Research on "Soft Start-up" of VSC-HVDC in Power System Restoration after Blackouts

It is very common to switch on a long no-load line in power systems. If nothing has been done, switching surge will appear instantaneously. In this paper, Voltage Source Converter (VSC) based HVDC (VSC-HVDC) technology is used in power system restoration to solve the problem of switching surge when switching on a long no-load line. Control strategies of VSC-HVDC are developed based on PI controllers. Simulation to start up a long no-load line has been conducted in three conditions respectively on software PSCAD/EMTDC. The simulation includes starting up a long no-load line without VSC-HVDC, starting up a long no-load line with VSC-HVDC when DC voltage reaches the rated value and "soft start-up" the long no-load line with VSC-HVDC. Simulation results show that "soft start-up" with VSC-HVDC can effectively reduce the switching surge when switching a long no-load line.