EN IEC 62933-2-1:2018

2003-01.Slovenski inštitut za standardizacijo. Razmnoževanje celote ali delov tega standarda ni dovoljeno.Systèmes de stockage d'énergie électrique - Partie 2-1 : Paramètres d'unité et méthodes d'essai - Spécification générale (IEC 62933-2-1:2017)Electrical energy storage (EES) systems - Part 2-1: Unit parameters and testing methods - General specification (IEC 62933-2-1:2017)27.010Prenos energije in toplote na splošnoEnergy and heat transfer engineering in generalICS:Ta slovenski standard je istoveten z:EN IEC 62933-2-1:2018SIST EN IEC 62933-2-1:2018en01-maj-2018SIST EN IEC 62933-2-1:2018SLOVENSKI
STANDARD
EUROPEAN STANDARD NORME EUROPÉENNE EUROPÄISCHE NORM
EN IEC 62933-2-1
March 2018 ICS 13.020.30
English Version
Electrical energy storage (EES) systems - Part 2-1: Unit parameters and testing methods - General specification (IEC 62933-2-1:2017)
Systèmes de stockage d'énergie électrique - Partie 2-1 : Paramètres d'unité et méthodes d'essai - Spécification générale (IEC 62933-2-1:2017)
Elektrische Energiespeichersysteme - Teil 2-1: Einheitsparameter und Prüfverfahren - Allgemeine Festlegungen (IEC 62933-2-1:2017) This European Standard was approved by CENELEC on 2018-01-17. CENELEC members are bound to comply with the CEN/CENELEC Internal Regulations which stipulate the conditions for giving this European Standard the status of a national standard without any alteration. Up-to-date lists and bibliographical references concerning such national standards may be obtained on application to the CEN-CENELEC Management Centre or to any CENELEC member.
This European Standard exists in three official versions (English, French, German). A version in any other language made by translation under the responsibility of a CENELEC member into its own language and notified to the CEN-CENELEC Management Centre has the same status as the official versions. 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. EN IEC 62933-2-1:2018 E SIST EN IEC 62933-2-1:2018

The following dates are fixed: • latest date by which the document has to be implemented at national level by publication of an identical national standard or by endorsement (dop) 2018-10-17 • latest date by which the national standards conflicting with the document have to be withdrawn (dow) 2021-01-17
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. Endorsement notice The text of the International Standard IEC 62933-2-1:2017 was approved by CENELEC as a European Standard without any modification. In the official version, for Bibliography, the following notes have to be added for the standards indicated:
IEC 62620 NOTE Harmonized as EN 62620. IEC 62933-3-11 NOTE Harmonized as EN 62933-3-12. IEC 60060-1 NOTE Harmonized as EN 60060-1. IEC 60068-2(series) NOTE Harmonized as EN 60068-2 (series). IEC 60721-2-2 NOTE Harmonized as EN 60721-2-2. IEC 60721-2-4 NOTE Harmonized as HD 478.2.4 S1. IEC 60146-1-1 NOTE Harmonized as EN 60146-1-1. IEC 60146-1-3 NOTE Harmonized as EN 60146-1-3. IEC 60146-2 NOTE Harmonized as EN 60146-2. IEC 62109-1 NOTE Harmonized as EN 62109-1. IEC 62109-2 NOTE Harmonized as EN 62109-2. IEC 62116 NOTE Harmonized as EN 62116. IEC 62477-1:2012 NOTE Harmonized as EN 62477-1:2012 (not modified). IEC 62909-1 NOTE Harmonized as EN 62909-1. IEC 60947-1 NOTE Harmonized as EN 60947-1. IEC 60947-2 NOTE Harmonized as EN 60947-2 IEC 60947-3 NOTE Harmonized as EN 60947-3. IEC 60947-4-1 NOTE Harmonized as EN 60947-4-1. IEC 61439-1 NOTE Harmonized as EN 61439-1. IEC 61439-2 NOTE Harmonized as EN 61439-2. IEC 61439-3 NOTE Harmonized as EN 61439-3.
1 Under development. Stage at the time of publication: IEC CDM 62933-3-1:2017. 2 Under development. Stage at the time of publication: prEN 62933-3-1:2016. SIST EN IEC 62933-2-1:2018

(normative)
Normative references to international publications
with their corresponding European publications
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.
