CLC/TS 50654-2:2018

SLOVENSKI STANDARD
01-maj-2018
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HVDC Grid Systems and connected Converter Stations - Guideline and Parameter Lists
for Functional Specifications - Part 2: Parameter Lists
Ta slovenski standard je istoveten z: CLC/TS 50654-2:2018
ICS:
29.240.01 2PUHåMD]DSUHQRVLQ Power transmission and
GLVWULEXFLMRHOHNWULþQHHQHUJLMH distribution networks in
QDVSORãQR general
2003-01.Slovenski inštitut za standardizacijo. Razmnoževanje celote ali delov tega standarda ni dovoljeno.

TECHNICAL SPECIFICATION CLC/TS 50654-2

SPÉCIFICATION TECHNIQUE
TECHNISCHE SPEZIFIKATION
March 2018
ICS 29.240.01
English Version
HVDC Grid Systems and connected Converter Stations -
Guideline and Parameter Lists for Functional Specifications -
Part 2: Parameter Lists
Réseaux CCHT et stations de conversion connectées - Hochspannungsgleichstrom-Netzsysteme - Leitfaden und
Lignes directrices et listes de paramètres pour les Parameter-Listen für funktionale Spezifikationen - Teil 2:
spécifications fonctionnelles - Partie 2: Listes de Parameter-Listen
paramètres
This Technical Specification was approved by CENELEC on 2018-01-22.

CENELEC members are required to announce the existence of this TS in the same way as for an EN and to make the TS available promptly
at national level in an appropriate form. It is permissible to keep conflicting national standards in force.

CENELEC members are the national electrotechnical committees of Austria, Belgium, Bulgaria, Croatia, Cyprus, the Czech Republic,
Denmark, Estonia, Finland, Former Yugoslav Republic of Macedonia, France, Germany, Greece, Hungary, Iceland, Ireland, Italy, Latvia,
Lithuania, Luxembourg, Malta, the Netherlands, Norway, Poland, Portugal, Romania, Serbia, Slovakia, Slovenia, Spain, Sweden,
Switzerland, Turkey and the United Kingdom.

European Committee for Electrotechnical Standardization
Comité Européen de Normalisation Electrotechnique
Europäisches Komitee für Elektrotechnische Normung
CEN-CENELEC Management Centre: Rue de la Science 23, B-1040 Brussels
© 2018 CENELEC All rights of exploitation in any form and by any means reserved worldwide for CENELEC Members.
Ref. No. CLC/TS 50654-2:2018 E

Contents Page
European foreword . 5
Introduction . 6
1 Scope . 7
1.1 General . 7
1.2 About the present release . 7
2 Normative references . 7
3 Terms, definitions and abbreviations . 8
3.1 Terms and definitions . 8
3.2 Abbreviations . 10
4 Coordination of HVDC Grid System and AC Systems . 11
4.1 Purpose of the HVDC Grid System and Power Network Diagram . 11
4.2 Hybrid AC/DC Power Flow Optimization . 12
4.3 Basic Operation Functions – Converter Normal Operation State . 14
4.3.1 General. 14
4.3.2 AC System Frequency by a Frequency / Power Droop . 15
4.3.3 DC Voltage / DC Power Droop . 15
4.4 Basic Operation Functions – Converter Abnormal Operation State . 15
4.4.1 General. 15
4.4.2 Network Conditions and Power Flow Requirements . 16
4.4.3 Abnormal AC Voltage Conditions . 16
4.5 Ancillary Services . 18
4.5.1 General. 18
4.5.2 Frequency Control Related Services . 18
4.5.3 AC Voltage Control Related Services . 20
4.5.4 Power Oscillation Damping Services . 20
4.5.5 System Restoration Services . 20
