IEC TR 63363-1:2022

IEC TR 63363-1 ®
Edition 1.0 2022-05
TECHNICAL
REPORT
colour
inside
Performance of voltage sourced converter (VSC) based high-voltage direct
current (HVDC) transmission –
Part 1: Steady-state conditions
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IEC TR 63363-1 ®
Edition 1.0 2022-05
TECHNICAL
REPORT
colour
inside
Performance of voltage sourced converter (VSC) based high-voltage direct

current (HVDC) transmission –
Part 1: Steady-state conditions

INTERNATIONAL
ELECTROTECHNICAL
COMMISSION
ICS 29.200; 29.240.01 ISBN 978-2-8322-2198-3

– 2 – IEC TR 63363-1:2022  IEC 2022
CONTENTS
FOREWORD . 6
INTRODUCTION . 8
1 Scope . 9
2 Normative references . 9
3 Terms, definitions and abbreviated terms . 10
3.1 Terms and definitions . 10
3.2 Abbreviated terms . 11
4 Classifications of VSC HVDC systems . 12
4.1 General . 12
4.2 Symmetrical monopolar HVDC system . 12
4.3 Asymmetrical monopolar HVDC system . 13
4.3.1 General . 13
4.3.2 ASMP with earth return . 13
4.3.3 ASMP with metallic return . 13
4.4 Bipolar HVDC system . 14
4.4.1 General . 14
4.4.2 Bipolar HVDC with earth return . 14
4.4.3 Rigid bipolar configuration . 14
4.4.4 Bipolar HVDC with dedicated metallic return . 15
4.5 Back-to-back HVDC system . 15
4.6 Interface transformer arrangements . 15
4.7 Switching and reconfiguration . 16
4.7.1 Converter station and DC yard switching . 16
4.7.2 Transition station switching . 17
4.7.3 Connecting multiple converters . 18
4.7.4 DC gas-insulated metal enclosed switchgear (DC GIS) . 22
5 Environmental information . 22
6 Rated power, current and voltage . 24
6.1 Rated power . 24
6.2 Rated DC current . 24
6.3 Rated DC voltage . 25
7 Steady-state operation . 25
7.1 General . 25
7.2 PQ diagram. 25
7.3 UQ diagram . 26
7.4 Reactive power exchange . 27
8 Overload and equipment capability . 28
8.1 Overload . 28
8.2 Equipment capability . 28
8.2.1 General . 28
8.2.2 Converter valve capability . 29
8.2.3 Capability of oil-cooled transformers and dry type reactors . 29
8.2.4 Capability of other converter station equipment . 29
9 Converter station types and operation modes . 29
9.1 Converter station types . 29
9.2 Operation modes . 31

9.2.1 Reduced direct voltage operation . 31
9.2.2 Full direct voltage operation . 31
9.2.3 Operating sequences . 31
10 AC system . 33
10.1 General . 33
10.2 AC voltage . 34
10.2.1 Steady-state voltage range . 34
10.2.2 Negative sequence voltage . 34
10.3 Frequency . 34
10.3.1 Rated frequency . 34
10.3.2 Steady-state frequency range . 34
10.3.3 Short-term frequency variation . 34
10.3.4 Frequency variation during emergency . 35
10.4 AC voltage and frequency operation ranges . 35
10.5 System impedance . 35
10.6 Positive and zero-sequence surge impedance. 36
10.7 Other sources of harmonics . 36
11 Reactive power . 36
11.1 General . 36
11.2 VSC HVDC systems . 36
12 HVDC transmission line, earth electrode line and earth electrode . 37
12.1 General . 37
12.2 Overhead line(s) . 37
12.2.1 General . 37
12.2.2 Electrical parameters . 37
12.3 Cable(s) . 38
12.3.1 General . 38
12.3.2 Electrical parameters . 38
12.4 Transmission line combined with overhead line and cable section . 39
12.5 Electrode line . 39
12.6 Earth electrode . 39
12.7 Gas insulated line . 39
13 Reliability . 39
14 HVDC control . 39
14.1 General . 39
14.2 Control objectives . 40
14.3 Control structure . 40
14.3.1 General . 40
14.3.2 HVDC bipole/station control . 41
14.3.3 HVDC pole control . 42
14.3.4 Converter and valve control . 43
14.4 Measurement . 43
15 Telecommunication . 44
15.1 Types of telecommunication links . 44
15.2 Classification of data to be shared . 44
15.3 Fast response telecommunication . 44
16 Auxiliary systems . 45
16.1 General . 45

