IEC TS 63291-2:2023

High voltage direct current (HVDC) grid systems and connected converter stations - Guideline and parameter lists for functional specifications - Part 2: Parameter lists

IEC TS 63291-2:2023 defines aspects on planning, specification, and execution of multi-vendor HVDC grid systems also referred to as HVDC grids. The terms "HVDC grid systems" or "HVDC grids" are used in this document to describe HVDC systems for power transmission having more than two HVDC stations connected to a common DC circuit. The DC circuit can be of radial or meshed topology or a combination thereof. In this document, the term "HVDC grids" is used.
While this document focuses on requirements specific for HVDC grids, some requirements are considered applicable to all HVDC systems in general, i.e., including point-to-point HVDC systems. Existing IEC (e.g., IEC TR 63363-1 [1]), Cigre or other relevant documents have been used for reference as far as possible.
Corresponding to electric power transmission applications, this document is applicable to high voltage systems, i.e., those having typically nominal DC voltages higher than 50 kV with respect to earth are considered in this document.
NOTE While the physical principles of DC networks are basically voltage independent, the technical options for designing equipment get much wider with lower DC voltage levels, e.g. in the case of converters or switchgear.
This document covers technical aspects of:
- coordination of HVDC grid and AC systems,
- HVDC grid characteristics,
- HVDC grid control,
- HVDC grid protection,
- AC/DC converter stations,
- HVDC grid installations, including DC switching stations and HVDC transmission lines,
- studies and associated models,
- testing.
Beyond the scope of this document, the following content is proposed for future work:
DC/DC converter stations.

General Information

• Status: Published
• Publication Date: 28-Sep-2023
• ICS: 29.200 - Rectifiers. Convertors. Stabilized power supply
• ICS: 29.240.01 - Power transmission and distribution networks in general
• Technical Committee: TC 115 - High Voltage Direct Current (HVDC) transmission for DC voltages above 100 kV
• Drafting Committee: WG 15 - TC 115/WG 15
• Current Stage: PPUB - Publication issued
• Start Date: 29-Sep-2023
• Completion Date: 18-Jul-2023

Overview

IEC TS 63291-2:2023 provides parameter lists and guidance for functional specifications of multi‑vendor high voltage direct current (HVDC) grid systems and their connected converter stations. Part 2 focuses on the parameter lists needed for planning, specifying and executing HVDC grids - systems with more than two HVDC stations on a common DC circuit (radial, meshed or hybrid topologies). The technical specification applies mainly to high‑voltage DC systems (typically nominal DC voltages > 50 kV) and complements other IEC and Cigré guidance for HVDC and point‑to‑point links.

Key topics and technical requirements

The document organizes parameters and requirements across the full HVDC grid lifecycle, including:

• HVDC grid characteristics
  • Circuit topologies (radial/meshed), availability and reliability attributes
  • Nominal and temporary DC voltages, insulation coordination and short‑circuit characteristics
• Coordination of HVDC and AC systems
  • AC/DC power flow optimisation, converter operational modes and ancillary services
• HVDC grid control
  • Core closed‑loop controls, controller hierarchy (internal converter, DC node, coordinated grid control), open‑loop sequences and propagation of information
• HVDC grid protection
  • Fault separation strategies, protection zones, DC protection functions and communication requirements
• AC/DC converter stations
  • Station types, main‑circuit design considerations, control interfaces, dynamic behavior and protection configuration
• HVDC installations
  • DC switching stations, transmission line requirements, installation controls and protection
• Studies, models and testing
  • Planning/design/extension studies, model requirements for interoperability and testing

The specification also identifies topics proposed for future work (e.g., DC/DC converter stations) and references other IEC/Cigré documents where applicable.

