• Title, Summary, Keyword: Current and Voltage Harmonics

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A Study on the Characteristic of Capacitor by Voltage and Current Harmonics (전압 및 전류 고조파에 의한 커패시터 동작 특성)

  • Kim, Jong-Gyeum;Park, Young-Jeen;Lee, Dong-Ju;Lee, Eun-Woong
    • The Transactions of the Korean Institute of Electrical Engineers P
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    • v.58 no.3
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    • pp.257-262
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    • 2009
  • Capacitor is basically used for the power-factor compensation and sometimes as the passive filter to reduce harmonics of nonlinear load. Since the impedance of capacitor is inversely proportional to the frequency. The harmonic current may result in the problems of voltage distortion and resonance. Capacitor has easily fall under by two harmonic components, a nonlinear load and a distorted utility voltage. The amplified harmonic current and voltage may damage power capacitor. Hence the pre-investigation of harmonic is needed before designing and application the power factor for reducing fault rate. In this paper, we analyzed that voltage and current with harmonics components act on the capacitor under the resonance condition. we concluded that both voltage and current harmonics have an bad effect on the capacitor and current harmonics is a bitter rather than effect by voltage harmonics.

A Study on the Analysis of Harmonics Aspects on Low-voltage AC Mains (저압 전원계통에서 고조파 양상의 분석에 관한 연구)

  • Lee, Bok-Hee;Baek, Young-Hwan
    • Proceedings of the Korean Institute of IIIuminating and Electrical Installation Engineers Conference
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    • pp.100-103
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    • 2004
  • This paper presents the aspect and distribution of voltage and current harmonics being made at low voltage power systems. The voltage and current harmonics in power systems supplying various loads were monitored and analyzed. We have examined the results compared to advanced countries' harmonics control standards. As a result, the current harmonics were significantly greater than the voltage harmonics. In particular, the harmonics of currents flowing through loads with power switching electronics was pronounced. Also, the contents of current harmonics of street lamp circuits was about 30%, and it was decreased to 12.3% with the installation of series reactor. On the whole, The measured results of voltage and current harmonics exceeds the regulation limits recommended by IEEE 519-1992.

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A Study on the Analysis of Harmonics on Low-voltage AC Lines (저압 전원선의 고조파 분석)

  • Lee, B.H.;Baek, Y.H.
    • Proceedings of the KIEE Conference
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    • pp.1885-1887
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    • 2004
  • This paper presents the aspect and distribution of voltage and current harmonics being made at low voltage power systems. The voltage and current harmonics in power systems supplying various loads were monitored and analyzed. We have examined the results compared to advanced countries' harmonics control standards. As a result, the current harmonics were significantly greater than the voltage harmonics. In particular, the harmonics of currents flowing through loads with power switching electronics was pronounced. Also, the contents of current harmonics of street lamp circuits was about 30%, and it was decreased to 12.3% with the installation of scries reactor. On the whole, The measured results of voltage and current harmonics exceeds the regulation limits recommended by IEEE std 519-1992.

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Influence of System Voltage Harmonics on Arrester Deterioration Diagnostic Techniques by Leakage Current Measurement (누설전류측정에 의한 피뢰기 열화진단기술에 있어 전원고조파의 영향)

  • Kil, Gyung-Suk;Han, Joo-Sup
    • Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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    • pp.142-145
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    • 2002
  • This paper describes an influence of system voltage harmonics on arrester deterioration diagnostic techniques based on leakage current measurement because the resistive current is composed of two components caused by nonlinear characteristics of arrester and by system voltage harmonics. Resistive leakage currents of arresters, which can be evaluated by the third harmonic component of total leakage currents, increase with its deterioration progress. In this paper, we developed a PSpice model for ZnO arrester to simulate the harmonics' effect described above. In simulation, pure sinusoidal voltage and the $3^{rd}$ harmonic voltage are applied to the model, and the leakage current changes are compared. The simulation results showed that the magnitudes of resistive leakage current depend not only on the phase of system voltage harmonics but also on the magnitude of it.

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A Study on the Characteristic of Capacitor by Asymmetrical Voltage Unbalance (비대칭 전압 불평형에 의한 커패시터 동작 특성)

  • Kim, Jong-Gyeum;Park, Young-Jeen
    • The Transactions of the Korean Institute of Electrical Engineers P
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    • v.59 no.1
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    • pp.18-23
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    • 2010
  • As the increasing of Non-linear load, we have been growing interest for the harmonics. Harmonics has been focused on the current component rather than voltages. Voltage harmonics can be mainly generated at the PCC with non-linear load and act on voltage unbalance. Voltage harmonics can be enlarged at the capacitor with low impedance as frequency increases. Capacitor is basically used for the power-factor compensation and sometimes as the passive filter. Small voltage of low-order acts on quite a few at the capacitor by the current increase. Capacitor has easily fall under by harmonic components. In this paper, we measured the magnitude and phase angle of asymmetrical voltage with harmonics components at the PCC and calculated with the same condition. we concluded that voltage harmonics of higher order increase each current component but have a little effect on capacitor rating.

