• 대한전기학회:학술대회논문집
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• 대한전기학회 2002년도 합동 추계학술대회 논문집 정보 및 제어부문
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• pp.286-289
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• 2002

In this paper, we use the PI dual control using do transformation(dq stationary frame and dq synchronous rotating frame) for series voltage sag and swell compensation algorithm. Analysis, simulation results are presented for voltage sags and swells on a three-phase unbalanced voltage source.

• 조명전기설비학회논문지
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• 제21권8호
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• pp.34-43
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• 2007

본 연구에서는 배전시스템 안정성의 요소라 할 수 있는 고조파, 전압변동, Sag/Swell, 신뢰도의 측면에서 배전시스템을 전력품질 측면에서 안정성을 종합적으로 평가하는 방법을 개발하였다. 시스템이 전력품질의 측면에서 얼마나 안정적인가를 정량적으로 평가하기 위해서 AHP(Analytic Hierarchy Process)를 사용하여 종합 전력품질 통합지수를 산정하는 방법을 제안하였다. 또한 몬테카를로 시뮬레이션을 수행함으로서 사고를 고려한 배전계통의 안정성을 평가하였다.

• 전력전자학회논문지
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• 제13권3호
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• pp.163-170
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• 2008

본 논문에서는 DVR 등의 전력품질 개선장치들의 성능시험에 용이하게 사용하기 위하여 제안한 3상 전압변동 발생기에 대하여 선형뿐만 아니라 비선형 부하에서도 동작이 가능함을 보이는 스위칭 특성해석을 하였다. 선형 부하의 경우는 전류가 연속이므로 전압변동 발생기를 구성하는 SCR 사이리스터의 자연전류(natural commutation)가 용이하게 발생하지만, 비선형 부하의 경우는 전류 불연속 모드 동작이 발생하여 SCR 사이리스터의 원활한 스위칭이 이루어질 수 없는 경우도 있다. 따라서 비선형 부하 시 전류 불연속 구간에서의 SCR 사이리스터의 스위칭 패턴을 분석하여 전압 새그(sag), 스웰(swell), 순간정전(outage), 전압불평형(voltage unbalance) 동작이 선형에서와 동일하게 발생되는 조건을 파악하였다. 각각의 기능을 발생시키는 원리와 동작 특성을 해석하였으며 시뮬레이션과 실험을 통하여 성능을 확인하였다. 본 논문에서 다룬 전압변동 발생기는 전원 외란 발생을 낮은 비용으로 구현해 낼 수 있고 구조와 제어가 간단하여 전력품질 개선과 관련된 연구를 하는데 용이하게 활용될 것으로 기대한다.

• Journal of Electrical Engineering and Technology
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• 제10권1호
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• pp.379-387
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• 2015

A custom power device provides an integrated solution to the present problems that are faced by the utilities and power distribution. In this paper, a new controller is designed which is connected to a multiconverter unified power quality conditioner (MC-UPQC) for improving the power quality issues adopted modified synchronous reference frame (MSRF) theory with Fuzzy logic control (FLC) technique. This newly designed controller is connected to a source in order to compensate voltage and current in two feeders. The expanded concept of UPQC is multi converter-UPQC; this system has a two-series voltage source inverter and one shunt voltage source inverter connected back to back. This configuration will helps mitigate any type of voltage / current fluctuations and power factor correction in power distribution network to improve power quality issues. In the proposed system the power can be conveyed from one feeder to another in order to mitigate the voltage sag, swell, interruption and transient response of the system. The control strategies of multi converter- UPQC are designed based on the modified synchronous reference frame theory with fuzzy logic controller. The fast dynamics response of dc link capacitor is achieved with the help of Fuzzy logic controller. Different types of fault conditions are taken and simulated for the analysis and the results are compared with the conventional method. The relevant simulation and compensation performance analysis of the proposed multi converter-UPQC with fuzzy logic controller is performed.

• 조명전기설비학회논문지
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• 제21권4호
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• pp.36-44
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• 2007

This study researched the mutual relationship between elevator emergencies(sudden stops, entrapment) and power quality such as voltage interruptions or sags. To analyze the power quality at the elevator switchboard of an apartment, the on-line power quality(sag, swell, and interruption, etc.) were measured and error messages(under voltage error, etc.) in the elevator control room were researched. Also the performance and susceptibility for stops were evaluated and stated through the testing of three pieces of simulated test equipment with an EN12016(2004) standard setting and the magnitude and duration data of the measured sag or interruption. This paper will use these data in the analysis of the mutual relationship between power quality and elevator emergencies.

