China State Grid makes new breakthrough in DC power distribution tech

State Grid Corporation of China (SGCC) has made new technological breakthroughs in direct current (DC) power distribution with Pangdong DC central station put into service on Tuesday by State Grid Jiangsu Electric Power Co., Ltd, a subsidiary of SGCC.

Functioning for AC/DC conversion and power distribution, the Pangdong station acts as one of the two "hearts" for State Grid Jiangsu's demonstrative low and medium voltage (LV/MV DC) distribution project, which is expected to become a world leading LV/MV DC distribution system with the largest scale, complete voltage levels as well as latest technical equipments when completed this August.

Listed as a national key R&D project in 2018 with construction kicked off last May, the demonstation project is applied and undertaken by State Grid Jiangsu. It has built two DC central stations ("hearts") in Pangdong and Jiuli within Wujiang Economic Development Zone in Suzhou city of east China's Jiangsu province to construct a LV/MV DC system covering various scenarios such as municipal, industrial and commercial, and household uses. With accumulative DC load of 10.5MW, the system is capable of different DC output at 10KV, 750V, and 375V for meeting different power demand.

The newly-commissioned Pangdong station, for example, could convert 10KV AC into 10KV DC, and deliver, upon demand, different voltage level DC through a transformer, according to Yang Chen, deputy director of the operation and inspection department with State Grid Suzhou Power Supply Company under State Grid Jiangsu.

The Pangdong station is also the control center of the entire distribution system, said Yang, noting that power supply can be restored within 100 milliseconds in case of network failure thus increasing power supply reliability rate to 99.999 percent with latest control system and coordination system.

It is noted that the project so far has made breakthroughs in areas of system planning and design, key equipment development, operation control technology and system protection technology, with 93 patents accepted, 12 software works registered, as well as 6 domestic and foreign standards compiled.

The demonstration project is expected to explore the construction, operation and maintenance model for integrated DC power distribution and use, and provide experience for global energy transformation and power consumption changes, according to Yuan Dong, deputy director of the equipment department of State Grid Jiangsu.