• 제목/요약/키워드: Harmonic Transfer Characteristic

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배전 시스템의 고조파 분석 및 모델링에 관한 연구 (A Study on Harmonics Analysis and Modelling for Distribution System)

  • 왕용필;정종원;정동일
    • 조명전기설비학회논문지
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    • 제21권3호
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    • pp.62-68
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    • 2007
  • 최근 전력 전자 응용 기기의 사용증가로 비선형 특성 부하에 의한 고조파가 상당히 발생하고 있으며, 이에 의한 영향으로 배전시스템의 변압기 열화, 소자의 고장, 통신 간섭 등의 여러 가지 문제를 발생시키고 있다. 따라서 배전 시스템에서의 고조파 수준과 전달특성을 정확하게 분석하기 위하여 배전시스템의 효과적인 실측정과 모델링에 관한 연구가 필요한 실정이다. 본 논문에서는 고조파 관리기준 IEC61000-3-6 토대로 배전 시스템의 고조파 특성을 해석하기 위하여 공통 결합점(Point of Common Coupling : PCC)을 선택하였다. 실 배전 시스템의 PCC 지점에서 고조파 전압, 전류를 측정하여, 고조파 분포, 비선형 부하 성분 및 고조파 전압, 전류 왜형률 (Voltage/Current Total Harmonic Distortion: VTHD/ITHD)을 분석하였다. 또한 정상상태에서 고조파 임피던스, 전압, 전류을 해석을 통하여 실 배전시스템을 효과적이고 정확하게 모델링 되었을 확인하였다. 또한 고조파 전류원 발생시에 고조파 전압, 전류를 비교 분석하여 고조파 전달특성을 조사하였다.

배전시스템 고조파 모델링에 관한 연구 (Harmonics Modelling for Distribution System)

  • 한형주;왕용필;정형환;성병화;박희철;박인표
    • 대한전기학회:학술대회논문집
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    • 대한전기학회 2005년도 제36회 하계학술대회 논문집 A
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    • pp.205-207
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    • 2005
  • In this paper, the Point of Common Coupling (PCC) is selected to analyze harmonic characteristic of distribution system by IEC 61000 - 3 - 6 in Electromagnetic Compatibility(EMC). Harmonic voltage and current were measured at the PCC of real distribution system. Harmonic distribution, nonlinear load component and Total Harmonic Distortion(THD) were verified by measurement. The effective and accurate modelling of real distribution system were proved through a analysis of harmonic impedance, voltage and current in steady-state. Harmonic transfer characteristic in distribution system were summarized and investigated through a analysis of harmonic voltage and harmonic current in harmonic current source.

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An Alternative Approach to Optimal Impulsive-Thrust Formation Reconfigurations in a Near-Circular-Orbit

  • 김영광;박상영;박찬덕
    • 천문학회보
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    • 제37권2호
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    • pp.160.1-160.1
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    • 2012
  • We present an alternative approach for satellite formation reconfiguration by an optimal impulsive-thrust strategy to minimize the total characteristic velocity in a near-circular-orbit. Linear transformation decouples the Hill-Clohessy-Wiltshire(HCW) dynamics into a new block-diagonal system matrix consisting of 1-dimensional harmonic oscillator and 2-dimensional subsystem. In contrast to a solution based on the conventional primer vector theory, the optimal solution and the necessary conditions are represented as times and directions of impulses. New analytical expression of the total characteristic velocity is found for each sub systems under general boundary conditions including transfer time constraint. To minimize the total characteristic velocity, necessary conditions for times and directions of impulses are analytically solved. While the solution to the 1-dimensional harmonic oscillator has been found, the solution to the 2-dimensional subsystem is currently under construction. Our approach is expected to be applicable to more challenging problems.

