Optimization of Distributive Ratios of Apportioned Winding Configuration in HTS Power Transformers for Hysteresis Loss and Leakage Flux Reduction

Abstract

In recent years, using high-temperature superconductor (HTS) transformers in transportation and electrical power systems has attracted much interest. The major advantages of HTS transformers compared with conventional ones are much smaller size and volume and lighter weight in confined spaces of urban areas or transportation devices. One of the most critical parameters to design, fabricate, and commercialize HTS transformers is hysteresis loss in HTS tapes. Using numerical methods, the accurate value of hysteresis loss and efficiency can be calculated or estimated in HTS transformers. In this paper, two innovative techniques to reduce the leakage flux and thereby hysteresis loss in HTS transformers have been proposed. In the first technique, the concentric windings of HTS transformer are apportioned into a certain number of sub-windings. In the second one, with optimizing the distributive ratios of sub-windings, the windings become unsymmetrical. In order to demonstrate the effectiveness of proposed techniques, an accurate and advanced numerical method based on finite element analysis has been used to design four symmetrical and unsymmetrical primary (P)-secondary (S)-P-S-P and P-S-P-S-P-S-P winding schemes. The simulation results prove the effectiveness of both techniques in reducing the radial and axial leakage flux magnitudes and thereby hysteresis loss in HTS windings.