• Title, Summary, Keyword: Harmonic analysis

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Source Model for Harmonic Interaction Analysis between Renewable Energy Generators and Power Distribution System (계통 고조파와 분산형 전원의 상호작용 평가를 위한 고조파 모델에 관한 연구)

  • Cho, Sung-Min;Shin, Hee-Sang;Moon, Won-Sik;Kim, Jae-Chul
    • The Transactions of The Korean Institute of Electrical Engineers
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    • v.60 no.4
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    • pp.733-738
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    • 2011
  • As increase of nonlinear loads and renewable energy generators (REGs) being connected to power distribution system via inverters, the concern on harmonic problems have increased. Recently, the harmonics evaluation method considering TDD (Total Demand Distortion) is used to analyze the effect of harmonics from inverters on power distribution quality. Harmonic current sources are typically used for simulation of nonlinear load. Most inverter type for REGs is voltage source inverter (VSI). So, harmonic voltage sources are more suitable to analyze impact of renewable energy generator on harmonics problem in power distribution system. In this paper, we presented the circuit model to analyze interaction between harmonics from nonlinear load and REGs. We verified that the harmonic analysis using the proposed circuit model is more appropriate than the harmonics evaluation method considering TDD through case study using PSCAD/EMTDC.

The Ground Impedance Modeling for Neutral Harmonic Analysis by Field Tests (현장시험에 의한 중성선 고조파 해석용 접지 임피던스 모델링)

  • Kim Kyung Chul;Park Seung Hyun;Choi Jong Ki;Lee Il Moo;Kim Jong Uk
    • Proceedings of the KIEE Conference
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    • pp.369-371
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    • 2004
  • With the proliferation of nonlinear loads, high neutral harmonic currents in three-phase four-wire distribution system have been observed. It has been. known that the ground impedance has an effect on the neutral currents of a system which operates with harmonics present. On-site measurements of harmonic currents and voltages according to the fell-of-potential method under case study system were made and the ground impedance modeling using the pattern search method for the harmonic analysis was developed. The ground impedance model obtained by the proposed method was compared with the frequency characteristics by field tests and has shown appropriate results, and would be applicable to evaluate the harmonic and transient response characteristics of the ground system.

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Numerical Algorithm for Power Transformer Protection

  • Park, Chul-Won;Suh, Hee-Seok;Shin, Myong-Chul
    • KIEE International Transactions on Power Engineering
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    • v.4A no.3
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    • pp.146-151
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    • 2004
  • The most widely used primary protection for the internal fault detection of the power transformer is current ratio differential relaying (CRDR) with harmonic restraint. However, the second harmonic component could be decreased by magnetizing inrush when there have been changes to the material of the iron core or its design methodology. The higher the capacitance of the high voltage status and underground distribution, the more the differential current includes the second harmonic during the occurrence of an internal fault. Therefore, the conventional second harmonic restraint CRDR must be modified. This paper proposes a numerical algorithm for enhanced power transformer protection. This algorithm enables a clear distinction regarding internal faults as well as magnetizing inrush and steady state. It does this by analyzing the RMS fluctuation of terminal voltage, instantaneous value of the differential current, RMS changes, harmonic component analysis of differential current, and analysis of flux-differential slope characteristics. Based on the results of testing with WatATP99 simulation data, the proposed algorithm demonstrated more rapid and reliable performance.

Analysis of the Harmonic Resonance during Restoration of Primary Restorative Transmission System (시송전계통 탁구과정에서의 고조파 공진 현상에 대한 고찰)

  • Lee, H.J.;Lee, K.S.;Park, S.M.
    • Proceedings of the KIEE Conference
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    • pp.220-222
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    • 2005
  • Power system restoration following a wide area or complete blackout starts with energizing primary restorative transmission systems. During this primary restoration process, unexpected over-voltage may happen due to nonlinear interaction between the unloaded transformer and the transmission system. This is known as the harmonic resonance phenomenon that may cause burning out of transformer or other devices. Since the harmonic resonance originates from the nonlinear characteristics, it is very difficult to predict the occurrence of this phenomenon. This paper reports the possible existence of the harmonic resonance in Korean power system. Analysis of the harmonic over-voltage is presented based on the various simulations using PSCAD/EMTDC.

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A Study on the Hormonic Analysis of on Electronic Ballast (전자식 안정기의 고조파 저감 대책)

  • Hong, Soon-Seuk;Oh, Jung-Suk;Yoo, Tae-Kun
    • Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
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    • v.19 no.2
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    • pp.35-41
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    • 2005
  • Electric ballast is widely used to turn on the fluorescent. Electric ballast measure occurrence of harmonic through the actual measurement and it is simulated by modeling equivalent circuit for harmonic analysis. The purpose of this paper is to give an equivalent circuit modeling methodology for the harmonic currents generated by single-phase loads to evaluate a commercially available series resonant filter for the harmonic currents compensation based on the IEC 61000-3-2 and IEEE Std 519-1992 standards for limiting harmonic distortion.

