• Journal of Electrical Engineering and Technology
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• v.9 no.4
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• pp.1182-1187
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• 2014

This paper proposes an energy management strategy and adaptive control for superconducting magnetic energy storage (SMES) in a distribution power system with a grid-connected photovoltaic (PV) farm. Application of the SMES system can decrease the output power fluctuations of PV system effectively. Also, it can control the real and reactive powers corresponding to the scheduled reference values with adequate converter capacity, which are required at a steady-state operating point. Therefore, the adaptive control strategy for SMES plays a key role in improving the system stability when the PV generation causes uncertain variations due to weather conditions. The performance of proposed energy management strategy and control method for the SMES is then evaluated with several case studies based on the PSCAD/EMTDC$^{(R)}$ simulation.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.14 no.6
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• pp.2979-2984
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• 2013

This paper proposes a modeling and controller design method of Flywheel Energy Storage System(FESS) for solving the unstable operation problem in hybrid generation system with wind turbine and diesel generator applied in island area. FESS is considered as a permanent magnetic synchronous machine connected to flywheel because of its efficiency. The controller of FESS is composed of AC/DC/AC back-to-back converter. The AC/DC converter is designed to charge/discharge according to the frequency variation and the DC/AC converter to operate to keep the DC bus voltage constant. The proposed modeling and controller design method of FESS was applied to hybrid generation system with wind turbine and diesel generator. The unstable operation problem owing to wind variations was solved through simulation results.

• Proceedings of the KSME Conference
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• 2001.06d
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• pp.585-588
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• 2001

Particle contamination on the data storage disks has been a serious problem for magnetic hard disk drive manufacturers. For high storage optical disks, such as DVD-ROM/RAM or NFR (near field recording) system, particle-induced damages can be also detected because only a few micrometer particles can prevent read/write signal from optical lens. The increasing areal density and smaller bit size accelerates particle induced damages on the optical disk. One of the methods to prevent particle contamination on the optical disk surface is to handle the disk enclosed in a cartridge like a modern DVD-RAM disk. However, even for a perfectly sealed disk drive, particles are found inside the drive. The other method is to improve disk surface characteristics. Particle contamination on the surface can be reduced by proper selection of disk coating materials. [n this paper, particle detachment ratios for CD (compact disk), DVD (digital versatile disk), HD (magnetic hard disk), HD with Jut lubricant, and aluminosilicate substrate HD were investigated. Surface roughness and surface energy of the test disks were compared with the particle detachment ratios. Proper substrate and lubricant characteristics to reduce particle contamination on the disk surface were found.

• The Transactions of The Korean Institute of Electrical Engineers
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• v.59 no.12
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• pp.2190-2194
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• 2010

Wind power generation system (WPGS) of Ulleung Island causes frequency and voltage fluctuation due to wind speed variation during night time. Superconducting magnetic energy storage (SMES) system can overcome the fluctuations through the fast response time of energy charging and discharging. The SMES system should be connected to the terminal of the WPGS for frequency stabilization. To demonstrated the effectiveness of SMES system for power quality improvement, Ulleung Island power network was modeled in a real time digital simulator (RTDS). The RTDS-based simulation results of power quality improvement with SMES are investigated and discussed in detail.

• Proceedings of the KIEE Conference
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• 2015.07a
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• pp.521-522
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• 2015

Many countries concern about environmental problems. Therefore, they have made regulation for mandatory reduction of greenhouse gases. Electric Vehicles(EVs) are one of the most effective counterproposals for it. EVs are usually charging for it by using actual distribution system of the Korea Electric Power Corporation(KEPCO). However, it could cause adverse effects such as increase of the power demand and voltage variation on the distribution system. To reduce adverse effects for demand power side, in this paper, charging for EVs by using PV(Photovolatic Power Generation) connected with ESS(Energy Storage System) are modeled by using Electro Magnetic Transient Program(EMTP). And then, the simulation results are compared with EVs that are connected to the distribution system of KEPCO for using charge.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2008.11a
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• pp.129-130
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• 2008

• Journal of Advanced Navigation Technology
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• v.13 no.4
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• pp.509-514
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• 2009

In this paper, we designed and analyzed 256GB DRAM-based SSD storage using DDR1 memory and PCI-e interface. SSD is a storage system that uses DRAM or NAND Flash as primary storage media. Since the SSD read and write data directly to memory chips, which results in storage speeds far greater than conventional magnetic storage devices, HDD. Architecture of the proposed SSD system has performance of high speed data processing duo to use multiple RAM disks as primary storage and PCI-e interface bus as communication path of RAM disks. We constructed experimental system with UNIX, Windows/Linux server, SAN Switch, and Ethernet Switch and measured IOPS and bandwidth of proposed SSD using IOmeter. In experimental results, it has been shown that IOPS, 470,000 and bandwidth,800MB/sec of the DDR-1 SSD is better than those of the HDD and Flash-based SSD.

• The Journal of the Korea institute of electronic communication sciences
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• v.10 no.6
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• pp.691-698
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• 2015

Recently, the power industry has a great interest in the superconducting energy storage device as a way to maximize energy efficiency to cope with global warming. A superconducting energy storage device can archive maximization of electric energy use efficiency by storing in the form of a magnetic field energy or a kinetic energy without loss a large amount of electrical energy at the non-peak load and then converting it again into electric energy at the peak load. Therefore, in this study, such as the concept of the superconducting energy storage technologies, the present state of its research and development and its applications are surveyed and analyzed to establish methodology applying the superconducting energy storage technologies to power system.

• The Transactions of The Korean Institute of Electrical Engineers
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• v.63 no.6
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• pp.820-827
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• 2014

Since a microgrid has renewable energy sources, imbalance between power supply and power demand occurs in the islanded mode. In order to solve the imbalance, several energy storage systems (ESSs) such as bettary energy storage system (BESS), EDLC (electric double layer capacitor), flywheel, and SMES (superconducting magnetic energy storage) are generally used. Especially, their electrical characteristics are different. For efficient use of them, a coordinated control scheme is required. In this paper, a coordinated control scheme for using a Lead-acid BESS, a Lithium BESS, and a EDLC is designed to efficient frequency control for a microgrid in the islanded mode. The coordinated frequency control strategy is designed based on their electrical characteristics. The feasibility of the proposed coordinated frequency control strategy is verified through the simulation.

• Journal of the Korean Society for Precision Engineering
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• v.18 no.8
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• pp.174-181
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• 2001

Nowadays, the improvement and development of Multi-media and information & communication technology is rapidly processed. They need large data storage capacity. So that, many studies and researches in data storage have been carried out. According to them, the data storage capacity has been increased. But the limitation of storage capacity is happened for several problems. One of them is spot & pit size in optical and magnetic data storage and another is the resolution of actuators. The problems in spot & pit size are covered by new data storage methods-- for examples, AFM(Atomic Force Microscopy), MO(Magneto-optical) system, and NFR(Near-Field decoding) system etc. But the resolution limit of an actuator was not developed and doesn\`t follow up the development of spot & pit size. Because of them, we should improve a resolution of an actuator. Especially, in this paper an actuator if studied and designed for NFR (in using SIL(Solid Immersion Lens) system. It is a dual stage actuator, which consists of a Fine actuator and a Coarse actuator. and should desire 100nm accuracy. Its actuating force generation method is VCM(Voice Coil Motor). The Fine actuator is composed of 4-leaf springs and a bobbin wrapped by coil. The Coarse actuator has Coils and 3-Roller bearings. Also, The Characteristics of designed actuator for NFR system is estimated by Sine-Swept mode and LDV(Laser Doppler Vibro-meter).