IEC 61803:2020

Determination of power losses in high-voltage direct current (HVDC) converter stations with line-commutated converters

IEC 61803:2020 applies to all line-commutated high-voltage direct current (HVDC) converter stations used for power exchange (power transmission or back-to-back installation) in utility systems. This document presumes the use of 12-pulse thyristor converters but can, with due care, also be used for 6-pulse thyristor converters. In some applications, synchronous compensators or static var compensators (SVC) may be connected to the AC bus of the HVDC converter station. The loss determination procedures for such equipment are not included in this document. This document presents a set of standard procedures for determining the total losses of an HVDC converter station. The procedures cover all parts, except as noted above, and address no-load operation and operating losses together with their methods of calculation which use, wherever possible, measured parameters. Converter station designs employing novel components or circuit configurations compared to the typical design assumed in this document, or designs equipped with unusual auxiliary circuits that could affect the losses, are assessed on their own merits. This edition includes the following significant technical changes with respect to the previous edition:
- to facilitate the application of this document and to ensure its quality remains consistent, 5.1.8 and 5.8 have been reviewed, taking into consideration that the present thyristor production technology provides considerably less thyristor parameters dispersion comparing with the situation in 1999 when the first edition of IEC 61803 was developed, and therefore the production records of thyristors can be used for the power losses calculation;
- the calculation of the total station load losses (cases D1 and D2 in Annex C) has been corrected.

Détermination des pertes en puissance dans les postes de conversion en courant continu à haute tension (CCHT) munis de convertisseurs commutés par la ligne

L'IEC 61803:2020 s'applique à tous les postes de conversion en courant continu à haute tension (CCHT), commutés par la ligne, et utilisés pour l'échange de puissance (transmission de puissance ou installation dos à dos) dans des systèmes de distribution d'énergie. Le présent document présuppose l'utilisation de convertisseurs à thyristors à 12 impulsions mais peut également, en prenant les précautions appropriées, s'appliquer à des convertisseurs à thyristors à 6 impulsions. Dans certaines applications, il est admis de connecter des compensateurs synchrones ou des compensateurs var statiques (CVS) au nœud à courant alternatif du poste de conversion en courant continu à haute tension (CCHT). Les procédures de détermination de pertes pour ce type de matériel ne figurent pas dans le présent document. Le présent document décrit un ensemble de procédures types permettant de déterminer l'ensemble des pertes d'un poste de conversion à CCHT. Les procédures s’appliquent à toutes les pièces, à l'exception de celles susmentionnées, et considèrent les pertes en fonctionnement à vide et les pertes en fonctionnement ainsi que leurs méthodes de calcul utilisant, dans la mesure du possible, des paramètres mesurés. Les conceptions de poste de conversion utilisant des composants ou des configurations de circuit originaux par rapport à la conception type prise pour hypothèse dans le présent document, ou des conceptions équipées de circuits de distribution d'énergie auxiliaires inhabituels susceptibles de modifier les pertes, sont évaluées selon leurs propres mérites. Cette édition inclut les modifications techniques majeures suivantes par rapport à l'édition précédente:
- en vue de faciliter l’application de la norme sans en détériorer la qualité, 5.1.8 et 5.8 ont été revus en tenant compte du fait que la technologie de production de thyristors actuelle occasionne considérablement moins de dispersion dans ses paramètres par rapport à la situation de 1999, lorsque la première édition de l'IEC 61803 a été élaborée. Ainsi, les données enregistrées de production de thyristors peuvent être utilisées pour les calculs de pertes de puissance;
- le calcul des pertes de charge au poste totales (cas D1 et D2 à l’Annexe C) a été corrigé.

General Information

• Status: Published
• Publication Date: 18-Oct-2020
• ICS: 29.200 - Rectifiers. Convertors. Stabilized power supply
• Technical Committee: SC 22F - Power electronics for electrical transmission and distribution systems
• Drafting Committee: MT 14 - TC 22/SC 22F/MT 14
• Current Stage: PPUB - Publication issued
• Start Date: 19-Oct-2020
• Completion Date: 17-Nov-2020

Relations

• Revises: IEC 61803:1999 - Determination of power losses in high-voltage direct current (HVDC) converter stations
• Effective Date: 05-Sep-2023
• Revises: IEC 61803:1999/AMD1:2010 - Amendment 1 - Determination of power losses in high-voltage direct current (HVDC) converter stations with line-commutated converters
• Effective Date: 05-Sep-2023
• Revises: IEC 61803:1999/AMD2:2016 - Amendment 2 - Determination of power losses in high-voltage direct current (HVDC) converter stations with line commutated converters
• Effective Date: 05-Sep-2023
• Revises: IEC 61803:1999/COR1:1999 - Corrigendum 1 - Determination of power losses in high-voltage direct current (HVDC) converter stations
• Effective Date: 05-Sep-2023

Overview

IEC 61803:2020 - Determination of power losses in high-voltage direct current (HVDC) converter stations with line‑commutated converters - is an International Electrotechnical Commission standard that defines standardized procedures to quantify total power losses in line‑commutated HVDC converter stations. The document is written primarily for stations using 12‑pulse thyristor converters (and, with care, applicable to 6‑pulse converters). It covers both no‑load and operating losses, and recommends using measured parameters wherever possible.

This edition (2020) includes notable updates:

• Recognition that modern thyristor production has reduced parameter dispersion, allowing the use of thyristor production records for loss calculations (revisions to clauses 5.1.8 and 5.8).
• Corrections to the calculation of total station load losses (cases D1 and D2 in Annex C).

Key topics

• Scope and assumptions for line‑commutated HVDC converter stations (power transmission and back‑to‑back installations).
• Thyristor valve losses: conduction, spreading, turn‑off, damping and temperature effects.
• Converter transformer losses: no‑load and load losses, auxiliary power considerations.
• AC and DC filter losses: capacitor, reactor and resistor loss components.
• Shunt capacitor and reactor losses, DC smoothing reactor and other equipment loss categories.
• Auxiliaries and station service losses, and radio interference / PLC series filter losses.
• Harmonic calculations and methods (Annex A) and worked examples for loss evaluation (Annex C).
• Guidance on how to handle non‑typical designs or unusual auxiliary circuits (assessed case‑by‑case).

Applications

IEC 61803:2020 is practical for:

• HVDC design engineers and OEMs verifying converter station loss estimates.
• Utility planners and system operators performing loss studies, energy accounting and economic assessments.
• Testing and commissioning teams establishing contractual loss measurements and acceptance criteria.
• Consultants performing performance benchmarking, audits or life‑cycle cost analyses.
• Procurement/specification authors who need standardized loss calculation methods.

Practical benefits include consistent, repeatable loss evaluations, improved comparability between designs, and support for operational optimization and tariff/settlement calculations.

Related standards

• IEC 60076 series (Power transformers), including IEC 60076‑1 and IEC 60076‑6, referenced for transformer loss and testing procedures.
• Other IEC and industry standards on HVDC, power electronics and harmonic measurement are complementary when applying IEC 61803.

Keywords: IEC 61803, HVDC, power losses, line‑commutated converters, thyristor valves, 12‑pulse converter, loss determination, converter transformer, AC filter, DC smoothing reactor.

Standards Content (Sample)

IEC 61803 ®
Edition 2.0 2020-10
REDLINE VERSION
INTERNATIONAL
STANDARD
colour
inside
Determination of power losses in high-voltage direct current (HVDC) converter
stations with line-commutated converters

All rights reserved. Unless otherwise specified, no part of this publication may be reproduced or utilized in any form
or by any means, electronic or mechanical, including photocopying and microfilm, without permission in writing from
either IEC or IEC's member National Committee in the country of the requester. If you have any questions about IEC
copyright or have an enquiry about obtaining additional rights to this publication, please contact the address below or
your local IEC member National Committee for further information.

IEC Central Office Tel.: [phone]
3, rue de Varembé [e-mail]
CH-1211 Geneva 20 www.iec.ch
Switzerland
About the IEC
The International Electrotechnical Commission (IEC) is the leading global organization that prepares and publishes
International Standards for all electrical, electronic and related technologies.

About IEC publications
The technical content of IEC publications is kept under constant review by the IEC. Please make sure that you have the
latest edition, a corrigendum or an amendment might have been published.

