Kideok Sim

A Study on the Operating Characteristics of SMES for the Dispersed Power Generation System

WPGS (Wind Power Generation System) output fluctuates due to wind speed variations and PV power generation output is changed by sudden cloudy weather conditions. Hence, if a large number of wind and PV power generators are connected to power system, their output can cause a serious influence on the power system operation, that is, frequency and voltage fluctuations. In order to solve these problems, the control of generator output fluctuations is very important. With these points as background, Superconducting Magnetic Energy Storage (SMES) is probably a key technology to overcome these fluctuations. For stabilization of power, the SMES is connected to the terminal of the WPGS. The authors compared the load side frequencies under the 1 MJ and 2.5 MJ of SMES connection, respectively. From the simulation results, it can be concluded that the SMES is a very effective device for stabilization of power system and minimization of frequency fluctuations.

Operating Characteristic Analysis of HTS SMES for Frequency Stabilization of Dispersed Power Generation System

This paper analyses operating characteristic of high temperature superconducting magnetic energy storage (HTS SMES) for frequency stabilization of dispersed power generation system. The wind power generation system (WPGS) fluctuates due to wind speed variation and affects the frequency and voltage fluctuations of the utility. SMES is probably a key technology to overcome these fluctuations. To stabilize power system frequency, a large-scale HTS SMES is connected to the terminal of the WPGS. The authors analysed the load side frequencies using two different configurations of SMES, one consisting of a single magnet and the other of a dual magnet. From the simulation results, it can be concluded that the SMES is a useful device for stabilizing the power system frequency fluctuations, and a dual magnet type SMES is more effective for frequency stabilizing but exhibits more AC loss due to the increased operating current than a single magnet type.

Development and testing of 30 m HTS power transmission cable

To obtain realistic data on HTS power cable, single-phase 30 m long, 22.9 kV class HTS power transmission cable system have been developed by Korea Electrotechnology Research Institute (KERI) and LG cable Ltd. that is one of 21st century frontier project in Korea. The HTS cable consists of Ag/Bi-2223 tapes, high voltage insulation paper which is impregnated by LN/sub 2/. The cable is rated at 22.9 kV, 50 MVA, 60 Hz and is cooled with pressured liquid nitrogen at temperature from 70 to 80 K. This paper describes the results of design, fabrication and evaluation of the single-phase, 30 m HTS power cable system.

Design and Experimental Results of a 3 Phase 30 m HTS Power Cable

HTS power cables appear to be the replacement and retrofitting of underground cable in urban areas and HTS power cable offers a number of technical and economic merits compared to normal conductor cable system. A 3 phase 22.9 kV, 50 MVA class HTS power cable system have been developed by Korea Electrotechnology Research Institute (KERI), LS Cable Ltd. and Korea Institute of Machinery and Materials (KIMM) that is one of 21st century frontier project in Korea. The 30 m long cable with 3 cores in 1 cryostat has been manufactured and installed to conduct long-term reliability test. The HTS power cable consists of two layers of phase conductor and two layers of shield used Ag/Bi-2223 tapes and polypropylene laminated paper is used in LN2 as electrical insulation. A HTS power cable has been tested with DC and rated current and voltage in pressurized liquid nitrogen. The evaluation results clarify good performance of HTS cable and these results prove that the HTS power cable has the basic electrical properties for 22.9 kV HTS power cable. This paper describes the results of developmental the 30 m, 3 phase, 22.9 kV, 50 MVA HTS power cable in Korea

De-Lamination Characteristics of Coated Conductor for Conduction Cooled HTS Coil

According to the continuous development of coated conductors and compact cryocoolers, research and development efforts for High Temperature Superconducting (HTS) magnets are increasing using conduction cooling method. To increase the cooling efficiency and thermal stability of the HTS magnet, the coated conductor is wound by wet-winding or epoxy impregnating in vacuum after dry-winding. Due to the large Lorentz force and thermal contraction, stress analysis of the composite material, which is composed of HTS conductor, insulation layer and epoxy layer, is necessary to assure the mechanical stability of the HTS magnets. Mechanical strength for a/b axis, which is parallel to the conductor surface, is usually strong enough to endure the large tensile stress due to the tough substrate material. However, c-axis strength, which is perpendicular to the conductor surface, is not strong enough to ensure the large Lorentz force. The de-lamination of the multi-layered HTS tape in a coil structure can occur and the results were previously reported. Therefore, the test data for allowable c-axis strength is necessary to design the mechanical stability of the HTS coil. This paper describes the experimental results for the c-axis tensile strength of various coated conductors. The results show the wide divergence of the c-axis tension force from 18 MPa to 53 MPa. Through the FEM analysis for multi-layered structure of the HTS tape, concept design for HTS tape of enhanced c-axis strength is suggested.

