Numerical AC Loss Analysis in HTS Stack Carrying Nonsinusoidal Transport Current

Bifilar coil structure is promising for reducing ac loss in resistive-type superconducting fault current limiters (FCLs). However, the electric power networks could be contaminated with harmonic components due to nonlinear loads and switch converters. We built a numerical model to calculate transport ac loss in a bifilar stack composed of two coated conductors, carrying distorted current, by means of H-formulation. We compared the calculated losses in the bifilar stack exposed to nonsinusoidal current with the third and fifth harmonics plotted as a function of total harmonic distortion (THD), where THD is defined as the ratio of current magnitudes for the harmonic frequency and fundamental frequency, I
_hf,peak
/I
_ff,peak
. AC loss results in the bifilar stack carrying current with the third harmonic in each conductor were compared with those in an inductive stack and single tape carrying the same current as the conductors in the bifilar stack. Results show that harmonic components have substantial influence on ac loss in the bifilar stack. AC loss values in the stack with fifth harmonic increased monotonically with increasing THD, while ac loss value in the stack with the third harmonic had minimum value when THD is approximately 0.2.