• Journal of Electrical Engineering and Technology
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• v.9 no.2
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• pp.576-588
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• 2014

The superiority of CMI (Cascaded Multilevel Inverter) is unparalleled in high power and high voltage STATCOM (Static Synchronous Compensator). However, the parameters and operating conditions of each individual power unit composing the cascaded STATCOM differ from unit to unit, causing unit voltage disequilibrium on the DC side. This phenomenon seriously impairs the operation performance of STATCOM, and thus maintaining the DC voltage balance and stability becomes critical for cascaded STATCOM. This paper analyzes the case of voltage disequilibrium, combines the operation characteristics of the cascaded STATCOM, and proposes a new DC voltage control scheme with the advantages of good control performance and stability. This hierarchical control method uses software to achieve the total active power control and also uses chopper controllers to enable that the imbalance power can flow among the capacitors in order to keep DC capacitor voltages balance. The operating principle of the chopper controllers is analyzed and the implementation is presented. The major advantages of the proposed control strategy are that the number of PI regulators has been decreased remarkably and accordingly the blindness of system design and debugging also reduces obviously. The simulation reveals that the proposed control scheme can achieve the satisfactory control goals.

• Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
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• v.12 no.4
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• pp.100-105
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• 1998

This paper proposes a new control strategy of bidirectional uninterruptible power supply (UPS) with the performance of active power filter which compensates the harmonics and reactive power. With only one power stage, it is working simultaneously as the AC/DC rectifier/battery charger and DC/AC inverter to the operation of battery charging or back-up power supplying. Therefore the operation of the proposed system can be divided into the modes, such as the active power filter mode and the battery back-up power mode. And a novel closed-loop control strategy is used to calculate the reference current. The performance of the proposed 5[kVA] system is verified by the simulation and experimental results.

• Journal of Information Technology Services
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• v.14 no.4
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• pp.15-30
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• 2015

SMBA (Small and Medium Business Administration) and TIPA (Korea Technology and Information Promotion Agency for SMEs) have operated the Business Innovation Platform for SME Informatization based on cloud computing technology with the cooperation of seven industry cooperatives since 2013. This project will evolve into the open market platform where service providers and users voluntarily participate and transact. This research conducts the literature review about the concept of open market and the empirical analysis through survey for the software providers and the future users regarding the future operation methods. The policy about how the open market strategy for the business innovation platform needs to be designed and implemented are organized as the three differentiated government support strategies. The first is to provide free IT services including specialized core operation support S/W which is developed only for the small or home office group of firms which lack minimal informatization capability and budget. The second is to augment IT platform service through incorporating ERP supplier initiated commercial S/W sales window for those firms having medium level informatization capability. This includes to provide IT support for customization and system integration with existing government subsidized S/W. The third is to provide upgrading services of existing S/W functions to facilitate better system utilization. The results provide useful insight for government role to enhance SME competitiveness using IT.

• KSII Transactions on Internet and Information Systems (TIIS)
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• v.15 no.8
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• pp.2783-2804
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• 2021

In the network function virtualization environment, dynamic changes in network traffic will lead to the dynamic changes of service function chain resource demand, which entails timely dynamic adjustment of service function chain resource configuration. At present, most researches solve this problem through virtual network function migration and link rerouting, and there exist some problems such as long service interruption time, excessive network operation cost and high penalty. This paper proposes a dynamic adjustment method of service function chain resource configuration for the dynamic changes of network traffic. First, a dynamic adjustment request of service function chain is generated according to the prediction of network traffic. Second, a dynamic adjustment strategy of service function chain resource configuration is determined according to substrate network resources. Finally, the resource configuration of a service function chain is pre-adjusted according to the dynamic adjustment strategy. Virtual network functions combination and virtual machine reusing are fully considered in this process. The experimental results show that this method can reduce the influence of service function chain resource configuration dynamic adjustment on quality of service, reduce network operation cost and improve the revenue of service providers.

