• 대한전기학회논문지:전력기술부문A
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• 제49권11호
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• pp.531-535
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• 2000

A method to compute the reactive powers of the added buses by the decoupled UPFC model for the optimal voltage profile is presented, by which the voltage magnitudes of PQ buses can get closer to the reference value(usually one p.u.). The performance index for assessing how much the voltage magnitude is closer to the reference value is defined as the squared sum of the present voltage minus the reference voltage multiplied by the weighting number associated with the relative importance of the buses. Numerical example in a 10-unit 39-bus power system with 2 UPFC's shows that the performance index can be very much reduced by operating many UPFC's with the reactive powers for the optimal voltage profile proposed in this paper.

• 대한감각통합치료학회지
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• 제3권1호
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• pp.49-56
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• 2005

Objective : The purpose of this study was to indicate the foundational data to standardize MVPT-R for Koreans. Method : This study was conducted on 221 children ranging in all preschool age from 4 to 6 years residing in Busan and Kyungsangnam-do. It was performed from January 12, 2004 to April 30, 2004. Result : First, similar to American children, as Korean children grow older, the mean raw score of MVPT-R increased. Second, Korean children's mean raw score was higher than that of American children; 3.51 in 4 age, 1.52 in 4.6 age, 2.93 in 5 age, 1.72 in 5.6 age, 1.84 in 6 age and 0.48 in 6.6 age. Third, the mean of PQ(106.57) in Korean children was higher than that of PQ in American children. Fourth, The raw score in Korean children was higher than the raw score in American children in most of the subjects(excluding visual closure subjects). Conclusion : The visual perception skill of Korean children is higher than that of American children. If we apply MVPT-R developed in U.S to Korean children, it will be difficult for Korean children to achieve the adequate results. Therefore, we must use the standardized MVPT-R for Korean that can minimize the differences between American and Korean children's visual perception skills.

• 한국건설관리학회:학술대회논문집
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• 한국건설관리학회 2007년도 정기학술발표대회 논문집
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• pp.704-709
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• 2007

본 연구는 공동주택 공사를 전문적으로 발주하는 대한주택공사가 가지고 있는 입 ${\cdot}$ 낙찰제도의 문제점 및 개선방안을 제시하고자 실시하였다. 이를 위하여 전자조달시스템을 이용해 2001년부터 2005년 10월 까지 대한주택공사의 입 ${\cdot}$ 낙찰 현황 자료를 조사하였다. 위와 같은 과정을 통해 조사한 내용을 공종별 발주추이와 낙찰률, 최저가 낙찰제와 등급별 대상공사 실태 별로 각각 분류하여 분석을 실시하였다. 상기와 같은 목적과 방법에 따라 진행된 본 연구의 결과를 요약하면 다음과 같다: 1) 통계자료를 통하여 대한주택공사에서 발주한 공사의 현황을 분석한 결과 낙찰률의 하락과 특정등급에 발주물량이 편중되어 있는 것으로 분석되었다. 2) 입 ${\cdot}$ 낙찰제도의 문제점 및 대한주택공사와 용역을 제공하는 업체를 위한 효과적인 개선방안을 제시하자면 다음과 같다. 첫째, 적격심사제도와 최저가 심사제의 보완이 필요하다. 둘째, 낙찰률과 발주물량을 조정하여야 한다. 셋째, PQ제도의개선 및 공종별 유자격자 명부제로의 전환이 필요하다.

• Journal of Electrical Engineering and Technology
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• 제11권2호
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• pp.309-319
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• 2016

This paper presents a new recognition and classification method for power quality (PQ) disturbances on the basis of pattern linguistic values. This method solves the difficulty of recognizing disturbances rapidly and accurately by using fuzzy logic. This method uses classification disturbance patterns to define the linguistic values of fuzzy input variables and used the input variables of corresponding disturbance pattern to set membership functions. This method also sets the fuzzy rules by analyzing the distribution regularities of the input variable values. One characteristic of this method is that the linguistic values of fuzzy input variables and the setting of membership functions are not only related to the input variables but also to the character of classification disturbance and the classification results. Furthermore, the number of fuzzy rules is equal to the number of disturbance patterns. By using this method for disturbance classification, the membership function and design of fuzzy rules are directly related to the objective of classification, thus effectively reducing the complexity of the design process and yielding accurate classification results. The classification results of the simulation and measured data verify the feasibility and effectiveness of this method.

