• Proceedings of the KIEE Conference
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• 2003.07a
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• pp.128-130
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• 2003

In recent years, both utilities and users have expressed their deep concerns about the quality of electric power. Expressed, voltage sag which is one of power quality disturbance is very serious power quality problem on the power system. Voltage sag is a decrease to between 0.1 and 0.9 pu in rms voltage magnitude on the power system for durations from 0.5 cycles to 1 minute. These voltage sags are usually caused by fault condition, overload, and starting of large motors. In this paper, different types of voltage sags are simulated by using EMTP. This paper describes the distinctive characteristic for various sag origins, proposes the effective technique for voltage sag detection using EMTP.

• New & Renewable Energy
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• v.5 no.3
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• pp.4-12
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• 2009

The effect of change in DFIG (doubly-fed wind power generator) rotating speed and active power on the grid was analyzed to understand the characteristics of wind power using the wind power simulator connected to the grid at Gochang Power Quality Test Center. Electric power quality improvement devices (DVR, STATCOM, SSTS) and electric power quality disturbance application devices for 22.9 kV grid are equipped at Gochang Power Quality Test Center. Induction motor and VVVF inverter were used to emulate the blade of a wind power generator, and a simulator for Cage wound induction generator and DFIG was developed. The trial line were assumed to be 20 km and 40 km in length, and variable wind speed pattern was set using wind speed data from Ducjeokdo to verify the power characteristics of the wind power generator according to rotating speed.

• Proceedings of the KIEE Conference
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• 2006.04b
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• pp.244-246
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• 2006

This paper deals with an analysis of SCR thyristor switching pattern for a power quality disturbance generator with phase jump function. The proposed generator can be applied to the performance test of custom power devices. Voltage sag, swell, outage, unbalance and phase jump after outage are provided by the generator. The phase jump operating principle of the generator is described and analysed. Especially, a proper switching of the SCR thyristors for the proposed generator is important to guarantee the system reliability. Therefore the switching patterns for the thyristors in each made were analysed.

• The Transactions of the Korean Institute of Electrical Engineers B
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• v.55 no.1
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• pp.39-46
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• 2006

PLL is a key item of power converter for power quality compensation and power flow control. This paper proposes a novel 3-phase PLL that is composed of ALC and PI controller. The operational principle was investigated through theoretical approach, and the performance was verified through computer simulations with MATLAB and experimental works with TMS320VC33 DSP board. The proposed 3-phase PLL shows accurate performance under the voltage disturbances such as sag, harmonics. phase-angle jump, and frequency change.

• Proceedings of the IEEK Conference
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• 2000.09a
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• pp.915-918
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• 2000

In this paper, we propose an efficient feature vector extraction and decision fusion methods for the automatic classification of power system disturbances. Here, FFT and WPT(wavelet packet transform) are und to extract an appropriate feature for classifying power quality disturbances with variable properties. In particular, the WPT can be utilized to develop an adaptable feature extraction algorithm using best basis selection. Furthermore. the extracted feature vectors are applied as input to the decision fusion system which combines the decisions of several classifiers having complementary performances, leading to improvement of the classification performance. Finally, the applicability of the proposed approach is demonstrated using some simulations results obtained by analyzing power quality disturbances data generated by using Matlab.

• The Transactions of The Korean Institute of Electrical Engineers
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• v.61 no.5
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• pp.657-663
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• 2012

Recently, by increasing of devices which are sensitive to power quality, the deterioration of power quality has been accelerated. For this reason, the social and economic losses are increased. So not only correct measurement and evaluation, but also countermeasure for improvement of power quality is surely necessary for both electric power supplier and consumer. In this paper, the discrimination algorithm for events and variation occurred in distribution systems using S-transform is proposed. Firstly, we review for events and variations that occur in distribution system. Next, we simulate events and variations on various conditions using ElectroMagnetic Transient Program(EMTP). For the simulation, the IEEE 13 Node Test Feeder and KEPCO's distribution system is modeled. Finally, for the analysis, a modified wavelet transform known as S-transform is adopted to find out the characteristics of each events and variations.

• The Transactions of the Korean Institute of Power Electronics
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• v.11 no.5
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• pp.463-470
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• 2006

This paper deals with a new 3-phase power quality disturbance generator. The proposed generator can provide phase jump as well as voltage sag, swell, outage, unbalance, and over and under voltage. The operating principle of the generator is described in each mode of disturbance. The magnitude of the phase jump is analysed and it is found that the magnitude is the function of the turn-ratios of the transformers consisting the generator. The scheme has simple structure compared with the conventional one, and the major components of the proposed scheme are SCR thyristor and transformer, which guarantees high reliability and cost-effective implementation of the generator. Furthermore, high efficiency can be obtained because there is no PWM switching of the semiconductor devices, and it is easy to control the system. Simulations are carried out to confirm the operation in each disturbance mode, and experiments has been done with 5kVA power rating. The usefulness of the proposed scheme is verified through simulation and experimental results. It is expected that the scheme can be applied to the performance test of the custom power devices such as UPS, DVR, DSTATCOM, and SSTS with cost-effective system.

• Proceedings of the KIEE Conference
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• 2001.07a
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• pp.276-278
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• 2001

In recent years, both electric utilities and end users have expressed their deep concerns about the quality of electric power. Especially, voltage sag which is one of power quality disturbance is very serious power quality problem on the power system. Voltage sag is a decrease to between 0.1 and 0.9 pu in rms voltage magnitude on the power system for durations from 0.5 cycles to 1 minute. These voltage sags are usually caused by fault conditions, overloads, and starting of large motors. The wavelet transform has attracted considerable attention in the field of power quality analysis recently. It has proved to be a powerful tool to study those transients that have time-localized information. In this paper, different types of voltage sags are simulated by using EMTP. This paper proposes the effective technique for voltage sag detection using wavelet transform.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.20 no.7
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• pp.1283-1289
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• 2016

Electrical energy is the essential resource for modern society. Recently, the demand for power was significantly increased. Increase of power demand has lead to a decrease in the power quality. Power quality in modern society has been an important factor that can cause a major problem throughout the home and general industry. Therefore, we need a system for preventing the power quality problems. To avoid power issues, it is important that the measurement of the power quality and initial response. In this paper, we propose real-time power quality measurement system and harmonics monitoring system. We design the system using DM240001 board include dsPIC33FJ256GP710A of microchip. This system can adapt three-phase three-wire system. And optimized the algorithm, we can measure momentary changes of the power system. In addition, designed system can measure harmonics distortion like to VTHD, ITHD and ITDD for 31th harmonics.

• Journal of Electrical Engineering and Technology
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• v.10 no.1
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• pp.92-101
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• 2015

As one type of power quality (PQ) disturbance sources, high-speed rail (HSR) can have major impacts on the power supply grid. Providing timely and accurate warning information for PQ problems of HSR is important for the safe and stable operation of traction power supply systems and the power supply grid. This study proposes a novel warning approach to identify PQ problems and provide warning prompts based on the monitored data of HSR. To embody the displacement and status change of monitored data, multi-features of different sliding windows are computed. To reflect the relative importance degree of these features in the overall evaluation, an analytic hierarchy process (AHP) is used to analyse the weights of multi-features. Finally, a multi-features similarity algorithm is applied to analyse the difference between monitored data and the reference data of HSR, and PQ warning results based on dynamic thresholds can be analysed to quantify its severity. Cases studies demonstrate that the proposed approach is effective and feasible, and it has now been applied to an actual PQ monitoring platform.