• Proceedings of the KIEE Conference
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• 2011.07a
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• pp.764-765
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• 2011

전력시스템을 더 효율적으로 운용하고, 더 지능화하려는 노력은 2000년대 초 다양한 각도로 진행되어 왔다. 그리하여 중장기 국책과제인 전력IT 과제를 필두로 여러 지능화 기기들이 국 내외 유관업체를 통하여 지속적으로 성장을 하였고 현재에 이르러서는 과제의 틀이 아닌 비즈니스 모델 창출을 위하여 여러 시범 사업들이 구상되고 있는 중이다. 이는 전력IT 의 핵심 아이템이라 할 수 있는 IEC-61850 국제 표준 프로토콜 기반의 IED (Intelligent Electronic Devices) 개발과 어울려 변전소의 직접 현장 적용을 통한 엔지니어링 기술 개발에 역점을 두고 있는 상태이다. 변전소 자동화 (S/A: Substation Automation)의 영역이 점점 현실화 되어가고, 전 세계 적용 Site의 폭발적인 증가로 힘입어 이젠 선택이 아닌 필수가 되고 있고, 적용에서 끝이 아닌 다양한 엔지니어링 Tool 의 개발, 진단 시스템의 융합 등과 더불어 계속 발전해나가고 있다. 본 논문에서는 이러한 시대적 흐름을 바탕으로 당사에서 참여중인 한국전력 154kV S/A 시범사업 및 스마트그리드 실증사업을 통하여 현장 적용된 154kV Main Transformer 용 IED 솔루션의 적용 사례를 소개하고자 한다. S/A 시범사업의 경우, 한국전력 충주본부 풍동S/S에서 올해 초 설계되어 현재 현장 엔지니어링을 1차 마무리한 상태이며, 스마트 그리드 실증사업은 제주 성산S/S에서 진행 중이며 이도 마무리를 하는 단계에 이르러, 그동안 현장적용의 문제점을 논의하고, 이에 대한 대응책을 서로 공유하며 정리하고 있다. 참고로 본 논문에서는 IEC-61850 프로토콜 구현에 대한 것은 다루지 않으며, 다만 현장제어에 필요하고 또한 구현되어 있는 기능에 대한 전반적인 내용을 다루게 된다.

• Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
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• v.24 no.1
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• pp.98-104
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• 2010

In order to evaluate the performance of a grounding system against lightning or fault currents including high frequency components, the grounding impedance should be considered rather than the steady state ground resistance. To evaluate the ground impedance, the frequency dependence of resistivity and relative dielectric constant of the soil have to be analyzed. This paper deals with the frequency dependence of the resistivity and relative dielectric constant of three types of soil on water content. As a result, the resistivity of soil is getting lower with increasing of water content. It is nearly independent of the frequency in the range less than 1[MHz], and is decreased over the frequency range above 1[MHz]. On the other hand, the relative dielectric constant is rapidly decreased with the frequency in the range less than 1[MHz], but it is nearly independent on the frequency over the range of 1[MHz]. It was found from the experiments that the frequency-dependant resistivity and relative dielectric constant of soil should be considered when designing the grounding systems for protection from lightning or switching surges.

• Journal of IKEEE
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• v.8 no.1 s.14
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• pp.145-151
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• 2004

For wide-band spread spectrum communication systems such as IMT-2000, a digital matched filter is a key device for rapid spreading code synchronization. Although a digital matched filter can be implemented easily, large power consumption at the higher chip rate and large summation delay of longer chip length are the bottleneck of practical use. In this paper, we propose a optimized partial correlation digital matched filter structure which can be constructed of the so-called generalized hierarchical Golay sequence. a partial correlation structure can reduce the number of correlators, but enlarge the size of flip-flops. In this paper, The proposed approach focuses on efficient circuit size, power dissipation, maintaining the operating throughput. A proposed digital matched filter reduce the size of flip-flops by rounding method. and it reduces about 45 percentages of power dissipation and chip area as compared with digital matched filter which is not rounded. rounding. The proposed architecture was verified by using Xilinx FPGA.

