• 전력전자학회:학술대회논문집
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• 전력전자학회 2010년도 하계학술대회 논문집
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• pp.216-217
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• 2010

This paper presents a new software-based on-line dead-time compensation technique for single-phase grid-connected photovoltaic (PV) inverter system. To improve the mitigation of dead-time effect around the zero-crossing point of phase current, a selective harmonic elimination of instantaneous feedback current is used as an additional part of conventional current control scheme. Simulation and experimental results are shown to verify the effectiveness of proposed compensation method in the grid-connected power distributed generation systems.

• 대한전기학회:학술대회논문집
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• 대한전기학회 1997년도 하계학술대회 논문집 B
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• pp.612-615
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• 1997

In this paper, a robust speed controller considering the effect of uncertainty (plant parameter variation. external load disturbance. unmodeled and nonlinear dynamics etc..) for induction motor is proposed. Firstly. the dynamic model at nominal case of induction motor is estimated. Based on the estimated model. the IPSC ( Integral - Proportional Speed Controller) is designed. Then a DTRC (Dead-time Robust Controller) combining DTC ( Dead-time Compensator) & SRC (Simple Robust Controller) is designed to reduce the effects of parameter variation and external disturbance. Some simulated results are provided to demonstrate the effectiveness of the proposed controller.

• 전력전자학회논문지
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• 제11권5호
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• pp.395-403
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• 2006

본 논문에서는 전압형 PWM 인버터에서의 새로운 데드 타임 보상 기법을 제안하였다. 전압형 PMW 인버터의 경우 데드 타임 영향과 스위칭 소자의 비선형적인 특성에 의해 전압 왜곡이 발생한다. 특히, 전압 왜곡은 정지 좌표계 상전류에 5차와 7차, 그리고 동기 좌표계 상전류에는 6차 고조파를 발생시킨다. 그 결과 d축 동기 PI 전류 제어기의 적분기 출력은 인버터 기본파 주파수의 6배에 해당하는 맥동을 가지고 있다. 본 논문에서는 d축 전류 제어기의 적분기 출력 신호를 데드 타임 보상을 위한 제어 신호로 사용하였다. 제안된 방법은 실험과 시뮬레이션을 통해 타당성을 검증하였다.

• 대한전기학회:학술대회논문집
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• 대한전기학회 2002년도 하계학술대회 논문집 D
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• pp.2164-2166
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• 2002

This paper present a controller design scheme for time-delay system. The Smith Predictor has been proposed to solve the problem of time-delay. But this structure has a condition that parameters of plant and model have to be matched accurately. Because of this condition, it is not applied broadly in practical industrial process field. In this paper, the 2nd-order model with dead-time is used as plant model of the Smith Predictor and a main controller is designed by using the effect of mismatch between plant and model.

• 한국초지조사료학회지
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• 제7권2호
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• pp.87-91
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• 1987

This study was carried out to investigate the effects of different cutting times at 0, 10 and 20 days after lodging on the percentage of dead plants and bare ground, live and dead matter build-up, and botanical composition of orchardgrass dominated pasture during the mid summer season. For the test, a randomized block design with 3 replications was treated with 3 different cutting times (July 17, July 27 and Aug. 6). The results obtained are summarized as follows: 1. The percentage of dead plants with cutting times at 0, 10 and 20 days after lodging was 26.3,41.7 and 46.7'%, respectively. 2. The percentage of bare ground with cutting times at 0, 10 and 20 days after lodging was 13.3,26.7 and 3 1.7%, respectively. 3. Dead matter build-up with cutting times at 0, 10 and 20 days after lodging was increased significantly with later cutting (p<0.05). The ratio of live and dead matter build-up with cutting times at 0, 10 and 20 days after lodging was 90.2:9.8, 47.7:52.3 and 39.1:60.9%, respectively. 4. Regrowth yield after lodging was decreased significantly (p<0.05) with later cutting time. 5. The percentage of legumes in botanical composition was increased greatly with later cutting time. The ratio of grasses and legumes with cutting times at 0, 10 and 20 days after lodging was 77.8:21.6,45.5: 50.3 and 36.5:61.7%, respectively.

