HVDC Moves From Niche to Mainstream
High-voltage direct current (HVDC) transmission has traditionally been treated as a specialty technology, reserved for extremely long overhead lines, subsea cables, or particularly difficult grid interconnections. That era is ending. During a recent episode of the Redefining Energy podcast, Cornelis Plet, Chief Technology Officer for Grid Systems Integration at GE Vernova, described HVDC as a technology that is joining the normal transmission planner's toolbox rather than sitting on the sidelines as an exotic proposal.
This shift is driven by the accelerating energy transition. As renewable energy sources such as offshore wind and large-scale solar expand, they often connect to demand centers that are far away or separated by water. HVDC offers lower losses over long distances and the ability to control power flows precisely. With conventional power plants retiring, HVDC is also being called upon to provide stability services that rotating machines once supplied.
Hardware Standardization: The 2 GW Building Block
The most visible sign of HVDC's maturation is physical standardization. According to Plet, the European market is converging on 2 gigawatt (GW), 525 kilovolt (kV) systems as a repeatable building block. These systems use common converter configurations and bipolar designs. Other regions are developing their own patterns, including 3 GW projects planned in the United States and India.
This repetition is transformative for the supply chain. Manufacturers of converters, cables, transformers, and other components can build around a product family instead of engineering every project from scratch. Standardization shortens lead times, lowers costs, and improves reliability because suppliers gain experience with identical or similar equipment. It also simplifies permitting and grid integration, as regulators and system operators become familiar with the technology.
The Control Gap: Grid-Forming Converters Lack Global Standards
While the hardware is becoming standardized, the electrical system around those converters is not. As more generation connects through power electronics, transmission systems must do more than deliver bulk electricity. Converters are increasingly expected to help stabilize the grid by providing services such as voltage support, frequency regulation, and damping. Grid-forming control is emerging as a key capability for HVDC systems.
However, Plet was careful to note the current state of standards for these controls. There is not yet one coherent global definition of how grid-forming behavior should be implemented. Requirements differ by grid code and regional practice, forcing vendors to maintain multiple control variants and system operators to reconcile incompatible behavior. This creates additional engineering effort and raises the risk of unexpected interactions.
Multi-Terminal and Multi-Vendor Interoperability
The control challenge becomes even more acute as Europe moves from point-to-point HVDC links to multi-terminal and eventually multi-vendor HVDC networks. Offshore wind farms in the North Sea, for example, are likely to be connected through a meshed grid rather than individual radial lines. In such a system, a converter station from one supplier must communicate and cooperate with equipment from another supplier.
Interoperability is not simply a matter of agreeing on voltage and power levels. Control modes, protection schemes, communication protocols, and even intellectual property must be aligned. Vendors may be reluctant to share proprietary details, yet without common standards, the system cannot guarantee stable operation under fault conditions. This is one of the most difficult technical and commercial hurdles facing HVDC grid expansion.
Lessons From PROMOTioN and Future Research
Plet previously led PROMOTioN, a major European research and demonstration program focused on meshed offshore HVDC technology. That project advanced the state of the art in direct current circuit breakers, protection strategies, and multi-terminal control. It proved that such systems can work, but it also highlighted remaining gaps. Follow-on initiatives are now addressing those gaps with increased focus.
The research community and industry have learned that hardware standardization alone is insufficient. To fully realize the benefits of HVDC, grid codes must evolve to accommodate new control schemes, and utilities must adopt planning methods that treat multi-terminal networks as an integrated system rather than a collection of separate assets. The technology is ready; the surrounding grid architecture is still catching up.
Regional Differences: Europe, United States, and India
Europe's move toward 2 GW, 525 kV building blocks contrasts with the larger 3 GW projects being developed in the United States and India. These regional differences reflect varying transmission distances, load densities, and renewable integration targets. In the United States, long-distance interconnections between renewable-rich regions and population centers are becoming more common, driving the need for higher capacity HVDC links. India is similarly investing in HVDC to move power from its solar and wind corridors to high-demand areas.
While the hardware may differ, the control challenges are universal. In every region, grid-forming control requirements are still being defined, and multi-vendor interoperability remains a work in progress. The industry has not yet settled on a common framework for how converters should behave during normal operation and disturbances.
Key Takeaways
- HVDC is now a mainstream technology for transmission planners, not a niche solution.
- European markets are standardizing on 2 GW, 525 kV HVDC systems, with 3 GW projects in the US and India.
- Grid-forming controls are becoming essential, but global standards are absent.
- Multi-terminal and multi-vendor HVDC grids face significant interoperability challenges.
- Research programs like PROMOTioN have demonstrated feasibility but also revealed gaps that require continued effort.
The Road Ahead
The transition to a grid built on HVDC is already underway. The hardware is becoming more standard and more affordable, but the surrounding system—the controls, codes, and planning practices—is still evolving. Bridging this gap will require collaboration among utilities, regulators, vendors, and researchers. Without common standards for grid-forming behavior and multi-vendor interoperability, the full promise of HVDC will remain unrealized.
The next decade will likely see HVDC become as common as AC transmission in many parts of the world. But the successful integration of these systems depends on solving the puzzle of the grid around them. As Plet and his colleagues have emphasized, the technology is ahead of the infrastructure that surrounds it. The question is how quickly the rest of the grid can catch up.
This article is based on reporting by CleanTechnica. Read the original article.
Originally published on cleantechnica.com
