• Proceedings of the KIEE Conference
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• 2006.05a
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• pp.48-50
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• 2006

SC(Static Condenser) in KEPCO is used in voltage control and power factor compensation. Currently KEPCO uses SC to 154kv 50MVA and 23kv SMVA. It is not important in old days because a SC bank accident has no effect on power system. But we are interested in the SC bank for power quality in these days. The SC Bank has a reactor and a condenser using series connection. It is operated in critical point for resonance circuit normally. Therefore the SC bank has a small reliability against other Power instruments. If a 4th harmonic frequency as a resonance frequency is supplied in system, the condenser is damaged because of a resonance current. And a trip and a closing for CB(Circuit Breaker) in many times will have a big influence of SC bank destruction. General OCR(Over Current Relay) observing SC bank is not useful for this protection We think that protection relay must be have the SC bank characteristics. A solution for this problem is active Power, resonance frequency and impedance.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.18 no.7
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• pp.610-614
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• 2005

In this paper, simple AT-cut crystal resonator utilizing $Bi_{0.5}(Na_{0.84}K_{0.16})_{0.5}TiO_3$ relaxator ceramics as load capacitator were designed and their frequency-temperature characteristics were investigated. In order to modify temperature dependance of dielectric constant, $Bi_{0.5}(Na_{0.84}K_{0.16})_{0.5}TiO_3$ ceramics were manufactured with the variations in Sr substitution. At the composition with $6\;mol\%$ Sr substitution as load capacitator, frequency-temperature characteristics of AT-cut crystal resonators with the series load capacitance were similarly varied as those of cut orientation variation, and also compensated.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.17 no.8 s.111
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• pp.713-718
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• 2006

We designed and fabricated, in this paper, a quintuple band folded monopole antenna for the mobile phone handset that can be provided multiple mobile services. Antenna design was based on the compensation of series antenna capacitance with the expansion of physical antenna length by the proper folding structure. It's shown that this antenna satisfies quintuple service band as CDMA/GSM/DCS/USPCS/WCDMA, and is more cost competitive than conventional metal plate pressing method by applying on flexible PCB technology. Measured maximum gain on quintuple band were $-2.51{\sim}+1.82 dBi$, and radiation patterns were also shown nearly omnidirectional on all bands.

• Journal of the Korean Solar Energy Society
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• v.29 no.6
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• pp.1-13
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• 2009

Photovoltaic conditioning systems normally use a maximum power point tracking (MPPT) technique to deliver the highest possible power to the load continuously when variations occur in the insolation and temperature. A unique method of tracking the maximum power points (MPPs) and forcing the boost converter system to operate close to these points is presented through deriving small-signal model and transfer function of boost converter considering input capacitor. This paper aims at modeling boost converter including fairly large equivalent series resistance(ESR) of input reservoir capacitor by state-space-averaging method and PWM switch model and compares both methods using Bode plots. In the future, properly designed controller for compensation will be constructed in 3kw real system for maximum photovoltaic power tracking control.

• Proceedings of the KIPE Conference
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• 2003.07b
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• pp.896-899
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• 2003

The electric railway has been widely used as a transportation all over the world. It also was opened in 1973 in korea and it has been steadily proceeded in making electric railway network for a big city and building Keongbu high speed , electric railway. That's why the system of electric railway is able to solve the environmental pollution and operate the useful energy in environmental ways, it helps to increase the ability of transportation and to decrease the cost. Because of the advantage of making the economic situation better, the system of electric railway is trying to do their best in developing technique of electric railway. Because of the increasing of transportation and the high speed operation, cars with regenerative braking system was adapted. Therefore, unbalanced voltage and current of three phase system and the drop and rise of voltage of feeding circuit is expected. Now that building the substation, newly spends lots of costs and time, it is a very difficult situation to solve the problem. We can guess that electric railway line can't receive power from the power system of bigger size in building newly electric railway. In this paper, it was proved that series voltage compensator was suitable as a solution according to voltage drop and voltage fluctuating through computer simulation.