– 4 – IEC TR 63363-1:2022  IEC 2022
16.2 Electrical auxiliary system . 45
16.2.1 General . 45
16.2.2 Auxiliary power supplies . 45
16.2.3 Batteries and uninterruptible power supplies (UPS) . 46
16.2.4 Emergency supply . 46
16.3 Mechanical auxiliary system . 47
17 Audible noise . 48
17.1 General . 48
17.2 Public nuisance. 48
17.2.1 Valves and valve coolers . 48
17.2.2 Interface transformers . 48
17.2.3 Reactors . 48
17.3 Noise in working areas . 49
18 AC side harmonics . 49
18.1 General . 49
18.2 Harmonic sources . 50
18.2.1 General . 50
18.2.2 Converter generated harmonics . 50
18.2.3 Pre-existing network harmonics . 50
18.3 Total harmonic distortion . 51
19 DC side harmonics . 51
19.1 General . 51
19.2 Coupling between parallel AC and DC circuits . 52
20 Power line carrier (PLC) interference . 53
20.1 General . 53
20.2 Performance specification . 54
21 Radio frequency interference . 54
21.1 General . 54
21.2 RFI from HVDC systems . 54
21.2.1 RFI sources . 54
21.2.2 RFI propagation . 55
22 Power losses . 55
Annex A (informative) Fundamental PQ equations of the VSC converter station. 56
Annex B (informative) Reactive power exchange of the VSC converter station . 58
Bibliography . 59

Figure 1 – Symmetrical monopolar VSC HVDC system . 13
Figure 2 – Asymmetrical monopolar VSC HVDC system with earth return . 13
Figure 3 – Asymmetrical monopolar VSC HVDC system with metallic return . 13
Figure 4 – Bipolar VSC HVDC system with earth return . 14
Figure 5 – Rigid bipolar VSC HVDC system . 15
Figure 6 – Bipolar HVDC system with dedicated metallic return . 15
Figure 7 – DC switching of line conductors . 17
Figure 8 – DC switching – Overhead line to cable . 18
Figure 9 – Examples of VSC HVDC system with two converter units per pole . 19
Figure 10 – Example of PQ diagram of the VSC converter . 26

Figure 11 – Example of UQ diagram of the VSC converter . 27
Figure 12 – Reactive power exchanges of the VSC converter station at PCC . 28
Figure 13 – AC/DC converter station types in the U/I diagram . 30
Figure 14 – Operating sequence transitions of the VSC HVDC system . 32
Figure 15 – Example of the AC grid voltage and frequency operation ranges . 35
Figure 16 – Hierarchical structure of an HVDC control system . 41
Figure 17 – HVDC pole control . 43
Figure 18 – Harmonic contribution by the VSC converter . 50
Figure 19 – Amplification of the pre-existing network harmonics . 51
Figure 20 – Example of separate AC and DC tower configurations . 52
Figure 21 – Example of hybrid AC and DC tower configuration . 53
Figure A.1 – Simple configuration of the VSC converter station to AC grid . 56
Figure A.2 – Example of power-circle diagrams of the VSC converter . 57
Figure B.1 – Simplified equivalent AC grid at PCC of the VSC converter station . 58