5 HVDC Grid System Characteristics . 21
5.1 HVDC Circuit Topologies . 21
5.1.1 Basic Characteristics and Nomenclature . 21
5.1.2 Attributes of HVDC Grid Systems or HVDC Grid Sub-Systems . 21
5.1.3 Attributes of a Converter Station . 21
5.2 Grid Operating States . 22
5.2.1 Normal State . 22
5.2.2 Alert State . 22
5.2.3 Emergency State . 22
5.2.4 Blackout State . 23
5.2.5 Restoration . 23
5.3 DC Voltages . 23
5.3.1 General. 23
5.3.2 Nominal DC System Voltage . 24
5.3.3 Steady-State DC Voltage . 24
5.3.4 Temporary DC Voltage . 24
5.4 Insulation Coordination . 25
5.5 Short-Circuit Characteristics . 25
5.5.1 General Remarks . 25
5.5.2 Calculation of Short-Circuit Currents in HVDC Grid Systems. 25
5.5.3 Short Circuit Current Design Requirements. 27
5.6 Steady-State Voltage and Current Distortions . 27
6 HVDC Grid System Control . 27
6.1 Closed-Loop Control Functions . 27
6.1.1 General. 27
6.1.2 Core Control Functions . 27
6.1.3 Coordinating Control Functions . 28
6.2 Controller Hierarchy . 28
6.2.1 General. 28
6.2.2 Internal Converter Control . 28
6.2.3 DC Node Voltage Control. 28
6.2.4 Coordinated System Control . 28
6.2.5 AC/DC Grid Control . 30
6.3 Propagation of Information . 31
6.4 Open-Loop Controls . 34
6.4.1 Operating Sequences for Grid Installations . 34
6.4.2 Operating Sequences for the Return Path . 35
6.4.3 Recovery . 35
7 HVDC Grid System Protection . 36
7.1 General . 36
7.2 DC Fault Separation . 36
7.3 Protection System Related Installations and Equipment . 36
7.3.1 AC/DC Converter Station . 36
7.3.2 HVDC Grid System Topology and Equipment . 36
7.4 HVDC Grid System Protection Zones . 36
7.4.1 General. 36
7.4.2 Permanent Stop P . 38
7.4.3 Permanent Stop PQ . 38
7.4.4 Temporary Stop P . 39
7.4.5 Temporary Stop PQ . 39
7.4.6 Continued Operation . 39
7.4.7 Example of a Protection Zone Matrix . 39
7.5 DC Protection . 39
7.5.1 General. 39
7.5.2 DC Converter Protections . 40
7.5.3 HVDC Grid System Protections . 40
7.5.4 HVDC Hub Respective HVDC Node Protections . 40
7.5.5 DC Grid Protection Communication . 40
8 AC/DC Converter Stations . 40
8.1 General . 40
8.2 AC/DC Converter Station Types . 40
9 HVDC Grid System Installations . 40
10 Models and Validation . 40
10.1 Introduction . 40
10.2 HVDC Grid System Studies . 40
10.2.1 Type of Studies . 40
10.2.2 Tools and Methods . 41
10.3 Model General Specifications . 41
10.3.1 Model Capability . 41
10.3.2 Model Format and Data Type . 41
10.3.3 Model Aggregation . 41
10.4 Model Specific Recommendations . 42
10.4.1 Load Flow Models . 42
10.4.2 Short-Circuit Models . 42
10.4.3 Protection System Models . 42
10.4.4 Insulation Coordination Related Models . 42
10.4.5 Electromechanical Transient Models . 43
10.4.6 Electromagnetic Transient Models . 44
10.4.7 Power Quality Models . 49
10.5 Model Validation . 50
10.6 Compliance Simulation . 51
10.7 Outputs/Results . 51
10.7.1 Model Data . 51
10.7.2 Model Documentation . 51
10.7.3 Model Example . 51
10.7.4 Model Compliance Documentation . 51
10.7.5 Model Validation Documentation – Model Final Version . 51
10.7.6 Model Guarantee . 51
11 HVDC Grid System Integration Tests . 51
Bibliography . 52

European foreword
This document (CLC/TS 50654-2:2018) has been prepared by CLC/TC8X/WG 06 “System Aspects of
HVDC Grid”.
