• Journal of Advanced Marine Engineering and Technology
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• 제14권3호
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• pp.42-51
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• 1990

A construction method of a switching hyperplane for the Variable Structure Systems, which have robustness for parameter variations and noises in sliding mode is presented. The problem of composing a switching hyperplane is considered as a special case of the pole assignment for a closed-loop system. It is shown that the condition for constructing arbitrarily a switching hyperplane matrix C is equivalent to the controllability of the pair matrix(A, B) for the system, and then an algorithm of obtaining the switching hyperplane is proposed. It is also proved that zeros of the system are invariable in the sliding mode, and the stability for the system dynamic is equivalent to the stability of PA $\textit{ker}$ C. The applicability of the method proposed in the paper is shown by the simulation results for an example system.

• Journal of Power Electronics
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• 제15권2호
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• pp.504-517
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• 2015

This paper presents a novel switching voltage model and an offset-based pulse width modulation (PWM) scheme for multilevel inverters with unbalanced DC sources. The switching voltage model under a DC voltage imbalance will be formulated in general form for multilevel neutral-point-clamped topologies. Analysis of the reference switching voltages from active and non-active switching voltage components in abc coordinates can enable voltage implementation for an unbalanced DC-source condition. Offset voltage is introduced as an indispensable variable in the switching voltage model for multilevel voltage-source inverters. The PWM performance is controlled through the design of two offset components in a subsequence. One main offset may refer to the common mode voltage, and the other offset restricts its effect on the quality of PWM control in related DC levels. The PWM quality can be improved as the switching loss is reduced in a discontinuous PWM mode by setting the local offset, which is related to the load currents. The validity of the proposed algorithm is verified by experimental results.

• 전기학회논문지P
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• 제51권3호
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• pp.120-125
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• 2002

The switching-mode power converter has been widely used because of its features of high efficiency and small weight and size. These features are brought by the ON-OFF operation of semiconductor switching devices. However, this switching operation causes the surge and EMI(Electromagnetic Interference) which deteriorate the reliability of the converter themselves and entire electronic systems. This problem on the surge and noise is one of the most serious difficulties in AC-to-DC converter. In the switching-mode power converter, the output voltage is generally controlled by varying the duty ratio of main switch. When a converter operates in steady state, duty ratio of the converter is kept constant. So the power of switching noise is concentrated in specific frequencies. Generally, to reduce the EMI and improve the immunity of converter system, the switching frequency of converter needs to be properly modulated during a rectified line period instead of being kept constant. Random Pulse Width Modulation (RPWM) is performed by adding a random perturbation to switching instant while output-voltage regulation of converter is performed. RPWM method for reducing conducted EMI in single switch three phase discontinuous conduction mode boost converter is presented. The more white noise is injected, the more conducted EMI is reduced. But output-voltage is not sufficiently regulated. This is the reason why carrier frequency selection topology is proposed. In the case of carrier frequency selection, output-voltage of steady state and transient state is fully regulated. A RPWM control method was proposed in order to smooth the switching noise spectrum and reduce it's level. Experimental results are verified by converter operating at 300V/1kW with 5%~30% white noise input. Spectrum analysis is performed on the Phase current and the CM noise voltage. The former is measured with Current Probe and the latter is achieved with LISN, which are connected to the spectrum analyzer respectively.

• Journal of Power Electronics
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• 제9권6호
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• pp.949-959
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• 2009

This paper presents a systematic investigation of the fault-mode behaviors of matrix converter systems. Knowledge about converter behaviors after fault occurrence is important from the standpoint of reliable system design, protection and fault-tolerant control. Converter behaviors have been, in detail, examined with both qualitative and quantitative approaches for key fault types, such as switch open-circuited faults and switch short-circuited faults. Investigating the fault-mode behaviors of matrix converters reveals that converter operation with switch short-circuited faults leads to overvoltage stresses as well as overcurrent stresses on other healthy switching components. On the other hand, switch open-circuited faults only result in overvoltage to other switching components. This study can be used to predict fault-mode converter behaviors and determine additional stresses on remaining power circuit components under fault-mode operations.

• 드라이브 ㆍ 컨트롤
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• 제18권3호
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• pp.16-22
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• 2021

The variable structure controller has the characteristic that while in sliding mode, the system moves along the switching plane in the vicinity of the switching plane, so it is robust to the parameter fluctuations of the plant. However, a controller based on a variable structure may not meet the desired performance when it is commanded to track any input or exposed to disturbances. To solve this problem, a sliding mode controller based on the IVSC approach excluding an integrator is proposed in this study. The proposed sliding mode control was applied to the position control of a hydraulic cylinder piston. The sliding plane was determined by the pole placement and the control input was designed to ensure the existence of the sliding mode. The feasibility of the modeling and controller was reviewed by comparing it with a conventional proportional control through computer simulation using MATLAB software and experiment in the presence of significant plant parameter fluctuations and disturbances.