NOTE 1
Where an International Publication has been modified by common modifications, indicated by (mod), the relevant EN/HD applies.
NOTE 2
Up-to-date information on the latest versions of the European Standards listed in this annex is available here: www.cenelec.eu.
Publication Year Title EN/HD Year IEC 60364-6 -
Low-voltage electrical installations - Part 6: Verification HD 60364-6 -
IEC 61000-4-7 -
Electromagnetic compatibility (EMC) -- Part 4-7: Testing and measurement techniques - General guide on harmonics and interharmonics measurements and instrumentation, for power supply systems and equipment connected thereto EN 61000-4-7 -
IEC 61400-21 -
Wind turbines -- Part 21: Measurement and assessment of power quality characteristics of grid connected wind turbines EN 61400-21 -
IEC TR 61850-90-7 -
Communication networks and systems for power utility automation - Part 90-7: Object models for power converters in distributed energy resources (DER) systems - -
IEC 61936-1 -
Power installations exceeding 1 kV a.c. -- Part 1: Common rules EN 61936-1 -
IEC 62933-13 -
Electrical energy storage (EES) systems – Part 1: Vocabulary EN 62933-14 -
3 Under preparation. Stage at the time of publication: IEC FDIS 62933-1:2017. 4 Under preparation. Stage at the time of publication: FprEN 62933-1:2017 SIST EN IEC 62933-2-1:2018

IEC 62933-2-1 Edition 1.0 2017-12 INTERNATIONAL STANDARD NORME INTERNATIONALE Electrical energy storage (EES) systems –
Part 2-1: Unit parameters and testing methods – General specification
Systèmes de stockage de l'énergie électrique (EES) – Partie 2-1: Paramètres unitaires et méthodes d'essai – Spécifications générales INTERNATIONAL ELECTROTECHNICAL COMMISSION COMMISSION ELECTROTECHNIQUE INTERNATIONALE
ICS 13.020.30
ISBN 978-2-8322-5146-1
– 2 – IEC 62933-2-1:2017 © IEC 2017
CONTENTS FOREWORD . 5 1 Scope . 7 2 Normative references . 7 3 Terms, definitions, abbreviated terms and symbols . 7 3.1 Terms and definitions . 7 3.2 Abbreviated terms . 8 3.3 Symbols . 8 4 Classification of EES system . 8 4.1 General . 8 4.2 Categorizing the application of EES system . 9 4.3 Class A applications . 9 4.3.1 Frequency regulation . 9 4.3.2 Fluctuation reduction . 9 4.3.3 Voltage regulation . 9 4.4 Class B – Peak shaving/peak shifting . 10 4.5 Class C – Back-up power . 10 5 Unit parameters . 10 5.1 General . 10 5.1.1 Overview . 10 5.1.2 Reference environmental conditions . 10 5.1.3 Standard testing conditions . 11 5.1.4 Typical architecture . 11 5.2 List of unit parameters . 12 5.2.1 Nominal energy capacity . 12 5.2.2 Input and output power rating . 12 5.2.3 Roundtrip efficiency . 14 5.2.4 Expected service life . 15 5.2.5 System response . 15 5.2.6 Auxiliary power consumption . 16 5.2.7 Self- discharge of EES system . 17 5.2.8 Rated voltage range . 17 5.2.9 Rated frequency range . 17 6 Testing methods and procedures . 17 6.1 General . 17 6.2 Parameter test . 18 6.2.1 Actual energy capacity test . 18 6.2.2 Input and output power rating test. 19 6.2.3 Roundtrip efficiency test . 20 6.2.4 Expected service life test . 21 6.2.5 System response test, step response time and ramp rate . 21 6.2.6 Auxiliary power consumption test . 24 6.2.7 Self-discharge of EES system test . 24 6.2.8 Rated voltage and frequency range test . 25 6.3 Performance test . 25 6.3.1 General . 25 6.3.2 Performance test for class A applications . 26 SIST EN IEC 62933-2-1:2018

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6.3.3 Performance test for class B applications . 26 6.3.4 Performance test for Class C applications . 27 6.4 System implementation test . 27 6.4.1 Visual inspection . 27 6.4.2 Continuity and validity of conductors . 28 6.4.3 Earthing test . 28 6.4.4 Insulation test . 28 6.4.5 Protective and switching device test . 28 6.4.6 Equipment and basic function test . 29 6.4.7 Grid connection compatibility test . 29 6.4.8 Available energy test . 30 6.4.9 EMC immunity test . 30 Annex A (informative)
Duty cycle for efficiency test . 31 A.1 General . 31 A.2 Class A application duty cycle . 31 A.2.1 General . 31 A.2.2 Duty cycle . 31 A.3 Class B application duty cycles . 32 A.3.1 General . 32 A.3.2 Duty cycle . 32 Annex B (informative)
Fluctuation reduction test . 33 B.1 General . 33 B.2 Fluctuation reduction test . 33 Annex C (informative)