• Journal of the Korean Wood Science and Technology
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• v.52 no.2
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• pp.175-190
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• 2024

The increase in atmospheric carbon dioxide concentrations is known to be closely associated with climate change and global warming. In this sense, considering that facilities for appropriate education and experience on wood, which is a carbon pool, have been required, this study targets the Wood Cultural Experience Centers, which are in current operation, examines and evaluates their operation status and policy changes, and ultimately derives a successful positioning plan. To this end, it conducts a survey, and the results are as follows. First, as a result of the similarity analysis (KYST: Kruskal-Young-Shepard-Torgerson program) with facilities with leisure activities and educational functions, the Wood Cultural Experience Center have competition with natural recreation forests in terms of naturalness, and it has competition with the career experience center and youth training center in terms of experiential observation. Second, the result of positioning analysis of the attribute space map indicates that the Wood Cultural Experience Center is positively perceived in terms of such attributes as naturalness, experiential learning or recreation, and preservation of natural environment, but is negatively recognized in terms of accessibility, escape from daily life, and things to see.

• The Transactions of the Korean Institute of Electrical Engineers A
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• v.48 no.12
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• pp.1498-1506
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• 1999

In this paper, a hybridization of Evolutionary Strategy (ES) and a Two-Phase Neural Network(TPNN) is applied to the optimal environmental and economic operation. As the evolutionary computation, ES is to search for the global optimum based on natural selection and genetics but it shows a defect of reducing the convergence rate in the latter part of search, and often does not search the exact solution. Also, neural network theory as a local search technique can be used to search a more exact solution. But it also has the defect that a solution frequently sticks to the local region. So, new algorithm is presented as hybrid methods by combining merits of two methods. The hybrid algorithm has been tested on Emission Constrained Economic Dispatch (ECED) problem and Weighted Emission Economic Dispatch (WEED) problem for optimal environmental and economic operation. The result indicated that the hybrid approach can outperform the other computational efficiency and accuracy.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.22 no.12
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• pp.873-880
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• 2010

The present study developed a computer simulation program to determine the optimum strategy and capacity of a micro combined heat and power(CHP) system. This simulation program considered a part-load electrical/thermal efficiency and transient response characteristics of CHP unit. The result obtained from the simulation was compared with the actual operation of 30 kW gas engine driven micro CHP system. It was found that the simulation could reproduce the daily operation behavior, such as operating hours and mean load factor, closely to the actual behavior of the system and could predict the amount of electrical/thermal output and fuel consumption with the error of less than 12%.

• Journal of the Korean Institute of Gas
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• v.1 no.1
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• pp.64-72
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• 1997

A strategy is proposed for the systematic synthesis of goal-tree to support the operation of abnormal situation in chemical plant. A knowledge base using the heuristics of operators is organized for synthesizing goal tree to take appropriate safety precautions with properties of accident. A computer-based system which utilizes artificial intelligence technique is developed to evaluate the effectiveness of the methodology and applied to the model plant.

• Journal of Korean Institute of Industrial Engineers
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• v.27 no.4
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• pp.384-393
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• 2001

The performance of a double carousel system depends on its design and operation strategy. The two-class based assignment policy is expected to be an appropriate storage policy for its efficient operation, since it has two independently-moved carousels, lower and upper sub-carousels. This paper conducts a comparative analysis of the effects of the two-class based assignment policy and those of randomized assignment policy on the throughput of a double carousel system. We also show that, by allowing the sub-carousels not to be equal in size, a further improvement in the throughput can be obtained.

• Proceedings of the KIEE Conference
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• 2006.10c
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• pp.357-359
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• 2006

The electric power system of Kwangyang steel works needs to keep the parallel operation with the system of KOPEC(Korea Electric Power Corporation) for supplying the power with safety. Once it is separated from KOPEC due to an accident, it operates the automatic Mill trip system to prevent huge fluctuating loads from the serious frequency drop. In spite of that, it is recent situations that the continuous growth of electric loads facilitates the frequency drop. Therefore, this paper proposes a model of generator control system so as to quantitatively analyze the response characteristics to the frequency change under the single operation, and also suggests the strategy for minimizing the frequency changes. The simulation results show it is desirable to operate the generators by 3% speed droop and 10% load limiter.