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An efficient two dimensional T-A formulation based approach is proposed to calculate the electromagnetic characteristics of tape stacks and coils made of second generation high temperature superconductors. In the approach, a thin strip approximation of the superconductor is used in which the superconducting layer is modeled as a 1-dimensional domain. The formulation is mainly based on the calculation of the current vector potential T in the superconductor layer and the calculation of the magnetic vector potential A in the whole space, which are coupled together in the model. Compared with previous T-based models, the proposed model is innovative in terms of magnetic vector potential A solving, which is achieved by using the differential method, instead of the integral method. To validate the T-A formulation model, it is used to simulate racetrack coils made of second generation high temperature superconducting (2G HTS) tape, and the results are compared with the experimentally obtained data on the AC loss. The results show that the T-A formulation is accurate and efficient in calculating 2G HTS coils, including magnetic field distribution, current density distribution, and AC loss. Finally, the proposed model is used for simulating a 2000 turn coil to demonstrate its effectiveness and efficiency in simulating large-scale 2G HTS coils. [ABSTRACT FROM AUTHOR]

With significant interest in the use of high‐temperature superconducting (HTS) components in electric aircraft, there is a need for novel modelling techniques that allow architecture‐level studies of the electrical systems including HTS components. In this study, a simple electric network architecture, as proposed in the literature has been considered, which includes generators, dynamic propulsion load and cables. This electric network has been modelled considering conventional technology and using HTS cables by replacing the conventional copper cables, to evaluate the variations in the network performance. The network performance has been studied for the dynamically varying propulsion load, which is nearly equivalent to the aircraft load over the entire flight duration. Following this, electric faults have been applied at various locations, and the impact of HTS cables on the network fault levels has been evaluated. The fault current levels are compared using both conventional and HTS cables, due to the fault current limiting properties of the HTS cables, they are observed to offer lowered fault current values. [ABSTRACT FROM AUTHOR]

A coaxial cable made out of helically wound 2G HTS tapes is being widely implemented based on its low critical bending radius, ease of manufacturing and installation. Though the design technique is mature, the cable still lacks standard Ic definition. With increased usage of such cables, robustness in its operation is expected. HTS tapes are highly sensitive to externally applied mechanical stress and strain values. These limitations force the coaxial cables to be operated at 50–75% of its rated capacity. One of the major problems in coaxial cable design is the contact resistance of the tapes with the terminal, which affects the current distribution among different tapes in the same layer. Further current redistribution at constant intervals helps the applied current in bypassing the localized faults in the individual HTS tapes, thus making efficient use of the major length of the tape. This paper proposes the use of voltage shunts between HTS layers at constant intervals for regular current redistributions along the length of the cable. This method significantly helps to sustain the Ic value of the cable, even if it has got several minor defects in the tapes. [ABSTRACT FROM PUBLISHER]

High-temperature superconducting (HTS) triaxial conductor on round core (CORC) cable is a potential candidate for use in the transmission line of hybrid-electric aircraft because of its advantages in compactness, high power density, and reduced usage of HTS tapes. The harmonic currents generated by ac/dc converters, generators, and motors in the aircraft affect the ac loss of the transmission cable, thus influencing the efficiency of the cable. This paper analyzes the influence of harmonic current on the magnetization loss of a triaxial CORC HTS cable (10 MW, 3 kV/2 kA), which is designed for hybrid-electric aircraft. A finite element method model based on the T-A formulation has been developed for the HTS triaxial CORC cable, which calculates the losses induced both with and without applied harmonic currents. The results show that the magnetization loss has a significant nonuniform distribution among three phases even under a three-phase balanced rated load. The results also show that a small harmonic current (less than 10% of the rated load current) can lead to a considerable increase in the magnetization loss of the cable (up to 40%). In the triaxial CORC cable, harmonic currents lead to the highest increasing rate of magnetization loss with respect to frequency in the innermost phase. [ABSTRACT FROM AUTHOR]

• The DFIG is a promising wind turbine generator type. • A DFIG wind turbine system is connected to a DC system using a SMES-FCL device. • The SMES-FCL system is used to limit the high DC currents and to store the energy. Wind energy is seen as one of the main pillars of renewable energy. However, the intermittent nature of these sources still poses as a major challenge. Moreover, sensitivity to grid faults and response to load changes are also main concerns. Superconducting devices have been introduced to solve grid faults and energy storage problems associated with renewable energy sources. Nevertheless, the cost of superconducting materials was still a major drawback for their application in power grids. In this paper, a novel power electronics circuit is used to connect the superconducting magnetic energy storage (SMES) to a DC system based on a doubly fed induction generator wind turbine. The proposed system merges energy storage function and the fault current limiting function into one device which is referred to as SMES-FCL in this paper. The role played by the SMES-FCL is studied under various scenarios that may affect the whole system. The study of the system is carried in MATLAB/SIMULINK where the system is simulated in standalone and grid-connected modes. In the end, the proposed SMES-FCL control circuit is tested in a small-scale DC system experimentally. [ABSTRACT FROM AUTHOR]

Superconducting devices have emerged in many applications during the last few decades. They offer many advantages, including high efficiency, compact size, and superior performance. However, the main drawback of these devices is the high cost. An option to reduce the high cost and improve the cost-benefit ratio is to integrate two functions into one device. This paper presents the superconducting fault current limiting transformer (SFCLT) as a superior alternative to normal power transformers. The transformer has superconducting windings and also provides fault current limiting capability to reduce high fault currents. The SFCLT is tested in two power system models: a 7 bus wind farm-based model simulated in PSCAD and on the 80 bus simplified Australian power system model simulated in real-time digital simulator. Various conditions were studied to investigate the effectiveness of the fault current limiting transformer. [ABSTRACT FROM AUTHOR]

Growing electricity demand from a range of sources and the changes of the power grid structures open the possibility of more frequent and much higher fault current. Traditional solutions to the fault are difficult to satisfy the requirement of the new power grid due to many factors, such as high cost, additional impact to power grid in normal loading condition, which leads to the research for an efficient alternative solution of interest to both academia and industry: Superconducting fault current limiter (SFCL). In this paper, two types of low-inductance solenoidal coils, the braid type and the nonintersecting type, are built with 2G high-temperature superconductors. The current limiting performance, the recovery characteristics, and the ac losses of both types of coils are tested and compared in detail. Experimental results show that both types of coils can effectively limit fault current and recover in several seconds. Furthermore, comparison between the ac losses of both types of SFCLs shows that the ac loss of the braid type coil is lower than that of the single tape by about an order of magnitude in low-current regions. [ABSTRACT FROM PUBLISHER]