• Journal of Power Electronics
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• 제12권5호
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• pp.787-799
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• 2012

Real and reactive power flows on a transmission line interact inherently. This situation degrades power flow controller performance when independent real and reactive power flow regulation is required. In this study, a quasi multi-pulse interline power flow controller (IPFC), consisting of eight six-pulse voltage source converters (VSC) switched at the fundamental frequency is proposed to control real and reactive power flows dynamically on a transmission line in response to a sequence of set-point changes formed by unit-step reference values. It is shown that the proposed hybrid fuzzy-PI commanded IPFC shows better decoupling performance than the parameter optimized PI controllers with analytically calculated feed-forward gains for decoupling. Comparative simulation studies are carried out on a 4-machine 4-bus test power system through a number of case studies. While only the fuzzy inference of the proposed control scheme has been modeled in MATLAB, the power system, converter power circuit, control and calculation blocks have been simulated in PSCAD/EMTDC by interfacing these two packages on-line.

• 전력전자학회논문지
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• 제4권3호
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• pp.304-309
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• 1999

본 논문에서는 새로운 24펄스 다이오드 정류기 시스템을 제안한다. 제안하는 다이오드 정류기 시스템은 기존의 직렬형 12펄스 다이오드 정류기에 수동의 보조회로를 추가함으로서 구성되어지고, 입력전류는 제 22차까지의 고조파가 제거되어 거의 정현파에 가까운 전류 파형을 얻는다. 또한, 출력 전압은 n=24k, k=1,2,3... 의 고조파 성분을 갖는 24펄스 특성를 나타낸다. 더욱이, 이 보조회로의 용량은 출력용량에 비하여 매우 작으며, 능동 스위칭소자를 사용하지 않으므로 외란에 강하고 구현이 간단하다. 따라서, 본 방식은 중·대용량급의 고전압 비제어(uncontrolled) 직류전원이 필요한 인버터나 무정전 전원장치등의 앞단에서 입력고조파의 저감에 경제적이고 효율적이다. 220V, 3KVA 정류기 시스템의 실험을 통하여 제안한 시스템의 타당성을 검증하였다.

• Journal of Power Electronics
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• 제18권1호
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• pp.34-44
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• 2018

This paper presents a pulse-width adjustment (PWA) strategy for a novel bidirectional DC-DC boost converter to improve the performance of the dynamic inductor current response. This novel converter consists of three main components: a full-bridge converter (FBC), a high-frequency isolated transformer with large leakage inductance, and a three-level voltage-doubler rectifier (VDR). A number of scholars have analyzed the principles, such as the soft-switching performance and high-efficiency characteristic, of this converter based on pulse-width modulation plus phase-shift (PPS) control. It turns out that this converter is suitable for energy storage applications and exhibits good performance. However, the dynamic inductor current response processes of control variable adjustment is not analyzed in this converter. In fact, dc component may occur in the inductor current during its dynamic response process, which can influence the stability and reliability of the converter system. The dynamic responses under different operating modes of a conventional feedforward control are discussed in this paper. And a PWA strategy is proposed to enhance the dynamic inductor current response performance of the converter. This paper gives a detailed design and implementation of the PWA strategy. The proposed strategy is verified through a series of simulation and experimental results.

• 한국소음진동공학회논문집
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• 제23권11호
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• pp.951-956
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• 2013

This paper describes techniques used to analyze the sweet spot of sound field reproduced by ear-level linear arrays of loudspeakers by geometrical approach method. Previous researches have introduced various sweet spot definitions in their own way. In general, sweet spot is defined as an area whose stereophonic sound effect is valid. Its size is affected by the geometrical arrangement of the system. In this paper, a case when plane waves are generated by linear arrays of loudspeakers in the horizontal plane is considered. So the sweet spot is defined as an area in which the listener can perceive the desired azimuth angle. Because there are many loudspeakers, impulse responses at listener's ears are in the form of pulse-train and the time-duration of the pulse-train affects the localization performance of the listener. So we calculated the maximum time duration of pulse-train by geometrical approach method and identified with the results of impulse response simulation. This paper also includes parameter analysis with respect to aperture size, so it suggests a tool for sound engineers to expect the sweet spot size and listener's sound perception.

• Earthquakes and Structures
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• 제7권3호
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• pp.365-384
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• 2014

The intensity of a ground motion can be measured by a number of parameters, some of which might exhibit robust correlations with the damage of structures subjected to that motion. In this study, 204 near-fault pulse-type records are selected and their seismic parameters are determined. Time history and damage analyses of a tested 3-storey reinforced concrete frame representing for low-rise reinforced concrete buildings subjected to those earthquake motions are performed after calibration and comparison with the available experimental results. The aim of this paper is to determine amongst several available seismic parameters, the ones that have strong correlations with the structural damage measured by a damage index and the maximum inter-story drift. The results show that Velocity Spectrum Intensity is the leading parameter demonstrating the best correlation, followed by Housner Intensity, Spectral Acceleration and Spectral Displacement. These seismic parameters are recommended as reliable parameters of near-fault pulse-type motions related to damage potential of low-rise reinforced concrete structures. The results also reaffirm that the conventional and widely used parameter of Peak Ground Acceleration does not exhibit a good correlation with the structural damage.

