• Proceedings of the KIEE Conference
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• 1998.07f
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• pp.2048-2050
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• 1998

An uninterruptible power supply(UPS) with parallel operation is used to increase the power capacity of the system or to secure higher reliability at critical loads. In the parallel operating system composed of the multiple UPSs, load-sharing, i.e. current balance control between them is key technique. Because of its low impedance and quick response characteristics, inverter output current changes very rapidly and thereby easily researches an overload condition. The difference between total load current divided by number of operating inverters and its own current is detected as unbalanced current. Then frequency and voltage are controlled to minimize the active component and the reactive component. A good performance of the proposed load-sharing technique is verified by experiments in the parallel operating system with two 40kVA UPSs.

• Journal of Korea Port Economic Association
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• v.23 no.1
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• pp.75-93
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• 2007

It is recent trend that every countries are opening their border in the name of liberalization of contemporary era. Shipping is not exceptional and it used to be said as international business. Therefore, co-operation and openness of maritime sectors between regional countries is required to utilize resources that each countries can manage. It can be done by employing their vessels in other countries' short sea area. However, there are some problems to implement this practices, here cabotage is centre of issue. Each countries do not open their sea in order to protect their national interests in sovereignty. But, it should be opened if co-operation between each countries work well and properly. To achieve true maritime co-operation, countries as Korea, China and Japan in Northeast Asia region should have understanding for the opening of cabotage. In order to make things work well, it can be done by the lessons from EU and American cases. Therefore, it should be clarified such as market scale to provide cabotage trade, employment as well as interested parties, and technical safety matters as well as environmental standards. Then cabotage matters can be smoothly resolved between three countries in Northeast Asia region.

• Journal of Welding and Joining
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• v.28 no.1
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• pp.41-46
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• 2010

The low alloy-steel material(1.0Cr-0.5Mo, SA213T12), which has widely been used for the waterwall tube in the conventional power plant, do not have enough creep rupture strength for waterwall tubes of the Ultra-supercritical(USC) boilers. According to this reason, the high-strength low alloy-steel(2.25Cr-1.0Mo, SA213T22) has newly been adopted for the waterwall tube in the USC boilers. This paper presents failure analysis on weld-joint of the waterwall tubes in USC boilers. Visual inspections were performed to find out the characteristics of the fracture. Additionally both microscopic characteristics and hardness test were carried out on failed tube samples. Failures seem to happen mainly because the welding process has not been conducted strictly.(preheating, P.W.H.T and so forth). Thus, this paper has the purpose to describe the main cause of the poor welding process and to explain how to prevent similar failures in those weld-joints.

• The Transactions of the Korean Institute of Electrical Engineers A
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• v.50 no.6
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• pp.265-274
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• 2001

Recently, the operation of power systems has become more difficult because the peak demand load is increasing continuously and the daily load factor is getting worse and worse. Also, the consideration of deregulation and global environment in electric power industry is required. In order to overcome those problems, a study on the planning and operation in power systems of dispersed generating sources such as fuel cell systems, photovoltaic systems and wind power systems, has been performed energetically. This paper presents a method for determining an optimal operation strategy of dispersed co-generating sources, especially fuel cell generation systems, considering thermal supply as well as electric power supply. In other words, the optimal operation of those sources can be determined easily by the principle of equal incremental fuel cost and the thermal merit of those sources can be also evaluated quantitatively through Kuhn-Tucker's optimal conditions. In additions, an priority method using the comparison of total cost at the peak load time interval is presented in order ot select the optimal locations of those sources. The validity of the proposed algorithms is demonstrated using a model system.

• Journal of Korean Society of Rural Planning
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• v.22 no.2
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• pp.1-8
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• 2016

This study is intended to prepare an revitalization plan of region where rural development project is completed through an analysis of the actual condition of facility operation and maintenance in the region where the project is completed. The results of survey of actual condition of facility operation in the region where rural development project was completed showed that the facilities were not self-sufficient in terms of operation and maintenance cost. Therefore, a prerequisite to the revitalization of region where the project is completed is to prepare an alternative plan for increasing the efficiency and applicability of currently already prepared facilities. Second, a project operation organization system should be streamlined and the competency of operation personnel should continue to be strengthened. Third, it is necessary to prepare a support system and establish cooperation networks for increasing the extensibility of project and continuing to induce community revitalization in the region where the project is completed in the future.

