China Southern Power Grid announced the completion of the Luxi hybrid back-to-back HVDC project on the 26th of June 2017, according to Xinhua News. The project is a vital part in the asynchronous interconnection between the grid of Yunnan province and the main China Southern Grid aiming to transfer power from the hydroelectric power plants in the south-west of China to the main load centers in the south (Estimated to more than 3000TWh per year).
The project is located in the Luoping County of the Qujing district in the province of Yunnan. It is a hybrid HVDC system forming a combination of HVDC classic (LCC) and HVDC light (VSC). The capacity of the VSCs in the system is 1000MW at a rated dc-link voltage of ±350 kV, while the capacity of bipole LCC reaches 1000MW for each pole.
The project was completed in two stages. The first stage construction included the VSCs of the monopole HVDC light unit and was completed in 2016, with the second stage of the project completed in June 2017. The converter station is connected to four 500KV transmission lines on one terminal and three more 500kV lines into the the side of the main grid.
The HVDC classic consists of a set of 12 pulse converter units, installed in each pole, with six 400MVA converter transformers, two sets of 160MVar reactive power compensators for the rectifier station side, and three sets of 110MVar reactive power compensators in the inverter station side.
The project was completed in two stages. The first stage construction included the VSCs of the monopole HVDC light unit and was completed in 2016, with the second stage of the project completed in June 2017. The converter station is connected to four 500KV transmission lines on one terminal and three more 500kV lines into the the side of the main grid.
The HVDC classic consists of a set of 12 pulse converter units, installed in each pole, with six 400MVA converter transformers, two sets of 160MVar reactive power compensators for the rectifier station side, and three sets of 110MVar reactive power compensators in the inverter station side.
 | ||
Main valve hall of the Luxi station
|
The project is a result of the many developments on hydropower along the Changjiang River in Yunnan, with the potential benefits driving the China Southern Grid to reach an agreement with the province of Yunnan for the connection of the new hydropower stations to the main grid. Analysis on the network showed that a synchronous connection between the Yunnan and the main grid increased the risk of cascading failures in both networks so an HVDC connection was the preferable choice. However, the weak AC system in the province of Yunnan did not allow for an HVDC classic solution to by built for the project. The final design solution was a hybrid HVDC project, taking advantage of the benefits provided by the HVDC light for fast response in real and reactive power despite the weak AC system, while the HVDC classic is able to transmit bulk power.