IEC publications search - webstore.iec.ch/advsearchform Electropedia - www.electropedia.org
The advanced search enables to find IEC publications by a The world's leading online dictionary on electrotechnology,
variety of criteria (reference number, text, technical containing more than 22 000 terminological entries in English
committee,…). It also gives information on projects, replaced and French, with equivalent terms in 16 additional languages.
and withdrawn publications. Also known as the International Electrotechnical Vocabulary

(IEV) online.
IEC Just Published - webstore.iec.ch/justpublished

Stay up to date on all new IEC publications. Just Published IEC Glossary - std.iec.ch/glossary
details all new publications released. Available online and 67 000 electrotechnical terminology entries in English and
once a month by email. French extracted from the Terms and Definitions clause of
IEC publications issued since 2002. Some entries have been
IEC Customer Service Centre - webstore.iec.ch/csc collected from earlier publications of IEC TC 37, 77, 86 and
If you wish to give us your feedback on this publication or CISPR.

need further assistance, please contact the Customer Service

Centre: [e-mail].
IEC 61803 ®
Edition 2.0 2020-10
REDLINE VERSION
INTERNATIONAL
STANDARD
colour
inside
Determination of power losses in high-voltage direct current (HVDC) converter

stations with line-commutated converters

INTERNATIONAL
ELECTROTECHNICAL
COMMISSION
ICS 29.200 ISBN 978-2-8322-8970-9

– 2 – IEC 61803:2020 RLV © IEC 2020
CONTENTS
FOREWORD . 4
1 Scope . 6
2 Normative references . 6
3 Terms, definitions and symbols. 6
3.1 Terms and definitions . 7
3.2 Symbols . 8
4 Overview . 9
4.1 General . 9
4.2 Ambient conditions. 9
4.2.1 General . 9
4.2.2 Outdoor standard reference temperature . 9
4.2.3 Coolant standard reference temperature . 10
4.2.4 Standard reference air pressure . 10
4.3 Operating parameters . 10
5 Determination of equipment losses . 11
5.1 Thyristor valve losses . 11
5.1.1 General . 11
5.1.2 Thyristor conduction loss per valve . 11
5.1.3 Thyristor spreading loss per valve . 12
5.1.4 Other conduction losses per valve . 13
5.1.5 DC voltage-dependent loss per valve . 13
5.1.6 Damping loss per valve (resistor-dependent term) . 14
5.1.7 Damping loss per valve (change of capacitor energy term) . 15
5.1.8 Turn-off losses per valve . 15
5.1.9 Reactor loss per valve . 16
5.1.10 Total valve losses . 16
5.1.11 Temperature effects. 16
5.1.12 No-load operation loss per valve . 17
5.2 Converter transformer losses . 17
5.2.1 General . 17
5.2.2 No-load operation losses . 17
5.2.3 Operating losses. 17
5.2.4 Auxiliary power losses . 19
5.3 AC filter losses . 19
5.3.1 General . 19
5.3.2 AC filter capacitor losses . 19
5.3.3 AC filter reactor losses . 20
5.3.4 AC filter resistor losses . 20
5.3.5 Total AC filter losses . 20
5.4 Shunt capacitor bank losses . 20
5.5 Shunt reactor losses . 21
5.6 DC smoothing reactor losses . 21
5.7 DC filter losses . 22
5.7.1 General . 22
5.7.2 DC filter capacitor losses . 22
5.7.3 DC filter reactor losses . 22

5.7.4 DC filter resistor losses . 23
5.7.5 Total DC filter losses . 23
5.8 Auxiliaries and station service losses . 23
5.9 Radio interference/PLC Series filter losses . 24
5.10 Other equipment losses . 25
Annex A (normative informativee) Calculation of harmonic currents and voltages . 31
A.1 Harmonic currents in converter transformers . 31
A.2 Harmonic currents in the AC filters . 31
A.3 Harmonic voltages on the DC side . 32
A.4 DC side harmonic currents in the smoothing reactor . 32
Annex B (informative) Typical station losses . 33
Annex C (informative) HVDC converter station loss evaluation – An illustration . 34
C.1 General . 34
C.2 Loss evaluation under various cases . 35
Bibliography . 37

Figure 1 – Typical high-voltage direct current (HVDC) equipment for one pole (auxiliary
equipment is not shown) . 26
Figure 2 – Simplified three-phase diagram of an HVDC 12-pulse converter . 27
Figure 3 – Simplified equivalent circuit of a typical thyristor valve . 27
Figure 4 – Current and voltage waveforms of a valve operating in a 12-pulse converter
(commutation overshoots are not shown) . 28
Figure 5 – Thyristor on-state characteristic . 29
Figure 6 – Conduction current and voltage drop . 29
Figure 7 – Distribution of commutating inductance between L and L . 30
1 2
Figure 8 – Thyristor current during reverse recovery . 30

Table B.1 – Typical values of losses . 33
Table C.1 – Conditions for calculation of losses in case D1 . 36
Table C.2 – Conditions for calculation of losses in Case D2. . 36

– 4 – IEC 61803:2020 RLV © IEC 2020
INTERNATIONAL ELECTROTECHNICAL COMMISSION
____________
DETERMINATION OF POWER LOSSES IN HIGH-VOLTAGE
DIRECT CURRENT (HVDC) CONVERTER STATIONS WITH
LINE-COMMUTATED 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.
This redline version of the official IEC Standard allows the user to identify the changes
made to the previous edition. A vertical bar appears in the margin wherever a change
has been made. Additions are in green text, deletions are in strikethrough red text.

