High -voltage direct current system is in service, and direct current side inevitable will produce a large amount of harmonics, makes the neighbouring communication line of direct current circuit receive the interference, must restrain through the filter, and DC filter restraines the important equipment of direct current side harmonic as the current conversion station to the antithetical couplet is the effective means that restraines direct current system direct current side harmonic between high voltage DC generating line and neutral bus. For realizing above -mentioned technological mesh, the utility model discloses the technical scheme who takes as follows: take current conversion station DC filter circuit of secondary circuit design, characterized by includes a DC filter sub -station at least, the DC filter sub -station sets up 1224 wave filters of double tunning and 1236 wave filters of double tunning, do 1224 wave filters of double tunning and 1236 wave filters of double tunning connect respectively at direct current utmost point P1 WN and neutral bus P1 between the WP.