유도전동기의 공진 문제를 해결한 새로운 V/f 제어 기법

정강률 순천향대학교 산업기술연구소 2003 순천향 산업기술연구소논문집 Vol.9 No.1

.

빠른 동특성을 가지는 병렬 능동필터에 의한 무효전력 보상 기법

정강률 순천향대학교 교수학습개발센터 2005 순천향 산업기술연구소논문집 Vol.11 No.1

This paper proposes a compensation method of the reactive power by the shunt active filter with fast dynamics that can eliminate the harmonic currents included in line currents without computation of harmonic current components. A current controller with fast dynamics for an active filter is described. Harmonic currents are directly controlled without the need for sensing and computing the harmonic current of the load current, thus simplifying the control system. Current compensation is done in the time domain, allowing a fast time response. The DC voltage control loop keeps the voltage across the DC capacitor constant. High power factor control by an active filter is described. All control functions are implemented in software using a single-chip microcontroller, thus simplifying the control circuit. Any current-controlled synchronous rectifier can be used as a shunt active filter through only the simple modification of the software and the addition of current sensors. It is shown through experimental results that the proposed controller gives good performance for the shunt active filter.

회전자 자속 추정을 이용한 센서리스 유도전동기 제어

정강률 순천향대학교 부설 산업기술연구소 2004 순천향 산업기술연구소논문집 Vol.10 No.1

This paper proposes a speed-sensorless induction motor control system using a rotor flux estimation. To explain the proposed sensorless control, this paper describes and induction motor model in the synchronous reference frame for the vector control. The rotor flux is indirectly estimated by the rotor flux observer using the reduced-dimensional state estimator technique instead of directly measuring the rotor flux. The estimated rotor speed is obtained directly from the electrical frequency, the slip frequency, and the rotor speed compensation with the estimated q-axis rotor flux. To precisely estimate the rotor flus, the actual value of the stator resistance, whose actual variation is reflected, is derived. An implementation of pulse-width modulation (PWM) pulses using an effective space vector modulation (SVM) is briefly mentioned. For fast calculation and improved performance of the proposed algorithm, all control functions are implemented in software using a digital signal processor (DSP) with its environmental circuits. Also, it is shown through experimental results that the proposed system gives good performance for the speed-sensorless induction motor control.

유도전동기의 공진 문제를 해결한 V/f 제어 기법

정강률 순천향대학교 부설 산업기술연구소 2003 순천향 산업기술연구소논문집 Vol.9 No.1

This paper proposes the novel V/f control method to improve the stability of a V/f controlled induction motor drive system. The novel conventional V/f control method used in the proposed novel V/f control method is a vector-based method that is slightly different from the conventional V/f control method. The proposed control method uses a dynamic current compensator to improve the stability of a V/f controlled induction motor drive system. This novel method is easy to implement and completely eliminates the motor oscillation phenomenon causing the instability of a V/f controlled induction motor drive system. Additionally, this paper analyzes theoretically the instability of a V/f controlled induction motor drive system and shows the validity of the proposed V/f control method through simulation and experimental results.

전자 상거래를 위한 공개키 기반 구조 제시

이강석,염흥열 순천향대학교 부설 산업기술연구소 1998 순천향 산업기술연구소논문집 Vol.4 No.1

As the business of electronic commerce(EC) through Internet spreads widely and rapidly, both the government and the enterprise are faced with new problem, which is the privacy protection in Internet. They make efforts to solve this problem. In electronic commercial transactions one party can't trust the other party of transaction, because he can't see them directly. Generally, EC is based on the trust to the other party. But, the trust infrastructure of EC have not yet established. Furthermore, there are so many problems to be solved, which restrict the governments and international transaction. And, these problems are how to deal with the intellectual property rights, how to provide the information privacy, and which cryptographic algorithms to be used. The unique solution to these problems is to introduce the cryptographic technologies to EC, to establish the Public Key Infrastructure(PKI), and then to apply it for the creation of new security service. That is, we need the interoperable PKI policies and the establishment of international standards for EC. In this paper, we present the basic structure of PKI, requirements for PKI, and the components in PKI, and new PKI applications. Also, we present the security algorithms and components for establishing the PKI.

조광제어 기능을 가진 냉음극형형광램프 안정기

이재민,정강률 순천향대학교 산업기술연구소 2007 순천향 산업기술연구소논문집 Vol.13 No.1

.