International Standard IEC 61803 has been prepared by subcommittee 22F: Power electronics
for electrical transmission and distribution systems, of IEC technical committee 22: Power
electronic systems and equipment.
This second edition cancels and replaces the first edition published in 1999,
Amendment 1:2010 and Amendment 2:2016. This edition constitutes a technical revision.
This edition includes the following significant technical changes with respect to the previous
edition:
a) to facilitate the application of this document and to ensure its quality remains consistent,
5.1.8 and 5.8 have been reviewed, taking into consideration that the present thyristor
production technology provides considerably less thyristor parameters dispersion
comparing with the situation in 1999 when the first edition of IEC 61803 was developed,
and therefore the production records of thyristors can be used for the power losses
calculation;
b) the calculation of the total station load losses (cases D1 and D2 in Annex C) has been
corrected.
The text of this International Standard is based on the following documents:
CDV Report on voting
22F/563/CDV 22F/580A/RVC
Full information on the voting for the approval of this International Standard can be found in
the report on voting indicated in the above table.
This document has been drafted in accordance with the ISO/IEC Directives, Part 2.
The committee has decided that the contents of this document will remain unchanged until the
stability date indicated on the IEC website under "http://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.
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.
– 6 – IEC 61803:2020 RLV © IEC 2020
DETERMINATION OF POWER LOSSES IN HIGH-VOLTAGE
DIRECT CURRENT (HVDC) CONVERTER STATIONS WITH
LINE-COMMUTATED CONVERTERS
1 Scope
This document applies to all line-commutated high-voltage direct current (HVDC) converter
stations used for power exchange (power transmission or back-to-back installation) in utility
systems. This document presumes the use of 12-pulse thyristor converters but can, with due
care, also be used for 6-pulse thyristor converters.
In some applications, synchronous compensators or static var compensators (SVC) may be
connected to the AC bus of the HVDC converter station. The loss determination procedures
for such equipment are not included in this document.
This document presents a set of standard procedures for determining the total losses of an
HVDC converter station. Typical HVDC equipment is shown in figure 1. The procedures cover
all parts, except as noted above, and address no-load operation and operating losses
together with their methods of calculation which use, wherever possible, measured
parameters.
Converter station designs employing novel components or circuit configurations compared to
the typical design assumed in this document, or designs equipped with unusual auxiliary
circuits that could affect the losses, shall be are assessed on their own merits.
2 Normative references
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.
IEC 60076-1:1993, Power transformers – Part 1: General
IEC 60076-6, Power transformers – Part 6: Reactors
IEC 60289:1988, Reactors
IEC 60633:1998, Terminology for high-voltage direct current (HVDC) transmission
IEC 60633, High-voltage direct current (HVDC) transmission – Vocabulary
IEC 60700-1:19982015, Thyristor valves for high voltage direct current (HVDC) power
transmission – Part 1: Electrical testing
IEC 60747-6:1983, Semiconductor devices – Discrete devices – Part 6: Thyristors
IEC 60871-1:1997, Shunt capacitors for a.c. power systems having a rated voltage above
1 000 V – Part 1: General performance, testing and rating – Safety requirements – Guide for
installation and operation
3 Terms, definitions and symbols
For the purpose of this International Standard, the following definitions apply:
For the purposes of this document, the terms and definition given in IEC 60633 and the
following apply.
ISO and IEC maintain terminological databases for use in standardization at the following
addresses:
• IEC Electropedia: available at http://www.electropedia.org/
• ISO Online browsing platform: available at http://www.iso.org/obp
3.1 Terms and definitions
3.1.1
auxiliary losses
electric power required to feed the converter station auxiliary loads
Note 1 to entry: The auxiliary losses depend on the number of converter units used and whether the station is in
no-load operation or carrying load, in which case the auxiliary losses depend on the load level.
3.1.2
equipment no-load operation losses
losses produced in an item of equipment with the converter station energised but with the
converters blocked and all station service loads and auxiliary equipment connected as
required for immediate pick-up of load to specified minimum power
3.1.3
load level
direct current, direct voltage, firing angle, AC voltage, and converter transformer tap-changer
position at which the converter station is operating
3.1.4
equipment operating losses
losses produced in an item of equipment at a given load level with the converter station
energised and the converters operating
3.1.5
rated load
load related to operation at nominal values of DC current, DC voltage, AC voltage and
converter firing angle
Note 1 to entry: The AC system shall be assumed to be at nominal frequency, and its 3-phase voltages are
nominal and balanced. The position of the tap-changer of the converter transformer and the number of AC filters
and shunt reactive elements connected shall be consistent with operation at rated load, coincident with nominal
conditions.
3.1.6
total station no-load operation losses
the total station loss is the sum of all operating or no-load operation losses and the
corresponding auxiliary losses
sum of all equipment no-load operation losses (3.1.2) and corresponding auxiliary losses
(3.1.1)
3.1.7
total station operating losses
sum of all equipment operating losses (3.1.4) and corresponding auxiliary losses (3.1.1) at a
particular load level
– 8 – IEC 61803:2020 RLV © IEC 2020
Note 1 to entry: An illustrative example using total station operating losses and corresponding loss evaluation is
given in Annex C, case D1.
3.1.8
total station load losses
difference between total station operating losses (3.1.7) and total station no-load operation
losses (3.1.6)
Note 1 to entry: Such calculated total station load losses are considered as being quantitatively equivalent to load
losses as in conventional AC substation practice.
Note 2 to entry: It is recognized that some purchasers evaluate total station no-load operation losses (3.1.6) and
total station load losses individually instead of the evaluating total station operating losses (3.1.7).
Note 3 to entry: An illustrative example to derive load losses, equivalent load losses and corresponding loss
evaluation is given in Annex C, case D2.
3.1.9
station essential auxiliary load
load whose failure will affect the conversion capability of the HVDC converter station (e.g.
valve cooling), as well as load that shall remain working in case of complete loss of AC power
supply (e.g. battery chargers, operating mechanisms)
3.2 Symbols
(trigger/firing) delay angle, in radians (rad)
α
commutation overlap angle, in radians (rad)
µ
f AC system frequency, in hertz (Hz)
I direct current in the bridge d.c. connection, in amperes (A)
d
I harmonic RMS current of order n, in amperes (A)
n
L inductance, in henrys (H), referred to the valve winding, between the commutating
voltage source and the point of common coupling between star- and delta-connected
windings. L shall include any external inductance between the transformer line-
winding terminals and the point of connection of the AC harmonic filters.
L inductance, in henrys (H), referred to the valve winding, between the point of
common coupling between star- and delta-connected windings, and the valve. L
shall include the saturated inductance of the valve reactors.
m
electromagnetic notch coupling factor, m = L /(L + L )
1 1 2
n harmonic order
N number of series-connected thyristors per valve
t
P power loss in an item of equipment, in watts (W)
Q
quality factor at harmonic order n
n
R
resistance value, in ohms (W) (Ω)
U direct voltage, in volts (V)
d
U
harmonic RMS voltage of order n, in volts (V)
n
U RMS value of the phase-to-phase no-load voltage on the valve side of the converter
vo
transformer excluding harmonics, in volts (V)
X
inductive reactance at harmonic order n, in ohms (Ω)
n
4 Overview
4.1 General
4.1 Introduction
Suppliers need to know in detail how and where losses are generated, since this affects
component and equipment ratings. Purchasers are interested in a verifiable loss figure which
allows equitable bid comparison and in a procedure after delivery which can objectively verify
the guaranteed performance requirements of the supplier.
As a general principle, it would be desirable to determine the efficiency of an HVDC converter
station by a direct measurement of its energy losses. However, attempts to determine the
station losses by subtracting the measured output power from the measured input power
should recognize that such measurements have an inherent inaccuracy, especially if
performed at high voltage. The losses of an HVDC converter station at full load are generally
less than 1 % of the transmitted power. Therefore, the loss measured as a small difference
between two large quantities is not likely to be a sufficiently accurate indication of the actual
losses.
In some special circumstances, it may be possible, for example, to arrange a temporary test
connection in which two converters are operated from the same AC source and also
connected together via their DC terminals. In this connection, the power drawn from the AC
source equals the losses in the circuit. However, the AC source must shall also provide var
support and commutating voltage to the two converters. Once again, there are practical
measurement difficulties.
In order to avoid the problems described above, this document standardizes a method of
calculating the HVDC converter station losses by summing the losses calculated for each item
of equipment. The standardized calculation method will help the purchaser to meaningfully
compare the competing bids. It will also allow an easy generation of performance curves for
the wide range of operating conditions in which the performance has to be known. In the
absence of an inexpensive experimental method which could be employed for an objective
verification of losses during type tests, the calculation method is the next best alternative as it
uses, wherever possible, experimental data obtained from measurements on individual
equipment and components under conditions equivalent to those encountered in real
operation.
The calculation of harmonic currents and voltages in HVDC equipment is described in
Annex A.
It is important to note that the power loss in each item of equipment will depend on the
ambient conditions under which it operates, as well as on the operating conditions or duty
cycles to which it is subjected. Therefore, the ambient and operating conditions shall be
defined for each item of equipment, based on the ambient and operating conditions of the
entire HVDC converter station.
4.2 Ambient conditions
4.2.1 General
A set of standard reference ambient conditions shall be used for determining the power losses
in HVDC converter stations.
4.2.2 Outdoor standard reference temperature
An outdoor ambient dry bulb temperature of 20 °C shall be used as the standard reference
temperature for determining the total converter station losses. Corresponding valve hall
temperature may be defined by the supplier if necessary. The equivalent wet-bulb
temperature (where necessary) shall be defined by the purchaser.

– 10 – IEC 61803:2020 RLV © IEC 2020
If not defined, the wet-bulb temperature is recommended to be 14 °C, which corresponds to
approximately 50 % RH at 20 °C dry bulb temperature.
4.2.3 Coolant standard reference temperature
Where forced cooling is used for equipment, the flow rate and temperature of the coolant can
influence the temperature rise and associated losses of that equipment. Therefore, the
coolant temperatures and flow rates established by the purchaser and the supplier shall be
used as a basis for determining the losses.
4.2.4 Standard reference air pressure
The reference air pressure to be used for the evaluation of total converter station power
losses shall be the standard atmospheric pressure (101,3 kPa) corrected to the altitude of the
installation in question.
4.3 Operating parameters
The losses of an HVDC converter station depend on its operating parameters.
The losses of HVDC converter stations are classified into three categories, termed the no-
load operation losses, operating losses and auxiliary losses.
The losses of HVDC converter stations are classified into two categories, referred to as
operating losses (3.1.4 and 3.1.7) and no-load operation losses (3.1.2 and 3.1.6).
The operating losses and auxiliary losses are affected by the load level of the station because
the numbers of certain types of energised equipment (for example harmonic filters and cooling
equipment) may depend upon the load level and because losses in individual items of
equipment themselves vary with the load level.
HVDC converter station losses shall be determined for nominal (balanced) AC system voltage
and frequency, symmetrical impedances of the converter transformer and symmetrical firing
angles. The transformer tap-changer shall be assumed to be in the position corresponding to
nominal AC system voltage or as decided by the control system for the defined operating
condition.
The operating losses shall be determined for the load levels specified by the purchaser, or at
rated load if no such conditions are specified. For each load level, the valve-winding AC
voltage, DC current, converter firing angle, shunt compensation and harmonic filtering
equipment shall be consistent with the respective load level and other specified performance
requirements, relating, for example, to harmonic distortion and reactive power. Cooling and
other auxiliary equipment, as appropriate to the standard reference temperature (see 4.2.2
and 4.2.3), shall be assumed to be connected to support the respective load level.
For the no-load operation mode, converter transformers shall be energised and the converters
blocked. All filters and reactive power compensation equipment shall be assumed to be
disconnected except for those which are required to sustain operation at zero load in order,
for example, to meet the specified reactive power requirements. Station service loads and
auxiliary equipment (e.g. cooling-water pumps) shall be assumed to be connected as required
for immediate pick-up of load for the converter station (without waiting for tap changer
movement) to specified minimum power.

