• 대한전기학회:학술대회논문집
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• 대한전기학회 1997년도 하계학술대회 논문집 D
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• pp.954-957
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• 1997

In this paper, we analyze the voltage sag caused by reclosing on electric power distribution system. When a fault is on the electric system, a reclosing operation brings a voltage sag on the feeders which is supplied with a common substation transformer. By analyzing the fault wave-form measured in the field, it is showed that a voltage sag is in proportion to a fault current. Also, we propose an adaptive reclosing scheme. This scheme changes the number of reclosing as a function of the magnitude of a fault voltage and the fault type. As the proposed scheme is compared with conventional scheme in the side of voltage sag and permanent fault, it is verified that the proposed scheme is more effective than conventional scheme.

• 조명전기설비학회논문지
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• 제24권9호
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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.

• 대한전기학회:학술대회논문집
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• 대한전기학회 2003년도 하계학술대회 논문집 A
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• pp.3-5
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• 2003

본 논문은 DVR과 DSTATCOM 같은 수 MVA급 용량의 CPD (Custom Power Device)를 평가하기 위한 Sag 및 Swell 전압 발생 장치에 사용될 두 가지 형태의 새로운 회로 방식에 관한 것이다. 제안된 Sag 및 Swell 전압 발생 장치는 계통선로에 직렬로 연결된 직렬 변압기를 통해 다양한 형태로 전압을 발생 시킬 수 있으며, 전격회로는 Solid-State Switched Tap Changer와 AC-Chopper 두 가지 방식을 이용하고 있다. 본 논문에서는 제안된 각각의 방식에 대한 고조파 분석을 하였고, 또한 시뮬레이션을 통해서 제안된 Sag 및 Swell 전압 발생장치를 통해서 원하는 형태의 전압을 얻을 수 있음을 확인하였다.

• 전력전자학회논문지
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• 제17권1호
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• pp.85-92
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• 2012

In this paper, a 300[W] class boost type single-phase inverter system which can compensate voltage sag on source side is designed and implemented. This system is a two-stage conversion system composed of a boost converter and a PWM inverter. If the voltage sag has appeared at the point of common coupling, the boost converter would be operated to compensate it. The boost converter and the inverter were constructed on single smart power module(SPM) to implement low cost system. The system is designed for that the THD of output voltage is below 5[%]. Finally, the validity of the design for the inverter system is verified by both simulations and experiments.

• 한국철도학회논문집
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• 제16권4호
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• pp.272-277
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• 2013

Power quality is a term that is now extensively used in power systems applications, and in this context the voltage, current, and phase angle are discussed widely. In particular, different algorithms that are capable of detecting the voltage sag and swell information in a real time environment have been proposed and developed. Voltage sag and swell play an important role in determining the stability, quality, and operation of a power system. This paper presents ANFIS (Adaptive Network based Fuzzy Inference System) models with different membership functions to build the voltage shape with the knowledge of known system parameters, and detect voltage sag and swell accurately. The performance of each method has been compared with each other/other methods to determine the effectiveness of the different models, and the results are presented.

• 대한전기학회:학술대회논문집
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• 대한전기학회 2001년도 추계학술대회 논문집 전기기기 및 에너지변환시스템부문
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• pp.236-238
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• 2001

Voltage sags are known as a serious problem causing mal-operation of equipment, process controllers and adjustable-speed drives. In this paper various analysis techniques for voltage sags will be presented, voltage sag characterization, equipment behaviour during voltage sag, stochastic assessment of voltage sags. And possible solution to voltage sag sensitivity problems are also described.

• Journal of Power Electronics
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• 제13권2호
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• pp.304-312
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• 2013

The most common power quality problems in distribution systems are related to unbalanced voltage sags. Voltage sags must be detected quickly and corrected in a minimum amount of time. One of the most widely used methods for sag detection is based on the d-q transformation. This method has the disadvantage of missing the detection of unbalanced faults, because this method uses a voltage sag level signal obtained from the average of 3 phases for sag detection. In this paper, an adaptive filter sag detection method is proposed for Dynamic Voltage Restorers (DVR) under unbalanced fault conditions. The proposed DVR controller is able to detect balanced, unbalanced and single phase voltage sags. A novel reference voltage generation method is also presented. To validate the proposed control methods, a 3-phase DSP controlling a DVR prototype with a power rating of 1.5-kVA has been developed. Finally, experimental results are presented to verify the performance of the proposed control methods.

• 한국전기전자재료학회논문지
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• 제25권12호
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• pp.1000-1003
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• 2012

The superconducting fault current limiter (SFCL) can quickly limit the fault current shortly after the short circuit occurs and recover the superconducting state after the fault removes and plays a role in compensating the voltage sag of the sound feeder adjacent to the fault feeder as well as the fault current limiting operation of the fault feeder. Especially, the flux-lock type SFCL with an isolated transformer, which consists of two parallel connected coils on an iron core and the isolated transformer connected in series with one of two coils, has different voltage sag compensating and current limiting characteristics due to the winding direction and the inductance ratio of two coils. The current limiting and the voltage sag compensating characteristics of a SFCL using a transformer winding were analyzed. Through the analysis on the short-circuit tests results considering the winding direction of two coils, the SFCL designed with the additive polarity winding has shown the higher limited fault current than the SFCL designed with the subtractive polarity winding. It could be confirmed that the higher fault current limitation of the SFCL could be contributed to the higher load voltage sag compensation.

• 조명전기설비학회논문지
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• 제23권4호
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• pp.92-100
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• 2009

본 논문은 순간전압강하 추계적 평가를 위한 윈도우즈 프로그램을 소개한다. 개발된 프로그램을 통해 발전기 운전 스케줄링, 시변 사고율 및 부하 전압 민감도 특성을 고려한 순간전압강하 평가가 가능하다. 고장 계산, 취약지역계산, 순간전압강하 발생 횟수 추산 등 다양한 분석 기능들을 가지고 있으며 컴퓨터 그래픽과 애니메이션을 이용한 효과적인 데이터 시각화 기능도 제공하고 있다. 본 논문에서는 순간전압강하 평가의 개념과 발전기 스케줄링 및 시변 사고율을 고려한 순간전압강하 평가 방법에 대한 내용도 기술한다. 또한 개발된 프로그램을 이용한 사례 연구를 통해 순간전압강하 평가에 있어서의 발전기 운전 스케줄링 및 시변 사고율의 영향을 파악한다.

• 전기학회논문지
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• 제63권2호
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• pp.230-236
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• 2014

Superconducting fault current limiter (SFCL) has been expected as one of more effective solutions for decreasing fault current instantaneously and various types of SFCLs have been developed to apply into real power system. Recently, the application of the SFCL in a power distribution system has been reported to be contributed to the suppression of the voltage sag as well as the limitation of the fault current. However, the suppressing effect of voltage sag by the SFCL depends on component of its impedance and its application location in a power distribution system considering the recloser-recloser coordination. This paper analyzed the voltage sag caused by recloser-recloser coordination in a power distribution system and the suppression of the voltage sag due to the application location of the SFCL in a power distribution system was discussed through the PSCAD/EMTDC simulation.