• KIEE International Transactions on Electrophysics and Applications
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• 제4C권3호
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• pp.81-89
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• 2004

Frequency Domain Spectroscopy (FDS) measurements were performed on pressboard samples containing different moisture contents and on insulation system of power transformers. The results were used for evaluating sensitivity of the so-called X - Y model, which is applied for estimating moisture content in transformer insulation using the results of FDS measurements. Based on the observations of this analysis a simplified model, called X model, was introduced in which the presence of spacers in transformer insulation has been neglected. Finally, reliability of the X model was assessed by comparing estimates of moisture contents based on FDS measurements on field installed power transformers with moisture contents obtained from chemical analyses of their oil samples.

• 대한전기학회논문지:전기기기및에너지변환시스템부문B
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• 제49권8호
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• pp.529-535
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• 2000

In this paper, a current control system of a single phase PWM AC/DC converter using a reduced-order Luenberger observer without source voltage sensors is proposed. The sinusoidal input current and unity input power factor are realised based on the estimated source voltage performed by the reduced-order Luenberger observer using actual currents and DC link voltage. The poles of the reduced-order Luenberger observer are placed in the left half plane of s-plane by the pole-placement method in order to acquire the stability of the observer. The magnitude and the phase of the estimated source voltage are used to accomplish the unity power factor. The proposed method is implemented by DSP(Digital Signal Processor). Experimental Results verify that the reduced-order observer estimates the source voltage without the estimation error and the control system accomplishes the unity power factor, and constant DC link voltage.

• Journal of Electrical Engineering and Technology
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• 제5권1호
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• pp.28-35
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• 2010

This paper presents new Adaptive Linear Combination Structure (ADALINE) for tracking/estimating voltage-current phasor and frequency of power system. To estimate the phasors and frequency from sampled data, the algorithm assumes that orthogonal coefficients and speed of angular frequency of power system are unknown parameters. With adequate sampled data, the estimation problem can be considered as a linear weighted least squares (LMS) problem. In addition to determining the phasors (orthogonal coefficients), the procedure estimates the power system frequency. The main algorithm is verified through a computer simulation and data from field. The proposed algorithm is tested with transient and dynamic behaviors during power swing, a step change of frequency upon islanding of small generators and disconnection of load. The algorithm shows a very high accuracy, robustness, fast response time and adaptive performance over a wide range of frequency, from 10 to 2000 Hz.

• 대한전기학회:학술대회논문집
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• 대한전기학회 1992년도 하계학술대회 논문집 A
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• pp.205-210
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• 1992

The power flow calculations are the most important and powerful tools in the various studies of power system engineering. Newton-Raphson method, among the various power flow calculation techniques, is normally used due to its rapidness of numerical convergency. In the conventional Newton-Raphson method, however, there are some unrealistic assumptions, in which all the system power losses are considered to be supplied by the slack bus generator. Introducing the system power loss formula and augmenting the conventional Newton-Raphson power flow method, we can relieve the unrealistic assumption and improve the performance of power flow calculation. In this study, A new approach for handling the losses and augmenting the conventional power flow problem is proposed. The proposed method estimates the increamental changes of active power on each generation bus with respect to the change of total system power losses and the estimated value are used to update the slack bus power. If some studies for more theoritical investigations and verifications are followed, the proposed approach will show some improvement of the conventional method and give lots of contribution to increase the performance of power flow techniques in power systems engineering.

• 자원ㆍ환경경제연구
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• 제22권2호
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• pp.367-391
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• 2013

후쿠시마원자력발전소의 사고를 계기로 원전의 안전대책비용, 사고위험대응비용과 같은 외부비용들의 존재가 부각되고 있다. 이에 본 연구는 원전의 외부비용들 중에서 추가안전대책비용과 사고위험대응비용을 추정하고, 이를 발전원가 및 전기요금에 반영하여 변화정도를 살폈다. 원전의 추가안전대책비용은 70~90%의 이용률에서 0.53원/kWh~0.80원/kWh으로 원전의 발전원가에 큰 영향을 미치지는 않는다. 사고위험대응비용은 원전사고피해규모별, 사고발생빈도별, 이용률별로 0.0025원/kWh~26.4188원/kWh로 추정되었다. 사고위험대응비용을 포함시키면 원전발전원가는 47.58원/kWh~85.92원/kWh가 된다. 2011년을 기준으로 사고위험대응비용을 내부화한 경우의 전기요금의 증가율은 70~90%의 이용률에서 0.001%~10.0563% 로 추정되었다. 본 연구는 원전의 외부비용을 내부화하는 방법으로서 외부비용을 발전원가에 포함하여 전기요금에 반영하였다. 본 연구는 지금까지 우리나라에 논의되지 않았던 원전 외부비용을 내부화하는 방법의 하나가 될 것이다.