• Journal of Electrical Engineering and Technology
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• 제10권1호
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• pp.195-204
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• 2015

In this paper, the development of a cost-effective active power filter/uninterruptible power supply (APF/UPS) system with seamless mode transfer is described. The proposed scheme employs a pulse-width-modulation (PWM) voltage-source inverter and has two operational modes. First, when the source voltage is normal, the system operates as an APF, which compensates for the harmonics and power factor while boosting the DC-link voltage to be ready for the disturbance, without an additional DC charging circuit. A simple algorithm to detect the load current harmonics is also proposed. Second, when the source voltage is out of the normal range (owing to sag, swell, or outage), it operates a UPS, which controls the output voltage constantly by discharging the DC-link capacitor. Furthermore, a seamless transfer method for the single-phase inverter between the APF mode and the UPS mode is also proposed, in which an IGBT switch with diodes is used as a static bypass switch. Dissimilar to a conventional SCR switch, the IGBT switch can implement a seamless mode transfer. During the UPS operation, when the source voltage returns to the normal range, the system operates as an APF. The proposed system has good transient and steady-state response characteristics. The APF, charging circuit, and UPS systems are implemented in one inverter system. Finally, the validity of the proposed scheme is investigated with simulated and experimental results for a prototype APF/UPS system rated at 3 kVA.

• 전력전자학회:학술대회논문집
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• 전력전자학회 2009년도 정기총회 및 추계학술대회 논문집
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• pp.287-289
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• 2009

This paper deals with a parallel processing uninterruptible power supply (UPS) for sudden voltage fluctuation in computer applications to integrate power quality improvement, load voltage stabilization and UPS. To reduce the complexity, cost and number of power conversions, which results in higher efficiency, only one voltage-controlled voltage source inverter (VCVSI) is used. The system provides sinusoidal voltage at the fundamental value of 220V/60Hz for the load during abnormal utility power conditions or grid failure. Also, the system can be operated to mitigate the harmonic current and voltage demand from nonlinear loads and provide voltage stabilization for loads when sudden voltage fluctuation occur, such as sag and swell. System operation simulation demonstrates that the system protects against outages caused by abnormal utility power conditions and sudden voltage fluctuations and changes.

• 전력전자학회논문지
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• 제11권5호
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• pp.463-470
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• 2006

본 논문에서는 새로운 방식의 3상 전력품질 외란발생기를 제안하였다. 제안한 방식은 전압새그(sag), 스웰(swell), 순간정전, 전압불평형, 과전압, 저전압 뿐 아니라 위상급변 발생도 가능하다. 전압변동의 각 모드별 동작해석을 하였으며, 특히 위상급변 모드에서의 위상변위량을 정량적으로 제시하였다. 위상변위량은 외란발생기를 구성하는 변압기들의 변압비에 의해 결정되므로 변위량의 설정이 용이하다. 기존방식에 비하여 구조가 간단하고 주요 구성품이 SCR 사이리스터와 변압기류이므로 시스템의 신뢰도가 높고 저렴한 비용으로 구현이 가능하다는 특징이 있다. 또한 PWM 스위칭 없이 동작이 이루어지므로 효율을 극대화할 수 있으며 제어도 용이하다. 각 모드별 동작을 시뮬레이션을 통하여 확인하였으며 5kVA 용량의 부하조건에서 실험을 수행하여 제안한 방식의 타당성을 입증하였다. 제안한 방식의 외란발생기는 UPS, DVR, DSTATCOM, SSTS 등의 전력품질 개선장치들의 성능시험을 하는데 있어서 효과적이고 경제적인 시스템을 구현하고자 하는 경우에 크게 기여할 것으로 기대한다.

• 대한전기학회:학술대회논문집
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• 대한전기학회 2004년도 하계학술대회 논문집 A
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• pp.233-235
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• 2004

Operation of wind turbines has impacts on the voltage quantity at the connected electricity network. Increasing penetration of wind energy makes necessary to study the power quality regarding voltage variations(sag, swell, interruption) and presence of harmonics in the id. This paper investigates the voltage quality of low voltage customers connected to wind generation system. To study the influences of wind power generation to low voltage power system, voltage data are collected in three house using PQM(Power Quality Monitoring) equipment during one month and analyzed regarding voltage variation and harmonics

• 전력전자학회:학술대회논문집
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• 전력전자학회 2008년도 하계학술대회 논문집
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• pp.69-71
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• 2008

Recently, the interest on power quality has been hot issue because the equipments cause voltage disturbance and become more sensitive to the voltage disturbance. The DVR(Dynamic Voltage Restorer) is one of the Custom Power Device that can compensate the voltage. DVR operates as a series connected compensator whose output voltage can be controlled system voltage. And the magnitude of compensation voltage is limited by the characteristics of system and load. Compensation capability of DVR was simulated by EMTDC under several condition. This paper analyzed effect of DVR's compensation at power quality test center which has SSFG(Sag, swell, and Flicker Generator, CPDs(SSTS, DVR, DSTATCOM), and loads.