Electrical energy storage (EES) systems - Part 2-2: Unit parameters and testing methods - Application and performance testing

IEC TS 62933-2-2:2022(E) defines testing methods and duty cycles to validate the EES system’s technical specification for the manufacturers, designers, operators, utilities and owners of the EES systems which evaluate the performance of the EES systems for various applications. The following items are covered in this document. The energy storage devices and technologies are outside the scope of this document:
application;
performance testing methods;
duty cycles for specific application.

General Information

Status
Published
Publication Date
25-Apr-2022
Current Stage
PPUB - Publication issued
Completion Date
26-Apr-2022
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IEC TS 62933-2-2:2022 - Electrical energy storage (EES) systems - Part 2-2: Unit parameters and testing methods - Application and performance testing
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IEC TS 62933-2-2
Edition 1.0 2022-04
TECHNICAL
SPECIFICATION
colour
inside
Electrical energy storage (EES) systems –
Part 2-2: Unit parameters and testing methods – Application and performance
testing
IEC TS 62933-2-2:2022-04(en)
---------------------- Page: 1 ----------------------
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---------------------- Page: 2 ----------------------
IEC TS 62933-2-2
Edition 1.0 2022-04
TECHNICAL
SPECIFICATION
colour
inside
Electrical energy storage (EES) systems –
Part 2-2: Unit parameters and testing methods – Application and performance
testing
INTERNATIONAL
ELECTROTECHNICAL
COMMISSION
ICS 13.020.30 ISBN 978-2-8322-1104-1

Warning! Make sure that you obtained this publication from an authorized distributor.

® Registered trademark of the International Electrotechnical Commission
---------------------- Page: 3 ----------------------
– 2 – IEC TS 62933-2-2:2022 © IEC 2022
CONTENTS

FOREWORD ........................................................................................................................... 5

INTRODUCTION ..................................................................................................................... 7

1 Scope .............................................................................................................................. 8

2 Normative references ...................................................................................................... 8

3 Terms, definitions and abbreviated terms ........................................................................ 8

3.1 Terms and definitions .............................................................................................. 8

3.2 Abbreviated terms ................................................................................................... 9

4 Application of EES system ............................................................................................... 9

4.1 General ................................................................................................................... 9

4.2 Class A applications ............................................................................................... 9

4.2.1 Frequency control ............................................................................................ 9

4.2.2 Primary/secondary/tertiary frequency control ................................................... 9

4.2.3 Fluctuation reduction of PV and wind farms ................................................... 10

4.2.4 Reactive-power voltage control ...................................................................... 10

4.2.5 Voltage sag mitigation ................................................................................... 10

4.3 Class B applications ............................................................................................. 10

4.3.1 Peak shaving ................................................................................................. 10

4.3.2 Renewable firming ......................................................................................... 10

4.3.3 Islanded grid .................................................................................................. 11

4.4 Class C applications ............................................................................................. 11

5 Parameter testing methods for application ..................................................................... 11

5.1 Parameter tests .................................................................................................... 11

5.1.1 General ......................................................................................................... 11

5.1.2 Actual energy capacity ................................................................................... 11

5.1.3 Roundtrip efficiency ....................................................................................... 11

5.1.4 Step response time and ramp rate ................................................................. 12

5.1.5 Auxiliary power consumption ......................................................................... 12

5.1.6 Self-discharge ............................................................................................... 12

5.1.7 SOC .............................................................................................................. 12

5.2 Duty cycle performance tests ................................................................................ 12

5.2.1 General ......................................................................................................... 12

5.2.2 Duty cycle roundtrip efficiency ....................................................................... 12

5.2.3 Reference signal tracking .............................................................................. 12

5.3 Test items for each application ............................................................................. 14

6 Duty cycle for specific applications ................................................................................ 15

6.1 General ................................................................................................................. 15

6.2 Frequency control ................................................................................................. 15

6.2.1 Frequency control duty cycle ......................................................................... 15

6.2.2 Primary/secondary/tertiary frequency control duty cycle ................................. 16

6.2.3 Deviation control of frequency ....................................................................... 18

6.3 Fluctuation reduction of PV and wind farm ............................................................ 20

6.4 Reactive-power voltage control ............................................................................. 22

6.5 Voltage sag mitigation ........................................................................................... 23

