IFC Software: Control Concept for Expandable Multi-Terminal HVDC Transmission Systems


Generally, the conventional HVDC grid control concept considers a single vendor implementation, with a single link implementation. However, in reality, different vendors might participate in developing multi-terminal HVDC (MTDC) systems, enabling DC transmission system operators (DC-TSOs) to select and implement the best and most cost optimal solution for an interconnected HVDC based grid between e.g. the countries surrounding the North Sea.

This IFC control concept can be used to achieve this. Each TSOs can integrate the software into their internal analysis environment, and use it to help define the specifications for future Tenders on new HVDC and MTDC links, to ensure interoperability of new additions to their grid. Further, based on received proposals from Vendors, the TSOs can use the software concept to validate black box solutions provided from Vendors as part of their proposals, so it is clear whether a proposed solution has a good fit with the tender Specifications, at the time the offer is made. And even if not, provide a starting point for discussions, to secure delivery of systems that integrate well into the existing grid before a Vendor is chosen.

Likewise, this IFC control concept may be used by system Vendors to validate their own Black Box before tender, securing a good fit to required specifications in the proposals made. Finally, to achieve an easy integration with systems from other vendors, the vendors could potentially implement this type of control, to secure their own system interoperability with systems from other suppliers.

This can be achieved, without changing the converter control of existing products, by adding the proposed concept as an additional control layer (IFC), compared to the conventional DC grid control concept, which is used to interface between the centralized MTDC control and localized converter control. By using the IFC on top of existing controls from various vendors, the only requirements for the converters to be interconnected with each other, are that the DC voltage control (UdcCtrl) is available, and that the reference for this control, is adjustable. Hence, the IFC simplifies the interconnection requirements and supports easy realization of multi-vendor MTDC systems.

  • In principle, the power flow within the DC grid can be controlled by controlling the DC voltage in each terminal of the converter. The DC voltage control is usually available in each of the link.

  • The IFC software produces an appropriate DC voltage reference, such that the converter can be operated to follow a certain characteristic, e.g. to mimic the active power control or DC voltage droop control.

  • The behavior of the existing DC voltage control can be modified by using the phase compensator component within the IFC software. Furthermore, the droop shift part is used to integrate the AC grid control such that the converter can be operated in fully AC-DC grid control.

Easy implementation without altering the existing converter control

In the North Sea region, there are several HVDC links from various vendors already in operation or currently being developed. The offshore wind installations are expected to grow and meet at least 13% of the electricity demand in Europe by 2030. Further, with the plans to build Energy Islands off the coast of Denmark, a DC grid will be developed, and provide the most suitable way to transport the offshore wind power to the European continent. It is envisioned that in the near future, an MTDC system emerges by interconnecting some of these links or adding a new offshore wind farm converter to an existing link. The COBRAcable connection between Denmark and the Netherlands, is already prepared for this.  

With the proposed approach, developed in the COBRAcable project, the DC grid control can be implemented without altering the existing converter control. Hence, lowering the investment cost for realizing the MTDC system for the DC-TSO, and enabling the system suppliers to utilize their current HVDC link concepts, without change in the MTDC system, by utilizing the IFC software as the core part of the solution.


The IFC software has been implemented as an external function in simulation programs like PSCAD and PowerFactory. This means that the IFC software is ready to be used by DC-TSO’s and System Vendors to perform simulations during the feasibility studies of new HVDC/MTDC links. With the IFC software, vendor-specific black-box models, which has DC voltage reference input, are sufficient to be used for the simulations to validate whether an HVDC link from a specific vendor can be used as part of an MTDC system, utilizing the IFC software, and thus meet the basic operational requirements from the DC-TSO.

The IFC software is already licensed non-exclusive to Energinet in Denmark, and open for licensing for other TSOs as well as System Vendors.

AAU Tech ID: 2018-521/10-0684


If you are interested in testing or licensing the IFC software, please contact:

Lars Halkjær
Technology Transfer Manager
Phone: +45 9940 7343
E-mail: lah@adm.aau.dk

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