• Proceedings of the KIEE Conference
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• summer
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• pp.1254-1256
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• 2004

This paper deals with a novel 3-phase power quality disturbance generator. The proposed generator can be applied to the performance that of custom power devices. Voltage sag, swell and outage are provided by the generator. The control scheme for the disturbance generation is simple, and hardware setup is cost effective, compared with conventional scheme. The operating principle of the generator is described and the usefulness verified through simulation with 10KVA power rating.

• The Transactions of the Korean Institute of Electrical Engineers P
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• v.59 no.4
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• pp.378-383
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• 2010

Due to the large capacity and low cost, DC link electrolytic capacitors with of energy storage and voltage regulation are used for almost all types of power converter as the DC/AC inverter or DC/DC converter. Electrolytic capacitor, which is the most of the time affected by the aging effect, plays very important role for the power converter system quality and reliability. Therefore, this paper proposes a simple method to estimate the capacitance variation of an electrolytic capacitor in order to analyze the internal characteristic decrease and worn-out state of an electrolytic capacitor. Simulation results by using capacitor storage energy computation show the validity of the proposed capacitance estimation method.

• The Transactions of the Korean Institute of Electrical Engineers P
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• v.59 no.4
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• pp.372-376
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• 2010

Electrolytic capacitors have been widely used in power electronics system because of the features of large capacitance, small size, high-voltage, and low-cost. Electrolytic capacitors, which is most of the time affected by aging effect, plays a very important role for the power electronics system quality and reliability. Therefore it is important to estimate the parameter of an electrolytic capacitor to predict the failure. The estimation of the equivalent series resistance(ESR) is important parameter in life condition monitoring of electrolytic capacitor. This paper proposes a simple technique to measure the ESR of an electrolytic capacitor. This method uses a switching DC/DC boost converter to measure the DC Bus capacitor ESR of power converter. Main advantage of the proposed method is very simple in technique, consumes very little time and requires only simple instruments. Simulation results are shown to verify the performance of the proposed method.

• KSII Transactions on Internet and Information Systems (TIIS)
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• v.16 no.4
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• pp.1249-1265
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• 2022

Video streaming has become one of the most popular applications for mobile devices. The network bandwidth required for video streaming continues to exponentially increase as video quality increases and the user base grows. Multi-Path TCP (MPTCP), which allows devices to communicate simultaneously through multiple network interfaces, is one of the solutions for providing robust and reliable streaming of such high-definition video. However, mobile video streaming over MPTCP raises new concerns, e.g., power consumption and cellular data usage, since mobile device resources are constrained, and users prefer to minimize such costs. In this work, we propose a mobile video streaming framework over MPTCP (mDASH) to reduce the costs of energy and cellular data usage while preserving feasible streaming quality. Our evaluation results show that by utilizing knowledge about video behavior, mDASH can reduce energy consumption by up to around 20%, and cellular usage by 15% points, with minimal quality degradation.

• Journal of Power Electronics
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• v.17 no.1
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• pp.232-241
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• 2017

Advanced control algorithms must be used to make wind power generation truly cost effective and reliable. In this study, we develop a new and simple control scheme that employs model predictive control (MPC), which is used in permanent magnet synchronous generators and grid-connected inverters. The proposed control law is based on two points, namely, MPC-based torque-current control loop is used for the generator-side converter to reach the maximum power point of the wind turbine, and MPC-based direct power control loop is used for the grid-side converter to satisfy the grid code and help improve system stability. Moreover, a simple prediction scheme is developed for the direct-drive wind energy conversion system (WECS) to reduce the computation burden for real-time applications. A small-scale WECS laboratory prototype is built and evaluated to verify the validity of the developed control methods. Acceptable results are obtained from the real-time implementation of the proposed MPC methods for WECS.