5 Determination of equipment losses
5.1 Thyristor valve losses
5.1.1 General
The loss production mechanisms applicable when the valves are blocked (no-load operation
losses) are different from those applicable in normal operation (operating losses). Operating
losses are dealt with in 5.1.2 to 5.1.11, and no-load operation losses are dealt with in 5.1.12.
Auxiliary losses are dealt with in 5.8.
Typical high-voltage direct current (HVDC) equipment for one pole of a HVDC substation is
shown in Figure 1.
A simplified three-phase diagram of an HVDC 12-pulse converter is shown in Figure 2.
Individual valves are marked in the order of their conduction sequence.
A simplified equivalent circuit of a typical valve is shown in Figure 3. Symbol t "th" combines
together the effects of N thyristors connected in series in the valve. C and R are the
t AC AC
corresponding combined values of R-C damping circuits used for voltage sharing and
overvoltage suppression. R represents DC grading resistors and other resistive
DC
components which incur loss when the valve blocks voltage. It also includes the effects of the
thyristor leakage current (see 5.1.5 and 5.1.12). C includes both stray capacitances and
s
surge distribution capacitors (if used). L represents saturable reactors used to limit the di/dt
s
stresses to safe values and to improve the distribution of fast rising voltages. R represents
s
the resistances of the current conducting components of the valve such as the busbars,
contact resistances, resistance of the windings of the saturable reactors, etc. Power losses in
the valve surge arrester (not shown) shall be neglected.
Figure 4 shows, as an example, current and voltage waveforms of valve 1 (according to Figure 2)
operating in rectifier – Figure 4 a) – and inverter – Figure 4 b) – modes. In the example
shown, the firing instants of the valves of the upper bridge are delayed by 30° with respect to
the valves of the lower bridge due to the phase shift between the two secondaries. For each
valve, the length of the conduction intervals is 130° (2π/3 + μ). During commutations, the
valve current is assumed, for this document, to be changing linearly whereas in reality the
valve currents follow portions of sine waves. This simplification has negligible effect on the
resulting losses, while the trapezoidal waveform significantly simplifies the calculations. The
voltage blocked by the valve shows notches caused by commutations between individual
valves.
5.1.2 Thyristor conduction loss per valve
A typical thyristor on-state characteristic is shown in Figure 5. This Thyristor conduction loss
component is the product of the conduction current i(t) – Figure 6 a) – and the corresponding
ideal on-state voltage as shown in Figure 5 and 6. Formula P shall be used provided that
V1a
the DC bridge current is well smoothed. In the event that the root sum square value of the DC
side harmonic currents, determined in accordance with Clause A.4 (annex A), exceeds 5 % of
the DC component, formula P shall be used instead.
V1b
– 12 – IEC 61803:2020 RLV © IEC 2020
NI×
 2π− µ 

td
P U+ RI××
V1a 0 0 d 

32π


n=48

N ××I U N × R 2π − µ

td 0 t 0 22

P= ++II
V1b d n
∑ 

33 2π

n=12

where
U is the current-independent component of the on-state voltage of the average thyristor
(see note below), in volts;
R is the slope resistance of the on-state characteristic of the average thyristor (see note
below), in ohms;
th
I is the calculated RMS value of the n harmonic current in the bridge DC connection
n
according to Clause A.4, in amperes.
NOTE U and R (see Figure 5) are determined from the fully spread on-state voltage measured at the
0 0
appropriate current and junction temperature. The average value of U and R is obtained from production records
0 0
of the thyristors manufactured for the specific project at 100 % and 50 % of nominal d.c. current. The temperature
dependence of U and R is established from type tests or routine tests on a statistically significant number of the
0 0
thyristors employed, and is used, where necessary, to correct U and R to the appropriate service junction
0 0
temperature. If parallel connection of p thyristors is employed, the appropriate 100 % current is the nominal DC
bridge current divided by p. The calculated result is then multiplied by p.
5.1.3 Thyristor spreading loss per valve
This loss component is an additional conduction loss of the thyristors arising from the delay in
establishing full conduction of the silicon after the thyristor has been turned on. The additional
loss is the product of the current and the voltage by which the thyristor voltage exceeds the
ideal thyristor on-state voltage drop – see the hatched area in Figure 6 b).
t1
P = N××f u t− u t ×i t dt
( ) ( ) ( )
V2 t B A
∫ 
where
t is the length of the conduction interval, in seconds, which is given by:
π + µ
t = ;
2πf
u (t) is the instantaneous on-state voltage, in volts, of a thyristor whose fully spread on-
B
state voltage is typical for the thyristors used; the instantaneous on-state voltage shall
be determined for the appropriate junction temperature measured with a trapezoidal
current pulse exhibiting the correct amplitude and commutation overlap periods (see
Figure 5 and Figure 6);
u (t) is the calculated instantaneous on-state voltage of the average thyristor at the same
A
junction temperature for the same current pulse but with the conducting area fully
established throughout the conduction, as derived from its on-state characteristic
represented by U and R only (see Figure 6);
0 0
i(t) is the instantaneous current in the thyristor, in amperes.
NOTE – Instantaneous on-state voltage data, including the effects of spreading, are usually not
available from production records. Measurements of typical thyristor on-state voltage,
including spreading, should therefore be obtained during the valve periodic firing and
=
extinction type test (IEC 60700-1:2015, Clause 9) or, alternatively, from a separate laboratory
test on a statistically significant number of thyristors.
5.1.4 Other conduction losses per valve
These are the conduction losses in the main circuit of the valve due to components other than
the thyristors.
R ⋅ I
2π − µ
sd
P =
V3 
32π

where
is the DC resistance of the valve terminal-to-terminal circuit excluding the thyristors, in
R
s
ohms (see Figure 3).
The value of R is determined by direct measurement on a representative valve section that
s
includes all elements of the main circuit of a valve in the correct proportions, but in which the
thyristors have been replaced by copper blocks of the appropriate dimensions and with
contacts treated in the same way as for real thyristors. Alternatively, the resistance may be
calculated, in which case the calculation methods shall be documented.
5.1.5 DC voltage-dependent loss per valve
This loss component is the loss in the shunt resistance R of the valve (see Figure 3),
DC
arising from the voltage which appears between valve terminals during the non-conducting
interval (see Figure 4). It includes losses due to thyristor off-state and reverse leakage, losses
in DC grading resistors, other resistive circuits and elements connected in parallel with the
thyristors, resistance of the coolant in coolant pipes, resistivity effects of the structure, fibre
optics, etc.
2 2

