• Journal of the Korean Solar Energy Society
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• v.29 no.5
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• pp.65-72
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• 2009

The new method is proposed to improve high speed detection of grid voltage phase and magnitude during a voltage dip due to a grid faults. Usually, A LPF(Low Pass Filter) is used in the feedback loop of PLL (Phase Locked Loop) system because the measured grid voltage contains harmonic distortions and sensor noises. so, a new design method of the loop gain of the PI -type controller in the PLL system is proposed with the consideration of the dynamics of the LPF. As a result, a better transient response can be obtained with the proposed design method. The LPF frequency and PI controller gain are designed in coordination according to the steady state and dynamic performance requirement. This paper shows the feasibility and the usefulness of the proposed methods through the computer simulation and the lab-scale experiments.

• Progress in Superconductivity and Cryogenics
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• v.11 no.3
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• pp.55-59
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• 2009

In attempts to closely study the effect of high efficiency, friendly environment HTS(High Temperature Superconducting) cable and SFCL(Superconducting Fault Current Limiters) on power system, several projects were carried out around the world. Promising results have been achieved in terms of cable capacity and reliability. commercial HTS cable and SFCL, however, must not only be only be feasible, but meet practical requirements as well. To facilitate the transition of HTS cable technology from the Lab. to the Real Grid, a New project for applying 22.9kV HTS cables and SFCL to the commercial Power Grid supported by Government has just started in KEPCO. Target of this project is to operate two 22.9kV, 50MVA, 150MVA HTS cables and two 22.9kV 630A, 3000A SFCL in a KEPCO Grid in order to demonstrate its reliability and stable operation. This paper will present the technology for selecting appropriate site and its plan for installation & operating of 22.9kV HTS cables & SFCL in KEPCO Grid.

• Journal of the Korean earth science society
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• v.32 no.6
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• pp.640-653
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• 2011

We simulate the propagation of earthquake waves in the continental margin of Antarctica using the elastic wave modeling algorithm, which is modified to be suitable for acoustic-elastic coupled media and earthquake source. To simulate the various types of earthquake source, the staggered-grid finite-difference method, which is composed of velocity-stress formulae, can be more appropriate to use than the conventional, displacement-based, finite-difference method. We simulate the elastic wave propagation generated by earthquakes combining 3D staggered-grid finite-difference algorithm composed of displacement-velocity-stress formulae with double couple mechanisms for earthquake source. Through numerical tests for left-lateral strike-slip fault, normal fault and reverse fault, we could confirm that the first arrival of P waves at the surface is in a good agreement with the theoretically-predicted results based on the focal mechanism of an earthquake. Numerical results for a model made after the subduction zone in the continental margin of Antarctica showed that earthquake waves, generated by the reverse fault and propagating through the continental crust, the oceanic crust and the ocean, are accurately described.

• Proceedings of the KIEE Conference
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• 1999.07e
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• pp.2352-2354
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• 1999

The purpose of substation grounding system is to provide reference potential with power system and protect field workers from electrical shock resulted from unsymetrical power system faults. For this purpose, grounding grid should be designed to maintain max, touch voltage under safety criteria in fault conditions. It is difficult, however, to design a safe grounding grid at very resistive or narrow area. This paper describes an example of substation grounding grid design procedures in such areas with very severe design conditions. By using grounding conductors, which is located close to earth surface, earth surface potential could be controlled effectively, so that maximum touch voltages is to be maintained under safety criteria.

• The Transactions of The Korean Institute of Electrical Engineers
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• v.60 no.2
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• pp.239-244
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• 2011

Due to large demand, the increase of fault current has caused the capacity of power machines in power grid to increase. Among several countermeasures, the superconducting fault current limiter (SFCL) has been noticed as one of the promising countermeasures to solve these problems. However, in spite of excellent current limiting performances of the SFCL, the application of SFCL to power system has been delayed due to both the limited space for the SFCL's installation and its longer recovery time after the fault removal. In order to solve these problems, a hybrid type SFCL was developed. In this paper, we studied the operation characteristics of the hybrid SFCL with first half cycle non-limiting operation by modelling using PSCAD/EMTDC and experiment. It was shown through the simulation using PSCAD/EMTDC and the simulated experiment that the fault current limiting and the fast recovery operations of the hybrid SFCL with the first half cycle non-limiting operation were achieved.

