IEC TR 63411:2025

Grid connection of offshore wind via VSC-HVDC systems

IEC TR 63411:2025 discusses the challenges of connecting offshore wind farms via VSC-HVDC, key technical issues and emerging technologies. The potential solutions include new technologies, methods and practices to provide more flexibility and improve the efficiency of power systems. The primary objective of this document is to provide a comprehensive overview of challenges, potential solutions, and emerging technologies for grid integration of large-scale offshore wind farms via VSC-HVDC. It is expected that this document can also provide guidance for further standardization on relevant issues. The purpose of this document is not intended to hinder any further development of state-of-art technologies in this field. This Technical report is not an exhaustive document in itself to specify any scope of work or similar, between a purchaser and a supplier, for any contractual delivery of a HVDC project/equipment. It is expected that this document is used for pre-study and then to make studies, specification for delivery of specific HVDC project, as applicable.

General Information

• Status: Published
• Publication Date: 13-Jan-2025
• ICS: 27.180 - Wind turbine energy systems
• ICS: 29.020 - Electrical engineering in general
• Technical Committee: SC 8A - Grid Integration of Renewable Energy Generation
• Current Stage: PPUB - Publication issued
• Start Date: 10-Jan-2025
• Due Date: 14-Jan-2025
• Completion Date: 14-Jan-2025

Standards Content (Sample)

IEC TR 63411 ®
Edition 1.0 2025-01
TECHNICAL
REPORT
colour
inside
Grid connection of offshore wind via VSC-HVDC systems

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, graphical symbols and the glossary.
committee, …). It also gives information on projects, replaced With a subscription you will always have access to up to date
and withdrawn publications. content tailored to your needs.

IEC Just Published - webstore.iec.ch/justpublished
Electropedia - www.electropedia.org
Stay up to date on all new IEC publications. Just Published
The world's leading online dictionary on electrotechnology,
details all new publications released. Available online and once
containing more than 22 500 terminological entries in English
a month by email.
and French, with equivalent terms in 25 additional languages.

Also known as the International Electrotechnical Vocabulary
IEC Customer Service Centre - webstore.iec.ch/csc
(IEV) online.
If you wish to give us your feedback on this publication or need

further assistance, please contact the Customer Service
Centre: [e-mail].
IEC TR 63411 ®
Edition 1.0 2025-01
TECHNICAL
REPORT
colour
inside
Grid connection of offshore wind via VSC-HVDC systems

INTERNATIONAL
ELECTROTECHNICAL
COMMISSION
ICS 27.180; 29.020 ISBN 978-2-8327-0144-7

– 2 – IEC TR 63411:2025 © IEC 2025
CONTENTS
FOREWORD . 6
INTRODUCTION . 8
1 Scope . 9
2 Normative references . 9
3 Terms and definitions . 10
4 Practices and challenges . 10
4.1 Practices . 10
4.1.1 General . 10
4.1.2 Projects in North Sea, Germany. 10
4.1.3 Nan’ao project, China . 11
4.1.4 Hybrid Interconnector project, Belgium and Denmark . 12
4.2 Challenges . 12
5 Optimal planning . 13
5.1 General . 13
5.2 The core and key issues . 14
5.2.1 Planning process of offshore wind integration via VSC-HVDC . 14
5.2.2 Designing of offshore wind integration via VSC-HVDC . 15
5.3 Summary . 17
6 Coordinated voltage control . 17
6.1 General . 17
6.2 The core and key issues . 18
6.2.1 Coordinated voltage control . 18
6.2.2 Reactive power regulation replacement strategy . 20
6.3 Summary . 21
7 Coordinated active power control . 21
7.1 General . 21
7.2 The core and key issues . 21
7.2.1 Active power . 21
7.2.2 Coordinated active power control . 22
7.2.3 Frequency control . 25
7.3 Summary . 27
8 Fault response and coordinated control . 27
8.1 General . 27
8.2 The core and key issues . 29
8.2.1 Fault response in different kind of faults . 29
8.2.2 Duty segregation in fault response and coordinated control . 31
8.3 Fault control . 32
8.3.1 Optional fault ride-through technical solutions . 32
8.3.2 Technical requirements in coordinated control . 33
8.4 Summary . 33
9 Multi-frequency oscillation . 35
9.1 Problem statement . 35
9.2 The core and key issues . 35
9.2.1 General . 35
9.2.2 Impedance-based stability analysis method . 35
9.2.3 Impedance scanning analysis method . 38

9.2.4 Passivity analysis method . 39
9.2.5 Modal analysis method . 40
9.2.6 Electro-magnetic-transient simulation . 41
9.3 Multi-frequency oscillation suppression technology . 41
9.3.1 General . 41
9.3.2 Controller parameter optimization . 41
9.3.3 Control structure optimization and active damping control . 42
9.3.4 Passive filters . 42
9.3.5 Operational scenarios . 43
9.4 Summary . 44
10 Control and protection function verification . 45
10.1 Problem statement . 45
10.2 The key issues . 45
10.2.1 The C&P verification system . 45
10.2.2 Functions of C&P verification system . 46
10.3 The key verification and evaluation items . 48
10.3.1 General . 48
10.3.2 Verification for multi-frequency oscillation control . 48
10.3.3 Verification for AC fault ride through control . 48
10.3.4 Verification for energy-consuming control and protection device . 48
10.3.5 Verification for black start control . 49
10.4 Summary . 49
11 Testing and commissioning. 49
11.1 General . 49
11.2 Special scheme of testing and commissioning . 49
11.2.1 Process of testing and commissioning . 49
11.2.2 Joint commissioning . 51
11.3 The core and key issues . 51
11.3.1 The process and sequence of commissioning . 51
11.3.2 Offshore converter station test . 53
11.3.3 Dynamic braking system test . 54
11.3.4 Transmission commissioning . 55
11.3.5 Interaction commissioning . 56
11.4 Summary . 57
12 Black start . 58
12.1 General . 58
12.2 Black start process . 59
12.3 The core and key issues . 60
12.3.1 Black-start electric source configuration . 60
12.3.2 Establish the voltage and frequency of the offshore AC system . 60
12.3.3 Maintain the steady-state power balance of the offshore AC system . 62
12.3.4 Transient impact during the black-start process . 62
12.3.5 VSC-HVDC control . 63
12.3.6 Requirements for auxiliary equipment and secondary systems . 63
12.4 Summary . 63
13 Emerging innovative solution . 64
13.1 General . 64
13.2 The core and key issues . 64

– 4 – IEC TR 63411:2025 © IEC 2025
13.2.1 Offshore wind power integrated with DRU-HVDC transmission . 64
13.2.2 DC collection network for large offshore wind farm . 69
13.3 Summary . 71
14 Conclusion .
...