Jin-Geun Kim

Performance Analysis of a Toroid-Type HTS SMES Adopted for Frequency Stabilization

Superconducting magnetic energy storage (SMES) can overcome fluctuations in frequency because of its fast response time in charging and discharging energy. To stabilize the fluctuations in frequency of wind power generation systems (WPGSs), HTS SMES systems should be connected to the terminal of the WPGSs. Ulleung Islands power network in Korea was modeled with a real-time digital simulator (RTDS) to demonstrate the effectiveness of SMES at stabilizing frequency. A toroid-type HTS SMES cooled by conduction cooling and a DC/DC chopper to charge and discharge current were fabricated for the experiment. The simulation results show the frequency stabilization effected by the HTS SMES system with its operational characteristics such as real time variation in current and temperature.

Design and Manufacturing of a SMES Model Coil for Real Time Digital Simulator Based Power Quality Enhancement Simulation

The Superconducting Magnetic Energy Storage (SMES) system is a key technology for overcoming the voltage sag, swell, interruption, and frequency fluctuation with the fast response speed of current charge and discharge. A toroidal-type SMES is designed using a 3D CAD program, and the inductance and AC loss characteristic during operation are analysed using Finite Element Method (FEM) program. The toroidal-type magnet consists of 30 double pancake coils (DPC). The single pancake coils (SPC), constituting the double pancake coils, are arranged at an angle of 6° from each other, based on the central axis of the toroidal-type magnet. The conduction cooling method is used for the toroidal-type SMES cooling. To evaluate the characteristics of the over-mega-joule class grid-connected HTS SMES system, the authors implemented a simulation by which the SMES coil could be connected to the Real Time Digital Simulator (RTDS). Using the simulation, users can perform voltage sag and frequency stabilization simulations with a real SMES coil in real time and easily change the capacity of the SMES system as much as they need. The effectiveness of the toroidal-type HTS SMES system is demonstrated through the RTDS-based simulation and the results are briefly discussed.

Design of HTS Transmission Cable With Cu Stabilizer

More than three HTS cable development and installation projects are proceeded over the world. A 22.9 kV/50 MVA class HTS cable system has been developed in Korea during last 3 years. And the HTS cable system for commercialization will be developed and installed on the real or test power grid within 2 years. Every HTS cable system has to satisfy the fault-current specifications of the power grid in order to protect the cable itself from the fault current. HTS cable composed of HTS tapes has some capacity of enduring the fault current by bypassing the fault-current through its Ag-sheath. But it may not be enough. So, some Cu stabilizer is generally introduced inside the conductor layers and outside the shield layers of HTS cable core for some higher fault current grade. In this paper, the design method of HTS cable with Cu stabilizer will be introduced. And the fault current capacity of HTS cable and its eddy current loss generated from the stabilizer will be calculated. And the impedance change of HTS cable in the fault current state will be calculated

Design and Mechanical Stress Analysis of a Toroidal-Type SMES Magnet

This paper investigates the mechanical stresses of a toroidal-type superconducting magnet (TSM). The TSM is designed by 3D CAD program. The Bi-2223 high temperature superconducting (HTS) wire made by soldering brass on both sides of the superconductor is used for the magnet winding. The TSM consists of 30 double pancake coils (DPC). Single pancake coils (SPC) constituting the double pancake coils are arranged at an angle of 6 from each other based on the central axis of the TSM. The mechanical stresses due to the Lorentz force caused by the operating current are analyzed using FEM. These fundamental data will effectively be applied to design a toroidal-type superconducting magnetic energy storage.

Loss Characteristic Analysis of an HTS DC Model Cable Connected to a Model VSC-HVDC System

The purpose of high-temperature superconducting (HTS) cables as the transmission conductor in a high-voltage dc transmission system is mainly to reduce the Joule losses arising from the power transmission process. However, the harmonic currents generated from the switching behavior of the voltage source converters result in power loss in the HTS dc power cable. The cable loss characteristic should be analyzed in terms of its practical applications. In this paper, the harmonic currents characteristics were analyzed in both steady and transient state. An HTS dc cable model was also developed using the finite elements method to examine its loss characteristics. The results showed that the harmonic loss of the HTS dc model cable depends on the properties of the voltage source converters, the operating dc current level, and the ac system conditions. This work will be useful in studying the loss analysis of a real HTS dc power cable.

