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Unpredictable power fluctuation and fault ride-through capability attract increased attention as two uncertain major factors in doubly-fed induction generators (DFIGs) integrated DC power system. Present solutions usually require complicated cooperation comprising multiple modules of energy storage, current control, and voltage stabilizer. To overcome the drawbacks of existing solutions, this paper proposes a superconducting magnetic energy storage (SMES) integrated current-source DC/DC converter (CSDC). It is mainly composed of a current-source back-to-back converter, and the SMES is tactfully embedded in series with the intermediate DC link. The proposed SMES-CSDC is installed in front of the DC-DFIG to carry out its dual abilities of load voltage stabilization under multi-farious transient disturbances and power regulation under wind speed variations. Compared with the existing DC protection devices, the SMES-CSDC is designed on the basis of unique current-type energy storage. It has the advantages of fast response, extensive compensation range, concise hardware structure, and straightforward control strategy. The feasibility of the SMES-CSDC is implemented via a scaled-down experiment, and its effectiveness for DC-DFIG protection is verified by a large-scale DC power system simulation.

Using hybrid energy storage system (HESS) to solve the issues of power regulation and fault protection of DC microgrids has attracted extensive attention. To realize multiple functions of power flow control and power quality enhancement of the DC microgrid, a concept of distributed HESS based on superconducting magnetic energy storage (SMES) and battery energy storage (BES) is introduced in this paper. A SMES-based energy-storage-composited DC transformer (ESDCT) is designed to interconnect the low-voltage DC microgrid into a medium-voltage DC power system. It is with the functions of DC voltage transformation, and grid fault isolation. The BES is selected to regulate the unstable output power of the LVDC microgrid caused by renewable energy generators and load variations. The modeling of the SMES-based ESDCT and the cooperative control of the BES and SMES is analyzed. Finally, the performance of the SMES/BES distributed HESS is verified via a simulation, and the feasibility of the proposed SMES-based ESDCT is demonstrated via a scaled-down experiment.

A dual-function series-connected compensator based on superconducting magnetic energy storage (SMES-based SCC) is proposed for a photovoltaic microgrid. The SMES-based SCC can operate in two different modes: dynamic voltage restorer for voltage fluctuation and fault current limiter for short-circuit fault. The SMES provides/absorbs power to/from the common DC-link capacitor by a DC/DC converter under different modes with fast response speed. In order to achieve better tracking performance to reference voltage and overcome the drawback of the conventional control methods, a modified sliding mode controller based on SVPWM strategy (SMSVM) is proposed for control of the SCC. The performances of the SMES-based SCC under different operation modes are evaluated through a series of simulation results and its superiority is verified by comparing it to a battery energy storage-based SCC. Simulation and comparative analyses between the proposed SMSVM method and the conventional hysteresis control method are conducted to prove the validity and superiority of the SMSVM method.

A superconducting energy pipeline cooled during its clean energy transferring becomes attractive recently to be a promising alternative way for combined green energy transmission to meet the ever-rising energy demand across the world. Though, study on superconducting energy pipelines gets into the conceptual design of single energy integration, the critical multi-composite structure and its characteristics have not yet been systematical. A novel high-temperature superconducting (HTS) energy pipeline integrated with power cable and liquid hydrogen (LH2) and liquefied natural gas (LNG) is proposed in this paper. The maximum allowable temperature difference and pressure drop methods are adopted to design the pipeline. A two-dimensional axisymmetric electromagnetic thermal coupling model has been established using the finite element method. The interface magnetic field formulation, heat transfer modeling, and multiphysics interface has been applied to conduct a detailed analysis of the designed superconducting energy pipeline (LH2-LNG-HTSEP). The results show that the designed LH2-LNG-HTSEP is feasible for practical operation and has more favorite characteristics to suit the HTS cable for the composite pipeline operation. The model and analysis method provide a theoretical base for the composite superconducting energy pipeline design and structural optimization.

Over time, high-temperature superconductor (HTS)-coated conductors (CCs) have proven to be promising candidates for future high-efficiency and high-power density electrical machines. However, their commercialization is handicapped due to the AC dissipative loss that occurs upon exposure to external magnetic fields. In rotating electromagnetic devices, the external magnetic field is a combination of alternating and rotating magnetic fields. Most of the research is devoted to the effect of exposure of the superconductors to alternating magnetic fields only. This article presents an investigation to observe the behavior of HTSCCs under rotating magnetic fields, particularly the AC loss, using a finite-element-based homogeneous H-formulation technique. Our investigation shows that the AC loss could be considerably high when HTSCCs are exposed to rotating magnetic fields and, ultimately, could affect the cooling efficiency of future high-efficiency and high-power density electrical machines.

