• Proceedings of the Korean Institute of IIIuminating and Electrical Installation Engineers Conference
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• 2008.10a
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• pp.57-60
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• 2008

As the technology of a large scale battery have advanced, it's application to the electric power network have been active in foreign country. By providing the electric power energy stored in the electric power storage system when needed, there are many advantages that it is able to reduce the gap between the electric power demand and supply for day and night to increase capacity factor, to upgrade the electric power quality degraded from the unbalance between power demand and supply and to compensate the fluctuation of wind power plant and photovoltaic power generation. In this study, the current application of electric power storage system using battery is introduced in detail, and I have thought out it's application fields based on the foreign examples. These are demand side response, upgrade of the power quality, stabilization of fluctuation of renewable energy and distributed generation for filling elapse.

• The Transactions of The Korean Institute of Electrical Engineers
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• v.60 no.7
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• pp.1331-1338
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• 2011

This paper proposes a method for frequency control of islanded microgrid with battery energy storage system. For frequency control of islanded microgrid, battery energy storage system uses a phase locked loop algorithm with positive sequence components for a fast frequency estimation. Microgrid is a power system with small inertia because it has small capacity generators and inverter systems for renewable energy. So, Islanded microgrid's frequency varies fast and large as small generation and load changes. To reduce frequency variation of islanded microgrid, it needs a device with fast frequency response. For fast frequency response, a fast frequency tracking is important. To show the validation of proposed fast frequency tracking algorithm, battery energy storage system with proposed algorithm is tested in microgrid pilot plant.

• Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
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• v.30 no.1
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• pp.21-27
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• 2016

The study concerning about the grid connection of the large-capacity battery energy storage system(BESS) is increasing. However, the protection study which is necessary to maintain the reliability of distribution system has been hardly performed. Therefore, this paper analyzes the effect of reclosing among protection issues in distribution system with BESS and proposes the new relcosing method. To verify the proposed method, the BESS, distribution system, and proposed method are modeled by using EMTP/ATPDraw and the various simulations according to the fault clearing time are performed. The simulation results show that the reclosing in distribution system with BESS is successfully performed by proposed method and the operation of BESS is not affected from reclosing.

• 한국신재생에너지학회:학술대회논문집
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• 2006.06a
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• pp.9-12
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• 2006

We performed molecular dynamics simulations on the conventional MOF, IRMOF-14 and the catenated MOF with two MOF chains, IRMOF13, to find out rational design and synthetic strategies toward efficient hydrogen storage materials. The molecular dynamics calculations were done using Universal force fields and the analysis of result was performed during the NVE dynamics after preliminary NVT dynamics at 77K. The results showed the density of adsorbed hydrogen molecules was increased in the various pores created by catenation of MOFs while the large amount of volume in conventional MOF was not effectively utilized to store hydrogen. Those calculation results commonly showed the proper control of pore si Be for hydrogen storage into MOF by catenation would be one of the efficient ways to increase hydrogen capacity of MOFs.

• The Transactions of the Korean Institute of Electrical Engineers P
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• v.63 no.4
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• pp.254-259
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• 2014

In this paper, we describe construction of a wind stabilization demo-site and effects of output power control of wind turbines for suppression of ramp rate using ESS (Energy Storage System). It is difficult to control the output power of distributed generator such as wind turbine which of variation is very large. If the large capacity wind farm be interconnected into power system may cause blackout due to Power Quality. For these reasons, the international standards such as Grid-Code is limited to less than 10 [%/min] of renewable energy ramp rate. The case of Korea, government actively conducts propagating large-scale renewable energy for green growth policy, to interconnecting more renewable energy into power system is necessary for stabilization technology. For these reasons, the POSCO consortium has constructed a wind stabilization demo-site that is configured as 500 [kWh] battery energy storage systems can output up to 3 [C-Rate] and two wind turbines rated 750 [kW]. In POSCO consortium, which implements various methods stabilizing output power of wind turbine such as smoothing, section firming and ramp control, we derive the results of long-term demonstration that can be controlled to satisfy to the international standard about ramp rate [%/kW] of wind turbine output power.