U
4 3 6mm−−12 7
v0
P π+ cos 2α+cos 2αµ+2 + sin 2α−sin 2αµ+2+2µ
( ) ( ) ( ) ( )

v4
   
2  π R 3 4 8
DC


where
R is the effective off-state DC resistance of a complete valve determined by measuring
DC
the current drawn during the valve terminal-to-terminal DC voltage type test (according
to IEC 60700-1:2015, 8.3.1) in ohms; if a type test is not performed on the thyristor
valve, R shall be determined by reference to a previous type test (see also note 2
DC
the paragraph after Note 1 below);
m = L /(L + L );
1 1 2
L is the inductance, in henrys, referred to the valve winding, between the commutating
voltage source and the point of common coupling between star- and delta-connected
windings; L shall include any external inductance between the transformer line-
winding terminals and the point of connection of the AC harmonic filters (see Figure 7);
L is the inductance, in henrys, referred to the valve winding, between the point of
common coupling between star- and delta-connected windings, and the valve; L shall
include the saturated inductance of the valve reactors (see Figure 7).
The value of L shall be the same for both secondaries (L L = L ) (see notes 3 and 4
2d
2 2Δ 2Y
Note 2 and last paragraph below).
NOTE 1 The formula for P is valid for µ < π/6 (30°) only.
V4
NOTE 2 – Since the thyristor resistive leakage current is usually much higher at operating
temperatures than at the prevailing ambient air temperature, it is either necessary to heat the
=
– 14 – IEC 61803:2020 RLV © IEC 2020
thyristors of the valve to the correct operating temperature before the measurement of R is
DC
taken or to make later corrections to the measured value using the average thyristor data
obtained separately, to include the mentioned temperature effect (see also 5.1.11). The same
pertains to the liquid coolant.
NOTE 3 – 2 The value of m quantifies the effects of inductive coupling between the two secondaries of the
converter transformer. It determines the magnitude of the notches caused by the commutation in the other bridge
(notches from 1' to 3' and from 4' to 6' in Figure 4). If m = 0, then there is no coupling between the two bridges and
the notches from 1' to 3' and from 4' to 6' disappear altogether. The notches in Figure 4 correspond to m = 0,2.
NOTE 4 – Values of L and L are obtained from the short-circuit impedance measurements on
1 2
the converter transformers, and by adding any external inductances as required. The value of
L includes any external common inductance (such as power line carrier filters) between the
point of common coupling and the commutation voltage source. In cases where no AC
harmonic filters are connected, L also includes the AC system impedance. When separate
transformers supply the star and delta bridges and no additional line-side inductance is
included, L = 0, hence m = 0. When a three-winding transformer construction is employed, a
common winding impedance and mutual coupling effects of the two secondary windings give
non-zero values for L , which may be either positive or negative. For more complicated
transformer arrangements, such as filters connected to a tertiary winding, the values of L and
L must shall be determined with care.
5.1.6 Damping loss per valve (resistor-dependent term)
This loss component depends on the value of the resistive elements of those circuits that are
AC coupled via series capacitors and on the voltage appearing between valve terminals
during the non-conduction interval.


4π 3 3 3 m μ 7 9mm39
− + + 6mm−12 − 7 ++ − sin2α +

( )

3 2 8 4 8 4 32

  
22 2
P 2πfU C R

V5 v0 AC AC
  
7 3mm3 3 m 33 m 3 m
 + + sin 2α + 2μ − + cos2α + cos 2α + 2μ
( ) ( )

  
8 4 32 16 8 16
  

where
C is the effective terminal-to-terminal value of valve damping capacitance, in farads (see
AC
Figure 3);
R is the effective terminal-to-terminal value of the associated series-connected damping
AC
resistance, in ohms (see Figure 3);
C shall be the design value of damping capacitance per level divided by the number of
AC
thyristor levels in a valve;
R shall be the design value of damping resistor per level multiplied by the number of
AC
thyristor levels in a valve.
If the valve employs more than one damping or grading network that incorporates series-
connected R-C branches, then each branch shall be evaluated separately and the results
summed.
If energy is extracted from the R-C grading network to energise the thyristor firing and/or
monitoring circuits, then either it shall be demonstrated that the additional losses are
negligible or the additional loss shall be calculated separately and added to the figure
obtained from the formula P .
V5
NOTE Notes 1, 3 and 4 in 5.1.4 1 and 2 and the last paragraph of 5.1.5 also apply to P .
V5
=
----------
...

IEC 61803 ®
Edition 2.0 2020-10
INTERNATIONAL
STANDARD
NORME
INTERNATIONALE
Determination of power losses in high-voltage direct current (HVDC) converter
stations with line-commutated converters

Détermination des pertes en puissance dans les postes de conversion
en courant continu à haute tension (CCHT) munis de convertisseurs commutés
par la ligne
All rights reserved. Unless otherwise specified, no part of this publication may be reproduced or utilized in any form
or by any means, electronic or mechanical, including photocopying and microfilm, without permission in writing from
either IEC or IEC's member National Committee in the country of the requester. If you have any questions about IEC
copyright or have an enquiry about obtaining additional rights to this publication, please contact the address below or
your local IEC member National Committee for further information.

Droits de reproduction réservés. Sauf indication contraire, aucune partie de cette publication ne peut être reproduite
ni utilisée sous quelque forme que ce soit et par aucun procédé, électronique ou mécanique, y compris la photocopie
et les microfilms, sans l'accord écrit de l'IEC ou du Comité national de l'IEC du pays du demandeur. Si vous avez des
questions sur le copyright de l'IEC ou si vous désirez obtenir des droits supplémentaires sur cette publication, utilisez
les coordonnées ci-après ou contactez le Comité national de l'IEC de votre pays de résidence.

IEC Central Office Tel.: [phone]
3, rue de Varembé [e-mail]
CH-1211 Geneva 20 www.iec.ch
Switzerland
About the IEC
The International Electrotechnical Commission (IEC) is the leading global organization that prepares and publishes
International Standards for all electrical, electronic and related technologies.

About IEC publications
The technical content of IEC publications is kept under constant review by the IEC. Please make sure that you have the
latest edition, a corrigendum or an amendment might have been published.

IEC publications search - webstore.iec.ch/advsearchform Electropedia - www.electropedia.org
The advanced search enables to find IEC publications by a The world's leading online dictionary on electrotechnology,
variety of criteria (reference number, text, technical containing more than 22 000 terminological entries in English
committee,…). It also gives information on projects, replaced and French, with equivalent terms in 16 additional languages.
and withdrawn publications. Also known as the International Electrotechnical Vocabulary

(IEV) online.
IEC Just Published - webstore.iec.ch/justpublished
Stay up to date on all new IEC publications. Just Published IEC Glossary - std.iec.ch/glossary
details all new publications released. Available online and 67 000 electrotechnical terminology entries in English and
once a month by email. French extracted from the Terms and Definitions clause of
IEC publications issued since 2002. Some entries have been
IEC Customer Service Centre - webstore.iec.ch/csc collected from earlier publications of IEC TC 37, 77, 86 and
If you wish to give us your feedback on this publication or CISPR.

need further assistance, please contact the Customer Service

Centre: [e-mail].
A propos de l'IEC
La Commission Electrotechnique Internationale (IEC) est la première organisation mondiale qui élabore et publie des
Normes internationales pour tout ce qui a trait à l'électricité, à l'électronique et aux technologies apparentées.

A propos des publications IEC
Le contenu technique des publications IEC est constamment revu. Veuillez vous assurer que vous possédez l’édition la
plus récente, un corrigendum ou amendement peut avoir été publié.

Recherche de publications IEC - Electropedia - www.electropedia.org
webstore.iec.ch/advsearchform Le premier dictionnaire d'électrotechnologie en ligne au
La recherche avancée permet de trouver des publications IEC monde, avec plus de 22 000 articles terminologiques en
en utilisant différents critères (numéro de référence, texte, anglais et en français, ainsi que les termes équivalents dans
comité d’études,…). Elle donne aussi des informations sur les 16 langues additionnelles. Egalement appelé Vocabulaire
projets et les publications remplacées ou retirées. Electrotechnique International (IEV) en ligne.

IEC Just Published - webstore.iec.ch/justpublished Glossaire IEC - std.iec.ch/glossary
Restez informé sur les nouvelles publications IEC. Just 67 000 entrées terminologiques électrotechniques, en anglais
Published détaille les nouvelles publications parues. et en français, extraites des articles Termes et Définitions des
Disponible en ligne et une fois par mois par email. publications IEC parues depuis 2002. Plus certaines entrées
antérieures extraites des publications des CE 37, 77, 86 et
Service Clients - webstore.iec.ch/csc CISPR de l'IEC.

