WuDongDe Multi Terminal HVDC - Longmen Station

In response to a number of Chinese national VSC HVDC development projects including the Zhangbei DC Grid Project being developed by State Grid China Corporation (SGCC) and the WuDongDe (aka KunLiuLong) scheme being developed by China Southern Grid (CSG) RXHK has developed and had type tested in 2017 an 800kV 5GW VSC HVDC Valve.

KunLiuLong is the official name of the project that is also known as “WuDongDe”. "WuDongDe" is the name of the hydroelectric power station whose output power drove the KunLiuLong project investment.

"KunLiuLong" is the combination name of the three converter stations. "Kun" refers to Kunming North Converter Station (LCC 8GW). "Liu" refers to Liuzhou North Converter Station (VSC 3GW). "Long" refers to Longmen Converter Station (VSC 5GW). The DC voltage for the scheme is 800kV.

At the end of August 2018 when CSG announced the contract award results for KunLiuLong RXHK won the positive pole of the VSC-valve of Longmen Station, a 5GW 800kV valve and controls contract.

Project introduction and significance

Wudongde VSC-UHVDC Project is China's first UHV multi-terminal DC demonstration project, the world's first UHVDC project, and the world's highest voltage level, largest transmission capacity, and longest transmission distance multi-terminal hybrid DC project. It is also a key demonstration project for trans-provincial power transmission which was set as a target for the Chinese national "13th Five-Year Plan for Energy Development" and "13th Five-Year Plan for Electric Power Development".

The Wudongde VSC-UHVDC Project starts from Kunming, Yunnan (a 8GW LCC converter station) in the west of China, and ends in Liuzhou, Guangxi province (Liubei 3GW VSC Converter Station) and Huizhou, Guangdong (Longmen 5GW VSC Converter Station). It adopts ±800kV three-terminal hybrid DC technology, 1452 kilometers long. The project sends the abundant hydropower of the world’s seventh largest hydropower station-Wudongde Power Station to the power load centers in Guangdong and Guangxi via overhead line.

The Wudongde project is an important measure to implement the strategy of power transmission from the west to the east and promote the consumption of clean energy. The Guangdong-Hong Kong-Macao Dawan Bay Area currently consumes 9.5 million tons of coal and emits 25 million tons of carbon dioxide per annum. By substituting this coal fired power generation with hydropower this project effectively promotes energy conservation, emission reduction and air pollution prevention, and is of milestone significance for promoting green development, innovative development, and coordinated regional development.

RXHK Technology Features

• Utilises multi-level redundant and reliable power module bypass strategy to ensure that the converter valve does not lock and stop in the event of any single module failure;
• Demonstrates the development and engineering application of power modules based on IGBT power devices manufactured in China;
• High reliability design of the converter valve control boards, including successful completion of the reliability enhancement verification tests;
• High seismic performance of the converter valve;
• Maintenance friendly design including high-safety, user-friendly internal maintenance channels and portable, multi-function power module test devices;
• Utilises a valve control cross-redundant switching scheme to improve the reliability of the control system and reduce the switching probability;
• Online monitoring of power module health status and historical data record query, providing a technical platform and data support for the life cycle management and maintenance of converter valves;
• Power losses less than 0.7%.

The valve is designed to be installed in two separate valve halls, a LV Hall (0 to 400kV) and a HV Hall (400kV to 800kV).

The LV Valve Hall (0 - 400kV)

The HV Valve Hall (400 - 800kV)

RXHK Scope of Work

RXHK undertook the development and supply of one branch of the ±800kV/5000MW HVDC converter valve for the Longmen converter station in the Wudongde VSC-UHVDC Project. Despite the severe situation of COVID-19 in 2020 RXHK has overcome the difficulties, strictly abiding by the epidemic prevention requirements, and maintained a focused effort, completing all R&D tests, type tests, special tests and routine tests for the power module, valve section, valve tower and valve control system.

Once the equipment was shipped to site RXHK closely supported the construction activities and mobilised to site at the required point to carry out the site tests, commissioning and bipolar station system debugging tasks as required.

Project Milestones

• In May 2020, the installation of Pole 1 of the 0-400kV valve block of the Longmen Converter Station was completed;
• On June 20, 2020, the Pole 1 0-400kV valve group of the Longmen Converter Station was successfully energised for the first time;
• On July 22, 2020, the bipolar 0-400kV valve of the Longmen Converter Station was successfully unlocked and transmitted for the first time;
• On July 26, 2020, full power transmission was achieved by the bipolar 0-400kV valve of the Longmen Converter Station;
• In October 2020, the installation of Pole 1 400-800kV valve block of the Longmen Converter Station was completed;
• On November 1, 2020, the Pole 1 400-800kV valve group of the Longmen Converter Station was successfully energised;
• On December 2, 2020, the bipolar 0-800kV valve of the Longmen Converter Station was successfully unlocked;
• On December 12, 2020, the Longmen Converter Station Pole 1 400-800kV full power transmission was successful;
• On December 17, 2020, the three-terminal (Kunming, Liubei and Longmen) Pole 1 0-800kV converter system was successfully unlocked;
• The full three-terminal bipolar 800kV system was unlocked on December 20, 2020;
• On December 27, 2020, Wudongde VSC-UHVDC Project officially started production and power transmission.