Nan'Ao Multi-Terminal HVDC System

A landmark multi-terminal VSC-HVDC system developed for China’s Nan’ao Island grid reinforcement and wind power plant went online in December 2013. It consists of three converter stations at different locations, connected by a combination of subsea DC cable, land DC cable and overhead DC line. The goal was to reduce transmission losses, increase network security and eliminate the need for reactive power compensation when incorporating wind power generated on the island into the onshore grid.

RXHK was contracted by China Southern Grid to supply the 200MW 160kV VSC-based HVDC valve and control package for the Sucheng converter station. RXHK, in collaboration with Sifang, also provided station controls for all three terminals as well as the overall multi-terminal control and protection system.  

The completion and ongoing success of this project is a significant milestone in the development of power transmission technology. RXHK has overcome one of the industry’s most complex challenges, the intricacies of control and protection for multi-terminal HVDC.

As part of the project valve routine test and type tests has been conducted in July 2015 according to the up-to-date IEC 62501 and IEC 62751. The test has been done in XIHARI (Xi’an High Voltage Apparatus Research Institute Co., Ltd). XIHARI is a test institute certified to IEC17025. GL DNV (ex-KEMA) have inspected the RXHK valves as part of witnessing the tests and issued a formal inspection report.