Si vous désirez nous donner des commentaires sur cette
publication ou si vous avez des questions contactez-nous:
[e-mail].
IEC 61803 ®
Edition 2.0 2020-10
INTERNATIONAL
STANDARD
NORME
INTERNATIONALE
Determination of power losses in high-voltage direct current (HVDC) converter

stations with line-commutated converters

Détermination des pertes en puissance dans les postes de conversion

en courant continu à haute tension (CCHT) munis de convertisseurs commutés

par la ligne
INTERNATIONAL
ELECTROTECHNICAL
COMMISSION
COMMISSION
ELECTROTECHNIQUE
INTERNATIONALE
ICS 29.200 ISBN 978-2-8322-8948-8

– 2 – IEC 61803:2020 © IEC 2020
CONTENTS
FOREWORD . 4
1 Scope . 6
2 Normative references . 6
3 Terms, definitions and symbols. 6
3.1 Terms and definitions . 7
3.2 Symbols . 8
4 Overview . 8
4.1 General . 8
4.2 Ambient conditions. 9
4.2.1 General . 9
4.2.2 Outdoor standard reference temperature . 9
4.2.3 Coolant standard reference temperature . 9
4.2.4 Standard reference air pressure . 10
4.3 Operating parameters . 10
5 Determination of equipment losses . 10
5.1 Thyristor valve losses . 10
5.1.1 General . 10
5.1.2 Thyristor conduction loss per valve . 11
5.1.3 Thyristor spreading loss per valve . 12
5.1.4 Other conduction losses per valve . 12
5.1.5 DC voltage-dependent loss per valve . 13
5.1.6 Damping loss per valve (resistor-dependent term) . 14
5.1.7 Damping loss per valve (change of capacitor energy term) . 14
5.1.8 Turn-off losses per valve . 15
5.1.9 Reactor loss per valve . 15
5.1.10 Total valve losses . 16
5.1.11 Temperature effects. 16
5.1.12 No-load operation loss per valve . 16
5.2 Converter transformer losses . 17
5.2.1 General . 17
5.2.2 No-load operation losses . 17
5.2.3 Operating losses. 17
5.2.4 Auxiliary power losses . 18
5.3 AC filter losses . 19
5.3.1 General . 19
5.3.2 AC filter capacitor losses . 19
5.3.3 AC filter reactor losses . 19
5.3.4 AC filter resistor losses . 20
5.3.5 Total AC filter losses . 20
5.4 Shunt capacitor bank losses . 20
5.5 Shunt reactor losses . 20
5.6 DC smoothing reactor losses . 21
5.7 DC filter losses . 21
5.7.1 General . 21
5.7.2 DC filter capacitor losses . 22
5.7.3 DC filter reactor losses . 22

5.7.4 DC filter resistor losses . 23
5.7.5 Total DC filter losses . 23
5.8 Auxiliaries and station service losses . 23
5.9 Series filter losses . 24
5.10 Other equipment losses . 25
Annex A (informative) Calculation of harmonic currents and voltages . 31
A.1 Harmonic currents in converter transformers . 31
A.2 Harmonic currents in the AC filters . 31
A.3 Harmonic voltages on the DC side . 32
A.4 DC side harmonic currents in the smoothing reactor . 32
Annex B (informative) Typical station losses . 33
Annex C (informative) HVDC converter station loss evaluation – An illustration . 34
C.1 General . 34
C.2 Loss evaluation under various cases . 35
Bibliography . 37

Figure 1 – Typical high-voltage direct current (HVDC) equipment for one pole . 26
Figure 2 – Simplified three-phase diagram of an HVDC 12-pulse converter . 27
Figure 3 – Simplified equivalent circuit of a typical thyristor valve . 27
Figure 4 – Current and voltage waveforms of a valve operating in a 12-pulse converter . 28
Figure 5 – Thyristor on-state characteristic . 29
Figure 6 – Conduction current and voltage drop . 29
Figure 7 – Distribution of commutating inductance between L and L . 30
1 2
Figure 8 – Thyristor current during reverse recovery . 30

Table B.1 – Typical values of losses . 33
Table C.1 – Conditions for calculation of losses in case D1 . 36
Table C.2 – Conditions for calculation of losses in Case D2. . 36

– 4 – IEC 61803:2020 © IEC 2020
INTERNATIONAL ELECTROTECHNICAL COMMISSION
____________
DETERMINATION OF POWER LOSSES IN HIGH-VOLTAGE
DIRECT CURRENT (HVDC) CONVERTER STATIONS WITH
LINE-COMMUTATED 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 61803 has been prepared by subcommittee 22F: Power electronics
for electrical transmission and distribution systems, of IEC technical committee 22: Power
electronic systems and equipment.
This second edition cancels and replaces the first edition published in 1999,
Amendment 1:2010 and Amendment 2:2016. This edition constitutes a technical revision.
This edition includes the following significant technical changes with respect to the previous
edition:
a) to facilitate the application of this document and to ensure its quality remains consistent,
5.1.8 and 5.8 have been reviewed, taking into consideration that the present thyristor
production technology provides considerably less thyristor parameters dispersion
comparing with the situation in 1999 when the first edition of IEC 61803 was developed,
and therefore the production records of thyristors can be used for the power losses
calculation;
b) the calculation of the total station load losses (cases D1 and D2 in Annex C) has been
corrected.
The text of this International Standard is based on the following documents:
CDV Report on voting
22F/563/CDV 22F/580A/RVC
Full information on the voting for the approval of this International Standard can be found in
the report on voting indicated in the above table.
This document has been drafted in accordance with the ISO/IEC Directives, Part 2.
The committee has decided that the contents of this document will remain unchanged until the
stability date indicated on the IEC website under "http://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.
– 6 – IEC 61803:2020 © IEC 2020
DETERMINATION OF POWER LOSSES IN HIGH-VOLTAGE
DIRECT CURRENT (HVDC) CONVERTER STATIONS WITH
LINE-COMMUTATED CONVERTERS
1 Scope
This document applies to all line-commutated high-voltage direct current (HVDC) converter
stations used for power exchange (power transmission or back-to-back installation) in utility
systems. This document presumes the use of 12-pulse thyristor converters but can, with due
care, also be used for 6-pulse thyristor converters.
In some applications, synchronous compensators or static var compensators (SVC) may be
connected to the AC bus of the HVDC converter station. The loss determination procedures
for such equipment are not included in this document.
This document presents a set of standard procedures for determining the total losses of an
HVDC converter station. The procedures cover all parts, except as noted above, and address
no-load operation and operating losses together with their methods of calculation which use,
wherever possible, measured parameters.
Converter station designs employing novel components or circuit configurations compared to
the typical design assumed in this document, or designs equipped with unusual auxiliary
circuits that could affect the losses, are assessed on their own merits.
2 Normative references
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.
IEC 60076-1, Power transformers – Part 1: General
IEC 60076-6, Power transformers – Part 6: Reactors
IEC 60633, High-voltage direct current (HVDC) transmission – Vocabulary
IEC 60700-1:2015, Thyristor valves for high voltage direct current (HVDC) power transmission
– Part 1: Electrical testing
IEC 60871-1, Shunt capacitors for a.c. power systems having a rated voltage above 1 000 V –
Part 1: General
3 Terms, definitions and symbols
For the purposes of this document, the terms and definition given in IEC 60633 and the
following apply.
ISO and IEC maintain terminological databases for use in standardization at the following
addresses:
• IEC Electropedia: available at http://www.electropedia.org/
• ISO Online browsing platform: available at http://www.iso.org/obp
3.1 Terms and definitions
3.1.1
auxiliary losses
electric power required to feed the converter station auxiliary loads
Note 1 to entry: The auxiliary losses depend on the number of converter units used and whether the station is in
no-load operation or carrying load, in which case the auxiliary losses depend on the load level.
3.1.2
equipment no-load operation losses
losses produced in an item of equipment with the converter station energised but with the
converters blocked and all station service loads and auxiliary equipment connected as
required for immediate pick-up of load to specified minimum power
3.1.3
load level
direct current, direct voltage, firing angle, AC voltage, and converter transformer tap-changer
position at which the converter station is operating
3.1.4
equipment operating losses
losses produced in an item of equipment at a given load level with the converter station
energised and the converters operating
3.1.5
rated load
load related to operation at nominal values of DC current, DC voltage, AC voltage and
converter firing angle
Note 1 to entry: The AC system shall be assumed to be at nominal frequency, and its 3-phase voltages are
nominal and balanced. The position of the tap-changer of the converter transformer and the number of AC filters
and shunt reactive elements connected shall be consistent with operation at rated load, coincident with nominal
conditions.
3.1.6
total station no-load operation losses
sum of all equipment no-load operation losses (3.1.2) and corresponding auxiliary losses
(3.1.1)
3.1.7
total station operating losses
sum of all equipment operating losses (3.1.4) and corresponding auxiliary losses (3.1.1) at a
particular load level
Note 1 to entry: An illustrative example using total station operating losses and corresponding loss evaluation is
given in Annex C, case D1.
3.1.8
total station load losses
difference between total station operating losses (3.1.7) and total station no-load operation
losses (3.1.6)
Note 1 to entry: Such calculated total station load losses are considered as being quantitatively equivalent to load
losses as in conventional AC substation practice.

