• 대한전기학회논문지:전력기술부문A
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• 제48권6호
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• pp.704-711
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• 1999

This paper presents a design of fuzzy power system stabilizer (FPSS) using adaptive evolutionary computation (AEC). We have proposed an adaptive evolutionary algorithm which uses a genetic algorithm (GA) and an evolution strategy (ES) in an adaptive manner in order to take merits of two different evolutionary computations. FPSS shows better control performances than conventional power system stabilizer (CPSS) in three-phase fault with heavy load which is used when tuning FPSS. To show the robustness of the proposed FPSS, it is appliedto damp the low frequency oscillations caused by disturbances such as three-phase fault with normal and light load, the angle deviation of generator with normal and light load and the angle deviation of generator with heavy load. Proposed FPSS shows better robustness than CPSS.

• 대한전기학회:학술대회논문집
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• 대한전기학회 1998년도 추계학술대회 논문집 학회본부A
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• pp.326-328
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• 1998

This paper presents an optimal fuzzy power system stabilizer to damp out low frequency oscillation. The fuzzy logic controllers has been applied to a power system stabilizing controllers. But the design of a fuzzy logic power system stabilizer relies on empirical and heuristic knowledge of human experts as well as many trial-and-errors in general. This paper presents the optimal design method of the fuzzy logic stabilizer using the genetic algorithm, which is the optimization method based on the mechanics of natural selection and natural genetics. The proposed method tunes the parameters of the fuzzy logic stabilizer in order to minimize the consuming time during the design process. In this paper, the proposed method tunes the shape of membership function of the fuzzy variables. The proposed system is applied to the one-machine infinite-bus model of a power system. Through the case study, the efficiency of the fuzzy stabilizing controller tuned by genetic algorithm is verified.

• 전기학회논문지
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• 제57권10호
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• pp.1708-1712
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• 2008

This paper describes a linear matrix inequality (LMI) approach to the design of robust low-order power system stabilizers (PSSs), which are used to damp out local-mode oscillations of synchronous generators. The performance of a PSS is expressed as the location of the closed-loop poles, and a single fixed-gain pole-placement controller is synthesized for a wide range of operating conditions. The synthesis results in simultaneous regional pole-placement stabilization. and is formulated as an LMI feasibility problem with a rank condition. A penalty method is applied to solve the rank-constrained LMI problem. Numerical experiments with a single-machine connected to an infinite bus system were performed to demonstrate the proposed method.

• 한국도로학회논문집
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• 제9권4호
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• pp.171-184
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• 2007

화학적 첨가제를 이용한 안정처리는 지반의 강도증가 및 변형발생을 제어하기 위한 방법으로 깊은 심도까지 광범위하게 적용되어 지고 있다. 화학적 안정처리의 기본목적은 지반의 강도증가, 압축성 감소, 팽창특성 등을 개선하여 지반의 내구성을 증가시키는 것이며, 최근 들어 환경친화적이며 혼합체의 특성 및 혼합속도를 효율적으로 개선한 다양한 형태의 진보적인 시멘트 혼화재가 개발되고 있다. 본 연구에서는 농어촌도로(농도)의 효율적인 포장공법 개발을 위하여 시멘트혼화재를 활용하는 방안을 연구하였으며, 혼화재 종류 및 배합비에 따른 다짐시험, 일축압축강도시험, 동결융해시험 및 휨강도시험을 실시하였다. 본 연구결과에 따르면, 실트질 원지반토가 점토지반에 비해 강도증가 및 동결융해특성이 우수하며, 액상형 시멘트 혼화재가 분말형태 보다 효과적인 것으로 나타났다. 또한 저배합에서도 고강도의 품질을 발휘하여 농어촌도로 표층 내구성 저하를 개선할 수 있을 것으로 판단된다.

• 대한전기학회논문지:시스템및제어부문D
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• 제55권1호
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• pp.1-13
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• 2006

This paper presents the problems of designing low-order controller for a linear time-invariant(LTI) system in parameter space, wherein both transient response requirements and stability shall be considered in the same space. For a LTI system, we, (1) develop a method determining the existence of low-order stabilizers of the first-order and PID structures, (2) develop an algorithm of finding such a stabilizing region. (3) Both procedures are carried out by means of a parametric approach in the same frame work. This leads to easily obtain a subset of controller gains from the stabilizing set, that meet good time response requirements. It is illustrated by examples.

