• 전력전자학회논문지
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• 제22권5호
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• pp.440-448
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• 2017

This paper proposes a controller design of a distributed source inverter in stand-alone mode or grid-connected mode to compensate the current or voltage harmonics caused by local nonlinear load. The PR-based multi loop controller has been used to improve the dynamic performance of the system and to compensate the output voltage or grid current harmonics. The multi-loop controller consists of an outer current controller and an inner voltage controller for the output voltage control in stand-alone mode. In grid-connected mode, an outer current controller is added to the output voltage controller for the grid current control. The design performance of each controller is described through the Root locus and Bode plot of the transfer functions. The validity of the proposed control algorithm and design parameters has been verified through the PSiM simulation and experimental results.

• 전기학회논문지P
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• 제66권3호
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• pp.99-104
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• 2017

The three-phase four-wire power distribution system can be used to supply power to single-phase and three-phase loads at the same time. There are linear loads and nonlinear loads as single-phase loads connected to each phase. The nonlinear load generates a harmonic current during the power energy conversion process. In particular, the single-phase nonlinear load has a higher proportion of generation of the third harmonic current than the harmonics of the other orders. In a three-phase four-wire system, the third harmonic current flows through the neutral wire to the power supply side, affecting the power supply side and the line. Furthermore, the magnitude of the current flowing in the neutral line can be higher than the current flowing in the individual phase. If the neutral current is higher than the phase current, the breaker may be blocked. Therefore, it is necessary to reduce the amount of current flowing in the neutral line by harmonics. There is a method of zigzag connecting a single phase transformer by a method of reducing 3 harmonic current. In this study, the method of reducing the magnitude of the three harmonic currents flowing through the zigzag wire by comparing the polarity and the negative polarity characteristics of the single phase transformer was compared through measurement and simulation.

• Steel and Composite Structures
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• 제27권5호
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• pp.623-632
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• 2018

Performance-Based Plastic Design (PBPD) method has been recently developed to evaluate the behavior of structures in different performance levels. The PBPD method utilizes a base shear force and a lateral load pattern that are estimated based on energy and yielding mechanism concepts. Using of current lateral force pattern results in weak structural members in upper stories of a structure so that the values of the story drift in these stories are larger than the target drift, particularly in high-rise buildings. Therefore, such distribution requires modifications to overcome this drawback. This paper proposes a modified lateral load pattern for steel Eccentrically Braced Frames (EBFs) based on parametric study. In order to achieve the modified load pattern, a group of 26 EBFs has been analyzed under a set of 20 earthquake ground motions. Additionally, results of nonlinear dynamic analyses of EBFs have been post-processed by nonlinear regression analysis in order to derive the new load pattern. To prove the efficiency of present study, three EBFs as examples were designed by modified pattern and current PBPD distribution. Inelastic dynamic analyses results showed that the story drifts using modified lateral load pattern were well within the target values in comparison with current pattern in PBPD, particularly where the effect of the height is significant. The modified load pattern reduces the possibility of underdesigning in upper levels and overdesigning in lower levels of the frames.

• 조명전기설비학회논문지
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• 제25권11호
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• pp.113-122
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• 2011

This paper introduces and develops an efficient method for measuring power factor (PF) and its nature under nonlinear load current situations. The method is based on generating a pulse width modulated signal whose width correlates to the value of PF. This signal can then be employed as a feedback signal for controlling PF related power quantities in a system. This method has the advantages of its simple implementation, less computational complexity, and its allowable error of less than 4[%], which is justified by the computer simulation results.

• 전력전자학회:학술대회논문집
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• 전력전자학회 2000년도 전력전자학술대회 논문집
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• pp.339-342
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• 2000

Repetitive Load Prediction is proposed for the UPS inverter application of the second order deadbeat controller which is robust against the calculation time delay and the parameter variation and which gets fast response against the load variation. The proposed technique predicts the load current ahead of two sampling time using that the load current is periodic. This is effective under nonlinear load condition. The proposed technique is derived theoretically and verified through simulation and experimental result.