• 융합정보논문지
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• 제11권11호
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• pp.17-22
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• 2021

전자전에서 레이더 신호 해석은 수신한 레이더 신호에서 추출한 신호제원(방향, 주파수, 펄스반복주기, 펄스 폭, 스캔주기)으로 레이더 종류를 식별하는 기술이다. 그러나 신형 레이더, 위협환경이 고도화되면서 레이더 종류를 식별하는 과정에서 레이더 식별 모호성(Ambiguity)가 발생한다. 본 논문에서는 기존 방법의 문제점을 분석하고 새로운 방법을 제안한다. 이 기술은 레이더 스캔 주기의 펄스 도착시간 차이와 스캔주기 판별 최소 수집 개수로 스캔주기 유효성을 판별한다. 실험에 의하여 입력된 신호세기의 RMS((Root Mean Square)와 무관하게 스캔 주기 결과를 도출하는 것을 입증했다.

• Journal of Power Electronics
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• 제19권3호
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• pp.727-743
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• 2019

This paper presents a pulse-width modulation strategy to eliminate the common mode voltage (CMV) with reduced CMV spikes in multilevel inverters since a high CMV magnitude and its fast variations dv/dt result in bearing failure of motors, overvoltage at motor terminals, and electromagnetic interference (EMI). The proposed method only utilizes the zero CMV states in a space vector diagram and it is implemented by a carrier-based pulse-width modulation (CBPWM) method. This method is generalized for odd number levels of inverters including neutral-point-clamped (NPC) and cascaded H-bridge inverters. Then it is extended to the over-modulation mode. The over-modulation mode is implemented by using the two-limit trajectory principle to maintain linear control and to avoid look-up tables. Even though the CMV is eliminated, CMV spikes that can cause EMI and bearing current problems still exist due to the deadtime effect. As a result, the deadtime effect is analyzed. By taking the deadtime effect into consideration, the proposed method is capable of reducing CMV spikes. Simulation and experimental results verify the effectiveness of the proposed strategy.

• Current Optics and Photonics
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• 제6권4호
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• pp.407-412
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• 2022

We report on a diode-laser-pumped mode-locked Yb:KGW laser system, which delivers ultrashort pulses down to 89 fs at a repetition rate of 63 MHz, with an average power of up to 5.6 W. A fiber-coupled diode laser at 981 nm, operated with a compact driver, is used to optically pump the gain crystal via an off-axis parabolic mirror. A semiconductor saturable-absorber mirror is used to initiate the pulsed operation. Laser characteristics such as the pulse duration, spectrum bandwidth, and output power are investigated by varying the intracavity dispersions via changing the number of bounces between negative-dispersive mirrors within the cavity. Short pulses with a duration of 89 fs, a center wavelength of 1,027 nm, and 3.6 W of output power are produced at a group-velocity dispersion (GVD) of -3,300 fs². As the negative GVD increases, the pulse duration lengthens but the output power at the single-pulse condition can be enhanced, reaching 5.6 W at a GVD of -6,600 fs². Because of pulse broadening at high negative GVDs, the highest peak intensity is achievable at a moderate GVD with our system.

• 한국콘텐츠학회논문지
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• 제13권12호
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• pp.27-37
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• 2013

축산업이 대형화 되면서 빠른 성장을 보이고 있다. 하지만 한 농가당 사육두수의 증가로 인한 위생관리부실로 경제적 손실이 전체 총 생산액의 20%인 약 2조원에 육박하고 있고, 이러한 경제적 손실을 막기 위해 축산업에 무선 센서 네트워크 기술 적용이 전 세계에서 연구되고 있다. 본 연구에서는 체온, 호흡수와 더불어 건강의 중요한 지표인 맥박의 지속적인 모니터링을 위한 측정 위치와 방법을 제안한다. 젖소의 중미동맥과 좌측 흉벽에서 맥박을 측정 할 수 있었으며, 측정 방법은 비 침습적이며 탈부착과 관리가 용이한 광 혈류측정 (Photoplethysmography, PPG) 센서를 사용하여 중미동맥과 좌측흉벽에 본 연구에서 제안한 하네스를 이용하여 측정하였다.

• 한국산학기술학회논문지
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• 제21권2호
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• pp.359-365
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• 2020

한방병원에 건강검진을 목적으로 내원한 732명의 피험자를 대상으로 사상체질감별설문지 검사를 통하여 한의사가 감별한 사상체질 결과와 맥진기를 사용하여 촌, 관, 척 부위의 요골 맥파를 측정한 자료를 입수하였다. 입수한 맥파 자료로부터 맥파의 폭, 피크의 크기와 개수를 특징 변수로 추출했다. 특징 변수들 중 타당도와 신뢰도가 높은 것들을 판별변수로 선정했다. 5겹 교차 검증법을 적용하여, 맥파 자료를 사상체질을 알려주는 훈련 표본과 사상체질을 알려주지 않는 예측 표본으로 구분했다. 훈련 표본에 대해서 판별분석을 수행하여 판별 함수를 구한 후, 이것을 예측 표본에 적용하여 사상체질을 예측했다. 예측한 사상체질과 설문지 검사로 알고 있는 사상체질을 비교하여 사상체질 분류 정확도를 계산했다. 사상체질 분류 정확도는 나이별, 성별 보정 전에는 태음인: 73.6 %, 소음인: 68.4 %, 소양인: 74.2 %이었으며, 전체 분류 정확도는 72.5 %이었다. 한국 인구를 기반으로 한 성별, 나이별 가중치를 적용하여 보정을 한 후의 사상체질 분류 정확도는 태음인(70.4 %), 소음인(84.2 %), 소양인(67.7 %)이었으며, 전체 분류 정확도는 73.8 %이었다.