BTB DC link modeling, control, and application in the segmentation of AC interconnections

The dynamic control and application of VSC-based Back-to-Back (BtB) DC link to the segmentation of large AC interconnections are investigated. A BtB DC link consists of two voltage-sourced converters (VSC) shunt connected to distinct buses, with DC side coupled. This paper first introduces the regulation modes and control schemes of the two shunt VSCs and the DC tie. Then the AC network segmentation is discussed by applying the dynamic models of the BtB VSCs in linking multiple regional power grids, instead of AC interconnections. With the aid of an extra frequency controller and proper power flow control strategies, the capability of a BtB DC link in improving reliability of large transmission interconnection is demonstrated. The results are illustrated with different fault scenarios on a 13-bus and 28-bus test system, respectively.