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Structures of Ammonia Cluster Cations

  • 박종근
    • Bulletin of the Korean Chemical Society
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    • 제20권9호
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    • pp.1067-1072
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    • 1999
  • Structures of unprotonated [(NH3)n+(n = 1-6)] and protonated [NH4+(NH3)n-1(n = 1-6)] ammonia cluster cations have been optimized with ab initio Hartree-Fock (HF) and second-order MФller-Plesset (MP2)/6-31+G ** levels and the harmonic vibrational frequencies have also been evaluated. In unprotonated cluster cations, NH3+ forms as a central core of the first ammonia solvation shell. In protonated cluster cations, NH4+ forms as a central core. In unprotonated dimer and trimer cations, there are two types of isomers (hydrogen-bonded and head-to-head interactions). In both cluster cations, the hydrogen-bonded isomers are more stable. In the hydrogen-bonded dimer cation, the proton transfer reaction takes place from (NH3-HN+H2) to (NH4+-NH2). But in the other unprotonated cluster cations, the proton transfer does not take place. In unprotonated pentamer and hexamer, a NH3+ core has both interactions in a complex. On the other hand, in unprotonated tetramer a core has only the hydrogen-bonded type combined with neutral ammonia molecules. With increasing cluster cation size, the bond lengths [R(NN)] between two nitrogen atoms and the distances [R(N ...H)] of the hydrogen-bond increase reg-ularly. In the calculated infra-red absorption bands for ammonia cluster cations, the characteristic peaks of the bridged NH vibration of the hydrogen-bonded clusters appear near 2500 cm-1 . With increasing size, the peaks shift from 2306 cm-1 to 2780 cm-1 .

A Design of LC-tuned Sinusoidal VCOs Using OTA-C Active Inductors

  • Chung, Won-Sup;Son, Sang-Hee
    • 전기전자학회논문지
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    • 제11권3호
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    • pp.122-128
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    • 2007
  • Sinusoidal voltage-controlled oscillators (VCOs) based on Colpitts and Hartley oscillators are presented. They consist of a LC parallel-tuned circuit connected in a negative-feedback loop with an OTA-R amplifier and two diode limiters, where the inductor is simulated one realized with temperature-stable linear operational transconductance amplifiers (OTAs) and a grounded capacitor. Prototype VCOs are built with discrete components. The Colpitts VCO exhibits less than 1% nonlinearity in its current-to-frequency transfer characteristic from 4.2 to 21.7 MHz and ${\pm}$95 ppm/$^{\circ}C$ temperature drift of frequency over 0 to $70^{\circ}C$. The total harmonic distortion (THD) is as low as 2.92% with a peak-to-peak amplitude of 0.7 V for a frequency-tuning range of 10.8-32 MHz. The Hartley VCO has the temperature drift and THD of two times higher than those of the Colpitts VCO.

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Hartley-VCO Using Linear OTA-based Active Inductor

  • Jeong, Seong-Ryeol;Chung, Won-Sup
    • 전기전자학회논문지
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    • 제19권4호
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    • pp.465-471
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    • 2015
  • An LC-tuned sinusoidal voltage-controlled oscillator (VCO) using temperature-stable linear operational transconductance amplifiers (OTAs) is presented. Its architecture is based on Hartley oscillator configuration, where the inductor is active one realized with two OTAs and a grounded capacitor. Two diode limiters are used for limiting amplitude. A prototype oscillator built with discrete components exhibits less than 3.1% nonlinearity in its current-to-frequency transfer characteristic from 1.99 MHz to 39.14 MHz and $220ppm/^{\circ}C$ frequency stability to the temperature drift over 0 to $75^{\circ}C$. The total harmonic distortion (THD) is as low as 4.4 % for a specified frequency-tuning range. The simulated phase noise of the VCO is about -108.9 dBc/Hz at 1 MHz offset frequency in frequency range of 0.4 - 46.97 MHz and property of phase noise of VCO is better than colpitts-VCO.