Thermal Network Model for HTS Cable Systems and Components Cooled by Helium Gas

A versatile method to model combined electrical and thermal behavior of superconducting power devices is introduced. The methodology and computational tools of thermal network models (TNM) that use MATLAB with a Simulink toolbox primarily intended for power electronics simulations (“PLECS”) are presented. The utility of the modeling technique is demonstrated with a case study of superconducting cable termination that is cooled with gaseous helium circulation. The temperature profile in the termination due to the heat leak from the ambient and the Joule heating in the bushing and at the interfaces between copper leads and superconducting cable has been modeled. The temperature profile resulted from the TNM compared well with values obtained from experimental investigations. Suggestions for expanding the capabilities of the model are described.

Hardware-in-the-Loop Simulation for Superconducting DC Power Transmission System

When ac power is converted to dc power, the thyristor converter generates a harmonic component, creating problems that cannot be bypassed by both the ac and dc sides. This may result in ripple current in dc power transmission system and become a major problem for the current sourced HVDC transmission systems. The effects of the harmonics require serious consideration when applying an HTS dc power cable to an high voltage direct current (HVDC) system. The effect of harmonics on the HTS dc power cable was clarified by manufacturing a small scale thyristor converter system and miniaturized HTS dc power cable. This paper presents real-time simulation methods for the transient analysis of a superconducting dc transmission system. An HTS dc power cable system was analyzed using Hardware-in-the-loop simulation (HILS). This research mainly focuses on investigation of the stability of a superconducting dc cable system under a steady state and transient condition. The operating characteristics of the Jeju power system with a superconducting dc cable system are described in detail.

Quench Detection Method of HTS Model Coil Using a Series-Type Thermocouple

This paper proposes a quench detection method applied to a HTS coil and also discusses the results of tests on an HTS BSCCO wire and an HTS YBCO coil. A series-type thermocouple was fabricated to detect quench, where several thermocouples were welded in series. As the series-type thermocouple has many points of detection, variation in temperature was detected at each point by using thermo-electromotive force. The feasibility of the proposed method was investigated through the quench detection tests on the YBCO coil. This method has advantages such as a simple structure and cost effectiveness and also protects the HTS coil by detecting partial quench and its propagation.

A Novel Multi-Terminal Based Evaluation Method for an HTS DC Power Cable

High current capacity is one of the advantages of a superconducting power cable system. However, it creates difficulties when experimenting to analyze its characteristics. Short-length superconducting cables for a laboratory-scale experiment system present problems: large operating current and current distribution by terminal resistance. Experimental conditions, such as transient states, are limited by power supply capacity. In this paper, the authors suggest a new experimental method for the high-temperature superconducting (HTS) power cable to reduce the capacity of a power supply and solve current distribution problems. For the suggested method of this paper, each HTS wire has separated terminal and each HTS wire was connected in series through the separated terminal. All of HTS wires in the HTS power cable are insulated and connected in series. The cross-sectional area of the HTS power cable is the same, but the terminal structure is different. Thus, all HTS wires have the same current and cross-sectional area of HTS power cable. It is possible to test a large capacity HTS power cable under the transient state or fault conditions using a small-size power source. The design concept, configuration of the experiment system, and the experimental results were discussed in detail in this paper.

Analysis of Operational Loss Characteristics of 10 kJ Class Toroid-Type SMES

This paper describes the design results, loss analysis, and experiment testing of the real manufactured toroid-type superconducting magnetic energy storage (SMES). We analysed heat load through the conduction and radiation of the cryostat and magnetization loss caused by the charging and discharging of the toroid-type SMES system. We also measured the characteristics of toroid-type SMES under three different types of operating conditions (steady state, one-cycle charging and discharging, series charging and discharging). The fundamental design specifications and the data obtained from the experiment will be applied to a large-scale toroid-type SMES system design.