• 한국농공학회논문집
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• 제50권2호
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• pp.19-26
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• 2008

This study has been carried out to investigate the dynamic characteristics of RC slabs. For this purpose, the 20-node solid element has been used to discretize the RC slabs into two parts of concrete and rebar. The material non-linearity considering elasto-visco plastic model and the smeared crack model have been adopted in the finite element formulation. The applied load can handle step load, load intensity of harmonic load, area of distributed load and frequency. The frequency of harmonic load has an significant effect on dynamic behaviour in terms of displacement. As the frequency is increased, the effect of load amplitude is more serious. Especially, if the frequency of harmonic load exceeds 30 Hz, it is noted that the displacement by harmonic load is greater than that by step load. In case of harmonic load, the damping effect shows no certain tendency with respect to frequency of load. In details, the damping is effective when the frequency of harmonic load is 2 Hz, but there is no consistent tendency according to damping ratio. The dynamic response when the frequency of harmonic load is 3 Hz shows same result for undamped case as well as for damped case with 5% damping ratio. It is also noted that we can get the largest deflection for damped case with 1% damping ratio. However, there is not any damping effect when the frequency of harmonic load is greater than 4 Hz.

• 전기학회논문지
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• 제59권7호
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• pp.1214-1220
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• 2010

This paper proposes an efficient under frequency relay load shedding scheme for the korea power system which is more than two times than the system size and its capacity of the power system 10 years ago. The proposed method is keeping the power system stability and supports for the operating system during critical situations such as big disturbances and unstable in supply and demand. In order to determine the number of load shedding steps, the load to be shed per step, and frequency level, it is necessary to investigate and analyze maximum losses of generation due to the biggest contingency, maximum system overload, maximum keeping frequency, maximum load to be shed, and recovery frequency. The proposed method is applied to Off-peak load(25,400MW) and Peak load(62,290MW) of Korea Electric Power Corporation to demonstrate its effectiveness.

• Journal of Electrical Engineering and Technology
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• 제5권2호
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• pp.307-318
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• 2010

In this work, an accurate analysis of low frequency current ripple in residential fuel cell power generation systems is performed based on the proposed residential load model and its unique operation algorithm. Rather than using a constant dc voltage source, a proton exchange membrane fuel cell (PEMFC) model is implemented in this research so that a system-level analysis considering the fuel cell stack, power conditioning system (PCS), and the actual load is possible. Using the attained results, a comparative study regarding the discrepancies of low frequency current ripple between a simple resistor load and a realistic residential load is performed. The data indicate that the low frequency current ripple of the proposed residential load model is increased by more than a factor of two when compared to the low frequency current ripple of a simple resistor load under identical conditions. Theoretical analysis, simulation data, and experimental results are provided, along with a model of the load usage pattern of low frequency current ripples.

• 설비공학논문집
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• 제6권4호
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• pp.344-353
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• 1994

This study numerically analyzed the dynamic characteristics of the frequency response on the pneumatic transmission line with load impedances. The pressure transfer function is represented by the distributed parameter line model. To validate the mathematical approximations of Bessel function ratios, the results of frequency response in a blocked line were compared with those obtained by the Infinite-product, Brown's and Square-root approximations. Special emphasis was given to the frequency response characteristics on the pneumatic transmission line with load impedances. Computations were carried out for the wide range of parameters in terms of load capacitance ratio and load resistance ratio. The present results indicated that the theoretical model is capable of accurately predicting the frequency response characteristics for any configuration of a fluid transmission line.

• 대한전기학회:학술대회논문집
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• 대한전기학회 2002년도 추계학술대회 논문집 전력기술부문
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• pp.121-122
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• 2002

When a power system experiences a serious disturbance on insufficient power, the system frequency may drop. For system frequency will be maintain standard value, under_frequency relay will reconstruct balance of power and load by load shedding. Currently load shedding scheme is due to establishment plan by fixed scenario. Where compare current scheme with past scheme, system frequency should be recovered by load shedding using rate of frequency decline. This paper suggests the dynamic load shedding scheme by using the rate of change of frequency when The Korea Electric power system is happened the large disturbance.

• 한국소음진동공학회논문집
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• 제17권2호
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• pp.130-135
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• 2007

The purpose of this paper is that investigates the Natural Frequency behavior characteristic of wind turbine jacket type tower model, and calculated that the stress values of thrust load, wave load, wind load, current loda, gravity load, etc., environment evaluation analysis during static operating wind turbine jacket type tower model, carried out of natural frequency analysis of total load case to stress matrix, frequency calculated that calculated add natural frequency to stiffness matrix for determinant to stress results. The finite element analysis is performed with commercial F.E.M program (ANSYS) on the basis of the natural frequency and mode shape.

• Journal of Advanced Marine Engineering and Technology
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• 제23권1호
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• pp.40-46
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• 1999

A self-tuning FPID(Fuzzy Proportional Intergral Derivative) controller fo load frequency control of 2-area power systemis proposed in this paper. The paramters of the proposed self-tuning FPID controller are self-tuned by the proposed fuzzy inference technique. Therefore in this paper the fuzzy inference technique of PID gains using PSGM(Product Sum Gravity Method) is presented and is applied to the load frequency control of 2-area power system. The computer simulation results show that the proposed controller give better more control characteristics than convention-al PID, FLC under load changes.

• Journal of Advanced Marine Engineering and Technology
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• 제28권6호
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• pp.1017-1025
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• 2004

Generally generator is connected to the bus with no load. After the connection to the bus. the frequency of generator system with no load has to be increased for preventing the reverse power. But in a few case of parallel running with infinite bus system, we have to synchronize the loaded generator to the infinite bus. The frequency of generator system with load has to be lowered for prevention of load shift to the bus system. The blackout of infinite bus decreases the parallel running generator's frequency because of load increasing. In this paper we propose a method that the generator with load maintains the frequency constantly after the blackout of infinite bus. With the constant speed control and load control method of parallel running system to the infinite bus we apply the method to the industrial generating system.

• 한국소음진동공학회:학술대회논문집
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• 한국소음진동공학회 2007년도 춘계학술대회논문집
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• pp.1008-1016
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• 2007

The purpose of this paper is to investigate the Natural Frequency behavior characteristic of Wind Turbine Tower model, and calculated the stress values of thrust load, wave load, wind load, current load, and gravity load. The offshore Jacket Type Tower which was installed in Vitenam South China Sea is used for the study. Natural frequency and mode shape are calculated with commercial program using the measured vibration. The finite element analysis is performed with commercial F.E.M program(ANSYS) on the basis of the natural frequency and mode shape.

• 한국소음진동공학회:학술대회논문집
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• 한국소음진동공학회 2006년도 추계학술대회논문집
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• pp.434-438
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• 2006

The purpose of this paper is that investigates the Natural Frequency behavior characteristic of Wind Turbine Jacket Type Tower model, and calculated that the stress values of Thrust Load, Wave Load, Wind Load, Current Loda, Gravity Load, etc., environment evaluation analysis during static Operating Wind Turbine Jacket Type Tower model, carried out of Natural Frequency analysis of total load case to stress matrix, Frequency calculated that calculated Add Natural Frequency to stiffness matrix for determinant to stress results. The finite element analysis is performed with commercial F.E.M program (ANSYS) on the basis of the natural frequency and mode shape.