Wire connecting method and converter station for ultra-high voltage direct current power transmission, and ultra-high voltage direct current power transmission system

A wire connecting method and a converter station for ultra-high voltage direct current power transmission, and an ultra-high voltage direct current power transmission system. A rectification-side ultra-high voltage low-end converter station (11) converts a first AC power into a first low voltage DC power which is transmitted to a rectification-side ultra-high voltage high-end converter station (12). The rectification-side ultra-high voltage high-end converter station converts a second AC power into a DC power which is added to the first low voltage DC power so as to generate a first ultra-high voltage DC power which is transmitted to an inversion-side ultra-high voltage high-end converter station (31). The inversion-side ultra-high voltage high-end converter station outputs a third AC power and a second low voltage DC power. The third AC power is supplied to a first load region. The second low voltage DC power is transmitted to an inversion- side ultra-high voltage low-end converter station (32) and is converted into a fourth AC power to be supplied to a second load region. More than one medium-end converter stations may be provided between the high-end and low-end converter stations at each of the rectification side and the inversion side, and each station is cascaded through a DC line. By means of multiple points, the system solves a problem of poor grid security and stability due to a single point.