IEC TR 62001-1:2016

IEC TR 62001-1 ®
Edition 1.0 2016-05
TECHNICAL
REPORT
colour
inside
High-voltage direct current (HVDC) systems – Guidance to the specification and
design evaluation of AC filters –

Part 1: Overview
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.: +41 22 919 02 11
3, rue de Varembé Fax: +41 22 919 03 00
CH-1211 Geneva 20 info@iec.ch
Switzerland www.iec.ch
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 corrigenda or an amendment might have been published.

IEC Catalogue - webstore.iec.ch/catalogue Electropedia - www.electropedia.org
The stand-alone application for consulting the entire The world's leading online dictionary of electronic and
bibliographical information on IEC International Standards, electrical terms containing 20 000 terms and definitions in
Technical Specifications, Technical Reports and other English and French, with equivalent terms in 15 additional
documents. Available for PC, Mac OS, Android Tablets and languages. Also known as the International Electrotechnical
iPad. Vocabulary (IEV) online.

IEC publications search - www.iec.ch/searchpub IEC Glossary - std.iec.ch/glossary
The advanced search enables to find IEC publications by a 65 000 electrotechnical terminology entries in English and
variety of criteria (reference number, text, technical French extracted from the Terms and Definitions clause of
committee,…). It also gives information on projects, replaced IEC publications issued since 2002. Some entries have been
and withdrawn publications. collected from earlier publications of IEC TC 37, 77, 86 and

CISPR.
IEC Just Published - webstore.iec.ch/justpublished
Stay up to date on all new IEC publications. Just Published IEC Customer Service Centre - webstore.iec.ch/csc
details all new publications released. Available online and If you wish to give us your feedback on this publication or
also once a month by email. need further assistance, please contact the Customer Service
Centre: csc@iec.ch.
IEC TR 62001-1 ®
Edition 1.0 2016-05
TECHNICAL
REPORT
colour
inside
High-voltage direct current (HVDC) systems – Guidance to the specification and

design evaluation of AC filters –

Part 1: Overview
INTERNATIONAL
ELECTROTECHNICAL
COMMISSION
ICS 29.200 ISBN 978-2-8322-3401-3

– 2 – IEC TR 62001-1:2016 © IEC 2016
CONTENTS
FOREWORD .8
INTRODUCTION . 10
1 Scope . 11
2 Terms and definitions . 11
3 Outline of specifications of AC filters for HVDC systems . 12
3.1 General . 12
3.2 Boundaries of responsibility . 13
3.3 Scope of studies . 14
3.4 Scope of supply . 15
3.5 Technical data to be supplied by contractor . 16
3.6 Alternative proposals by bidders . 16
4 Permissible distortion limits . 17
4.1 General . 17
4.2 Voltage distortion . 18
4.2.1 General . 18
4.2.2 Voltage distortion – Definitions of performance criteria . 18
4.2.3 Voltage distortion – Discussion and recommendations . 18
4.2.4 Voltage distortion – Determination of limits . 19
4.2.5 Voltage distortion – Pre-existing harmonic levels . 22
4.2.6 Voltage distortion – Relaxed limits for short term and infrequent
conditions . 23
4.2.7 Treatment of interharmonic frequencies . 23
4.3 Distortion limits pertaining to the HV and EHV network equipment . 24
4.3.1 HVAC transmission system equipment . 24
4.3.2 Harmonic currents in synchronous machines . 24
4.3.3 Nearby HVDC installations . 25
4.4 Telephone interference . 25
4.4.1 General . 25
4.4.2 Causes of telephone interference . 25
4.4.3 Telephone interference – Definitions of performance criteria. 25
4.4.4 Telephone interference – Discussion . 25
4.4.5 Telephone interference – Determination of limits . 26
4.4.6 Telephone interference – Pre-existing harmonic levels . 28
4.4.7 Telephone interference – Limits for temporary conditions . 28
4.5 Special criteria . 29
5 Harmonic generation . 29
5.1 General . 29
5.2 Converter harmonic generation . 29
5.2.1 Idealized conditions . 29
5.2.2 Realistic conditions . 31
5.3 Calculation methodology . 33
5.3.1 General . 33
5.3.2 Harmonic currents for performance, rating and other calculations . 33
5.3.3 Combining harmonics from different converter bridges . 34
5.3.4 Consistent sets . 34
5.3.5 Harmonic generation for different DC power ranges. 35

