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A numerical multiscale model is used to resolve the high computation complexity in the ac loss calculation of large-scale superconducting devices and proves advantageous with regard to time and memory requirements. In the multiscale model, the background field estimation method is of crucial importance to the calculation accuracy. In this paper, we propose four new background field estimation methods, including the Jacobi Gauss–Seidel hybrid and iteration methods, to improve the accuracy and expand the application scope of the multiscale model. A high temperature superconducting solenoid magnet is used to test the performance of these four methods and the results are compared with those of the H-formulation reference model and the multiscale model with a J0 uniform background field estimation method. Results show that in the 19 A/50 Hz ac transport current test case: the Jacobi Gauss– hybrid and iteration methods reduce the error of the ac loss mean value/peak value to 7.88%/5.89%, 5.71%/2.4%, 3.22%/1.22%, and 1.83%/0.69% with the total time cost reduced by 15.7, 8.9, 13.5, and 7.8 times. The multiscale model is expected to achieve even higher accuracy in applications where the ac loss is relatively small due to its coincidence property. The greatly improved accuracy makes the multiscale model a reliable substitute for the H-formulation model. In addition, the idea of iteration and back substitution in background field correction widely expands the application scope of the multiscale model. Alternative background field estimation methods allow the multiscale model to be applied flexibly according to the requirement of the calculation speed and accuracy. The feature of small degrees of freedom resolves the high computation complexity of the ac loss calculation model and reduces the memory requirement. All these merits make the multiscale model competitive in the calculation of ac loss. [ABSTRACT FROM AUTHOR]

Superconducting fault current limiters (SFCLs) are considered as one of the most promising technologies to limit fault current levels, as they can suppress fault currents without adding impedance to the circuit during normal operation. In this paper, a flux-coupling-type SFCL (FC-SFCL) based on disconnecting coupling windings for current reduction is considered as a potential scheme to limit fault currents due to its low steady impedance before a fault and higher current-limiting impedance after a fault. Three types of winding methods of the FC-SFCL are introduced and the main parameters are discussed, along with the voltage distribution of the coils. Based on these, the optimal winding structure is determined, a small-scale test prototype is designed and fabricated, and a series of experimental tests is conducted. From the demonstrated experimental results, the FC-SFCL prototype is able to effectively suppress the fault current’s steady value to a lower level, and it has good performance in terms of current reduction. [ABSTRACT FROM AUTHOR]

In the latest design studies of superconducting magnetic energy storage (SMES) systems, the emphasis was put on the electromagnetic design of SMES magnets without giving due attention to the electrical design with a view to eliminating the overvoltage problem. The power conditioning system (PCS) interfaces with the superconducting magnet and the ac system through an electrical connection. With a pulse-width modulation converter usually adopted in the PCS, the high-frequency overvoltage problem is even more serious. Therefore, electrical design based on voltage distribution analysis and protection measures should be taken into account during the SMES design. This paper first gives transient models of PCS, SMES, and the connecting cable in a systematic view. Later on, a design flow path containing both the electromagnetic design and the electrical design is presented. Adopting the proposed design method, one design plan of a 1 MJ HTS SMES is chosen and conclusions are drawn on its optimal comprehensive design plan. [ABSTRACT FROM PUBLISHER]