• Proceedings of the KIEE Conference
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• 1999.07b
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• pp.894-896
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• 1999

PID 제어는 50년의 역사를 갖기 때문에 현장의 사용자는 이 제어방식에 익숙해져 있으며, 제어장치의 구성이 간단하며 제어기의 최적동조가 가능하므로 많은 분야에서 사용되고 있다[1]. 그러나 PID 제어기에 의해서 얻은 결과에 대하여 만족하기 위해서는 많은 시행착오를 겪어야 한다. 또한 만족하는 결과를 얻었다고 할지라도 외란, 플랜트의 동특성이 바뀌는 경우 시스템을 추종하지 못하기 때문에 파라미터를 재조정하여야 한다. 유전 알고리즘은 자연세계의 진화 현상에 기초한 계산모델로서 John Holland에 의해서 1975년에 개발된 전역적인 최적화 알고리즘이며[1][2], 비선형 고차원, 불연속, 다중모드, 노이즈 함수 등에 대하여 강건함을 보여주고, 복잡한 탐색 공간에서 최적 값을 스스로 발견하는 학습 능력을 갖는다. 이 방법은 재생산, 교배, 돌연변이를 통하여 최적해를 찾은 방법으로 1989년에 D. E. Goldgerg에 의해서 체계적으로 정리된 후 여러 분야에서 응용되고 있다[3][4]. 그러나 유전 알고리즘은 목적함수만을 이용하여 해집단을 탐색하기 때문에 숙련운전자가 원하는 제어 특성 명세인 상승시간, 정착시간, 초과량(oveshoot) 둥을 구체적으로 명시하여 제어에 반영할 수 없다. 또한, 유전 알고리즘은 입력 값이 크게 바뀔 경우 다른 시스템으로 인식하여 새로운 탐색을 수행하는 단점을 가지고 있다. 본 논문은 첫째, 기준모델을 도입하여 플랜트의 성능을 기준모델로 표현하여 플랜트가 요구하는 성능지표를 정량적으로 규정하는 것이 가능하였다. 또한, 이것은 미지 플랜트 동특성을 식별하기 위한 신호로 사용되어, 플랜트의 정보를 얻는데 이용되었다. 즉, 기준모델과 플랜트 출력사이의 추종 오차 정보가 적응기구인 PID 유전제어기의 입력으로 사용되며, 구형파 입력의 경우에도 기준모델과 플랜트의 출력차는 크게 변하지 않는다. 따라서, 유전 알고리즘의 목적함수에 기준 모델을 제안 적용하여 안정적이고, 세밀한 제어를 수행하였다. 둘째, PID의 간단하면서 확실한 제어가 가능하다는 점과 전역적인 최적값을 찾을 수 있는 유전 알고리즘을 적용하여 고속제어를 요하는 직류 서보 모터(DC Servo Motor) 운전 시 실시간 파라미터 동조에 적용하였다.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.22 no.1
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• pp.37-44
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• 2021

In this study, shape design and material selection were carried out for a two-stage pressure-reducing regulator to compensate for the shortcomings of a one-stage mechanical decompression regulator. The shape of the contact surface of the depressurization unit was considered, material was selected, and the shape was designed to compensate for the pulsation and slow response through the two-stage decompression and to solve the problem of high pressure deviation. In terms of airtightness, the deformation amount of TPU showed a small amount of displacement of up to 15.82%. Considering the fact that it is applicable to various hydrogen fuel supply systems by securing universality by applying electronic solenoids to the second pressure reduction, magnetic materials were selected. The hydrogen embrittlement and corrosion resistance were evaluated to verify the plating process. Surface corrosion did not occur in only the case of Cr plating. The elongation during the corrosion process was compared using a tensile test, and there was a difference within 2%.

• The Journal of the Institute of Internet, Broadcasting and Communication
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• v.22 no.3
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• pp.49-55
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• 2022

In the next generation mobile communication systems, hybrid massive multiple-input multiple output (MIMO) can be used to highly improve an achievable rate without increasing the number of RF chains. Recently, successive-interference-cancellation (SIC) based hybrid precoder design scheme was proposed to reduce the complexity. However, since this scheme uses simple diagonal matrix for baseband precoding, it cannot solve an interference problem between the transmitted streams. Also, there is a limitation for improving the data rate because of the use of one phase shifter for analog precoding. To solve these problems, in this paper we propose a digital precoding based on the SVD of the effective channel and an analog precoding using two phase shifters. Through simulation, we show that the proposed scheme has better achievable rate and SINR performances than the conventional one.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.20 no.3
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• pp.570-575
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• 2019