6.6 Peak shaving ........................................................................................................ 26

6.6.1 “One charge-one discharge” mode ................................................................. 26

6.6.2 “Two charges-two discharges” mode .............................................................. 28

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IEC TS 62933-2-2:2022 © IEC 2022 – 3 –

6.7 Renewable firming ................................................................................................ 29

6.8 Islanded grid ......................................................................................................... 30

6.9 Back-up power ...................................................................................................... 32

6.9.1 General ......................................................................................................... 32

6.9.2 Grid outage test ............................................................................................. 32

6.9.3 Step load test ................................................................................................ 32

6.9.4 Unbalanced load test ..................................................................................... 33

6.9.5 Function test .................................................................................................. 33

6.9.6 Grid recovery test .......................................................................................... 33

Annex A (normative) Numerical data for duty cycle ............................................................. 34

Bibliography .......................................................................................................................... 66

Figure 1 – Frequency control duty cycle ................................................................................ 16

Figure 2 – Primary frequency control signal – 24 h duty cycle with 30 s discharge

every half hour shown over a) 24 h and b) 2 h ...................................................................... 17

Figure 3 – Secondary frequency control signal – 24 h duty cycle with 20 min discharge

every hour shown over a) 24 h and b) 3 h ............................................................................. 18

Figure 4 – Example of droop active power frequency control with a dead band ..................... 19

Figure 5 – Duty cycle of fluctuation reduction of PV (photovoltaic energy systems) ............... 20

Figure 6 – Duty cycle of fluctuation reduction of wind farm .................................................... 21

Figure 7 – Duty cycle of fluctuation reduction of wind farm (low standard deviation) .............. 21

Figure 8 – Duty cycle of fluctuation reduction of wind farm (average standard

deviation) .............................................................................................................................. 22

Figure 9 – Duty cycle of fluctuation reduction of wind farm (high standard deviation) ............ 22

Figure 10 – Reactive-power voltage control test profile ......................................................... 23

Figure 11 – Voltage sag mitigation test profile (test level: 80 %) ........................................... 24

Figure 12 – Voltage sag mitigation test profile (test level: 70 %) ........................................... 25

Figure 13 – Voltage sag mitigation test profile (test level: 40 %) ........................................... 25

Figure 14 – Voltage sag mitigation test profile (test level: 0 %) ............................................. 26

Figure 15 – Duty cycle for peak shaving application of “one charge-one discharge”

mode .................................................................................................................................... 28

Figure 16 – Duty cycle for peak shaving of “two charges-two discharges” mode .................... 29

Figure 17 – Duty cycle for renewable firming mode ............................................................... 30

Figure 18 – Duty cycle for fluctuation reduction of renewable energy sources (power)

and frequency control ........................................................................................................... 31

Figure 19 – Duty cycle for fluctuation reduction of renewable energy sources (power)

without frequency control ...................................................................................................... 31

Figure 20 – Duty cycle without fluctuation reduction of renewable energy sources

(power) or frequency control ................................................................................................. 32

Table 1 – Test items for each application .............................................................................. 15

Table 2 – Reactive-power voltage control test profile ............................................................ 23

Table A.1 – Numerical data of Figure 1 (duty cycle of frequency control ) ............................. 35

Table A.2 – Numerical data of Figure 5 (duty cycle of fluctuation reduction of PV

(photovoltaic energy systems) ) ............................................................................................ 40

Table A.3 – Numerical data of Figure 7 (duty cycle of fluctuation reduction of wind

farm (low standard deviation)) ............................................................................................... 44

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– 4 – IEC TS 62933-2-2:2022 © IEC 2022

Table A.4 – Numerical data of Figure 8 (duty cycle of fluctuation reduction of wind

farm (average standard deviation)) ....................................................................................... 45

Table A.5 – Numerical data of Figure 9 (duty cycle of fluctuation reduction of wind

farm (high standard deviation)) ............................................................................................. 46