Table 1 – Information supplied for HVDC substation . 22

– 6 – IEC TR 63363-1:2022  IEC 2022
INTERNATIONAL ELECTROTECHNICAL COMMISSION
____________
PERFORMANCE OF VOLTAGE SOURCED CONVERTER (VSC) BASED
HIGH-VOLTAGE DIRECT CURRENT (HVDC) TRANSMISSION –

Part 1: Steady-state conditions

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 permitted International Standards, Technical Specifications,
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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
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6) All users should ensure that they have the latest edition of this publication.
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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.
IEC TR 63363-1 has been prepared by IEC technical committee 115: High Voltage Direct
Current (HVDC) transmission for DC voltages above 100 kV and IEC subcommittee 22F: Power
electronics for electrical transmission and distribution systems. It is a Technical Report.
The text of this Technical Report is based on the following documents:
Draft Report on voting
115/281/DTR 115/298/RVDTR
Full information on the voting for its approval can be found in the report on voting indicated in
the above table.
The language used for the development of this Technical Report is English.

A list of all parts in the IEC 63363 series, published under the general title Performance of
voltage sourced converter (VSC) based high-voltage direct current (HVDC) transmission, can
be found on the IEC website.
This document was drafted in accordance with ISO/IEC Directives, Part 2, and developed in
accordance with ISO/IEC Directives, Part 1 and ISO/IEC Directives, IEC Supplement, available
at www.iec.ch/members_experts/refdocs. The main document types developed by IEC are
described in greater detail at www.iec.ch/standardsdev/publications.
The committee has decided that the contents of this document will remain unchanged until the
stability date indicated on the IEC website under webstore.iec.ch in the data related to the
specific document. At this date, the document will be
• reconfirmed,
• withdrawn,
• replaced by a revised edition, or
• amended.
IMPORTANT – The "colour inside" logo on the cover page of this document 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.

– 8 – IEC TR 63363-1:2022  IEC 2022
INTRODUCTION
High-voltage direct current (HVDC) is an established technology that has been in commercial
use for more than 60 years. With the changes in demands due to evolving environmental needs,
installation of HVDC systems has increased dramatically in the last 30 years and almost half of
the world's HVDC projects were commissioned after the year 2000. HVDC has become a
common tool in the design of future global transmission systems.
An HVDC system transmits more electrical power over longer distances than a similar
alternating current (AC) transmission system, which means fewer transmission lines are needed,
saving both money and land and simplifying approvals. In addition to significantly lowering
electrical losses over long distances, HVDC transmission is also very stable and easily
controlled, and can stabilize and interconnect AC power networks that are otherwise
incompatible. Typically, an HVDC system provides unique or superior capabilities in the
following aspects:
– long distance bulk power transmission;
– asynchronous interconnections;
– long distance cable;
– controllability;
– lower losses;
– environmental concerns;
– limitation of short-circuit currents.
The voltage sourced converter (VSC) HVDC transmission system is a new generation of HVDC
transmission technology, which can increase the reliability of power grids and provide an
alternative to connecting wind farms or solar farms to power grids, providing power to islands,
connecting asynchronous grids and building direct current (DC) grids. VSC HVDC can provide:
– independent decoupled control of active and reactive power;
– power supply for weak or even passive networks without a need for AC network to provide
commutating voltage;
– simultaneous support of both active and reactive power to the AC power systems, which is
beneficial for enhancing system reliability and improving power quality.
Simply due to these technical merits, the market demand for VSC HVDC transmission
technology is spreading widely over the world. VSC HVDC has been selected for a number of
transmission projects aimed at exchanging energy between areas and connection of remote
renewable energy sources such as offshore wind farms to onshore.
With the fast development of the VSC HVDC power transmission industry, IEC standardization
work has been carried out accordingly. Up to the time of writing, more than four IEC documents,
related to VSC DC equipment and systems have been published. Among these, IEC 62747,
IEC TR 62543, IEC 62501, and the IEC TS 62751 series provide essential information for the
design and operation of VSC HVDC transmission systems.
This document provides, as a supplement to above publications, a basic guide in VSC HVDC
transmission system design and operation.
This document is part one of a series of three intended technical reports, covering steady-state
performance, while parts two and three (yet to be published) are intended to cover transient
performance and dynamic performance, respectively.

