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Multi-terminal DC grid for offshore wind

Final Report Summary - MEDOW (Multi-terminal DC grid for offshore wind)

MEDOW was a Marie Curie Initial Training Network which appointed 17 early career researchers to receive broad-ranging training and development in the exciting new field of multi-terminal DC grids for offshore wind power.

Renewable power is essential for Europe to meet energy demand and reduce carbon emissions. Offshore wind offers many advantages over other forms of renewable energy, including high yield of power and lack of disruption to landscapes or noise pollution. High Voltage Direct Current (HVDC) will be the key technology for integrating offshore wind power into AC (alternating current) main grids and for interconnecting European countries’ AC grids. HVDC transmission offers efficient transmission of large amounts of power over long distances. Development of DC transmission has gained significant momentum as a result of two key drivers. Firstly, the development of modern power conversion technology (voltage source converter) and secondly, the need for transmission of offshore wind power. Plans for the interconnection of multiple renewable power sources, loads and AC grids through DC technologies are leading to the exciting transmission concept of HVDC grids. If Europe is to take advantage of the environmental and economic opportunities offered by offshore wind power, HVDC grids and of the significant potential for the creation of a European energy ‘Supergrid’, research expertise, both in the private sector and in universities and research institutes, must be developed.

The primary aim of MEDOW has therefore been to train talented young researchers within a multi-disciplinary network of top academic and research-focused industrial organisations across Europe and in China. This ‘training through research’ has equipped them with the expert knowledge, tools and skills to leave the project as highly employable researchers ready to embark on successful careers with impact and to contribute to Europe’s future society, economy and environment.

Comments from researchers on their experiences in MEDOW include:

“This project gave me the opportunity to work in a different country and with an international environment where I learnt different ways to work and collaborate with other researchers and academics. This is particularly important in HVDC and offshore wind power research due to the limited number of people working in this area.”

“It was a unique and great opportunity that I was granted the chance of collaborating with MEDOW researchers and supervisors. Therefore, the extensive professional network that I have created during my MEDOW fellowship is one of the most valuable outcomes, which will have a long-term impact on my future career.”

“The most significant trainings provided during the project meetings and MEDOW weeks were on so-called soft skills and specifically on presentation skills. Such training activities are unique compared to conventional doctoral programs and will have surely a positive impact on the future career specifically in terms of self-confidence in new environments, presentation situations and networking events.”

Project funds from the European Commission supported researchers’ salaries and their training and development in the form of wide-ranging technical and complementary training. Funds also supported the recruited researchers to disseminate and communicate their work in a variety of ways. Researchers communicated their results within the scientific community through over 25 articles in international peer-reviewed journals, over 75 presentations at international conferences and workshops, in 5 book chapters and 1 patent application. Researchers made over 30 presentations to various power systems and offshore wind power industry bodies. A substantial outreach schedule, with over 30 outreach activities, aimed to communicate MEDOW beyond the power grids research community, and included researchers taking part in high school science weeks, teaching MSc classes and presenting the project to the general public. All fellows made individual contributions to the outreach programme.

Training received by MEDOW and other researchers included: a visit to a wind turbine manufacturing plant, a talk from the CEO of Friends of the Supergrid, a Wind Power summer school, lectures from high profile Visiting Scientists of international standing in their field, a visit to an offshore wind farm and workshops in entrepreneurship and personal impact. Whenever possible, researchers from outside the network were invited to participate for free in training activities.