• 한국콘텐츠학회논문지
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• 제12권7호
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• pp.11-20
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• 2012

본 논문은 비동기식 프로세서, A8051의 명령어 레벨 소비 전력 모델을 제안한다. 제안된 소비 전력 모델은 명령어 레벨로 프로세서가 소비하는 전력을 예측하지만, 프로그램이 실행되는 동안 비동기식 파이프라인의 동작 특성을 반영한다. 따라서, 제안된 방법은 프로세서 소비 전력 모델의 복잡도와 시뮬레이션 시간의 증가 없이 비동기식 임베디드 프로세서 소비 전력 모델의 정확도를 효과적으로 향상시켰다. 제안된 소비 전력 모델은 A8051의 소비 전력 특성을 반영하여 구현되었고 게이트 레벨의 합성한 결과를 이용한 소비 전력 예측 결과와 비교하여 성능 평가를 수행하였다. 제안된 소비 전력 모델은 게이트 레벨의 소비 전력예측 결과와 비교하여 94%의 정확도를 보였고, 1,600 배 이상 시뮬레이션 시간을 단축하였다.

• 응용통계연구
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• 제24권6호
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• pp.1197-1211
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• 2011

The actual power performance of historical structural change tests are compared under various alternatives. The tests of interest are F, CUSUM, MOSUM, Moving Estimates and empirical distribution function tests with both recursive and ordinary least-squares residuals. Our comparison of the structural tests involves limiting distributions under the hypothesis, the ability to detect the alternative hypotheses under one or double structural change, and smooth change in parameters. Even though no version is uniformly superior to the other, the knowledge about the properties of those tests and connections between these tests can be used in practical structural change tests and in further research on other change tests.

• Korean Journal of Mathematics
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• 제25권1호
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• pp.45-60
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• 2017

This paper focuses on estimation of an non-integral quadratic function (NIQF) and integral quadratic function (IQF) of a random signal in dynamic system described by a linear stochastic differential equation. The quadratic form of an unobservable signal indicates useful information of a signal for control. The optimal (in mean square sense) and suboptimal estimates of NIQF and IQF represent a function of the Kalman estimate and its error covariance. The proposed estimation algorithms have a closed-form estimation procedure. The obtained estimates are studied in detail, including derivation of the exact formulas and differential equations for mean square errors. The results we demonstrate on practical example of a power of signal, and comparison analysis between optimal and suboptimal estimators is presented.

• 제어로봇시스템학회:학술대회논문집
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• 제어로봇시스템학회 1991년도 한국자동제어학술회의논문집(국내학술편); KOEX, Seoul; 22-24 Oct. 1991
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• pp.736-740
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• 1991

EEG(Electroencephalogram) background signals can be represented as the sun of a conventional AR(Autoregressive) process and an innovation process, or a prediction error process. We have seen that conventional estimation techniques. such as least square estimates(LSE) or Gaussian maximum likelihood estimates(MLE-G) are optimal when the innovation process satisfies the Gaussian or presumed distribution. But when the data are contaminated by outliers, or artifacts, these assumptions are not met and conventional estimation techniques can badly fall and be strongly biased. It is known that EEG can be easily affected by artifacts. So we suggest a robust estimation technique which considerably performs well against those artifacts.

• Communications for Statistical Applications and Methods
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• 제9권2호
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• pp.389-399
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• 2002

In order to examine whether the difference between two point estimates of population proportions is statistically significant, data analysts use two techniques. The first is to explore the overlap between two associated confidence intervals. Second method is to test the significance which is introduced at most statistical textbooks under the common assumptions of consistency, asymptotic normality, and asymptotic independence of the estimates. Under the null hypothesis which is two population proportions are equal, the pooled estimator of population proportion is preferred as a point estimator since two independent random samples are considered to be collected from one population. Hence as an alternative method, we could obtain another confidence interval of the difference of the population proportions with using the pooled estimate. We conclude that, among three methods, the overlapped method is under-estimated, and the difference of the population proportions method is over-estimated on the basis of the proposed method.