• The Transactions of the Korean Institute of Electrical Engineers B
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• v.52 no.5
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• pp.203-210
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• 2003

This paper describes high voltage and high energy density capacitor developed for pulsed power applications. The rated voltage of the developed capacitor is DC 22 [kV], the capacitance is 206 [$\mu$F] and the energy density is about 0.7 [kJ/kg]. Polypropylene film and kraft paper were used as the dielectrics. The ratio of the thickness of each dielectric material which consists of the composite dielectric structure, stacking factor and the termination method were determined by the charging and discharging tests on model capacitors. In terms of energy density, the developed capacitor has higher energy density compared with the products of foreign leading companies. In addition, it has been proved that the life expectancy can be more over 2000 shots through the charging and discharging test. The voltage reversal factor was 20%. This capacitor can be used as numerous discharge applications such as military, medical, industrial fields.

• Journal of the Korean Institute of Telematics and Electronics B
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• v.32B no.6
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• pp.932-942
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• 1995

A spacecraft power system can be divided into two types : DET system(Direct Energy Transfer system) and PPT system(Peak Power Tracking system). In a DET system employing the regulated bus voltage control method, the battery charger and discharger are widely used for the bus voltage regulation. The battery charger has two different modes of operation. One is the bus voltage regulation mode and the other is the charge current regulation mode. The battery discharger is employed to provide the power when the spacecraft is in the earth's shadow or the sun is eclipsed. The operating mode, charging or discharging, is selected by a power control circuit. In this paper, small-signal dynamic characteristics of battery charging and discharging system are analyzed to facilitate design of control loop for optimum performance. Control loop designs in various operating modes are discussed. Anaylses are verified through experiments.

• Elastomers and Composites
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• v.33 no.4
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• pp.238-245
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• 1998

In this paper, the electric property was investigated for insulation diagnosis of radiation of EPR electric power cables by partially irradiation with $^{60}Co-{\gamma}$ rays. As the rate of radiation increased from 100Mrad to 200Mrad, charging current and discharging current were increased from $1.03{\times}10^{-7}$(A) to $4.3{\times}10^{-9}$(A). In addition, we found charging current and discharging current of cables subjected to 50% and 16.7% irradiation changed the length of the part 1/2 to 1/6 as in comparison with cables degraded by 100% irradiation. For 22m and 66m of cables which had not been degraded yet, we realized the value of charging current and discharging current of 66m cables is three times higher than 22m cables. From these results, it is demonstrated that the possibility of utilizing charging current and discharging current as the diagnosis method of insulation degradation with irradiating EPR cables by $^{60}Co-{\gamma}$ rays.

• Journal of the Korean Society for Precision Engineering
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• v.12 no.11
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• pp.125-131
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• 1995

Pneumatic System has been mainly used as main equipment for actuation and control of fluid force in manufacturing industry. For velocity control of piston, meter-out restriction method is used in many cases. In this systems, meter-out restriction method is adopted for analysing the Dynamic Charging and Discharging Process which is Variable Volume Chamber. Experiments has been conducted for different supply pressure condition. As a experimental result, charge side chamber pressure rises to supply pressure rapidily and discharge side chamber pressure decreases. Also, when the air in the cylinder is discharged, tempdrature of air decreases steeply. Restriction of the Cylinder sometimes freeze and it dose not function. The result will be useful for the analysis of pneumatic system.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.26 no.7
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• pp.301-307
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• 2014

This paper presents a numerical study on the constrained melting of a phase change material inside various capsule containers, using water and HDPE (High Density Polyethylene) as a PCM and a capsule material, respectively. The computations are based on an iterative, finite-volume numerical procedure that incorporates a single-domain enthalpy formulation for simulation of the phase change phenomenon. Using the enthalpy method, various capsule configurations, such as a capsule from E company, an isochoric cylinder capsule, an equivalent diameter sphere capsule, and an isochoric sphere capsule, are used to investigate the effect of capsule configurations on the charging and discharging performance. A transient three-dimensional model is used for each case. The simulation results show that the capsule from E company results in a higher melting and solidification rate of the PCM, than the other capsule configurations considered in this research.

