• The Journal of Korean Association of Computer Education
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• v.11 no.1
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• pp.97-107
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• 2008

The result verification that determines correctness for the work results calculated in each PC is one of the most important issues in PC grid environments. In this literature, voting-based and trust-based schemes have been mainly used to guarantee the correctness of work results. However, these schemes suffer from both waste of resource utilization and high computation delay because they can not effectively cope with dynamic computational environments. To overcome these shortcomings, we introduce the distribution information of PC resources based on credibility and availability into result verification phase. Using this information, we propose a new result verification scheme, which can determine the correctness of work results by each PC resources' credibility and cope with the dynamic changing environments by each PC resources' availability. To demonstrate the efficiency of our result verification scheme, we evaluate the performance of our scheme from the viewpoints of turnaround time and resource utilization, utilizing resource distribution information in the Korea@Home that is a representative PC grid system in domestic. We also compare the performance of our scheme with that of other ones.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.28 no.5
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• pp.604-611
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• 2004

Simulation of three-dimensional turbulent flow with LES and DNS lakes much time and expense with currently available computing resources and requires big computing resources especially for high Reynolds number. The emerging alternative to provide the required computing power and working environment is the Grid computing technology. We developed the CFD code which carries out the parallel computing under the Grid environment. We constructed the Grid environment by connecting different PC-cluster systems located at two different institutes of Pusan National University in Busan and KISTI in Daejeon. The specification of PC-cluster located at two different institutes is not uniform. We run our parallelized computer code under the Grid environment and compared its performance with that obtained using the homogeneous computing environment. When we run our code under the Grid environment, the communication time between different computer nodes takes much larger time than the real computation time. Thus the Grid computing requires the highly fast network speed.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• 2010.10a
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• pp.240-243
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• 2010

Smart Phone supplies are diffused and substitute the Internet PC with Mobile communications which they are applied. Smart Phone in Smart Grid where electric power watch and the IT of existing amalgamate are used with business. Consequently from Smart Grid network connections which lead Smart Phone in about connection and control in about security vulnerabilities and Smart Grid networks the research is necessary in about vulnerability. It uses Smart Phone from the present paper and when approaching electric power watch systems which lead Smart Grid networks, it researches in about connection vulnerability. Also it uses Smart Phone and after connecting in Smart Grid networks a vulnerability in seizure possibility and, electric power information and control information, about private data etc. access authority it analyzes with the problem point which occurs it confronts it researches. And the research direction for a security reinforcement under presenting boil in about Smart Grid network security vulnerabilities which lead Smart Phone.

• Proceedings of the KIPE Conference
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• 2003.07b
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• pp.524-527
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• 2003

This paper describes control of the grid connected transformer-less type photovoltaic(PV) power conditioning system. which is simpler and more efficient than conventional transformer type systems. With modeling and analysis of PV system, the validity of the control strategy was verified by simulations and experimental results.

• Journal of the Korean Data and Information Science Society
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• v.17 no.2
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• pp.569-579
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• 2006

Recently, the amount of genome sequence is increasing rapidly due to advanced computational techniques and experimental tools in the biological area. Sequence comparisons are very useful operations to predict the functions of the genes or proteins. However, it takes too much time to compare long sequence data and there are many research results for fast sequence comparisons. In this paper, we propose a hybrid grid system to improve the performance of the sequence comparisons based on the LanLinux system. Compared with conventional approaches, hybrid grid is easy to construct, maintain, and manage because there is no need to install SWs for every node. As a real experiment, we constructed an orthologous database for 89 prokaryotes just in a week under hybrid grid; note that it requires 33 weeks on a single computer.

• The KIPS Transactions:PartA
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• v.8A no.3
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• pp.269-278
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• 2001

Routing region modeling method of auto_routing systems are use the grid and the non-grid type. Though grid type has a few electrical and physical element on PCB, grid type has disadvantage which decrease the auto-routing speed dur to constraint with board and gird size. Thus it increase the memory capacity, Non-grid type(Shape baed type) use the region processing type, so it has 44.2% memory decrease effect than grid type in routing region. Thus, via number has 55% decrease effect, total routing time is increased 83.8% than conventional PCB system. In this paper we developed high speed PCB auto-routing system without memory waste by using shaped type applicant with auction algorithm which reaching the destination from one-point with best speed and solving the path problem. Also, this system developed by Visual C++ in IBM Pentium computer Window environment, and compatible with other PC.

