• Journal of the Korean Solar Energy Society
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• v.33 no.4
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• pp.23-30
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• 2013

This paper presents the determination method of the hybrid energy storage capacity for compensating the output of wind power when disconnecting from the grid. In the wind power output compensation, a lot of charging and discharging time with lithium-ion battery will be deteriorated the life time. And also, this fluctuation will cause some problems of the power quality and power system stability. To solve these kind of problems, many researchers in the world have been studied with BESS(Battery Energy Storage System) in the wind farm. But, BESS has the limitation of its output during very short term period, this means that it is difficult to compensate the very short term output of wind farm. Using the EDLC (Electric Double Layer Capacitor), it is possible to solve the problem. Installing the battery system in the wind farm, it will be possible to decrease the total capacity of BESS consisting of HESS (Hybrid Energy Storage System). This paper shows simulation results when not only BESS is connected to wind farm but also to HESS. To verify the proposed system, results of computer simulation using PSCAD/EMTDC program with actual output data of wind farms of Jeju Island will be presented.

• Journal of IKEEE
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• v.23 no.2
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• pp.695-703
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• 2019

In this paper, we propose a method to remove the circulating current which can occur in the parallel connection of the high voltage series connected battery module in the battery pack. The removal way is a method of inserting a module named VVSM (Variable Voltage Variable Module) using bidirectional DCDC converter and supercapacitor in place of one or some of the cascaded battery cells in the battery pack configuration. In this module, it operates like a battery cell that can be controlled at a desired voltage. VVSM is used to match the voltages of the cascaded battery modules very easily. To demonstrate the proposed method, a PSIM simulation for battery model is used. In addition, the module with only the battery cell connected in series and the module with the proposed VVSM are made, and the two modules were connected in parallel to measure the circulating current between the two modules. As a result, it was verified that the proposed method effectively suppressed the circulating current.

• Journal of the Korean Crystal Growth and Crystal Technology
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• v.29 no.4
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• pp.160-166
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• 2019

Cerium oxide ($CeO_2$, often called as Ceria) is one of the valuable rare earth oxide materials, which has been widely used for high temperature applications such as solid oxide fuel cells, automotive three-way catalysts and oxygen storage capacity. Considering those application, it is important to improve high redox and thermal stability with high surface morphology because the high surface area of $CeO_2$ could improve the catalytic reactivity at high temperature conditions. Herein we successfully fabricated hierarchical flower-like $CeO_2$ deposited via controlling pathway of precipitation reaction to supply carbonate ion lead to the flower-like morphology. The hexagonal lattice system of precipitated precursor shows better thermal stability then orthorhombic one during thermal cycling condition.

• Journal of Advanced Navigation Technology
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• v.23 no.4
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• pp.309-315
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• 2019

This paper proposes an implementation of unequal power divider with 1:3 and 1:4 splitting ratio in multi-section structure using CPW and offset coupled transmission line. The power divider consists of a multi-section transmission line and a circuit with parallel capacitors and resistors. A multi-section transmission line was implemented by decomposing a ${\lambda}/4$ single transmission line terminated by an arbitrary impedance and converging it with a multi-section transmission line shorter than $90^{\circ}$ electrical length, and RC parallel circuits were connected between transmission lines to obtain reflection coefficient of output port and isolation characteristics between the output port. In this way, it was confirmed that the transmission lines at the unequal power divider designed at 2 GHz were shorter than ${\lambda}/4$ and implemented at least 27% less than the conventional ones, and that the broadband characteristics could be obtained.

• The Journal of the Institute of Internet, Broadcasting and Communication
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• v.20 no.6
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• pp.129-135
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• 2020

This study relates to a characteristic change and frequency correction method according to the temperature sensor position of an oven-controlled crystal oscillator (OCXO) using a 10 MHz SC-CUT crystal. Although there are several methods of manufacturing the previous high-precision 10MHz OCXO, the present study shows that the frequency stability characteristics against external temperature changes can be improved simply by adjusting the position of the temperature sensor. Factors that affect the frequency characteristics of the OCXO include the temperature transmitted to the crystal, the voltage applied to the crystal, and the capacitance constituting the oscillation circuit. The amount of change in frequency due to these factors was measured, and the change in the correction value of the OCXO output frequency was investigated by measuring the temperature inflection point and changing the capacitor value.