The network’s second aim was to make meaningful research progress and generate new knowledge in DC grids and offshore wind power, building our network of people and organisations. New links and cross-sectoral collaborations have been forged and it is anticipated that our network of partners, with its extended network of other collaborators, will be sustainable into the coming years as momentum builds in the area of DC grids. Research activities and achievements include:

• Determination of DC grids suitable for offshore wind power and of characteristics of necessary converters;
• Development of algorithms for determining operating points;
• Development and use of a digital wind farm model for testing variable configurations and topologies;
• Development of a wind power reduction method;
• Development and validation of 2-Level and half-bridge and full-bridge modular multilevel converter (MMC) models;
• Comparison of different cell solutions for MMC including economic/technical comparison using proper index and comparison methods;
• Study of the influence of converter station configurations on DC Voltage Restoration Reserve (DCVRR);
• Analysis of DC grid faults and development of DC protection algorithms and post-fault restoration schemes;
• Investigation of the effects of DC grid faults on AC transmission power protection with high penetration of DC grids. Validation and testing of the outcomes in a closed-loop test with RTDS simulator, power amplifier and a commercial AC transmission relay;
• Design, development and testing of the prototype so-called Ultra-Fast Solid-State DC Circuit Breaker;
• Application for patent protection for a ‘Fault Current Managing Branch for Surge-less current interruption in DC System’;
• Analysis of interactions between offshore wind farms and AC power systems with the objective of providing ancillary services;
• Determination of adverse interactions of HVDC converters with AC systems in the sub-harmonic (SSR) frequency domain and controller induced resonances at higher frequencies;
• Investigation of HVDC grid behaviour in the presence of AC faults;
• Implementation of developed algorithms on laboratory test platforms.

The MEDOW team has sought to communicate what it has achieved and discovered to a variety of audiences. In April 2016, the consortium hosted an international conference day on ‘Offshore Wind and HVDC Grids’ with Brussels-based Friends of the Supergrid at the 2016 IEEE EnergyCon conference at KU Leuven, Belgium. The project was honoured to be given part of the programme of this prestigious international conference. MEDOW researchers had the opportunity to present their findings to an audience of power systems stakeholders, giving maximum exposure to their work and allowing them to make contacts and engage with other university groups, private companies and transmission system operators.

MEDOW co-hosted the Annual HVDC PhD Colloquiums at KU Leuven in 2013, at Danmarks Tekniske Universitet in 2015 at the Universidade do Porto in 2016. It plans to continue its legacy of community building in DC grids research though the next HVDC Colloquium September 2017 and through a summary report of project results that will be available for free download via the project website.

The website ( is a repository of public information about the project’s results and activities. Articles on MEDOW have appeared in around 30 different energy and general interest websites, newspapers and magazines including Offshore Wind Journal, Wind and Wave Connect magazine, Wales Online, The Time of India and the Friends of the Supergrid newsletter. In November 2016, MEDOW was profiled in the European Commission’s Research EU Results magazine. In September 2016, MEDOW was showcased in a report by Universities UK International, with support from the UK’s Department of Business, Innovation and Skills. The report was launched by Jo Johnson MP, UK Minister of State for Universities and Science. The report praises MEDOW for its impact, particularly that of linking industries across borders, providing opportunities for future collaborations and contributing to an international framework for the development of a pan-EU power grid. In December 2015, MEDOW featured in the brochure of the 7th European Innovation Summit, which was organised by the Knowledge 4 Innovation forum of the European Parliament. The project featured as an example of how research and development is contributing to transforming the energy sector in Europe. A full record of media coverage and outreach activities is available on the website.
The academic and industrial offshore wind grids communities benefitted not only from the research findings of the project but also from the potential to recruit highly skilled researchers with cross-border experience in both universities and the private sector. The project has contributed to the European Research Area by building and structuring a community of complementary partners to work together in Europe to advance collection and transmission of clean energy.
The MEDOW project’s training and research efforts have been evaluated as a very positive addition to European progress towards large-scale integration of renewable power sources. However, the network has also showed that more training actions of this type in the field of HVDC grids and transmission are urgently needed in order to provide Europe with a sustainable energy future and to keep it competitive on the international scene. The consortium is delighted that it is due to sign a new grant agreement with the European Commission to run a second Marie Skłodowska-Curie European Training Network, InnoDC, due to start in late 2017 and to offer another high quality training and learning experience for promising your researchers in the field of offshore grids.

Contact: Scientist-in-Charge, Dr Jun Liang -