Back-to-back test method for EES system . 35 C.1 Back-to-back test without grid interconnection . 35 C.2 Back-to-back test with grid interconnection . 36 Bibliography . 37
Figure 1 – Example of classification of EES systems . 9 Figure 2 – Typical architecture of EES system . 12 Figure 3 – Optional architecture of EES system . 12 Figure 4 – Sign convention of active power and reactive power . 14 Figure 5 – Step response time and ramp rate of EES system . 16 Figure 6 – Typical testing points for apparent power . 20 Figure 7 – System response test . 23 Figure A.1 – Class A application duty cycle . 31 Figure A.2 – Class B application duty cycles . 32 Figure B.1 – Power stabilization test . 33 Figure B.2 – Report of stabilization test . 34 Figure C.1 – Back-to-back test configuration (EESS module type) . 35 Figure C.2 – Back-to-back test configuration (AC/DC/AC converter type) . 36 Figure C.3 – Back-to-back test configuration (EESS module type) . 36
– 4 – IEC 62933-2-1:2017 © IEC 2017 Table 1 – Example of typical and not exclusive applications classification . 9 Table 2 – Normal environmental conditions . 11 Table 3 – Standard testing conditions . 11 Table 4 – Document format of roundtrip efficiency . 20 Table 5 – Performance test items. 26
IEC 62933-2-1:2017 © IEC 2017 – 5 –
INTERNATIONAL ELECTROTECHNICAL COMMISSION ____________
ELECTRICAL ENERGY STORAGE (EES) SYSTEMS –
Part 2-1: Unit parameters and testing methods – General specification
FOREWORD 1) The International Electrotechnical Commission (IEC) is a worldwide organization for standardization comprising all national electrotechnical committees (IEC National Committees). The object of IEC is to promote international co-operation on all questions concerning standardization in the electrical and electronic fields. To this end and in addition to other activities, IEC publishes International Standards, Technical Specifications, Technical Reports, Publicly Available Specifications (PAS) and Guides (hereafter referred to as “IEC Publication(s)”). Their preparation is entrusted to technical committees; any IEC National Committee interested in the subject dealt with may participate in this preparatory work. International, governmental and non-governmental organizations liaising with the IEC also participate in this preparation. IEC collaborates closely with the International Organization for Standardization (ISO) in accordance with conditions determined by agreement between the two organizations. 2) The formal decisions or agreements of IEC on technical matters express, as nearly as possible, an international consensus of opinion on the relevant subjects since each technical committee has representation from all interested IEC National Committees.
3) IEC Publications have the form of recommendations for international use and are accepted by IEC National Committees in that sense. While all reasonable efforts are made to ensure that the technical content of IEC Publications is accurate, IEC cannot be held responsible for the way in which they are used or for any misinterpretation by any end user. 4) In order to promote international uniformity, IEC National Committees undertake to apply IEC Publications transparently to the maximum extent possible in their national and regional publications. Any divergence between any IEC Publication and the corresponding national or regional publication shall be clearly indicated in the latter. 5) IEC itself does not provide any attestation of conformity. Independent certification bodies provide conformity assessment services and, in some areas, access to IEC marks of conformity. IEC is not responsible for any services carried out by independent certification bodies. 6) All users should ensure that they have the latest edition of this publication. 7) No liability shall attach to IEC or its directors, employees, servants or agents including individual experts and members of its technical committees and IEC National Committees for any personal injury, property damage or other damage of any nature whatsoever, whether direct or indirect, or for costs (including legal fees) and expenses arising out of the publication, use of, or reliance upon, this IEC Publication or any other IEC Publications.
