• Journal of Power Electronics
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• v.10 no.2
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• pp.203-209
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• 2010

This paper describes the development of a three-phase line-interactive DVR with a new sag detection algorithm. The developed detection algorithm has a hybrid structure composed of an instantaneous detector and RMS-variation detectors. The source voltage passes through the sliding-window DFT and RMS calculator, and the instantaneous sag detector. If an instantaneous sag is detected, the RMS variation detector-1 is selected to calculate the RMS variation. The RMS variation detector-2 is selected when the instantaneous sag occurs under the operation of the RMS variation detector-1. The feasibility of the proposed algorithm is verified through computer simulations and experimental work with a prototype of a line-interactive DVR with a 3kVA rating. The line-interactive DVR with the proposed algorithm can compensate for an input voltage sag or an interruption within a 2ms delay. The developed DVR can effectively compensate for a voltage sag or interruption in sensitive loads, such as computers, communications equipment, and automation equipment.

• Proceedings of the KIEE Conference
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• 2001.10a
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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.

• The Transactions of the Korean Institute of Electrical Engineers A
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• v.49 no.4
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• pp.177-184
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• 2000

In this paper, we proposes a method for assessing the effect of voltage sag in power distribution systems using fuzzy model. The proposed method is based on the reliability data of distribution system and specified computer business equipment manufacturer association(SCBEMA) curve that express the representative power acceptability curve by voltage sag for each customer type. The SCBEMA curves are made by using the CBEMA curves obtained from the experiment for the customers sensitive equipment. In order to transform SCBEMA curves to the differential damage by voltage sag, a fuzzy model is used. The proposed fuzzy model is composed to reflect two parameters of customers damage by voltage sag. One is the duration and magnitude of voltage sag and the other is the different risk due to the customer types. The Monte Carlo simulation method and the historical reliability data in KEPCO ae used for case studies.

• Proceedings of the KIEE Conference
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• 2015.07a
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• pp.323-324
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• 2015

Voltage sag phenomenon is known as one of the important problems that brought huge economic losses in the modern industry. The voltage sag assessment is to predict an annual expected sag frequency (ESF) at concerned consumers caused by fault in the system. An area of severity (AOS) assessment is defined as a set of the fault positions that can result in the voltage sag bigger than certain level for multi-concerned buses simultaneously. This paper introduces how to determine a method for evaluating the voltage sag performance based on the AOS assessment.

• Journal of Power Electronics
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• v.13 no.2
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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.

• Proceedings of the KIPE Conference
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• 2014.07a
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• pp.142-143
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• 2014

본 논문에서는 Buck type의 단상 AC/AC 초퍼를 이용한 단상 voltage sag compensator를 제안한다. 제안된 회로는 sag보상 동작 시 사용된 변압기의 누설리액턴스가 단상 PWM Buck AC/AC converter에 미치는 영향이 작아 동작효율이 높고, sag가 발생하지 않는 상태일 때 입력과 출력이 절연되는 장점이 있다. 본 논문에서는 제안된 회로의 동작 및 특성을 설명하고, 타당성을 입증하기 위해 PSIM으로 시뮬레이션 하였다.

• Proceedings of the KIPE Conference
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• 2014.07a
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• pp.144-145
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• 2014

본 논문에서는 Buck type의 3상 AC/AC 초퍼를 이용한 3상 voltage sag compensator를 제안한다. 제안된 회로는 sag보상 동작 시 사용된 변압기의 누설리액턴스가 3상 PWM Buck AC/AC converter에 미치는 영향이 작아 동작효율이 높고, sag가 발생하지 않은 상태일 때 입력과 출력이 절연되는 장점이 있다. 본 논문에서는 제안된 회로의 동작 및 특성을 설명하고, 타당성을 입증하기 위해 PSIM으로 시뮬레이션 하였다.

• Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
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• v.28 no.12
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• pp.65-73
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• 2014

In this paper, the detection scheme of the voltage variation using a two difference voltage is proposed. The conventional sag detector is from a single-phase digital phase-locked loop (DPLL) that is based on a d-q transformation using an all-pass filter (APF). The APF generates a virtual q-axis voltage component with $90^{\circ}$ phase delay but the APF cannot generate the virtual q-axis voltage depending on the phase of the grid voltage. To overcome the problem, q-axis voltage component is generated from difference between the current and previous value of d-axis voltage component in the stationary reference frame. However, the difference voltage around the zero crossing is not enough to detect the voltage sag. Therefore, the new detection scheme using the two difference voltage which can detect the sag around the zero crossing voltage is proposed.

• Proceedings of the KIPE Conference
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• 2011.07a
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• pp.352-353
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• 2011

This paper proposes a cascaded boost type inverter system to compensate the voltage sag. If the voltage sag has appeared in input voltage, a cascaded boost converter would be operated to compensate voltage sag. The output voltage is kept constant by a direct-quadrature frame controller in the single-phase PWM inverter. The validity of proposed system is verified by simulation on the 300W cascaded boost type inverter system.

• Journal of the Korean Society for Railway
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• v.16 no.4
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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.