• The Transactions of the Korean Institute of Electrical Engineers
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• v.41 no.8
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• pp.841-849
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• 1992

In power system operation, the stability of synchronous machine has been recognized one of the most important things. AESOPS program developed by EPRI in U.S.A. is a frequency domain analysis program in power system stability and it computes the electro-mechanical oscillation mode. This paper presents how to analyze the power system small signal stability problem efficiently by uusing the AESOPS program and analyze the various factors affecting the damping characteristics of these oscillations in KEPCO power system of 1986 with pumped-storage plant. To reduce the computing time and efforts, selecting the poorly-damped oscillation mode and clustering technique have been used. The characteristics of load, the amount of power flow on the transmission line and the gain of exciter have a significant effects on the damping of the system while the governing system has only a minor one. With the Power System Stabilizers, the stability of the power system has been improved.

• Proceedings of the KIEE Conference
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• 2011.07a
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• pp.224-225
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• 2011

전력진동(Power Oscillation)은 전력이 0.05 Hz ~ 3.0 Hz의 저주파로 진동하는 현상으로서 계통고장 등의 원인으로 의해 취약한 송전선로에서 발생된다. 전력진동의 종류에는 inter-area mode, intra-area mode, local mode 등이 있는데, 국내 전력계통에서는 향후 영동권 원자력단지와 충남 서해안 화력단지 간을 연결하는 초고압 송전선로에서 intra-area mode의 전력진동이 발생할 가능성이 있다. TCSC를 적용하여 전력진동 제동효과를 얻을 수 있다. 본 논문에서 국내 전력계통에 TCSC를 설치함으로써 전력진동이 효과적으로 감소됨을 보인다. simulation 결과, 전력진동이 5% 수준으로 대폭 감소됨을 알 수 있다.

• KIEE International Transactions on Power Engineering
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• v.4A no.4
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• pp.178-191
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• 2004

This paper presents a new approach to HVDC system control for damping subsynchronous oscillation (SSO) involving HVDC converters and turbine generator shaft systems. This requires a novel eigenvalue analysis (NEA) program, derivation of HVDC system modeling considering steady-state conditions and dynamic conditions in the combined AC/DC system, and an appropriate control scheme. The method suggested makes possible the design of a subsynchronous oscillation damping controller (SODC) to provide positive damping torque for the range of torsional modes in combined AC/DC systems. There are three steps involved in the design of a SODC； first the worst torsional mode is determined using the NEA program, next the SODC parameters are designed for the range of that torsional mode, and then finally an off-line simultaneous time domain program such as PSCAD/EMTDC is used to verify the parameters of the SODC. The suggested SODC design method is applied to two AC/DC systems, and its practicality is verified using the PSCAD/EMTDC simulation program.

• Journal of the Optical Society of Korea
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• v.4 no.1
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• pp.11-13
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• 2000

We experimentally measured the cold cavity loss of a mode-locked erbium-doped fiber ring laser in situ by using the relaxation oscillation frequency method. The relaxation oscillation frequency is measured for various pumping powers and the data is fitted by the least squares method with a theoretical curve of parameters including the cavity loss. We obtained a cavity loss of 15.3$\pm$0.5 dB which was found to agree with the results of direct transmission loss measurements.

• ETRI Journal
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• v.24 no.3
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• pp.255-258
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• 2002

We created a new design for an Nd-doped clad-pumped silica fiber laser to enhance the pump absorption and lasing efficiency for a butt-coupled, end-pumped scheme. Two concatenated adiabatic tapers formed within the laser cavity simultaneously removed higher order modes and were spliced to conventional single mode fibers. We theoretically analyzed mode propagation along the composite cavity and experimentally achieved continuous wave oscillation in the $LP_{01}$ mode at $1.06\;{\mu}m$ and a laser output power of over 820 mW with a slope efficiency of 27%.

• The Transactions of the Korean Institute of Electrical Engineers P
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• v.58 no.4
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• pp.588-591
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• 2009

We had experimental studies of microwave output generator. We experimented with a corrugate-shped K-band slow wave guide in the backward wave oscillator. It generated output 표 interaction between electron beam's generation and magnetic field. We estimated oscillation frequency at 24GHz by changing propagation velocity and group velocity. We identified movement by second harmonic of Cherencov interaction and slow cyclotron mode. In our study we achieved oscillation stabilization, generation of long pulse, improvement of oscillation efficiency and output.

• Proceedings of the Korea Water Resources Association Conference
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• 2011.05a
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• pp.91-91
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• 2011

In the present study, the proposed EMD and NSOR models has been applied in hydrology and climate sciences. Here, we present those applications as the following: (1) to extend future scenarios of Global Surface Temperature Anomaly including long-term oscillation component; (2) to extend the future evolution of the Eastern Canada winter precipitation; (3) to apply EMD in detecting climate change.

• Korean Journal of Optics and Photonics
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• v.23 no.2
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• pp.77-86
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• 2012

The connection between the continuousness of Rabi oscillation and the discontinuity of quantum jumps has long remained one of the conceptual difficulties since the discovery of the quantum physical paradigm. In this study, however, we demonstrate that the behavior of the atom-field composite system gradually changes from the continuous Rabi interaction to the discontinuous quantum jumps as the atom-field coupling strength is reduced. The reduction occurs through enlarging the quantization volume of the mode so that the mode approaches one of the infinitely many modes of the thermal background.

• Proceedings of the Korean Society of Propulsion Engineers Conference
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• 2010.11a
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• pp.563-564
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• 2010

A Numerical analysis of preventing pressure oscillation for the supersonic inlet of IRR at the boosting mode was conducted in this study. To reduce the fluctuation of pressure, the supersonic inlet was equipped with annular slit. By decreasing the entrained air mass, the amplitude of fluctuation and maximum pressure at the inlet were decreased while the frequency was increased. In case, the optimal trade-off value is obtained between frequency and amplitude, it is expected that the pressure oscillation declining method using the slit will be helpful in various boosting and transition mode problem for IRR.

• The Transactions of The Korean Institute of Electrical Engineers
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• v.63 no.1
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• pp.1-9
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• 2014

The parameters of electromechanical modes offer considerable insight into the dynamic stability properties of a power system. This paper describes an initial result for extraction of dynamic parameters from synchrophasor measurements collected on the KEPCO system. Dominant modes of the system are estimated by oscillation detecting program in K-WAMS. The critical wide-area modes of KEPCO system have frequencies in the 0.4 to 0.7Hz range. And the local mode causing the low frequency oscillation of generators located on the west coast area has in the frequency 0.97 and 1.25 Hz, respectively. This results can serve as a reference in the future for reliable system operation in KEPCO system.