Practical applications and users

IEC TS 63291-2:2023 is intended for professionals involved in design, procurement, integration and operation of HVDC grids, including:

• Utility planners and transmission system operators (TSOs)
• OEMs and multi‑vendor integrators of converters, switchgear and protection systems
• Protection and control engineers specifying functional performance and interoperability
• Consultants performing HVDC grid studies, modelling and testing
• Regulators and standards committees defining compliance and interface requirements

Practical uses include preparing functional specifications, defining vendor interoperability parameters, coordinating AC/DC interfaces, designing protection schemes, and ensuring consistent testing and commissioning practices.

Related standards

• IEC TS 63291-1 (guideline context)
• IEC TR 63363‑1 and relevant Cigré reports (referenced for background on HVDC technology)

Keywords: IEC TS 63291-2:2023, HVDC grid, parameter lists, HVDC control, HVDC protection, converter stations, DC switching station, HVDC transmission lines, functional specifications.

Standards Content (Sample)

IEC TS 63291-2 ®
Edition 1.0 2023-09
TECHNICAL
SPECIFICATION
colour
inside
High voltage direct current (HVDC) grid systems and connected converter
stations – Guideline and parameter lists for functional specifications –
Part 2: Parameter lists
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IEC TS 63291-2 ®
Edition 1.0 2023-09
TECHNICAL
SPECIFICATION
colour
inside
High voltage direct current (HVDC) grid systems and connected converter

stations – Guideline and parameter lists for functional specifications –

Part 2: Parameter lists
INTERNATIONAL
ELECTROTECHNICAL
COMMISSION
ICS 29.200; 29.240.01 ISBN 978-2-8322-7572-6

– 2 – IEC TS 63291-2:2023 © IEC 2023
CONTENTS
FOREWORD . 9
INTRODUCTION . 11
1 Scope . 12
2 Normative references . 12
3 Terms, definitions and abbreviated terms . 13
3.1 Terms and definitions . 13
3.2 Abbreviated terms . 17
4 Coordination of HVDC grid and AC systems . 18
4.1 About HVDC grids . 18
4.2 HVDC grid structure . 18
4.3 Purpose of the HVDC grid and power network diagram . 18
4.4 AC/DC power flow optimisation . 19
4.5 Converter operational functions . 21
4.5.1 Basic operation functions – Converter normal operation state . 21
4.5.2 Basic operation functions – Converter abnormal operation state . 22
4.5.3 Ancillary services . 24
5 HVDC grid characteristics . 28
5.1 HVDC circuit topologies . 28
5.1.1 Availability and reliability . 28
5.1.2 Basic characteristics and nomenclature . 28
5.1.3 Attributes of HVDC grids or HVDC grid subsystems . 29
5.1.4 Attributes of an HVDC station . 29
5.2 Connection modes . 30
5.3 Grid operating states . 30
5.3.1 General . 30
5.3.2 Normal state . 30
5.3.3 Alert state . 30
5.3.4 Emergency state . 30
5.3.5 Blackout state . 30
5.3.6 Restoration . 30
5.4 DC voltages . 31
5.4.1 General . 31
5.4.2 Nominal DC system voltage . 32
5.4.3 Steady-state DC pole voltage . 32
5.4.4 Temporary DC pole voltage . 32
5.4.5 DC neutral bus voltage . 33
5.5 Insulation coordination . 35
5.6 Short-circuit characteristics . 35
5.6.1 Calculation of short-circuit currents in HVDC grids . 35
5.6.2 Short-circuit current design requirements . 37
5.7 Steady-state voltage and current distortions . 37
5.7.1 Emissions and impacts . 37
5.7.2 Rights and obligations of a connectee . 39
5.7.3 Similarities between HVDC grids and AC networks . 39
5.7.4 Voltage and current distortion limits . 39
5.7.5 Allocation of limits to individual connectees . 39