• Journal of KIISE:Computer Systems and Theory
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• v.35 no.5
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• pp.187-198
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• 2008

This paper develops a framework for efficient resource management within the grid service environment. Resource management is the core element of the grid service; therefore, GridRMF(Grid Resource Management Framework) is modeled and developed in order to respond to such variable characteristics of resources as accordingly as possible. GridRMF uses the participation level of grid resource as a basis of its hierarchical management. This hierarchical management divides managing domains into two parts: VMS(Virtual Organization Management System) for virtual organization management and RMS(Resource Management System) for metadata management. VMS mediates resources according to optimal virtual organization selection mechanism, and responds to malfunctions of the virtual organization by LRM(Local Resource Manager) automatic recovery mechanism. RMS, on the other hand, responds to load balance and fault by applying resource status monitoring information into adaptive performance-based task allocation algorithm.

• The Transactions of The Korean Institute of Electrical Engineers
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• v.63 no.9
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• pp.1219-1226
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• 2014

This paper introduces a hardware simulator for the LVRT operation analysis of the grid-tied PMSG wind power system with a power dissipation circuit. The power dissipation circuit, which is composed of chopper and resistor, suppresses the sudden increase of DC-link voltage in the back-to-back converter of the grid-tied PMSG wind power system. The LVRT operation was first analyzed using computer simulations with PSCAD/EMTDC. A wind power simulator including the power dissipation circuit and the fault simulator composed of variac and IGBT were built to analyze the LVRT operation. Various experiments were conducted to verify the effectiveness of the power dissipation circuit for the LVRT operation. The developed hardware simulator can be extensively utilized for the analysis of various LVRT operations of the grid-tied wind power system.

• Progress in Superconductivity and Cryogenics
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• v.12 no.3
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• pp.34-38
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• 2010

Until now some countries including South Korea have made big progress and many efforts in the development of high temperature superconductor (HTS) power equipments. Especially, HTS Cable and superconducting fault current limiter (SFCL) are the strongest candidates among them from the viewpoint of applying to real grid. In South Korea, HTS cable and SFCL have been installed in test fields and tested successfully at Gochang PT Center of KEPCO. In order to meet practical requirements and be feasible in real grid, a demonstration project for HTS cable and SFCL systems, called GENI(green superconducting electric power network at Icheon substation) project, has been initiated to install 23kV HTS cable and SFCL systems in a utility network in South Korea since 2008. Namely, it says the first demonstration project for the application HTS system to real smart grid in South Korea. This paper presents the design and the application plan of the 22.9kV HTS cable and SFCL in 154kV Icheon substation in South Korea with the viewpoint of applying in Smat Grid.

• Journal of IKEEE
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• v.24 no.3
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• pp.691-698
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• 2020

The installation cost or the magnitude of the fault current varies depending on the grid connection method of the offshore wind farm. Therefore, there is a need for an efficient power grid connection method considering the capacity and location of the complex. In particular, most power cables in offshore wind farms use 3-core considering cost and efficiency. In the event of a failure such as a short circuit, the entire cable must be replaced, which can lead to significant losses in terms of cost, considering repair costs and turbine downtime. Therefore, in this paper, a radial, ring, and molding method is introduced into a 100 MW wind farm to be installed at Jeju offshore, and a three-phase short circuit failure is performed using a PSCAD/EMTDC program to perform computer analysis. I would like to propose a suitable power grid connection method.

• The Journal of the Korea institute of electronic communication sciences
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• v.12 no.6
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• pp.1107-1114
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• 2017

In this paper, a miniaturized distribution line was experimentally made. The smart grid distribution system was modeled by analyzing the distribution system, and a miniaturized micro three phase distribution system recloser was designed. The micro recloser was designed as a sensor part, a main part and a relay part, and the main part was designed to cut off the fault current by determining the fault from the input current based on the DSP. Finally, based on the results of the modeling, the micro three phase power distribution line and the micro three phase recloser were experimentally fabricated, and the basic making technology of the miniaturized micro smart grid was obtained through the making process.