• 한국의학물리학회지:의학물리
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• 제7권1호
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• pp.79-89
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• 1996

목적 : $^{99m}Tc$, $^{123}I$, $^{131}I$과 lucite cylindrical phantom 을 이용 갑상선 탐침 (thyroid probe)의 계수불능시간 (dead time)을 알아본 후 그의 보정방법에 대해 알아보고자 하였다. 재료 및 방법 : 갑상선 탐침과 lucite cylindrical phantom 을 사용하여 $^{99m}Tc$ 10.5mCi는 약 43시간, $^{123}I$ 2.08mCi는 약 79시간동안 2시간 간격으로, $^{131}I$ 2.06mCi 는 약 910시간 동안 6시간 간격으로 medical spectrometer를 통해 계수하였다. 이때 실제 선량과 계수곡선을 이용 계수불능시간의 영향을 받기 시작하는 지점을 측정하기 위해 매 실험시 dose calibrator를 사용하여 선량을 측정하였다. 결과 : $^{99m}Tc$ 은 모든 거리에서 약 0.80mCi, $^{123}I$은 1.00mCi 지점에서 dead time의 영향을 받기 시작했다. 20%의 계수손실이 일어나는 지점에서의 방사능세기는 이 $^{99m}Tc$의 경우는 1.29 (center), 1.28(2cm), 1.31(4cm), 1.13(6cm)mCi 이었고 $^{123}I$은 1.39mCi 이었다. 각 방사능핵종에 대한 correction factor값의 일예로 선량이 2mCi 일 때 $^{99m}Tc$의 경우는 각각 1.52 (center), 1.52(2cm), 1.50(4cm), 1.58(6cm)이였고 $^{123}I$의 경우는 1.58이었다.

• International Journal of Air-Conditioning and Refrigeration
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• 제15권3호
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• pp.129-136
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• 2007

In this paper, we suggest PI control with the Smith predictive controller to improve transient response of a variable speed refrigeration system (VSRS). As the refrigeration system has long dead time inherently, it is difficult to get fast responses of super-heat and reference temperature. We incorporated the Smith predictive controller into PI to compensate the effect of the long dead time of the system. At first, we introduced the decoupling model of the system to control capacity and superheat simultaneously and independently. Next, we designed the predictive controller of the superheat based on PI control law. Finally, the control performance by the proposed method was investigated through some numerical simulations and experiments. The results of the simulations and experiments showed that the proposed PI control with the predictive controller could obtain acceptable transient behaviour for the system.

• 한국신재생에너지학회:학술대회논문집
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• 한국신재생에너지학회 2009년도 춘계학술대회 논문집
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• pp.336-340
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• 2009

This paper presents experimental results carried out on the purge characteristic of the anodic dead-end mode fuelcell and how to improve the cell performance by pulsation effects. The dead-end mode fuelcell has some merits that a fuel supplying device is not needed and the cell power is higher than that in the open mode fuelcell. However, the purge is necessary for preventing the porous media from being flooded by liquid water formed in the channel. At this time, the un-reacted fuel is discharged with the liquid water together in purge process. The discharged fuel can make the fuel efficiency lower. Therefore, the number of purge times should be decreased for the better fuel efficiency. In this study, the outlet of the anode channel was equipped with a purge solenoid valve and a pulsation generator. The purge times was decreased when the current density decreased and operation pressure increased without the pulsation effects. In addition, when the pulsation effects such as various frequencies or amplitudes were applied, purge times was alleviated up to 40%.

• International journal of advanced smart convergence
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• 제5권1호
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• pp.34-46
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• 2016

Networked Control System (NCS) has evolved in the past decade through the advances in communication technology. The problems involved in NCS are broadly classified into two categories namely network issues due to network and control performance due to system network. The network problems are related to bandwidth allocation, scheduling and network security, and the control problems deal with stability analysis and delay compensation. Various delays with variable length occur due to sharing a common network medium. Though most delays are very less and mostly neglected, the network induced delay is significant. It occurs when sensors, actuators, and controllers exchange data packet across the communication network. Networked induced delay arises from sensor to controller and controller to actuator. This paper presents an adaptive delay compensation process for efficient control. Though Smith predictor has been commonly used as dead time compensators, it is not adaptive to match with the stochastic behavior of network characteristics. Time delay adaptive compensation gives an effective control to solve dead time, and creates a virtual environment using the plant model and computed delay which is used to compensate the effect of delay. This approach is simulated using TrueTime simulator that is a Matlab Simulink based simulator facilitates co-simulation of controller task execution in real-time kernels, network transmissions and continuous plant dynamics for NCS. The simulation result is analyzed, and it is confirmed that this control provides good performance.

• 대한전기학회:학술대회논문집
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• 대한전기학회 1999년도 추계학술대회 논문집 학회본부 B
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• pp.515-517
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• 1999

This paper considers the design of the effective controllers for the plant with an integrator and a long deadtime. The structure of the new DTC(DeadTime Compensator) that has an additive filter is proposed. Our DTC shows the improved performance in set-point response and disturbance rejection. Especially the bad effect of the long deadtime in the disturbance rejection is fairly reduced by using the additive filter. Illustrative examples are provided to show the availability of the proposed controller.