5.7.6 Frequency-dependent DC system impedance . 39
5.8 DC system restoration. 39
5.8.1 General . 39
5.8.2 Post-DC fault recovery . 40
5.8.3 Restoration from blackout . 40
6 HVDC grid control . 40
6.1 Closed-loop control functions . 40
6.1.1 General . 40
6.1.2 Core control functions . 40
6.1.3 Coordinating control functions . 40
6.2 Controller hierarchy . 40
6.2.1 General . 40
6.2.2 Internal converter control . 40
6.2.3 DC node voltage control . 40
6.2.4 Coordinated HVDC grid control . 41
6.2.5 AC/DC grid control . 44
6.3 Propagation of information . 44
6.4 Open-loop controls. 48
6.4.1 Coordination of connection modes between HVDC stations and their
PoC-DC . 48
6.4.2 Operating sequences for HVDC grid installations . 48
6.4.3 Post-DC fault recovery . 49
7 HVDC grid protection . 49
7.1 General . 49
7.2 DC fault separation . 49
7.3 Protection system related installations and equipment . 50
7.3.1 AC/DC converter station . 50
7.3.2 HVDC grid topology and equipment . 50
7.4 HVDC grid protection zones . 50
7.4.1 General . 50
7.4.2 Permanent stop P . 53
7.4.3 Permanent stop PQ . 54
7.4.4 Temporary stop P . 54
7.4.5 Temporary stop PQ . 54
7.4.6 Continued operation . 54
7.4.7 Example of a protection zone matrix . 54
7.5 DC protection . 55
7.5.1 General . 55
7.5.2 DC converter protections . 55
7.5.3 HVDC grid protections . 55
7.5.4 HVDC grid protection communication . 55
8 AC/DC converter stations . 55
8.1 Purpose . 55
8.2 AC/DC converter station types . 55
8.3 Overall requirements . 55
8.3.1 Robustness of AC/DC converter stations . 55
8.3.2 Availability and reliability . 56
8.3.3 Active power reversal . 56

– 4 – IEC TS 63291-2:2023 © IEC 2023
8.4 Main circuit design . 56
8.4.1 General characteristics . 56
8.4.2 DC side . 57
8.4.3 AC side. 62
8.5 HVDC grid control and protection interface . 62
8.6 Controls . 63
8.6.1 General . 63
8.6.2 Automated vs manual operation . 63
8.6.3 Control modes and support of coordination . 63
8.6.4 Limitation strategies . 64
8.6.5 Operating sequences for AC/DC converter station . 65
8.6.6 Dynamic behaviour . 65
8.7 Protection . 66
8.7.1 General . 66
8.7.2 Configuration requirements . 66
8.7.3 Function requirements . 66
8.7.4 Fault separation strategy for faults inside the AC/DC converter station . 66
8.7.5 Coordination of the DC protection with the HVDC grid . 66
8.7.6 Example for coordination of the DC protection with the HVDC grid . 66
9 HVDC grid installations . 66
9.1 General . 66
9.2 DC switching station . 66
9.2.1 Purpose . 66
9.2.2 Overall requirements . 67
9.2.3 Main circuit design . 67
9.2.4 HVDC grid control and protection interface . 74
9.2.5 Controls . 75
9.2.6 Protection . 78
9.3 HVDC transmission lines. 79
9.3.1 Purpose . 79
9.3.2 Overall requirements . 79
9.3.3 Main circuit design . 80
9.3.4 HVDC grid control and protection interface . 82
9.3.5 Controls . 83
9.3.6 Protection . 83
9.4 DC/DC converter stations . 83
10 Studies and associated models . 84
10.1 General . 84
10.2 Description of studies . 84
10.2.1 General . 84
10.2.2 HVDC grid planning studies . 84
10.2.3 HVDC grid design studies . 84
10.2.4 HVDC grid extension studies . 84
10.2.5 Studies for HVDC grid installation refurbishments and other
modifications . 84
10.3 Models and interfaces . 84
10.3.1 General . 84
10.3.2 Model interfaces and integration compatibility . 85
10.3.3 Model capability . 85

