• Progress in Superconductivity and Cryogenics
• /
• v.12 no.2
• /
• pp.17-20
• /
• 2010

A considerable amount of research material discussing designs and properties of High Temperature Superconducting Fault Current Limiter (HTS FCL) is available. However, a shortage of research concerning positioning of HTS FCL in power grid is felt. In this paper a feasibility study of HTS FCL positioning in Smart Grid through simulation analysis is carried out. A complete power network (including generation, transmission and distribution) is modeled in Simulink / SimPowerSystems. A generalized HTS FCL is also designed by integrating Simulink and SimPowerSystem blocks. The distribution network of the model has a wind turbine attached to it forming a micro grid. Three phase fault have been simulated along with placing FCL models at key points of the distribution grid. It is observed that distribution grid, having distributed generation sources attached to it, must not have a single FCL located at the substation level. Optimized HTS FCL location regarding the best fault current contribution from wind turbine has been determined through simulation analysis.

• The Journal of the Korea institute of electronic communication sciences
• /
• v.10 no.12
• /
• pp.1337-1344
• /
• 2015

Formation process through charge/discharge operation is needed in manufacturing Li-ion battery. In the process battery is discharged by a load resistor of discharger. Here, energy losses happen. Therefore, in this paper, the efficient energy operation of battery is studied in the charge/discharge system based on DC ${\mu}-Grid$. A result of computer simulation shows that if in the charge/discharge system based on DC ${\mu}-Grid$, the number of discharge batteries in comparison with three charge battery sets exceeds 133%, voltage fluctuation that occurs while the grid voltage stabilizes, which makes the system fatal. Therefore, it was demonstrated that a remarkable energy saving effect could be achieved when the number of discharge battery set is maintained to be 133% in comparison with three charge battery sets.

• Journal of Korea Multimedia Society
• /
• v.19 no.5
• /
• pp.901-909
• /
• 2016

Unprecedented attention is being given to Smart Grid, Micro Grid and Internet of Things (IoT) in the Republic of Korea recently but such systems' effect is not well experienced by the market since they require additional and costly reforms for the existing household electrical system where adaptive communication platforms are needed. As such platforms, both wireless and wire communication technologies are being considered at the moment. Usually, they include WiFi, Zigbee technologies and the latter, LAN technology. However, communication speed decline due to signal attenuation and interference during wireless communications are considered to be the major problem and the extra works involving time and costs for the LAN system construction can be another demerit. Therefore, in this paper, we have introduced a Power Line Communication-based Smart Outlet System Expandable at Home to complement these disadvantages. Proposed IoT system involves Power Line Communication (PLC) technology which is essential to constructing a Smart Grid.

• Journal of Korea Society of Digital Industry and Information Management
• /
• v.14 no.1
• /
• pp.15-25
• /
• 2018

ISO/IEC 15118 is a standard for communications and services for electric vehicle charging infrastructure. Although this standard deals only with data communication between an electric vehicle and a charge station, communication with the outside is essential for establishing an authentication system for vehicle certification and V2G service for electric power transmission. In this study, it was designed to verify the information of electric car charging infrastructure in electric power system through communication link between ISO/IEC 15118 electric vehicle model and IEC 61850 standard MMS protocol. This is demonstrated in the field so that the electric vehicle communication data is linked with the micro grid management system. This could be used as an element technology in other distributed power sources as well as electric cars in the future.

• Transactions of the Korean Society of Mechanical Engineers A
• /
• v.26 no.8
• /
• pp.1709-1718
• /
• 2002

It is well recognized that improving capacity of positive grid in battery is one of key factors for controlling the expected long lift-time of Battery Energy Storage System(B.E.S.S). Thus it is really important to characterized material properties of positive grid which are mainly affected by fabrication process. In this study, two kinds of positive grids, which were fabricated by gravity casting and die-casting technique were used. Micro-structural observation and tensile test were conducted to investigate the effect of fabrication process of positive grid. Ultrasonic measurement based on pulse-echo method and ultrasonic C-scan technique also performed to correlate ultrasonic velocity with porosity ratio in positive grid. It was found that the porosity ratio of grid fabricated by gravity casting technique increased significantly compared to the grid fabricated by die-casting technique. It was also shown that ulrasonic technique is effective to evaluate the porosity ratio in positive grid.