Attention is drawn to the possibility that some of the elements of this document may be the subject of
patent rights. CENELEC shall not be held responsible for identifying any or all such patent rights.
Introduction
HVDC Grid Systems are a new field of technology. There are very few systems with a small number of
converter stations in operation; some more are in execution or in detailed planning.
The Guidelines and Parameter Lists to Functional Specifications are presented featuring planning,
specification and execution of multi-vendor HVDC Grid Systems in Europe. Being elaborated by a team of
experts from leading manufacturers of HVDC technology, Transmission System Operators (TSO's),
Academia and Institutions in Europe, the present document provides a commonly agreed basis for an
open market of compatible equipment and solutions for HVDC Grid Systems. Executing such systems
and gaining operational experience is seen an important prerequisite for developing corresponding
technical standards in the future.
By elaborating 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. The physical phenomena
are categorized in order to show the mutual dependence of the individual parameters and ensure
completeness of the physical aspects to be considered. Based on a clearly defined common language
describing the functionalities requested, existing technologies can be applied or new dedicated technical
solutions can be developed.
Reflecting the early stage of technology, these Guidelines and Parameter Lists to Functional
Specifications need comprehensive explanations and background information for the technical
parameters. This dual character of the content will be represented by two corresponding parts:
• Part I “Guidelines” containing the explanations and the background information in context with the
Parameter Lists.
• Part II “Parameter Lists” containing the essential lists of parameters and values describing properties
of the a.c. respectively d.c. system (operating conditions) and parameters describing the
performance of the newly installed component (performance requirements).
1 Scope
1.1 General
These Guidelines and Parameter Lists to Functional Specifications describe specific functional
requirements for HVDC Grid Systems. The terminology “HVDC Grid Systems” is used here describing
HVDC systems for power transmission having more than two converter stations connected to a common
d.c. circuit.
While this document focuses on requirements, that are specific for HVDC Grid Systems, some
requirements are considered applicable to all HVDC systems in general, i.e. including point-to-point
HVDC systems. Existing IEC, Cigré or other documents relevant 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. .only nominal d.c. voltages equal or higher than 50 kV with respect to earth are considered
in this document.
NOTE While the physical principles of d.c. networks are basically voltage independent, the technical options for
designing equipment get much wider with lower d.c. voltage levels, e.g. in case of converters or switchgear.
Both parts have the same outline and headlines to aid the reader.
1.2 About the present release
The present release of the Guidelines and Parameter Lists for Functional Specifications describes
technical guidelines and specifications for HVDC Grid Systems which are characterized by having exactly
one single connection between two converter stations, often referred to as radial systems. When
developing the requirements for radial systems, care is taken not to build up potential show-stoppers for
meshed systems. Meshed HVDC Grid Systems can be included into this specification at a later point in
time.
The Guidelines and Parameter List to the Functional Specification of HVDC Grid Systems cover technical
aspects of
• Coordination of HVDC Grid and a.c. Systems
• HVDC Grid System Characteristics
• HVDC Grid System Control
• HVDC Grid System Protection
• Models and Validation
• Beyond the present scope, the following aspects are proposed for future work:
• AC/DC converter stations
• HVDC Grid System Equipment
• HVDC Grid System Integration Tests
2 Normative references
The following documents, in whole or in part, are normatively referenced in this document and are
indispensable for its application. For dated references, only the edition cited applies. For undated
references, the latest edition of the referenced document (including any amendments) applies.
