• Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
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• v.24 no.9
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• pp.165-171
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• 2010

There are many researches on Power Quality Device to protect the critical load and power system as the nonlinear load and precision load are adopted into the power system recently. To analyze the voltage compensation of voltage sag and voltage swell by DVR, which is connected to the important load in series, this paper shows PSCAD/EMTDC simulation and its verification by comparing with the actual DVR output of 2MVA. DVR control scheme in this paper is applicable to compensate single-phase, 2-phases or 3-phases voltage sag as well as DVR for distribution system.

• The Transactions of the Korean Institute of Power Electronics
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• v.9 no.3
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• pp.275-284
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• 2004

This paper discusses how to control the compensation voltages in dynamic voltage restorers (DVR). On analyzing the power circuit of a DVR system, control limitations and control targets are presented for the voltage compensation in DVRs. Based on the preceded power stage analysis, a novel controller for the compensation voltages of DVRs is proposed by a feed forward control scheme. This paper discusses also the time delay problems in the control system of DVRs. Digitally controlled DVR systems normally have control delay at amount of one sampling time of the control system and a half of the switching period of the DVR inverter. The control delay in digital controllers increases the dimension of the system transfer function one degree higher, which makes the control system more complicate and more unstable. This paper proposes a guide line to design the control gain, appropriate output filter parameters and inverter switching frequency for DVRs with digital controllers. Proposed theory is verified by an experimental DVR system with a full digital controller.

• Journal of Institute of Control, Robotics and Systems
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• v.10 no.4
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• pp.325-333
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• 2004

It is investigated that the relation between the response time of DVR(Dynamic Voltage Restorer) and the possible compensation range of voltage dip by the DVR system which protects the 3-phase phase-controlled rectifier from voltage dip. As a result, the permissible range of voltage dip is presented in the 3-phase phase-controlled rectifier, and it is presented that the range of voltage dip which can be compensated according to the DVR s response time. when the DVR compensates voltage dip, Using the proposed method, the DVR s response time can be determined from the parameters of 3-phase phase-controlled rectifier and the possible compensation range of voltage dip, and it is possible to use the control system which have an appropriate speed. Therefore, the use of excessively fast device can be avoided, and the stability of the overall system is improved. Also the reliance of DVR about the 3-phase phase-controlled rectifier can be verified.

• 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 the Korea Academia-Industrial cooperation Society
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• v.10 no.1
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• pp.110-116
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• 2009

It is very important for a DVR system to compress mass video data because they should be able to store#playback of video data. There are several high efficient DVR products using ordinary MPEG-4 compression fur data compression. But most of them support only CIF(D1/4) image, which means degraded image quality in comparison with input image source. In this paper, M-JPEG and H.264 Codec are realized using DSP. To multiple channels system M-JPEG is used for data transmission through network, and Data compression rate is improved as about 4 times as ordinary MPEG-4 compression by supporting Baseline Profile of H.264. As a result, high resolution with the width 720 pixels and the height 480 pixels can be supported.

• The Transactions of the Korean Institute of Electrical Engineers P
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• v.57 no.3
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• pp.236-243
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• 2008

This paper analyses magnetic flux saturation of matching transformer considering characteristic of dynamic voltage restorer(DVR) system to solve voltage sags which are considered the dominant disturbances affecting power quality. This DVR consist of PWM inverter to inject arbitrary voltage, LC low pass filter and matching transformer for isolation and grid connection. However, the matching transformer has an excess of inrush current by magnetic flux saturation in the core of transformer. Due to this inrush current, the rating of matching transformers is double for needed nominal rating for protection of DVR. Therefore, in this paper, an advanced modeling method of magnetic flux saturation is used to analyze a magnitude and characteristic of magnetizing current. Simulation and experimental results considering characteristic of DVR system are provided to demonstrate the validity of the proposed analysis method.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• v.9 no.2
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• pp.1107-1111
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• 2005

The DVR system realization with watermarking and MPEG-4 for real time processing speed improvement is presented in this paper. For the real time processing the system is used the DSP processor, Quick DMA for data transmission, watermarking for security and MPEG-4 compression for facility. The algorithms are that the operational structure has the internal memory of processor, and the optimal realization is suitable to form the DSP processor structure r processed for the iterative operations. The experimental result shows the real time processing is improved 12% over for the D1 image in comparison with the other system.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.10 no.6
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• pp.1019-1024
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• 2006

A system design and realization for real time DVR system with robust video watermarking algorithm for contents security is presented in this paper. The robust video watermarking is used the intraframe space region and interframe insertion simultaneously, and to be processed at real time on image data and algorithm is used the 64bits special purpose quad DSP processor with assembly and soft pipeline codes. The experimental result shows that the processing time takes about 2.5ms in the D1 image per frame for 60% moving image.

• The Transactions of the Korean Institute of Power Electronics
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• v.10 no.2
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• pp.117-123
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• 2005

The cutoff frequency of a LC output filter for Dynamic Voltage Restorers (DVR) limits the control bandwidth of a DVR system while it attenuates the inverter switching ripples. For a selected cutoff frequency of a LC output filter, infinite number of L-C combinations is possible. Although different L-C combination has different filter characteristics, the filter design on L-C combination has been depended on field experiences without clear analysis. This paper proposes a design criterion and design examples for the L-C filter combination considering the control characteristics and the size of DVRs. An experimental DVR system based on the proposed LC output filter design methodology is built and tested.

• Journal of Power Electronics
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• v.9 no.3
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• pp.386-395
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• 2009

In this paper, a new control algorithm for the dynamic voltage restorer (DVR) is proposed to regulate the load terminal voltage during various power quality problems that include sag, swell, harmonics and unbalance in the voltage at the point of common coupling (PCC). The proposed control strategy is an Adaline (Adaptive linear element) Artificial Neural Network (ANN) and is used to control a capacitor supported DVR for power quality improvement. A capacitor supported DVR does not need any active power during steady state because the voltage injected is in quadrature with the feeder current. The control of the DVR is implemented through derived reference load terminal voltages. The proposed control strategy is validated through extensive simulation studies using the MATLAB software with its Simulink and SimPower System (SPS) toolboxes. The DVR is found suitable to support its dc bus voltage through the control under various disturbances.