10.3.4 Model format . 85
10.3.5 Model maintenance and portability . 86
10.3.6 Model aggregation . 86
10.3.7 Model testing and validation . 86
11 Testing . 87
11.1 General . 87
11.2 Off-site testing . 88
11.2.1 General . 88
11.2.2 Factory system tests . 88
11.3 On-site testing . 88
Bibliography . 89

Figure 1 – Definition of the point of connection-AC and the point of connection-DC at
an AC/DC converter station . 14
Figure 2 – Rigid bipolar HVDC system . 16
Figure 3 – Generic AC over- and undervoltage ride through profile of an AC/DC
converter station: Different values can be specified for symmetrical and asymmetrical
faults . 24
Figure 4 – Temporary DC pole to earth voltage profiles at a PoC-DC . 31
Figure 5 – Generic neutral bus voltage profile at a PoC-DC . 34
Figure 6 – Standard approximation function . 37
Figure 7 – Typical DC node voltage control modes (illustration in DC voltage/power
plane) . 41
Figure 8 – Generation of final converter schedules including converter control modes
and its parameters . 45
Figure 9 – Propagation of switching commands to individual HVDC stations . 46
Figure 10 – Operating sequences as transitions between operating states . 48
Figure 11 – Example voltage and current traces in the event of "permanent stop" . 51
Figure 12 – Example voltage and current traces in the event of "temporary stop P" . 52
Figure 13 – Example voltage and current traces in the event of "continued operation" . 53

Table 1 – Nomenclature of HVDC circuit topologies . 19
Table 2 – Active and reactive power characteristics for a given AC system voltage
operating range of an AC/DC converter station . 19
Table 3 – Parameters of an HVDC transmission line . 21
Table 4 – Parameter list for AC system frequency following a frequency / power droop
operation of an AC/DC converter station . 21
Table 5 – Parameter list for DC voltage / DC power droop operation of an AC/DC
converter station . 22
Table 6 – Parameters describing the operation conditions of the AC network at an
AC/DC converter station prior to and after a fault . 22
Table 7 – Time requirements for power restoration in the event of temporary faults . 23
Table 8 – AC undervoltage ride through requirements for an AC/DC converter station . 23
Table 9 – AC overvoltage ride through requirements for an AC/DC converter station . 24
Table 10 – Coordination of power associated with primary frequency control . 25
Table 11 – FCR parameters for an AC/DC converter station, parameters for active
power frequency response in FSM . 26

– 6 – IEC TS 63291-2:2023 © IEC 2023
Table 12 – Voltage range capability parameters for an AC/DC converter station . 27
Table 13 – Reactive power capability parameters for an AC/DC converter station . 27
Table 14 – Parameters describing electromechanical oscillations . 27
Table 15 – Parameters describing post-fault active power recovery at an AC/DC
converter station . 28
Table 16 – Characteristics of the HVDC grid . 28
Table 17 – DC circuit earthing parameters . 29
Table 18 – Parameters for each return path . 30
Table 19 – Nominal DC system voltage at a PoC-DC . 32
Table 20 – DC pole voltage range parameters at a PoC-DC of an HVDC station –
Steady-state . 32
Table 21 – DC pole voltage range parameters at a PoC-DC of an HVDC station –
Temporary undervoltages . 32
Table 22 – DC pole voltage range parameters at a PoC-DC of an HVDC station –
Temporary overvoltages . 33
Table 23 – DC neutral bus voltage range parameters . 34
Table 24 – Insulation levels at a PoC-DC . 35
Table 25 – Maximum converter current of an HVDC station into the HVDC grid . 35
Table 26 – Component data – Earthing branch . 36
Table 27 – Component data – Standalone DC capacitors and DC filters of an HVDC
station . 36
Table 28 – Component data – DC line reactors of an HVDC station . 36
a
Table 29 – Component data – DC lines (OHL, cable including electrode lines) . 36
Table 30 – Short-circuit current parameters at a PoC-DC . 37
Table 31 – Equivalent impedances for calculating voltage and current distortions at a
PoC-DC . 38
Table 32 – Pre-existing DC voltage and current distortions at a PoC-DC. 38
Table 33 – Planning levels and permissible DC voltage and current distortions at a
PoC-DC . 38
Table 34 – Coupling factors for calculating voltage distortions at a remote bus caused
by emissions at a PoC-DC . 39
Table 35 – Specification of DC system impedance . 39
Table 36 – DC node voltage control parameters . 41
Table 37 – System state variables and equipment status signals (interface list) . 42
Table 38 – General interface (signal list) for autonomous adaption control rules . 42
Table 39 – General interface (signal list) for defining an observation . 43
Table 40 – General interface (signal list) for defining countermeasures of rules . 43
Table 41 – Interface parameters required from the HVDC grid control layer . 44
Table 42 – General interface (signal list) for orders from TSOs . 44
Table 43 – General interface (signal list) defining a "converter schedule" . 45
Table 44 – General interface (signal list) defining "switching commands" . 46
Table 45 – General signal interface (physical quantities) of the "station information" . 47
Table 46 – General signal interface (control parameters) of the "station information" . 48
Table 47 – Unified description of operating sequences . 49
Table 48 – Parameters for recovery sequences after DC line faults . 49