Critical Current, Critical Temperature and Magnetic Field Based EMTDC Model Component for HTS Power Cable

Before applying the high temperature superconducting (HTS) power cable to real utility network, system analysis should be performed using simulation tools. For the practical use of HTS devices in electrical power system, prior simulation analysis is very important. PSCAD/EMTDC simulation is one of the most popular and useful analysis tools for electrical power system. Unfortunately the model component for HTS power cable is not provided in the PSCAD/EMTDC simulation tool. In this paper, EMTDC model component for HTS power cable has been developed considering critical current, critical temperature, magnetic field, and recovery time constant which depend on the sorts of HTS wire. The numerical model of HTS power cable in the PSCAD/EMTDC was designed by using the real experimental data obtained from a real HTS 1G wire test. The utility application analysis of HTS power cable was also performed using the model component developed. The component for HTS power cable could be variously used when the power system includes HTS power cable, especially it will be readily analyzed by the PSCAD/EMTDC in order to obtain the data for the level of fault current, power flow, and power losses, and so on.

Investigation on the Thermal Behavior of HTS Power Cable Under Fault Current

During the operation of HTS power cable, large fault current can be introduced to a HTS power cable due to several accidents. In this case, a circuit breaker limits the fault current to protect the HTS power cable just as conventional power cables. However, heat is necessarily generated until the circuit breaker operates and severe performance degradation or even burn-out can occur at HTS tapes. To ensure the safety against the fault current, thermal characteristic of the HTS power cable should be verified under the fault current. Several experiments with a simple cable are performed using an AC pulse power supply. During the experiment, the increase of temperature and current redistribution are measured for the various fault current conditions. Through the experiments, safety margin of Korean HTS power cable is verified and the allowable peak current is suggested

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.

AC Loss Analysis of HTS Power Cable With RABiTS Coated Conductor

Numerical analysis of AC loss for a HTS power cable is investigated using commercial FEM software package. AC loss of the HTS power cable, which is made by 2 G conductor, is hard to experimentally measure due to very small signal compared to that made by 1G conductor. The FEM model describes current distribution and AC loss inside the HTS conductor for the AC transport current through nonlinear E-J correlation. For the verification of the AC loss analysis model, the results were compared with the well known analytic solution of a single strip HTS conductor and experiments. Unlike IBAD substrate, magnetization of the RABiTS has influence on the precise estimation of the AC loss and it is also considered in the FEM model. Moreover, several conductors should be stacked to meet the large transport current because of the small critical current at present and the effect of stacking configuration is also investigated. In this paper, AC loss analysis results are presented for various HTS power cable configurations such as stacking directions. The results are compared with the experimental results of a model HTS power cable and the best configuration to minimize AC loss is suggested.

Design and Performance Evaluation of a Multi-Purpose HTS DC Induction Heating Machine for Industrial Applications

In general, conventional induction heating system is designed only for a specific metal billet or object, because the heating system should be specialized to guarantee the best performance regarding heating quality and efficiency. It has been applied to large heating systems in metallic processing industries. A DC induction heating method using HTS magnets can be one of the better counterplans for higher efficiency and multi-purpose heating system. In this paper, we evaluated a performance of a 10 kW-class multi-purpose HTS DC induction heating machine without additional function or equipment, and performed efficiency analysis on various metals, including aluminum, copper, and iron billets. In addition, heating characteristics of other materials were simulated and analyzed through finite elements method (F.E.M.) models. The results demonstrate that the 2G HTS DC induction heating machine is applicable for all the ferrous and nonferrous metals and useful for large scale industrial applications.