Lingbao I is a 360 MW back-to-back HVDC station located on the border between Henan and Shaanxi provinces in central China. The station has been in operation since October 2005 and owns by the State grid of China. The Lingbao II extension project expands the original asynchronous interconnection by an additional 750 MW, and increases the possibility of power sharing between the two networks
To complete the extension, ABB delivered valves and control system components. The project uses six-inch thyristors rated at 4,500 Ampere, which so far is the highest rating in the world. The ABB MACH control system is the world's most commonly used control platform for HVDC and FACTS projects.
Back-to-back HVDC stations are able to couple separate electricity grids. In a back-to-back station, both converters are in the same area, usually the same building, and the length of the direct current line is kept as short as possible. The DC voltage in the intermediate circuit can be selected freely at HVDC back-to-back stations because of the short conductor length. DC voltage is usually kept as low as possible, in order to build a small valve hall and to reduce the number of series-connected thyristors in each valve. For this reason, valves with the highest available current rating (up to 4,500 Ampere) are used.