8) Attention is drawn to the Normative references cited in this publication. Use of the referenced publications is indispensable for the correct application of this publication. 9) Attention is drawn to the possibility that some of the elements of this IEC Publication may be the subject of patent rights. IEC shall not be held responsible for identifying any or all such patent rights. International Standard IEC 62933-2-1 has been prepared by IEC technical committee TC 120: Electrical energy storage (EES) systems. The text of this International Standard is based on the following documents: FDIS Report on voting 120/109/FDIS 120/115/RVD
Full information on the voting for the approval of this International Standard can be found in the report on voting indicated in the above table. This document has been drafted in accordance with the ISO/IEC Directives, Part 2. A list of all parts in the IEC 62933 series, published under the general title Electrical energy storage (EES) systems, can be found on the IEC website. SIST EN IEC 62933-2-1:2018

– 6 – IEC 62933-2-1:2017 © IEC 2017 The committee has decided that the contents of this document will remain unchanged until the stability date indicated on the IEC website under "http://webstore.iec.ch" in the data related to the specific document. At this date, the document will be
• reconfirmed, • withdrawn, • replaced by a revised edition, or • amended.
IMPORTANT – The 'colour inside' logo on the cover page of this publication indicates that it contains colours which are considered to be useful for the correct understanding of its contents. Users should therefore print this document using a colour printer.
IEC 62933-2-1:2017 © IEC 2017 – 7 –
ELECTRICAL ENERGY STORAGE (EES) SYSTEMS –
Part 2-1: Unit parameters and testing methods – General specification
1 Scope This part of IEC 62933 focuses on unit parameters and testing methods of EES systems. The energy storage devices and technologies are outside the scope of this document. This document deals with EES system performance defining:
– unit parameters, – testing methods. 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 60364-6, Low voltage electrical installations – Part 6: Verification IEC 61000-4-7, Electromagnetic compatibility (EMC) – Part 4-7: Testing and measurement techniques – General guide on harmonics and interharmonics measurements and instrumentation, for power supply systems and equipment connected thereto IEC 61400-21, Wind turbines – Part 21: Measurement and assessment of power quality characteristics of grid connected wind turbines IEC TR 61850-90-7, Communication networks and systems for power utility automation –
Part 90-7: Object models for power converters in distributed energy resources (DER) systems IEC 61936-1, Power installations exceeding 1 kV a.c. - Part 1: Common rules IEC 62933-11, Electrical energy storage (EES) systems – Part 1: Vocabulary 3 Terms, definitions, abbreviated terms and symbols 3.1 Terms and definitions For the purposes of this document, the terms and definitions given in IEC 62933-1 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 _____________ 1
Under preparation. Stage at the time of publication: IEC FDIS 62933-1:2017
– 8 – IEC 62933-2-1:2017 © IEC 2017 3.2 Abbreviated terms CAES compressed air energy storage CB circuit breaker
DLC double layer capacitor EES electrical energy storage FES flywheel energy storage NaS sodium sulphur NiCd nickel cadmium NiMH nickel metal hydride PHS pumped hydro storage POC point of connection SMES superconducting magnetic energy storage SNG synthetic natural gas SOC state of charge 3.3 Symbols rt roundtrip efficiency Eo total output energy measured at POC
EI total input energy measured at POC
aux_oE energy consumption of auxiliary subsystem measured at auxiliary POC during output operation aux_IE energy consumption of auxiliary subsystem measured at auxiliary POC during input operation RR ramp rate SRT step response time
P active power Q reactive power S apparent power U voltage I current Paux auxiliary power consumption 4 Classification of EES system
4.1 General
A widely-used approach for classifying EES systems is the determination according to the form of energy used. A classification example of EES systems according to energy form is shown in Figure 1. EES systems are classified into mechanical, electrochemical, chemical, electrical and thermal energy storage systems.
IEC 62933-2-1:2017 © IEC 2017 – 9 –
Figure 1 – Example of classification of EES systems 4.2 Categorizing the application of EES system The application and use of an EES system differs according to its purpose and location. The application of an EES system can be classified into three classes, and five representative applications are described in Table 1. The summary of the three classes of Table 1 is as follows: a) Class A: short-duration application that requires the EES system to input/output the required power over a duty cycle for a short period of time (for example, the EES system is charged and discharged in less than 1 h). b) Class B: long-duration application that requires the EES system to input/output the required power over a duty cycle for a long period of time (for example, the EES system is charged and discharged in more than 1 h).
c) Class C: the EES system is used to supply AC power to electric power grids in emergency case, without relying on an external power source. One EES system can be used in combination with applications of different classes.
