• Journal of Electrical Engineering and Technology
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• 제8권6호
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• pp.1380-1388
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• 2013

The conventional graphical representation of the instantaneous compensation power flow for single-phase active power filters(APFs) simply represents the active power flow and the reactive power flow which flowing between the power source and the active filter / the load. But, this method does not provide the information about the rectification mode and the compensation mode of APFs, especially, the loss for each mode was not considered at all. This is very important to understand the compensation operation characteristics of APFs. Therefore, this paper proposes the graphical representation of the instantaneous compensation power flow for single-phase APFs considering the instantaneous rectification mode and the instantaneous inversion mode. Three cases are verified in this paper - without compensation, with compensation of the active power 'p' and the fundamental reactive power 'q', and with compensation of only the distorted power 'h'. To ensure the validity of the proposed approach, PSIM simulation is achieved. As a result, we could confirm that the proposed approach was easy to explain the instantaneous compensation power flow considering the instantaneous rectification mode and the instantaneous inversion mode of APFs, also, Total Harmonic Distortion(THD)/Power Factor (P.F) and Fast Fourier Transform(FFT) analysis were compared for each case.

• Journal of Power Electronics
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• 제9권5호
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• pp.718-725
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• 2009

To get instantaneous reference data in a single power system with vector space phasors, the instantaneous load current is adopted as a phase and another new signal, which is delayed through filtering by the phase-delay property of a low-pass filter, is used as the secondary phase. Because the two-phases have a different phase, the instantaneous value of the harmonic current can be obtained without a time-delay in calculation. The reference voltage is created by multiplying the coefficient k by the compensation current using the rotating reference frame synchronized with the source-frequency. To verify the validity of the proposed control method, experiments are carried out on a prototype of the single-phase hybrid active power filter system.

• 전력전자학회논문지
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• 제11권2호
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• pp.172-183
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• 2006

본 논문은 Akagi에 의해 발표된 p-q 이론과 Nabae 및 Peng에 의하여 발표된 크로스벡터 이론의 대비를 통하여 3상 4선 계통에서 순시전력보상방법을 분석한다. 3상 3선 계통에서 영상성분 전압이 없는 경우 두 이론은 똑같다. 그렇지만 3상 4선 계통에서 영상성분 전압과 전류가 포함되는 경우, 두 이론은 순시무효전력과 순시유효전력을 달리 정의한다. 본 논문에서는 이론적 분석과 컴퓨터 시뮬레이션을 바탕으로 영상성분 전압과 영상성분 전류가 존재하는 3상 4선 계통에서 에너지 저장요소의 필요 없이 무효전력만의 보상을 통하여 계통의 중성선 전류를 완벽히 제거할 수 있는 순시전력보상방법을 제시한다.

• Ocean Systems Engineering
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• 제2권3호
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• pp.189-203
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• 2012

New experiments focusing on the evolution characteristics of nonlinear wave trains were conducted in a large wave flume. A series of wave trains with added sidebands, varying initial steepness, perturbed amplitudes and frequencies, were physically generated in a long wave flume. The experimental results show that the increasing wave steepness, increases the speed of sidebands growth. To study the frequency and phase modulation, the Morlet wavelet transform is adopted to extract the instantaneous frequency of wave trains and the phase functions of each wave component. From the instantaneous frequency, there are local frequency downshifts, even an effective frequency downshift was not observed. The frequency modulation increases with an increase in amplitude modulation, and abrupt changes of instantaneous frequencies occur at the peak modulation. The wrapped phase functions show that in the early stage of the modulation, the phase of the upper sideband first diverges from that of the carrier waves. However, at the later stage, the discrepancy phase from the carrier wave transformed to the lower sideband. The phase deviations appear in the front of the envelope's peaks. Furthermore, the evolution of the instantaneous frequency exhibits an approximate recurrence-type for the experiment with large imposed sidebands, even when the corresponding recurrence is not observed in the Fourier spectrum.

• Journal of Electrical Engineering and Technology
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• 제3권1호
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• pp.94-100
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• 2008

This paper presents a new control method of single-phase active power filter (APF) for the compensation of harmonic current components in nonlinear loads. To facilitate the possibility of complex calculation for harmonic current detection of the single phase, a single-phase system that has two phases was constructed by including an imaginary second-phase giving time delay to the load current. The imaginary phase, which lagged the load current T/4 (Here T is the fundamental cycle) is used in the conventional method. But in this proposed method, the new signal as the second phase is delayed by the filter. Because this control method is applied to a single-phase system, an instantaneous calculation was developed by using the rotating reference frames synchronized to source-frequency rather than by applying instantaneous reactive power theory that uses the conventional fixed reference frames. The control scheme of single-phase APF for the current source with R-L loads is applied to a laboratory prototype to verify the proposed control method.