PERFORMANCE OF VOLTAGE SOURCED CONVERTER (VSC) BASED
HIGH-VOLTAGE DIRECT CURRENT (HVDC) TRANSMISSION –

Part 1: Steady-state conditions

1 Scope
The objective of this Technical Report is to present the "state of the art" with respect to general
guidance on the steady-state performance demands of VSC HVDC transmission systems. It
concerns the steady-state performance of two-terminal VSC HVDC transmission systems
utilizing converters with power flow capability in both directions.
Different configurations of a VSC HVDC transmission system are covered in this document,
including the symmetrical monopolar, asymmetrical monopolar, bipolar with earth return, bipolar
with dedicated metallic return and rigid bipolar configurations.
There are many variations between different VSC HVDC transmission systems. This document
does not consider these in detail; consequently, it cannot be used directly as a specification for
a particular project, but rather to provide the general basis for the system steady-state
performance demands.
Normally, the performance specifications are based on a complete system including two VSC
HVDC converter stations. However, sometimes a VSC HVDC transmission system can also be
separately specified and purchased from multiple vendors instead of single turnkey vendor. In
such cases, due consideration can be given to the coordination of each part with the overall
VSC HVDC system performance objectives and the interface of each with the system can be
clearly defined. The major components of the VSC HVDC transmission system are presented
in IEC 62747.
Referring to IEC 62747, an HVDC substation/converter station is defined as that part of the
VSC HVDC transmission system which consists of one or more VSC converter units installed
in a single location together with buildings, reactors, filters, reactive power supply, control,
monitoring, protective, measuring and auxiliary equipment. The AC substations are not covered
in this document.
This document provides guidance and supporting information on the procedure for system
design and the technical issues involved in the system design of VSC HVDC transmission
projects for both owners and contractors. This document can be used as the basis for drafting
a procurement specification and as a guide during project implementation.
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 62747:2014, Terminology for voltage-sourced converters (VSC) for high-voltage direct
current (HVDC) systems
IEC 62747:2014/AMD1:2019
– 10 – IEC TR 63363-1:2022  IEC 2022
3 Terms, definitions, and abbreviated terms
For the purposes of this document, the terms, definitions and abbreviated terms given in
IEC 62747 and the following apply.
IEC and ISO 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
VSC phase unit
equipment used to connect the two DC terminals to one AC terminal
Note 1 to entry: In the simplest implementation, the VSC phase unit consists of two VSC valves, and in some case,
it can include also valve reactors. The VSC phase unit can also include control and protection equipment, and other
components.
[SOURCE: IEC 62747:2014, 7.7]
3.1.2
VSC unit
three VSC phase units, together with VSC unit control equipment, essential protective and
switching devices, DC storage capacitors, phase reactors and auxiliaries, if any, used for
conversion
[SOURCE: IEC 62747:2014, 7.6]
3.1.3
VSC converter unit
indivisible operative unit comprising all equipment between the point of connection on the AC
side and the point of connection on the DC side, essentially one or more VSC converters,
together with one or more interface transformers, converter unit control equipment, essential
protective and switching devices and auxiliaries, if any, used for conversion
[SOURCE: IEC 62747:2014, 7.5, modified – Addition of "VSC" to the term "converter unit" and
in the definition replacement of "common coupling" with "connection" and "VSC units" with "VSC
converters".]
3.1.4
VSC converter station
part of an VSC HVDC system which consists of one or more VSC converter units including DC
switchgear, DC fault current controlling devices, if any, installed in a single location together
with buildings, reactors, filters, reactive power supply, control, monitoring, protective,
measuring and auxiliary equipment
3.1.5
VSC HVDC system
high-voltage direct current transmission system connecting two VSC converter stations
transferring energy in the form of HVDC including related transmission lines and/or cables,
switching stations, if any, as well as other equipment and sub-systems needed for operation

