jun-2017

Overview

EN 62751-2:2014/A1:2019 (IEC 62751-2:2014/A1:2019) is the European amendment for assessing power losses in voltage sourced converter (VSC) valves used in high-voltage direct current (HVDC) systems - specifically for modular multilevel converters (MMC). Published by CENELEC/CLC in 2019, this amendment updates the original Part 2 guidance and clarifies measurement, simulation and reporting practices for valve loss determination in MMC-based HVDC converter stations.

Key topics and requirements

• Scope: Loss determination methods for VSC valve components in MMC topologies (IGBTs, diodes, submodules, valve electronics, snubbers, interconnects).
• Loss calculation principles: Emphasis on accurate system modelling, numerical simulation, and iterative calculation of semiconductor junction temperatures to derive conduction and switching losses.
• Input data & simulation rules:
  • Simplified models may use worst‑case on-state and switching characteristics at maximum rated junction temperature for basic current calculations.
  • Detailed loss calculations must include junction‑temperature dependent properties from device characterisation (see IEC 62751-1:2014).
  • Integration time for simulations shall not be less than 1 s.
• Conduction loss modelling:
  • Recommended piecewise‑linear representation of on‑state voltages (threshold V0 and slope R0) measured at 100% and 33% rated current for transparency and good accuracy.
  • Option to use polynomial device models if specified by purchaser to improve accuracy.
• Testing & measurement:
  • Characterisation tests must account for snubber influence and valve electronics power consumption.
  • Valve electronics power should be measured on a sample size (minimum equivalent to five submodules or 10 VSC valve levels for CTL designs).
• Reporting & uncertainty:
  • Manufacturers/bidders must submit a detailed valve loss determination report documenting assumptions, characterisation/routine test data and breakdown of losses; uncertainties must be justified.
  • Only total valve losses are typically used for commercial evaluation, though constituent breakdowns are requested.
• Notes on no‑load state: Occasional balancing switching in no‑load can cause measurable losses and should be considered.

Applications

• Specifying loss guarantees in HVDC procurements
• Designing and validating MMC converter stations for utilities and OEMs
• Thermal management, cooling and reliability studies for converter valves
• Tender evaluation and contract acceptance testing where valve losses affect operational cost and efficiency

Who uses this standard

• HVDC converter manufacturers and bidders
• Utilities and transmission system operators preparing procurement specifications
• Power electronics and system design engineers
• Test laboratories and certification bodies
• Consultants performing loss, efficiency and lifecycle-cost analyses

Related standards

• IEC 62751-1:2014 (characterisation of VSC valve semiconductors)
• IEC 61803 (determination of power losses in HVDC converter stations)
• CIGRÉ WG outputs (measurement feasibility studies, e.g., WG B4‑75)

Keywords: EN 62751-2:2014/A1:2019, IEC 62751-2, VSC valves, HVDC, MMC, power losses, valve loss determination, IGBT conduction losses, junction temperature, valve electronics.

Standards Content (Sample)

SLOVENSKI STANDARD
01-januar-2020
Ugotavljanje izgub moči v napetostnih pretvorniških ventilih za visokonapetostne
enosmerne sisteme - 2. del: Modularni večnivojski pretvorniki (IEC 62751-
2:2014/A1:2019)
Power losses in voltage sourced converter (VSC) valves for high-voltage direct current
(HVDC) systems - Part 2: Modular multilevel converters (IEC 62751-2:2014/A1:2019)
Bestimmung der Leistungsverluste in Spannungszwischenkreis-Stromrichtern (VSC) für
Hochspannungsgleichstrom(HGÜ)-Systeme - Teil 2: Modulare Mehrpunkt-Stromrichter
(IEC 62751-2:2014/A1:2019)
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 (IEC 62751-2:2014/A1:2019)
Ta slovenski standard je istoveten z: EN 62751-2:2014/A1:2019
ICS:
29.200 Usmerniki. Pretvorniki. Rectifiers. Convertors.
Stabilizirano električno Stabilized power supply
napajanje
29.240.01 Omrežja za prenos in Power transmission and
distribucijo električne energije distribution networks in
na splošno general
2003-01.Slovenski inštitut za standardizacijo. Razmnoževanje celote ali delov tega standarda ni dovoljeno.

EUROPEAN STANDARD EN 62751-2:2014/A1

NORME EUROPÉENNE
EUROPÄISCHE NORM
October 2019
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/A1:2019)
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 Mehrpunkt-Stromrichter
(IEC 62751-2:2014/A1:2019) (IEC 62751-2:2014/A1:2019)
This amendment A1 modifies the European Standard EN 62751-2:2014; it was approved by CENELEC on 2019-09-27. CENELEC
members are bound to comply with the CEN/CENELEC Internal Regulations which stipulate the conditions for giving this amendment 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 amendment 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, France, Germany, Greece, Hungary, Iceland, Ireland, Italy, Latvia, Lithuania, Luxembourg, Malta, the
Netherlands, Norway, Poland, Portugal, Republic of North Macedonia, Romania, Serbia, 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: Rue de la Science 23, B-1040 Brussels
© 2019 CENELEC All rights of exploitation in any form and by any means reserved worldwide for CENELEC Members.
Ref. No. EN 62751-2:2014/A1:2019 E

European foreword
The text of document 22F/479/CDV, future IEC 62751-2/A1, 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
The following dates are fixed:
• latest date by which the document has to be implemented at national (dop) 2020-06-27
level by publication of an identical national standard or by endorsement
• latest date by which the national standards conflicting with the (dow) 2022-09-27
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 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/A1:2019 was approved by CENELEC as a
European Standard without any modification.

