• The Transactions of The Korean Institute of Electrical Engineers
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• v.67 no.11
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• pp.1447-1454
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• 2018

In this paper, the design of robust DSC-PLL(Delayed Signal Cancellation Phase Locked Loop) is proposed for coping with frequency variation. This method shows significant performance for detection of fundamental positive sequence component voltage when the grid voltage is polluted by grid unbalance and frequency variation. The feedback frequency estimation of DSC-PLL is tracking the drift in the phase by unbalance and frequency variation. The robust DSC PLL is to present the analysis on method and performance under frequency variations. These compensation algorithms can correct for discrepancies of changing the frequency within maximum 193[ms] and improve traditional DSC-PLL. Linear interpolation method is adopted to reduce the discretized errors in the digital implementation of the PLL. For verification of robust characteristic, PLL methods are implemented on FPGA with a discrete fixed point based. The proposed method is validated by both Matlab/Simulink and experimental results based on FPGA(XC7Z030).

• Korean Journal of Computational Design and Engineering
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• v.12 no.3
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• pp.153-162
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• 2007

In this paper, we propose a knowledge-based method for generating CNC torch path for laser cutting of the outlines of planar shapes. The proposed method consists of two main phases: laser cutting knowledge construction and CNC torch path generation using the knowledge. In the first phase, cutting experiments are conducted on various operating parameters, and then empirical data are stored and analyzed to make up the knowledge of laser cutting. With this knowledge, we can inquire what a kerf width is for specific operating parameters. In the second phase, using the knowledge of laser cutting, CNC torch path is generated for cutting the outlines of the given planar shapes. This phase is basically based on the offset generation of each outline by a sequence of arc splines, where the offset distance is the same as the half of the kerf width determined from the constructed knowledge. The proposed method based on laser cutting knowledge makes full use of arc interpolators in CNC torch path generation. The method can efficiently reduce the number of path segments while keeping the torch path within the desired accuracy.

• The Journal of the Acoustical Society of Korea
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• v.35 no.5
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• pp.368-374
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• 2016

This paper presents constructing transmitter and receiver by using a direct sequence spread spectrum techniques to DPSK (Differential Phase-Shift Keying) scheme in underwater acoustic communication. Since DPSK signal can be demodulated if the receiver knows only the phase difference between the adjacent bits, DPSK receiver structure has the advantage of being simplified. In the conventional receiver, two adjacent symbols of transmitted signal before despread are passed to the transition correlator that detects data by comparing maximum correlation outputs. At this time, the error for maximum value of the correlator output may increase because of low SNR (Signal to Noise Ratio) or high Doppler shift frequency according to the underwater channel. In this paper, we propose a method for accurate detection result using the width as well as the magnitude among outputs produced by the correlator. The performances of the proposed method was evaluated by simulation and lake trial data.

• Proceedings of the Ginseng society Conference
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• 1990.06a
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• pp.65-67
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• 1990

The sequence of ginseng peptide gene was designed and synthesized by the solid phase plasmid pUC19. Escherichia coli JM101 cells were transformed with above hybrid plasmids. Ampicillin resistant transformants were screened and identified by in situ colony hybridization and Southern blot techinques. Finally the gene sequencing was done by the Sanger dideoxy method using primer extension.

• Journal of Power Electronics
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• v.17 no.1
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• pp.262-271
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• 2017

This paper studies the performances of five typical Phase-locked Loops (PLLs) for distorted and unbalanced grid, which are the Decoupled Double Synchronous Reference Frame PLL (DDSRF-PLL), Double Second-Order Generalized Integrator PLL (DSOGI-PLL), Double Second-Order Generalized Integrator Frequency-Lock Loop (DSOGI-FLL), Double Inverse Park Transformation PLL (DIPT-PLL) and Complex Coefficient Filter based PLL (CCF-PLL). Firstly, the principles of each method are meticulously analyzed and their unified small-signal models are proposed to reveal their interior relations and design control parameters. Then the performances are compared by simulations and experiments to investigate their dynamic and steady-state performances under the conditions of a grid voltage with a negative sequence component, a voltage drop and a frequency step. Finally, the merits and drawbacks of each PLL are given. The compared results provide a guide for the application of current control, low voltage ride through (LVRT), and unintentional islanding detection.