Table 1 – Example of typical and not exclusive applications classification Classifications Class A
(short duration) Class B (long duration) Class C
(back-up) Typical applications Frequency regulation Fluctuation reduction
Voltage regulation Peak shaving/peak shifting Back-up power
4.3 Class A applications 4.3.1 Frequency regulation The EES system supports grid frequency stabilization using active power. 4.3.2 Fluctuation reduction The EES system stabilizes a fluctuating power supply or a fluctuating load. 4.3.3 Voltage regulation The EES system stabilizes the voltage of a power grid using reactive and active power. IEC
Sensible heat storage Molten salt/A-CAES
Superconducting magnetic coil – SMES
Double-layer Capacitor – DLC
Hydrogen Electrolyser/Fuel cell/SNG
Flow batteries Redox flow/Hybrid flow
Secondary batteries Lead acid/NiCd/NiMH/Li/NaS
Pumped hydro – PHS Compressed air – CAES
Flywheel – FES EES systems Mechanical Electrochemical Chemical Electrical Thermal SIST EN IEC 62933-2-1:2018

– 10 – IEC 62933-2-1:2017 © IEC 2017 4.4 Class B – Peak shaving/peak shifting The EES system has a function to use the stored energy for peak demand or a function to store excess energy of generation. EES system can achieve better operation efficiency of the transmission and distribution lines. 4.5 Class C – Back-up power The EES system has a function to supply AC power in electric power grids or microgrids installed to operate critically important systems over a fixed duration in accordance with the system specifications. ESS system can therefore reduce the risk of major blackouts. 5 Unit parameters
5.1 General
5.1.1 Overview The following parameters shall be specified as the common basic parameters to ensure EES system capability and performance: • nominal energy capacity (Wh); • input and output power rating (W, var, VA); • roundtrip efficiency (%); • expected service life (years, duty-cycles); • system response (step response time (s) and ramp rate (W/s)); • auxiliary power consumption (W); • self-discharge of EESS (Wh/h); • voltage range (V); • frequency range (Hz). Each parameter defined in this document shall be measured and evaluated at the POC. 5.1.2 Reference environmental conditions The EES system shall be used under the conditions listed in Table 2. SIST EN IEC 62933-2-1:2018

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Table 2 – Normal environmental conditions
Indoor installation Outdoor installation Ambient air temperature Upper limit ≤ 40 °C ≤ 40 °C and 24 h average ≤ 35 °C ≤ 35 °C and one category: or or -5 indoor: ≥ −5 °C -15 indoor: ≥ −15 °C -25 indoor: ≥ −25 °C -10 outdoor: ≥ −10 °C -25 outdoor: ≥ −25 °C -40 outdoor: ≥ −40 °C Solar radiation (clear day, noon) Negligible ≤ 1 000 W/ma b Altitude ≤ 1 000 m ≤ 1 000 m Relative humidity: 24 h average ≤ 95 % b
Condensation, precipitation
c a
Details of global solar radiation are given in IEC 60721-2-4. Ultraviolet (UV) radiation can damage some synthetic materials, for more details see IEC 60068. b
For these conditions, condensation may occasionally occur. Condensation can be expected where sudden temperature changes occur in periods of high humidity. To avoid breakdown of insulation or corrosion of metallic parts due to high humidity and condensation, equipment designed for such conditions and tested accordingly should be used. Condensation may be prevented by special design of the building or housing, by suitable ventilation and heating of the station or by the use of dehumidifying equipment. c
Precipitation in the form of dew, condensation, fog, rain, snow, ice or hoar frost should be taken into account. Precipitation characteristics for insulation are described in IEC 60060-1 and IEC 60071-1. For other properties, precipitation characteristics are described in IEC 60721-2-2.
