• Journal of Electrical Engineering and Technology
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• 제9권4호
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• pp.1217-1228
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• 2014

A method for faulted line detection of four parallel lines on the same tower is presented, based on four-summing and double-differential sequences of one terminal current. Four-summing and double-differential sequences of fault current can be calculated using a certain transformation matrix for parameter decoupling of four parallel transmission lines. According to fault boundary conditions, the amplitude and phase characteristics of four-summing and double-differential sequences of fault current is studied under conditions of different types of fault. Through the analysis of the relationship of terminal current and fault current, a novel methodology for fault line detection of four parallel transmission line on the same tower is put forward, which can pick out the fault lines no matter the fault occurs in single line or cross double lines. Simulation results validate that the methodology is correct and reliable under conditions of different load currents, transient resistances and fault locations.

• 대한전기학회:학술대회논문집
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• 대한전기학회 1991년도 하계학술대회 논문집
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• pp.508-511
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• 1991

In this paper, we have analyzed the transient and steady state characteristics of buck type DC-DC converter using the sliding mode control method based upon VSS. This control method provides the easier analysis tool due to the time domain analysis and the acquirement of desired transient characteristics if the slope of the switching line is properly selected, and guarantees the robustness against parameter uncertainties and load disturbances. Also, it can achieve direct nonlinear control without linearizing approximation of state space averaging method. PSPICE simulation results are then presented verifying these concepts.

• 조명전기설비학회논문지
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• 제25권10호
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• pp.94-101
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• 2011

The proper installation of SPD and the evaluation of the SPD protection distance are basic steps for the effective protection measures of apparatus against surges within a structure. A novel method for installing SPD on the conventional distribution board without any modification was proposed and it's effectiveness was evaluated by experiments. Also, the transient overvoltage occurred across the power line from the SPD to the load was simulated with EMTP software to see how different the protection distances affecting the magnitude of the transient overvoltage. As evaluated, the effective protection method of apparatus against surges, coordinated SPD protection system is suggested as a proper measure to protect within the apartment.

• 대한전기학회:학술대회논문집
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• 대한전기학회 2005년도 제36회 하계학술대회 논문집 A
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• pp.136-139
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• 2005

On-line dynamic security assessment is becoming more and more important for the stable operation of power systems as load level increases. The necessity is getting apparent under Electricity Market environments due to more various operating conditions. Fast transient stability analysis tool is required for contingency selection. The TEF(Transient Energy Function) method is a good candidate for this purpose. The clustering of critical generators is crucial for the precise and fast calculation of energy margin. In this paper, we propose a new method for fast decision of mode of instability by using stability indices. Case study shows very promising results.

• Structural Engineering and Mechanics
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• 제12권3호
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• pp.267-281
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• 2001

Transient and quasi-steady-state vertical vibrations of a multi-span beam steel bridge located on a single-track railway line are considered, induced by a superfast passenger train, moving at speed 120-360 km/h. Matrix dynamic equations of motion of a simplified model of the system are formulated partly in the implicit form. A recurrent-iterative algorithm for solving these equations is presented. Excessive vibrations of the system in the resonant zones are reduced effectively with passive dynamic absorbers, tuned to the first mode of a single bridge span. The dynamic analysis has been performed for a series of types of bridges with span lengths of 10 to 30 m, and with parameters closed to multi-span beam railway bridges erected in the second half of the $20^{th}$ century.

• 전력전자학회논문지
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• 제4권3호
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• pp.268-274
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• 1999

일반적으로 컨버터 장치로서 사용되고 있는 전력용 반도체 소자인 SCR이나 diode를 사용할 때 역률과 고조파의 문제를 야기 시킨다. 이러한 문제점을 해결하기 위해 자기소호형 소자인 IGBT등을 사용하여 입력측 선전류를 입력 전원전압과 동상인 정현파 전류로 유지함으로써 역률과 고조파에 대한 문제를 해결 하였다. 본 논문에서는 컨버터 출력측 직류전압 제어기에 부하전류 전향보상기(feedforward compensator)를 부가하여 출력측에 다이오드 정류기가 부가된 단상 전압형 인버터를 부하로 사용하여 보상기 부가에 따른 과도상태특성을 개선하였으며 전압형 PWM 컨버터 제어에 의한 특성을 시뮬레이션 및 실험 결과를 통하여 확인 하였다.

• 대한기계학회:학술대회논문집
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• 대한기계학회 2007년도 춘계학술대회B
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• pp.2130-2135
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• 2007

Operating characteristics of a loop heat pipe (LHP) having a bypass line was investigated experimentally. The LHP had a sintered metal wick as a capillary structure and methanol as a working fluid. The sintered metal wick was made of stainless steel of which the average pore size was 5 ${\mu}m$and porosity of 47%. A bypass line of a small diameter was attached between the vapor escape passage and the liquid reservoir. The dimension of the flat evaporator was $50(L){\times}40(W){\times}30(H)$ mm and that of the condenser was $50(L){\times}40(W){\times}11(H)$ mm. Wall and pipe material of the LHP was stainless steel and heating area was 35(W) mm${\times}$35(L) mm. The inner diameters of vapor and liquid transport lines were 4.0 mm and 2.0 mm, and the lengths of the two lines were both 0.5 m. The LHP was tested for three different tilt angles of horizontal, favorite tilt, and adverse tilt. The thermal load range was up to 290 W at the condenser above evaporation position. Furthermore, the effect of a bypass line on the start-up transient as well as steady-state operation was presented and discussed.

• 대한전기학회:학술대회논문집
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• 대한전기학회 1997년도 하계학술대회 논문집 D
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• pp.844-847
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• 1997

Countermeasure for instability due to sudden changes like electric short circuit, line switching, generation/load dropping etc. in power systems have been sought in terms of intentional or controlled network changes such as series/shunt compensation and generation/load rejection etc. This paper presents the comparison of stability improving effects by series and shunt compensation for the first swing step out phenomena of a large capacity generating station.

• 대한전기학회:학술대회논문집
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• 대한전기학회 1987년도 전기.전자공학 학술대회 논문집(I)
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• pp.737-741
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• 1987

The induction motor is represented by nonlinear equations whose parameters are changing with respect to the slip-frequency, temperature, etc. The slip-frequency is effected by unknown load which is difficult to estimate on-line. Astable vector controller is designed with direct MRAC to improve the quality of the transient response. The unknown load is considered in this speed controller design, and tested by simulation. Also a flux controller is designed and tested to reduce the audible noise in this paper.

• 대한전기학회:학술대회논문집
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• 대한전기학회 2003년도 춘계학술대회 논문집 전기기기 및 에너지변환시스템부문
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• pp.270-272
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• 2003

Switching power supplies are widely used in many industrial fields. Power factor correction(PFC) circuits have tendency to be applied in new power supply designs. The input active power factor correction(APFC) circuits can be implemented using either the two-stage approach or the single-stage approach. The single-stage PFC circuit has advantage to reduce the number of components by eliminating a need for the PFC switch and control circuit. However, unlike in the two-stage approach, the do voltage on the energy storage capacitor in a single-stage PFC circuit is not well regulated. As a result. in universal line application($90{\sim}265Vac$), the storage capacitor voltage varies with the load and line variation. In this paper, the performance of output voltage regulation and transient response are clarified here. The validity of designed boost PFC circuit is confirmed by MATLAB simulation and experimental results of 2 [kW] prototype converter.