• Smart Structures and Systems
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• 제8권3호
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• pp.253-274
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• 2011

In this paper, the harmonic displacement response of a damaged square plate with all-over part-through damage parallel to one edge is utilized as the input signal function in wavelet analysis. The method requires the properties of the damaged plate, i.e., no information about the original undamaged structure is required. The location of damage is identified by sudden changes in the spatial variation of transformed response. The incurred damage causes a change in the stiffness or mass of the plate. This causes a localized singularity which can be identified by a wavelet analysis of the displacement response. In this study via numerical examples shown by using harmonic response is more versatile and effective compared with the static deflection response, specially in the presence of noise. In the light of the obtained results, suggestions for future work are presented and discussed.

• 한국철도학회:학술대회논문집
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• 한국철도학회 2005년도 춘계학술대회 논문집
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• pp.782-787
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• 2005

Magnitude of generated harmonic currents along with the operation of AC traction has nonlinear characteristics, and generated harmonic currents for high speed traction are more and more in high speed railroad(HSR) systems, especially. This paper presents probabilistic approximation method for the harmonic currents analysis about the operating speed of AC traction. To use probabilistic method for HSR system, probability density function(PDF) for collected operating speed based measure data is calculated. Mean and variance of harmonic currents of single traction are obtained based on the operating speed PDF and electrical traction model. The results of Monte Carlo Simulation(MCS) are in well accordance with the experimental and analytic methods. The harmonics of different number of trainloads are systematically investigated. It is assessed by the total demand distortion(TDD) for the HSR system.

• 대한전자공학회논문지
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• 제17권2호
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• pp.10-14
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• 1980

본 논문에서는 DH-laser diode의 threshold current를 계산하기 위하여 2차고조파 왜곡 (se cond harmonic distortion)에 대해 Rate 방정식 (Rate-equation)을 동적상태와 정적상태 방정식으로 연릴하여 계산하였다. 특히 고조파 왜곡 ( )을 계산하는데 바이어스 전류 에 대하여 변조 전류 을 변조계수 m으로 놓고 (Jm=mJo)계산하여 주입전류 J가 Jth에서 2차 고조파 왜곡이 최대치를 가짐을 보여 ,이제까지 알려진 Jth조사 방법보다 간편하고 정확하게 조사할 수 있음을 제시하였다.

• 대한전기학회:학술대회논문집
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• 대한전기학회 2008년도 제39회 하계학술대회
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• pp.754-755
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• 2008

This paper presents a method for reducing the Total Harmonic Distortion(THD) of line-line back_EMF of the IPMSM with distributed winding under the no-load condition. Firstly, the specific harmonic components of line-line back EMF are reduced considering with winding factor. Secondly, THD of line-line back EMF is minimized according to change of pole angle using by Space harmonic Analysis. Finally, the optimal design for minimizing the THD is conducted using response surface methodology with finite element analysis. The validity of the design method dealt with in this paper is demonstrated by comparison between the THD of optimal model and initial model.

• 대한전기학회논문지:전기기기및에너지변환시스템부문B
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• 제51권3호
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• pp.99-106
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• 2002

This study presents an approach to model the Electric Railway System with the common grounding based on the 8-port network model and to analyse traction power feeding system focused on the amplification of harmonic current. The entire system can be easily modeled by the combination of 8-port representation of each component in parallel and/or series. Through the research, 8-port network model which can be effectively applied to harmonic analysis is derived.

• 조명전기설비학회논문지
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• 제26권5호
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• pp.48-57
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• 2012

This paper analyzes the characteristic of gird connected photovoltaic power generation system which is available to connect the utility. Renewable energy photovoltaic power system has been linked to the system to analyze the impact of photovoltaic system. It is measured that power data for the Grid connected photovoltaic power plant with instantaneous measuring and 3-sec measuring for 7 days. Harmonic field measurements have shown that the harmonic contents of a waveform varies with time. A cumulative probability approach is the most commonly used method to solve time varying harmonics. So, it is used 50[%] cumulative probability approach. This paper provides an in depth analysis on power quality field measurement of the Grid connected photovoltaic power plant.

• 대한전기학회논문지:전력기술부문A
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• 제54권4호
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• pp.172-176
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• 2005

Power system restoration following a massive or complete blackout starts with energizing of primary restorative transmission lines. During this primary restoration, inexpected overvoltage may happen due to nonlinear interaction between the unloaded transformer and the transmission system. This is known as the harmonic resonance phenomenon that may cause burning out of transformer or other devices. By now the harmonic resonance is reported in the extra high voltage system. This paper reports the detection of the resonance in Korean power system. Basic analysis and simulation of the harmonic overvoltage is presented using EMTDC.

• 대한전기학회:학술대회논문집
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• 대한전기학회 2003년도 하계학술대회 논문집 B
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• pp.1276-1278
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• 2003

The magnified current harmonics usually brings about various problems. That is, the current harmonics makes interference in the adjacent lines of communications and the railway signalling system. Furthermore, in case it flows on the side of power system, not only overheating and vibration at the power capacitors but also wrong operation at the protective devices can occur. Therefore, the exact assessment of the harmonic current flow must be undertaken at design and planning stage for the electric traction systems. From these point of view, this study presents the harmonic analysis and the modelling of traction power feeding system focused on the amplification of harmonic current.

• 대한전기학회:학술대회논문집
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• 대한전기학회 2003년도 추계학술대회 논문집 전력기술부문
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• pp.31-33
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• 2003

Power system restoration following a partial or complete blackout starts with energizing of primary transmission lines. Because system changed rapidly during early restoration process, transformer energization and load pickup is executed to maintain the power system stability. However unexpected problem such as harmonic overvoltage may be arisen during energizing transformer. The reason of harmonic overvoltage is known as transformer saturation and magnetizing in-rush current and so on, but it is difficult to estimate the condition of occurrence. This paper describes the analysis of the harmonic overvoltage while unloaded transformer is energized using PSCAD/EMTDC.

• 한국소음진동공학회:학술대회논문집
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• 한국소음진동공학회 2004년도 추계학술대회논문집
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• pp.1077-1082
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• 2004

It is well known that the pipe will be unstable if the fluid velocity is higher than critical velocity. But even if the velocity of the fluid below the critical velocity, resonance will be caused by pulsation of the fluid. So, many people has studied about the piping system vibration due to a fluid pulsation. But almost guess that fluid has only one hamonic pulsation. Actually, like this case is rare quite. So, in this paper, we consider the vibration analysis of a pipe conveying fluid with several harmonic pulsations and compare the result which considers one hamonic pulsation with the result which considers several harmonic pulsations. And we verify the result in time domain again.