– 8 – IEC 61803:2020 © IEC 2020
Note 2 to entry: It is recognized that some purchasers evaluate total station no-load operation losses (3.1.6) and
total station load losses individually instead of the evaluating total station operating losses (3.1.7).
Note 3 to entry: An illustrative example to derive load losses, equivalent load losses and corresponding loss
evaluation is given in Annex C, case D2.
3.1.9
station essential auxiliary load
load whose failure will affect the conversion capability of the HVDC converter station (e.g.
valve cooling), as well as load that shall remain working in case of complete loss of AC power
supply (e.g. battery chargers, operating mechanisms)
3.2 Symbols
α (trigger/firing) delay angle, in radians (rad)
overlap angle, in radians (rad)
µ
f AC system frequency, in hertz (Hz)
I direct current, in amperes (A)
d
I harmonic RMS current of order n, in amperes (A)
n
L inductance, in henrys (H), referred to the valve winding, between the commutating
voltage source and the point of common coupling between star- and delta-connected
windings. L shall include any external inductance between the transformer line-
winding terminals and the point of connection of the AC harmonic filters.
L inductance, in henrys (H), referred to the valve winding, between the point of
common coupling between star- and delta-connected windings, and the valve. L
shall include the saturated inductance of the valve reactors.
m
electromagnetic notch coupling factor, m = L /(L + L )
1 1 2
n harmonic order
N number of series-connected thyristors per valve
t
P power loss in an item of equipment, in watts (W)
Q
quality factor at harmonic order n
n
R
resistance value, in ohms (Ω)
U direct voltage, in volts (V)
d
U
harmonic RMS voltage of order n, in volts (V)
n
U RMS value of the phase-to-phase no-load voltage on the valve side of the converter
vo
transformer excluding harmonics, in volts (V)
X
inductive reactance at harmonic order n, in ohms (Ω)
n
4 Overview
4.1 General
Suppliers need to know in detail how and where losses are generated, since this affects
component and equipment ratings. Purchasers are interested in a verifiable loss figure which
allows equitable bid comparison and in a procedure after delivery which can objectively verify
the guaranteed performance requirements of the supplier.

As a general principle, it would be desirable to determine the efficiency of an HVDC converter
station by a direct measurement of its energy losses. However, attempts to determine the
station losses by subtracting the measured output power from the measured input power
should recognize that such measurements have an inherent inaccuracy, especially if
performed at high voltage. The losses of an HVDC converter station at full load are generally
less than 1 % of the transmitted power. Therefore, the loss measured as a small difference
between two large quantities is not likely to be a sufficiently accurate indication of the actual
losses.
In some special circumstances, it may be possible, for example, to arrange a temporary test
connection in which two converters are operated from the same AC source and also
connected together via their DC terminals. In this connection, the power drawn from the AC
source equals the losses in the circuit. However, the AC source shall also provide var support
and commutating voltage to the two converters. Once again, there are practical measurement
difficulties.
In order to avoid the problems described above, this document standardizes a method of
calculating the HVDC converter station losses by summing the losses calculated for each item
of equipment. The standardized calculation method will help the purchaser to meaningfully
compare the competing bids. It will also allow an easy generation of performance curves for
the wide range of operating conditions in which the performance has to be known. In the
absence of an inexpensive experimental method which could be employed for an objective
verification of losses during type tests, the calculation method is the next best alternative as it
uses, wherever possible, experimental data obtained from measurements on individual
equipment and components under conditions equivalent to those encountered in real
operation.
The calculation of harmonic currents and voltages in HVDC equipment is described in
Annex A.
It is important to note that the power loss in each item of equipment will depend on the
ambient conditions under which it operates, as well as on the operating conditions or duty
cycles to which it is subjected. Therefore, the ambient and operating conditions shall be
defined for each item of equipment, based on the ambient and operating conditions of the
entire HVDC converter station.
4.2 Ambient conditions
4.2.1 General
A set of standard reference ambient conditions shall be used for determining the power losses
in HVDC converter stations.
4.2.2 Outdoor standard reference temperature
An outdoor ambient dry bulb temperature of 20 °C shall be used as the standard reference
temperature for determining the total converter station losses. Corresponding valve hall
temperature may be defined by the supplier if necessary. The equivalent wet-bulb
temperature (where necessary) shall be defined by the purchaser.
If not defined, the wet-bulb temperature is recommended to be 14 °C, which corresponds to

approximately 50 % RH at 20 °C dry bulb temperature.
4.2.3 Coolant standard reference temperature
Where forced cooling is used for equipment, the flow rate and temperature of the coolant can
influence the temperature rise and associated losses of that equipment. Therefore, the
coolant temperatures and flow rates established by the purchaser and the supplier shall be
used as a basis for determining the losses.

– 10 – IEC 61803:2020 © IEC 2020
4.2.4 Standard reference air pressure
The reference air pressure to be used for the evaluation of total converter station power
losses shall be the standard atmospheric pressure (101,3 kPa) corrected to the altitude of the
installation in question.
4.3 Operating parameters
The losses of an HVDC converter station depend on its operating parameters.
The losses of HVDC converter stations are classified into two categories, referred to as
operating losses (3.1.4 and 3.1.7) and no-load operation losses (3.1.2 and 3.1.6).
The operating losses and auxiliary losses are affected by the load level of the station because
the numbers of certain types of energised equipment (for example harmonic filters and cooling
equipment) may depend upon the load level and because losses in individual items of
equipment themselves vary with the load level.
HVDC converter station losses shall be determined for nominal (balanced) AC system voltage
and frequency, symmetrical impedances of the converter transformer and symmetrical firing
angles. The transformer tap-changer shall be assumed to be in the position corresponding to
nominal AC system voltage or as decided by the control system for the defined operating
condition.
The operating losses shall be determined for the load levels specified by the purchaser, or at
rated load if no such conditions are specified. For each load level, the valve-winding AC
voltage, DC current, converter firing angle, shunt compensation and harmonic filtering
equipment shall be consistent with the respective load level and other specified performance
requirements, relating, for example, to harmonic distortion and reactive power. Cooling and
other auxiliary equipment, as appropriate to the standard reference temperature (see 4.2.2
and 4.2.3), shall be assumed to be connected to support the respective load level.
For the no-load operation mode, converter transformers shall be energised and the converters
blocked. All filters and reactive power compensation equipment shall be assumed to be
disconnected except for those which are required to sustain operation at zero load in order,
for example, to meet the specified reactive power requirements. Station service loads and
auxiliary equipment (e.g. cooling-water pumps) shall be assumed to be connected as required
for immediate pick-up of load for the converter station (without waiting for tap changer
movement) to specified minimum power.
5 Determination of equipment losses
5.1 Thyristor valve losses
5.1.1 General
The loss production mechanisms applicable when the valves are blocked (no-load operation
losses) are different from those applicable in normal operation (operating losses). Operating
losses are dealt with in 5.1.2 to 5.1.11, and no-load operation losses are dealt with in 5.1.12.
Auxiliary losses are dealt with in 5.8.
Typical high-voltage direct current (HVDC) equipment for one pole of a HVDC substation is
shown in Figure 1.
A simplified three-phase diagram of an HVDC 12-pulse converter is shown in Figure 2.
Individual valves are marked in the order of their conduction sequence.