3.2 Abbreviated terms
The following abbreviated terms are used in the document.
AC alternating current
AM amplitude modulation
ASMP asymmetrical monopole
BPS bypass switch
BtB back-to-back
BES battery energy storage
C&P control and protection
CPS converter paralleling switch
DC direct current
DCCT current transformer for DC application
DCVT voltage transformer for DC application
DG diesel generator
DMR dedicated metallic return
DMRTS dedicated metallic return transfer switch
EMC electromagnetic compatibility
ERTS earth return transfer switch
FACTS flexible AC transmission systems
FB full-bridge
GIL gas-insulated transmission line
GIS gas-insulated metal enclosed switchgear
HB half-bridge
HV high voltage
HVDC high-voltage direct current
IGBT insulated-gate bipolar transistor
ITU international telecommunication union
LCC line-commutated converter
MMC modular multi-level converter
MV medium voltage
NBS neutral bus switch
NBES neutral bus earthing switch
PCC point of common coupling
PLC power line carrier
p.u. per unit
RF radio frequency
RFI radio frequency interference
RMS root mean square
SCADA supervisory control and data acquisition
SCL short-circuit level
SCR short-circuit ratio
SMP symmetrical monopole
– 12 – IEC TR 63363-1:2022  IEC 2022
SNR signal-to-noise ratio
SSTI sub-synchronous torsional interaction
STATCOM static synchronous reactive power compensator
UPS uninterruptible power system
VCU valve control units
VBC valve base controller
VBE valve base electronics
VSC voltage sourced converter
4 Classifications of VSC HVDC systems
4.1 General
Generally, in studies of projects of the classifications of VSC HVDC systems, this document
focuses on the two-terminal point-to-point configuration. The economic considerations can take
into account the capital costs, the cost of losses, cost of outages and other expected annual
expenses. The voltage and current ratings for a given power rating can be optimized to achieve
the lowest system cost, including the evaluated cost of losses. Ordinarily, the user does not
need to specify the direct voltage and current ratings, unless there are specific reasons to do
so, for example, for compatibility with an already existing station, to provide for a future
extension or for some other reasons.
The VSC HVDC system can be operated in different configurations such as with or without
transmission lines, monopolar or bipolar configurations, etc., which are further divided and
shown below:
– symmetrical monopolar HVDC system,
– asymmetrical monopolar HVDC system,
– bipolar HVDC system,
– back-to-back HVDC system.
In each configuration above, the VSC HVDC system can also be classified in terms of:
– series and parallel connections of the VSC converter units,
– interface transformer arrangements.
4.2 Symmetrical monopolar HVDC system
In a symmetrical monopole (SMP), the HVDC system employs one VSC converter per station
feeding a symmetrical transmission line with equal line to ground voltages on the positive and
negative poles and no low impedance ground connection. One of the advantages is that the
interface transformers are not exposed to DC voltage under normal operating conditions hence
their design is similar to that of conventional high voltage AC transmission transformers. A
defined impedance to ground is needed at DC side or AC side in order to control the DC voltages
to ground including balancing the positive and negative pole DC voltages. Figure 1 shows a
simplified illustration of an SMP system with AC side earthing impedance.