Active muffler is implemented by applying active noise control technique to reduce exhaust noise of automobile muffler. Conventional Filtered_x LMS algorithm has a problem that the degree of control filter becomes very large and convergence deteriorates when acoustic feedback is present. The recursive LMS algorithm can compensate for this problem because it can be easily diverted in the adaptive filter adaptation process. In this paper, the structure of the primary path and the secondary path transfer function is designed as the IIR filter to improve the convergence performance and the computational burden, and the stabilization filter algorithm is applied to secure stability which is a disadvantage of the IIR filter structure. The stabilization filter algorithm plays a role of pulling the pole into the unit circle to prevent the pole of the transfer function corresponding to the acoustic feedback from diverging during the adaptation process. In this way, the computational burden of the active muffler system and the convergence performance can be improved. In order to show the usefulness of the proposed system, we compared the performance of the proposed Filtered_x LMS algorithm with the performance of the proposed system for the exhaust sound of a diesel engine, which is a variable environment. Compared to conventional algorithm, proposed algorithm's computational burden is less than half, and convergence performances are more than 4 times.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.19 no.4
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• pp.578-585
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• 2018

This paper proposes a design method for a 3-phase interior permanent magnet synchronous motor (IPMSM) and clamping force control method for an electro-mechanical brake (EMB) using co-simulation for a high-speed train (HST). A traditional pneumatic brake system needs much space for the compressor, brake reservoir, and air pipe. However, an EMB system uses up to 50% less space due to the use of a motor and electric wires for controlling the brake caliper. In addition, it can reduce the latency time for brake control because of the fast response and precise control. A train that has many brakes is advantageous for safety because of the control by sharing the braking force. In this paper, a driving method for a cam-shaft-type EMB is modeled. It is different from the ball-screw-type brakes that are widely used in automobiles. In addition, a co-simulation method is proposed using JMAG and Matlab/Simulink. The IPMSM was designed and analyzed with the JMAG tool, and the control system was simulated using Matlab/Simulink. The effectiveness of the co-simulation results of the mechanical clamping force and braking force was verified by comparison with the clamping force specifications of a HEMU-430X HST.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.44 no.1
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• pp.49-62
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• 2024

Reckless development of the underground by rapid urbanization causes inspection delay on replacement of existing structure and installation new facilities. However, frequent accidents occur due to deviation in construction design planned by inaccurate location information of underground structure. Meanwhile, the electrical resistivity survey, knowns as non-destructive method, is based on the difference in the electric potential of electrodes to measure the electrical resistance of ground. This method is significantly advanced with multi-electrode and deep learning for analyzing strata. However, there is no study to quantitatively assess change in electrical resistance according to geometric conditions of structures. This study evaluates changes in electrical resistance through geometric parameters of electrodes and structure. Firstly, electrical resistance numerical module is developed using generalized mesh occurring minimal errors between theoretical and numerical resistance values. Then, changes in resistances are quantitatively compared on geometric parameters including burial depth, diameter of structure, and distance electrode and structure under steady current condition. The results show that higher electrical resistance is measured for shallow depth, larger size, and proximity to the electrode. Additionally, electric potential and current density distributions are analyzed to discuss the measured electrical resistance around the terminal electrode and structure.

• KIPS Transactions on Software and Data Engineering
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• v.10 no.12
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• pp.561-568
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• 2021

In recent years, autonomous driving technologies have become a high-value-added technology that attracts attention in the fields of science and industry. For smooth Self-driving, it is necessary to accurately detect an object and estimate its movement speed in real time. CNN-based deep learning algorithms and conventional dense optical flows have a large consumption time, making it difficult to detect objects and estimate its movement speed in real time. In this paper, using a single camera image, fast object detection was performed using the YOLOv5 algorithm, a deep learning algorithm, and fast estimation of the speed of the object was performed by using a local dense optical flow modified from the existing dense optical flow based on the detected object. Based on this algorithm, we present a system that can predict the collision time and probability, and through this system, we intend to contribute to prevent tram accidents.