• KSII Transactions on Internet and Information Systems (TIIS)
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• v.10 no.12
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• pp.5191-5211
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• 2016

It is essential to satisfy class-specific QoS constraints to provide broadband services for new generation networks. The present study proposes a QoS-driven multicast scheme for wireless networks in which the transmission rate and end-to-end delay are assumed to be bounded during a multiple multicast session. A distributed algorithm was used to identify a cost-efficient sub-graph between the source and destination which can satisfy QoS constraints of a multicast session. The model was then modified as to be applied for wireless networks in which satisfying interference constraints is the main challenge. A discrete power control scheme was also applied for the QoS-aware multicast model to accommodate the effect of transmission power level based on link capacity requirements. We also proposed random power allocation (RPA) and gradient power allocation (GPA) algorithms to efficient resource distribution each of which has different time complexity and optimality levels. Experimental results confirm that the proposed power allocation techniques decrease the number of unavailable links between intermediate nodes in the sub-graph and considerably increase the chance of finding an optimal solution.

• Journal of Power Electronics
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• v.15 no.3
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• pp.621-633
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• 2015

This paper proposes the analysis and design of a DC-side symmetrical zero-current-switching (ZCS) Class-D current-source driven resonant rectifier to improve the low power-factor and high line current harmonic distortion of lighting applications. An analysis of the junction capacitance effect of Class-D ZCS rectifier diodes, which has a significant impact on line current harmonic distortion, is discussed in this paper. The design procedure is based on the principle of the symmetrical Class-D ZCS rectifier, which ensures more accurate results and provides a more systematic and feasible analysis methodology. Improvement in the power quality is achieved by using the output characteristics of the DC-side Class-D ZCS rectifier, which is inserted between the front-end bridge-rectifier and the bulk-filter capacitor. By using this symmetrical topology, the conduction angle of the bridge-rectifier diode current is increased and the low line harmonic distortion and power-factor near unity were naturally achieved. The peak and ripple values of the line current are also reduced, which allows for a reduced filter-inductor volume of the electromagnetic interference (EMI) filter. In addition, low-cost standard-recovery diodes can be employed as a bridge-rectifier. The validity of the theoretical analysis is confirmed by simulation and experimental results.

• Proceedings of the Korean Society of Machine Tool Engineers Conference
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• 1997.10a
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• pp.108-113
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• 1997

In these days, customers require high-quality, high-performance, high-ride comfort for Automobile and then the automotive manufacturers concentrated on study of electrical, high-performance, low-cost of parts and sub-parts. In this paper, for ride comfort estimation PSD(Power Spectral Density) of acceleration at eight test point are measured, and then are calculated with new index of ride comfort. The new index of ride comfort developed for optimal design, real test, applied the actual. It can apply for various fields.

• Proceedings of the Safety Management and Science Conference
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• 2000.05a
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• pp.427-434
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• 2000

본 연구에서는 품질기능전개(QFD)를 품질전개, 기술전개, 원가전개, 신뢰성전개로 구분하여 각 단계에서 실무적으로 고려해야 할 중요한 사항을 제안한다. 품질전개에서는VOC로 J.D.Power사의 시장품질조사 방법을 활용할 것을 제안하며 기술전개에서는 새로운 SPC 공정도와 작업표준 작성방안을 제안한다. 끝으로 신뢰성 전개에서는 BOM의 구조분석과 RBD, FTA 통합기능분석, FMEA의 체계적인 정리 등의 3단계 전개방안을 제안한다.

• Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
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• v.22 no.5
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• pp.13-20
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• 2008

Power quality problems such as momentary interruptions and voltage sags do not great influence on loads at past. However, the interests in power quality problems increase as the use of sensitive loads with microprocessor like computers increases recently. Accordingly, power system reliability research focusing to sustained interruption and momentary interruption partially needs more accurate evaluation methods including momentary and instantaneous problems. That is, many sensitive loads being tripped by voltage sags result in interruption costs. In this paper, new reliability worth evaluation method is presented considering voltage sags. We calculated the magnitude of voltage sags using fault studies and the duration of voltage sags using the trip time of protective relays for each fault. Moreover, we includes the customer interruption cost resulted from sensitive load trip by voltage sags. Through case studies, we evaluate the effects of voltage sags for permanent faults.