• Journal of Electrical Engineering and Technology
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• v.13 no.6
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• pp.2227-2235
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• 2018

Under the current policies and compensation rules in South Korea, Photovoltaic (PV) generation supplier can maximize the profit by combining PV generation with Energy Storage System (ESS). However, the existing operational strategy of ESS is not able to maximize the profit due to the limitation of ESS capacity. In this paper, new ESS scheduling algorithm is introduced by utilizing the System Marginal Price (SMP) and PV generation forecasting to maximize the profits of PV generation supplier. The proposed algorithm determines the charging time of ESS by ranking the charging schedule from low to high SMP when PV generation is more than enough to charge ESS. The discharging time of ESS is determined by ranking the discharging schedule from high to low SMP when ESS energy is not enough to maintain the discharging. To compensate forecasting error, the algorithm is updated every hour to apply the up-to-date information. The simulation is performed to verify the effectiveness of the proposed algorithm by using actual PV generation and ESS information.

• 한국신재생에너지학회:학술대회논문집
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• 2009.06a
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• pp.315-318
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• 2009

Hydrogen is the ideal candidate as an alternative energy carrier, so many hydrogen storage methods are investigated. The hydrogen storage method using metal hydride is good candidate as energy sources for portable devices because hydrogen-storage as metal hydride shows large volumetric storage density. In this study, we investigated the variations of hydrogen charging/discharging performance of metal hydride tanks at different temperature conditions. We charged metal hydride tanks with hydrogen in low temperature because of the exothermic reactions of hydrogen absorption while we discharged in high temperature to provide sufficient heat because of the endothermic reactions of desorption. In addition, we investigated the difference of hydrogen charging/discharging performance between two tanks having different sizes.

• Proceedings of the IEEK Conference
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• 2001.06b
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• pp.85-88
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• 2001

This paper suggests an improved switch architecture for the rechargeable battery protection IC. In the existing protection IC, charging and discharging switches composed of the CMOS transistor and the diode are external components. It is difficult to integrate the switches in a CMOS process due to the large chip-size overhead and inevitable parasitic effects. In this paper, we propose a new switch architecture of the MOSFET's 'diode connection' method. The performance and chip-size overhead are proved to be adequate for the fully integrated protection IC.

• Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
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• v.29 no.2
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• pp.82-90
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• 2015

This paper proposes an efficient bi-directional DC/DC converter topology using multi-phase interleaved method for power storage system. The proposed converter topology is used for a power storage system using a vanadium redox flow battery(VRFB) and is configured to enable bidirectional power flow for charging and discharging of VRFB. Proposed DC/DC converter of the 4 leg method is reduced to 1/4 times the rating of the reactor and the power semiconductor device so can be reduce the system size. Also, proposed topology is obtained the effect of four times the switching frequency as compared to the conventional converter in each leg with a 90 degree phase shift 4 leg method. This can suppress the reduction of the life of the secondary battery because it is possible to reduce the current ripple in accordance with the charging and discharging of VRFB and may increase the efficiency of the entire system. In this paper, it proposed bidirectional high-efficiency DC/DC converter topology Using multi-phase interleaved method and proved the validity through simulations and experiments.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2001.07a
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• pp.519-522
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• 2001

Recently, the battery charging technology and reducing technology of harmonics on AC input line are rising importantly according to increasing electrical facilities that it has been replaced battery with emergency power. In this study, I proposed that an auto-charging circuit of battery has low cost with simple-construction circuit, relative, harmonics reduction with diode tap-change method, high reliability of system for using characteristics of thyristor switching. In case of this circuit, convenience and reliability of maintenance of battery power units were more improved. 1 think that it is resulted in effect of prevention to shortening of battery life from over-charging and over-discharging and decrease of harmonics obstacle on AC input line.