A static compensator apparatus for a HVDC system may control harmonic wave compensation at high passive speed to meet operating characteristics of the HVDC system. A static compensator is turned-on in a normal mode and compensates for invalid power and removes a harmonic wave generated by the high voltage direct current system. A static compensator controller controls an operation of the static compensator. A diesel power generator operates complementarily to the static compensator and being turned-on when the high voltage direct current system starts.