• Title/Summary/Keyword: Voltage sag

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Development of Three Phase 10kW Voltage Sag Compensator (SEMI F47을 만족하는 10kW급 3상 전압 새그 보상기 개발)

  • Chae, Seung-Woo;Cho, Hyun-Sik;Lee, Il-Yong;Kong, Se-Il;Han, Byung-Moon;Cha, Han-Ju
    • The Transactions of the Korean Institute of Power Electronics
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    • v.17 no.3
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    • pp.198-204
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    • 2012
  • 3-Phase voltage sag compensator protects a critical load from grid sags. The paper presents an algorithm and design of 3-phase voltage compensator. Compensator algorithm consists of a 3-phase voltage sag detection, thyrister commutation method and inverter output voltage control. The compensator satisfies SEMI F47 standard and 10kW 3-phase voltage sag compensator prototype is assembled. Validity of the proposed compensator is verified by simulation and experiment.

Voltage Sag Assessment Considering the Characteristics of Wind Power (풍력 발전 특성을 고려한 순간전압강하 평가)

  • Song, Young-Won;Park, Chang-Hyun
    • The Transactions of The Korean Institute of Electrical Engineers
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    • v.61 no.11
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    • pp.1571-1577
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    • 2012
  • This paper presents a method for assessing the voltage sag performance of power system involving wind power generation. Wind power generation is considered as one of the most desirable renewable energy sources. However, wind power generation have uncertain energy output and it is difficult to control the output. The existing methods of voltage sag assessment are not reflected the characteristics of wind power generation. Therefore, in order to more accurately assess the voltage sag performance, the probability of wind power operation is evaluated. In this paper, the probability is determined by combining the wind speed model with the output curve of wind turbine. The probability of wind power operation is reflected as a parameter in voltage sag assessment. The proposed method can provide more accurate results of voltage sag assessment for the case involving the wind power generation.

A Study on Financial Loss Assessment of Voltage Sags (순간전압강하 경제적 손실 평가 연구)

  • Park, Jomg-Il;Song, Young-Won;Park, Chang-Hyun;Jang, Gil-Soo
    • Proceedings of the KIEE Conference
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    • 2011.07a
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    • pp.324-325
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    • 2011
  • This paper addresses the assessment of voltage sag costs based on the stochastic prediction of voltage sags. When voltage sags below a certain voltage threshold occur at sensitive industrial process, the industrial customer will experience financial damage. In order to mitigate voltage sag costs and devise efficient solutions to mitigate damage, a study on the financial loss assessment of voltage sags is basically needed. In order to assess the voltage sag costs, the expected sag frequency at a sensitive load point should be calculated by using the concept of the area of vulnerability and historical fault statistics. Then, financial loss due to voltage sags can be obtained by multiplying the expected sag frequency by the cost per sag event.

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A Study on Boost Type Single-Phase Inverter System for Compensation of Voltage Sag (Voltage Sag 보상을 위한 승압형 단상 인버터 시스템에 관한 연구)

  • Seo, Young-Min;Lee, Seung-Yong;Hong, Soon-Chan
    • Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
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    • v.25 no.11
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    • pp.50-57
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    • 2011
  • This paper proposes a boost type single-phase inverter system to compensate the voltage sag appeared on source side. The proposed system is composed of a boost converter, a PWM inverter, and a bypass diode. If the voltage sag has appeared in input voltage, the boost converter would be operated to compensate it in the proposed system. The boost converter would not be operated when the magnitude of input voltage is more than 0.9 pu. The output voltage is kept constant by a direct-quadrature frame controller in the inverter. A 300 W class boost type inverter system was simulated, and the validity of the proposed system was verified by carrying out experiments.

A Study of Expanded Severity Index of Voltage Sag Using Fuzzy Clusterin (Fuzzy Clustering을 이용한 순간전압강하(Voltage Sag)의 확장된 심각도 지수(Expanded Severity Index) 연구)

  • Oh, Won-Wook;Kim, Yong-Su
    • Proceedings of the Korean Society of Computer Information Conference
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    • 2011.01a
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    • pp.81-84
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    • 2011
  • 본 논문은 전압 이벤트 현상 중 순간전압강하(Sag) 현상에 초점을 맞추었다. Sag 현상의 심각한 정도를 표현하는 심각도(Voltage Sag Severity) 지수는 동일 지속시간에 대한 임계치와의 비로 표현하였다. 제안하는 확장된 심각도(Expanded Severity) 지수는 sag현상의 분포에 따른 일시반복성의 정보를 표현하였다. 기존의 임계치를 표현하는 ITIC curve를 기반으로 된 심각도와 sag 현상이 발생하는 지속시간-전압 그래프의 분포를 fuzzy clustering을 통하여 medoid를 측정하고, medoid의 심각도와 실제 임계치에 근접한 sag 지점의 심각도를 계산하여 비교하였다. 확장된 심각도 지수는 심각도가 높은 현상들과의 연계성을 나타내는 지수로 심각한 정도의 수치 정보 이외에 일시적인 현상인지 지속 반복적인 현상인지를 0과 1사이의 수치로 표현하였고, 실험을 통하여 입증하였다.

