• Journal of Electrical Engineering and Technology
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• v.13 no.1
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• pp.114-123
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• 2018

Recently, as one of the countermeasures to reduce carbon dioxide($CO_2$) for global warming problems, operation methods in micro-grid systems replacing diesel generator with renewable energy sources including wind power(WP) and photovoltaic(PV) system have been studied and presented in energetic manners. However, it is reported that some operation problems in micro-grid systems without diesel generator for carbon-free island are being occurred when large scaled WP systems are at start-up. To overcome these problems, this paper proposes an operation strategy in micro-grid systems by adapting control devices such as CVCF(constant voltage constant frequency) ESS(energy storage system) for constant frequency and voltage regulation, load control ESS for balancing demand and supply and SVC(static-var compensator) for reactive power compensation. From the simulation results based on the various operation scenarios, it is confirmed that the proposed operation strategy in micro-grid systems without diesel generators is a useful tool to perform a stable operation in micro-grid systems without diesel generator and also make a contribution to reduce carbon dioxide in micro-grid systems.

• The Transactions of the Korean Institute of Power Electronics
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• v.19 no.5
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• pp.463-469
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• 2014

This paper proposes a maximum torque operation strategy for the direct torque control of a surface-mounted permanent-magnet synchronous motor (SPMSM). The proposed method analyzes the available operation region of the stator flux of the SPMSM under voltage and current constraints. Based on this analysis, the optimal stator flux trajectory that yields the maximum torque is obtained across the entire operation region, including constant torque and constant power regions. The proposed strategy is also applicable in the flux-weakening region II operation of the SPMSM, which has no speed limit. The validity of the proposed method is verified through experiments conducted on an 800 W SPMSM drive system.

• The Transactions of the Korean Institute of Power Electronics
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• v.20 no.1
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• pp.59-64
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• 2015

This paper proposes an analysis and operation strategy of a grid-connected wind turbine system using a diode rectifier. The currents of generators are the same as that of a small wind turbine system. Therefore, the analysis of generator torque is required as opposed to an analysis of blade speed. In this paper, the appropriate MPPT control method is proposed to control generator torque. Usefulness of the proposed operation strategy is verified by simulations and experiments.

• Journal of Korean Society of Industrial and Systems Engineering
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• v.33 no.1
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• pp.24-32
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• 2010

The first full-scale u-City operation has started in Dongtan u-City. As local cities take over and operates the u-City, unexpected issues arise such as securing the budget of operating costs and self-providing the costs with business models utilizing the u-City assets. The paper presents a strategy for solving these issues. The strategy provides a foundation(infrastructure) for long-term operation models which may reduce the long-term operation costs. In order to establish the economic operating framework of u-City, suggested are some cost-reduction models based on the operating costs structure. For each model, a base framework with comparative analysis of operating costs is provided. With these models, each u-City may select a relevant model according to the characteristics of it. We hope that the framework provides the foundation for efficient and sustainable u-City operations.

• Maritime Security
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• v.1 no.1
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• pp.61-92
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• 2020

This paper attempts to examine the changes in China's naval strategy and to analyze the goal, range, and method of each strategy during the Xi Jinping's era. Since the founding of New China, the People's Liberation of Army Navy(PLAN) has made four changes in the naval strategy. Under Xi Jinping's administration, China's naval strategy is far seas operation combined with near seas active defense. Now, China's naval strateg y is shifting from a defensive to an aggressive one, increasing the proportion of offensive weapon systems and the number of state-of-the-art warships, and the scope of the naval strategy has been specified in the second island chain including the Indian Ocean. With the changes of naval strategy, the PLAN will set a new strategic goal to secure maritime dominance and implement an assertive strategy to actively respond to the intervention and intrusion of external forces. Moreover, the PLAN will also improve its sea-based deterrence force and the maneuver force to block other countries in the long-distance maritime conflict zones. The operation method of China's future naval strateg y will gradually shift from 'interdiction' to 'rapid-response.'

• Asia pacific journal of information systems
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• v.8 no.2
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• pp.161-172
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• 1998

Marketing information systems become a competitive weapon that supports firms in making decisions on the operation of marketing-related activities. However, little research regarding the operating strategy of marketing information systems has been conducted in Korea. Considering that this issue has been studied in the United States, this paper conducted a global benchmarking on the operating strategy of marketing information systems between Korean and the United States firms. The result of this global benchmarking suggests recommendations on supports from three management levels, the mix of 4P, the management of marketing, data from environment, and information sources.