5.4 Sensitivity of harmonic generation to various factors . 36
5.4.1 Direct current, control angle and commutation overlap. 36
5.4.2 Effect of asymmetries on characteristic harmonics . 37
5.4.3 Converter equipment parameter tolerances . 37
5.4.4 Tap steps . 37
5.4.5 Theoretically cancelled harmonics . 37
5.4.6 Negative and zero phase sequence voltages . 38
5.4.7 Converter transformer saturation . 38
5.4.8 Harmonic interaction across the converter . 39
5.4.9 Back-to-back systems . 39
5.5 Externally generated harmonics . 39
6 Filter arrangements . 40
6.1 Overview . 40
6.2 Advantages and disadvantages of typical filters . 41
6.3 Classification of filter types . 41
6.4 Tuned filters . 42
6.4.1 Single tuned filters . 42
6.4.2 Double tuned filters . 43
6.4.3 Triple tuned filters . 45
6.5 Damped filters . 46
6.5.1 Single tuned damped filters . 46
6.5.2 Double tuned damped filters. 49
6.6 Choice of filters . 49
7 Filter performance calculation . 50
7.1 Calculation procedure . 50
7.1.1 General . 50
7.1.2 Input data . 51
7.1.3 Methodology . 51
7.1.4 Calculation of converter harmonic currents . 52
7.1.5 Selection of filter types and calculation of their impedances . 52
7.1.6 Calculation of performance . 53
7.2 Detuning and tolerances . 54
7.2.1 General . 54
7.2.2 Detuning factors . 54
7.2.3 Resistance variations . 55
7.2.4 Modelling . 55
7.3 Network impedance for performance calculations . 56
7.3.1 General . 56
7.3.2 Network modelling using impedance envelopes . 57
7.3.3 Sector diagram . 58
7.3.4 Circle diagram . 59
7.3.5 Discrete polygons . 59
7.3.6 Zero-sequence impedance modelling . 61
7.3.7 Detailed modelling of AC network for performance calculation . 61
7.4 Outages of filter banks and sub-banks . 62
7.5 Considerations of probability . 63
7.6 Flexibility regarding compliance . 65
7.7 Ratings of the harmonic filter equipment . 65
8 Filter switching and reactive power management . 65

– 4 – IEC TR 62001-1:2016 © IEC 2016
8.1 General . 65
8.2 Reactive power interchange with AC network . 66
8.2.1 General . 66
8.2.2 Impact on reactive compensation and filter equipment . 66
8.2.3 Evaluation of reactive power interchange . 67
8.3 HVDC converter reactive power capability . 67
8.4 Bank/sub-bank definitions and sizing . 67
8.4.1 General . 67
8.4.2 Sizing . 68
8.5 Hysteresis in switching points . 70
8.6 Converter Q-V control near switching points . 71
8.7 Operation at increased converter control angles . 71
8.8 Filter switching sequence and harmonic performance . 71
8.9 Demarcation of responsibilities . 72
8.9.1 General . 72
8.9.2 Customer . 72
8.9.3 Contractor . 73
9 Customer specified parameters and requirements . 73
9.1 General . 73
9.2 AC system parameters . 73
9.2.1 Voltage . 73
9.2.2 Voltage unbalance . 74
9.2.3 Frequency . 74
9.2.4 Short circuit level . 74
9.2.5 Filter switching . 75
9.2.6 Reactive power interchange . 75
9.2.7 System harmonic impedance . 75
9.2.8 Zero sequence data . 75
9.2.9 System earthing . 75
9.2.10 Insulation level . 75
9.2.11 Creepage distances . 75
9.2.12 Pre-existing voltage distortion . 75
9.3 Harmonic distortion requirements . 76
9.3.1 General . 76
9.3.2 Redundancy requirements . 76
9.4 Environmental conditions . 76
9.4.1 Temperature . 76
9.4.2 Pollution . 76
9.4.3 Wind . 77
9.4.4 Ice and snow loading (if applicable) . 77
9.4.5 Solar radiation . 77
9.4.6 Isokeraunic levels . 77
9.4.7 Seismic requirements . 77
9.4.8 Audible noise . 77
9.5 Electrical environment . 77
9.6 Requirements for filter arrangements and components . 78
9.6.1 Filter arrangements . 78
9.6.2 Filter capacitors . 78
9.6.3 Test requirements . 78