EN 62747:2014, Terminology for voltage-sourced converters (VSC) for high-voltage direct current
(HVDC) systems (IEC 62747:2014)
EN 61660-1:1997, Short-circuit currents in d.c. auxiliary installations in power plants and substations —
Part 1: Calculation of short-circuit currents (IEC 61660-1:1997)
3 Terms, definitions and abbreviations
3.1 Terms and definitions
For the purposes of this document, the following terms and definitions 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
3.1.1
AC/DC converter unit
indivisible operative unit comprising all equipment between the point of connection on the a.c. side and
the point of connection on the d.c. side, essentially one or more converters, together with converter
transformers, control equipment, essential protective and switching devices and auxiliaries, if any, used
for conversion
[SOURCE: EN 62747:2014, modified – The definition was neutralised with respect to technology (not only
VSC converters) and uses the terms PoC as defined in the present document]
3.1.2
AC/DC converter station
part of an HVDC system which consists of one or more AC/DC converter units including d.c. switchgear,
d.c. 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
[SOURCE: EN 62747:2014, modified – The definition was made specific with respect to AC/DC converter
units, differentiating from DC/DC converter units. Furthermore, only the term AC/DC converter station is
used in the present document]
3.1.3
Point of connection-DC (PoC-DC)
electrical interface point at d.c. voltage
3.1.4
Point of connection-AC (PoC-AC)
electrical interface point at a.c. voltage
AC/DC converter
station
a.c. side d.c. side
point of connection point of connection HVDC grid
(PoC-AC) (PoC-DC) system
Figure 1 — Definition of the Point Of Connection-AC and the Point Of Connection-DC at an AC/DC
converter station
3.1.5
DC/DC converter unit
indivisible operative unit comprising all equipment between the points of connection to the HVDC Grid
System, essentially one or more converters, together with converter transformers, if any, control
equipment, essential protective and switching devices and auxiliaries, if any, used for conversion
3.1.6
DC/DC converter station
part of an HVDC Grid System which consists of one or more DC/DC converter units including d.c.
switchgear, d.c. fault current controlling devices, if any, installed in a single location together with
buildings, reactors, filters, control, monitoring, protective, measuring and auxiliary equipment
3.1.7
HVDC Grid System
high voltage direct current transmission network connecting more than two AC/DC converter stations
transferring energy in the form of high-voltage direct current including related transmission lines,
switching stations, DC/DC converter stations, if any, as well as other equipment and sub-systems needed
for operation
3.1.8
meshed HVDC Grid System
HVDC Grid System having more than one direct current connection between at least two converter
stations
3.1.9
DC protection zone
physical part of a HVDC Grid System with a common response to d.c. faults
3.1.10
radial HVDC Grid System
HVDC Grid System having exactly one direct current connection between two arbitrary converter stations
3.1.11
rigid bipolar (HVDC) system
bipolar (HVDC) system without Dedicated Return Path or electrodes as illustrated in Figure 2
Note 1 to entry: Monopolar operation is possible by means of bypass switches during a converter pole outage, but
not during an HVDC conductor outage. A short bipolar outage will follow a converter pole outage before bypass
operation can be established.
[SOURCE: IEEE P1899]
Pole
DC Line or Cable
~   ~
= =
~
~
DC Line or Cable
= =
Pole
Figure 2 — Rigid Bipolar HVDC system
3.2 Abbreviations
AC/DC alternating current / direct current (conversion)
DC/DC direct current / direct current (conversion)
DPT dynamic performance tests
ENTSO-E European Network of Transmission System Operators for Electricity
FAT factory acceptance tests
FCR frequency containment reserve
FRR frequency restoration reserve
GOOSE generic object-oriented substation events
HSS high-speed switches
HV high voltage
HVDC high-voltage direct current
IEEE Institute of Electrical and Electronics Engineers
LAT laboratory acceptance test
LVRT low-voltage ride through
MMC modular multilevel converter
NC Network Code
OHL overhead line
OP operating point
OPF optimum power flow
OVRT over-voltage ride through
PoC-AC point of connection on a.c. side
PoC-DC point of connection on d.c. side
POD power oscillation damping
STATCOM static synchronous compensator
THD total harmonic distortion
TSO transmission system operator
UVRT under-voltage ride through
VSC voltage-sourced converter
4 Coordination of HVDC Grid System and AC Systems
4.1 Purpose of the HVDC Grid System and Power Network Diagram
The following information shall be provided
• HVDC Transmission System, d.c. lines
• HVDC Grid System topology and converter station topology for each AC/DC converter station as well
as each DC/DC converter station according to the nomenclature given in Table 1. In case of an
isolated HVDC Grid System, the number of series connected converter units between poles (one or
two) shall be specified
• DC earthing impedances at each AC/DC converter station and DC/DC converter station
• HVDC switchyard
• Surge Arresters
• DC breakers
o Mechanical HVDC breakers
o Semiconductor based HVDC breakers (breaking device is a semiconductor, e.g. IGBT valve)
o Hybrid HVDC breakers (combination of mechanical and semiconductor breaking device)
• Disconnecting switches
o High speed switches (HSS), i.e. mechanical breakers
o Disconnectors and earthing switches
• DC/DC Converter Station
o With d.c. fault current breaking capability
o Without d.c. fault current breaking capability
• Measurement equipment
• Transition between a cable and d.c. overhead line, i.e. d.c. transition station.
