An optimal control strategy for VSC-HVDC system considering transient stability

Based on the model of synchronverter, an equivalent mathematic model of VSC-HVDC system is firstly established in this paper. Secondly, in order to improve the transient characteristic of VSC-HVDC system, controller with droop characteristics similar to synchronous machine is designed to replace classic vector controller. Further, a Bang-bang control strategy based on the variation of power angle is put forward, which enhances the system damping effectively and consequently further improve the transient stability of system. Finally in PSCAD/EMTDC, extensive tests are carried out to verify the effectiveness of the proposed strategy in implementation of an AC/DC system with VSC-HVDC.