Table 49 – Example of an HVDC grid protection zone matrix . 50
Table 50 – DC protection parameter list . 50
Table 51 – DC converter protection parameter list . 55
Table 52 – Converter station topology . 56
Table 53 – Energy dissipation/absorption capability at a PoC . 57
Table 54 – DC connection modes of the AC/DC converter station . 58
Table 55 – DC circuit re-configuration time requirements . 58
Table 56 – Repetition of DC fault events and recovery attempts . 59
Table 57 – DC circuit energisation . 60
Table 58 – Connecting the AC/DC converter station . 60
Table 59 – Disconnecting the AC/DC converter station . 60
Table 60 – DC circuit de-energisation . 61
Table 61 – Parameters for the automatic control interface of the AC/DC converter
station according to standard protocols . 63
Table 62 – Parameters for the automatic control interface of the AC/DC converter

station according to proprietary protocols. 63
Table 63 – Parameters for the available control modes of the AC/DC converter station . 64
Table 64 – Limitation strategies . 65
Table 65 – Operating states and transitions for the AC/DC converter station . 65
Table 66 – Protection coordination of the AC/DC converter station and the HVDC grid
(for main and backup concept including the separation concept and the FSD) . 66
Table 67 – DC switching station topology . 67
Table 68 – Temporary energy dissipation/absorption capability of the DC switching
station . 68
Table 69 – Power flow controlling capability of a DC SU . 68
Table 70 – DC connection modes of a DC SU for PoC-DCx . 69
Table 71 – DC circuit re-configuration time requirements . 69
Table 72 – Repetition of DC fault events and recovery attempts . 71
Table 73 – DC circuit energisation . 72
Table 75 – Disconnecting the DC switching station . 72
Table 76 – DC circuit de-energisation . 73
Table 77 – Parameters for the automatic control interface of the DC switching station
according to standard protocols . 75
Table 78 – Parameters for the automatic control interface of the DC switching station
according to proprietary protocols . 75
Table 79 – Parameters for the available control modes of the DC switching station . 76
Table 80 – Limitation strategies . 77
Table 81 – Operating states and transitions for a SU of the DC switching station . 78
Table 82 – Protection coordination of the DC switching station and the HVDC grid (for
main and backup concept including the separation concept and the FSD) . 79
Table 83 – DC line power transmission parameters for the transmission line including

all different HVDC transmission line sections, if any. 80
Table 84 – Frequency range for specification of DC system impedance . 82
Table 85 – Parameters defining the model generalities . 84