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Voltage Sag Detection Algorithm for Instantaneous Voltage Sag Corrector

  • Lee, Sang-Hoon;Choi, Jae-Ho
    • Journal of Power Electronics
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    • v.2 no.3
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    • pp.162-170
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    • 2002
  • Voltage sag detection algorithm for voltage sag corrector is proposed in this paper. To quantify the standard of voltage unbalance under the faulted conditions, the 3-phase unbalanced voltages are decomposed into two balanced 3-phase symmetrical components of the positive and negative sequence voltages, which is defined by the magnitude factor (MF) and unbalance factor (UF). It is analyzed that MWF and UF values are given as the dc constant values even though under the voltage unbalance condition. This paper also proposes the control scheme of the instantaneous voltage sag corrector based on this detection algorithm. The validity of the proposed algorithm is verified through the EMTDC simulation and experiments.

Countermeasure of Voltage Sag in Radial Power Distribution System using Load Transfer Switching (부하 절환 스위칭을 이용한 방사상 배전계통에서의 순간전압강하 대책)

  • Yun, Sang-Yun;Oh, Jung-Hwan;Kim, Jae-Chul
    • The Transactions of the Korean Institute of Electrical Engineers A
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    • v.49 no.11
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    • pp.558-565
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    • 2000
  • In this paper, we propose a method for mitigating for mitigating the effect of voltage of voltage sag in radial power distribution systems using load transfer switching (LTS). The term of LTS is defined that the weakness load points for voltage sag transfer to the alternative source during the fault clearing practices. The sequenced of proposed LTS method is divided into the search of weakness points for voltage sag using the risk assessment model and transfer behavior of weakness points. The search of weakness point is carried out using the risk assessment model of voltage sag and Monte Carlo simulation method and the historical reliability data in Korea Electric Power Corporation (KEPCO) are also used. Through the case studies, we verify the effectiveness of proposed LTS method and present the searching method of effective application points of LTS method using the risk assessment model.

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A Simulation and Analysis of Voltage Sag Phenomena Using EMTP (EMTP를 이용한 Voltage Sag 현상 모의 및 고찰)

  • Kim, Y.K.;Kim, C.H.;Lee, T.Y.
    • Proceedings of the KIEE Conference
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    • 2003.07a
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    • pp.128-130
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    • 2003
  • In recent years, both utilities and users have expressed their deep concerns about the quality of electric power. Expressed, voltage sag which is one of power quality disturbance is very serious power quality problem on the power system. Voltage sag is a decrease to between 0.1 and 0.9 pu in rms voltage magnitude on the power system for durations from 0.5 cycles to 1 minute. These voltage sags are usually caused by fault condition, overload, and starting of large motors. In this paper, different types of voltage sags are simulated by using EMTP. This paper describes the distinctive characteristic for various sag origins, proposes the effective technique for voltage sag detection using EMTP.

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The Detection of Voltage Sag using Wavelet Transform (웨이브렛 변환을 이용한 Voltage Sag 검출)

  • Kim, Cheol-Hwan;Go, Yeong-Hun
    • The Transactions of the Korean Institute of Electrical Engineers A
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    • v.49 no.9
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    • pp.425-432
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    • 2000
  • Wavelet transform is a new method fro electric power quality analysis. Several types of mother wavelets are compared using voltage sag data. Investigations on the use of some mother wavelets, namely Daubechies, Symlets, Coiflets, Biorthogonal, are carried out. On the basis of extensive investigations, optimal mother wavelets for the detection of voltage sag are chosen. The recommended mother wavelet is 'Daubechies 4(db4)' wavelet. 'db4', the most commonly applied mother wavelet in the power quality analysis, can be used most properly in disturbance phenomena which occurs rapidly for a short time. This paper presents a discrete wavelet transform approach for determining the beginning time and end time of voltage sags. The technique is based on utilising the maximum value of d1(at scale 1) coefficients in multiresolution analysis(MRA) based on the discrete wavelet transform. The procedure is fully described, and the results are compared with other methods for determining voltage sag duration, such as the RMS voltage and STFT(Short-Time Fourier Transform) methods. As a result, the voltage sag detection using wavelet transform appears to be a reliable method for detecting and measuring voltage sags in power quality disturbance analysis.

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Dynamic Voltage Restorer(DVR) with a Z-Source AC Converter Topology (Z-소스 교류 컨버터 토폴로지의 동적 전압 보상기)

  • Lim, Young-Cheol;Jung, Young-Gook
    • Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
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    • v.24 no.9
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    • pp.36-43
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    • 2010
  • This paper proposes a new type of voltage sag-swell compensator based on a Z-source AC-AC converter. The proposed topology employs a pulse width modulation (PWM) Z-source AC-AC converter along with a injection transformer. A safe commutation strategy is used to eliminate voltage spikes on switches without snubber circuit. During a voltage sag or swell, the proposed system controls the adding or missing voltage and maintains the rated voltage of sinusoidal waveform at the terminals of the critical loads. The proposed system is able to compensate 20[%] voltage swell and is also able to compensate 60[%] voltage sag. In order to control and detect the voltage sag and swell, the peak voltage detection method is applied. Also, the operating principles of the proposed system are described, and a circuit analysis is provided. Finally, PSIM simulation and experimental results are presented to verify the proposed concept and theoretical analysis.