• Title/Summary/Keyword: Harmonic currents

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A Study on the Transformer Capability containing Harmonic Load Currents (고조파를 포함하는 부하의 변압기 용량 산정에 관한 연구)

  • Kim, Kyung-Chul;Park, Sang-Young;Lee, Il-Moo;Paik, Seung-Hyun
    • Proceedings of the Korean Institute of IIIuminating and Electrical Installation Engineers Conference
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    • 2004.11a
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    • pp.287-292
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    • 2004
  • The increasing use of nonlinear loads has resulted in an increase in the harmonic content of the load current for power transformers. Transformers subject to harmonic currents have higher losses and need to be derated. This paper presents a simple method for determining the capability of transformers to supply harmonic load currents and shows that the application of capacitor banks with a series connected reactor and harmonic filters will geatly increase the capability of transformers. The EDSA program was used as a simulation tool for the carse study.

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Novel Current Compensation Technique for Harmonic Current Elimination (고조파 전류 제거를 위한 새로운 전류 보상 기법)

  • Jeong Gang-Youl
    • Proceedings of the KIPE Conference
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    • 2004.07b
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    • pp.587-591
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    • 2004
  • This paper proposes a novel current compensation technique that can eliminate the harmonic currents included in line currents without computation of harmonic current components. A current controller with fast dynamics for an active filter is described. Harmonic currents are directly controlled without the need for sensing and computing the harmonic current of the load current, thus simplifying the control system. Current compensation is done in the time domain, allowing a fast time response. The DC voltage control loop keeps the voltage across the DC capacitor constant. High power factor control by an active filter is described. All control functions are implemented in software using a single-chip microcontroller, thus simplifying the control circuit. Any current-controlled synchronous rectifier can be used as a shunt active filter through only the simple modification of the software and the addition of current sensors. It is shown through experimental results that the proposed controller gives good performance for the shunt active filter.

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Technical Trend on Excitation Capacitors on Harmonic Amplification of Wind Induction Generator (풍력 유도발전기의 여자 축전지에 따른 고주파 증폭에 관한 기술 동향)

  • Rho, Sang-Pil;Park, Jung-Seok;Lee, Young-Gil;Choi, Yong-Sung;Lee, Kyung-Sup
    • Proceedings of the KIEE Conference
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    • 2007.07a
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    • pp.1976-1977
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    • 2007
  • This paper introduce the electrical quantities of a three-phase-connected wind induction generator (WIG) under sudden connection of static loads. An intelligent power-system recorder/monitor is employed to measure threephase voltages and currents of the studied system at WIG's terminals and load's terminals for 5 minutes. A laboratory 300 W wound-rotor induction machine driven by a blushless DC motor is utilized as the studied WIG. Since the generated harmonic currents are randomly varied, total harmonic distortion (THD) of current using cumulative probability density function is employed to determine the penetration of harmonic distortion. The results show that the harmonic currents generated by the studied WIG may be severely amplified to a high level by the connected self-excited capacitance at the stator's terminals.

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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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    • summer
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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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A Study on the Harmonic Current Characteristic and Emission Value Assess Method Considering the Linear Load (선형부하가 고려된 고조파 전류 특성 및 방출값 평가)

  • Park, Yong-Up;Choi, Seung-Hoon;Chang, Joon-Soo
    • The Transactions of The Korean Institute of Electrical Engineers
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    • v.59 no.1
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    • pp.33-39
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    • 2010
  • In order to operate the power system satisfactory for both system operators and customers, it is important to limit the harmonic currents to the allowable levels which injected into the system from the distorting installations. In this regard, the principles for the allocation of emission limits on individual customer were introduced in the technical report of IEC61000-3-6. According to these general principles, the emission limits are dependent on the agreed power of the customer, the power of the harmonic-generating equipment, and the system characteristics. The considerations in this report are very comprehensive and the process introduced is practical enough to implement as it is. However, there is a fact not appropriately dealing in the report that could be a very tickle but has a huge impact on determining the emission limit. This is the effect of non-harmonic load currents. More precisely, these are from the equipments which do not emit any harmonic or may emit harmonics but this specific order under the consideration by themselves if the source power is sinusoidal. The load currents originated from these equipments have an effect of active filter against the specific order of harmonic therefore, these should be dealt as a significant factoron the process of determining the emission limits for individual customer.

