IEC 62751-2:2014/AMD2:2023

IEC 62751-2 ®
Edition 1.0 2023-08
INTERNATIONAL
STANDARD
NORME
INTERNATIONALE
AMENDMENT 2
AMENDEMENT 2
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
IEC 62751-2:2014-08/AMD2:2023-08(en-fr)

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IEC 62751-2 ®
Edition 1.0 2023-08
INTERNATIONAL
STANDARD
NORME
INTERNATIONALE
AMENDMENT 2
AMENDEMENT 2
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, 29.240.99 ISBN 978-2-8322-7446-0

– 2 – IEC 62751-2:2014/AMD2:2023
© IEC 2023
INTERNATIONAL ELECTROTECHNICAL COMMISSION
____________
POWER LOSSES IN VOLTAGE SOURCED
CONVERTER (VSC) VALVES FOR HIGH-VOLTAGE
DIRECT CURRENT (HVDC) SYSTEMS –

Part 2: Modular multilevel converters

AMENDMENT 2
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
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Standardization (ISO) in accordance with conditions determined by agreement between the two organizations.
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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
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9) Attention is drawn to the possibility that some of the elements of this document may be the subject of patent
rights. IEC shall not be held responsible for identifying any or all such patent rights.
Amendment 2 to IEC 62751-2:2014 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:
Draft Report on voting
22F/712/CDV 22F/726/RVC
Full information on the voting for its approval can be found in the report on voting indicated in
the above table.
The language used for the development of this Amendment is English.

© IEC 2023
This document was drafted in accordance with ISO/IEC Directives, Part 2, and developed in
accordance with ISO/IEC Directives, Part 1 and ISO/IEC Directives, IEC Supplement, available
at www.iec.ch/members_experts/refdocs. The main document types developed by IEC are
described in greater detail at www.iec.ch/publications/.
The committee has decided that the contents of this document will remain unchanged until the
stability date indicated on the IEC website under webstore.iec.ch in the data related to the
specific document. At this date, the document will be
• reconfirmed,
• withdrawn,
• replaced by a revised edition, or
• amended.
___________
3.1.11
no-load operating state
Add, to the end of the existing Note 1 to entry, added by IEC 62751-2/AMD1:2019, the following
sentence:
The integration time over which such losses are averaged might need to be longer than during normal operation, so
as to obtain the correct weighted average of the losses while blocked and the losses while switching.
4.2 Principles for loss determination
Replace, in the last sentence of the existing first paragraph, modified by
IEC 62751-2/AMD1:2019, the word "justify" with "explain".
Replace, in the last sentence of the existing third paragraph, modified by
IEC 62751-2/AMD1:2019, the text "is now under study in CIGRÉ WG B4-75" with "has been
studied by CIGRE WG B4-75 and is summarised in Annex C".
Delete the third sentence of the existing last paragraph, starting with "Care should also be
taken".
4.4 Loss calculation method
Delete, in the third sentence of the existing first paragraph, the words "for example valve
currents and switching energies".
Replace, in the last sentence of the existing second paragraph, the word "currents" with
"losses".
Delete, in the existing last paragraph, the words "and justified".
Add, to the end of the existing last paragraph, the following new sentence:
The main benefit of the numerical offline simulation is the determination of the average
distribution of the switching events across a cycle.

– 4 – IEC 62751-2:2014/AMD2:2023
© IEC 2023
Add, after the existing last paragraph, the following new paragraph:
The remaining calculations can be performed analytically with a reasonable accuracy. If it can
be shown by the manufacturer that the distribution of switching events is reasonably accurate,
then the remaining calculations shall be allowed to be performed analytically.
4.5.2 Input data for numerical simulations
Replace, in the existing dashed list, modified by IEC 62751-2/AMD1:2019, the first dashed item
with the following new item:
The simulation model shall include a control block which reproduces the correct valve current
and switching pattern used in the complete system.
Delete, in the fourth dash of the existing dashed list, modified by IEC 62751-2/AMD1:2019, the
words "parasitic elements".
Replace, in the fifth dash of the existing dashed list, modified by IEC 62751-2/AMD1:2019, the
text "with a reduced number of" with "using a lumped representation of the".
Delete the last two dashed items of the existing dashed list, modified by
IEC 62751-2/AMD1:2019.
Add, after the existing dashed list, modified by IEC 62751-2/AMD1:2019, the following new
paragraph and list:
There are two different approaches/methods which may be applied:
1) Two-stage simulation and calculation method on the basis of simulated input values
In this approach, the input parameters required for a calculation shall be simulated using a
model which at least represents the on-state characteristics of the converter as well as the
switching pattern or control pattern for the switching of the cells. The on-state representation
may be chosen on the basis of worst-case characteristics (at high junction temperatures) or
on-state characteristics for lower junction temperatures. The simulated values (voltages,
currents and switching pattern) shall be used as input for the calculations. For the
calculations with the simulated values, the following two approaches may be used.
a) The semiconductor parameters are chosen for the rated or worst-case junction
temperature condition and the losses shall be calculated on the basis of the rated
junction temperature.
NOTE Due to the assumption of a worst-case temperature condition, this calculation will result in higher
losses than what can actually be observed in the real application.
b) Using
...