A Novel Design of an RF-DC Converter for a Low-Input Power Receiver

  • Au, Ngoc-Duc;Seo, Chulhun
    • Journal of electromagnetic engineering and science
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    • 제17권4호
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    • pp.191-196
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    • 2017
  • Microwave wireless power transmission (MWPT) is a promising technique for low and medium power applications such as wireless charging for sensor network or for biomedical chips in case with long ranges or in dispersive media such. A key factor of the MWPT technique is its efficiency, which includes the wireless power transmission efficiency and the radio frequency (RF) to direct current (DC) voltage efficiency of RF-DC converter (which transforms RF energy to DC supply voltage). The main problem in designing an RF-DC converter is the nonlinear characteristic of Schottky diodes; this characteristic causes low efficiency, higher harmonics frequency and a change in the input impedance value when the RF input power changes. In this paper, rather than using harmonic termination techniques of class E or class F power amplifiers, which are usually used to improve the efficiency of RF-DC converters, we propose a new method called "optimal input impedance" to enhance the performance of our design. The results of simulations and measurements are presented in this paper along with a discussion of our design concerning its practical applications.

가진입력의 크기에 따른 동조액체기둥감쇠기의 비선형 특성 (Nonlinear Characteristic of a Tuned Liquid Column Damper under Various Excitation Amplitudes)

  • 이성경;이혜리;민경원
    • 한국소음진동공학회:학술대회논문집
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    • 한국소음진동공학회 2009년도 추계학술대회 논문집
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    • pp.842-849
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    • 2009
  • The objective of this study is to investigate design parameters of a tuned liquid column damper(TLCD), which is affected by various excitation amplitudes, through shaking table test. Design parameters of a TLCD are examined based on the equivalent tuned mass damper(TMD) model of a TLCD, in which the nonlinear damping of a TLCD is transposed to equivalent viscous damping. Shaking table test is carried out for a TLCD specimen subjected to harmonic waves with various amplitudes. Transfer functions are ratios of liquid displacement of TLCD and control force produced by a TLCD, respectively, with respect to the acceleration excited by a shaking table. They are derived based on the equivalent TMD model of a TLCD. Then, the variation of design parameters according to the excitation amplitude is examined by comparing analytical transfer functions with experimental ones. Finally, the dissipation energy due to the damping of a TLCD, which is experimentally observed from the shaking table test, is examined according to the excitation amplitude. Comparisons between test results and analytical transfer functions showed that natural frequencies of TLCD and the ratio of the liquid mass in a horizontal column to the total liquid mass does not depend on the excitation amplitude, while the damping ratio of a TLCD increases with larger excitation amplitudes.

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가진입력의 크기에 따른 동조액체기둥감쇠기의 비선형 특성 (Nonlinear Characteristic of a Tuned Liquid Column Damper under Various Excitation Amplitude)

  • 이성경;이혜리;민경원
    • 한국소음진동공학회논문집
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    • 제19권11호
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    • pp.1167-1176
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    • 2009
  • The objective of this study is to investigate design parameters of a tuned liquid column damper(TLCD), which is affected by various excitation amplitude, through shaking table test. Design parameters of a TLCD are examined based on the equivalent tuned mass damper(TMD) model of a TLCD, in which the nonlinear damping of a TLCD is transposed to equivalent viscous damping. Shaking table test is carried out for a TLCD specimen subjected to harmonic waves with various amplitude. Transfer functions are ratios of liquid displacement of TLCD and control force produced by a TLCD, respectively, with respect to the acceleration excited by a shaking table. They are derived based on the equivalent TMD model of a TLCD. Then, the variation of design parameters according to the excitation amplitude is examined by comparing analytical transfer functions with experimental ones. Finally, the dissipation energy due to the damping of a TLCD, which is experimentally observed from the shaking table test, is examined according to the excitation amplitude. Comparisons between test results and analytical transfer functions showed that natural frequencies of TLCD and the ratio of the liquid mass in a horizontal column to the total liquid mass do not depend on the excitation amplitude, while the damping ratio of a TLCD increases with larger excitation amplitude.