Influence of Harmonics in Power System Voltage on Arrester Deterioration Diagnostics by Leakage Current Measurement (누설전류측정에 의한 피뢰기 열화진단에 있어 전원고조파의 영향)

  • 길경석;한주섭;주문노
    • The Transactions of the Korean Institute of Electrical Engineers C
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    • v.52 no.1
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    • pp.42-46
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    • 2003
  • Arresters are deteriorated by overvoltages or impulse currents, and the resistive leakage current of arresters increases as the deterioration of the arrester progresses, showing an increase in the 3$^{rd}$ harmonic component of the leakage current. In this reason, arrester diagnostic techniques based on the 3$^{rd}$ harmonic leakage current as a reference parameter of deterioration are widely used. The technique, however, includes an error due to the harmonics of power system voltage. Therefore, the influence of the harmonics on arrester diagnostics should be considered. In this paper, we designed a PSpice ZnO arrester model to simulate the influence of the voltage harmonics described above. A pure sinusoidal voltage and its the 3r harmonic voltage were applied to the model, and the leakage current components were analyzed. From the simulation results, it is confirmed that the peak value of resistive leakage current depends not only on the phase of the 3$^{rd}$ harmonic voltage but also on the magnitude of it. Consequently, the errors caused 1)y the harmonic voltage could be minimized by correcting the magnitude of leakage current upon analyzing the harmonics.cs.

Common-Mode Voltage and Current Harmonic Reduction for Five-Phase VSIs with Model Predictive Current Control

  • Vu, Huu-Cong;Lee, Hong-Hee
    • Journal of Power Electronics
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    • v.19 no.6
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    • pp.1477-1485
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    • 2019
  • This paper proposes an effective model predictive current control (MPCC) that involves using 10 virtual voltage vectors to reduce the current harmonics and common-mode voltage (CMV) for a two-level five-phase voltage source inverter (VSI). In the proposed scheme, 10 virtual voltage vectors are included to reduce the CMV and low-order current harmonics. These virtual voltage vectors are employed as the input control set for the MPCC. Among the 10 virtual voltage vectors, two are applied throughout the whole sampling period to reduce current ripples. The two selected virtual voltage vectors are based on location information of the reference voltage vector, and their duration times are calculated using a simple algorithm. This significantly reduces the computational burden. Simulation and experimental results are provided to verify the effectiveness of the proposed scheme.

Characteristic Analysis of Power Compensation Condenser Considering Voltage Harmonics (전압 고조파를 고려한 역률보상용 콘덴서의 특성 분석)

  • Kim, Jong-Gyeum;Lee, Dong-Ju
    • The Transactions of the Korean Institute of Electrical Engineers P
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    • v.59 no.2
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    • pp.141-145
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    • 2010
  • Most of the industrial loads includes the non-linear load as well as the linear load because there are many kinds of power conversion equipments at the input stage of the load in distribution network. The non-linear load causes the distortion of voltage waveform at PCC because the non-linear load generates the harmonic current. As a result, various voltage harmonics are existed at PCC depending on the current harmonics from the non-linear load. And, a series reactor is generally connected to the power capacitor in series to attenuate the distortion of voltage waveform and to reduce an inrush current of power capacitor. Also, harmonic current of power capacitor is highly dependent on the series reactor because it is operated with the power capacitor as a passive filter against nonlinear loads. Then, these capacitors might be damaged by the excessive voltage and current harmonic components. In this paper, we presented how to select the capacitor and series reactor to meet the requirement of the voltage distortion at PCC and analyzed the voltage, current and capacity rating of the power capacitor by the computer simulation to ensure the safe operation of power capacitor when the voltage harmonics at PCC are existed. Also, the analysis data were compared with the experimental measurements for the verification.

Voltage Distortion Suppression for Off-grid Inverters with an Improved Load Current Feedforward Control

  • Geng, Yiwen;Zhang, Xue;Li, Xiaoqiang;Wang, Kai;Yuan, Xibo
    • Journal of Power Electronics
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    • v.17 no.3
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    • pp.716-724
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    • 2017
  • The output voltage of an off-grid inverter is influenced by load current, and the voltage harmonics especially the 5th and 7th are increased with nonlinear loads. In this paper, to attenuate the output voltage harmonics of off-grid inverters with nonlinear loads nearby, a load current feedforward is proposed. It is introduced to a voltage control loop based on the Positive and Negative Sequence Harmonic Regulator (PNSHR) compensation to modify the output impedance at selective frequencies. The parameters of the PNSHR are revised with the output impedance of the off-grid inverter, which minimizes the output impedance of the off-grid inverter. Experimental results verify the proposed method, showing that the output voltage harmonics caused by nonlinear loads can be effectively suppressed.

Simplified Control Scheme of Unified Power Quality Conditioner based on Three-phase Three-level (NPC) inverter to Mitigate Current Source Harmonics and Compensate All Voltage Disturbances

  • Salim, Chennai;Toufik, Benchouia Mohamed
    • Journal of Electrical Engineering and Technology
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    • v.8 no.3
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    • pp.544-558
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    • 2013
  • This paper proposes a simplified and efficient control scheme for Unified Power Quality Conditioner (UPQC) based on three-level (NPC) inverter capable to mitigate source current harmonics and compensate all voltage disturbances perturbations such us, voltage sags, swells, unbalances and harmonics. The UPQC is designed by the integration of series and shunt active filters (AFs) sharing a common dc bus capacitor. The dc voltage is maintained constant using proportional integral voltage controller. The shunt and series AF are designed using a three-phase three-level (NPC) inverter. The synchronous reference frame (SRF) theory is used to get the reference signals for shunt and the power reactive theory (PQ) for a series APFs. The reference signals for the shunt and series APF are derived from the control algorithm and sensed signals are injected in tow controllers to generate switching signals for series and shunt APFs. The performance of proposed UPQC system is evaluated in terms of power factor correction and mitigation of voltage, current harmonics and all voltage disturbances compensation in three-phase, three-wire power system using MATLAB-Simulink software and SimPowerSystem Toolbox. The simulation results demonstrate that the proposed UPQC system can improve the power quality at the common connection point of the non-linear load.