This paper reviews the modeling of high-temperature superconductors (HTS) using the finiteelement method (FEM) based on the H-formulation of Maxwell's equations. This formulation has become the most popular numerical modeling method for simulating the electromagnetic behavior of HTS, especially thanks to the easiness of implementation in the commercial finite-element program COMSOL Multiphysics. Numerous studies prove that the H-formulation is able to simulate a wide scope of HTS topologies, from simple geometries such as HTS tapes and coils, to more complex HTS devices, up to large superconducting magnets. In this paper, we review the basics of the H-formulation, its evolution from 2D to 3D, its application for calculating critical currents and AC losses as well as magnetization of HTS bulks and tape stacks. We also review the use of the H-formulation for large-scale HTS applications, its use to solve multi-physics problems involving electromagnetic-thermal and electromagnetic-mechanical couplings, and its application to study the dynamic resistance of superconductors and flux pumps.

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Overview of H -Formulation: A Versatile Tool for Modeling Electromagnetics in High-Temperature Superconductor Applications

As the critical barriers to advanced high-temperature superconducting (HTS) device technologies are overcome, practical HTS devices and systems have been enabled and become available for commercial application. In identifying the applicability of various HTS devices, their operation principles, characteristics, performance, and efficiency are fundamental. Consequently, the corresponding verification of a wide range of HTS devices, especially the HTS power devices and their system technologies, has been comprehensively carried out, and the analytical results are presented in detail towards their practical applications.

HTS Power Devices and Systems: Principles, Characteristics, Performance, and Efficiency

The high fault current of dc line is a major threat to multiterminal voltage-source-converter-based HVDC (VSC-HVDC) system. However, dc circuit breaker (DCCB) with large capacity and fast breaking speed is still under development. Therefore, fault current limitation is vital for the multiterminal VSC-HV DC system. This paper proposes a simple and easily applied hybrid current-limiting circuit (HCLC) at dc side, which consists of a current-limiting inductor (CLI) and an energy dissipation circuit (EDC) in parallel with the CLI. The CLI is designed to reduce the requirement for the DCCB's capacity and breaking speed. The EDC, which consists of thyristor-controlled resistors, is proposed to reduce the stress on energy absorption element (metal oxide arrester) in DCCB and to accelerate the fault current interruption. The design and discussion about the HCLC parameters are performed in detail. By employing the proposed HCLC, dc line fault in the multiterminal system can be isolated effectively with existing DCCB technology, and fast system restoration without power interruption of healthy part can be achieved. Numerous simulations with real-time digital simulator and comparisons with traditional schemes have demonstrated the promising performance of the proposed HCLC. The effectiveness of the HCLC's topology has also been verified by a simplified and scaled test circuit.

A Hybrid Current-Limiting Circuit for DC Line Fault in Multiterminal VSC-HVDC System

Power systems are becoming more and more complex in nature due to the integration of several power electronic devices. Protection of such systems and augmentation of reliability as well as stability highly depend on limiting the fault currents. Several fault current limiters (FCLs) have been applied in power systems as they provide rapid and efficient fault current limitation. This paper presents a comprehensive literature review of the application of different types of FCLs in power systems. Applications of superconducting and non-superconducting FCLs are categorized as: (1) application in generation, transmission and distribution networks; (2) application in alternating current (AC)/direct current (DC) systems; (3) application in renewable energy resources integration; (4) application in distributed generation (DG); and (5) application for reliability, stability and fault ride through capability enhancement. Modeling, impact and control strategies of several FCLs in power systems are presented with practical implementation cases in different countries. Recommendations are provided to improve the performance of the FCLs in power systems with modification of its structures, optimal placement and proper control design. This review paper will be a good foundation for researchers working in power system stability issues and for industry to implement the ongoing research advancement in real systems.

https://www.mdpi.com/1996-1073/11/5/1025/pdf

Fault Current Limiters in Power Systems: A Comprehensive Review

This work covers the high-temperature superconducting (HTS) technologies based on the highlights in recent achievements in the applied HTS field in China. Its comprehensive coverage includes practical HTS material manufacturing and characterization, large-scale applications, and electronic applications. The applied HTS technologies have been well enabled to build applicable devices, and their characteristics have been well verified in the HTS devices developed to be industrialized for practical applications. The highlighted HTS devices and their performance details reveal the trend and the necessary improvement required to reach the goal of industrial applications of HTS technologies.

