• The Transactions of the Korean Institute of Power Electronics
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• v.10 no.6
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• pp.626-633
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• 2005

This paper proposes a new 2MVA SSFG(Sag Swell Flicker Generator) injecting voltage by using series inverter. The proposed SSFG composes series inverter, DC capacitor as energy storage, rectifier and voltage clamp circuit. This SSFG is designed to generate typical power disturbances, such as voltage sag/swell, over/under voltage and voltage flicker. Also it is designed to generate unexpected voltage phase jumping waveform by controlling the series inverter. In this paper, three kinds of control methods for the proposed 2MVA SSFG we investigated by PSIM simulation. Also typical voltage sag, swell, flicker waveforms are implemented by adopting effective control method.

• The Journal of the Korea institute of electronic communication sciences
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• v.18 no.5
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• pp.859-866
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• 2023

This paper focuses on configuring a user-friendly system of LED systems by applying improvement measures such as gamma correction, non-flicker, and driving noise removal using MCUs and LED drivers. As a result of the experiment, the 22kHz PWM mode of the LED driver generated noise outside the audible frequency range, making it practically imperceptible to users. The appropriate pull-up resistor values within the normal operating delay ratio of 5% were found to be 1kΩ to 10kΩ for the 3kHz PWM mode and 1kΩ to 2kΩ for the 22kHz PWM mode. In addition, gamma correction can be optimized for nonlinear human visual systems to express accurate contrast and as a result, it is expected to develop an LED system that can be expressed more naturally and accurately than conventional LED systems and improve users' visual experience.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.19 no.11
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• pp.2160-2169
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• 1994

Main components of phase time error of synchronous network are flicker noise and random walk noise. This paper describe computer simulation of clock error characterized by a statistical model recommended as a standard measure. Flicker noise sequences are generated from white noise sequences by means of a algorithm developed by Barnes. Random-walk noise sequence are obtained by integration of a white noise sequence. Especially for flicker noise, relation between stage number N, time constant ratio K and bandwidth of flicker noise generated was defined by using some examples.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.27 no.4
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• pp.262-267
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• 2014

This study describes that light flicker of LED lamp is improved by placing an AC-powered LED block in each phase of three-phase AC power. Rectified current is considered as an instantaneous luminous flux because the current flowing through the LED block is proportional to the amount of light emitted by the LED block. Percent flicker is calculated simply by modeling the rectified current flowing through the LED block to a triangular wave current. Percent flicker is 100% in single-phase AC powered LED lamp. Percent flicker of the same level as that in an incandescent lamp (6%~14%) is however, achieved if light emission starts before $40^{\circ}$ in each voltage phase of three-phase AC power.

• Proceedings of the KIEE Conference
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• 2008.11a
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• pp.241-243
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• 2008

태양광 발전 기술의 발달로 용량이 증가함에 따라 계통연계가 증가하고 있다. 본 논문에서는 태양광 발전이 계통에 연계됨에 따라 기존 배전계통에 미치는 전압변동 즉, 플리커 현상을 분석하였다. EMTP/ATPDraw를 이용하여 태양광 발전이 연계된 배전계통을 모델링 하였다. 태양광 발전은 직류가 3상 PWM 인버터를 통하여 교류로 변환되어 계통에 연결되도록 모델링하였다. 태양광 array를 병렬로 연결하여 태양광 발전의 출력량을 증가시켜서, 출력변동에 따른 계통의 전압변동을 분석 하였다.

• Proceedings of the Korean Institute of IIIuminating and Electrical Installation Engineers Conference
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• 2005.05a
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• pp.391-393
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• 2005

This paper studies flicker evaluation considering power quality disturbance. A flicker problem with light device irritates human's eyes. Also, the flicker problem has an influence on adverse effect such as rolling device and rotating device. However, a study of flicker evaluation is not complete. A flicker is measured and evaluated at monitoring point. But we consider power quality disturbances such as voltage sag and transient that cause fault and inverter/breaker switching. Power quality disturbances affects flicker evaluation. A flicker evaluation index increases. Therefore, we consider power quality disturbances. We detect voltage sag and transient using wavelet and evaluate flicker without flicker index including power quality disturbances.

• The Transactions of The Korean Institute of Electrical Engineers
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• v.60 no.9
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• pp.1663-1667
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• 2011

Voltage variation caused by large loads such as arc furnace and large motors, which use the large and instantaneous currents, can cause the voltage flicker. The flicker irritates the human's eyes and also has an adverse effect on protection device, rotating machine and electronic device etc, therefore the flicker needs to be managed effectively. Recently, the Korea power quality standard has been established on the IEC standards. This paper presents the flicker management standard for distribution power system and suggests the flicker transfer coefficients for Korea power system based on the IEC 61000-3-7.

• Proceedings of the KIEE Conference
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• 2006.07a
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• pp.531-532
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• 2006

태양광 발전, 풍력발전 등과 같은 신재생에너지 전원은 주로 수용가에 가까운 배전계통에 연계되어 운영되고 있다. 이들이 도입된 배전계통은 기존의 단방향 공급형태와는 달리 부하와 전원이 혼재되어 운용되고 있으며 양방향 전력공급의 형태로 되기 때문에 전력품질 및 보호협조 측면에서 배전계통에 연계시 복잡한 기술적인 검토가 요구되고 있다. 현재의 경우 수작업이나 EMTDC Tool에 의해 기술검토가 이루어지고 있으나 신뢰성, 정확성, 객관성외 측면에서 다소 미흡한 것이 사실이다. 따라서 한국전력 공사에서 운영하고 있는 신배전정보시스템(NDIS)를 이용하여 8가지 검토항목인 전력용량, 전기방식, 역률, 뱅크역조류, 상시 순시 전압변동, 플리커, 단락용량, 연계가능 용량을 객관적으로 검토할 수 있는 시스템을 개발하였다.

• Proceedings of the KIEE Conference
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• 1999.07c
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• pp.1282-1286
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• 1999

This paper presents the DQ transfomation and space vector modulation method to develop a control algorithm of distribution STATCON(STATic CONdenser) for line voltage regulation, dc link voltage regulation and harmonics compensation. The Performance analysis of a PI with ramp comparision and synchronous reference frame current controller is carried out. Based on these analysis, the control performances are desirable to compensate the harmonics and to regulate de link and line voltage of Distribution line.

• The Transactions of The Korean Institute of Electrical Engineers
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• v.65 no.1
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• pp.179-193
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• 2016

In power quality monitoring, voltage fluctuation is one of the power quality problems, which cause light flickers. To determine the flicker severity, the flicker meter concept was developed in an IEC 61000-4-15 standard. Generally, voltage fluctuations are described as an amplitude modulation(AM). The flicker meter of IEC 61000-4-15 as an international standard for flicker measurement recommends square demodulation method to detect flicker signals from voltage fluctuation signals. This paper suggests a new effective method using filter bank to detect and estimate flicker signals, which do not need square demodulation. For the accurate detection of flicker signals, the filter bank is designed with a full consideration of the spectrum characteristics of voltage fluctuation signals described as AM. The frequency and magnitude of the detected flicker signals are estimated using recursive method. Computer simulations were performed on synthesized signals to prove validity of the proposed method.