The invention relates to a high-voltage AC/DC power conversion device, which is formed by a three-phase structure. Each single-phase structure is formed by connecting upper and lower two bridge arm transform units. Each bridge arm transform unit is formed by two groups of device cascade structures and a submodule cascade structure. According to the technical scheme, switching operation is carried out on cascaded sub-modules through the device cascade structure, and thus AC/DC power conversion is realized; and self removal of DC fault can be realized through a full-bridge submodule structure, thereby meeting application requirements of overhead lines.