• 대한전기학회논문지:전기기기및에너지변환시스템부문B
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• 제50권12호
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• pp.601-608
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• 2001

The ever increasing density of adjustable speed drives(ASD) device with non-linear operating characteristics has been to put tremendous harmonic stress on end user's electrical application. All ASD controllers which employ solid state power devices cause harmonic currents in the source side line. This paper describes harmonic problems for use of ASD. In order to investigate the effect of harmonics caused by using of nonlinear load at the low voltage system, we fixed up simple load model and measured the voltage and current waveforms. Measurement results show that additional operation of linear load at the parallel bus with nonlinear load such as ASD is helpful to the reduction of harmonic influence.

• 전기학회논문지
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• 제57권12호
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• pp.2255-2262
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• 2008

This paper presents a design parameter calculation methodology and its realization to construction for the damped oscillatory impulse current generator(ICG) modelled as damping factor $\alpha$. Matlab internal functions, "fzero" and "polyfit" are applied to find a which are solutions of second order nonlinear equation related with three wave parameters $T_{1},T_{2}$ and $I_{os}$. The calculation results for standard impulse current waveforms such as 4/10${\mu}s$, 8/20${\mu}s$ and 30/80${\mu}s$ show very good accuracy and this results make it possible to extend to generalization in the design of damped oscillatory lCG with any capacitor. 8/20${\mu}s$ ICG based on the calculated design circuit parameters is fabricated in consideration of the nonlinear load(MOV) variation. Comparisons of the tested waveforms with the designed estimation show error within 10% for the waveform tolerance recommended in IEC 60060-1 and IEEE std. C62.45.

• 대한전기학회:학술대회논문집
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• 대한전기학회 2001년도 하계학술대회 논문집 B
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• pp.660-662
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• 2001

This paper describes the problems generated with the use of PWM ASDs with induction motors. The major effect of harmonic voltages and currents in induction motors is increased the heating due to iron and copper losses at harmonic frequencies. The harmonic components thus affect the motor efficiency and developed the torque. In order to investigate the effect of harmonics which is caused by using of nonlinear load at the low voltage system, we set up simple load system and measured the voltage and current. Measurement results show that additional operation of induction motor at the parallel bus in using nonlinear load such as ASD is helpful to the reduction of harmonic current.

• 전력전자학회논문지
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• 제3권3호
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• pp.184-190
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• 1998

대부분의 빌딩과 공장에서는 3상 4선식 저압 배전 시스템으로 전력을 공급받고 있다. 이 방식은 중성선에 전류가 흐르게 하는데 오늘날 전력 변환 기술의 개발과 컴퓨터의 보급으로 심각한 중성 전류가 발생하고 있다. 본 논문은 병렬형 3상 4선 능동 필터를 사용하여 계통의 전원 전압이 불평형이고 불평형 부하 및 비선형 부하가 접속된 상태에서 전원쪽으로 흐르는 중성 전류를 제거시키고, 전원전류의 파형을 정현파로 개선하는데 목적이 있으며, 부하 조건을 변화시키면서 시뮬레이션을 실행하여 능동 필터의 우수한 성능을 입증하였다.

• 전력전자학회논문지
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• 제13권3호
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• pp.163-170
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• 2008

본 논문에서는 DVR 등의 전력품질 개선장치들의 성능시험에 용이하게 사용하기 위하여 제안한 3상 전압변동 발생기에 대하여 선형뿐만 아니라 비선형 부하에서도 동작이 가능함을 보이는 스위칭 특성해석을 하였다. 선형 부하의 경우는 전류가 연속이므로 전압변동 발생기를 구성하는 SCR 사이리스터의 자연전류(natural commutation)가 용이하게 발생하지만, 비선형 부하의 경우는 전류 불연속 모드 동작이 발생하여 SCR 사이리스터의 원활한 스위칭이 이루어질 수 없는 경우도 있다. 따라서 비선형 부하 시 전류 불연속 구간에서의 SCR 사이리스터의 스위칭 패턴을 분석하여 전압 새그(sag), 스웰(swell), 순간정전(outage), 전압불평형(voltage unbalance) 동작이 선형에서와 동일하게 발생되는 조건을 파악하였다. 각각의 기능을 발생시키는 원리와 동작 특성을 해석하였으며 시뮬레이션과 실험을 통하여 성능을 확인하였다. 본 논문에서 다룬 전압변동 발생기는 전원 외란 발생을 낮은 비용으로 구현해 낼 수 있고 구조와 제어가 간단하여 전력품질 개선과 관련된 연구를 하는데 용이하게 활용될 것으로 기대한다.