The Emergence of a New Era for the European HVDC Market

The push towards a carbon-free electrical power network is driving the growth in renewable energy generation. This, in turn, is driving the need for new electrical power transmission infrastructure to transfer power from the source of generation to where it is needed. Where the distances in transmission are long or where submarine or underground cables are needed (in the connection of offshore wind generation to the onshore AC grid, for example), High-Voltage Direct Current (HVDC) is often the economic choice. HVDC solutions that are suitable for the European market and compliant with European grid regulations require Voltage-Sourced Converter (VSC)-based technology. The technology being used today to build HVDC VSCs is based on Modular Multilevel Converter (MMC) technology, with the Transbay Cable project, commissioned in 2010, being the first commercial HVDC project to use this technology. This project had a rating of 400 MW, at ±200 kVdc, while projects that are currently under construction within Europe have ratings of 2000 MW, ±525 kVdc. In addition, new requirements are emerging within the European Union. In the recent Offshore Network Development Plan publication, three main priorities were set out: the need for a shift from point‑to‑point HVDC links to multi-terminal HVDC, the development and integration of HVDC circuit breakers, and the move towards interoperability between vendors. While we are all witness to the energy transition, these changes indicate the rapid development that has occurred in technology to-date and the continued need for innovation.

The European market is observing various requirements from different Transmission System Operators (TSOs) based on specific regional strategies and internal company-specific standards and, in some cases, the requirement for equipment to be subject to specific TSO homologation. To meet these requirements, HVDC vendors are expected to modify their reference designs, utilizing engineering time, and modifying the sub-system and component delivery needs. This inherently imposes a constraint on the throughput of the overall supply chain. To overcome this constraint, a standard technical specification for HVDC transmission systems could be adopted by the European TSOs. Such policy would reduce the engineering effort on both the TSOs, who no longer need to generate very detailed project-/region-specific specifications, and vendors, by relieving the effort on adapting their individual reference solutions. TSOs would further benefit from the integration between vendors to build multi-terminal HVDC-VSC solutions, as there will be a clear understanding of each HVDC-VSC specification.

As HVDC-VSC technology and network demands are both continuing to develop, it is recognized that any standard European HVDC-VSC specification must also be able to adapt, but it is suggested that any such changes would be introduced in a collaborative change approval process between European TSOs and vendors.

To remain competitive within both the global and European market, it is critical to continue to innovate our solutions offering. The European HVDC specification needs to be functional, defining performance and constraints of equipment at boundaries, like the converter island defined as the scope of equipment between the AC and the DC point of connection with the AC feeder and the DC switching station. It is recognized that some requirements, not directly related to the functional performance of the HVDC-VSC solution, may not be within the scope of the TSOs to standardize. It is therefore proposed that such elements of the total project are removed from the scope of supply of the HVDC-VSC specification but, rather, the standard specification should have a defined interface to these elements.