China Launches World’s Largest Offshore DC Converter Station
China has reached a major milestone in renewable energy infrastructure as the world’s largest offshore flexible direct current (DC) converter station set sail from Nantong, Jiangsu Province, on July 7, 2026. The 25,000-tonne structure — the core of China’s first sea-land integrated flexible DC transmission project — is bound for the Yangjiang Sanxian Island offshore wind farm in Guangdong Province, where it will deliver clean electricity to the Guangdong-Hong Kong-Macao Greater Bay Area.
A Giant of Engineering
The offshore converter station is a seven-story steel platform measuring 85.5 meters long, 82.5 meters wide, and 43 meters tall — roughly the height of a 15-story building, with each floor covering an area comparable to a standard football field. According to CNR, the structure weighs approximately 25,000 tonnes, equivalent to more than 50 high-speed train sets.
With a voltage rating of ±500 kV and a transmission capacity of 2,000 MW (2 GW), the converter station is the highest-voltage and largest-capacity offshore flexible DC converter station in the world. It is designed to withstand Category 17 typhoons and magnitude 8 earthquakes, featuring specialized anti-corrosion technology for the high-salt, high-humidity marine environment.
The Journey to Sea
The converter station departed from the Zhenhua Heavy Industries dock in Nantong at 19:30 on July 7, embarking on a voyage of approximately 1,000 nautical miles (about 1,852 km) to Yangjiang, Guangdong. The journey is expected to take five to seven days. The Science and Technology Daily reported that the departure marks the completion of all land-based construction work, including structural construction, equipment installation, and system debugging.
“The dispatch of the offshore converter station marks the completion of all land-based construction work including structural construction, equipment installation, and system debugging. The project now moves to the critical phase of offshore transport and installation,” said Ji Shaofeng, General Manager of the Major Project Promotion Office at China Southern Power Grid Guangdong Power Grid Company.
Technical Innovation: The ‘Shared Corridor’ Model
The Sanxian Island project adopts a sea-land integrated DC transmission model that introduces an innovative “shared corridor” approach. Multiple offshore wind farms — from three power generation groups and four separate wind farms — will pool their electricity through a single onshore DC overhead transmission line, rather than building individual transmission corridors.
Wan Pingping, an engineer on the Sanxian Island project, explained that this model “can avoid multiple offshore wind power projects building their own separate onshore transmission lines, improving transmission corridor utilization efficiency, saving land space resources, and achieving project investment optimization.”
The platform is located nearly 100 km offshore, with a submarine cable transmission distance of 115 km — the farthest offshore distance and longest transmission distance for any domestic offshore wind DC transmission project. Combined with 180 km of onshore overhead lines, the total transmission corridor spans approximately 300 km.
Powering the Greater Bay Area
Once operational, the Sanxian Island project is expected to deliver approximately 6 billion kilowatt-hours of clean electricity annually to the Guangdong-Hong Kong-Macao Greater Bay Area. According to CGTN, this will save 1.74 million tonnes of standard coal and reduce carbon dioxide emissions by approximately 4.63 million tonnes each year.
A New ‘Sea Grid’ Takes Shape
The project represents a fundamental transformation of China’s power grid architecture. For the first time, the China Southern Power Grid’s main network extends into deep-sea areas, marking the formation of what officials are calling a “sea grid.”
“Before the Sanxian Island project, the China Southern Power Grid’s main network was entirely on land. The Sanxian Island project extends the main grid’s reach into the deep sea for the first time,” said Luo Tao, General Manager of the Infrastructure Department at China Southern Power Grid Guangdong Power Grid Company. “The offshore converter station has officially become a component of the Southern Power Grid’s main network.”
Broader Implications
The project cements China’s leadership in offshore wind transmission technology. As the world’s largest offshore wind power market, China has been aggressively expanding its offshore wind capacity as part of its “dual carbon” goals — peaking carbon emissions by 2030 and achieving carbon neutrality by 2060.
The innovative construction method — “onshore assembly, integrated transport, float-over installation” — developed by Zhenhua Heavy Industries (ZPMC) provides a replicable template for future offshore wind projects. The State-owned Assets Supervision and Administration Commission confirmed that the float-over installation technique, likened to “a car reversing into a parking spot,” allowed the massive structure to be precisely positioned despite challenging offshore conditions.
What to Watch
The converter station is expected to arrive in Yangjiang around July 12–14, 2026, where it will undergo offshore installation. The Sanxian Island project’s second phase is already planned to share the same transmission corridor, signaling China’s intent to scale this model for future offshore wind developments. As the country pushes toward its 2060 carbon neutrality target, projects like this will be critical in transforming how renewable energy is transmitted from sea to shore.