• 한국전기전자재료학회논문지
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• 제18권8호
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• pp.720-723
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• 2005

We studied the quantitativity of the image sticking which is occured by the resicual DC in the fringe-electric field switching (FFS) mode. Actually, in the FFS mode driven by the strong fringe electric field, the asymmetric residual DC was formed in the bottom substrate. It made the impurity ion stick to the alignment layer such as polyimde layer. Thus, the differnece of the luminance existes after the stress check pattern is applied to the panel so that we can see the image sticking. This image sticking decreases as the residual DC value between specific patterns decreases. Therefore, it is necessary to control the residual DC for the FFS mode with the high image quality. It is possible to eliminate the image stiking when the extra pixel voltage is applied through the circuit tunning for reducing the difference of residual DC accroding to the panel position.

• 전력전자학회논문지
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• 제8권1호
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• pp.89-97
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• 2003

PWM 인버터에 의해 구동리근 유도전동기에 발생되는 고주파 커먼 모드 전압은 전도성 EMI, 전통기 접지전류, 베어링 전류 및 다른 원치 않는 결과의 주원인이 된다. 인버터 제어의 무효벡터 스위칭 상태는 나머지 유효벡터 스위칭 상태에 비교하여 큰 커먼 모드 전압을 일으킨다. 그러므로 이 논문은 커먼 모드 전압을 완화하는 스위칭기법을 다룬다. 즉 정현파 PWM 기법을 기본으로 한 커먼 모드 전압 제거방법을 제안하였다. PWM 신호는 각자의 정현과 기준신호와 120$^{\circ}$위상차가 나는 3개의 캐리어 파형과 비교하여 발생된다. 시뮬레이션과 실험적 결과는 제안된 PWM 기법에서 커먼 모드 전압이 종래의 PWM 기법보다 약 66% 더 저감됨을 보였다.

• 한국전기전자재료학회:학술대회논문집
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• 한국전기전자재료학회 2002년도 춘계학술대회 논문집 디스플레이 광소자 분야
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• pp.136-140
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• 2002

투과형 광 시야각 모드의 하나인 Fringe Field Switching (FFS) mode를 반사형 액정 디스플레이소자로 응용하여 전기 광학적 특성을 컴퓨터 시늉 하였다. FFS mode는 액정이 수평으로 균일하게 유지되면서 구동하므로, 시야각에 따른 굴절률 변화 역시 균일하게 유지된다. 이러한 특성 때문에 반사형 FFS mode는 부가적인 위상필름을 쓰지 않고, 액정층과 편광판 1매 만으로도 일정한 수준의 반사형 디스플레이 특성을 얻을 수 있다. 컴퓨터 시늉을 통해 1매 편광판과 액정층, 반사판으로 구성된 Normally Black모드의 셀 구조를 취하고, 셀 간격을 일정하게 유지하면서 액정의 ${\Delta}n$을 변화시켜 특성을 구하는 방식으로 수행하여, 입사광의 파장이 550nm일때 최적의 셀 위상차값으로 $d{\Delta}n$인 $0.1365{\mu}m$를 얻었다. 입사광원을 $0^{\circ}C$로 하고 편광판 투과율이 41%였을 때 정면 반사율은 on시 33.6%, off시 0.14%로 명암대비가 233:1이었다. 특히 시야각은 극각 $60^{\circ}C$이내의 전 방향에서 명암 대비비가 5이상의 특성을 보였다.

• 전력전자학회논문지
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• 제9권1호
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• pp.10-16
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• 2004

본 논문에서는 공진 에너지 회생율을 최대화하여 전체적인 효율을 증가시킨 개선된 전파형 ZVT(Zero-Voltage-Transition) PWM(Pulse-Width-Modulation) DC-DC 컨버터를 소개한다. 개선된 회로는 단지 기존 컨버터의 보조스위치와 공진형 인덕터 사이에 직렬로 역공진 저지 다이오드를 추가로 달아서 모든 스위칭 소자들이 소프트 스위칭 조건에서 턴온/턴오프하여 스위칭 손실을 최소화하고, 공진 에너지를 완전히 입력으로 회귀시켜 전도손실을 절감하여 효율의 증감을 이루었다. 본 논문에서는 부스터 컨버터를 이용하여 개선된 컨버터의 동작을 분석하고, 실험결과를 바탕으로 제안된 회로의 타당성을 입증하였다.

• 한국전기전자재료학회논문지
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• 제17권11호
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• pp.1234-1240
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• 2004

We studied on the electro-optic characteristics and dynamic stability according to an undesirably defined pretilt angle induced in high step coverage of pixel area for the Twisted Nematic (TN) / Fringe-Field Switching (FFS) mode. In case of the TN mode, LC directors twist reversely near the edges of thin-film-transistor and black matrix where the pretilt angle of the LC is not well defined. Therefore, the voltage-dependent dynamics of the LC in TN mode is unstable and shows the bad electro-optic characteristics. On the other hand, in case of the FFS mode, the LCs are twisted parallel to the bottom substrate by fringe electric field and the electro-optic characteristic is not influenced by the pretilt angle of the LC which is not well defined.