• Journal of Advanced Navigation Technology
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• v.24 no.6
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• pp.557-565
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• 2020

In order for thermal degradationIn, excore nuclear flux monitoring system, as a monitoring and signal processing methodology of reactor power, monitors neutron pulses generated during nuclear fission as frequency status, and converts them into DC voltage, and then log values resultantly. The methods realy applied in the nuclear power plant are to construct combination of counters and flip-flops, or diodes and capacitors up to now. These methodes are reliable for relative high frequencies, while not credible for reasonable low frequencies or extreme low values. Therefore, we developed the circuit that converts frequencies into DC voltages, into and into log DC values in the wide range from low Hz to several hundred high kHz. We proved their validities through testing them using real data used in nuclear power plant and analyzed their results. And, these methods will be used to measure the neutron level of excore nuclear flux monitoring system in nuclear power plant.

• Journal of IKEEE
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• v.25 no.4
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• pp.591-597
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• 2021

This paper proposes an EMC-aware PCB design method to reduce electromagnetic emission, where trace length and teturn path of critical signal are shortened by changing chip location and trace layout on the PCB, while additional filters or decoupling capacitors are not required. In the proposed method, signal velocity is calculated for various signals on the PCB. Critical signal with the fastest signal velocity is determined and its return path is shortened as much as possible by placing chip location and trace routing first. Return path of critical signal should be carefully designed not to have discontinuity. Power plane and ground plane should be carefully designed not to be divided, since these planes are the reference of return path. The proposed method was applied to automotive directional Bluetooth speaker which failed to pass CISPR 32 and CISPR 25 EMC tests. Its PCB was redesigned based on the proposed method and it easily passed the EMC tests. The proposed method is useful to EMC-sensitive electronic equipments.

• Journal of IKEEE
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• v.26 no.2
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• pp.313-318
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• 2022

The feedback voltage detection structure is proposed to alleviate overshoot and undershoot caused by the removal of the existing external output capacitor. Conventional LDO regulators suffer from overshoot and undershoot caused by imbalances in the power supply voltage. Therefore, the proposed LDO is designed to have a more improved transient response to form a new control path while maintaining only the feedback path of the conventional LDO regulator. A new control path detects overshoot and undershoot events in the output stage. Accordingly, the operation speed of the pass element is improved by charging and discharging the current of the gate node of the pass element. LDO regulators with feedback voltage sensing architecture operate over an input voltage range of 3.3V to 4.5V and have a load current of up to 200mA at an output voltage of 3V. According to the simulation result, when the load current is 200mA, it is 73mV under the undershoot condition and 61mV under the overshoot condition.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 1993.11a
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• pp.17-20
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• 1993

In this paper, the (1-x)($Sr_{0.50}$$Pb_{0.25}$$Ba_{0.25}$)$TiO_3$-x $Bi_2$$Ti_3$$O_{9}$(x=0,4,6,8[mol.%]) ceramics with paraelectric properties were, fabricated by mixed oxide method. The dielectric and structural properties of ceramics were studied with sintering temperature and addition of $Bi_2Ti_3O_{9}$, and the application for the high - voltage capacitor was investigated. In the specimens with sintering at 1350[$^{\circ}C$], sintered density was showed the highest value of 5.745[g/cm$^3$]. Increasing of sintering temperature, average grain size was increased. The specimen. ($Sr_{0.50}$$Pb_{0.25}$$Ba_{0.25}$)$TiO_3$sintered at 1350[$^{\circ}C$] showed good dielectric properties and breakdown voltage was showed the highest value of 200[kV]. Temperature coefficient of capacitance was stabilized in specimens added $Bi_2Ti_3O_{9}$ Sintered density. dielectric properties and breakdown voltage ware decreased with increasing the contents of $Bi_2Ti_3O_{9}$.

• Journal of the Korean Vacuum Society
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• v.17 no.4
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• pp.331-340
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• 2008

A method of measuring the current and voltage is suggested in the circuit of cold cathode fluorescent lamps (CCFLs) which are driven at a high frequency of $50{\sim}100\;kHz$ and a high voltage of several kV. It is difficult to measure the current and voltage in the lamp circuit, because the impedance of the probe at high voltage side causes the leakage current and the variation of luminance. According to the analysis of equivalence circuit with the probe impedance and leakage current, the proper measuring method is to adjust the input DC voltage and to keep the specific luminance when the probe is installed at a high voltage circuit. The lamp current is detected with a current probe or a high frequency current meter at the ground side and the voltage is measured with a high voltage probe at the high voltage side of lamp. The lamp voltage($V_C$) is measured between the ballast capacitor and the lamp electrode, and the output voltage($V_I$) of inverter is measured between inverter output and ballast capacitor. As the phases of lamp voltage($V_C$) and current ($I_G$) are nearly the same values, the real power of lamp is the product of the lamp voltage($V_C$) by the lamp current($I_G$). The measured value of the phase difference between inverter output voltage($V_I$) and lamp current($I_G$) is appreciably deviated from the calculated value at $cos{\theta}=V_C/V_I$.