I. Introduction
Ultra-high Voltage Direct Current (UHVDC) transmission technique can lower the short-circuit current level of the circuit, actualize regional electricity consumption, and is the primary way for long-distance power transmission [1]. During transmission, losses occur in the converter station and transmission line [2], causing errors in power settlement at the gateway, affecting the fairness of power system transactions, and increasing the operational expenses of power grid firms [3]. It is necessary to conduct research on loss measurement to improve the efficiency of UHVDC transmission.