When the EES system is intended to be used under conditions different from the normal environmental conditions given in Table 2, an agreement between user and system supplier is necessary. For each test described in this document, the system supplier shall report the following environmental conditions: a) ambient air temperature b) altitude c) relative humidity/condensation and precipitation (precipitation is only needed for outdoor equipment) d) Atmospheric pressure 5.1.3 Standard testing conditions The EES system shall be tested under the conditions listed in Table 3. However, if it cannot be tested under standard test conditions, conversion to standard test conditions is allowed. Table 3 – Standard testing conditions Item Conditions Ambient air temperature 25 ºC
Altitude ≤ 1 000 m Humidity ≤ 95 % with no condensation
5.1.4 Typical architecture The typical architecture of an EES system is shown in Figure 2. The boundary between the EES system and the electrical power system is defined as POC. Each parameter that is defined in this document shall be measured at POC. SIST EN IEC 62933-2-1:2018

– 12 – IEC 62933-2-1:2017 © IEC 2017 Figure 2 and Figure 3 are examples.
Figure 2 – Typical architecture of EES system If the auxiliary subsystem is fed from another feeder, the optional architecture of the ESS system is shown in Figure 3.
Figure 3 – Optional architecture of EES system 5.2 List of unit parameters
5.2.1 Nominal energy capacity The nominal energy capacity is the energy that can be output by the system at POC under the standard testing conditions specified in 5.1.2. The energy capacity shall be evaluated considering energy losses including conversion loss and energy used for the auxiliary subsystem. The energy capacity shall be defined as the product of the rated output power and the output duration time at this rated power. The unit of energy capacity shall be defined as Wh for an EES system.
5.2.2 Input and output power rating 5.2.2.1 General The input and output power is the value of power that an EES system can absorb or provide for a specified time at the POC under the reference environmental conditions specified in 5.1.3. The rated input and output power shall be specified together with input or output duration. Accumulation subsystem Power conversion subsystem POC Connection subsystem Communication interface Auxiliary subsystem Control subsystem Communication subsystem Protection subsystem Management subsystem IEC Primary subsystem Accumulation subsystem Power conversion subsystem Primary POC Primary connection subsystem Auxiliary POC Auxiliary subsystem Auxiliary connection subsystem Control subsystem Communication interface
Communication subsystem Protection subsystem Management subsystem IEC Primary subsystem SIST EN IEC 62933-2-1:2018

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The input and output power are classified as active power (P), reactive power (Q) and apparent power (S) and the required parameters from these three parameters depending on applications shall be specified. The units of active power, reactive power and apparent power are defined as W, var and VA respectively. 5.2.2.2 Active power The rated input active power of the EES system is the maximum value of power that can be input at constant for a specified duration at the POC from the lower state of charge limit. Input active power shall be expressed with a negative sign as shown in Figure 4 according to IEC 62933-1 and IEC TR 61850-90-7.
The rated output active power of the EES system is the maximum value of power that can be output for a specified duration at POC from the full available energy level. Output active power shall be expressed with a positive sign as shown in Figure 4 according to IEC 62933-1 and IEC TR 61850-90-7. The EES system can be applied for various types of applications as listed in Table 1. Different types of input and output characteristics are required for various applications. Therefore, the input power rating, output power rating and input and output period during which the EES system can absorb or deliver constant power should be defined based on the application. Specific input and output related performance parameters for specific applications may be added as required. Short-duration input and output power is an example. Short-duration input power is the maximum power that the EES system can input at the POC during a specified duration, which is typically less than 5 min. Short-duration output power is the maximum power that the EES system can output at the POC for a specified duration, which is typically less than 5 min. The specific conditions, such as duration for short duration input and output power, shall be specified as agreed upon by the system supplier and user for these specific parameters. 5.2.2.3 Reactive power The rated reactive power of the EES system is the maximum value of constant reactive power that can be output or input continuously at the POC. Sign convention of reactive power is shown in Figure 4 according to IEC 62933-1 and IEC TR 61850-90-7.
5.2.2.4 Apparent power The apparent power is the absolute value of combining active power and reactive power at the POC as shown in Figure 4.
– 14 – IEC 62933-2-1:2017 © IEC 2017
Figure 4 – Sign convention of active power and reactive power NOTE The purpose of Figure 4 is to define the sign convention of active power and reactive power. The P and Q characteristic of EES system described in Figure 4 is an example with the same ratings for charging and discharging. 5.2.3 Roundtrip efficiency The roundtrip efficiency is the ratio of total output energy divided by total input energy over one charging/discharging cycle using rated input and output power, and it should be evaluated by energy efficiency in cycle, which is charging from minimum available energy level to the full available energy level, then discharging to the minimum available energy level. The roundtrip efficiency depends on actual energy capacity, rated input active power, rated output active power, power consumption of the auxiliary subsystem, as well as the standard testing conditions specified in 5.1.3.
