• Journal of the Korean Society of Industry Convergence
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• v.13 no.2
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• pp.63-68
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• 2010

Structural vibrations are among the biggest concerns in developing high resolution DVR(Digital Video Recorder) monitors. The vibrations in DVR monitors are mostly originated from the excitation sources such as the HDD and the cooling fan. In this study, the vibrations generated from the excitation sources were investigated in order to analyze the individual effect on the structural vibrations of the monitors and further to establish the design alteration to suppress the vibrations for the stability of the structure and for the better quality of the screen. The result shows that relatively simple design alterations can improve the stability of the structure substantially.

• Proceedings of the Korean Information Science Society Conference
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• 2002.10c
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• pp.397-399
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• 2002

최근 무인 감시 시스템 분야에서 리눅스 기반 DVR(Digital Video Recording)시스템의 사용이 늘어나고 있다. DVR시스템은 기존의 아날로그 비디오영상 기록을 대체하여, 카메라에서 입력받은 아날로그 신호를 디지털화(MPEG또는 MJPEG)된 영상을 하드디스크에 저장하는 방법으로 작동하는 주기적으로 빈번한 하드디스크의 쓰기 작업을 수행한다. 또 기록되는 내용의 특성상 높은 신뢰도가 요구된다. 따라서 저장장치의 신뢰도가 중요하며, 만일의 사태에 발생할 수 있는 시스템 고장에도 저장된 정보의 손실을 최소화해야 한다. 저널링 파일시스템은 이러한 요구사항에 적합한 기능을 갖추고 있으며 최근 사용범위가 넓어지고 있다. 본 논문에서는 리눅스 시스템에서 널리 사용되는 4가지 저널링 파일시스템의 상대적인 읽기, 쓰기 및 복구 성능을 비교 평가하고 이를 바탕으로 고 신뢰도의 DVR시스템에 요구되는 적절한 저널링 파일시스템을 제안한다.

• Proceedings of the KIEE Conference
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• summer
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• pp.30-32
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• 2004

This paper describes control system design for the DH(dynamic voltage restorer) consisted of a diode rectifier and series inverter applied to 22.9kV distribution system. The DVR control system is consisted of the main two parts. One is a voltage event detector using a neural network and the other is deadbeat controller for the output voltage and current control of the DVR. A simulation model was developed for analyzing performance of the controller and the whole system. The results confirm that the DVR can restore load voltage under the fault of the distribution system.

• Journal of Electrical Engineering and Technology
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• v.11 no.6
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• pp.1645-1655
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• 2016

A Dynamic Voltage Restorer (DVR) model is proposed to eliminate the short-term voltage disturbances that occur in the grid-connected mode, the switching between grid-connected mode and the stand-alone mode of a Microgrid. The proposed DVR structure is based on a conventional cascaded H-bridge multilevel inverter (MLI) topology; a novel composite control strategy is presented, which could ensure the compensation ability of voltage sag by the DVR. Moreover, the compensation to specified order of harmonic is added to implement effects that zero-steady error compensation to harmonic voltage in specified order of the presented control strategy; utilizing wind turbines-batteries units as DC energy storage components in the Microgrid, the operation cost of the DVR is reduced. When the Microgrid operates under stand-alone mode, the DVR can operate on microsource mode, which could ease the power supply from the main grid (distribution network) and consequently be favorable for energy saving and emission reduction. Simulation results validate the robustness and effective of the proposed DVR system.

• Journal of Power Electronics
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• v.16 no.1
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• pp.351-361
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• 2016

Power quality is a critical issue in distribution systems, where a dynamic voltage restorer (DVR) is commonly used to mitigate the voltage disturbances for loads. This paper deals with a nonlinear control for the three-phase four-wire (3P-4W) DVR under a grid voltage unbalance and nonlinear loads in the distribution system, where a novel control scheme based on the feedback linearization technique is proposed. Through feedback linearization, a nonlinear model of a DVR with a PWM voltage-source inverter (VSI) and LC filters is linearized. Then, the controller design of the linearized model is performed by applying the linear control theory, where the load voltages are kept constant by controlling the d-q-0 axis components of the DVR output voltages. To keep the load voltage unchanged, an in-phase compensation strategy is employed, where the load voltages are recovered to be the same as the previous voltage without a change in the magnitude. With this strategy, the performance of the DVR becomes faster and more stable even under unbalanced source voltages and nonlinear loads. The validity of the proposed control strategy has been verified by simulation and experimental results.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.15 no.4
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• pp.2363-2369
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• 2014

