The Transmission Technology That AC Cannot Replace for Long Distances
High-voltage direct current transmission uses direct current rather than the alternating current that the majority of the world's electricity grid infrastructure employs, exploiting the physical properties of direct current transmission that make it superior to AC for specific grid applications despite requiring the converter stations at each end of the transmission link that convert the AC power from the generation source to DC for transmission and back to AC for injection into the receiving grid. The advantages of HVDC over AC transmission emerge in three specific contexts whose commercial significance is growing as the renewable energy transition expands the geographic mismatch between where renewable electricity is generated and where it is consumed. For very long transmission distances exceeding approximately six hundred kilometres in overhead lines or approximately sixty kilometres in submarine cables, HVDC's lower transmission losses per kilometre than AC at equivalent voltage level create the energy efficiency advantage that makes HVDC the economically preferred option for the long-distance power transport that connects distant renewable resources to population centres. For submarine cable transmission whose capacitive charging current in long AC cables consumes an increasing fraction of the cable's thermal capacity as length increases, limiting practical AC submarine cable transmission to distances below approximately sixty kilometres, HVDC submarine cables whose direct current eliminates the capacitive charging current can transmit power over submarine cable distances of hundreds to thousands of kilometres that no AC submarine cable can practically achieve. And for connecting asynchronous or incompatible AC systems, HVDC back-to-back converter stations whose converter technology decouples the two AC systems' frequency and voltage control allow their interconnection without the synchronisation requirements that direct AC interconnection between different grid areas creates.
The HVDC transmission market, valued at approximately $12.8 billion in 2026 and growing at ten to twelve percent annually toward $25 billion by 2033, is being driven primarily by the offshore wind industry's expansion into waters where the distance from shore to the wind farm and from the wind farm to the grid connection point exceeds the practical limits of AC submarine cable transmission, requiring HVDC submarine cable systems whose converter stations and cable infrastructure represent the largest single capital cost items in offshore wind project budgets. The North Sea offshore wind build-out, the US East Coast offshore wind development, and the emerging offshore wind industries in Asia are each creating HVDC transmission demand that is taxing the converter station manufacturing capacity and the submarine cable manufacturing capacity of the handful of companies who can produce the high-voltage direct current infrastructure that these projects require.
Hitachi Energy and the VSC Converter Market
Hitachi Energy, formed from ABB's power grids business acquisition by Hitachi in 2020, is the market leader in voltage source converter HVDC technology whose HVDC Light product series has been the commercial reference for VSC HVDC since ABB pioneered the technology in the late 1990s. VSC HVDC, which uses insulated gate bipolar transistor power electronics to create the DC voltage rather than the thyristor-based current source converter that legacy HVDC Classic systems use, creates the HVDC technology that can be connected to weak or passive AC systems, can reverse power flow without reversing voltage polarity, and provides reactive power support to the connected AC systems, creating the operational flexibility that offshore wind farm connections require because the offshore AC collection systems are inherently passive networks that HVDC Classic converters cannot manage. Hitachi Energy's HVDC Light installations connecting offshore wind farms including the Dogger Bank offshore wind connection whose HVDC link will transmit three gigawatts from the world's largest offshore wind farm to the UK grid, and the NordLink HVDC interconnector between Norway and Germany whose 1.4 gigawatt capacity allows the exchange of Norwegian hydropower and German renewable electricity across the North Sea, create the operational reference base that demonstrates VSC HVDC's commercial maturity for the most demanding transmission applications.
Siemens Energy's HVDC PLUS product, the competing VSC HVDC technology whose modular multilevel converter architecture and its operational history in the DolWin and BorWin offshore wind transmission systems in the German North Sea create the competitive VSC HVDC commercial position, represents the duopoly that Hitachi Energy and Siemens Energy maintain in the VSC HVDC converter station market whose high technical barriers to entry and the long project development timelines create the supplier consolidation that new market entrants find practically impossible to overcome without decades of product and project development investment. Prysmian and Nexans are the submarine HVDC cable manufacturers whose production of the high-voltage extruded polymeric insulated DC cables that modern VSC HVDC systems use creates the cable supply bottleneck that is constraining the pace of offshore wind HVDC project delivery, with both companies operating their cable-laying vessels at full capacity and quoting delivery timelines that create the project schedule risk that offshore wind project developers are managing through forward-booking of cable capacity years ahead of installation schedules.
