ELECTRIC POWER CONVERSION APPARATUS AND ESTIMATION APPARATUS

A power conversion device (100_1) included in a self-excited DC power transmission system (400) connected to an AC system (300) includes a self-excited converter (6_1) and a control device (5_1). The control device includes: a storage (207) to store first vibration information and a first control parameter of the self-excited converter in association with each other for each of a plurality of pieces of first vibration information, a vibration detector (203) to detect a vibration component of an AC voltage of the AC system; a determination unit (205) to determine whether first similar vibration information similar to first detected vibration information including the vibration component of the AC voltage of the detected AC system exists in the plurality of pieces of first vibration information; and a setting unit (209) to set the first control parameter associated with the first similar vibration information as a new control parameter of the self-excited converter when the first similar vibration information exists.