• Resources Recycling
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• v.24 no.5
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• pp.40-55
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• 2015

The purpose of this study is to analyse whether the waste disposal volume level in the construction waste disposal industry makes a different effect on earnings management behaviour by size of the licensed storage capacity and by location of the waste disposal site. The empirical results of this study are as follows. First, the waste disposal volume significantly influences earnings management behavior. When it comes to the size of licensed storage capacity in the small-sized capacity firms, the smaller waste disposal volume firms make more aggressive earnings management by using discretionary accruals. On the other hand, in the large-sized capacity firms, more waste disposal volume firms report higher earnings by adjusting more discretionary accruals. Second, the effects of waste disposal volume on the earnings management show different pattern depending on the location of waste disposal site. When the firms are located in the non-capital regions, the smaller waste disposal volume firms report higher earnings by adjusting discretionary accruals as well as by using real activities earnings management. However, the firms located in the capital regions show more aggressive earnings management when they have higher waste disposal volume level.

• Proceedings of the Korean Institute of Intelligent Systems Conference
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• 2003.09a
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• pp.640-643
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• 2003

A Walsh function based associative memory is capable of storing m patterns in a single pattern storage space with Walsh encoding of each pattern. Furthermore, each stored pattern can be matched against the stored patterns extremely fast using algorithmic parallel processing. As such, this special type of memory is ideal for real-time processing of large scale information. However this incredible efficiency generates large amount of crosstalk between stored patterns that incurs mis-recognition. This crosstalk is a function of the set of different sequencies [number of zero crossings] of the Walsh function associated with each pattern to be stored. This sequency set is thus optimized in this paper to minimize mis-recognition, as well as to maximize memory saying. In this paper, this Walsh memory has been applied to the problem of face recognition, where PCA is applied to dimensionality reduction. The maximum Walsh spectral component and genetic algorithm (GA) are applied to determine the optimal Walsh function set to be associated with the data to be stored. The experimental results indicate that the proposed methods provide a novel and robust technology to achieve an error-free, real-time, and memory-saving recognition of large scale patterns.

• The Transactions of the Korean Institute of Electrical Engineers B
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• v.52 no.11
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• pp.557-562
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• 2003

To develop a stable and compact small-sized superconducting magnetic energy storage (SMES) system, which provides electric power with high quality to sensitive electric loads, we fabricated a SMES coil and tested it. Because such a large-sized superconducting coil quenches far away from its critical current, the recovery current is frequently used as a stability criterion in the coil fabrication. Therefore, we first investigated the recovery current characteristics of the large current conductor, which was used in our SMES coil fabrication. The test results indicate that the recovery currents measured in the conductor are nearly identical to those based on the single wire. This implies that the recovery current is affected by the conductor's cooling condition rather than its size and current capacity. In the SMES coil test the first quench occurred at 1250 A, which is equivalent to the stored energy of about 2 MJ. It corresponds to the quench current density of about $130A/mm^2$ This value is much higher in comparison with that reported in the other work. In addition, the first quench current of the coil agrees well with the measured recovery current of the conductor having similar cooling condition with it. This means that to determine the recovery current of a conductor is, first of all, important in the design and fabrication of a large-sized superconducting coil.

• Progress in Superconductivity and Cryogenics
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• v.10 no.3
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• pp.27-31
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• 2008

In order to cool the SMES coil to the operating temperature, conduction cooling is generally used. However, it often consumes a large amount of electric power because of it's continuous cryocooler operation. This can also lead to poor thermal stability and serious protection problems of the system. Solid nitrogen (SN2) can counter those disadvantages in the conduction cooling system because it has a large heat capacity. Particularly, a large amount of enthalpy with a minimal weight to the cold body of SN2 makes a compact and portable system by increase a recooling to recooling time period (RRTP) value. A conceptual design of the proto-type SN2 cooling system for a portable HTS superconducting magnetic energy storage (SMES) system will be introduced in this paper.

• Atmosphere
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• v.27 no.2
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• pp.251-258
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• 2017

The standard weighing raingauges have a capacity limit in measuring the amounts of precipitation. Exceptions are those using a siphon to drain the collected water during observations. To reduce the drain time of the siphon type or to overcome the hassles associated with the manual emptying of the bucket for measuring, the most of weighing gauges use a large bucket for storing of rainwater to be measured. To avoid the above-mentioned adverse requirements, we propose a paired barrel for a weighing raingauge. The paired barrel may improve the accuracy of the weighing raingauges by getting rid of their capacity limit and make the gauges smaller in size and lighter in weight than the conventional ones. We showed its proper function and the feasibility of realization by testing a prototype paired barrel.