• The Transactions of the Korean Institute of Power Electronics
• /
• v.5 no.6
• /
• pp.610-619
• /
• 2000

This paper presents an off-line UPS using the high temperature superconductive magnetic bearing. FES(Flywheel Energy Storage) system has good advantages in compare with lead acid battery. So, high efficiency FES using high temperature SMB(superconductive magnetic bearing) was composed in this paper. The outer rotor type of PMSM(Permanent Magnet Synchronous Motor) as motor/generator was used for the experiment, and square wave current and sinusoidal wave control methods was compared for high efficiency operation of motor/generator. The circuit for in phase sinusoidal wave current control with EMF in the full speed range was designed and the proposed flywheel energy storage system was applied in single phase off-line UPS system. As the stable operation characteristics of prototype system was confirmed, the its excellence as energy storage device in Off-line UPS was proved.

• Journal of the Korean Society for Precision Engineering
• /
• v.26 no.10
• /
• pp.97-107
• /
• 2009

Recent technologies of the car are focused on improving vehicle's fuel efficiency and developing alternative energy sources. These technologies bring on the development of hybrid car. On the other hand, because of short driving distance, low efficiency of charging and high price, energy storage system need to improve the storage capability. It is very important to understand the existing technologies, grasp the existing patent and establish the technical target to improve the energy storage system. In this paper, technology trends of energy storage system of the hybrid car are analyzed. This study was based on the applied and registered patent in Korea, Japan, U.S.A and Europe until December 2008. The analyses are divided into two categories: a battery system and charging system of the hybrid car. The facts of the level of technology, trends of the R&D of leading companies, key patents, blank of the technology were analyzed. Finally the future R&D strategy of hybrid car are established.

• Journal of the Korea Academia-Industrial cooperation Society
• /
• v.18 no.12
• /
• pp.26-31
• /
• 2017

The conventional method of improving the transient stability in a power system is the use of reactive power compensation devices, such as the STATCOM and SVC. However, this traditional method cannot prevent the rapid voltage collapse brought about by the stalling of the motor due to a system fault. On the other hand, the ESS (Energy Storage System) provides fast-acting, flexible reactive and active power control. The fast-acting power compensation provided by an energy storage system plays a significant role in enhancing the transient stability after a major fault in the power system. In this paper, a method of enhancing the transient stability using an energy storage system is proposed for power systems including a dynamic load, such as a large motor. The effectiveness of the energy storage system compared to conventional devices in enhancing the transient stability of the power system is presented. The results of the simulations show that the simultaneous injection of active and reactive power can enhance the transient stability more effectively.

• Journal of the Institute of Electronics and Information Engineers
• /
• v.51 no.2
• /
• pp.85-91
• /
• 2014

Cloud storage system uses a distributed file system for storing and managing data. Traditional distributed file system makes a triplication of data in order to restore data loss in disk failure. However, enforcing data replication method increases storage utilization and causes extra I/O operations during replication process. In this paper, we propose a data replication method using erasure codes in cloud storage system to improve storage space efficiency and I/O performance. In particular, according to data access frequency, the proposed method can reduce the number of data replications but using erasure codes can keep the same data recovery performance. Experimental results show that proposed method improves performance in storage efficiency 40%, read throughput 11%, write throughput 10% better than HDFS does.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
• /
• v.26 no.6
• /
• pp.247-256
• /
• 2014

The regulations to reduce energy consumption and carbon dioxide emission in building sectors are being developed and promoted all over the world. However, in Korea, as balcony extension of the apartments has been legally allowed, it became prevalent and resulted in excessive energy consumption. This study derived the possibility of PCM application to the thermal storage wall system through theoretical consideration and investigated the problems occurring when the balcony space has been extended to the diverted space. In addition, this study aims at the possibility of verifying the installation and confirming the cooling energy reduction effect, by conducting measuring tests with the actual installation of PCM applied thermal storage wall system. As a result of theoretical consideration, it is determined that the disadvantages with the existing thermal storage wall system can be complemented by applying PCM, and this study suggests the PCM applied Thermal Storage Wall System. The study was conducted on 1/6 of a miniature inner room of a domestic apartment with 84 $m^2$ of exclusive area. From the results of actual measurements, it is confirmed that the balcony extension structure can gain 11.3% of more calories than the existing balcony structure, resulting in the increase in cooling energy usage. It is determined that the installation of the PCM applied Thermal Storage Wall System may gain 25.2% of less calories to reduce cooling energy usage.

• Journal of Electrical Engineering and Technology
• /
• v.6 no.4
• /
• pp.447-458
• /
• 2011

In this paper, a novel flywheel energy storage device, called the flexible power conditioner, which integrates both the characteristics of the flywheel energy storage and the doubly-fed induction machine, is proposed to improve power system stability. A prototype is developed and its principle, composition, and design are described in detail. The control system is investigated and the operating characteristics are analyzed. The test results based on the prototype are presented and evaluated. The test results illustrate that the prototype meets the design requirement on power regulation and starting, and provides a cost-effective and effective means to improve power system stability.

• Proceedings of the Korean Society for Agricultural Machinery Conference
• /
• 1993.10a
• /
• pp.952-965
• /
• 1993

A simulation modeling is necessary for the optimal design of a rice processing plant, which consists of a facility (a silo system) of rice drying and storage and a rice mill plant. In a rice processing plant, the production scheduling and the decision on capcity of each unit based on a queuing theory is very important and difficult. In this study a process-oriented simulation model was developed for the design of a rice drying and storage system with SLAMSYSTEM. The simulation model is capable of simulating virtually all the processing activities and provides work schedules which minimize total processing time , mean flow time and bottleneck of the plant system and estimate drying time for a batch in a drying silo. Model results were used for determination the size and capacity of each processing unit and for analyzing the performance of the plant . The developed model was actually applied to construct a grain silo system for rice drying and storage.

• Proceedings of the Korea Information Processing Society Conference
• /
• 2007.05a
• /
• pp.1237-1239
• /
• 2007

This paper proposes a virtual storage system for smart home/office embedded devices by utilizing AoE and HyperSCSI protocols. It relies on current Ethernet infrastructures and aims to provide a low-cost solution for the storage limitation problem on embedded devices. We choose AoE (ATA over Ethernet) and HyperSCSI in our implementation because they are relatively lightweight compared to other network storage protocols such as NFS(Network File System), CIFS(Common Internet File System) and iSCSI(internet Small Computer System Interface). The design and architecture of our proposed virtual system as well as the prototype demonstration are presented in this paper.

• Proceedings of the KSME Conference
• /
• 2001.11a
• /
• pp.361-366
• /
• 2001

The purpose of installation of the brine heating system for LNG storage tank is the prevention of ground freezing. If the ground of LNG tank areas is frozen, it is caused by safety problems. The design of brine heating system for LNG storage tank which is constructing in our country is not well considered about domestic weather conditions and economical efficiency. Therefore, this paper reports on the study of the optimized temperature of inside pipes and cooling process through the transient analysis by using the existing brine heating system.

• Proceedings of the KSR Conference
• /
• 2010.06a
• /
• pp.514-520
• /
• 2010

This paper is about control algorithms that bi-direction DC-DC Converter using Super Capacitor and regenerative power from DC feeding system in train. In order to take advantage of regenerative energy efficient, charge and discharge level value of energy storage system serve as an important factor. Respect to output fluctuations of the substation and catenary voltage changing, we offers Charge-Discharge Auto Level Tuning Algorithms to improve system following of Energy Storage System.