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A simplified two-dimensional (2D) model, which takes the helical structure of the conductor on round core (CORC) cable into consideration, is utilized to analyze the electromagnetic and thermal properties of the cable. The model couples multi-physical fields through the JcBT(B,T) properties of the superconducting tape. We first introduced the modeling strategy and verified the validity of the 2D model. Then, considering the influence of thermal on the critical current of the tape, the cable loss under different conditions has been calculated. By changing the relative positions of the inner and outer conductor layers of the 2D model, the influence of the magnetic field on CORC cable loss can be obtained, and it can be extended to the periodic three-dimensional (3D) structure. [ABSTRACT FROM AUTHOR]

High-temperature superconducting (HTS) potential solution of solving the urban demand of large load and high-density power. However, the ac loss within the cable body is one of the primary factors limiting the large-scale HTS cable application. Due to the complex spiral structure of CORC (conductor on round core) cable and the high aspect ratio of conductors, modeling and calculation of CORC cable are pretty challenging. To better assess the cable loss, this article illustrates an improved model based on T-A formulation. Combined with a low-dimensional thermal model, the JcBT(B,T) characteristics of HTS tape are applied in simulation. With a global parameter control equation, the current redistribution of the tape can be analyzed by the model. The loss of a three-phase coaxial (tri-axial) HTS cable under different electric and thermal conditions has been calculated. This article provides a method based on T-A formulation to study the current redistribution and quench process. [ABSTRACT FROM AUTHOR]

A two-dimensional (2D) modeling method, which takes helical structure of superconducting layers in HTS cables into consideration, is proposed to analyze electromagnetic properties of HTS power transmission cable. The model is characterized by E-J power law and H-formulation, and is successfully implemented by finite element software. We first expound the principle of using 2D model to simulate 3D structure of a HTS cable. Then, the modeling process is given. In order to verify the validity of the method, a 3D model was established as the control group, and the current distribution and AC loss were compared. The influence of the 3D structure parameters of the cable has been investigated, including the pitch of superconducting layers and the gap width between HTS tapes. [ABSTRACT FROM AUTHOR]

In the process of power compensation of the superconducting magnetic energy storage system (SMES) in the power grid, the existence of ac loss and eddy current loss will cause the magnet to heat up, and temperature rise is the main factor limiting the power output capability of SMES. This article proposes a state assessment method (SAM) that considers the temperature rise of the magnet. This method comprehensively considers the effects of the initial operating current (I0), initial temperature (T0), power response time (t), and output voltage (U) of the magnet on the temperature rise. Before SMES responds to the system power command, a magnet temperature estimation link is added to adjust the power command according to the magnet's possible temperature rise so as to ensure the magnet's safety. By simulating the operating conditions of 150 kJ/100 kW SMES in the microgrid, it is proved that the magnet's thermal stability is significantly improved after adding SAM, and the system operating parameters still meet the requirements within a particular response time. This method helps to maximize the power response potential of SMES under the premise of protecting the safety of the magnet. [ABSTRACT FROM AUTHOR]

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]

The calculation of ac loss is an essential part in the thermal stability estimation of the high-temperature superconductor (HTS) superconducting magnetic energy storage system (SMES). In this paper, we propose an artificial neural network (ANN) prediction model to calculate the ac loss in real-time and apply the ANN prediction model to a 150 kJ self-made HTS SMES. The ANN prediction model is composed of a multi-scale model and an ANN. An ac loss data set calculated with the multi-scale model is used to train the ANN, and a validation data set is used to test the accuracy of the ANN after training. By comparing with the homogenization model, we find that the multi-scale model is reliable when used for ac loss calculation and suitable for building ac loss data set due to its high calculation speed. The ANN prediction model is verified to be reliable for fast estimation of the ac loss, and its accuracy improves as the scale of the training data set increases. [ABSTRACT FROM AUTHOR]

