IEC TS 62898-3-3:2023

Microgrids - Part 3-3: Technical requirements - Self-regulation of dispatchable loads

IEC TS 62898-3-3:2023 deals with frequency and voltage stabilization of AC microgrids by dispatchable loads, which react autonomously on variations of frequency and voltage with a change in active power consumption. Both 50 Hz and 60 Hz electric power systems are covered. This document gives requirements to emulate the self-regulation effect of loads including synthetic inertia.
The loads recommended for this approach are noncritical loads, this means their power modulation will not significantly affect the user as some kind of energy storage is involved which effectively decouples end energy use from the electricity supply by the electric network. The self-regulation of loads is beneficial both in island mode and grid-connected mode. This document gives the details of the self-regulation behaviour but does not stipulate which loads shall participate in this approach as an optional function.
This document covers both continuously controllable loads with droop control and ON/OFF switchable loads with staged settings. The scope of this document is limited to loads connected to the voltage level up to 35 kV. Reactive power for voltage stabilization and DC microgrids are excluded in this document.

General Information

• Status: Published
• Publication Date: 15-Aug-2023
• ICS: 29.240.01 - Power transmission and distribution networks in general
• Technical Committee: SC 8B - Decentralized electrical energy systems
• Drafting Committee: JWG 1 - TC 8/SC 8B/JWG 1
• Current Stage: PPUB - Publication issued
• Start Date: 17-Jul-2023
• Completion Date: 16-Aug-2023

Standards Content (Sample)

IEC TS 62898-3-3 ®
Edition 1.0 2023-08
TECHNICAL
SPECIFICATION
colour
inside
Microgrids –
Part 3-3: Technical requirements – Self-regulation of dispatchable loads

All rights reserved. Unless otherwise specified, no part of this publication may be reproduced or utilized in any form
or by any means, electronic or mechanical, including photocopying and microfilm, without permission in writing from
either IEC or IEC's member National Committee in the country of the requester. If you have any questions about IEC
copyright or have an enquiry about obtaining additional rights to this publication, please contact the address below or
your local IEC member National Committee for further information.

IEC Secretariat Tel.: [phone]
3, rue de Varembé [e-mail]
CH-1211 Geneva 20 www.iec.ch
Switzerland
About the IEC
The International Electrotechnical Commission (IEC) is the leading global organization that prepares and publishes
International Standards for all electrical, electronic and related technologies.

About IEC publications
The technical content of IEC publications is kept under constant review by the IEC. Please make sure that you have the
latest edition, a corrigendum or an amendment might have been published.

IEC publications search - webstore.iec.ch/advsearchform IEC Products & Services Portal - products.iec.ch
The advanced search enables to find IEC publications by a Discover our powerful search engine and read freely all the
variety of criteria (reference number, text, technical publications previews. With a subscription you will always have
committee, …). It also gives information on projects, replaced access to up to date content tailored to your needs.
and withdrawn publications.
Electropedia - www.electropedia.org
IEC Just Published - webstore.iec.ch/justpublished
The world's leading online dictionary on electrotechnology,
Stay up to date on all new IEC publications. Just Published
containing more than 22 300 terminological entries in English
details all new publications released. Available online and once
and French, with equivalent terms in 19 additional languages.
a month by email.
Also known as the International Electrotechnical Vocabulary

(IEV) online.
IEC Customer Service Centre - webstore.iec.ch/csc

If you wish to give us your feedback on this publication or need
further assistance, please contact the Customer Service
Centre: [e-mail].
IEC TS 62898-3-3 ®
Edition 1.0 2023-08
TECHNICAL
SPECIFICATION
colour
inside
Microgrids –
Part 3-3: Technical requirements – Self-regulation of dispatchable loads

