• 대한전기학회논문지:전력기술부문A
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• 제48권11호
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• pp.1434-1440
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• 1999

For the real-time power system analysis, there exists a limitation to the scale of the system to be simulated, hence it is necessary for the real-time simulation to develop reduced equivalent systems which preserve the desired property of the original system. In this paper, a procedure for developing an equivalent system whose scale is reduced within the hardware capacity of a real-time simulator is proposed. Also, the proposed procedure is applied to a KEPCO's system. The comparison between the original system and equivalent systems illustrates the capabilities of the proposed procedure.

• 소음진동
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• 제9권3호
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• pp.517-524
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• 1999

Mathematical formulas for multi-dimensional isolation analysis via vibrational power transmission can be derived in a rather simple form when the wave effects of the isolators are completely neglected. With increase of frequency range of interest, however, the wave effects play a very important role and hence cannot be neglected. The formulas get involved accordingly. In this study, a method of equivalent stiffness modeling of the isolators to include the wave effects is proposed in such a way that not only the complexity of the mathematical expressions but also that of experiments of necessity can be reduced. This method is illustratively applied to a two-dimensional vibration isolation system with nonrigid source and base structures.

• 한국철도학회:학술대회논문집
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• 한국철도학회 1998년도 추계학술대회 논문집
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• pp.398-404
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• 1998

The acoustic power reduction methods of the vibrating structures are valid to design the quite structure. To calculate the acoustic power, the dynamic responses have to be determined. It is not easy to analyse the structure composed of the corrugated panels. Because of the structural complexity and the many analysing times. To make up for these defects, the equivalent orthogonal panel is presented. Also the acoustic power prediction method of the vibrating structures is proposed. As examples, the equivalent material properties of the corrugated plates are obtained and the acoustic powers of the floor structure are calculated at several frequency regions for KHST.

• Journal of Power Electronics
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• 제13권6호
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• pp.1008-1015
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• 2013

By using fractional calculus and the circuit-averaging technique, the modeling and analysis of a Buck converter with fractional order inductor and fractional order capacitor in discontinuous conduction mode (DCM) operations is investigated in this study. The equivalent averaged circuit model of the fractional order Buck converter in DCM operations is established. DC analysis is conducted by using the derived DC equivalent circuit model. The transfer functions from the input voltage to the output voltage, the duty cycle to the output voltage, the input impedance, and the output impedance of the fractional order Buck converter in DCM operations are derived from the corresponding AC-equivalent circuit model. Results show that the DC equilibrium point, voltage ratio, and all derived transfer functions of the fractional order Buck converter in DCM operations are affected by the inductor order and/or capacitor order. The fractional order inductor and fractional order capacitor are designed, and PSIM simulations are performed to confirm the correctness of the derivations and theoretical analysis.

• Journal of Power Electronics
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• 제19권5호
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• pp.1326-1335
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• 2019

Common mode (CM) chokes are a crucial part in EMI filters for mitigating the electromagnetic interference (EMI) of switched-mode power supplies (SMPS) and for meeting electromagnetic compatibility standards. However, the parasitic capacitances of a CM choke deteriorate its high frequency filtering performance, which results in increases in the design cycle and cost of EMI filters. Therefore, this paper introduces a negative capacitance generated by a negative impedance converter (NIC) to cancel the influence of equivalent parallel capacitance (EPC). In this paper, based on a CM choke equivalent circuit, the EPCs of CM choke windings are accurately calculated by measuring their impedance. The negative capacitance is designed quantitatively and the EPC cancellation mechanisms are analyzed. The impedance of the CM choke in parallel with negative capacitances is tested and compared with the original CM choke using an impedance analyzer. Moreover, a CL type CM filter is added to a fabricated NIC prototype, and the insertion loss of the prototype is measured to verify the cancellation effect. The prototype is applied to a power converter to test the CM conducted noise. Both small signal and EMI measurement results show that the proposed technique can effectively cancel the EPCs and improve the CM filter's high frequency filtering performance.

• 한국태양에너지학회 논문집
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• 제34권1호
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• pp.1-7
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• 2014

A study on the available power of a wind turbine to be used for wind farm control was performed in this study, To accurately estimate the available power it is important to obtain a suitable wind which represents the three dimensional wind that the wind turbine rotor faces and also used to calculate the power. For this, two different models, the equivalent wind and the wind speed estimator were constructed and used for dynamic simulation using matlab simulink. From the comparison of the simulation result with that from a commercial code based on multi-body dynamics, it was found that using the hub height wind to estimate available power from a turbine results in high frequency components in the power prediction which is, in reality, filtered out by the rotor inertia. It was also found that the wind speed estimator yielded less error than the equivalent wind when compared with the result from the commercial code.