• Journal of Korea Society of Digital Industry and Information Management
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• v.14 no.1
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• pp.77-85
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• 2018

This paper proposes a robust digital video stabilization algorithm to extract and track an object, which uses a phase correlation-based motion correction. The proposed video stabilization algorithm consists of background stabilization based on motion estimation and extraction of a moving object. The motion vectors can be estimated by calculating the phase correlation of a series of frames in the eight sub-images, which are located in the corner of the video. The global motion vector can be estimated and the image can be compensated by using the multiple local motions of sub-images. Through the calculations of the phase correlation, the motion of the background can be subtracted from the former frame and the compensated frame, which share the same background. The moving objects in the video can also be extracted. In this paper, calculating the phase correlation to track the robust motion vectors results in the compensation of vibrations, such as movement, rotation, expansion and the downsize of videos from all directions of the sub-images. Experimental results show that the proposed digital image stabilization algorithm can provide continuously stabilized videos and tracking object movements.

• Journal of the Korean Society of Industry Convergence
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• v.23 no.4_1
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• pp.559-567
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• 2020

As the renewable energy market grows, grid-connected inverters have been improving and expanding in several fields in recent years because energy conversion devices are the main components of solar systems. In this paper, a high-precision new grid-connected three-phase inverter system is proposed. The proposed system consists of a main inverter, a sub inverter and a transformer. The main inverter operates at a low switching frequency and high power and transmits power to the grid. A sub-inverter connected in series with the transmission line through a matching transformer operates at lower power than the main inverter to provide input values to the transformer. The transformer acts as a power supply according to the voltage compensation value. This study is based on the principle of operation of the UPFC(Unified Power Flow Controller) structure used to regulate power flow in AC transmission lines. The grid-connected inverter system proposed in this paper is implemented with high precision and high resolution. The proposed system was verified through its ability to enhance and ensure the safety of the proposed system through simulation and experiment.

• KIEE International Transactions on Power Engineering
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• v.4A no.3
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• pp.129-133
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• 2004

This paper deals with the design and implementation of a TCSC (Thyristor Controlled Series Capacitor) simulator, which is a module for an analog type power system simulator. Principally, it presents configuration of controller hardware/software and its experimental results. An analog type power system simulator consists of numerous power system components, such as various types of generator models, scale-downed transmission line modules, transformer models, switches and FACTS (Flexible AC Transmission System) devices. It has been utilized for the verification of the control algorithm and the study of system characteristics analysis. This TCSC simulator is designed for 50% line compensation rate and considered for damping resister characteristic analysis. Its power rate is three phase 380V 20kVA. For hardware extendibility, its controller is designed with VMEBUS and its main CPU is TMS320C32 DSP (Digital Signal Processor). For real time control and communications, its controller is applied to the RTOS (Real Time Operation System) for multi-tasking. This RTOS is uC/OS-II. The experimental results of capacitive mode and inductive mode operations verify the fundamental operations of the TCSC.

• Proceedings of the KIEE Conference
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• 2001.04a
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• pp.349-352
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• 2001

FACTS technology is developed into the sophisticated system technology which combines conventional power system technology with power electronics, micro-process control, and information technology. Its objectives are achieving enhancement of the power system flexibility and maximum utilization of the power transfer capability through improvements of the system reliability, controllability, and efficiency [1]. As a series and shunt compensator, UPFC consists of two inverters with common dc link capacitor bank. It controls the magnitude of shunt bus voltage and real and reactive power flow of transmission line[2]. In this paper, we present the design, implementation and test results of developed 20kVA level prototype UPFC. It is applied to power system simulator and controls the real and reactive power flow and shunt bus voltage magnitude.

• Korean System Dynamics Review
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• v.15 no.3
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• pp.61-79
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• 2014

This paper deals with system thinking in the resilience of the SES (Social-Ecological Systems) around Mt. Gariwang, located in Jeongseon County, Gangwon Province, in particular with the disturbance that a new ski slope is planned to be built for the PyeongChang 2018 Winter Olympic. It first performs a literature survey and newspaper article search to summarize the controversy with regards to credible environmental and socio-economical impacts of the plan, and then elaborates a series of CLDs (Causal Loop Diagrams) to infer the dynamics of the impacts. The results imply that the natural restoration seems to be hard because the development activities can cause a great deal of damage to the ecosystem mainly due to soil degradation and the mitigation of icy valley effects with water exploitation for making artificial snow and so on. Moreover most of the households near the planned site seem to leave with land compensation, thus more policy efforts are needed to enhance the resilience of the ecosystem and the nearby society based on ecotourism.