Table 1 — Nomenclature of HVDC circuit topologies
(Please refer to CLC/TS 50654-1:2018, 5.1, for details of the nomenclature)
Characteristics of the HVDC Grid System - Characteristics of a converter station
Number of DC d.c. earthing - connection neutral return path station earthing
HV poles to pole
1 DC “z” isolated - “1” pole 1 “O” none “O” none
2 “e” effectively earthed “2” pole 2 “R” return “Z” impedance
conductor
“B” both “E” direct
“E” earth or sea
electrode
4.2 Hybrid AC/DC Power Flow Optimization
To provide a basis for the AC/DC power flow optimization the purpose and the operational strategy of the
hybrid AC/DC system needs to be described. The objectives of the optimization are to be expressed by
objective functions and boundary conditions.
The interface points between the HVDC grid and a.c. systems are the Points of Connection (PoC-AC or
PoC-DC respectively).
The parameters needed to perform a power flow calculation for hybrid a.c. and d.c. system both in normal
or in abnormal operating state are listed in the following table.
Table 2 — Parameters for a.c. and d.c. static power flow calculation
Symbol Parameter Characteristic Value Unit

U  maximum steady-state voltage at  kV
XACmax_ss
each station defined at the PoC-
AC, a station being identified by
X = A, B, …Z
U  minimum steady-state voltage at  kV
XACmin_ss
each station defined at the PoC-
AC, a station being identified by
X = A, B, …Z
P maximum active maximum steady-state active  MW
XACmax_ss
power power exchange between a.c. and
d.c. network at each station defined
at the PoC-AC, a station being
identified by X = A, B, …Z
P minimum active minimum steady-state active power  MW
XACmin_ss
power exchange between a.c. and d.c.
network at each station defined at
the PoC-AC, a station being
identified by X = A, B, …Z
Instead of P , the rated active power P may be defined at the PoC-DC.
XACmax_ss XDCmax_ss
Instead of PXACmin_ss, the rated active power PXDCmin_ss may be defined at the PoC-DC.
Symbol Parameter Characteristic Value Unit
P maximum active maximum temporary active power  MW
XACmax_temp
power exchange between a.c. and d.c.
network at each station defined at
the PoC-AC, a station being
identified by X = A, B, …Z
P minimum active minimum temporary active power  MW
XACmin_temp
power exchange between a.c. and d.c.
network at each station defined at
the PoC-AC, a station being
identified by X = A, B, …Z
t time time, for which limits of temporary  s
XP_ACtemp
maximum and minimum active
power apply
P power losses of power losses function of each  MW
Xloss_rat
station X station, a station being identified by
X = A, B, …Z
Q ( ) maximum reactive maximum steady-state reactive  Mvar
Xmax .
power power exchange capability chart
(inductive and capacitive)
depending on active power and
voltage (P ,U ) at the PoC-
XAC XAC
AC of each station, a station being
identified by X = A, B, …Z
Q (.) minimum reactive minimum steady-state reactive  Mvar
Xmin
power power exchange capability chart
(inductive and capacitive)
depending on active power and
voltage (P ,U ) at the PoC-
XAC XAC
AC of each station, a station being
identified by X = A, B, …Z
Q ( ) maximum reactive maximum temporary reactive power  Mvar
Xmax .
power exchange capability chart (inductive
and capacitive) depending on
active power and voltage
(P ,U ) at the PoC-AC of
XAC XAC
each station, a station being
identified by X = A, B, …Z
Instead of PXACmax_temp, the rated active power PXDCmax_temp may be defined at the PoC-DC.