• 전기학회논문지
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• 제58권5호
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• pp.936-943
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• 2009

Dynamic voltage restorer(DVR) is now more preferable enhancement than other power quality enhancement in industry to reduce the impact of voltage faults, especially voltage sags to sensitive loads. The main controllers for DVR consists of PLL(phase locked loop), compensation voltage calculator and voltage compensator. PLL detects the voltage faults and phase. Compensation voltage calculator calculates the reference voltage from the source voltage and phase. With calculated compensation voltage from PLL, voltage compensator restores the source voltage. If PLL detect ideal phase, compensation voltage calculator calculates ideal compensation voltage. Therefore, PLL for DVR is very important. This paper proposes the new method of PLL in DVR. First, the power circuit of DVR system is analyzed in order to compensate the voltage sags. Based on the analysis, new PLL for improving transient response of DVR is proposed. The proposed method uses band rejection filter(BRF) at q-axis in synchronous flame. In order to calculate compensation voltage in commercial instruments, the PQR theory is used. Proposed PLL method is demonstrated through simulation using Matlab-Simulink and experiment, and by checking load voltage, confirms operation of the DVR

• 한국안전학회지
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• 제6권3호
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• pp.50-55
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• 1991

It is well known that mechanisms of fracture and crack growth depend upon material characteristics such as fracture toughness, environmental condition, cracd geometry and mechanical properties. It seems to be very important to investihate the effects of the above factors on the behavior of structural components which contain flaws for the detailed evaluation of their intehrity. In this experimental research, fracture behaviors of moterials were investigated by using Acoustic Emission(AE) technique. The fracturing processes of materials were estimated through both the tension specimens. For the detrmlnatlon of yied strength or fracture toughness, the critical applied load at the crack initiation and propagation is thought to be very important. The critical applied load(PQ) was determined through AE signal. The source of AE signal was estimated by fractography analysis. These experimental results may contribute to the safety analyses and the evaluation of strength of structures.

• 전력전자학회:학술대회논문집
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• 전력전자학회 2004년도 전력전자학술대회 논문집(2)
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• pp.858-861
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• 2004

This paper presents a wavelet-based neural network technology for the detection and classification of the various types of power quality disturbances. Power quality phenomena are short-time problems and of many varieties. Particularly, the transients happen during very short durations to the nano- and microsecond. Thus, a method for detecting and classifying transient signals at the same time and in an automatic combines the properties of the wavelet transform and the advantages of neural networks. Especially, the additional feature extraction to improve the recognition rate is considered. The configuration of the hardware of WN (PQ-DAS) and some case studies are described.

• 대한전기학회:학술대회논문집
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• 대한전기학회 2000년도 하계학술대회 논문집 A
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• pp.265-267
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• 2000

A method to compute the reactive powers of the added buses by the decoupled UPFC model for the optimal voltage profile is presented, by which the voltage magnitudes of PQ buses can get closer to the reference value(usually one p.u.). The performance index for assessing how much the voltage magnitude is closer to the reference value is defined as the squared sum of the present voltage minus the reference voltage multiplied by the weighting number associated with the relative importance of the buses. Numerical example in a 10-unit 39-bus power system with 2 UPFC's shows that the performance index can be very much reduced by operating multi UPFC's with the reactive powers for the optimal voltage profile proposed in this paper.

• 대한전기학회논문지:전력기술부문A
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• 제52권10호
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• pp.577-583
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• 2003

The control method of Thyristor Controlled Reactor(TCR) is described in this paper for compensating the poor power factor, unbalanced and/or nonlinear load. Also, auxiliary controller such as DC current and power-factor controller is described. The reference current of TCR is calculated from the active and reactive Current components for each of the positive and negative sequence components in the load Currents. This reactive power control technique was verified by simulation program and will be used in 5Mvar TCR system, which will be installed next year at hot rolled mill at POSCO, located in Kwang-Yang.

• 대한전기학회:학술대회논문집
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• 대한전기학회 2003년도 추계학술대회 논문집 전력기술부문
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• pp.54-56
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• 2003

With the advancement of superconductor materials, especially in HTC YBCO(Gen II), the feasibility of SMES in power systems become much higher than previous days application[1]. Also, with the de-regulation of electricity market, it is indispensable to have a proper estimation of power quality index and power quality cost calcluation mechanism to stabilize highly industrialized society and to vitalize the investment for electric power system. This paper suggests a comprehensive algorithm[2] to determine the policy of SMES investment with the PQ Indices[3] based on aggregated load CBEMA curve reflecting the voltage characteristics such as volatge sags and interruptions which make electric load in unstable operation.