• 전력전자학회논문지
• /
• 제8권3호
• /
• pp.285-291
• /
• 2003

스위치드 릴럭턴스 전동기는 고출력, 고효율 및 직권전동기 구동특성 등으로 견인구동용으로 주목받고 있다. 그러나 전동기를 4상한 구동하기 위한 발전영역에서 제어는 쉽지 않다. 본 논문은 전류제한법에 의해 안정된 발전제동이 가능한 제어방식을 제안하였다. 전동기 구동시는 기준전류제한방식과 위상각 제어방식으로 속도제어를 행하고, 발전제동모드에서는 상전류가 발산하지 않는 조건을 산정하여서 이 값을 기준전류로 한 전류제한방식을 채택하였다. 시뮬레이션과 실험에 의해 제안한 방식의 타당성을 확인하였다.

• 대한전기학회:학술대회논문집
• /
• 대한전기학회 1992년도 하계학술대회 논문집 A
• /
• pp.135-137
• /
• 1992

A new algorithm for self-tuning digital controller is proposed. The system to be controlled is identified on line in auto-regressive-moving-average(ARMA) form via recursive least mean square method. The control law is obtained from the minimization of an objective function. The proposed objective function is similar to that of Generalized Minimum Variance(GMV) method but modified to lessen the overshoot and to avoid numerical divergence problem. This algorithm is applied to the power system stabilization and the comparison of the proposed method with a conventional power system stabilizer(PSS) is presented.

• Journal of the Korean Statistical Society
• /
• 제25권2호
• /
• pp.289-301
• /
• 1996

This paper suggests a new diagnostic measure for detecting influential observations in two group linear discriminant analysis(LDA). It is developed from an information theoretic point of view using the minimum discrimination information(MDI) methodology. MDI estimator of symmetric divergence by Kullback(l967) is taken as a measure of the power of discrimination in LDA. It is shown that the effect of an observation over the power of discrimination is fully explained by the diagnostic measure. Asymptotic distribution of the proposed measure is derived as a function of independent chi-squared and standard normal variables. By means of the distributions, a couple of methods are suggested for detecting the influential observations in LDA. Performance of the suggested methods are examined through a simulation study.

• 한국소음진동공학회:학술대회논문집
• /
• 한국소음진동공학회 1997년도 춘계학술대회논문집; 경주코오롱호텔; 22-23 May 1997
• /
• pp.452-459
• /
• 1997

For computer aided design and construction of low noisy power plants, indoor and outdoor noise prediction program has been developed. The program utilizes the predefined data of noise sources and building materials and has the faculty to estimate the source level using the empirical formula in case of the measured data not being available. In the noise prediction, the mutual noise propagation between indoor and outdoor sites are considered. The outdoor noise source in the calculation of geometric divergence effects is modelled as the omni-directional finite line or planar source according to the source geometry and the receiving points. Outdoor noise prediction is carried out to consider the diffraction effect due to plant structures as well as the attenuation effect due to atmospheric absorption and soft ground. The results of indoor and outdoor noise prediction for a recently constructed diesel engine power plant show good agreement with the measured.

• Journal of Electrical Engineering and Technology
• /
• 제6권4호
• /
• pp.484-492
• /
• 2011

Power system analyses, which involve the handling of massive data volumes, necessitate the use of effective visualization methods to facilitate analysis and assist the user in obtaining a clear understanding of the present state of the system. This paper introduces an interface that compensates for the limitations of the visualization modules of dynamic security assessment tools, such as PSS/e and TSAT, for power system variables including generator rotor angle and frequency. The compensation is made possible through the automatic provision of dynamic simulation data in visualized and tabular form for better data intuition, thereby considerably reducing the redundant manual operation and time required for data analysis. The interface also determines whether the generators are stable through a generator instability algorithm that scans simulation data and checks for an increase in swing or divergence. The proposed visualization methods are applied to the dynamic simulation results for contingencies in the Korean Electric Power Corporation system, and have been tested by power system researchers to verify the effectiveness of the data visualization interface.