• Proceedings of the KIEE Conference
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• summer
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• pp.1471-1473
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• 2004

Maximum power point tracking(MPPT) is used in photovoltaic(PV) systems to maximize the photovoltaic array output power, irrespective of the temperature and irradiation conditions. The object of this paper is to compare and analyze MPPT efficiency for different MPPT techniques by changing irradiance. Also, this paper introduces transformerless grid-connected inverter. Simple flow charts and characteristics of each MPPT algorithm are shown. The implementation of transformerless grid-connected inveter system was based on a digital signal processor(DSP). Simulation was carried out for each MPPT method.

• Proceedings of the KIEE Conference
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• 2009.07a
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• pp.1053_1054
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• 2009

A significant number of renewable energy systems have been connected to the grids as supplement power source. The renewable energy systems require control algorithm to maintain the power-supply reliability and quality. This paper proposes a novel control algorithm for smart Power Conditioning System (PCS) with harmonics and reactive power compensation. The smart PCS is used to feed Photovoltaic (PV) power to utility and compensate harmonics and reactive power at the same time. The experimentation is carried out on the proposed grid-connected PV generation system, and controlled by digital signal processor. The grid-connected PV generation system injects PV energy into the grid and performs as Active Filter (AF) and Static Synchronous Compensator (STATCOM) without additional devices. The experiment results show that the proposed control algorithm is effective for smart PCS with harmonics and reactive power compensation.

• Journal of the Korean Institute of Gas
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• v.22 no.5
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• pp.124-132
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• 2018

The supply of renewable energy has become more vigorous due to Paris Agreement. In Korea, supply policies of renewable energy is being promoted with priority given to public buildings, so, the supply of fuel cell system that are relatively easy to install in buildings is expected to expand, so it is important that study on anti-islanding evaluation of grid-connected power conditioning system(PCS) for fuel cell. In this study, we consider that KGS AB934 PC53 in domestic certification standard of PCS for fuel cell correspond with abroad standard and analyze anti-islanding evaluation that important safety performance when connected grid. Additionally, we constructed a prototype for anti-islanding evaluation of PCS for fuel cell connected in parallel and carried out the demonstration evaluation, so, we have conducted ways that ensure safety performance in accordance with the circumstances where several fuel cell systems are installed.

• Proceedings of the KIEE Conference
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• 2006.07b
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• pp.1159-1160
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• 2006

As the grid-connected photovoltaic power conditioning systems (PVPCS) are installed in many residential areas, this has raised potential problems of network protection on electrical power system. One of the numerous problems is an Island phenomenon. There has been an argument that because the probability of islanding is extremely low it may be a non-issue in practice. However, there are three counter-arguments: First, the low probability of islanding is based on the assumption of 100% power matching between the PVPCS and the islanded local loads. In fact, an island can be easily formed even without 100% power matching (the power mismatch could be up to 30% if only traditional protections are used, e.g. under/over voltage/frequency). The 30% power-mismatch condition will drastically increase the islanding probability. Second, even with a larger power mismatch, the time for voltage or frequency to deviate sufficient to cause a trip, plus the time required to execute the trip (particularly if conventional switchgear is required to operate), can easily be greater than the typical re-close time on the distribution circuit. And, third, the low-probability argument is based on the study of PVPCS. Especially, if the output power of PVPCS equals to power consumption of local loads, it is very difficult for the PVPCS to sustain the voltage and frequency in an island. Unintentional islanding of PVPCS may result in power-quality issues, interference to grid-protection devices, equipment damage, and even personnel safety hazards. So the verification of anti-islanding performance is strongly needed. In this paper, the authors propose the improved RPV method through considering power quality and anti-islanding capacity of grid-connected three-phase PVPCS in IEEE Std 1547 ("Standard for Interconnecting Distributed Resources to Electric Power Systems"). And the simulation and experimental results are verified.