Instead of P , the rated active power P may be defined at the PoC-DC.
XACmin_temp XDCmin_temp
Instead of PXloss_rat, power losses PXloss_OP at various operating points OP may be given.
Symbol Parameter Characteristic Value Unit
Q (.) minimum reactive minimum temporary reactive power  Mvar
Xmin
power exchange capability chart (inductive
and capacitive) depending on
active power and voltage
(P ,U ) at the PoC-AC of
XAC XAC
each station, a station being
identified by X = A, B, …Z
t time time, for which limits of temporary  s
XQ_ACtemp
maximum and minimum reactive
power apply
I ampacity ampacity of each d.c. line, identified  kA
XYDC_Lrat
by its terminating stations X,Y = A,
B, …Z
control Mode please refer to chapter 6  N/A
control Mode please refer to chapter 6  various
Parameters
G d.c. conductance   [G ] = S
DC i,j
matrix including
the dedicated
metallic return
conductors,
electrode lines
and earthing
impedances, if
any
U d.c. voltage band   [U ] = kV
DC i
vector
Z a.c. impedance ….  [Z ] = Ω
AC i,j
matrix
B a.c. conductance   [B ] = S
AC i,j
matrix
Y a.c. admittance   [Y ] = S
AC i,j
matrix
I a.c. line ampacity   [I ] = A
AC_Lrat i
vector
4.3 Basic Operation Functions – Converter Normal Operation State
4.3.1 General
No parameters necessary
A matrix can also be provided as network diagram including parameters.
4.3.2 AC System Frequency by a Frequency / Power Droop
Table 3 — Parameter list for basic operation functions
Symbol Parameter Characteristic Value Unit
P rated active rated active power exchange  MW
XACrat
power between a.c. and d.c. network at
each station defined at the POC on
the a.c. side, a station being
identified by X = A, B, …Z
s a.c. frequency / defines the droop constant for the  N/A
PF
active power converter control regarding the
droop change of the active power
reference with respect to the a.c.
system frequency
4.3.3 DC Voltage / DC Power Droop
Table 4 — Parameter list for basic operation functions
Symbol Parameter Characteristic Value Unit
U d.c. voltage rated d.c. voltage at each station  kV
XDCrat
defined at the PoC-DC, a station
being identified by X = A, B, … Z
s d.c. voltage / defines the change of active power  N/A
P_UDC
reference in response to a deviation
d.c. power droop
of the d.c. voltage from its
reference value
s d.c. voltage / defines the change of d.c. current  N/A
IDC_UDC
reference in response to a deviation
d.c. current droop
of the d.c. voltage from its
reference value.