The losses of Superconducting Magnetic Energy Storage (SMES) magnet are not neglectable during the power exchange process with the grid. In order to prevent the thermal runaway of a SMES magnet, quantitative analysis of its thermal status is inevitable. In this paper, the loss characteristics of a self-developed 150 kJ SMES magnet are analyzed by means of experiments and simulations, including the loss of the joint resistance, the eddy current loss of the metal cooling structures and the AC loss of the superconducting magnet. A thermal model of the magnet was built to theoretically analyze the relationship between the current and magnet temperature variation. Three kinds of power compensation experiments were carried out to study the thermal characteristics of the SMES magnet. The temperature variation of the magnet under these three operating conditions was simulated. The simulation results and experimental results are compared and analyzed. [ABSTRACT FROM AUTHOR]

AC loss is an unavoidable problem for a conduction-cooled HTS superconducting magnetic energy storage (SMES) magnet during dynamic operation, which may cause a temperature raise and affect the reliable operation of the magnet. In this paper, the anisotropic homogenization method is employed to realize the modeling of a 150 kJ hybrid SMES magnet based on H-formulation. The SMES magnet has a maximum of approximately 7000 turns. First, the homogenization method is validated that it can reasonably predict the ac losses of both YBCCO coils and BSCCO coils, but it has lower accuracy to estimate the ac losses of BSCCO coils than YBCO coils. Then, ac loss characteristics of the SMES magnet during dynamic operations are investigated. The magnetic field, current density distribution, and ac loss distribution are presented and discussed for different operation conductions. The results indicate that a steady-state current of less than 100 A may be an appropriate choice during power exchange for reducing ac loss. [ABSTRACT FROM PUBLISHER]

• In consideration of cost, stability, transient characteristics and parameter matching of the DC SFCL, an effective optimization design method consisting of electromagnetic theory and intelligent algorithm is proposed, which can obviously promote the utilization efficiency and stability of YBCO coated conductors. • Combined with three operation states of the DC SFCL, a corresponding FE model is established to simulate and evaluate the performance of superconducting coil in the DC SFCL, which further reveal the AC loss characteristics of super-conducting coil during current limiting process. With the increase of DC transmission voltage and capacity, large dc fault current becomes an important issue due to the bottleneck of the capacity of the DC breaker. In order to solve the problem, we have proposed a novel hybrid type DC superconducting fault current limiter (DC SFCL) in our previous papers. Based on a series of previous researches, some improvements are made to design the hybrid type DC SFCL for application in a MMC system in this paper. The target is to limit short circuit current and avoid converter valves blocked when the DC short circuit occurs. In consideration of cost and stability, combined with the transient characteristics and parameter matching of the DC SFCL, an effective optimization design method consisting of electromagnetic theory and intelligent algorithm is proposed, which can obviously promote the utilization efficiency and stability of YBCO coated conductors. According to the optimization design method, a design scheme of the DC SFCL is put forward. Combined with three operation states of the DC SFCL (normal state, current limiting state I and current limiting state II), a corresponding finite element model is established to simulate and evaluate the performance of superconducting coil in the DC SFCL, which further reveal the AC loss characteristics of superconducting coil during current limiting process. [ABSTRACT FROM AUTHOR]

• Using integral method to measure the AC loss of superconducting coil only needs to get the coil's voltage and current for simple calculation. • It is not necessary to extract the inductive and resistive components from the coil voltage separately. • The suggested integral method can be applied to measure the AC loss under non-sinusoidal current and it is easy to apply. So it widens the range of electrical method for measuring AC loss. • Integral method has the potential to realize real-time measurement of AC loss in superconducting coils, which is of great significance for the development of superconducting applications. Traditional electrical method for measuring AC loss in superconducting coil can perform well only when the high temperature superconducting (HTS) coils work with sinusoidal current. But due to the existence of harmonics, the working currents of some HTS power devices are not pure sinusoidal wave but periodic non-sinusoidal current. In order to obtain the AC loss under various periodic currents, integral method is applied in this paper. Experiments for measuring the AC loss in a coil wound from SCS4050 coated conductors are performed. AC loss measurements under sinusoidal currents, triangular currents and two highly distorted currents are investigated to explore advanced techniques for measuring the AC loss under periodic currents. The measurement results with integral method are compared with those by lock-in amplifier and those calculated by finite element model (FEM) to prove that the integral method has a high reliability. The results also show that the measured losses are dependent on the current frequency and waveform. This study widens the measuring range of electrical method. It can be employed to measure the AC loss of HTS devices under various periodic current. [ABSTRACT FROM AUTHOR]