• Journal of Hydrogen and New Energy
• /
• v.31 no.4
• /
• pp.387-394
• /
• 2020

A parametric study of a 2.5 kW class propeller type micro hydraulic turbine was performed. In order to analyze the internal flow characteristics in the hydraulic turbine, three dimensional Reynolds-averaged Navier-Stokes equations with shear stress transport turbulence model were used and the hexahedral grid system was used to construct computational domain. To secure the reliability of the numerical analysis, the grid dependency test was performed using the grid convergence index method based on the Richardson extrapolation, and the grid dependency was removed when about 1.7 million nodes were used. For the parametric study, the axial distance at shroud span (L) between the inlet guide vane and the runner, and the inlet and outlet blade angles (β₁, β₂) of the runner were selected as the geometric parameters. The inlet and outlet angles of the runner were defined in the 3 spans from the hub to tip, and a total of 7 geometric parameters were investigated. It was confirmed that the outlet angles of the runner had the most sensitive effect on the power and efficiency of the micro hydraulic turbine.

• The Transactions of the Korean Institute of Electrical Engineers P
• /
• v.64 no.3
• /
• pp.111-115
• /
• 2015

Recently, protection coordination issues can occur due to increased fault current in power system when power system being changed radial power system to grid system such as loop power system, micro grid and smart grid. This paper analyzed Recloser-Fuse coordination in loop power distribution system with Superconducting Fault Current Limiters(SFCLs) when single line ground fault occur in loop power distribution system with SFCLs. We analyzed Recloser-Fuse Coordination in radial power distribution system and changed coordination caused by increased Fault current because of loop system when single line ground fault occur in power distribution system. This paper simulated to improve changed coordination using SFCLs in loop power distribution system. Power distribution system, SFCLs and protective devices are modeled using PSCAD/EMTDC.

• Transactions on Electrical and Electronic Materials
• /
• v.3 no.1
• /
• pp.30-37
• /
• 2002

A focusing grating coupler (FGC) was not fabricated by the 'Continuous Path Control'writing strategy but by an electron-beam lithography system of more general exposure mode, which matches not only the address grid with the grating period but also an integer multiple of the address grid resolution (5 nm). To more simplify the fabrication, we are able to reduce a process step without large decrease of pattern quality by excluding a conducting material or layer such as metal (Al, Cr, Au), which are deposited on top or bottom of an e-beam resist to prevent charge build-up during e-beam exposure. A grating pitch period and an aperture feature size of the FGC designed and fabricated by e-beam lithography and reactive ion etching were ranged over 384.3 nm to 448.2 nm, and 0.5 $\times$ 0.5 mm$^2$area, respectively. This fabrication method presented will reduce processing time and improve the grating quality by means of a consideration of the address grid resolution, grating direction, pitch size and shapes when exposing. Here our investigations concentrate on the design and efficient fabrication results of the FGC for coupling from slab waveguide to a spot in free space.

• Proceedings of the KIPE Conference
• /
• 2012.07a
• /
• pp.486-487
• /
• 2012

In this paper, novel three-port active power decoupling (APD) method for applying 250[W] micro-inverter. This type using third port for active power decoupling stores the surplus energy and supplies sufficient energy to grid. Conventional decoupling circuit is applied in single phase grid connected micro-inverter especially single-stage configuration like flyback-type DC-AC inverter. In this passive power decoupling method, electrolytic capacitor with large capacitance is needed for decoupling from constant DC power and instantaneous AC power. However the decoupling capacitor is replaced with film capacitor by using APD, thus the overall system can achieve smaller size and long lifespan. Proposed three-port flyback inverter is verified by design and simulation.

• The Transactions of The Korean Institute of Electrical Engineers
• /
• v.64 no.7
• /
• pp.992-998
• /
• 2015

The ESS is composed of Battery Package, PCS(Power Conditioning System) Package, BCU(BESS Control Unit). In Jeju smart grid test-bed, we have developed a business model by ESS power system, renewable energy, transportation, such as customers, and have demonstrated above things. We have analyzed the EMS(Energy Management System) model of KPX where manages supply and demand of domestic electrical power system. We modified and launched EMS for microgrid but the cost was expensive and the system was large size. For releasing this system from industry as a whole, it is imperative to develop PMS(Power Management System) for microgrid. However, the cost of EMS for microgrid is expensive, some systems because it is a large development of the all of the first fruits in urgent PMS(Power Management System) for microgrid to be used in industry in general. Therefore, in this paper, we propose the ESS model considering the power systems characteristics and extensibility in korea. and also we propose the PMS to manage the ESS systems.