4.4 Basic Operation Functions – Converter Abnormal Operation State
4.4.1 General
No parameters necessary
Instead of PXACrat, the nominal active power PXDCrat may be defined at the PoC on the DC side
4.4.2 Network Conditions and Power Flow Requirements
Table 5 — Parameters describing the operation conditions of the a.c. network prior and after a
fault
Symbol Parameter Characteristic Value Unit
I minimum short minimum steady-state short circuit  kA
XSCmin_pre
circuit current current level the PoC-AC of a
station prior to a fault, a station
being identified by X = A, B, …Z
I minimum short minimum steady-state short circuit kA
XSCmin_post
circuit current current level the PoC-AC of a

station after a fault, a station being
identified by X = A, B, …Z
I maximum short maximum steady-state short circuit  kA
XSCmax
circuit current current level the PoC-AC of a
station, a station being identified by
X = A, B, …Z
X/R maximum value of   N/A
max
the X/R ratio
I “ maximum short maximum subtransient short circuit  kA
XSCmax
circuit current current level the PoC-AC of a
station, a station being identified by
X = A, B, …Z
Table 6 — Time requirements for power restoration in case of temporary faults
Symbol Parameter Characteristic Value Unit
T maximum time of interruption time due to a.c. system  ms
XPoffAC
active power faults, counted from fault inception
interruption until restoration of active power to
90 % of its target value at a
converter station, a station being
identified by X = A, B, …Z
T maximum time of interruption time due to a.c. system  ms
XQoffAC
reactive power faults, counted from fault inception
interruption until restoration of reactive power to
90 % of its target value at a
converter station, a station being
identified by X = A, B, …Z
T maximum time of interruption time due to d.c. system  ms
XPoffDC
active power faults, counted from fault inception
interruption until restoration of active power to
90 % of its target value at a
converter station, a station being
identified by X = A, B, …Z
T maximum time of interruption time due to d.c. system  ms
XQoffDC
reactive power faults, counted from fault inception
interruption until restoration of reactive power to
90 % of its target value at a
converter station, a station being
identified by X = A, B, …Z
4.4.3 Abnormal AC Voltage Conditions
The a.c. under voltage ride through requirements shall be specified by a diagram as shown in Figure 3
using the parameters listed below.
Table 7 — AC Under Voltage Ride Through Requirements
(piecewise linear definition of the voltage versus time curve)
Symbol Parameter Characteristic Value Unit
U voltage level voltage level defining the retained  kVrms
XAC_UVt
a.c. under voltage during a fault at
the PoC-AC of a station at the time
defined by t , a station
XAC_UVt
being identified by X = A, B, …Z
t time time defining the maximum duration s
XAC_UVt
of the voltage level U
XAC_UVt
The following additional information is relevant:
• Table 2, Parameters for a.c. and d.c. static power flow calculation; U
XACmin_ss
The a.c. over voltage ride through requirements shall be specified by a diagram as shown in Figure 3
using the parameters listed below.
Table 8 — AC Over Voltage Ride Through Requirements
(piecewise definition of the voltage versus time curve)
Symbol Parameter Characteristic Value Unit
U voltage level voltage level defining one  kVrms
XAC_OVt
supporting point of the a.c. over
voltage at the PoC-AC of a station
at the time defined by t , a
XAC_OVt
station being identified by X = A, B,
…Z
t time time defining the maximum duration s
XAC_OVt
of the voltage level U
XAC_OVt
The following additional information is relevant:
• Table 2, Parameters for a.c. and d.c. static power flow calculation; U
XACmax_ss
t
t t t t
AC_OV0
AC_OV1 AC_OV2 AC_OV3 AC_OV(i) t(s)
U
AC_OV1
U
AC_OV2
U
AC_OV3
U
AC_OV(i)
U
ACmax_ss
U
ACmin_ss
U
AC_UV2
U
AC_UV1
t t
t t
AC_UV1 AC_UV3 t(s)
AC_UV0 AC_UV2
Figure 3 — Exemplary generic AC Over- and Under Voltage Ride Through profile of a HVDC
converter station
4.5 Ancillary Services
4.5.1 General
No parameters necessary
4.5.2 Frequency Control Related Services
4.5.2.1 Synthetic Inertia (Differential Frequency Control)
The coordination of power associated with primary frequency control shall be specified by the required
variation of the output power, which is calculated by:

Table 9 — Coordination of power associated with primary frequency control
Symbol Parameter Characteristic Value Unit
time minimum step response time, to  s
tFCRact
coordinate with inertia
time maximum provision time, to  s
tFCRprov
coordinate with Frequency
Restoration Reserve (FRR)
frequency band frequency dead band, to limit the  s
f
DEADBAND
activation to exceptional situations
K coefficient Frequency Containment Reserve  N/A
FCR,i,j
(FCR)-distribution coefficient
indicating the amount of active
power drawn from the sending zone
j and fed into the receiving zone i
ΔP active power active power fed into receiving zone
...