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PROMOTioN - Progress on Meshed HVDC Offshore Transmission Networks

Periodic Reporting for period 3 - PROMOTION (PROMOTioN - Progress on Meshed HVDC Offshore Transmission Networks)

Okres sprawozdawczy: 2018-07-01 do 2020-09-30

Offshore wind energy will play a significant role in the European Green Deal. In the North Sea a total of over 200 GW of generating capacity could be built by 2050. Transporting this amount of power to shore and integrating into the onshore grid is a challenge, requiring high levels of interconnection between the countries.

Due to the remote locations of offshore wind farms (OWFs), traditional high-voltage alternating current (AC) transmission is no longer viable and high-voltage direct current (HVDC) connections must be utilised. Previous research projects have indicated that the most socio-economically beneficial implementation of such a grid is a coordinated meshed HVDC offshore transmission network.

To-date however, HVDC systems in Europe have been mainly implemented as separate point-to-point links under a single vendor, single purpose and single owner paradigm, due to immature HVDC network technology solutions, differences in national legal and regulatory frameworks, and an absence of a suitable economic framework.
The EU funded Horizon2020 project PROMOTioN ‘Progress on Meshed Offshore HVDC Transmission Networks’ project has addressed the technical, legal, regulatory, economic and financing challenges in the development of a meshed offshore HVDC transmission network in the North Sea by achieving six objectives:

1. To establish interoperability between different technologies and concepts by providing specific technical and operational requirements, behaviour patterns and standardization methods for different technologies:
- Focussed on four key technologies: HVDC network and OWF control, HVDC network protection, HVDC circuit breakers and HVDC gas insulated substations
- Defined common functional requirements for multi-terminal HVDC systems and OWFs
- Researched, simulated and compared the techno-economic performance and interoperability of meshed HVDC network topologies with different combinations of key technologies
- Developed guidelines for technology selection and equipment specification
- Developed recommendations to achieve compatibility and interoperability on regulatory, technical and contractual levels

2. To develop interoperable, reliable and cost-effective technology of protection for meshed HVDC offshore networks and the new type of offshore converter for wind power integration:
- Defined common performance requirements for HVDC network protection
- Created cost models and database for HVDC equipment and carried out a comprehensive lifetime cost and benefit analysis (CBA)
- Developed, tested and validated an Intelligent Electronic Device (IED) which can be programmed with various HVDC network protection strategies
- Developed a common system interface between different protection system components
- Demonstrated vendor interoperability through the successful operation of PROMOTioN’s and an industrial vendor’s IED with another industrial vendor’s converter control & protection replicas
- Carried out stress and failure mode analysis of HVDC circuit breakers
- De-risked grid forming operation of OWFs, providing functional requirements, compliance procedures and grid code recommendations
- Developed, implemented and validated generic and vendor-specific grid forming controllers for self-energization and black-start of OWFs

3. To demonstrate different cost-effective key technologies for meshed HVDC offshore networks and to increase their technology readiness level by investigating and overcoming early adopter issues and pitfalls:
- Developed technology performance qualification procedures and test circuits
- Carried out full-power, full-scale and/or full-functionality demonstrations of industrial prototypes of all key technologies delivered by vendors at independent industrial test laboratories
- Carried out numerous lower-power, lab-scale and simulation-based technology demonstrations
- Performed a dedicated technology readiness level (TRL) progress analysis of all key technologies and determined that they have been advanced to a TRL of 6 or higher

4. To develop a new EU regulatory framework, both in accordance with EU wide energy policy objectives and those of the Member States, and to increase the economic viability of meshed HVDC projects by providing a suitable financial framework:
- Performed a study of international, European and national law and developed specific recommendations for identified gaps
- Proposed a definition for a new type of assets for OWFs connected to more than one country
- Developed a methodology for socio-economic CBA for offshore transmission system development
- Developed recommendations for offshore network planning, operation and decommissioning
- Developed an offshore market design based on small bidding zones with additional measures to ensure stable revenue for OWF developers
- Made recommendations for the required investment volumes, ownership and income models, cross-border cost allocation and suitable financing strategies

5. To facilitate the harmonisation of ongoing initiatives, common system interfaces and future standards by actively engaging with working groups and standardisation bodies and actively using experience from the demonstrations:
- Inventoried all active and relevant standardisation initiatives and established liaisons
- Organized targeted harmonisation workshops on different topics
- Developed and shared specific information packages with standardisation initiatives. Test results of the demonstrators have been shared to actively drive and shape standardisation

6. To provide a concrete deployment plan for “phase two” in bringing key technologies for meshed HVDC offshore networks into commercial operation in Europe, taking into account technical, economic, financial and regulatory aspects
- Developed network topologies based on offshore wind roll out and international coordination
- Performed a comparison based on the cost and benefit analysis for the developed topologies
- Created a roadmap with necessary stakeholder actions and timing targeted at the 2050 goals
- Carried out feasibility studies of three short-term opportunities for multi-terminal HVDC pilot projects
Final conclusions
PROMOTioN concludes that there are no technological showstoppers for multi-terminal HVDC transmission network. Significant standardisation work is still required to enable multi-vendor HVDC network. TSOs and vendors need to align on common, technology-neutral functional performance requirements, communication protocols and standards for HVDC equipment. Procurement and contractual practises must be adapted to enable multi-vendor system integration.

Collaboration and coordination between national governments, TSOs and other offshore space users is key to aligning national offshore renewable energy plans with transmission planning. The best way to overcome the remaining challenges is through the realisation of a full-scale cross-border pilot project to demonstrate the technology’s viability and international collaboration models and deliver the socio-economic benefit of multi-terminal HVDC transmission systems.

The PROMOTioN results have been extensively disseminated through publication in international conferences as well as through targeted topic driven workshops with key stakeholders such as National ministries, DG Energy, ENTSO-E, WindEurope, T&D Europe and the North Sea Wind Power Hub. The public deliverables and presentations are available on