The development of DC custom power protection devices is still in infancy that confines the sensitive loads integrated into medium-voltage (MV) and low-voltage (LV) DC networks. Considering the DC doubly-fed induction generator (DC-DFIG) based wind energy conversion system (WECS), this paper proposes a dual active bridge (DAB) based DC unified power quality conditioner (DC-UPQC) with the integration of super-conducting magnetic energy storage (SMES) to maintain the terminal voltage of DC-DFIG and regulate the current flow. The principle of the proposed DC-UPQC has three parts, i.e., parallel-side DAB (PDAB), series-side DAB (SDAB), and SMES, used for the voltage compensation, current and power regulation, and energy storage, respectively. The circuit principle of the PDAB and SDAB and the modeling of SMES are analyzed in this paper. A DC dual control strategy is also proposed to deal with the DC voltage oscillation generated by the AC-side asymmetrical fault. A case study of DC-DFIG interfaced with DC power grid is carried out, integrated with the proposed SMES-based DC-UPQC to verify the high-power applications of the proposed structure. Finally, an experiment is implemented, and the results demonstrate the correctness of the theoretical analysis and the feasibility of the proposed structure.

High-temperature superconducting materials have shown great potential for the design of large-scale industry applications. However, they are complicated under AC conditions, resulting in penalties such as power loss or AC loss. This loss has to be considered in order to design reliable and efficient superconducting devices. Furthermore, when superconductors are used in rotating machines, they may be exposed to rotating magnetic fields, which is critical for the design of such machines. Existing AC loss measuring techniques are limited to measuring under one-dimensional AC magnetic fields or transport currents. Therefore, it is essential to develop and investigate robust experimental techniques to investigate the loss mechanism in HTS machines. In this paper, a new and novel experimental technique has been presented to measure AC loss in rotating magnetic field conditions. The loss under rotating magnetic fields is measured and compared by numerical modeling methods, and the results show a strong correlation with the numerical modeling and show the effectiveness of the experimental setup.

High-temperature superconductor (HTS) bulks have shown very promising potential for industrial applications due to the ability to trap much higher magnetic fields compared to traditional permanent magnets. In rotating electrical machines, the magnetic field is a combination of alternating and rotating fields. On the contrary, all studies on electromagnetic characterization of HTS presented in the literature so far have only focused on alternating AC magnetic fields and alternating AC loss due to the unavailability of robust experimental techniques and analytical models. This paper presents a numerical investigation on the characterization of HTS bulks subjected to rotating magnetic fields showing AC loss, current density distribution in three-dimensional axes, and trapped field analysis. A three-dimensional numerical model has been developed using H-formulation based on finite element analysis. An HTS cubic sample is magnetized and demagnetized with two-dimensional magnetic flux density vectors rotating in circular orientation around the XOY, XOZ, and YOZ planes.

The high-temperature superconductor (HTS) has been recognised as one of the most up-and-coming materials thanks to its superior electromagnetic performance (e.g., zero resistance). For a high-speed maglev, the HTS magnet can be the most crucial component because it is in charge of both the levitation and the propulsion of the maglev. Therefore, a fundamental study of HTS magnets for maglev is crucial. This article presents the fundamental design and modelling of the superconducting magnet for a high-speed maglev, including mechanics, electromagnetics, and loss analysis during instability. First, the measurements of the superconducting wire were performed. The HTS magnet was primarily designed and modelled to fulfil the basic electromagnetic requirements (e.g., magnetic field) in order to drive the maglev at a high speed. The modelling was verified by experimental tests on a scale-down HTS magnet. A more professional model using the H-formulation based on the finite element method (FEM) was built to further investigate some deeper physical phenomenon of the HTS magnet (e.g., current density and loss behaviours), particularly in situations where the high-speed maglev is in the normal steady state or encountering instability.

A single-sided high temperature superconducting (HTS) linear synchronous motor (HTSLSM) has been developed with a pulse magnetization system to obtain the HTS bulk magnet array with alternating magnetic poles for the motor secondary. In order to identify the trapped field characteristics of the HTS bulk magnet exposed to the external traveling-wave magnetic field generated by the primary of the HTSLSM, a measurement system has been built up and the relevant experiments have been carried out. The relationships between the trapped field attenuation of the HTS bulk magnet and the amplitude, frequency and acting direction of the external traveling-wave magnetic field are experimentally obtained to allow the HTSLSM characteristics to be practically verified. [ABSTRACT FROM AUTHOR]