Harmonic Impact Studies of Grid-Connected Wind Power and PV Generation Systems (계통연계 풍력 및 태양광발전시스템 고조파 영향 검토)

  • Lee, Sang-Min;Jung, Hyong-Mo;Yu, Gwon-Jong;Lee, Kang-Wan
    • The Transactions of The Korean Institute of Electrical Engineers
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    • v.58 no.11
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    • pp.2185-2191
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    • 2009
  • Wind power and photovoltaic(PV) generation systems are the fastest growing sources of renewable energy. The nonlinear devices, such as power electronic converter or inverter, of wind power and PV generation systems are the source of harmonics in power systems. The harmonic-related problems can have significant detrimental effects in the power system, such as capacitor heating, data communication interference, rotating equipment heating, transformer heating, relay misoperation and switchgear failure. There is a greater need for harmonic analysis that can properly maintain the power quality. By measuring harmonics of existing wind power and PV generation systems as harmonics modeling, the studies were made to see the harmonic impact of grid-connected wind power and PV generation systems.

Harmonic Winding Factors and MMF Analysis for Five-phase Fractional-slot Concentrated Winding PMSM

  • Kang, Huilin;Zhou, Libing;Wang, Jin
    • Journal of international Conference on Electrical Machines and Systems
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    • v.3 no.1
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    • pp.20-26
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    • 2014
  • To enhance torque density by harmonic current injection, optimal slot/pole combinations for five-phase permanent magnet synchronous motors (PMSM) with fractional-slot concentrated windings (FSCW) are chosen. The synchronous and the third harmonic winding factors are calculated for a series of slot/pole combinations. Two five-phase PMSM, with general FSCW (GFSCW) and modular stator FSCW (MFSCW), are analyzed and compared in detail, including the stator structures, star of slots diagrams, and MMF harmonic analysis based on the winding function theory. The analytical results are verified by finite element method, the torque characteristics and phase back-EMF are also taken into considerations. Results show that the MFSCW PMSM can produce higher average torque, while characterized by more MMF harmonic contents and larger ripple torque.

An algorithm to infer the central location of a solenoid coil for the mapping process based on harmonic analysis (조화해석 기반의 맵핑을 위한 솔레노이드 코일의 중심위치 추론 알고리즘)

  • Lee, Woo-Seung;Ahn, Min-Cheol;Hahn, Seung-Yong;Ko, Tae-Kuk
    • Progress in Superconductivity and Cryogenics
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    • v.14 no.1
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    • pp.14-19
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    • 2012
  • Shimming, active and/or passive, is indispensable for most MR (magnetic resonance) magnets where homogeneous magnetic fields are required within target spaces. Generally, shimming consists of two steps, field mapping and correcting of fields, and they are recursively repeated until the target field homogeneity is reached. Thus, accuracy of the field mapping is crucial for fast and efficient shimming of MR magnets. For an accurate shimming, a "magnetic" center, which is a mathematical origin for harmonic analysis, must be carefully defined, Although the magnetic center is in general identical to the physical center of a magnet, it is not rare that both centers are different particularly in HTS (high temperature superconducting) magnets of which harmonic field errors, especially high orders, are significantly dependent on a location of the magnetic center. This paper presents a new algorithm, based on a field mapping theory with harmonic analysis, to define the best magnetic center of an MR magnet in terms of minimization of pre-shimming field errors. And the proposed algorithm is tested with simulation under gaussian noise environment.

High-Performance Millimeter Wave Harmonic Output Oscillator using Sub-Harmonic Wave Injection-Synchronization (서브하모닉 주입동기에 의한 밀리미터파 대역 고조파 발진기의 고성능화)

  • Choi, Young-Kyu;Nam, Byeong-Gun
    • Journal of the Korea Institute of Information and Communication Engineering
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    • v.12 no.1
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    • pp.17-24
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    • 2008
  • This paper deals with a millimeter wave source which is utilizing sub-harmonic injection-synchronization technique. A 8.7GHz oscillator with MES-FET is fabricated, and is driven as a harmonic output oscillator at 17.4GHz by means of sub-harmonic injection-synchronization. The oscillator operates as a multiplier as well as oscillator in this system. Adopting this technique, we can obtain a high stable, high frequency millimeter wave source even though self-oscillating frequency of an oscillator is relatively low. In the experiments, the range of injection-synchronization is about 26MHz and is proportional to the input sub-harmonic power. From the spectrum analysis of the 2nd harmonic output. we blow that the phase noise of the harmonic oscillator is remarkably decreased.

The Simple Harmonic Analysis Method of the Multi-Carrier PWM Techniques by Using the Output Phase Voltage in the Multi-Level Inverter (출력 상전압을 이용한 멀티-캐리어 PWM 기법의 간단한 고조파 분석 방법)

  • 김준성;김태진;강대욱;현동석
    • The Transactions of the Korean Institute of Electrical Engineers B
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    • v.52 no.7
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    • pp.352-360
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    • 2003
  • This paper deals with a simple method in order to analyze and compare the harmonic characteristics in the multi-level inverter. Generally, the magnitude of harmonic components becomes different according to the multi-carrier Pulse Width Modulation(PWM) techniques, the modulation index($M_i$) and the switching frequency The previous papers analyzed the harmonic characteristics from the viewpoint of the space voltage vector. Hence, the calculation of the harmonic vector becomes more difficult and complex in 4-level or over 5-level. However, the proposed method has reduced an amount of calculation and simplified the process of it, using the relationship between the reference voltage and the output phase voltage to the load neutral point. It is applied to the 5-level cascade inverter and the harmonic characteristics for each multi-carrier PWM technique are compared through the simulation.