Annex ZA
(normative)
Normative references to international publications
with their corresponding European publications
The following documents are referred to in the text in such a way that some or all of their content
constitutes requirements of this document. For dated references, only the edition cited applies. For
undated references, the latest edition of the referenced document (including any amendments)
applies.
NOTE 1  Where 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 61803 -  Determination of power losses in high- EN 61803 -
voltage direct current (HVDC) converter
stations
IEC 62751-2 ®
Edition 1.0 2019-08
INTERNATIONAL
STANDARD
NORME
INTERNATIONALE
colour
inside
A MENDMENT 1
AM ENDEMENT 1
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
INTERNATIONALE
ICS 29.200; 29.240 ISBN 978-2-8322-7218-3

– 2 – IEC 62751-2:2014/AMD1:2019
© IEC 2019
FOREWORD
This amendment 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 amendment is based on the following documents:
CDV Report on voting
22F/479/CDV 22F/488B/RVC
Full information on the voting for the approval of this amendment can be found in the report
on voting indicated in the above table.
The committee has decided that the contents of this amendment and the base publication will
remain unchanged until the stability date indicated on the IEC website 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.
_____________
2 Normative references
Add the following new reference:
IEC 61803, Determination of power losses in high-voltage direct current (HVDC) converter
stations
3.1.11
no-load operating state
Add, after the existing definition, the following new note:
Note 1 to entry: In the no-load state, in principle no switching should occur as the valve is blocked. However, in
some designs, it may be necessary to make occasional switching operations to balance voltages between different
parts of the converter. Here, some losses may occur and need to be accounted for.

IEC 62751-2:2014/AMD1:2019 – 3 –
© IEC 2019
4 General conditions
4.1 General
Replace, in the third sentence of the existing paragraph, the abbreviated term "CTLC" by
"CTL".
4.2 Principles for loss determination
Add, to the end of the first existing paragraph, the following new sentence:
The manufacturer shall justify, in the loss calculation report, how the uncertainties have been
considered.
Replace the last two sentences of the third existing paragraph by the following new sentences:
In practice, this measurement would require the use of state-of-the-art measurement
equipment that rivals the best equipment available at national metrology institutes. To date,
although some industry/academic partnership projects have demonstrated prototypes of
measurement equipment claiming sufficient accuracy, there is little industry experience with
using such equipment on site. The feasibility of using laboratory measurements on VSC
valves to support a more accurate determination of valve losses is now under study in
CIGRÉ WG B4-75.
4.4 Loss calculation method
Replace the first sentence of the existing second paragraph by the following new sentence:
An important requirement for such simulations is an accurate modelling of the system under
investigation.
4.5.2 Input data for numerical simulations
Replace the last item of the existing dash list by the following new items:
– For calculating converter valve currents and MMC building block capacitor currents, which
are the basis for the calculation of corresponding losses, it is sufficient to use a simplified
model in which the on-state and switching characteristics of the IGBTs and diodes are
represented by worst-case characteristics applicable to their maximum rated junction
temperature.
– For the detailed calculation of losses, the simulation shall also consider the junction
temperature dependent semiconductor properties, such as on-state voltages, switching
and recovery losses. These properties are based on the characterisation testing as
described in IEC 62751-1:2014, 4.4.2. The steady-state junction temperatures of the
semiconductors are calculated iteratively for the relevant operating point to derive the
semiconductor losses.
4.5.3 Input data coming from numerical simulations
Add, to the last existing paragraph, the following new sentence:
The mean and rms currents in IGBTs and diodes are not required if conduction losses in
IGBTs and diodes are calculated using polynomials as discussed in 5.1.
4.5.4 Converter station data
Add, to the sixth dash of the existing list, the words "(for CTL designs)".

– 4 – IEC 62751-2:2014/AMD1:2019
© IEC 2019
Add, after the existing 4.5.5, the following new subclause:
4.6 Contents and structure of valve loss determination report
The manufacturer or bidder shall prepare and submit to the purchaser a detailed report
explaining how the losses in the VSC valves have been determined and including a
breakdown of the valve losses into the constituent parts P to P for each operating
V1 V9
condition at which losses are required to be guaranteed.
At the bid stage, and (where requested in the contract) after contract award but before the
manufacturing of valve components, the report shall document the assumptions used in
arriving at the calculated value of losses. After manufacturing, the report shall document the
actual values of test data derived from characterisation tests and routine tests on components.
Although a breakdown of the valve losses into the constituent parts P to P is requested,
V1 V9
only the total valve losses P shall be subject to financial evaluation.
Vt
A recommended list of data to be included in the report is presented in Annex B.
5.1 General
Add, after the existing Figure 2, the following new paragraphs:
To simplify the process of mathematically analysing conduction losses, the on-state voltage of
IGBTs and diodes is usually represen
...