• 전력전자학회논문지
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• 제7권2호
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• pp.178-185
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• 2002

본 연구에서는 왜형되고 불평형인 전원의 정상분 순시전압 검출기법(Detection Method of Instantaneous Positive Sequence Voltage : PSD)에 의한 3상 3선 능동전력필터 시스템을 제작하였다. 불평형 및 왜형된 전원전압은 PSD에 의하여 정상분 순시전압을 실시간으로 검출한 후 순시전력이론의 상변환 행렬을 연산하고 있으며, 따라서 왜형되고 불평형된 전원조건에 순시전력이론을 적용하기 위하여 종전의 순시전력이론의 수학적인 구조를 변경할 필요가 없다. 본 연구에서 구현된 방법의 타당성을 입증하기 위해, 왜형된 B상 전압을 20% 증가시킨 전원과 불평형 비선형 부하 조건하에서 정상상태 및 과도상태의 실험을 수행하였으며, PSD가 없는 방법에 비하여 구현된 방법의 유용성을 입증할 수 있었다.

• Journal of Astronomy and Space Sciences
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• 제28권4호
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• pp.261-265
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• 2011

We investigate the sunspot area data spanning from solar cycles 1 (March 1755) to 23 (December 2010) in time domain. For this purpose, we employ the Hilbert transform analysis method, which is used in the field of information theory. One of the most important advantages of this method is that it enables the simultaneous study of associations between the amplitude and the phase in various timescales. In this pilot study, we adopt the alternating sunspot area as a function of time, known as Bracewell transformation. We first calculate the instantaneous amplitude and the instantaneous phase. As a result, we confirm a ~22-year periodic behavior in the instantaneous amplitude. We also find that a behavior of the instantaneous amplitude with longer periodicities than the ~22-year periodicity can also be seen, though it is not as straightforward as the obvious ~22-year periodic behavior revealed by the method currently proposed. In addition to these, we note that the phase difference apparently correlates with the instantaneous amplitude. On the other hand, however, we cannot see any obvious association of the instantaneous frequency and the instantaneous amplitude. We conclude by briefly discussing the current status of development of an algorithm for the solar activity forecast based on the method presented, as this work is a part of that larger project.

• 전기학회논문지
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• 제56권6호
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• pp.1047-1054
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• 2007

This paper presents a high efficiency direct instantaneous torque control (DITC) of Switched Reluctance Motor(SRM) based on the nonlinear model. The DITC method can reduce the high inherent torque ripple of SRM drive system, but drive efficiency is somewhat low due to the high current and switching loss during commutations. In order to reduce a torque ripple, a fast torque reference trajectory is selected at every instantaneous rotor position. Based on the nonlinear model of SRM, the developing torque by one phase is fixed and the other phase is regulated for minimum switchings of phase switch and variation of torque. The switching during commutation can be reduced and fast commutation can be obtained in the proposed method. As a result, drive efficiency could be improved as well as torque ripple reduction. The validity of proposed method is verified by computer simulations and comparative experiments.

• 전력전자학회:학술대회논문집
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• 전력전자학회 2002년도 추계학술대회 논문집
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• pp.152-157
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• 2002

This paper describes the implementation of 3-phase 3-wire active power filter system with a instantaneous PSD for distorted and unbalanced power conditions. The positive sequence voltage of the distorted and the unbalanced power system Is calculated by the instantaneous PSD, and phase transformation matrix of the instantaneous power theory is achieved with detected positive sequence voltage. Finally, the proposed method is experimented and tested under unbalanced nonlinear load as well as unbalanced/distorted condition in power system.

• 전력전자학회:학술대회논문집
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• 전력전자학회 1997년도 전력전자학술대회 논문집
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• pp.233-238
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• 1997

An important assumption for the active power filter design using instantaneous power theory and the d-q transformation method in a 3-phase power system is based on balanced 3-phase system. However, under pratical conditions, the 3-phase power system can not be continuously balanced due to unbalanced loading. In this paper, a method to control the 3-phase active power filer using instantaneous power theory and the d-q transformation under unbalanced power system is presented and the theoretical results are verified by simulated results.