Wudongde (KunLiuLong)

Project Overview

The Wudongde HVDC project, also known as the Wudongde VSC-UHVDC Project or KunLiuLong project, is a groundbreaking ultra-high voltage direct current (UHVDC) transmission system in China. It is the world's first ±800 kV UHV multi-terminal flexible DC transmission project, representing a significant advancement in power transmission technology.

Technical Specifications

The project consists of three converter stations: Kunming North Converter Station (LCC) with 8 GW capacity, Liuzhou North Converter Station (VSC) with 3 GW capacity, and Longmen Converter Station (VSC) with 5 GW capacity. The system operates at ±800 kV, making it the highest voltage level multi-terminal hybrid DC project globally. It also boasts the largest transmission capacity and longest transmission distance for a multi-terminal hybrid DC project.

Converter Technology

The Kunbei converter station uses LCC technology, while both receiving ends (Liubei and Longmen) employ VSC technology. This hybrid approach combines the advantages of traditional HVDC and flexible DC systems.

The VSC stations utilize Modular Multilevel Converter (MMC) technology. Each MMC converter valve is composed of half-bridge submodules (HBSM) and full-bridge submodules (FBSM) in a mixed cascade ratio of 3:7. The upper and lower bridge arms contain 200 submodules at any given time, with some redundancy.

Control System

The control system for the Wudongde HVDC project is designed as follows: Kunbei-side uses constant DC and constant α control, Liubei-side employs constant active and reactive power control, and Longmen-side utilizes constant DC voltage and reactive power control.

Transmission Line

The total length of the Wudongde transmission project is 1,452 km, with the Kunming-Liuzhou section spanning 932 km. The average soil resistivity along the line is 1750 Ω·m.

Transformer Configuration

The project uses three-phase double-winding transformers with the following capacities: Kunbei-side has 1,217.4 MVA per single set, wired in Y0/Y and Y0/△, Liubei-side has 870 MVA, wired in Y0/Y, and Longmen-side has 1440 MVA, wired in Y0/Y.

Operational Modes

The Wudongde HVDC system can operate in three basic DC operation modes: positive full-voltage ground return, negative full-voltage ground return, and bipolar operation. Under normal bipolar operation, the system transmits ±5 kA at ±800 kV, delivering a total power of 8000 MW.

Environmental Impact

The Wudongde HVDC project plays an important role in China's strategy of transmitting power from the west to the east. By substituting coal-fired power generation with hydropower, it promotes energy conservation and emission reduction. The project is estimated to reduce coal consumption by 9.5 million tons and carbon dioxide emissions by 25 million tons annually in the Guangdong-Hong Kong-Macao Greater Bay Area.