First installation of flexible DC valve tower core structure completed at Yuezhou Converter Station

The main structure of the Pole 1 high-end flexible DC valve tower was installed at the Yuezhou Converter Station of the Gansu–Zhejiang ±800 kV UHVDC transmission project on Aug 6.

This marks a major milestone in the installation of the core equipment for the world's first UHVDC project employing flexible DC technology at both the sending and receiving ends.

As a key national “West-to-East Power Transmission Initiative”, the Gansu–Zhejiang UHVDC project stretches 2,370 kilometers from Minqin county, Wuwei city in Gansu province in West China to Shangyu district, Shaoxing city in Zhejiang province in the east. It is based on a total investment of 35.3 billion yuan ($4.84 billion). The Yuezhou Converter Station, located in Shangyu, Shaoxing, is tasked with receiving and redistributing clean energy generated from the desert–Gobi–wasteland regions of Gansu.

The converter valve is widely regarded as the "heart" of the converter station and represents the project's most critical equipment. Unlike conventional DC transmission projects, the Gansu–Zhejiang project employs world-leading flexible DC transmission technology, boosting transmission capacity from the conventional 5 gigawatts to 8 GW.

The Yuezhou Converter Station is equipped with four valve halls, each housing six valve towers. The newly installed Pole 1 high-end flexible DC valve tower stands 18 meters tall, weighs 215 metric tons, and consists of 200 sub-modules.

The equipment utilizes next-generation high-power IGBT devices capable of responding to grid fluctuations within milliseconds, enabling flexible power control and AC/DC fault ride-through capabilities.

The installation of the converter valve demands extremely stringent precision and environmental conditions. The temperature inside the valve hall must be maintained within a range of 10–25 C. It requires humidity between 30 percent and 60 percent, while air cleanliness must meet Class 100,000 standards — comparable to the environment of a precision pharmaceutical manufacturing facility. The height differential between the 24 mounting bases must not exceed 1 millimeter.

For the valve tower lifting — categorized as the highest safety risk operation in the construction process — State Grid Zhejiang Power Supply Co (State Grid Zhejiang) established a digital-intelligent factory-style installation system within the valve hall. Prior to construction, the team conducted virtual process rehearsals using BIM models to simulate equipment transport routes, lifting trajectories, and extreme-condition risks. Only after verification and validation were the procedures released for on-site execution.

During installation, AGV transport vehicles automatically delivered valve assemblies along preset tracks, AR smart glasses provided the real-time overlay of installation data for workers, and intelligent equipment — including welding robots and integrated environmental monitoring units — were deployed to enable collaborative human-machine operations.

Prior to the valve installation, State Grid Zhejiang personnel conducted parameter consistency inspections at both the converter valve and sub-module levels. Issues identified and rectified included the mixed use of domestic and imported capacitors in the Pole 1 converter valve and single-coil bypass switch configuration in the Pole 2 sub-modules — ensuring that all equipment entered the installation phase in optimal condition.

During the subsequent commissioning phase, full-tower pressurization tests and sub-module pressurization tests will be carried out to verify various functions, including switch device, bypass actuation, and redundant communication.

The project is scheduled to undergo system commissioning and low-voltage pressurization tests of the converter valves in the coming phases. With full commercial operation expected in April 2027, clean energy from Gansu will flow continuously to Zhejiang, providing robust support for energy security and the achievement of carbon peaking and carbon neutrality goals in the Yangtze River Delta region.