• Proceedings of the KIEE Conference
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• 2006.07a
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• pp.230-231
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• 2006

In this paper, the RCF(Resistive Companion Form) analysis method is used to analyze small signal stability of power systems including GTO controlled FACTS equipment such as SSSC. To apply the RCF analysis method in power system small signal stability problems, state transition equations of power system equipments and power systems with SSSC are presented. In eigenvalue analysis of power systems by the RCF analysis method, SSSC is modelled into the equivalents voltage source model and PWM switching circuit model. As a result of simulation, the RCF method is very powerful to calculate the oscillation modes exactly after the switching operations, and useful to analyze the small signal stability of power systems with periodic switching device such as SSSC.

• The Transactions of the Korean Institute of Electrical Engineers
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• v.36 no.10
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• pp.695-702
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• 1987

Nowadays as the power systems have been more complicated and have grown to ultra high voltage, it requires a accurate and high speed relaying scheme to improve the reliability and stability of power systems for a harmonious power supplying. For this purpose voltage and current have to be measured at the location of the protective device and the short circuit impedance must be determined. This paper presents the application methods and some results of digital distance relaying scheme which is based upon the theouy of real-time symmetrical components. Usually the symmetrical component have been used to solve the transient systems as well as the steady state systems under unbalanced systems. But, real-time symmetrical component frequently have not been applied to on-line control region of the large power system. We have tried to apply this method to deal with the various type of faults on artificial transmission line. And experimental results demonstrate the validity of the proposed techniques. Therefore, this study is expected that it is contributed to improve the reliability of power supplying, searching for the fault location rapidly and exactly in power system.

• Journal of Institute of Control, Robotics and Systems
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• v.5 no.7
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• pp.868-875
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• 1999

In this paper, digital motor control center using protection relay is developed in order to protect power systems by means of timely fault detection and diagnosis during operation for induction motor which have various load environments and capacities in power systems. Digital motor control center is employed by power supervisory control systems without separate remote terminal unit and transducers adding communicational ability. Also we develope a maximum demand controller to control the load effectively at peak status and a power factor controller to minimize real power losses and improve the power factor. Therefore, when using the developed controller, real time computation is possible by loading DSP in hardware and applying real-time kernel which can convert each algorithm to task module.

• Proceedings of the KIEE Conference
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• 2002.07d
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• pp.2540-2542
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• 2002

In recent years, it is a worldwide trend that many power utilities focus their attention to employ up-to-date communication technology to the automation of their power plants and distribution systems. Automation Systems in Korea was installed using twisted pair cable(TPC), power line carrier(PLC), coaxial cable(CA), wireless network(wireless data, TRS and PCS). Among the communication media only Satellite Communication guarantees the reliable communication in case of emergency such as a flood, a heavy snow and an earthquake. It can integrate two-way satellite systems to existent nationwide SCADA controlling points of electric power transmission & distribution system that enables real time remote monitoring and controlling automatically. This paper presents some of design efforts for the satellite communication network as the media of Automation Systems.

• Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
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• v.29 no.2
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• pp.97-103
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• 2015

This paper introduces two on-going projects for DC high temperature superconducting (HTS) cable systems in South Korea. This study proposes the application of DC HTS cable systems to enhance power transfer limits of a grid-connected offshore wind farm. In order to develop the superconducting DC transmission system model based on HTS power cables, the maximum transfer limits from offshore wind farm are estimated and the system marginal price (SMP) calculated through a Two-Step Power Transfer (TSPT) model based on PV analysis and DC-optimal power flow. The proposed TSPT model will be applied to 2022 KEPCO systems with offshore wind farms.

• Proceedings of the KIEE Conference
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• 1999.11b
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• pp.175-177
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• 1999

This paper presents a prototype of visualization MMI of the Power System Phenomenon, specially synchronous machine dynamics and frequency deviations of power system for KEPCO's Enhanced Power System Simulator(KEPS)[1]. And some visualization designs of the Power System Phenomenons such as voltage stability, transient stability, SSR, Line overflow, and voltage deviations are presented. The prototype MMI has included the animations & 3D graphics presentations for synchronous machine rotor deviations and frequency deviations. So, a user can intuitively acquire the basic concepts of the power system oscillations. Finally, it will be scheduled to development of the various visualization MMI of the power system phenomenons for development and installation of KEPS.

• KIEE International Transactions on Electrophysics and Applications
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• v.3C no.3
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• pp.91-98
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• 2003

The importance of improving the quality of electric power is being strongly raised, owing to an increasing use of sensitive and small-sized electronic devices and systems. The transient over-voltages on low-voltage power distribution systems are induced by direct or indirect lightning return strokes. These can cause damage and/or malfunction of the utility systems for home automation, office automation, factory automation, medical automation, etc. The behaviors of lightning overvoltages transferred through the transformer to the low-voltage distribution systems using a Marx generator were experimentally investigated. Furthermore, the coupling mechanisms of lightning overvoltages transferred to the low-voltage systems were clearly illustrated through a theoretical simulation using a Pspice program. The overvoltages in low-voltage ac power systems are rarely limited by the application of the surge arrester to the primary side of the distribution transformer. A superior surge protection scheme is to install surge protection devices at the service entrance switchboard and/or at the load devices in TN power systems.

• Journal of Institute of Control, Robotics and Systems
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• v.20 no.11
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• pp.1118-1124
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• 2014

This paper proposes a novel controller design scheme for multimachine power systems based on the explorized policy iteration. Power systems have several uncertainties on system dynamics due to the various effects of interconnections between generators. To solve this problem, the proposed method solves the LQR (Linear Quadratic Regulation) problem of isolated subsystems without the knowledge of a system matrix and the interconnection parameters of multimachine power systems. By selecting the proper performance indices, it guarantees the stability and convergence of the LQ optimal control. To implement the proposed scheme, the least squares based online method is also investigated in terms of PE (Persistency of Excitation), interconnection parameters and exploration signals. Finally, the performance and effectiveness of the proposed algorithm are demonstrated by numerical simulations of three-machine power systems with governor controllers.

• ETRI Journal
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• v.33 no.2
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• pp.279-282
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• 2011

Coexistence analysis is extremely important in examining the possibility for spectrum sharing between orthogonal frequency-division multiplexing (OFDM)-based international mobile telecommunications (IMT)-Advanced and other wireless services. In this letter, a new closed form method is derived based on power spectral density analysis in order to analyze the coexistence of OFDM-based IMT-Advanced systems and broadcasting frequency modulation (FM) systems. The proposed method evaluates more exact interference power of IMT-Advanced systems in FM broadcasting systems than the advanced minimum coupling loss (A-MCL) method. Numerical results show that the interference power is 1.3 dB and 3 dB less than that obtained using the A-MCL method at cochannel and adjacent channel, respectively. This reduces the minimum separation distance between the two systems, which eventually saves spectrum resources.

• 한국전산유체공학회:학술대회논문집
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• 2008.08a
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• pp.37.5-37.5
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• 2008