• Journal of Electrical Engineering and information Science
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• 제2권3호
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• pp.88-94
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• 1997

This paper presents the sliding mode observer-model following (SMO-MF) power system stabilizer(PSS) for unmeasurable state variables. This SMO-MF PSS is obtained by combining the sliding mode-model following (SM-MF) including closed-loop feedback(CLF) with the full-order observer(FOO). The control input of the proposed MO-MF PSS is derived by Lyapunov's second method to determine a control input that keeps the system stable for unmeasurable plant state variables. Simulation results show that the proposed SMO-MF PSS including CLF is able to reduce the low frequency oscillation and to achieve asymptotic tracking error between the reference mode state and the estimated plant state at different initial conditions.

• Journal of Electrical Engineering and information Science
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• 제2권4호
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• pp.53-58
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• 1997

In this paper, the power system stabilizer(PSS) using the sliding mode observer-model following(SMO-MF) with closed-loop feedback (CLF) for single machine system is extended to multimachine system. This a multimachine SMO-MF PSS for unmeasureable plant state variable is obtained by combining the sliding mode-model following(SM-MF) including closed-loop feedback(CLF) with the full-order observer(FOO). And the estimated control input for unmeasurable plant sate variables is derived by Lyapunov's second method to determine a control input that keeps the system stable. Time domain simulation results for the torque angle and for the angular velocity show that the proposed multimachine SMO-MF PSS including CLF for unmeasurable plant sate variables is able to damp out the low frequency oscillation and to achieve asymptotic tracking error between the reference model state at different initial conditions and at step input.

• 한국응용과학기술학회지
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• 제35권3호
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• pp.985-1001
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• 2018

W/O 에멀젼; 안정성; 유화제본 연구에서는 일반적으로 O/W 에멀젼에 비해 안정화가 어려운 W/O 에멀젼, 특히 유동성이 높은 저점도 W/O 에멀젼의 안정성 증진을 위하여 유화제, 전해질, 유화 안정화제, 겔화제 등을 적용한 다양한 실험을 수행하여 보았다. 그 결과 이번 실험에서는 Polyglyceryl-4 diisostearate/polyhydroxystearate/sebacate를 주 유화제로 하면서 PEG-30 dipolyhydroxystearate와 Cetyl PEG/PPG-10/1 dimethicone을 보조 유화제로 하는 유화 체계에, 전해질로 Sodium chloride를 0.5 %, 유화 안정화제로 Distearyldimonium chloride를 1 %, 유상 겔화제로 Glyceryl behenate/eicosadioate를 0.5 % 적용한 유화 입자도 작고 조밀하며 점도도 2,000 cps 이하로 일정하게 유지되는 안정한 저점도 W/O 에멀젼을 제조할 수가 있었다. 또한 상기와 같은 에멀젼 베이스에 무기 자외선 차단성분의 적용 실험을 통하여 안정성이 우수한 저점도 플루이드형 자외선 차단제품의 개발 가능성도 긍정적으로 검토할 수가 있었다.

• 대한전기학회논문지:전력기술부문A
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• 제50권7호
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• pp.324-332
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• 2001

In this paper, it is suggested that the selection method of parameter of Power System Stabilizer(PSS) with robustness in low frequency oscillation for Static VAR Compensator(SVC) using a Real Variable Elitism Genetic Algorithm(RVEGA). A SVC, one of the Flexible AC Transmission System(FACTS), constructed by a fixed capacitor(FC) and a thyristor controlled reactor(TCR), is designed and implemented to improve the damping of a synchronous generator, as well as controlling the system voltage. The proposed PSS parameters are optimized using RVEGA in order to maintain optimal operation of generator under the various operating conditions. To decrease the computational time, real variable string is adopted. To verify the robustness of the proposed method, we considered the dynamic response of generator speed deviation and generator terminal voltage by applying a power fluctuation and three-phase fault at heavy load, normal load and light load. Thus, we prove the usefulness of proposed method to improve the stability of single machine-infinite bus with SVC system.

• 한국철도학회:학술대회논문집
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• 한국철도학회 2000년도 춘계학술대회 논문집
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• pp.479-486
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• 2000

최근에 철도분야에서는 철도차단시간을 최소화하는 상태에서 현장케도의 동적성능을 향상시키고자하는 노력이 지속되어 왔다. 본 연구에서는 철도케도의 거동 및 동특성규명을 위해 운행선 궤도를 대상으로 도상안정제 살포 전ㆍ후 열차주행시험, 횡저항력시험 및 정ㆍ동적해석을 실시하였다. 이들 결과를 토대로 도상안정제의 효과를 확인하였으며, 아울러 궤도상태를 나타내는 궤도계수 산출을 위한 도표와 도상궤도 구성요소의 진동 및 하부구조로 전달되는 분포력 저감방안을 제시하였다. 본 연구에서 제시되는 결과는 향후 궤도상태판정 및 유지관리를 위한 기초자료로서 널리 이용될 수 있을 것으로 판단되었다.