1. A method for designing a multiple tuned filter (MTF) in a high voltage direct current (HVDC) system, the method comprising: setting an input parameter constituting the MTF; setting a resonance frequency of the MTF; extracting at least one LC combination case constituting the MTF on the basis of the input parameter and the resonance frequency; performing optimization for harmonic reduction on the LC combination case; and extracting an LC combination case determined based on a result obtained by performing the optimization.