PROMOTioN's Digital Capstone Event, 08/24/20  - 09/21/20

Breakout Session 1: Offshore HVDC Grid Technology

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This week our Breakout Sessions will focus on the detailed technical work regarding HVDC Grid technology within the PROMOTioN project.  The technical work packages within PROMOTioN have progressed the understanding of technical design choices for future multi-terminal HVDC systems, with regard to different converter types and their control, DC fault clearing strategies, DC circuit breaker technologies, the control of the offshore windfarms and the overall system integration and operation of these components under a broad variety of system conditions.

KEYWORDS: HVDC System Control & Operation | Diode rectifier integration | Grid Forming OWF Controls | Frequency Support | Black Start | AC-DC system interaction | DC CB technology and modelling | Grid protection concepts | Cost-benefit analysis of protection concepts | Standardisation and grid codes | HVDC GIS technology and demonstrator

CHAIR: Christina Brantl, RWTH Aachen

Work package 2 (WP2) of PROMOTioN on “Converters and Topologies” was set-up to investigate the interconnection of different converter types and possible future HVDC offshore grid topologies to derive recommendations on onshore and offshore power systems for existing grid codes.  
The work package encompassed a broad range of studies on possible grid topologies including different converter technologies, e.g. half-bridge and full-bridge MMCs and diode rectifier units. The interaction of these converters within the system and with adjacent AC systems, like onshore synchronous grids and the offshore wind farms were studied under different operation and fault scenarios to identify the typical behaviour of the HVDC system, improve the overall system performance and identify persistent challenges.

WP3 focused on de-risking the Diode Rectifier Unit (DRU) based offshore transmission concept. In doing so, it defined requirements, developed grid forming controls, defined and tested compliance evaluation procedures and paved the way to the demonstration done in WP16. Furthermore, with the developed grid forming controls, WP3 performed extensive simulation studies of black-start capabilities and strategies from offshore wind, with both academic and vendor specific controllers. Using the knowledge created, WP3 provided grid code recommendations for DRU connected OWPPs to WP11.



HVAC connected OWPPs - Ramon Blaso Gimenez (UPV)
Simulations for HVAC connected OWPPs - Anubhav Jain (DTU)

This WP aimed to further develop the most appropriate DC grid protection methodologies for various system topologies. The WP investigated different protection strategies, in combination with different fault clearing methodologies, for different DC grid concepts. Risk-based tools to evaluate different protection strategies to derive the most optimal DC grid protection based on technical and economic considerations were developed. Within the WP, an Intelligent Electronic Device (IED) was developed, and the necessary tests were implemented to validate the different methods in the DC grid demonstrator of WP 9. WP 4 also prepared input for WP 11 (standardisation) and WP 12 (roadmap).




Functional specs of DC grid protection - Kamran Sharifabadi (Statoil)
DC grid protection: algorithms and protection strategies - Willem Leterme (KU Leuven)
Failure modes & KPI of DC grid protection - Alberto Bertinato (Supergrid Insitute)
The open source Promotion HVDC relay - Ilka Jahn (KTH)

Converter breaker strategy - Pascal Torwelle (Supergrid Insitute)
Full-bridge converter protection strategy - Philipp Ruffing (RWTH Aachen)
Post-fault pole rebalancing - Mian Wang (KU Leuven)
Multi-vendor HVDC grid protection - Mian Wang (KU Leuven)
Backup protection - Mian Wang (KU Leuven)


CBA methodology - Serge Poullain (Supergrid Insitute)
Link between AC desing and DC grid protection - Jaykumar Dave (KU Leuven)
CBA of HVDC grid protection: outcomes - Serge Poullain (Supergrid Insitute)

This WP studied in depth commercial DC CB topologies. It complemented DC CB demonstration activities in WP5 and WP10, since it developed software models that can be used for fast and flexible studies of DC CBs. Some DC CB technology advances have been proposed and experimentally verified on lab-scale DC CB demonstrators. WP 6 further provide real-time DC CB models for DC grid demonstration in WP9.



Semere Mebrahtu-Melake
Hybrid DC CB, technology, modelling and integration in Tennet DC system
Linash Kunjumuhammed
Current injection DC CB, technology, modelling, scaling and integration in Tennet DC system
Simon Nee and Marjan Popov
VARC DC CB technology, modelling, scaling and integration in Tennet DC system

Marjan Popov
Real time Mechanical DC CB model
Dragan Jovcic
Real time Hybrid DC CB model

Mario Zaja
DC CB simplified models and DC CB Test circuit
Mario Zaja

DC CB Failure mode study

Dragan Jovcic
DC CB research and new topologies

The overall objective of WP11 was to support and establish harmonization of the industry’s best practices, standards and requirements for HVDC systems and HVDC connected offshore wind power plants. WP 11 aimed to ensure that the experience collected through the project – including research and engineering in WP 2-6, as well as engineering and demonstrations in WP 9-10 and WP 15-16 – is utilised in ongoing and future standardisation work.



HVDC gas-insulated systems have a much smaller clearance distance than air-insulated systems and can be built with a much higher degree of compactness and significantly lower sensitivity to ambient factors. The most obvious cost-saving potential can be found on offshore converter platforms which are currently implemented as air-insulated systems. WP 15 was set-up to aims to develop recommendations for specifying gas-insulated HVDC systems and to develop testing requirements, procedures and methods based on simulation analysis, real HVDC onshore and offshore experiences, and also based on CIGRE work. This leads to the need for long-term tests on gas-insulated HVDC systems in general. Long term testing of full power HVDC GIS were carried out according to developed test requirements and procedures and using developed monitoring and diagnostic methods. Users intending to employ gas-insulated HVDC systems expect high reliability and long-term performance. Monitoring and diagnostic methods for HVDC GIS were developed to ensure a safe operation. Monitoring methods are also evaluated for SF6 alternatives.



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