• Journal of Electrical Engineering and Technology
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• 제13권6호
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• pp.2301-2309
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• 2018

In a field-oriented vector-controlled permanent magnet synchronous motor (PMSM) control system, the d-axis current control loop can offer a free degree of freedom which can be used to improve control performances. However, in the industry the desired d-axis current command is usually set as zero without using the free degree of freedom. This paper proposes a method to use the degree of freedom for control performance improvement. It is assumed that both the inner loop proportional-integral (PI) current controller and the q-axis outer loop PI speed controller are tuned by the well-known tuning rules. This paper gives an optimal d-axis reference current command generator such that some useful performance indexes are minimized and/or a tradeoff between conflicting performance criteria is made. This paper uses a differential evolution algorithm to autotune the parameter values of the optimal d-axis reference current command generator. This paper implements the proposed control system in real time on a Texas Instruments TMS320F28335 floating-point DSP. This paper also gives experimental results showing the practicality and feasibility of the proposed control system, along with simulation results.

• 대한전기학회:학술대회논문집
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• 대한전기학회 2007년도 추계학술대회 논문집 전기기기 및 에너지변환시스템부문
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• pp.138-140
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• 2007

A novel non-linear logical torque sharing function (TSF) is presented. To improve efficiency and to reduce torque ripple in commutation region, only a phase torque under commutation is regulated to produce a uniform torque. And the torque developed by the other phase remains with the previous state under a current limit of the motor and drive. If the minimum change of a phase torque reference can not satisfy the total reference torque, two-phase changing mode is used. Since a phase torque is constant and the other phase torque is changed at each rotor position, total torque error can be reduced within a phase torque error limit. And the total torque error is dependent on the change of phase torque. To consider non-linear torque characteristics and to suppress a tail current at the end of commutation region, the incoming phase current is changed to torque increasing direction, but the outgoing phase current is changed to torque decreasing direction. So, the torque sharing of the outgoing phase and incoming phase can be smoothly changed with a minimum current cross over. The proposed control scheme is verified by some computer simulations and experimental results.

• Journal of Power Electronics
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• 제13권5호
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• pp.829-840
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• 2013

The modified sinusoidal pulse-width modulation (SPWM) is one of the PWM techniques used in three-phase AC-DC buck converters. The modified SPWM works without the current sensor (the converter is current sensorless), improves production of sinusoidal AC current, enables obtainment of near-unity power factor, and controls output voltage through modulation gain (ranging from 0 to 1). The main problem of the modified SPWM is the huge starting current and voltage (during transient) that results from a large step change from the reference voltage. When the load changes, the output voltage significantly drops (through switching losses and non-ideal converter elements). The single-input single-output (SISO) approach with minor-loop voltage feedback controller presented here overcomes this problem. This approach is created on a theoretical linear model and verified by discrete-model simulation on MATLAB/Simulink. The capability and effectiveness of the SISO approach in compensating start-up current/voltage and in achieving zero steady-state error were tested for transient cases with step-changed load and step-changed reference voltage for linear and non-linear loads. Tests were done to analyze the transient performance against various controller gains. An experiment prototype was also developed for verification.

• Journal of Power Electronics
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• 제16권2호
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• pp.654-665
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• 2016

The pumping of electric power from photovoltaic (PV) farms is normally carried out using transformers, which require heavy mounting structures and are thus costly, less efficient, and bulky. Therefore, transformerless schemes are developed for the injection of power into the grid. Compared with the H4 inverter topology, the H6 topology is a better choice for pumping PV power into the grid because of the reduced common mode current. This paper presents how the perturb and observe (P&O) algorithm for maximum power point tracking (MPPT) can be implemented in the H6 inverter topology along with the improved sinusoidal current injected to the grid at unity power factor with the average current mode control technique. On the basis of the P&O MPPT algorithm, a power reference for the present insolation level is first calculated. Maintaining this power reference and referring to the AC sine wave of bus bars, a sinusoidal current at unity power factor is injected to the grid. The proportional integral (PI) controller and fuzzy logic controller (FLC) are designed and implemented. The FLC outperforms the PI controller in terms of conversion efficiency and injected power quality. A simulation in the MATLAB/SIMULINK environment is carried out. An experimental prototype is built to validate the proposed idea. The dynamic and steady-state performances of the FLC controller are found to be better than those of the PI controller. The results are presented in this paper.

• 대한전기학회논문지:전기기기및에너지변환시스템부문B
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• 제49권7호
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• pp.500-508
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• 2000

Basic design for single-phase active power filter, which aims at railway application provided with PWM-controlled converters, is comprehensively studied and its performance is presented in this paper. Active power filters are used to compensate railway signaling and public telecommunication interference due to the high-order harmonic currents generated in railway traction locomotives. A type of hybrid digital filter which is composed of low pass filter and high pass filter is proposed so that the desired harmonic reference current with accurate magnitude and phase shift can be extracted from catenary line current. A design criteria to determine input inductor L and output capacitor C is also described, considering voltage, current, PWM pattern, and switching frequency of the main converters. Finally, computer simulation and DSP-based experiments resulted from laboratory test are presented.