• Journal of the Korean Institute of Telematics and Electronics A
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• v.33A no.5
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• pp.165-171
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• 1996

A noncoherent full-digital PN(pseudo noise) code acquisition/tracking loop has been presetned and implemented in FPGA for the CDMA band-limited direct-sequence spread-spectrum (DS-SS) signals. It employs a simple decimator to control of local PN code phase to lower the hardware cost, and a second order loop to enable the more accurate tracking. The proposed acquisition/tracking loop has been designed in RTL-level VHDL, synthesized into logic gates using the design analyzer of synopsys software, implemented in an ALTERA FPGA chip, and tested. The number of logic gates used in the implemented FPGA chip is around 7000. The functionality has been verified using a PC interface circuitry and a logic analyzer.

• Journal of Power Electronics
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• v.17 no.6
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• pp.1637-1649
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• 2017

This paper describes an intensive analysis of a harmonic identification algorithm in non-ideal voltages source systems. The dq-axis Fourier with a positive sequence voltage detector (DQFP) is a novel harmonic identification algorithm for active power filters. A compensating current control system based on repetitive control is presented. A design and stability analysis of the proposed current control are also given. The aim of the paper is to achieve a robustness of the harmonic identification in a distorted and unbalanced voltage source. The proposed ideas are supported by a hardware in the loop technique based on a $eZdsp^{TM}$ F28335 and the Simulink program. The obtained results are presented to demonstrate the performance of the harmonic identification and the control strategy for the active power filter in non-ideal systems.

• Journal of Korean Society of Industrial and Systems Engineering
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• v.28 no.2
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• pp.94-100
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• 2005

This paper presents the application of integrated mathematical programming approach for the design of cellular manufacturing. The proposed approach is carried out in two phases The first phase concerning exceptional elements(EEs) in cell formation and the second phase facilities layout design. This paper considers the total costs of three important costs for (1) intercellular transfer (2) machine duplication and (3) subcontracting. One of Important issue is the calculation of the number of machines considering the maximum utilization of machines and the available capacity of a machines that can be transferred between cells. Facilities layout design is considered to reflect the real field data taking in to account the operational sequence of the parts to be manufactured. The model is formulated as mixed integer programming that is employed to find the optimal solution.

• Wind and Structures
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• v.21 no.1
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• pp.41-61
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• 2015

The flutter stability of long-span suspension bridges during erection can be more problematic and more susceptible to be influenced by many factors than in the final state. As described in this paper, numerical flutter stability analyses were performed for the construction process of Zhongdu Bridge over Yangtze River using the commercial FE package ANSYS. The effect of the initial wind attack angle, the sequence of deck erection, the stiffness reduction of stiffening girders, the structural damping, and the cross cables are discussed in detail. It was found that the non-symmetrical sequence of deck erection was confirmed to be aerodynamically favourable for the deck erection of long-span suspension bridges and the best erection sequence should be investigated in the design phase. While the initial wind attack angle of $-3^{\circ}$ is advantageous for the aerodynamic stability, $+3^{\circ}$ is disadvantageous compared with the initial wind attack angle of $0^{\circ}$ during the deck erection. The stiffness reduction of the stiffening girders has a slight effect on the flutter wind speed of the suspension bridge during erection, but structural damping has a great impact on it, especially for the early erection stages.

• Proceedings of the KIEE Conference
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• 2009.07a
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• pp.932_933
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• 2009

A technology based on thyristors will be used to manufacture the super-conducting coil AC/DC converters because of the low ratio of cost over installed power compared to a design based on GTO or similar technology. But phase-controlled converter suffers from fundamental disadvantage. They inject current harmonics into the input ac mains due to their nonlinear characteristics, thereby distort the supply voltage waveform, and demand reactive power from the associated ac power system at retarded angles. To overcome this disadvantage, in the case of two series converters at the DC side, connected to the same step-down transformer, apply for the sequence control. It is the most simple and efficient way to reduce the reactive power consumption at low cost. Analytical sequence control algorithm is suggested, the validity of the proposed scheme has been verified by experimental results with the small-scaled International Thermonuclear Experimental Reactor (ITER) Power Supply to minimize reactive power consumption.