The Ground Impedance Modeling using pattern Search Method for Neutral Hormonic Analysis (Pattern Search 법을 이용한 중성선 고조파 해석용 접지 임피던스 모델링)

  • 백승현;김경철;최종기;이일무;백남웅
    • Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
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    • v.18 no.4
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    • pp.181-187
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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 fall-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.

Influence Analysis of Power Grid Harmonics on Synchronous Hydro Generators

  • Qiu, Hongbo;Fan, Xiaobin;Feng, Jianqin;Yang, Cunxiang
    • Journal of Power Electronics
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    • v.18 no.5
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    • pp.1577-1584
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    • 2018
  • The content of harmonic current increases with an increase in the number of power electronic devices in power grid. When a generator is directly connected to the power grid through a step-up transformer, the influence of the harmonic currents on the generator is inevitable. To study the influences of harmonics on generators, a 24-MW bulb tubular turbine generator is taken as an example in this paper. A 2-D transient electromagnetic field model is established. Through a comparative analysis of the data of experiments and simulations, the correctness of the model is verified. The values of the air gap magnetic density, torque and losses of the generator under various conditions are calculated using the finite element method. Taking the rated condition as a reference, the influence of the harmonic currents on the magnetic flux density is analyzed. It is confirmed that the time harmonic is a key factor affecting the generator performance. At the same time, the effects of harmonic currents on the torque ripple, average torque and eddy current loss of the generator are studied, and the mechanism of the variation of the eddy current loss is also discussed.

The Measurement of the Harmonic Currents in the Household & Office Appliances (가정.사무용 기기의 고조파 전류 측정)

  • Seo, J.C.;Kang, Y.C.;Kim, S.S.;Nam, S.R.;Park, J.K.;Myoung, S.H.;Kang, Y.S.;Choi, H.Y.
    • Proceedings of the KIEE Conference
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    • 1996.11a
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    • pp.149-151
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    • 1996
  • This paper reports the measurement results of the harmonic currents in the household and office appliances. The harmonic currents of 10 items are measured up to 20th order using the no distortion source. These results can be used as a raw data in determining the harmonic current limit in the household and office appliances.

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Performance Improvement of an Active Neutral Harmonic Suppressor System Under Unbalanced Load Conditions

  • Choi, Se-Wan;Jang, Min-Soo
    • Proceedings of the KIPE Conference
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    • 2001.10a
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    • pp.822-828
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    • 2001
  • Three-phase four-wire electrical distribution systems are widely employed in manufacturing plants, commercial and residential buildings. Due to the nonlinear loads connected to the distribution system, the neutral conductor carries excessive harmonic currents even under balanced loading since the triplen harmonics in phase currents do not cancel each other. This may result in wiring failure of the neutral conductor and overloading of the distribution transformer. In response to these concerns, a cost-effective neutral current harmonic suppressor system has been proposed [6]. This paper proposes an improved control method for the harmonic suppressor system under unbalanced load conditions. The proposed control method compensates for only the harmonic components in the neutral conductor, and the zero-sequence fundamental component due to unbalanced loading is prevented from flowing through the harmonic suppressor system. This remedies overloading and power loss of the system. The experimental results on a prototype validate the proposed control approach.

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

  • Choi, Hong-Kyu;Hong, Sun-Suk;Oh, Jung-Suk;Yoo, Tae-Kun
    • Proceedings of the Korean Institute of IIIuminating and Electrical Installation Engineers Conference
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    • 2004.11a
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    • pp.121-127
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    • 2004
  • 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 personal computer loads to evaluate a commercially available series resonant filter for the harmonic currents compensation based on the IEC std 61000-3-2 and IEEE 519 standards for limiting harmonic distortion.

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