• Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
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• v.21 no.4
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• pp.73-79
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• 2007

In order to analyze the potential rise of grounding systems installed in buildings, a hemispherical grounding simulation system was studied. Potential rise was measured and analyzed regarding the shape and distance of the grounding electrodes by using this system. The system was composed of a hemispherical water tank, AC power supply, a movable potentiometer, and test grounding electrodes. The potential rise was measured in real time by the horizontal moving probe of be potentiometer. The test grounding electrodes were fabricated through reducing the grounding electrode installed in real buildings such as the ground rod, grounding grid and so on. The potential rise was displayed in a two-dimensional profile and was analyzed regarding the shapes of the ground electrodes. The potential rise of the grounding grid combined with a ground rod was the lowest of every grounding electrode tested. The proposed results can be applicable to evaluating ground potential rise in grounding systems, and the analytical data can be used to stabilize the electrical installations and prevent electrical disasters.

• Journal of Power Electronics
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• v.16 no.5
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• pp.1698-1705
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• 2016

In this paper, a hardware-in-the-loop simulation platform for MMCs is established, which connects a real time digital simulator (RTDS) and a designed MMC controller with optical fiber. In this platform, the converter valves are simulated with a small time step of 2.5 microsecond in the RTDS, and multicore technology is implemented for the controller so that the parallel valve control is distributed between different cores. Therefore, the designed controller can satisfy the requirements of real-time control. The functions of the designed platform and the rationality for the designed controller are verified through experimental tests. The results show that different modulation modes and various control strategies can be implemented in the simulation platform and that each control objective can been tracked accurately and with a fast dynamic response.

• Journal of Institute of Control, Robotics and Systems
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• v.22 no.10
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• pp.803-810
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• 2016

This paper presents a study of localization methods based on particle filter using 2D laser sensor measurements and road feature map information, for autonomous vehicles. In order to navigate in an urban environment, an autonomous vehicle should be able to estimate the location of the ego-vehicle with reasonable accuracy. In this study, road features such as curbs and road markings are detected to construct a grid-based feature map using 2D laser range finder measurements. Then, we describe a particle filter-based method for accurate positional estimation of the autonomous vehicle in real-time. Finally, the performance of the proposed method is verified through real road driving experiments, in comparison with accurate DGPS data as a reference.

• Journal of international Conference on Electrical Machines and Systems
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• v.1 no.1
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• pp.8-16
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• 2012

Fixed speed wind turbine generators system that uses induction generator as a wind generator has the stability problem similar to a synchronous generator. On the other hand, doubly fed induction generator (DFIG) has the flexibility to control its real and reactive powers independently while being operated in variable speed mode. This paper focuses on a scheme where IG is stabilized by using DFIG during grid fault. In that case, DFIG will be heavily stressed and a remedy should be found out to protect the frequency converter as well as to allow the independent control of real and reactive powers without loosing the synchronism. For that purpose, a crowbar protection switch or DC-link protecting device can be considered. This paper presents a comparative study between two protective schemes, a crowbar circuit connected across the rotor of the DFIG and a protective device connected in the DC-link circuit of the frequency converter. Simulation analysis by using PSCAD/EMTDC shows that both schemes could effectively protect the DFIG, but the latter scheme is superior to the former, because of less circuitry involved.

• Journal of Power Electronics
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• v.18 no.1
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• pp.204-211
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• 2018

At present, one of two LCC-HVDC systems is responsible for controlling the grid frequency of the Jeju Island Power System (JIPS). The grid voltage is regulated by using STATCOMs. However, these two objectives can be achieved in one device that is called by a modular multilevel converter-high voltage direct current (MMC-HVDC) system. Therefore, this paper proposes frequency and voltage control strategies for the JIPS based on a MMC-HVDC system. In this case, the ancillary frequency and voltage controllers are implemented into the MMC-HVDC system. The modelling of the JIPS is done based on the parameters and measured data from the real JIPS. The simulation results obtained from the PSCAD/EMTDC simulation program are confirmed by comparing them to measured data from the real JIPS. Then, the effect of the MMC-HVDC system on the JIPS will be tested in many cases of operation when the JIPS operates with and without STATCOMs. The objective is to demonstrate the effectiveness of the proposed control strategy.

• Journal of Korea Multimedia Society
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• v.10 no.2
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• pp.187-199
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• 2007

The purpose of painterly rendering is to express real painting work from input image. For expression of real pain ting impression, drawing condition is one of main element. In this paper, we propose new algorithm for using density of edges. Drawing condition of new algorithm uses color difference and density of edges. And for finding next position from current position, we used dynamic grid. We did direction interpolation for coherence direction. Also using various texture brush, we express the feel of a material effective. We show results of images rendered more realistic oil painting effect, and discuss long-term goals for more effective result.