9.7 Protection of filters . 78
9.8 Loss evaluation . 78
9.9 Field measurements and verifications . 78
9.10 General requirements . 79
10 Future developments . 79
10.1 General . 79
10.2 New filter technology . 79
10.2.1 General . 79
10.2.2 Automatically tuned reactors . 80
10.2.3 Single-phase redundancy . 82
10.2.4 Fuseless capacitors . 83
10.2.5 Active filters . 84
10.2.6 Compact design . 85
10.2.7 Other filter circuit components . 86
10.3 New converter technology . 87
10.3.1 General . 87
10.3.2 Series commutated converters . 87
10.3.3 PWM voltage-sourced converters . 88
10.3.4 Transformerless converters . 90
10.3.5 Unit connection . 91
10.4 Changing external environment . 91
10.4.1 Increased pre-existing levels of harmonic distortion . 91
10.4.2 Developments in communication technology . 92
10.4.3 Changes in structure of the power supply industry . 92
10.4.4 Focus on power quality . 93
Annex A (informative) Alternative type of procurement procedure . 94
Annex B (informative) Formulae for calculating the characteristic harmonics of a
bridge converter . 95
Annex C (informative) Definition of telephone interference parameters . 97
C.1 General . 97
C.2 Criteria according to European practice . 97
C.3 Criteria according to North American practice . 98
C.4 Discussion . 99
Annex D (informative) Equivalent frequency deviation . 101
Annex E (informative) Reactive power management . 102
E.1 HVDC converter reactive power capability . 102
E.1.1 Steady-state capability . 102
E.1.2 Temporary capability . 104
E.2 Converter Q-V control near switching points . 105
E.3 Step-change in voltage on switching a filter . 106
Annex F (informative) Voltage sourced converters . 108
F.1 General . 108
F.2 Two-level converter with PWM . 108
F.3 Three-level converter with PWM . 110
F.4 Multi-level converters . 111
F.5 Modelling of VSCs for harmonic filtering purposes . 112
Bibliography . 114

– 6 – IEC TR 62001-1:2016 © IEC 2016
Figure 1 – Idealized current waveforms on the AC side of converter transformer . 30
Figure 2 – Realistic current waveforms on the AC side of converter transformer
including effect of non-idealities . 31
Figure 3 – Comparison of harmonic content of current waveform under idealized and
realistic conditions . 32
Figure 4 – Typical variation of characteristic harmonic magnitude with direct current . 36
Figure 5 – Single tuned filter and frequency response . 42
Figure 6 – Double tuned filter and frequency response . 44
Figure 7 – Triple tuned filter and frequency response . 45
Figure 8 – 2nd order damped filter and frequency response . 47
Figure 9 – 3rd order damped filter and frequency response . 47
Figure 10 – C-type filter and frequency response . 48
Figure 11 – Double tuned damped filter and frequency response . 49
Figure 12 – Circuit model for filter calculations . 51
Figure 13 – AC system impedance general sector diagram, with minimum impedance . 58
Figure 14 – AC system impedance general sector diagram, with minimum resistance . 58
Figure 15 – AC system impedance general circle diagram, with minimum resistance . 59
Figure 16 – Example of harmonic impedances for harmonics of order 2 to 4 . 60
Figure 17 – Example of harmonic impedances for harmonics of order 5 to 8 . 60
Figure 18 – Example of harmonic impedances for harmonics of order 9 to 13 . 60
Figure 19 – Example of harmonic impedances for harmonics of order 14 to 49 . 60
Figure 20 – Illustration of basic voltage quality concepts with time/location statistics
covering the whole system (adapted from IEC TR 61000-3-6:2008) . 64
Figure 21 – Example of range of operation where specifications on harmonic levels
are not met for a filter scheme solution . 64
Figure 22 – Branch, sub-bank and bank definition . 68
Figure 23 – Typical switching sequence . 72
Figure 24 – Reactive power components . 73
Figure 25 – Design principle of a self-tuned reactor using DC control current in an