The roundtrip efficiency (rt) shall be defined as shown in the formula below. For Figure 2:
IortEE=η (1) For Figure 3:
aux_IIaux_o ortEEEE+−=η (2) +P (W) +Q (var) –Q (var) –P (W) Rated Q Rated P S (VA) Operating zone (Output) (Input) –Q (var) +P (W) –P (W) Operating zone (Capacitive) (Inductive) (Capacitive) (Inductive) Rated P S (VA) (Output) (Input) (Capacitive) (Inductive) (Capacitive) (Inductive) IEC Rated Q
EES system P, Q: + POC
Power grid I: + SIST EN IEC 62933-2-1:2018

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where Eo
is the total output energy measured at the (primary) POC considering energy losses including conversion loss and energy used for the auxiliary subsystem in as shown in Figure 2, EI is the total input energy measured at the (primary) POC, Eaux_o is the energy consumption of the auxiliary subsystem measured at the auxiliary POC during output operation as shown in Figure 3,
Eaux_I is the energy consumption of the auxiliary subsystem measured at the auxiliary POC during the input operation as shown in Figure 3. 5.2.4 Expected service life The time point when any of the following degradation phenomena have occurred and EES system no longer complies with the specifications is defined as expected service life of EES system. The end of service life values that are specified in the specification should be used as performance criteria as follows so that EES system can comply with the specifications. • The nominal energy capacity of the EES system at rated power becomes lower than the end of service life values. • The input and output power during system charging and discharging for a specified duration is lower than the end of service life values. • The system response is deteriorated for end of service life values. In view of these points, the degradation characteristic due to ageing or the charge and discharge cycles shall be considered as one of the important performance data to evaluate the expected service life of the EES system. In particular, the actual initial energy capacity of the EES system should be calculated in the planning stage taking into account the energy capacity degradation characteristics depending on the applications addressed by the EES system to meet the required service life of the EES system. NOTE In some cases, the end of service life values can be considered as rated values. 5.2.5 System response
5.2.5.1 Step response time The step response time of the EES system is the duration of the time interval between the instant T0 when the set point is received at the EES system, which is in stand-by mode, or when the grid parameter changes in a way to trigger the system response, and the instant T3 when the active power at the POC reaches within 2 % of the set point as shown in Figure 5. A detailed definition of T0 shall be agreed between the system supplier and user. The reference set point for the definition of the step response time is the rated input/output power. If the system has a rated value of reactive power, then the step response time shall be also tested at: – rated input/output reactive power, – rated input/output apparent power (with different ratio of active/reactive powers), – other set points with reduced power respect to the rated one. NOTE In general, the response time of reactive power is covered by the response time of active power, because the response time of reactive power is faster than the response time of active power. 5.2.5.2 Ramp rate The ramp rate of the EES system is the average rate of active power variation per unit of time between T2 and T1 as shown in Figure 5. T1 is the time when the active power at the POC becomes higher than 2 % of the set point value. T2 is the time when the active power at the POC becomes higher than 98 % of the set point value. The reference set point for the SIST EN IEC 62933-2-1:2018

– 16 – IEC 62933-2-1:2017 © IEC 2017 definition of the ramp rate is the rated input and output power to decide the charge and discharge ramp rate. In case the consideration of non-linear characteristics or transition behaviour during mode change for the ramp rate is required, for example charge – discharge – charge, the definition of ramp rate shall be defined by agreement between the user and system supplier.
()W/s)()(1212TTTPTPRR−−= (3) If the system has a rated value of reactive power, then the ramp rate shall be also tested at: – rated input/output reactive power, – rated input/output apparent power (with different ratios of active/reactive powers), – other set points with reduced power respect to the rated one.
Figure 5 – Step response time and ramp rate of EES system 5.2.6 Auxiliary power consumption The auxiliary power consumption corresponds to the power needed to operate the auxiliary subsystem. The unit shall be defined as W. Auxiliary power consumption shall be measured or estimated by keeping the parameters of power conversion subsystem as in the following five cases: a) active power 0 W and reactive power 0 var,
b) rated output active power,
c) rated input active power,
d) rated output reactive power (if the system has a rated value of reactive power), e) rated input reactive power (if the system has a rated value of reactive power).
In case
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