– 8 – IEC TS 63291-2:2023 © IEC 2023
Table 86 – Parameters to characterize the model capability . 85
Table 87 – Parameters to define the model format . 85
Table 88 – Parameters defining the model aggregation . 86
Table 89 – Parameters defining the model validation . 86
Table 90 – Parameters for testing . 87
Table 91 – Minimum set of parameters to be defined for all test scenarios . 87

INTERNATIONAL ELECTROTECHNICAL COMMISSION
____________
HIGH VOLTAGE DIRECT CURRENT (HVDC) GRID SYSTEMS AND
CONNECTED CONVERTER STATIONS – GUIDELINE AND PARAMETER
LISTS FOR FUNCTIONAL SPECIFICATIONS –

Part 2: Parameter lists
FOREWORD
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rights. IEC shall not be held responsible for identifying any or all such patent rights.
IEC TS 63291-2 has been prepared by IEC technical committee TC 115: High Voltage Direct
Current (HVDC) transmission for DC voltages above 100 kV. It is a Technical Specification.
The text of this Technical Specification is based on the following documents:
Draft Report on voting
115/320/DTS 115/329/RVDTS
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 Specification is English.
This Technical Specification is to be used in conjunction with IEC TS 63291-1:2023.

– 10 – IEC TS 63291-2:2023 © IEC 2023
A list of all parts in the IEC 63291 series, published under the general title High voltage direct
current (HVDC) grid systems and connected converter stations – Guideline and parameter lists
for functional specifications, 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/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.

INTRODUCTION
In the preparation of this document, special care has been taken to as far as possible describe
the requirements in a technologically independent way. In order to achieve that, a function of
interest is described by a comprehensive set of parameters. The parameters are selected based
on a systematic analysis of physical phenomena relevant to achieve the requested functionality.
Reflecting the early stage of technology, the technical parameters need comprehensive
explanations and background information. This need is reflected in the dual character of the
content, which is presented in the two corresponding parts:
• IEC TS 63291-1, Guideline containing the explanations and the background information in
context with the parameter lists;
• IEC TS 63291-2, Parameter lists containing the essential lists of parameters and values
describing properties of the AC as well as the DC system (operating conditions) and
parameters describing the performance of the newly installed component (performance
requirements).
IEC TS 63291-1 and IEC TS 63291-2 have the same structure to aid the reader.
At the time of writing there is no real-life multi-national, multi-vendor HVDC grid project to which
the guideline and parameter lists can be applied. Practical experiences in the near future are
expected to provide input for developing these guideline and parameter lists further.

– 12 – IEC TS 63291-2:2023 © IEC 2023
HIGH VOLTAGE DIRECT CURRENT (HVDC) GRID SYSTEMS AND
CONNECTED CONVERTER STATIONS – GUIDELINE AND PARAMETER
LISTS FOR FUNCTIONAL SPECIFICATIONS –

Part 2: Parameter lists
1 Scope
This document defines aspects on planning, specification, and execution of multi-vendor HVDC
grid systems also referred to as HVDC grids. The terms "HVDC grid systems" or "HVDC grids"
are used in this document to describe HVDC systems for power transmission having more than
two HVDC stations connected to a common DC circuit. The DC circuit can be of radial or meshed
topology or a combination thereof. In this document, the term "HVDC grids" is used.
While this document focuses on requirements specific for HVDC grids, some requirements are
considered applicable to all HVDC systems in general, i.e., including point-to-point HVDC
systems. Existing IEC (e.g., IEC TR 63363-1 [1]), Cigre or other relevant documents have been
used for reference as far as possible.
Corresponding to electric power transmission applications, this document is applicable to high
voltage systems, i.e., those having typically nominal DC voltages higher than 50 kV with respect
to earth are considered in this document.
NOTE While the physical principles of DC networks are basically voltage independent, the technical options for
designing equipment get much wider with lower DC voltage levels, e.g. in the case of converters or switchgear.
This document covers technical aspects of:
• coordination of HVDC grid and AC systems,
• HVDC grid characteristics,
...