• Title, Summary, Keyword: Voltage sag

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An Improvement in Synchronously Rotating Reference Frame-Based Voltage Sag Detection under Distorted Grid Voltages

  • Sillapawicharn, Yutthachai;Kumsuwan, Yuttana
    • Journal of Electrical Engineering and Technology
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    • v.8 no.6
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    • pp.1283-1295
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    • 2013
  • This study proposed an improvement in synchronously rotating reference frame-based voltage sag detection under distorted grid voltages. In the past, the conventional synchronously rotating reference frame (CSRRF)-based voltage sag detection was generally used in the voltage sag compensation applications. Its disadvantage is a long delay of detection time. The modified synchronously rotating reference frame (MSRRF)-based voltage sag detection is able to detect the voltage sag with only a short delay in detection time. However, its operation under distorted grid voltage conditions is unavailable. This paper proposed the improvement of modified synchronously rotating reference frame (IMSRRF)-based voltage sag detection for use in distorted grid voltages with very fast operation of voltage sag detection. The operation of the proposed voltage sag detections is investigated via simulations and experimentations to verify the performance of the IMSRRF-based voltage sag detection.

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.

Stochastic Method to Assess Voltage Sag Performance Considering Sag Duration in Large Power System (대규모 계통에서의 순간전압강하 지속시간을 고려한 추계적 평가 방법)

  • Lee, Myeong-Cheol;Park, Chang-Hyun
    • Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
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    • v.30 no.2
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    • pp.85-92
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    • 2016
  • The paper presents a method to assess system voltage sag performance considering sag durations as well as magnitudes. In general, voltage sag assessment for large power systems is performed only considering sag magnitudes at sensitive load points. However some equipment can be affected by certain sag durations. The duration of the voltage sag is depend on the time of fault current flow in the system. Therefore, the duration can be determined by analyzing the operating characteristic of the protection system. In this paper, an effective method to evaluate sag durations regarding the characteristics and failure rates of the protection system is described. The proposed method can be used to assess the long-term performance of the voltage sags in large power system.

An Analysis the Distribution Power System Voltage Sag Case by a High Capacity Motor Connection (대용량 전동기 기동시 배전계통의 순간전압강하 발생사례 분석)

  • Park, Yong-Up;Lee, Keon-Hang
    • Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
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    • v.24 no.10
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    • pp.143-148
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    • 2010
  • Recently, the KEPCO is constructing the PQMS(Power Quality Monitoring System) each of the distribution line and will establish the voltage sag standard based on the long time measurement data of PQMS. The voltage sag prospect is difficult for the power system manager, however, the voltage sag forecasted is very important because the damage effect of the voltage sag is very broad. This paper describes the prospect formula of the voltage sag magnitude in the PCC(Point Common Coupling) by the starting current when the high capacity equipment is connected with the distribution line. To achieve this, this paper has proposed the sag prospect formula revision of KEPCO for the reliability improvement and the proposed formula has been applied the voltage sag real case to inspect the calculation procedure and reliability.

A Dynamic Characteristics on Non-linear Voltage Electric Equipment under Voltage Sag (순간전압강하에 대한 비선형 저압전기기기의 동적특성)

  • Lee, Hyun-Chul;Jeong, Sung-Won;Gim, Jae-Hyeon;Lee, Geun-Joon
    • The Transactions of The Korean Institute of Electrical Engineers
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    • v.57 no.3
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    • pp.336-343
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    • 2008
  • In this study, a transition of power quality was characterized by non-linear voltage electric equipments under voltage sag. The test was inputted voltage sag to IPC(Sag Generator) from AVR, and then to equipments by IPC which adjust voltage magnitude and duration. The load test which non-linear voltage electric equipments used PLC, Magnetic Contactor, SMPS, HID Lamp. The test result was different from each other according to a manufacturing companys, models, and equipments. PLC was greatly described to be stabilized voltage sag in case of no load then rated load. Magnetic Contactor was made a difference to phase angles on voltage sag, which was $0^{\circ}$, $30^{\circ}$, $60^{\circ}$, $90^{\circ}$. HPD Lamp was described to be stabilized the sodium lamp, and to be unstabilized the metal hailed lamp. The test result was showed CBEMA curve that stand for evaluated responsiveness of voltage sag. This study was tested description to dynamic characteristics on non-linear voltage electric equipment under voltage sag. There was hoped that power system designed the essential particulars.

Three-Phase PWM-Switched Autotransformer Voltage-Sag Compensator Based on Phase Angle Analysis

  • Mansor, Muhamad;Rahim, Nasrudin Abd.
    • Journal of Power Electronics
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    • v.11 no.6
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    • pp.897-903
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    • 2011
  • Many voltage sag compensators have been introduced, including the traditional dynamic voltage restorer (DVR), which requires an energy storage device but is inadequate for compensating deep and long-duration voltage sags. The AC-AC sag compensators introduced next do not require a storage device and they are capable of compensating voltage sags. This type of compensator needs an AC-AC converter to regulate the output voltage. Presented in this paper is a three-phase PWM-switched autotransformer voltage sag compensator based on an AC-AC converter that uses a proposed detection technique and PWM voltage control as a controller. Its effectiveness and capability in instantly detecting and compensating voltage sags were verified via MATLAB/Simulink simulations and further investigated through a laboratory prototype developed with a TMS320F2812 DSP as the main controller.