Enabling High-Temperature Superconducting Technologies Toward Practical Applications

We have been carrying out a saturable iron core reactive type superconducting fault current limiter (SFCL) development program since 2002. The major two disadvantages that people used to be foretold for a saturable iron core reactive type SFCL are the massive use of iron (resulting in large size, heavy weight, and high cost) and the high induced voltage hazard to the dc superconducting coil (this may damage the current supply of the dc bias) as a fault takes place. We have found the ways to deal with these two problems, making such kind of equipment reliable and cost effective. In this paper, we will report the technical data and testing results of a 3 phase lab testing model. Some key design parameters of the 35 kV/100 MVA prototype will also be presented.

Development of Saturated Iron Core HTS Fault Current Limiters

A 220 kV/300 MVA saturated iron-core superconducting fault current limiter (SI-SFCL) has been successfully manufactured and installed at Shigezhuang substation in Tianjin, China Because it is the first time SI-SFCL has been used at such a high voltage level, extensive testing was carried out to assess the safety and functional performance of the device in the HV power grid Two categories of tests were conducted at the factory before the SFCL was shipped to the installation site One was to examine whether the device met the relevant industrial standards, such as lightning impulse, high voltage withstanding, partial discharging, and temperature rising, etc The other was to determine the functional performance and key operational parameters, such as measuring steady impedance, magnetizing and demagnetizing the superconducting coil, and so on Following the completion of the installation at the substation, field tests were performed to re-confirm performance after the stages of disassembly, shipment, and reassembly on site This paper introduces the major results of these tests

Factory and Field Tests of a 220 kV/300 MVA Statured Iron-Core Superconducting Fault Current Limiter

A dc magnetization system, comprises a HTS dc bias coil, a current source, a high-speed switch, and an energy release circuit, was built for a 35 kV/90 MVA saturated iron-core fault current limiter to enhance its functional capability and reliability and to reduce its size and weight. The dc bias coil is made of high temperature superconducting silver sheathed Bi-2223 tapes with a magnetization capacity of 141,000 ampere ldr turns. The current source is able to supply a maximum of 350 A constant current. The energy release circuit was designed to quickly discharge the magnetic energy of the saturated iron cores and to suppress the voltage surge across the dc coil when the magnetization circuit was switched to open in a short-circuit event. This controllable magnetization system enables the fault current limiter to respond to a short-circuit fault in one millisecond, to reach full current limiting function in 5 milliseconds, and to re-saturate the iron cores in 800 milliseconds after the clearance of a fault. In this paper, we introduce the configuration and specifications of the system. Some experimental results are also reported.

DC Magnetization System for a 35 kV/90 MVA Superconducting Saturated Iron-Core Fault Current Limiter

A core-saturated superconductive fault current limiter and a control method of the fault current limiter. The fault current limiter includes a superconductive magnet (2), a core (4), an AC winding (5), a cryostat system, a monitor system (7) and a DC control system (6). The output of the DC control system (6) is connected to the two terminals of the superconductive magnet (2). The DC control system (6) is also connected to the monitor system (7). The core (4) has an unequal section core structure. The control method includes: controlling the current which is flowing through the superconductive magnet (2) for limiting the fault current in the power net (1) in the case of a short circuit fault event.

Core-saturated superconductive fault current limiter and control method of the fault current limiter

The current limiter includes following parts: iron core set including two or more paired identical i«„…i» shaped iron cores prepared by piling silicon steel sheets; AC winding sheathed outside core leg, all AC windings in each phase cascaded are connected to AC power network in series; superconductive DC winding encircling all core legs inside iron core, and connected to constant DC power source; short circuit auxiliary winding placed at inside or outside superconductive DC winding, matched to superconductive DC winding in shape; induction breaker connected to DC loop of superconductive DC winding; Dewar is as a low temperature container, and the said all superconductive DC windings are put its vacuum cavity. The disclosed current limiter possesses features of fast response, quick speed for restricting short circuit current, simple structure, safe and reliable operation.

Xiaoye Niu

Papers

Development of Saturated Iron Core HTS Fault Current Limiters

Factory and Field Tests of a 220 kV/300 MVA Statured Iron-Core Superconducting Fault Current Limiter

DC Magnetization System for a 35 kV/90 MVA Superconducting Saturated Iron-Core Fault Current Limiter

Core-saturated superconductive fault current limiter and control method of the fault current limiter

Quick current limiting type superconductive short circuit fault