The new distribution and transmission grid as described in the WP1 and WP2 sections, requires the deployment of innovative technologies that will enable the operation of the grid. Multi-terminal DC transmission is not yet commercially used, but it is anticipated to be a relevant option for the system expansion or reinforcement in the near future. Additionally, the principles and technologies for isolating and accurately detecting the faults clearly differ from existing AC solutions.
Three classes of High Voltage Direct Current (HVDC) breakers have been discussed in the literature: mechanical, static and hybrid. Fast measurement and fault detection systems for HVDC are not yet available and none of these principles has yet been demonstrated at the required ratings. Similarly, fault-tolerant HVDC converters have been proposed, but they are not used as current commercial products.
Further research activities are also required in modular power electronic converters while in mixed frequency insulation material, the effects of the dielectric stress distribution will become an increasing hindrance in the future grids. However, our current understanding of these effects is limited.
- multi-terminal HVDC system design and operation;
- fault detection and clearing in multi-terminal HVDC;
- enabling technologies.
WP3’s objective include:
- Standardisation work (including procedures) allowing to accelerate Switzerland’s connection to multi-terminal DC networks,
- Facilitation of the emergence of a common DC fault management concept for the European interconnected network,
- Investigation of key power electronic technology issues to be solved in order to establish cost efficient and reliable converters for transmission applications.
Activities Phase II
S 3.1 Multi-terminal HVDC system design, testing and operation
Subtask leader: 2.6 ETHZ-HVL, Prof. Franck
S 3.1 Milestones
|2.4 ETHZ-HPE, Prof. Biela||[Jun. 2018]|
|M3.1.2 Enhanced dynamic controller concept ready||2.4 ETHZ-HPE, Prof. Biela||[Dec. 2018]|
|M3.1.3 Installation of full-scale test source||2.4 ETHZ-HPE, Prof. Biela||[Dec. 2020]|
|M3.1.4 Operation and design concepts for coordinated ACDC networks||4.1 HES-SO-EIA-FR, Prof. Favre- Perrod||[Dec. 2020]|
S 3.2 Fault detection and clearing in multi-terminal HVDC
Subtask leader: 1.10 EPFL-EMC, Prof. Rachidi
S 3.2 Milestones
|M3.2.1 Ultra-Fast disconnector built and experimentally characterized||2.6 ETHZ-HVL, Prof. Franck||[Aug 2018]|
|M3.2.2 Prototype of the fault locating device||1.10 EPFL-EMC, Prof. Rachidi||[Dec 2018]|
|M3.2.3 Hybrid circuit breaker system build and performance experimentally measured||2.6 ETHZ-HVL, Prof. Franck||[Dec 2019]|
|M3.2.4 Deployment of the system in a substation of the Romande Energie demonstrator and performance analysis||1.10 EPFL-EMC, Prof. Rachidi||[Dec 2020]|
S 3.3 Enabling component and converter technologies and applications
Subtask leader: 4.2 HES-SO-IESE, Prof. Carpita
a) development and demonstration of highly flexible, modular and scalable direct current transformer technology platform for medium voltage direct current grids, integrating advance control and protection features (“GIMC converters”). Study of the MVDC grids stability, considering converter interactions and active load sharing
b) fault and power flow management in active distribution grids by using a soft open point (in cooperation with Romande Energie)
c) the development and demonstration of a framework for the provision of ancillary services in systems with high RE penetration
d) the development of a toolbox for optimized medium-voltage medium-frequency solid-state transformer This will include the deployment of a soft open point first in the FURIES AC/DC lab network and subsequently in the Romande Energie demonstrator in cooperation with S3.2, which will provide the fault detection needed for the operation of the device.
S 3.3 Milestones
|M3.3.1 Development of a design toolbox for solid-state transformers||2.5 ETHZ-LEM, Prof. Kolar||[Dec 2017]|
|M3.3.2 DC transformer concept developed||1.8 EPFL-PEL, Prof. Dujic||[Dec 2017]|
|M3.3.3 Stability of MVDC laboratory demonstrator established||1.8 EPFL-PEL, Prof. Dujic||[Dec 2018]|
|M3.3.4 Laboratory test of soft-open point prototype||4.2 HES-SO-IESE, Prof. Carpita||[Jul 2019]|
|M3.3.5 Laboratory demonstration of core functional parts of an optimized SST||2.5 ETHZ-LEM, Prof. Kolar||[Dec 2020]|
|M3.3.6 Field test soft-open point prototype demonstrated||4.2 HES-SO-IESE, Prof. Carpita||[Dec 2020]|
Storage system in MV for grid auxiliary services
Innovative interface of storage systems for MV applications, making use of modular converters and avoiding the 50Hz main transformer
Fault clearing in multi-terminal HVDC
For the safe operation of future HVDC multi-terminal grids, HVDC circuit breakers are a key component. Advances in HVDC switching technology will enable the Swiss energy industry to take a leading role in the world-wide transition from fossil to renewable energy sources.