Table A.6 – Numerical data of Figure 17 (duty cycle for renewable firming mode) ................. 47

Table A.7 – Numerical data of Figure 18 (duty cycle for fluctuation reduction of

renewable energy sources (power) and frequency control) .................................................... 51

Table A.8 – Numerical data of Figure 19 (duty cycle for fluctuation reduction of

renewable energy sources (power) without frequency control) .............................................. 56

Table A.9 – Numerical data of Figure 20 (duty cycle without fluctuation reduction of

renewable energy sources (power) or frequency control) ...................................................... 61

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IEC TS 62933-2-2:2022 © IEC 2022 – 5 –
INTERNATIONAL ELECTROTECHNICAL COMMISSION
____________
ELECTRICAL ENERGY STORAGE (EES) SYSTEMS –
Part 2-2: Unit parameters and testing methods –
Application and performance testing
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

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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

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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 62933-2-2 has been prepared by IEC technical committee TC 120: Electrical Energy

Storage (EES) Systems. It is a Technical Specification.
The text of this Technical Specification is based on the following documents:
Draft Report on voting
120/249/DTS 120/264A/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.

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– 6 – IEC TS 62933-2-2:2022 © IEC 2022

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.

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.

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.
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IEC TS 62933-2-2:2022 © IEC 2022 – 7 –
INTRODUCTION

Considering the wide variety of applications of EES systems, it is becoming important to define

the typical application of each EES system depending on its purpose and control types, and

also important to define the corresponding performance testing methods and procedures of the

EES system.

IEC 62933-2-1 describes the general specification of unit parameters and testing methods for

EES systems, in which details of duty cycles for typical grid applications and the associated

performance metrics and testing methods are not covered.

This part of IEC 62933 focuses on developing generic duty cycles for applications, identifying

relevant performance metrics and developing performance testing methods and procedures for

EES systems.
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– 8 – IEC TS 62933-2-2:2022 © IEC 2022
ELECTRICAL ENERGY STORAGE (EES) SYSTEMS –
Part 2-2: Unit parameters and testing methods –
Application and performance testing
1 Scope

This part of IEC 62933 defines testing methods and duty cycles to validate the EES system’s

technical specification for the manufacturers, designers, operators, utilities and owners of the

EES systems which evaluate the performance of the EES systems for various applications. The

following items are covered in this document. The energy storage devices and technologies are

outside the scope of this document:
– application;
– performance testing methods;
– duty cycles for specific application.

This document will be used as a reference when selecting testing items and their corresponding

evaluation methods.
This document considers applications such as:
• frequency control;
• primary/secondary/tertiary frequency control;
• fluctuation reduction of PV and wind farm;
• reactive-power voltage control;
• power quality events mitigation;
• peak shaving;
• renewable firming;
• back-up power;
• islanded grid.
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 62933-1, Electrical energy storage (EES) systems – Part 1: Vocabulary

IEC 62933-2-1, Electrical energy storage (EES) systems – Part 2: Unit parameters and testing

methods – General specification
3 Terms, definitions and abbreviated terms
3.1 Terms and definitions

For the purposes of this document, the terms and definitions given in IEC 62933-1 apply.

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IEC TS 62933-2-2:2022 © IEC 2022 – 9 –

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
3.2 Abbreviated terms
EES: Electrical energy storage
EESS SOC: State of charge of EES system
POC: Point of connection
UPS: Uninterruptable power systems
4 Application of EES system
4.1 General

The applications of EES systems differ according to their purposes. The applications of EES

systems are classified into three classes:

a) class A applications: short duration/power intensive applications (with a duty cycle of less

than 1 h);

b) class B applications: long duration/energy intensive applications (with a duty cycle of more

than 1 h), and
c) class C applications: back-up applications.

IEC 62933-2-1 provides classification details. The typical application of each class will be

described hereinafter.
4.2 Class A applications
4.2.1 Frequency control

EES systems provide a grid frequency control function to increase the frequency by discharging

and to reduce the frequency by charging. The system frequency will be controlled within a

predetermined bandwidth. The control subsystem in the EES system continuously measures

the frequency and then sends a control signal to the power conversion subsystem to increase

or decrease the amount of active power injected into the grid or the amount of load on the grid.