• KSBB Journal
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• v.13 no.3
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• pp.259-267
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• 1998

Optimal feeding strategies in bioreactor operation of Scutellaria baicalensis G. plant cell culture were investigated to maximize the production of flavone glycosides by using a structured kinetic model which can predict culture growth and flavone glycosides synthesis in a rigorous, quantitative manner. For the production of baicalin and wogonin-7-0-GA, the strategies for glucose feeding into Scutellaria baicalensis G. plant cell culture were proposed based on the model, which are a periodic fed-batch operation with maintenance of cell viability and of specific production rate respectively, and a perfusion operation with maintenance of specific production rate for baicalin and wogonin-7-0-GA. Simulation results showed that the highest volumetric concentration of flavone glycosides was obtained in a periodic fed-batch operation with maintenance of cell viability among all the suggested strategies. In the periodic fed-batch operations, the higher volumetric production of flavone glycosides was achieved compared with that in the perfusion operation. It can be concluded that a periodic fed-batch operation with maintenance of cell viability would be the optimal and practical operating strategy of Scutellaris baicalensis G. plant cell culture for the production of flavone glycosides.

• Journal of the Korean Society of Systems Engineering
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• v.15 no.1
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• pp.25-33
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• 2019

In the plant industry, the share of equipment accounts for 45 ~ 75%, which is very high. It is a traditional plant centered on processes and reactions like petroleum and chemical plants. Renewable energy generation plants such as wind power generation and solar power generation are equipment-centric plants. Equipment-centric plants are very important not only in the EPC phase but also in the operation and management phase. The procurement of equipment for plant operation and management can be divided into make and buy. Make is a method of producing equipment itself, and buy is a method of procuring equipment from the outside. The procurement method of the equipment directly affects the plant operation and management cost. In this study, the decision making of equipment procurement method for plant operation and management is defined as 4 phase. Each phase is selection of procurement decision-making objects, technology strategy perspective, finance perspective, and production perspective. In detail, we defined selection process of procurement decision-making objects and technology strategy perspective process. We will contribute to the enhancement of the competitiveness of the plant operation and management area by carrying out researches on the process and application examples of financial and production perspectives in the future.

• Nuclear Engineering and Technology
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• v.47 no.4
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• pp.443-453
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• 2015

A hybrid safety injection tank (H-SIT) can enhance the capability of an advanced power reactor plus (APR+) during a station black out (SBO) that is accompanied by a severe accident. It may a useful alternative to an electric motor. The operations strategy of the H-SIT has to be investigated to achieve maximum utilization of its function. In this study, the master logic diagram (i.e., an analysis for identifying the differences between an H-SIT and a safety injection pump) and an accident case classification were used to determine the parameters of the H-SIT operation. The conditions that require the use of an H-SIT were determined using a decision-making process. The proper timing for using an H-SIT was also analyzed by using the Multi-dimensional Analysis of Reactor Safety (MARS) 1.3 code (Korea Atomic Energy Research Institute, Daejeon, South Korea). The operation strategy analysis indicates that a H-SIT can mitigate five types of failure: (1) failure of the safety injection pump, (2) failure of the passive auxiliary feedwater system, (3) failure of the depressurization system, (4) failure of the shutdown cooling pump (SCP), and (5) failure of the recirculation system. The results of the MARS code demonstrate that the time allowed for recovery can be extended when using an H-SIT, compared with the same situation in which an H-SIT is not used. Based on the results, the use of an H-SIT is recommended, especially after the pilot-operated safety relief valve (POSRV) is opened.

• Journal of Electrical Engineering and Technology
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• v.13 no.2
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• pp.631-636
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• 2018

This paper proposed an optimal operation strategy for a hybrid energy storage system (HESS) with a lithium-ion battery and lead-acid battery for mild hybrid electric vehicles (mild HEVs). The proposed mild HEV system is targeted to mount the electric motor and the battery to a conventional internal combustion engine vehicle. Because the proposed mild HEV includes the motor and energy storage device of small capacity, the system focuses on low system cost and small size. To overcome these limitations, it is necessary to use a lead acid battery which is used for a vehicle. Thus, it is possible to use more energy using HESS with a lithium battery and a lead storage battery. The HESS, which combines the lithium-ion battery and the secondary battery in parallel, can achieve better performance by using the two types of energy storage systems with different characteristics. However, the system requires an operation strategy because accurate and selective control of the batteries for each situation is necessary. In this paper, an optimal operation strategy is proposed considering characteristics of each energy storage system, state-of-charge (SOC), bidirectional converters, the desired output power, and driving conditions in the mild HEV system. The performance of the proposed system is evaluated through several case studies with respect to energy capacity, SOC, battery characteristic, and system efficiency.