orthogonal winding . 81
Figure 26 – Control principle for self-tuned filter . 81
Figure 27 – One method of switching a redundant single phase filter . 83
Figure 28 – Fuseless capacitor design compared to internal and external fused units . 84
Figure 29 – Various possible configurations of series compensated HVDC converters . 89
Figure 30 – Circuit and waveforms of a DC link using voltage-sourced converters . 90
Figure E.1 – Capability diagram of a converter under different control strategies . 102
Figure E.2 – Converter capability with γ = 17°, γ = 40°, α = 5°, α = 35°
min max min max
and U = 1,2U . 103
diomax dioN
Figure E.3 – Reactive power absorption of a rectifier as a function of α with
U = U , d = 9,4 % and d = 0,2 % . 105
dio dioN x r
Figure E.4 – Reactive power absorption of a inverter as a function of γ with
U = U , d = 9,4 % and d = 0,2 % . 105
dio dioN x r
Figure F.1 – Simplified representation of a 2-level voltage sourced converter . 109
Figure F.2 – Single-phase AC output for 2-level converter with PWM switching at 21
times fundamental frequency . 109
Figure F.3 – Simplified representation of a 3-level voltage sourced converter . 110

Figure F.4 – Single-phase AC output for 3-level converter with PWM switching at 21
times fundamental frequency . 110
Figure F.5 – Basic operation of the MMC converters . 111
Figure F.6 – Phase unit of the modular multi-level converter (MMC) in basic half-
bridge, without series-connected IGBTs (left) and the cascaded two level (CTL)
converter with series-connected IGBTs (right) . 113
Figure F.7 – Representation of a voltage sourced converter as a harmonic voltage
source behind an inductance . 113

– 8 – IEC TR 62001-1:2016 © IEC 2016
INTERNATIONAL ELECTROTECHNICAL COMMISSION
____________
HIGH-VOLTAGE DIRECT CURRENT (HVDC) SYSTEMS – GUIDANCE TO
THE SPECIFICATION AND DESIGN EVALUATION OF AC FILTERS –

Part 1: Overview
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.
The main task of IEC technical committees is to prepare International Standards. However, a
technical committee may propose the publication of a Technical Report when it has collected
data of a different kind from that which is normally published as an International Standard, for
example "state of the art".
IEC TR 62001-1, which is a Technical Report, 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 first edition of IEC TR 62001-1, together with IEC TR 62001-2 , IEC TR 62001-3 and
IEC TR 62001-4, cancels and replaces IEC TR 62001 published in 2009. This edition
constitutes a technical revision.
___________
To be published.
IEC TR 62001-1 includes the following significant technical changes with respect to
IEC TR 62001:
a) Clauses 3 to 5, 7 to 9, 17, 20, Annexes A and C to E have been expanded and
supplemented;
b) Annexes C and F on the definition of telephone interference parameters and voltage
sourced converters have been added.
The text of this document is based on the following documents:
Enquiry draft Report on voting
22F/378/DTR 22F/384A/RVC
Full information on the voting for the approval of this document can be found in the report on
voting indicated in the above table.
This publication has been drafted in accordance with the ISO/IEC Directives, Part 2.
A list of all parts in the IEC TR 62001 series, published under the general title High-voltage
direct current (HVDC) systems – Guidance to the specification and design evaluation of AC
filters, can be found on the IEC website.
The committee has decided that the contents of this publication will remain unchanged until
the stability date indicated on the IEC 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.
A bilingual version of this publication may be issued at a later date.

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.
– 10 – IEC TR 62001-1:2016 © IEC 2016
INTRODUCTION
IEC TR 62001 is structured in four parts:
Part 1 – Overview
This part concerns specifications of AC filters for high-voltage direct current (HVDC) systems
with line-commutated converters, permissible distortion limits, harmonic generation, filter
arrangements, filter performance calculation, filter switching and reactive power management
and customer specified parameters and requirements.
Part 2 – Performance
This part deals with current-based interference criteria, design issues and special
applications, field measurements and verification.
Part 3 – Modelling
This part addresses the harmonic interaction across converters, pre-existing harmonics, AC
network impedance modelling, simulation of AC filter performance.
Part 4 – Equipment
This part concerns steady-state and transient ratings of AC filters and their components,
power losses, audible noise, design issues and special applications, filter protection, seismic
requirements, equipment design and test parameters.