• Progress in Superconductivity and Cryogenics
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• v.11 no.3
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• pp.35-39
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• 2009

The study for a protective relay system is one of the important technical issues on the power system application of Superconducting Fault Current Limiter (SFCL). We used Real Time Digital Simulator(RTDS) to study the true interaction of the protection system with the power system. RTDS modeling of SFCL is necessary to the detailed protective relay tests. In this paper, we developed an analysis model using RTDS for studying the transient behavior of 22.9kV SFCL and carried out closed-loop testing of protective relays in distribution power system with the developed SFCL model. The SFCL model has the operation mechanism of 22.9kV hybrid SFCL being developed by LSIS and KEPRI in Korea. The parameters of the model are based on the test data of the real SFCL. Power system planners and operators can solve the expected problems in power system application of SFCL using protective relay testing results.

• Proceedings of the KIEE Conference
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• 2004.11c
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• pp.30-32
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• 2004

With 3-D vision measuring, camera calibration is necessary to calculate parameters accurately. Camera calibration was developed widely in two categories. The first establishes reference points in space, and the second uses a grid type frame and statistical method. But, the former has difficulty to setup reference points and the latter has low accuracy. In this paper we present an algorithm for camera calibration using perspective ratio of the grid type frame with different line widths. It can easily estimate camera calibration parameters such as lens distortion, focal length, scale factor, pose, orientations, and distance. The advantage of this algorithm is that it can estimate the distance of the object. Also, the proposed camera calibration method is possible estimate distance in dynamic environment such as autonomous navigation. To validate proposed method, we set up the experiments with a frame on rotator at a distance of 1, 2, 3, 4[m] from camera and rotate the frame from -60 to 60 degrees. Both computer simulation and real data have been used to test the proposed method and very good results have been obtained. We have investigated the distance error affected by scale factor or different line widths and experimentally found an average scale factor that includes the least distance error with each image. The average scale factor tends to fluctuate with small variation and makes distance error decrease. Compared with classical methods that use stereo camera or two or three orthogonal planes, the proposed method is easy to use and flexible. It advances camera calibration one more step from static environments to real world such as autonomous land vehicle use.

• Korean Journal of Agricultural and Forest Meteorology
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• v.3 no.3
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• pp.156-162
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• 2001

In order to monitor local climatic information, twelve automated weather stations (AWS) were installed in alpine area by the Alpine Agricultural Experiment Station, Rural Development Administration (RDA), at the field of major crop located in around highland area, and collected data from 1993 to 2000. Hourly measurements of air and soil temperature (underground 10 cm,20 cm), relative humidity, wind speed and direction, precipitation, solar radiation and leaf wetness were automatically performed and the data could be collected through a public phone line. Datalogger was selected as CR10X (Campbell scientific, LTD, USA) out of consideration for sensers' compatibility, economics, endurance and conveniences. All AWS in alpine area were combined for net work and daily climatic data were analyzed in text and graphic file by program (Chumsungdae, LTD) on 1 km $\times$ 1 km grid tell basis. In this analysis system, important multi-functionalities, monitoring and analysis of local climatic information in alpine area was emphasized. The first objective was to obtain the output of a real time data from AWS. Secondly, daily climatic normals for each grid tell were calculated from geo-statistical relationships based on the climatic records of existing weather stations as well as their topographical informations. On 1 km $\times$ 1 km grid cell basis, real time climatic data from the automated weather stations and daily climatic normals were analyzed and graphed. In the future, if several simulation models were developed and connected with this system it would be possible to precisely forecast crop growth and yield or plant disease and pest by using climatic information in alpine area.

• Journal of Digital Convergence
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• v.19 no.10
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• pp.395-401
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• 2021

In the digital era, Korean universities are using real-time remote lecture platforms as a tool for learning. However, it is confusing due to low usage experience problems, and usability studies are needed. The purpose of this study is to measure, analyze, and propose gaze tracking and learning experiences according to the UI design layout of ZOOM. A total of 30 subjects were selected to conduct eye tracking and survey when learning. The experiment showed that grid layouts have a higher emotional realism and learning satisfaction than other layouts. Furthermore, it turns out that participants focused the most attention on grid layouts. Therefore, for high learning experience, grid layouts and layouts that visually highlight participants and induce communication are needed.