• 응용통계연구
• /
• 제16권2호
• /
• pp.455-467
• /
• 2003

소표본 분할표 자료에서 적합도 검정통계량들의 카이제곱 근사 적용 가능에 대하여 많은 연구가 진행되었다. 소표본에서 세 가지 검정 통계량(피어슨 카이제곱 Χ$^2$, 일반화 가능도비 G$^2$, 그리고 역발산 Ι(2/3) 검정통계량)에 관하여 비교한 Rudas(1986)의 연구를 확장하여, 최근에 제안된 차이측도(BWHD(1/9), BWCS(1/3), NED(4/3) 검정통계량)를 포함시켜 비교 분석하였다. 독립모형의 이차원 분할표, 조건부 독립모형과 한 변수 독립 모형을 따르는 삼차원 분할표에 대한 모의실험을 통하여 생성된 90과 95 백분위수와 이에 대응하는 95% 신뢰구간을 살펴보고 실제 백분위수와 비교하였다. 그 결과 Χ$^2$, Ι(2/3), 그리고 BWHD(1/9) 검정통계량이 유사한 결과를 나타내었고 이 통계량들이 기존에 제안된 검정통계량들보다 적은 표본크기에서도 카이제곱 근사방법에 적용 가능함을 발견하였다.

• 한국광학회지
• /
• 제30권5호
• /
• pp.193-196
• /
• 2019

고출력 레이저 다이오드 광원의 안정적 구동을 위한 방열 관리는 필수적이며, 발열부인 활성층 근처의 열흐름에 있어 병목이 심하므로 그 부분의 열저항을 분석하고 설계에 적용하여 개선하는 것이 매우 중요하다. 띠형 발열구조를 갖는 레이저 다이오드 광원은 열전달층 두께에 따라 열저항이 지수함수적으로 급격하게 증가하다가 점점 선형적으로 포화되므로 열저항을 분석함에 있어서 오차가 큰 어려움이 있으며, 보다 정확한 열저항 모델링이 필요하여 수정된 두께의존성 모델함수를 제안하고 그 정확성을 검증하였다. 또한, 전산모사로 얻어낸 열저항의 변화경향성을 미분하여 열전달-단면적의 변화를 구하여 열병목 부위가 직관적으로 파악되게 하였고, 제안하는 모델함수의 열전달-단면적 결과와도 비교하여 분석모델의 예측 정확성을 부연 확인하였다. 고열전도 보조층을 활용하여 열저항이 개선된 구조에 대하여도 그 열전달-단면적 변화경향과 열저항 개선효과를 높은 정확도로 분석한 결과를 소개한다.

• Journal of Electrical Engineering and Technology
• /
• 제13권1호
• /
• pp.240-249
• /
• 2018

Individual DC voltage balance problem is an inherent issue for cascaded H-bridge (CHB) based converter. When the CHB-based static synchronous compensator (STATCOM) is operating at zero current mode, the software-based individual DC voltage balancing control techniques may not work because of the infinitesimal output current. However, the different power losses of each cell would lead to the individual DC voltages unbalance. The uneven power losses on the local supplied cell-controllers (including the control circuit and drive circuit) would especially cause the divergence of individual DC voltages, due to their characteristic as constant power loads. To solve this problem, this paper proposes an adaptive voltage balancing module which is designed in the cell-controller board with small size and low cost circuits. It is controlled to make the power loss of the cell a constant resistance load, thus the DC voltages are balanced in zero current mode. Field test in a 10kV STATCOM confirms the performance of the proposed method.

• 전력전자학회:학술대회논문집
• /
• 전력전자학회 2004년도 전력전자학술대회 논문집(1)
• /
• pp.186-189
• /
• 2004

Switched reluctance machine has much attention because of high efficiency, high power and DC series torque characteristics with a traction drive. But the motor has to have a regenerative mode when it is adopted in an electric vehicle. A current divergence during the regeneration makes difficulties in the control of SRM. This paper proposes a reference current limitation strategy for a stable regeneration based on simulations and experimental tests. The motor is operated with conventional current limit and switching angle control method in motoring mode. Simulations and experiments are executed to verify proposed method.

• Nuclear Engineering and Technology
• /
• 제48권2호
• /
• pp.434-447
• /
• 2016

The aim of this paper is the study of instability state of boiling water reactors with a method based in largest Lyapunov exponents (LLEs). Detecting the presence of chaos in a dynamical system is an important problem that is solved by measuring the LLE. Lyapunov exponents quantify the exponential divergence of initially close state-space trajectories and estimate the amount of chaos in a system. This method was applied to a set of signals from several nuclear power plant (NPP) reactors under commercial operating conditions that experienced instabilities events, apparently each of a different nature. Laguna Verde and Forsmark NPPs with in-phase instabilities, and Cofrentes NPP with out-of-phases instability. This study presents the results of intrinsic instability in the boiling water reactors of three NPPs. In the analyzed cases the limit cycle was not reached, which implies that the point of equilibrium exerts influence and attraction on system evolution.