• 한국문헌정보학회지
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• 제21권
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• pp.141-168
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• 1991

The Purpose of this study is to explore and analyse ways of enhancing the effectiveness of reference service through reference evaluation. Marketing research technique combined with pre-evaluation theory was applied in this study to find out information for practice the service based on current concept of reference service. Aims and results of this study can be summarised as follows: First, the evaluation of effectiveness of reference service should be conducted for the purpose of finding out the ways of increasing user's satisfaction. Second, the policy evaluation was understood as the appropriated evaluation concept. The policy evaluation in principle coincides with reference service in sense that the satisfaction of public should have priority and hence be the criterion of the evaluation. Third, marketing research based on recently developed 'marketing concept', which concentrates all its efforts to meet user's demand and attempt to acquire the information for better marketing management of non-profit organization such as library, is examined to find out the evaluation method practically applicable to the pre-evaluation of reference service. In this study , conjoint analysis was adopted as the method of pre-evaluation about reference service. The Reference Room of the Central Library Yonsei University, was selected as the arget sample to find out the expected condition for the maximization of the user's satisfaction from the reference service. Based on this example study, the analysis indicates as the most desirable combination for reference service in terms of the user's satisfaction is following condition: the younger librarian with aimable personality who displays willingness In his/her assistance, plus as the method of reference service, sufficient and practical introduction to the reference materials available, plus immediate and satisfactory result of the service, and finally a library equipped with inter-library use system.

• 전자공학회논문지C
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• 제35C권10호
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• pp.22-29
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• 1998

본 논문에서는 휴대용 영상신호처리 시스템에 집적화할 수 있는 전류예측기와 모듈형 기준전류원을 이용한 10비트 저전력 전류구동 CMOS A/D 변환기를 설계하였다. 전류예측기와 모듈형 기준 전류원을 사용함으로써 2단 플래시구조를 갖는 A/D 변환기에 비해 비교기와 기준전류원의 개수를 줄일 수 있게 되었고, 따라서 설계된 A/D변환기의 저전력 동작이 가능하였다. 설계된 10비트 저전력 전류구동 CMOS A/D 변환기는 0.6㎛ n-well single-poly triple metal CMOS 공정을 사용하여 제작되었다. +5V 단일 공급전압하에서 동작할 때 측정된 전력소모는 94.4mW이며, 아날로그 입력 전류범위는 16㎂에서 528㎂로 측정되었으며, INL과 DNL은 각각 ±1LSB, ±0.5LSB이하로 나타났다. 또한 10MSamples/s의 변환속도를 나타내었고, 제작된 10비트 전류구동 CMOS 4/D 변환기의 유효 칩면적은 1.8㎜ x 2.4㎜이다.

• 대한전기학회:학술대회논문집
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• 대한전기학회 1988년도 추계학술대회 논문집 학회본부
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• pp.277-280
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• 1988

In the current-controlled PWM, the actual current tracks the sinusoidal reference wave within desired hyeteresis band. This paper au99e61s the current control scheme for voltage-fed single-phase inverter and presents the simulation results. It is expected that the inverter with this control method produces no significant lower-order harmonics.

• 대한전자공학회:학술대회논문집
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• 대한전자공학회 1999년도 하계종합학술대회 논문집
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• pp.986-989
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• 1999

An 12bit current-mode folding and interpolation analog to digital converter (ADC) with multiplied folding amplifiers is proposed in this paper. A current - mode multiplied folding amplifier is employed not only to reduced the number of reference current source, but also to decrease a power dissipation within the ADC. The designed ADC fabricated by a 0.6${\mu}{\textrm}{m}$ n-well CMOS double metal/single poly process. The simulation result shows the power dissipation of 280㎽ with a power supply of 5V.

• 한국정보시스템학회지:정보시스템연구
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• 제18권2호
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• pp.35-59
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• 2009

The study of Information Systems(IS) is a relatively new discipline area, thus an analysis of the latest research literature could be useful to identify what the researchers are doing and what can be done to improve our discipline. With that purpose in mind, this study analyzes the total 208 articles published in "The Journal of Information Systems~ between 2001 and 2008. The classification system that comprises three key characteristics of diversity (research topic, research method, and reference discipline) was developed based on a review of prior literature. The results of this study were also compared with Kim et al.(2005)'s and Vessey et al.(2002)'s results to identify issues in current Information Systems research and 10 suggest some recommendations for future In formation Systems research. The findings identify popular research topic:s, the dominant research method, and reference discipline. The popular research topics consists of organizational concepts, problem domain-specific concepts, and systems/software management concepts. Field study was characterized as the dominant research method in the papers included in the study. Information Systems itself represents the major theoretical reference of the studies. However, many papers in this study relied on a number of reference disciplines., none of which was dominant, or they did not rely on a specific reference discipline. Finally, this study suggests more research on the disciplinary issues, more training on the research method, more accurate and specific reference discipline, and controlled diversity.