• Title, Summary, Keyword: Voltage sag

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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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    • 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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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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Quantitative Evaluation of the Impact of Low-Voltage Loads due to Repetitive Voltage Sags

  • Yun Sang-Yun;Kim Jae-Chul;Moon Jong-Fil;Kang Bong-Seok
    • KIEE International Transactions on Power Engineering
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    • v.5A no.3
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    • pp.293-299
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    • 2005
  • Automatic reclosing is a typical protection method in power distribution systems for the clearing of temporary faults. However, it has a fatal weakness in regards to voltage sags because it produces repetitive voltage sags. In this paper, we explored the repetitive impact of voltage sag due to the automatic reclosing of power distribution systems. The actual tests of low voltage loads were carried out for obtaining the susceptibility of voltage sags. The final results of the tests yielded power acceptability curves of voltage sag, and the curves transformed the 3-dimensional CBEMA (Computer Business Equipment Manufacturer Association) format. For the quantitative evaluation of the impact of repetitive voltage sags, an assessment formulation using the voltage sag contour was proposed. The proposed formulation was tested by using the voltage sag contour data of IEEE standard and the results of the test. Through the case studies, we verified that the proposed method can be effectively used to evaluate the actual impact of repetitive voltage sags.

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.

Design of a Series Voltage Sag Compensation System in Transmission Line

  • Park, Hyen-Young;Kim, Yang-Mo;Lee, Gyo-Sung;Oh, Se-Ho;Park, Jung-Gyun
    • KIEE International Transaction on Electrical Machinery and Energy Conversion Systems
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    • v.2B no.4
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    • pp.191-200
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    • 2002
  • When power consumption increases, power supply must be efficient and reliable for good power quality. The studies on compensation system of power quality are processing actively. Voltage sag among of factors for power quality is generally PI dual control that voltage sag compensation is used. But this control is no more available since of 120[KHz] ripple rejection. So we proposed the control algorithm using PID control in 3-phase unbalanced power system and the series voltage compensator, when voltage sag occurs.

Sag & Swell Detection by Phase Voltage Compensation in 3-Phase Unbalanced Grid (3상 불평형 계통에서의 상 전압 보상을 통한 Sag 및 Swell 검출)

  • Kim, Min-Gi;Kim, Jun-Gu;Jung, Yong-Chae;Won, Chun-Yuen
    • Proceedings of the KIPE Conference
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    • pp.258-259
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    • 2013
  • Load connection or disconnection makes instantaneous sag & swell in 3-phase grid. When unbalance state occurs, between sensed phase voltage and actual phase voltage may have discrepancy. It makes difficult to detect accurate sag & swell, so it is hard to satisfy the standard for switching ESS system to UPS mode. In this paper, we analyzed unbalanced 3-phase voltage, and compensated the actual sag & swell magnitude.

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Stochastic Estimation of Voltage Sags Based on Voltage Monitoring (전압 모니터링에 기반한 순간전압강하 확률적 추계 방법)

  • Son, Jeongdae;Park, Chang-Hyun
    • The Transactions of The Korean Institute of Electrical Engineers
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    • v.67 no.10
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    • pp.1271-1277
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    • 2018
  • This paper deals with a voltage sag assessment based on a voltage monitoring program. The voltage sag performance at a specific site can be evaluated by analyzing voltage monitoring data recorded for a long time period. Although an assessment based on voltage monitoring is an effective way to understand voltage sag performance at a measurement site, the statistical confidence of voltage sag frequency estimation heavily depends on the length of monitoring period and the number of recorded events. Short monitoring period and insufficient recorded data can not provide a reliable assessment result. This paper proposes a compensation assessment method by combining a computer simulation approach for in case that monitoring period and data are not enough for a valid assessment.

Series Voltage Compensation Systems for Voltage Sag by Using an Environmentally Friendly Ultra-capacitor (친환경 Ultra-capacitor에 의한 순시전압강하의 직렬전압보상 시스템)

  • Shon, Jin-Geun;Jeon, Hee-Jong
    • The Transactions of The Korean Institute of Electrical Engineers
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    • v.58 no.4
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    • pp.763-769
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    • 2009
  • A series voltage compensation(SVC) system is a power-electronics controller that can protect sensitive loads from disturbance in the supply system. Especially, voltage sags are considered the dominant disturbances affecting the power quality. This paper dealt with a system of off-line type voltage sag compensation by using a bi-directional DC/DC converter of environmentally friendly ultra-capacitor. This capacitor is attached to the DC link of SVC through the high-efficiency DC/DC converter in order to compensate the DC link voltage drop during short-term power interruption as voltage sags. Therefore, in this paper, a DC/DC converter to control high-efficiency energy of ultra-capacitor and voltage sag detection algorithm of off-line type SVC systems are newly introduced. According to the results of experimental of prototype system, it is verified that the proposed system has effectiveness of voltage sag compensation using an ultra-capacitor.

A novel approach for optimal DG allocation in distribution network for minimizing voltage sag

  • Hashemian, Pejman;Nematollahi, Amin Foroughi;Vahidi, Behrooz
    • Advances in Energy Research
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    • v.6 no.1
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    • pp.55-73
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    • 2019
  • The cost incurred by voltage sag effect in power networks has always been of important concern for discussions. Due to the environmental constraints, fossil fuel shortage crisis and low efficiency of conventional power plants, decentralized generation and renewable based DG have become trends in recent decades; because DGs can reduce the voltage sag effect in distribution networks noticeably; therefore, optimum allocation of DGs in order to maximize their effectiveness is highly important in order to maximize their effectiveness. In this paper, a new method is proposed for calculating the cost incurred by voltage sag effect in power networks. Thus, a new objective function is provided that comprehends technical standards as minimization of the cost incurred by voltage sag effect, active power losses and economic criterion as the installation and maintenance costs of DGs. Considering operational constraints of the system, the optimum allocation of DGs is a constrained optimization problem in which Lightning Attachment procedure optimization (LAPO) is used to resolve it and is the optimum number, size and location of DGs are determined in IEEE 33 bus test system and IEEE 34 bus test system. The results show that optimum allocation of DGs not only reduces the cost incurred by voltage sag effect, but also improves the other characteristics of the system.