4.2.2 Primary/secondary/tertiary frequency control

In this application, there is a sudden loss of generation which leads to be made up through a

discharge from the EES system. In the case of a sudden loss of load in the grid, energy is

charged into the EES.

Generally, the definition of each control is based on the control order and control time period.

The following are example cases for reference.

Primary frequency control comes first and usually it is automatically initiated. It is activated

within a few seconds and lasts up to a few minutes.

Primary frequency control is followed by secondary frequency control if necessary and is

initiated automatically or manually. It should have an activation time typically between 30 s and

up to15 min.

Tertiary frequency control is used to resolve any additional imbalance that exists after the

primary and secondary frequency control has been carried out. It should have an activation time

typically between 15 min and several hours.
---------------------- Page: 11 ----------------------
– 10 – IEC TS 62933-2-2:2022 © IEC 2022

The activation time period of these controls is usually set in the grid code of each country or

region.
4.2.3 Fluctuation reduction of PV and wind farms

An EES system is used to reduce the rapid fluctuations of the power output from PV and wind

farms. The purpose of fluctuation reduction of the power output from PV and wind farms is to

help to meet the ramp rate requirements. This action will mitigate frequency variation and

stability issues at both feeder and transmission levels particularly with high penetration PV and

wind farm scenarios.

At the feeder level, fluctuation reduction of PV and wind farm is implemented to mitigate voltage

flicker and voltage deviations from desired bands. At the transmission level, PV and wind farm

variability can require an additional operating reserve to be set aside. This can cause traditional

power generation facilities to be cycled on/off more often than desirable.

The method by which the EES system can provide reduction of PV and wind farm output power

power at appropriate times as determined by
fluctuation is to absorb or supply active/reactive

a control system resulting in a less variable composite power signal at the feeder and/or

transmission level.
4.2.4 Reactive-power voltage control

The reactive-power voltage control application addresses the fluctuations in the grid voltage by

providing reactive power support. EES systems inject reactive power as the grid voltage dips

and absorb reactive power as the grid voltage increases.
4.2.5 Voltage sag mitigation

The sag or interruption in voltage potentially causes power disturbances that negatively impact

power quality. EES systems mitigate voltage sags by discharging real power for up to a few

tens of seconds. The application of an EES system to improve power quality does not require

the EES system to provide enough energy for customers to ride through sag or interruption.

NOTE An event duration of more than 1 min is considered as outage mitigation.
4.3 Class B applications
4.3.1 Peak shaving

The EES system discharges stored energy into the grid upon an excess or peak of demand or

absorbs excess energy, available in the grid, for storage. With this balancing a time shift

between power generation and electricity usage is achieved.

Examples of this application include energy time shift of conventional/wind/solar/base load-

generation, and include transmission/distribution grid congestion relief.
4.3.2 Renewable firming

Renewable firming is the use of an EES system to provide energy to supplement renewable

power generation such that their combination produces steady power output over a desired time

window. More precisely, the purpose of renewable firming is to provide energy (or conversely,

to absorb energy) when renewable generation falls below some threshold (or conversely,

exceeds this threshold).

This service is performed to provide steady power output over a desired time window, usually

a period of multiple hours. Typically, the threshold is based upon the forecasted nominal

renewable power generation over the desired time window. Thus, the EES system is

compensating for the forecast uncertainty in actual renewable generation during that time

window.
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IEC TS 62933-2-2:2022 © IEC 2022 – 11 –

The method by which the EES system performs this service is described as follows. The EES

system discharges power during periods for which renewable generation falls short of the

threshold and absorbs power when renewable generation exceeds this threshold.
4.3.3 Islanded grid

The EES supports in islanded grids their multiple loads, distributed energy generation and

storage resources. In such a service the EES system provides energy to the load of the islanded

grid. The EES system converter typically operates in the voltage/frequency mode to control the

islanded grid.

The EES systems supply the islanded grid for a limited time when the power supply from the

other grid
...

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