A simplified equivalent circuit of a typical valve is shown in Figure 3. Symbol "th" combines
together the effects of N thyristors connected in series in the valve. C and R are the
t AC AC
corresponding combined values of R-C damping circuits used for voltage sharing and
overvoltage suppression. R represents DC grading resistors and other resistive
DC
components which incur loss when the valve blocks voltage. It also includes the effects of the
includes both stray capacitances and
thyristor leakage current (see 5.1.5 and 5.1.12). C
s
surge distribution capacitors (if used). L represents saturable reactors used to limit the di/dt
s
stresses to safe values and to improve the distribution of fast rising voltages. R represents
s
the resistances of the current conducting components of the valve such as the busbars,
contact resistances, resistance of the windings of the saturable reactors, etc. Power losses in
the valve surge arrester (not shown) shall be neglected.
Figure 4 shows, as an example, current and voltage waveforms of valve 1 (according to Figure 2)
operating in rectifier – Figure 4 a) – and inverter – Figure 4 b) – modes. In the example
shown, the firing instants of the valves of the upper bridge are delayed by 30° with respect to
the valves of the lower bridge due to the phase shift between the two secondaries. For each
valve, the length of the conduction intervals is 130° (2π/3 + μ). During commutations, the
valve current is assumed, for this document, to be changing linearly whereas in reality the
valve currents follow portions of sine waves. This simplification has negligible effect on the
resulting losses, while the trapezoidal waveform significantly simplifies the calculations. The
voltage blocked by the valve shows notches caused by commutations between individual
valves.
5.1.2 Thyristor conduction loss per valve
A typical thyristor on-state characteristic is shown in Figure 5. Thyristor conduction loss
component is the product of the conduction current i(t) – Figure 6 a) – and the corresponding
ideal on-state voltage as shown in Figure 5. Formula P shall be used provided that the DC
V1a
bridge current is well smoothed. In the event that the root sum square value of the DC side
harmonic currents, determined in accordance with Clause A.4, exceeds 5 % of the DC
component, formula P shall be used instead.
V1b
NI×  2π− µ 

td
P U+ RI××
V1a 0 0 d 

32π


n=48

N ××I U N × R 2π − µ

td 0 t 0

P= ++II
V1b d n
∑ 

33 2π

n=12

where
is the current-independent component of the on-state voltage of the average thyristor
U
(see note below), in volts;
R is the slope resistance of the on-state characteristic of the average thyristor (see note
below), in ohms;
th
is the calculated RMS value of the n harmonic current in the bridge DC connection
I
n
according to Clause A.4, in amperes.
NOTE U and R (see Figure 5) are determined from the fully spread on-state voltage measured at the
0 0
appropriate current and junction temperature. The average value of U and R is obtained from production records
0 0
of the thyristors. The temperature dependence of U and R is established from type tests or routine tests on a
0 0
statistically significant number of the thyristors employed, and is used, where necessary, to correct U and R to
0 0
the appropriate service junction temperature. If parallel connection of p thyristors is employed, the appropriate
100 % current is the nominal DC bridge current divided by p. The calculated result is then multiplied by p.
=
– 12 – IEC 61803:2020 © IEC 2020
5.1.3 Thyristor spreading loss per valve
This loss component is an additional conduction loss of the thyristors arising from the delay in
establishing full conduction of the silicon after the thyristor has been turned on. The additional
loss is the product of the current and the voltage by which the thyristor voltage exceeds the
ideal thyristor on-state voltage drop – see the hatched area in Figure 6 b).
t1
P = N××f u t− u t ×i t dt
( ) ( ) ( )
V2 t B A

∫
where
t is the length of the conduction interval, in seconds, which is given by:
π + µ
;
t =
2πf
(t) is the instantaneous on-state voltage, in volts, of a thyristor whose fully spread on-
u
B
state voltage is typical for the thyristors used; the instantaneous on-state voltage shall
be determined for the appropriate junction temperature measured with a trapezoidal
current pulse exhibiting the correct amplitude and commutation overlap periods (see
Figure 5 and Figure 6);
u (t) is the calculated instantaneous on-state voltage of the average thyristor at the same
A
junction temperature for the same current pulse but with the conducting area fully
established throughout the conduction, as derived from its on-state characteristic
represented by U and R only (see Figure 6);
0 0
i(t) is the instantaneous current in the thyristor, in amperes.
Instantaneous on-state voltage data, including the effects of spreading, are usually not
available from production records. Measurements of typical thyristor on-state voltage,
including spreading, should therefore be obtained during the valve periodic firing and
extinction type test (IEC 60700-1:2015, Clause 9) or, alternatively, from a separate laboratory
test on a statistically significant number of thyristors.
5.1.4 Other conduction losses per valve
These are the conduction losses in the main circuit of the valve due to components other than
the thyristors.
R ⋅ I 2π − µ

sd
P =
V3 
32π

where
R is the DC resistance of the valve terminal-to-terminal circuit excluding the thyristors, in
s
ohms (see Figure 3).
The value of R is determined by direct measurement on a representative valve section that
s
includes all elements of the main circuit of a valve in the correct proportions, but in which the
thyristors have been replaced by copper blocks of the appropriate dimensions and with
contacts treated in the same way as for real thyristors. Alternatively, the resistance may be
calculated, in which case the calculation methods shall be documented.

5.1.5 DC voltage-dependent loss per valve
This loss component is the loss in the shunt resistance R of the valve (see Figure 3),
DC
arising from the voltage which appears between valve terminals during the non-conducting
interval (see Figure 4). It includes losses due to thyristor off-state and reverse leakage, losses
in DC grading resistors, other resistive circuits and elements connected in parallel with the
thyristors, resistance of the coolant in coolant pipes, resistivity effects of the structure, fibre
optics, etc.
2 2

U
4 3 6mm−−12 7
v0
P π+ cos 2α+cos 2αµ+2 + sin 2α−sin 2αµ+2+2µ
( ) ( ) ( ) ( )

v4
   
2  π R 3 4 8
DC


where
R is the effective off-state DC resistance of a complete valve determined by measuring
DC
the current drawn during the valve terminal-to-terminal DC voltage type test (according
to IEC 60700-1:2015, 8.3.1) in ohms; if a type test is not performed on the thyristor
valve, R shall be determined by reference to a previous type test (see also the
DC
paragraph after Note 1 below);
m = L /(L + L );
1 1 2
L is the inductance, in henrys, referred to the valve winding, between the commutating
voltage source and the point of common coupling between star- and delta-connected
windings; L shall include any external inductance between the transformer line-
winding terminals and the point of connection of the AC harmonic filters (see Figure 7);
L is the inductance, in henrys, referred to the valve winding, between the point of
common coupling between star- and delta-connected windings, and the valve; L shall
include the saturated inductance of the valve reactors (see Figure 7).
The value of L shall be the same for both secondaries (L = L ) (see Note 2 and last
2 2Δ 2Y
paragraph below).
NOTE 1 The formula for P is valid for µ < π/6 (30°) only.
V4
Since the thyristor resistive leakage current is usually much higher at operating temperatures
than at the prevailing ambient air temperature, it is either necessary to heat the thyristors of
the valve to the correct operating temperature before the measurement of R is taken or to
DC
make later corrections to the measured value using the average thyristor data obtained
separately, to include the mentioned temperature effect (see also 5.1.11). The same pertains
to the liquid coolant.
NOTE 2 The value of m quantifies the effects of inductive coupling between the two secondaries of the converter
transformer. It determines the magnitude of the notches caused by the commutation in the other bridge (notches
from 1' to 3' and from 4' to 6' in Figure 4). If m = 0, then there is no coupling between the two bridges and the
notches from 1' to 3' and from 4' to 6' disappear altogether. The notches in Figure 4 correspond to m = 0,2.
Values of L and L are obtained from the short-circuit impedance measurements on the
1 2
converter transformers, and by adding any external inductances as required. The value of L
includes any external common inductance (such as power line carrier filters) between the
point of common coupling and the commutation voltage source. In cases where no AC
harmonic filters are connected, L also includes the AC system impedance. When separate
transformers supply the star and delta bridges and no additional line-side inductance is
included, L = 0, hence m = 0. When a three-winding transformer construction is employed, a
common winding impedance and mutual coupling effects of the two secondary windings give
non-zero values for L , which may be either positive or negative. For more complicated
transformer arrangements, such as filters connected to a tertiary winding, the values of L and
shall be determined with care.
L
=
– 14 – IEC 61803:2020 © IEC 2020
5.1.6 Damping loss per valve (resistor-dependent term)
This loss component depends on the value of the resistive elements of those circuits that are
AC coupled via series capacitors and on the voltage appearing between valve terminals
during the non-conduction interval.


4π 3 3 3 m μ 7 9m 39m

− + + 6mm−12 − 7 ++− sin2α +
( )

3 2 8 4 8 4 32

  
22 2
P 2πfU C R

V5 v0 AC AC
  
7 3mm3 3 m 33 m 3 m
 + + sin(2α + 2μ
...