새로운 동기정류기 이용한 고효율 하프브리지 DC-DC 컨버터

유두희,정강률 순천향대학교 부설 산업기술연구소 2007 순천향 산업기술연구소논문집 Vol.13 No.1

This paper presents a high efficiency half-bridge dc-dc converter using a novel synchronous rectifier. After conventional self-driven synchronous rectifier technique applied to each conventional converter is briefly reviewed, the new topological self-driven synchronous rectifier applied to the proposed converter is briefly described. The new topological synchronous rectifier increases the system efficiency using low on-resistance of its switches and its switch conduction time extension to the whole switching period, which is one of the characteristics of the asymmetrical half-bridge converter. The synchronous rectifier type used in the proposed converter is a little modified type of the conventional synchronous rectifier used in the conventional asymmetrical half-bridge converter, which changes the transformer structure and synchronous rectifier switch connection. The operational principle of the proposed half-bridge dc-dc converter is explained, and according to this, a design consideration is shown. As the proposed converter utilizes the transformer leakage inductance as the resonant inductance, its structure is more simplified. The circuit operation and mathematical analysis of the proposed converter are given in detail. Also it is shown through the experimental results that the proposed converter operates excellently as a high efficiency converter.

입원 중인 베트남 참전 군인의 삶의 만족도와 관련된 요인

김애리,박종,김율,노희송,박광희,김은숙,김형철,홍강식,류소연,강명근,김기순 朝鮮大學校 附設 醫學硏究所 2007 The Medical Journal of Chosun University Vol.32 No.2

Background and Objectives: The aim of the study was to identify the factors associated with life satisfaction of hospitalized Vietnam veterans. Material and Methods: The data were collected from 200 hospitalized Vietnam veterans of 5 veterans hospitals in Korea from September 13 to 23, 2004. Information of general characteristics, health behavior, disease history, family function, depression and life satisfaction were collected by structured questionnaire. Results: The mean of life satisfaction was 21.48(±6.03), and the mean of depression was 53.10(±9.64). The prevalence of depression was mild depression 24.0%, moderate depression 43.5% and severe depression 25.0%. Depression was associated with life satisfaction and depression was higher, life satisfaction was lower. Family function and age were positively associated with life satisfaction, Conclusion: Life satisfaction was affected by depression and family function in hospitalized Vietnam veterans. Therefore, it was thought that psychosocial approaches such as improve depression and family function in care of hospitalized Vietnam veterans is required.

Improved Single-Stage AC-DC LED-Drive Flyback Converter using the Transformer-Coupled Lossless Snubber

Gang-Youl Jeong,Su-Han Kwon 대한전기학회 2016 Journal of Electrical Engineering & Technology Vol.11 No.3

This paper presents an improved single-stage ac-dc LED-drive flyback converter using the transformer-coupled lossless (TCL) snubber. The proposed converter is derived from the integration of a full-bridge diode rectifier and a conventional flyback converter with a simple TCL snubber. The TCL snubber circuit is composed of only two diodes, a capacitor, and a transformer-coupled auxiliary winding. The TCL snubber limits the surge voltage of the switch and regenerates the energy stored in the leakage inductance of the transformer. Also, the switch of the proposed converter is turned on at a minimum voltage using a formed resonant circuit. Thus, the proposed converter achieves high efficiency. The proposed converter utilizes only one general power factor correction (PFC) control IC as its controller and performs both PFC and output power regulation, simultaneously. Therefore, the proposed converter provides a simple structure and an economic implementation and achieves a high power factor without the need for any separate PFC circuit. In this paper, the operational principle of the proposed converter is explained in detail and the design guideline of the proposed converter is briefly shown. Experimental results for a 40-W prototype are shown to validate the performance of the proposed converter.

Simple High Efficiency Full-Bridge DC-DC Converter using a Series Resonant Capacitor

Gang-Youl Jeong,Su-Han Kwon,Geun-Yong Park 대한전기학회 2016 Journal of Electrical Engineering & Technology Vol.11 No.1

This paper presents a simple high efficiency full-bridge DC-DC converter using a series resonant capacitor. The proposed converter achieves the zero voltage switching of the primary switches under a wide range of load conditions and reduces the high circulating current in the freewheeling mode using the leakage resonant inductance and the series resonant capacitor. Thus, the proposed converter overcomes the drawbacks of the conventional full-bridge DC-DC converter and improves its overall system efficiency. Its structure is simplified by using the leakage inductance of the transformer as the resonant inductance and omitting the DC output filter inductance. Also it can operate over a wide range of input voltages. In this paper, the operational principle, analysis and design example are described in detail. Finally, the experimental results from a 650W (24V/27A) prototype are demonstrated to confirm the operation, validity and features of the proposed converter.