The DVR system supports multiple cameras and should be able to receive images at 30 frames per channel in real time. Thus, The system is using Full-HD-grade Multiplexer and Hardware compression codec. In this paper, Describing the design and implementation for the 4-channel Full-HD-grade PC-based DVR using FPGA and GPU inside CPU without Multiplexer and Hardware codec. The existing DVR system for Full-HD-grade has drawbacks to acquire images of about only 20 frames per channel in real time. The system to acquire images of multiple channel in real time was designed using FPGA. The software for the system was implemented using Intel Media SDK. At the result of performance evaluation, It was satisfied all for the required conditions. The practicality of the system was confirmed as implementation the system without using hardware compression.

• KOREAN JOURNAL OF CROP SCIENCE
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• v.36 no.2
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• pp.97-106
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• 1991

Two dimensional non-parametric model using daily mean temperature and daylength as predictor variables was established and daily developmental rates (DVR) for the period of seedling emergence to heading were estimated for 26 rice cultivars by using data from field direct seeding dates and short-day treatments experiment carried out at experimental farm of Seoul National University in 1990. Three existing parametric models were tested for the comparision of predictability with non-parametric model. The non-parametric model was found to be superior to parametric models in predicting heading date. The developmetal indice(DVI) at heading date, cummulative DVR's from seedling emergence showed 0.5 to 2.2 percent of coefficient of variations. The non-parametric model revealed errors of 0 to three days in 11 varieties when applied to data independent of those used in estimating DVR.

• The Journal of the Korea Contents Association
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• v.12 no.12
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• pp.135-145
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• 2012

This study is a research development case study on the free-standing Network based camera video recording DVR. The DVR devices till now have recorded data by converting and compressing analogue video to digital, but in the future, digital videos will be recorded directly through the network camera. Also, digital compressing methods are progressing from MPEG-4, MJPEG, to H.264 method, with products considering high definition compression efficiency, minimized data size, network compatibility, and fast pending time. According to this, in 2012, it is predicted that network camera and video devices throughout the world will outrun the current analogue devices. With this transition of technological environment and fast product pending speed, a new, quality focused design is required for product development including technical realization, reliability, high-definition, compression technology, will be essential. Manufacturers are researching a new direction for the product appearance. This study considers the actual end-users as the design target and through consumer survey on preferences, design needs and required elements necessary in the design development process are extracted. Furthermore, usability and preferred images were explored through literature study and market research. Through this research process, appropriate forms for the network based DVR were analyzed, and applied into the design development process. This product will take into consideration its competitiveness and the significance of USP(Unique Selling Proposition) which is the design supremacy and professional technical skills.

• The Transactions of the Korean Institute of Power Electronics
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• v.11 no.4
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• pp.340-348
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• 2006

This paper proposes an inrush current control technique of matching transformer for configuration of dynamic voltage restorer(DVR). The DVR system consist of PWM inverter to inject arbitrary voltage, LC low pass filter as harmonic eliminator and matching transformer for isolation. However, the matching transformer has an excess of inrush current by magnetic flux saturation in the core. Due to this inrush current, the rating of matching transformers is double for needed nominal rating for protection of DVR. Therefore, in this paper, the modeling method of magnetic flux saturation is used to analyze a magnitude of inrush current, and additional current controller is used for PWM inverter output regulation. Simulation and experimental results are provided to demonstrate the validity of the proposed control method.

• Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
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• v.27 no.2
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• pp.62-68
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• 2013

The dynamic voltage restorer (DVR) is an effective protection device for wind turbine generators based on doubly-fed induction generator (DFIG) that is operated under unbalanced voltage dip conditions. The compensating voltages of the DVR depend on the voltage dips and on the influence of the zero sequence component. The zero sequence component results in high insulation costs and asymmetry in terminal voltages. This paper proposes the use of a proportional-resonant controller in stationary reference frames for controlling zero sequence components in the DVR to protect the DFIG during unbalanced voltage dips. To enhance the proposed control method, a comparison is carried out between two cases: with and without using the control of a zero sequence component. Simulation results are presented to verify the effectiveness of the proposed control method by using the Psim simulation program.