The multiDC Project
The project “MULTI-DC: Innovative Methods and Optimal Operation of Multiple HVDC Connections and Grids” (multiDC) applied in 2016 for funding under the Innovation Fund Denmark framework of “Grand Solutions”. Due to the high number of HVDC connections in the Nordic region, this call pursues new and advanced control solutions to fully employ the benefits HVDC connection has to offer. The specific objective of multiDC project is to develop innovative methods for the optimal coordination of multiple HVDC lines and HVDC grids in systems with high shares of renewables. To achieve this highly ambitious result, multiDC teamed up with established researchers, technology providers, and end customers
Our focus
Dynamic Security
The increase of inverter-based generation is phasing out grid-connected generation units, which provide various system services, such as Short Circuit Capacity (SCC), frequency control and rotational energy. Moreover, the clustered renewable generation requires facilitation of huge power influx in a power system, which becomes increasingly challenging for TSOs to control. Due to high controllability and bulk power transmission capability, HVDC technology is a promising replacement to provide such services and help stabilizing the system. To ensure the feasibility of such transition, stability analysis needs to be conducted for low and zero inertia systems, and advanced converter control design should be employed.
Optimal operation
In the last decades, HVDC technology has become a common tool in the design of transmission grids. From a technical point of view, the full controllability of power converters gives the opportunity of supporting local AC networks by means of voltage control, frequency support and reactive power compensation. On the economic side, HVDC interconnectors facilitate the exchange of energy and ancillary services between countries. Thus, if HVDC and AC grids are operated in an optimal way, significant cost and energy savings can be achieved. The scope of this project is to benchmark current markets and to propose various path for their evolution in order to unleash the potential of HVDC lines.
Emergency Control
HVDC connections will play a key role in an efficient and secure operation of the future system, mainly due to their capability to bulk power transmission over long distances and for fast, flexible control. Today the operation of multi HVDC connections is not coordinated during disturbed system operation. This project’s primary goal is to enable HVDCs active participation in AC system frequency stability by developing advanced control actions. Moreover, these control actions should be carefully coordinated to avoid negative interaction with other stability types and operation factors in all interconnected systems. The aim is to use the current power system infrastructure, without implying large additional investment costs.
Implementation and testing
To analyse the North Sea Wind Power Hub offshore grid stability, and HVDC effective utilization in market operations and emergency control, an environment for testing must be established. This process is separated into two stages: online testing using powerful simulation tools, and hardware-in-the-loop implementation in state-of-art facilities across Denmark. The primary tool for online testing is DigSilent PowerFactory, used to develop Kriegers Flak interconnector, NSWPH, and detailed Nordic Test System models. Once our methods prove viable the implementation is taken to PowerLabDK Real-Time-Digital-Simulator, and, finally, reaches the transmission system operator’s SCADA control room.
Our Team

Jacob Østergaard

Spyros Chatzivasileiadis

Fitim Kryezi

Robert Eriksson

Thierry Van Cutsem

Jenny Josefsson

Mehrdad Ghandhari

Tilman Weckesser

Georgios Misyris

Matas Dijokas