China's HVDC Expansion and the Ultra-High Voltage Projects
China's State Grid and China Southern Power Grid have constructed the world's most extensive HVDC transmission network whose ultra-high voltage direct current links at 800 kilovolts and 1100 kilovolts transmit hydropower and coal power from western China to the eastern coastal load centres across distances of two thousand to three thousand kilometres that no other country's grid has matched at equivalent voltage and power transfer capacity. The UHVDC technology development that State Grid and its equipment supplier TBEA, CSSC, and State Grid Global Energy Interconnection Research Institute have pursued creates the Chinese HVDC technology capability whose scale substantially exceeds the Western HVDC industry's project pipeline and whose potential export to developing market HVDC projects creates the geopolitical dimension of HVDC infrastructure investment.
Top 10 Companies in HVDC Transmission Technology Globally
- Hitachi Energy (ABB Power Grids heritage): Swiss-Japanese energy technology company with HVDC Light VSC technology and the Dogger Bank offshore wind HVDC connection; its VSC HVDC market leadership and its offshore wind transmission project portfolio create the dominant HVDC converter station company whose technology defines the commercial standard for offshore renewable energy transmission.
- Siemens Energy (HVDC PLUS): German energy technology company with HVDC PLUS modular multilevel converter technology and North Sea offshore wind transmission installations; its DolWin and BorWin HVDC projects and its competing VSC technology create the duopoly competitor that shares the HVDC converter station market with Hitachi Energy.
- Prysmian Group: Italian cable manufacturer with the world's largest HVDC submarine cable production capacity and cable-laying vessel fleet; its BorWin and DolWin cable supply and its forward booking by offshore wind developers create the dominant submarine HVDC cable manufacturer whose production capacity constraints determine offshore wind project delivery timelines.
- Nexans: French cable manufacturer with HVDC submarine cable production and the Aurora cable-laying vessel; its competing HVDC submarine cable capacity and its Norwegian production facility create the competing HVDC cable manufacturer whose production capacity alongside Prysmian determines the total submarine HVDC cable supply available for the offshore wind transmission market.
- NKT: Danish cable manufacturer with HVDC cable production expanding for North Sea offshore wind market; its High Voltage cable factory capacity expansion and its entry into the HVDC cable market alongside Prysmian and Nexans create the third HVDC submarine cable manufacturer whose capacity addition is the industry response to the offshore wind-driven cable supply shortage.
- TBEA: Chinese electrical equipment company with UHVDC converter transformer manufacturing for Chinese grid projects; its ultra-high voltage transformer production and its State Grid supply relationships create the Chinese HVDC equipment manufacturer whose domestic market scale exceeds the combined project pipeline of Western HVDC equipment companies.
- GE Vernova: US grid technology company with HVDC converter technology through its Power Conversion division; its HVDC technology development and its grid infrastructure project experience create the US grid equipment company's HVDC commercial position in the North American offshore wind market whose HVDC transmission requirements are growing with the US East Coast offshore wind build-out.
- ABB: Swiss technology company retaining HVDC Classic thyristor-based HVDC technology following the Hitachi Energy power grids separation; its established HVDC Classic converter station supply for point-to-point bulk power transmission over long distances creates the continuing ABB HVDC commercial position in the high-capacity long-distance bulk power transmission that LCC HVDC serves.
- Viscas: Japanese power cable company with HVDC submarine cable products for Asian offshore and interconnector applications; its Japanese manufacturing and its Asian offshore wind and grid interconnector projects create the Asian HVDC cable manufacturer whose production serves the Japanese and broader Asian HVDC cable market that Western cable manufacturers cannot fully serve from their European production locations.
- Elia Group: Belgian electricity transmission system operator with North Sea HVDC interconnector operations; its Princess Elisabeth Island offshore HVDC hub development and its cross-border interconnector operations create the European TSO whose HVDC infrastructure investment in the North Sea offshore wind and cross-border interconnection market defines the grid operator's role in enabling the renewable energy transmission that the HVDC technology companies supply.