Analysis on AC Loss of DC HTS SFCL Coils Due to AC Ripple Current in MMC-Based DC System

In this paper, a DC system based on MMC converter is developed in PSCAD/EMTDC to analyze the AC ripple characteristic. Then, two DC HTS SFCL coils without and with iron yokes are investigated and compared by 2D FEM models, given that the AC ripple current consists of high order and low order harmonics in MMC-based DC system. The AC loss in the coil with iron yokes is lower than that without iron yokes 39%, which indicates AC loss due to AC ripple current can be effectively reduced by iron yokes. The result of this paper can provide some reference to the rational design of DC HTS SFCL and corresponding cryogenic systems.