Development of a Method to Analyze Voltage Sag Monitoring Data (순간전압강하 모니터링 데이터 분석 방법)

  • Park, Chang-Hyun
    • Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
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    • v.27 no.4
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    • pp.16-22
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    • 2013
  • This paper presents a method to analyze the voltage sag data obtained from monitoring systems. In order to establish effective countermeasures against voltage sag problems, an assessment of the system performance with respect to voltage sags is needed. Generally, the average annual sag frequency can be estimated by using the recorded voltage sag events for several years. However, the simple average value can not give the information about the errors of estimation. Such an average estimation is not useful for establishing effective solutions for voltage sag problems. Therefore, this paper proposes an effective method based on the Interval Estimation method. The estimation of voltage sag frequency is performed by using the average frequency and Poisson probability model. The proposed method can give the expected annual sag frequency and upper one-sided bound frequency.

Single-Phase Series Type Quasi Z-Source Voltage Sag-Swell Compensator for Voltage Compensation of Entire Region (전 영역의 전압보상을 위한 단상 직렬형 Quasi Z-소스 전압 Sag-Swell 보상기)

  • Eom, Jun-Hyun;Jung, Young-Gook;Lim, Young-Cheol
    • The Transactions of the Korean Institute of Power Electronics
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    • v.18 no.4
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    • pp.322-332
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    • 2013
  • Conventional single-phase series quasi Z-source voltage compensator can not compensate for voltage sag less than 50% that frequently occurs in the industrial field. In this study, single-phase series quasi Z-source voltage sag-swell compensator which can compensate the voltage variation of entire range is proposed. The proposed system is composed of two quasi Z-source AC-AC converters connected in series with output terminal stage. Voltage sag less than 50% could be compensated by the intersection switching control of the upper converter duty ratio and of the upper converter duty ratio. Also the compensation voltage and its flowchart for each compensation mode are presented for entire sag-swell region. To confirm the validity of the proposed system, a DSP(DSP28335) controlled experimental system was manufactured. As a result, the proposed system could compensate for the voltage sag/swell of 20% and 60%. Finally, voltage compensation factor and THD(Total Harmonic Distortion) according to voltage variation and load change were measured, and voltage quality shows a good results.

Fast Detection Algorithm for Voltage Sags and Swells Based on Delta Square Operation for a Single-Phase Inverter System

  • Lee, Woo-Cheol;Sung, Kook-Nam;Lee, Taeck-Kie
    • Journal of Electrical Engineering and Technology
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    • v.11 no.1
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    • pp.157-166
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    • 2016
  • In this paper, a new sag and peak voltage detector is proposed for a single-phase inverter using delta square operation. The conventional sag detector is from a single-phase digital phase-locked loop (DPLL) that is based on d-q transformations using an all-pass filter (APF). The d-q transformation is typically used in the three-phase coordinate system. The APF generates a virtual q-axis voltage component with a 90° phase delay, but this virtual phase cannot reflect a sudden change in the grid voltage at the instant the voltage sag occurs. As a result, the peak value is drastically distorted, and it settles down slowly. A modified APF generates the virtual q-axis voltage component from the difference between the current and the previous values of the d-axis voltage component in the stationary reference frame. However, the modified APF cannot detect the voltage sag and peak value when the sag occurs around the zero crossing points such as 0° and 180°, because the difference voltage is not sufficient to detect the voltage sag. The proposed algorithm detects the sag voltage through all regions including the zero crossing voltage. Moreover, the exact voltage drop can be acquired by calculating the q-axis component that is proportional to the d-axis component. To verify the feasibility of the proposed system, the conventional and proposed methods are compared using simulations and experimental results.

Stand-Alone Type Single-Phase Fuel Cells Micro-Source with ac Voltage Compensation Capability (교류전압 보상 기능을 갖는 독립형 단상 연료전지 마이크로 소스)

  • Jung, Young-Gook
    • The Transactions of The Korean Institute of Electrical Engineers
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    • v.58 no.1
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    • pp.35-41
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    • 2009
  • This paper proposes a stand alone type single-phase fuel cells micro-source with a voltage sag compensator for compensating the ac output voltage variations (sag or swell) of micro-source. The proposed micro-source is consist of a PEM(polymer electrolyte membrane) fuel cells simulator, a full bridge de converter, a 60Hz PWM(pulse width modulation) VSI(voltage source inverter), and a voltage sag compensator. Voltage sag compensator is similar to the configuration of hybrid series active power filter, and it is directly connected to micro-source through the injection transformer. Compensation algorithm of a voltage sag compensator adopts a single phase p-q theory. Effectiveness of the proposed the system is verified by the PSIM(power electronics simulation tool) simulation in the steady state and transient state which the proposed system is able to simultaneously compensate the harmonic current and source voltage sag or swell.