IEC TS 62257-301:2025
(Main)Renewable energy off-grid systems - Part 301: Generators - Integration of solar with other forms of power generation within hybrid power systems
Renewable energy off-grid systems - Part 301: Generators - Integration of solar with other forms of power generation within hybrid power systems
IEC TS 62257-301:2025 specifies the design and implementation of hybrid off-grid solar systems, where solar energy provides energy to a load in conjunction with other sources of energy. Such systems can either include or not include an energy storage system. There are a variety of different system architectures and applications, and many ways in which these energy sources can be combined. This document distinguishes between different sorts of hybrid system applications and gives guidance on the design and integration of these systems.
It applies to single-phase and three-phase applications, and it covers situations where grid is available as an additional source of power for charging batteries and maintaining system reliability, but this document does not cover situations in which energy is fed back into a utility grid, although such systems can incidentally possess this function.
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IEC TS 62257-301 ®
Edition 1.0 2025-08
TECHNICAL
SPECIFICATION
Renewable energy off-grid systems -
Part 301: Generators - Integration of solar with other forms of power generation
within hybrid power systems
ICS 27.160 ISBN 978-2-8327-0622-0
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CONTENTS
FOREWORD . 2
INTRODUCTION . 4
1 Scope . 5
2 Normative references . 5
3 Terms and definitions . 5
4 Overview . 7
5 Types of hybrid systems . 7
5.1 General . 7
5.2 Multi-master rotating machine dominated mini-grid . 8
5.2.1 General. 8
5.2.2 Design . 8
5.2.3 Design and selection of fuel powered generators. 9
5.2.4 Design and selection of renewable energy component . 9
5.2.5 Design and selection of batteries . 10
5.2.6 Control system . 10
5.3 Single switched master mini-grid . 11
5.3.1 General. 11
5.3.2 Design . 12
5.3.3 Design and selection of fuel powered generators. 12
5.3.4 Design and selection of renewable energy component . 12
5.3.5 Design and selection of batteries . 13
5.3.6 System control . 13
5.4 Multi-master inverter dominated mini-grid . 15
5.4.1 General. 15
5.4.2 Design . 15
5.4.3 Design and selection of fuel powered generators. 15
5.4.4 Design and selection of renewable energy component . 15
5.4.5 Design and selection of batteries . 16
5.4.6 Control. 16
Bibliography . 18
Figure 1 – Typical multi-master rotating machine dominated mini-grid architecture . 8
Figure 2 – Single switched master mini-grid architecture . 11
Figure 3 – Multi-master inverter dominated mini-grid architecture . 15
INTERNATIONAL ELECTROTECHNICAL COMMISSION
____________
Renewable energy off-grid systems -
Part 301: Generators - Integration of solar with other forms
of power generation within hybrid power systems
FOREWORD
1) The International Electrotechnical Commission (IEC) is a worldwide organization for standardization comprising
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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) IEC draws attention to the possibility that the implementation of this document may involve the use of (a)
patent(s). IEC takes no position concerning the evidence, validity or applicability of any claimed patent rights in
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shall not be held responsible for identifying any or all such patent rights.
IEC TS 62257-301 has been prepared by IEC technical committee 82: Solar photovoltaic energy
systems. It is a Technical Specification.
This first edition cancels and replaces IEC TS 62257-7-4, published in 2019.
The text of this Technical Specification is based on the following documents:
Draft Report on voting
82/2408/DTS 82/2463/RVDTS
Full information on the voting for its approval can be found in the report on voting indicated in
the above table.
The language used for the development of this Technical Specification is English.
This document was drafted in accordance with ISO/IEC Directives, Part 2, and developed in
accordance with ISO/IEC Directives, Part 1 and ISO/IEC Directives, IEC Supplement, available
at www.iec.ch/members_experts/refdocs. The main document types developed by IEC are
described in greater detail at www.iec.ch/publications.
This part of IEC 62257 is to be used in conjunction with IEC 62257 (all parts).
A list of all parts in the IEC 62257 series, published under the general title Renewable energy
off-grid systems, can be found on the IEC website.
Future standards in this series will carry the new general title as cited above. Titles of existing
standards in this series will be updated at the time of the next edition.
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, or
• revised.
INTRODUCTION
The IEC 62257 series provides technical standardization to different stakeholders (including
but not limited to project developers, financing agencies, testing agencies, installers, etc.)
involved in electrification projects for access to electricity for those not solely connected to the
regional grid, through the setting up of off-grid renewable energy and hybrid systems (including
micro-grids) with a voltage less than or equal to 1 000 V for AC (alternating current) or a voltage
less than or equal to 1 500 V for DC (direct current).
Access to electricity is one of the predominant policy actions designed to increase the well-
being of populations, together with access to clean water, improved healthcare, education,
personal advancement, and economic development. Increasing access to electricity through
utilization of renewable off-grid electricity also directly or indirectly supports various United
Nations Sustainable Development Goals (https://sdgs.un.org/goals), depending on the
application.
The IEC 62257 technical specifications focus on enabling access to electricity by concentrating
on, but not being specific to, developing countries. This series should not be considered as all-
inclusive for access to electricity. That means that the technical specifications could be used
for rural electrification, also for electrification of remote sites in developed countries, or any
requirement for electricity access that cannot be met by attaching solely to the national utility
grid.
One of the main objectives of this series is to provide the minimum sufficient recommendations,
including items for safety, sustainability of systems, and at the lowest life cycle cost, relevant
to the renewable energy and hybrid off-grid systems field of application.
Where connection to a national or regional electricity grid is not possible or reliable enough to
provide the desired level of electrification, renewable energy off grid and hybrid systems are
typically used to provide it. These autonomous renewable energy and hybrid systems can
provide electricity without connection to the larger utility grid.
Using renewable energy off-grid and hybrid systems to create “access to electricity” applies to
cases where the regional grid is too far away and/or too costly for the user(s) to connect to the
regional grid, and where autonomous power systems can be used to supply these services.
1 Scope
This part of IEC 62257, which is a technical specification, sp
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