Research Of Protection And Start-up Strategy Of VSC-HVDC Under AC Network Fault Of VSC-HVDC Inverter Side

VSC-HVDC has many advantages, so it will be applied in the interconnectionprojects between AC networks widely. The faults of AC network connected toVSC-HVDC may bring severe damages to VSC-HVDC. In this paper, the controland protection strategy of VSC-HVDC has been proposed when the AC networkhave faults. That is the "soft shut-off" control strategy of VSC-HVDC, which has thefunction of self-protection and can act as the spinning reserve electric power source. It isvery common in switching on a no-load long line in power system. If any measureshave not been done, severe operation overvoltage will appear instantaneously whileswitching on the no-load long line. In this paper, power system is started up by "softstart-up" control of VSC-HVDC and it avoids the severe operation overvoltage ofswitching on the no-load long line. Corresponding controllers have been designedbased on PID control principle, and simulations of "soft shut-off" and "soft start-up" ofVSC-HVDC have been carried on with the PSCAD/EMTDC software.