Figure 1 – Symmetrical monopolar VSC HVDC system
4.3 Asymmetrical monopolar HVDC system
4.3.1 General
With an asymmetrical monopole (ASMP), the asymmetrical monopolar configuration can be the
first stage in the development of a bipolar scheme. An ASMP HVDC system typically features
one converter at each end of the transmission line. Voltages of the two DC output terminals of
the converter are asymmetrical. One end of the converter can be grounded directly on the DC
side, through an impedance or through the electrode transmission line. The DC side
configuration of an ASMP system can be with earth return or metallic return, as shown in
Figure 2 and Figure 3.
Figure 2 – Asymmetrical monopolar VSC HVDC system with earth return

Figure 3 – Asymmetrical monopolar VSC HVDC system with metallic return
4.3.2 ASMP with earth return
For an ASMP with earth return scheme, as illustrated in Figure 2, the system also needs an
earth electrode line and continuously operable earth electrodes at the two ends of the
transmission. The presence of current through the earth involves issues such as corrosion,
magnetic field effects, etc., covered in IEC TS 62334.
4.3.3 ASMP with metallic return
For an ASMP with metallic return scheme, as illustrated in Figure 3, the metallic return
configuration can generally be used for technical and/or economical optimization such as:
a) as the first stage in the construction of a bipolar system and if long-term flow of earth current
is undesirable during the interim period. In such circumstances, the return path can be
through the other pole line, or;
b) if the transmission line length is short enough to make it uneconomical and undesirable to
build earth electrode lines and earth electrodes, or;

– 14 – IEC TR 63363-1:2022  IEC 2022
c) if the earth resistivity is high enough to impose an unreasonable economic penalty, or;
d) if long-term flow of earth current is unsuitable, e.g., because of environmental and safety
regulations.
This metallic return configuration utilizes one pole conductor and one dedicated metallic return
conductor. The neutral is connected at one of the two HVDC substations to its station earth
either directly or via an impedance or, alternatively, to the associated earth electrode. The other
HVDC substation neutral can be connected to its station earth through a capacitor or an arrester
or both.
NOTE The metallic return conductor can be either a dedicated neutral conductor or another high voltage conductor.
4.4 Bipolar HVDC system
4.4.1 General
For a bipolar HVDC system, there are three configurations as given below:
• bipolar HVDC with earth return,
• rigid bipolar configuration,
• bipolar HVDC with dedicated metallic return.
The main advantage of this bipolar configuration is that it retains an availability of 50 % of the
transmission capacity in case of one converter outage. In such cases the HVDC system
operates as a monopole.
With the bipolar configuration, one pole has positive polarity to earth and the other pole has
negative polarity to earth. For power flow direction change, the two poles reverse the directions
of their currents rather than the polarities of their voltages. When both poles are in operation,
the unbalance current flowing in the earth path can be kept at a very low value.
4.4.2 Bipolar HVDC with earth return
This arrangement is used when a DC transmission line connects two HVDC converter stations
with electrodes provided for earth return operation, as shown in Figure 4. It is effectively
equivalent to a double-circuit AC transmission. When combined, two monopolar earth return
schemes can give a bipolar scheme.

Figure 4 – Bipolar VSC HVDC system with earth return
4.4.3 Rigid bipolar configuration
A rigid bipolar HVDC system configuration is shown in Figure 5. With this scheme, operation is
limited to naturally balanced DC current, however, the installation cost can be reduced. In case
of outage of one pole line, the entire transmission capacity of the bipolar link is lost. In case of

outage of one converter pole, 50 % of the transmission capacity can be restored after
reconfiguration by DC switchgear for bypassing DC terminals of the failed converter bridge.

Figure 5 – Rigid bipolar VSC HVDC system
4.4.4 Bipolar HVDC with dedicated metallic return
The bipolar HVDC with dedicated metallic return (DMR) can be constructed with a third
conductor, as shown in Figure 6. This third conductor carries unbalanced currents during bipolar
operation. It also serves as the return path when one transmission line pole is out of service.
This third conductor needs only reduced voltage insulation.

Figure 6 – Bipolar HVDC system with dedicated metallic return
The neutral of one of the two HVDC substations can be earthed, while the neutral at the other
end of the transmission can float or be tied to its station earth through an arrester, a capacitor
or both.
4.5 Back-to-back HVDC system
The back-to-back (BtB)
...