• Nuclear Engineering and Technology
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• v.54 no.8
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• pp.2840-2851
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• 2022

Electric boilers (EBs) are the backup steam source for the auxiliary steam system of high-temperature gas-cooled reactor nuclear power plants. When the plant is in normal operations, the EB is always in hot standby status. However, the current hot standby operation strategy has problems of slow response, high power consumption, and long operation time. To solve these problems, this study focuses on the optimization of hot standby operations for the EB system. First, mathematical models of an electrode immersion EB and its accompanying deaerator were established. Then, a control simulation platform of the EB system was developed in MATLAB/Simulink implementing the established mathematical models and corresponding control systems. Finally, two optimization strategies for the EB hot standby operation were proposed, followed by dynamic simulations of the EB system transient from hot standby to normal operations. The results indicate that the proposed optimization strategies can significantly speed up the transient response of the EB system from hot standby to normal operations and reduce the power consumption in hot standby operations, improving the dynamic performance and economy of the system.

• Proceedings of the IEEK Conference
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• 2009.05a
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• pp.347-349
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• 2009

Air quality of indoor space environment is affected by various pollutants like as particles and chemical stuffs. The indoor air pollution affects directly the human respiration organs to cause consequently unpleasant mental status. The $CO_2$ concentration level is one of the harmful components of air pollutants. Major factor to increase the $CO_2$ concentration level is the people's breath amount in indoor. The car exhaust gas diffused from the around road also has strong affect on $CO_2$ concentration. There are some other reasons to affect the $CO_2$ concentration change, such as, real-time change of the population movement, closeness to the indoor air flow inlet window and changes in road car traffic amount. A remote monitoring system to measure environmental indoor air pollution concerning on the $CO_2$ concentration was studied and installed realized set-up model. Zigbee network configuration was applied for this system and the $CO_2$ concentration data were collected through USN network. A software program was developed to assure systematic analysis and to display real-time data on web pages. For the experimental test various condition was set up, like as, window opening, stopping air condition operation and adjusting fan heater work, etc. The analysis result showed the relation of various environmental conditions to $CO_2$ concentration changes. The causes to increase $CO_2$ concentration were experimentally defined as windows closing, the stopping air condition system, fan heater operation. To keep the $CO_2$ concentration under the legally required ppm level in public access indoor space, the developed remote measurement system will be usefully applied.

• Journal of Energy Engineering
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• v.28 no.2
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• pp.47-54
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• 2019

As absorption type heat pump for waste heat recovery is installed in combined cycle power plant for Energy Service Company, performance test is implemented to confirm the operation data on partial load. The operation data changes according to the heat pump operation on partial load are as follows. Total heat output increases, because waste heat of closed cooling water and a portion of LP steam from HRSG is supplied. But electric power output of steam turbine is reduced, because LP steam to steam turbine is reduced. And heat output from HP district heater and LP district heater is reduced, because HP turbine exhaust steam to HP district heater and LP district heater is reduced. On partial load operation, turbine output reduction is higher than the base load operation. Therefore, on partial load, heat pump should be operated in consideration of the heat output increase and electric power output reduction.

• Proceedings of the Korean Environmental Health Society Conference
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• 2002.04a
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• pp.84-90
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• 2002

In 1995 we licensed pyrolysis gas melting technology of indirect heating type (using kiln) from Siemens AG, and built its demonstration facility in 1998 at Clean-Park-East of Fukuoka City to demonstrate the technology for municipal solid waste (MSW). In 1997 we were awarded an order from Kanemura Co., Ltd. to build a pyrolysis gas melting and power generation plant, specifically for treating residue from car shredder. The latter was launched in 1998, and is currently in commercial operation. The operation of these plants have proven the following facts. (1) The system is capable for performing a stable operation with a wide variety of waste. (2) Pyrolysis is achieved steadily regardless of the variation in the quality of waste. (3) The system can be operated under low excess air ratio (1.2∼1.3). (4) The concentration of dioxins at the furnace outlet is 0.062ng-TEQ/㎥$\_$N/, and 0.002ng-TEQ/㎥$\_$N/, at the stack. (the value is corrected to dryO$_2$ 12％) (5) The purity of recovered metals exceeds 90%.

• Proceedings of the KIPE Conference
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• 2002.07a
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• pp.734-738
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• 2002

In this paper, a novel wireless parallel operation algorithm of N+1 redundant UPS system with no control interconnections is presented. The load sharing of multiple UPS modules are controlled by Q-V droop and $P-\delta$ droop algorithm. This algorithm compensates for inverter parameter variation and line impedance imbalances with wireless auto-tuning method. And to increase the reliability of transient characteristic under parallel operation, a virtual injected Impedance is proposed to decrease a circulation current between inverter modules. Simulation results are provided to prove the novel wireless algorithm.