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 corresponding to the MTF, using a microprocessor; setting a resonance frequency of the MTF; extracting at least one LC combination case constituting the MTF on a basis of the input parameter and the resonance frequency; performing optimization for harmonic reduction on the LC combination case by computing a first objective function having a total harmonic distortion (THD) as a minimum, and computing a second objective function having a total demand distortion of current (TDD) as a minimum; and extracting an LC combination case determined based on a result of performing the optimization, such that the extracting of the LC combination case is based on the first objective function and the second objective function.