INTERNATIONAL
ELECTROTECHNICAL
COMMISSION
ICS 29.240.01  ISBN 978-2-8322-7336-4

– 2 – IEC TS 62898-3-3:2023 © IEC 2023
CONTENTS
FOREWORD . 4
INTRODUCTION . 6
1 Scope . 7
2 Normative references . 7
3 Terms, definitions, abbreviated terms and symbols . 7
3.1 Terms and definitions . 8
3.2 Abbreviated terms and symbols . 16
3.2.1 Abbreviated terms . 16
3.2.2 Symbols . 16
4 Requirements on self-regulation . 17
4.1 General . 17
4.1.1 Operational ranges . 17
4.1.2 Continuous and discrete control . 17
4.1.3 Dead band . 18
4.1.4 Accuracy and resolution . 18
4.1.5 Step response objective . 19
4.1.6 Damping . 20
4.2 Frequency stabilization . 20
4.2.1 General . 20
4.2.2 Continuously controllable loads . 21
4.2.3 Switchable loads. 23
4.2.4 Recommended default values . 24
4.3 Voltage stabilization . 24
4.3.1 General . 24
4.3.2 Continuously controllable loads . 25
4.3.3 Switchable loads. 26
4.3.4 Recommended default values . 27
4.4 Hybrid controls for both voltage and frequency . 28
5 Testing . 28
5.1 General . 28
5.2 Test for frequency response of self-regulated loads . 30
5.2.1 Purpose . 30
5.2.2 Procedure . 30
5.2.3 Criteria . 30
5.2.4 Comments . 30
5.3 Test for voltage response of self-regulated loads . 30
5.3.1 Purpose . 30
5.3.2 Procedure . 30
5.3.3 Criteria . 31
5.3.4 Comments . 31
Annex A (informative) Background information about the self-regulation effect . 32
Annex B (informative) Choice of coefficients k and k . 34
f U
B.1 General . 34
B.2 Expression of coefficient k for self-regulation of frequency . 34
f
B.3 Example of frequency settings in an isolated microgrid . 35
B.4 Example of frequency settings in a large interconnected network . 36

B.5 Expression of coefficient k for self-regulation of voltage. 37
U
B.6 Example of voltage settings in an isolated microgrid . 38
Annex C (informative) Prioritization of loads . 40
Annex D (informative) Damping measure in electric power systems . 44
Annex E (informative) Formula development on the relation of power and torque . 46
Annex F (informative) Examples for desynchronisation strategies . 47
F.1 General . 47
F.2 Heterogeneous load types . 47
F.3 Fuzzy or randomized control logic . 47
F.4 Emulating continuously controllable loads . 47
Bibliography . 48

Figure 1 – Hysteresis curve of a switchable load . 10
Figure 2 – Typical step response of a system . 12
Figure 3 – Example of P(f) self-regulation before and after activating the dead band . 18
Figure 4 – Bode diagram of a typical differential loop . 21
Figure 5 – Time domain response of first order low-pass filter . 22
Figure 6 – Functional diagram of a combined frequency control function for
continuously controllable dispatchable loads . 22
Figure 7 – Example of a hysteresis controller to control the temperature of a freezer in
response to variations in grid frequency . 23
Figure 8 – Functional diagram of a combined voltage control function for continuously
controllable dispatchable loads . 26
Figure 9 – Schematic diagram for the test environment of a self-regulated load . 28
Figure A.1 – Frequency development after a disturbance . 32
Figure A.2 – Particle model of switchable loads . 33
Figure B.1 – Example of P(f) self-regulation in an isolated microgrid . 36
Figure B.2 – Example of P(f) self-regulation in a large interconnected network . 37
Figure B.3 – Example of P(U) self-regulation in an isolated microgrid . 39
Figure C.1 – Frequency distribution of the power frequency of a 50 Hz network . 40
Figure C.2 – Four different droop curves according to prioritization . 41
Figure C.3 – Schematic representation of voltage probability distribution . 42
Figure D.1 – Typical location for desired eigenvalues . 44

Table 1 – Declared frequency measurement accuracy levels . 18
Table 2 – Declared voltage measurement accuracy levels . 19
Table 3 – Time quality levels . 19
Table 4 – Performance quality levels . 20
Table B.1 – Relationship between k and droop for self-regulation of frequency . 35
f
Table B.2 – Relationship between k and droop for self-regulation of voltage . 38
U
Table C.1 – Frequency domain (example for 50 Hz systems) . 41
Table C.2 – Frequency domain (example for 60 Hz systems) . 41
Table C.3 – Voltage domain (example) . 43

– 4 – IEC TS 62898-3-3:2023 © IEC 2023
INTERNATIONAL ELECTROTECHNICAL COMMISSION
____________
MICROGRIDS –
Part 3-3: Technical requirements –
Self-regulation of dispatchable loads

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
...