• 대한전기학회:학술대회논문집
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• 대한전기학회 1988년도 추계학술대회 논문집 학회본부
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• pp.236-240
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• 1988

The simplified equivalent by using the short circuit impedance has been used for analyzing the prospective transient recovery voltage of the large power system. But it sometimes generates untorelable error in the rate-of-rise of TRV when using the Thevenin equivalent source. This paper provides the new equivalent by using the multi-port theory. The application of the new method to the sample system gives satisfactory accuracy compared with the short-circuit equivalent.

• Journal of Advanced Marine Engineering and Technology
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• 제34권8호
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• pp.1195-1202
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• 2010

2회로정수 등가회로에 의한 3상유도전동기 모델링 방식은 정격제원만으로 모의운전 특성을 효과적으로 재현하는 장점이 있으나 여자전류의 생략으로 역률 지시에서의 오차가 커지는 문제가 있다. 본 논문에서는 이러한 오차를 해소하기 위한 방안으로 정격 역률이 실제 전동기와 일치되는 조건에서 부하 크기와 관련이 없는 보상전류의 직교 성분을 해석한 후 이를 2회로정수의 부하 전류에 합성하는 방식을 제시하였다. 또한 정격제원으로부터 보상전류와 보정된 값의 전동기 전류, 토크 및 역률을 출력하는 전체적인 과정을 계산하는 연산모듈을 구성하였으며 실제 전동기의 제원을 모듈에 입력하여 나타나는 시뮬레이션 결과를 확인하였다. 이로부터 정격 운전점에서 주요 운전값이 실제 전동기와 일치할 뿐 아니라 슬립에 따른 전체 운전 영역에서 제시된 모듈의 출력 결과가 2회로정수의 경우보다 개선된 모의 특성을 나타내었다.

• 융합신호처리학회논문지
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• 제4권1호
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• pp.41-48
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• 2003

본 논문에서는 DGS(Defected Ground Structure)에 대한 새로운 등가 회로를 제안하였으며, 이를 IMT-2000용 AB급 대전력 증폭기 설계에 적용하여 증폭기의 성능을 향상시켰다. 새로운 DGS 등가 회로는 병렬의 LC 공진기와 병렬 형태의 캐패시턴스로 구성되어 금속 접지면에 에칭된 결함으로 인한 프린징(fringing) 효과를 반영하도록 하였으며, 전력 증폭기 출 단 정합 회로를 최적화하기 위하여 사용되었다. 이전의 논문에서도 하모닉 성분의 억제와 증폭기의 효율 개선을 위하여 DGS를 사용하였으나 DGS 등가 회로의 해석은 없었으며(1), 본 논문에서는 이를 개선하여 회로 시뮬레이션을 통한 정한 DGS의 등가 회로를 AB급 증폭기의 출력 단 정합회로에 적용함으로써 성능 향상과 함께 증폭기 제작 후에 튜닝이 거의 필요없는 정확한 설계 방법을 제시하였다. 이와 같이 제안된 전력 증폭기의 설계 방법은 정확한 설계 결과를 제공함으로써 최적 부하 조건과 하모닉 성분의 제거 성능을 동시에 만족시킬 수 있었다. 제안된 방법의 효과를 입증하기 위하여 DGS를 적용한 기존의 방법과 새로이 제안된 방법을 사용하여 20W급의 전력 증폭기를 설계 및 제작하였으며, 그 측정 결과를 비교하였다.

• KIEE International Transactions on Electrophysics and Applications
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• 제2C권5호
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• pp.246-252
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• 2002

Two-dimensional steady state simulations of planar type radio frequency inductively coupled plasma (RFICP) have been performed. The characteristics of RFICP were investigated in terms of power transfer efficiency, equivalent circuit analysis, spatial distribution of plasma density and electron temperature. Plasma density and electron temperature were determined from the equations of ambipolar diffusion and energy conservation. Joule heating, ionization, excitation and elastic collision loss were included as the source terms of the electron energy equation. The electromagnetic field was calculated from the vector potential formulation of ampere's law. The peak electron temperature decreases from about 4eV to 2eV as pressure increases from 5 mTorr to 100 mTorr. The peak density increases with increasing pressure. Electron temperatures at the center of the chamber are almost independent of input power and electron densities linearly increase with power level. The results agree well with theoretical analysis and experimental results. A single turn, edge feeding antenna configuration shows better density uniformity than a four-turn antenna system at relatively low pressure conditions. The thickness of the dielectric window should be minimized to reduce power loss. The equivalent resistance of the system increases with both power and pressure, which reflects the improvement of power transfer efficiency.