HIGH-VOLTAGE DIRECT CURRENT (HVDC) SYSTEMS – GUIDANCE TO
THE SPECIFICATION AND DESIGN EVALUATION OF AC FILTERS –

Part 1: Overview
1 Scope
This part of IEC TR 62001, which is a Technical Report, provides guidance on the
specifications of AC filters for high-voltage direct current (HVDC) systems with line-
commutated converters and filter performance calculation.
This document deals with the specification and design evaluation of AC side harmonic
performance and AC side filters for HVDC schemes. It is intended to be primarily for the use
of the utilities and consultants who are responsible for issuing the specifications for new
HVDC projects and evaluating designs proposed by prospective suppliers.
The scope of this document covers AC side filtering for the frequency range of interest in
terms of harmonic distortion and audible frequency disturbances. It excludes filters designed
to be effective in the Power Line Carrier (PLC) and radio interference spectra.
The bulk of this document concentrates on the "conventional" AC filter technology and line-
commutated HVDC converters. The changes entailed by new technologies are also
discussed.
2 Terms and definitions
For the purposes of this document, the following terms and definitions apply.
2.1
specification
document which defines the overall system requirements for an AC filter and the AC system
environment in which it operates
Note 1 to entry: Such a document is normally issued by utilities to the prospective HVDC manufacturers. It also
ensures the uniformity of proposals and sets guidelines for the evaluation of bids.
Note 2 to entry: The term as used here does not refer to the detailed engineering specifications relating to
individual items of equipment, which are prepared by the HVDC manufacturer as a result of the filter design
process.
Note 3 to entry: The specification defines the technical basis for a contract between two parties: the customer
(2.2) and the contractor (2.3).
2.2
customer
organization which is purchasing the HVDC converter station, including the AC filters
Note 1 to entry: The term “customer” is taken to cover similar terms which may be used in specifications, such as
owner, client, buyer, utility, user, employer and purchaser, and also covers a consultant representing the
customer.
2.3
contractor
organization which has the overall responsibility for delivery of the HVDC converter station,
including the AC filters, as a system

– 12 – IEC TR 62001-1:2016 © IEC 2016
Note 1 to entry: The contractor may in turn contract one or more sub-suppliers of individual items of equipment.
Note 2 to entry: The term “contractor” is taken to cover similar terms which may be used in specifications, such
as manufacturer, or supplier.
Note 3 to entry: Where the context clearly refers to the pre-contract stage of a project, the word “bidder” has
been used instead of “contractor”, to indicate a prospective contractor, or tenderer.
2.4
branch
arm
set of components (capacitor, inductor, resistor), either in singular or interconnected
arrangement, which may be isolated off load for maintenance
Note 1 to entry: In interconnected arrangement, it forms a smallest tuned filter unit.
SEE: Figure 22
2.5
sub-bank
one or more branches which can be switched (connected or disconnected) on load for
reactive power control
Note 1 to entry: The switch does not necessarily need to have fault clearing capability.
SEE: Figure 22
2.6
bank
one or more sub-banks which can be switched together by a circuit breaker
SEE: Figure 22
3 Outline of specifications of AC filters for HVDC systems
3.1 General
When installing an HVDC converter station in an AC system, the way in which it may affect
the quality of power supply in that system is always an important issue. One of the main
power quality topics is that of harmonic performance.
The AC side current of an HVDC converter has a highly non-sinusoidal waveform, and, if
allowed to flow in the connected AC system, might produce unacceptable levels of distortion.
AC side filters are therefore required as part of the total HVDC converter station, in order to
reduce the harmonic distortion of the AC side current and voltage to acceptably low levels.
HVDC converters also consume substantial reactive power, a large proportion of which is
normally supplied locally within the converter station. Shunt connected AC filters appear as
capacitive sources of reactive power at fundamental frequency, and normally in conventional
HVDC schemes the AC filters are used to compensate most or all of the reactive
consumption of the converter. Additional shunt capacitors and reactors may also be used to
ensure that the desired reactive balance is maintained within specified limits under defined
operational conditions.
The design of the AC filters therefore normally has to satisfy these two requirements of
harmonic filtering and reactive power compensation, for various operational states and load
levels. Optimization of this design is the task of the AC filter designer, and the constraints
under which the design is made are defined in the specification.
The AC filters form a substantial part of a conventional HVDC converter station. The
fundamental reactive power rating of the AC filters (including shunt capacitors where

applicable) at each converter station has typically been in the range of 50 % to 60 % of the
active power rating of the scheme. Together with the required switchyard equipment, the AC
filters can occupy over half of the total land requirements of an HVDC scheme. The cost of
manufacture, installation and commissioning of the AC filter equipment is significant, being
typically in the approximate range of 10 % of the total station costs. In addition,
...