• Journal of Power Electronics
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• v.10 no.5
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• pp.477-484
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• 2010

A pulse width modulation-voltage source inverter (PWM-VSI) is used for variable speed permanent magnet synchronous motor (PMSM) drives. The PWM-VSI fed PMSM has two major disadvantages. Firstly, the PWM-VSI DC-link voltage limits the magnitude of the PMSM terminal voltage. As a result, the motor speed is restricted. Secondly, in a low speed range, the PWM-VSI modulation index declines. This is caused by a high DC-link voltage and a low terminal voltage ratio. As a result, the distortion of the voltage command and the stator current are increased. This paper proposes an optimal pulse amplitude modulation (PAM) control which can adjust the inverter DC-link voltage by using a buck-boost DC-DC converter. At a low speed range, the proposed system can reduce the distortion of the voltage command, which improves the stator current waveform. Also, the allowable speed range is extended. In order to verify the proposed method, experimental results are provided to confirm the simulation results.

• Journal of international Conference on Electrical Machines and Systems
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• v.2 no.2
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• pp.225-231
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• 2013

Low voltage ride through capability augmentation of a hybrid micro-grid system is presented in this paper which reflects enhanced reliability in the system. The control scheme involves parallel connected multiple ac-dc bidirectional converters. When the micro-grid system is subjected to a severe voltage dip by any transient fault single power converter may not be able to provide necessary reactive power to overcome the severe voltage dip. This paper discusses the control strategy of additional power converter connected in parallel with main converter to support extra reactive power to withstand the severe voltage dip. During transient fault, when the terminal voltage crosses 90% of its pre-fault value, additional converter comes into operation. With the help of additional power converter, the micro-grid system withstands the severe voltage fulfilling the grid code requirements. This multiple converter scheme provides the micro-grid system the capability of low voltage ride through which makes the system more reliable and stable.

• The Transactions of The Korean Institute of Electrical Engineers
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• v.66 no.3
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• pp.587-592
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• 2017

In the three-phase four-wire low-voltage power distribution equipment, single-phase and three-phase load have been used mainly mixed. Also linear and nonlinear loads have been used together in the same conditions. In a three-phase four-wire distribution line, the current distribution of three-phase linear load is almost constant in each phase during driving or stopping, but the single-phase load is different from each other for each phase in accordance with the operation and stop. So that the voltage unbalance is caused by the current difference of each phase. In the three-phase four-wire distribution system, non-linear load is used with linear load. The presence of single-phase nonlinear loads can produce an increase in harmonic currents in three-phase and neutral line. It can also cause voltage unbalance. In the present study, we analyzed for the voltage unbalance fluctuations by the operation pattern of the single and three-phase linear and non-linear load in three-phase four-wire low voltage distribution system.

• Proceedings of the Korean Institute of IIIuminating and Electrical Installation Engineers Conference
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• 2009.05a
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• pp.336-339
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• 2009

In this paper, such as battery power or solar energy and fuel cells generated from Renewable energy sources, high voltage to low voltage DC-DC Converter for converting the design of the study. System consists of low voltage ($24{\sim}28$ [VDC]) and Boosts the voltage (270 [VDC]) for a 3 [kW] DC-DC converter and control circuit is configured as, Power switch the ST Tomson's Automotive low voltage high current MOSFET switches STE250NS10S (temperature 250A) was applied to the two parallel. Also, Controller's processor used ATMEGA128, and Gate Drive applies and composed Photo Coupler TLP250. development. Input voltage (24V) and output voltage (270V) for Conversion in the H-bridge converter topology of the circuit output side power and voltage to control the implementation of the Phase shift angle control applied. And, 3kW of power to pass appropriate specification of the secondary side as interpreted by the high frequency transformer, and the experimental production and analysis of the experiment

• Journal of Electrical Engineering and Technology
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• v.10 no.1
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• pp.216-226
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• 2015

The neutral beam injection generate ultra-high temperature energy in the tokamak of nuclear fusion. The neutral beam injection make up arc power supply, filament power supply and acceleration & deceleration power supply. The arc power supply has characteristics of low voltage and high current. Arc power supply generate arc through constant output of voltage and current. So this paper proposed suitable buck converter for low voltage and high current. The proposed buck converter used parallel switch because it can be increased capacity and decrease conduction loss. When an arc generated, the neutral beam injection chamber occur high voltage. And it will break output capacitor of buck converter. Therefore the output capacitor was removed in the proposed converter. Thus the proposed converter should be designed for the characteristics of low voltage and high current. Also, the arc power supply should be guaranteed for system stability. The proposed parallel buck converter enables the system stability of the divided low output voltage and high current. The proposed converter with constant output be the most important design of the output inductor. In this paper, designed arc power supply verified operation of system and stability through simulation and prototype. After it is applied to the 288[kW] arc power supply for neutral beam injection.

• The Transactions of the Korean Institute of Electrical Engineers B
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• v.49 no.12
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• pp.813-820
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• 2000

A technique to suppress the low frequency ripple voltage of the DC output in three phase buck diode converter is presented in this paper. The proposed pulse frequency modulation methods and duty ratio modulation methods are employed to regulate the output voltage of the buck diode converter and guarantee zero-current-switching(ZCS) of the switch over the wide load range. The proposed control methods used in this paper provide generally good performance such as low THD of the input line current and unity power factor. In addition, control methods can be effectively used to suppress the low frequency ripple voltage appeared in the dc output voltage. The harmonic injection technique illustrates its validity and effectiveness through the simulations and experiments.

• Proceedings of the KIEE Conference
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• 1999.07e
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• pp.2326-2328
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• 1999

Developments of effective and economic diagnostic apparatus for industrial plastic insulated high voltage power cables are in discontented condition still. Some report told that DC high voltage was damaged plastic insulation of a partially aged power cable to lead breakdown easily. But now, we have no alternative tools of DC diagnostic apparatus, and we try to reduce a possibility of hazard DC diagnosis. DC diagnostic apparatus still have many advantages to field cable engineer like low price, portability easy applications and sufficient data. Main hazard of DC diagnosis is excessive hight of applied voltage Recent developments for DC diagnosis use considerably low voltage. But new test methods need special measuring device and manipulator, like high input impedance voltmeter, low leakage current high voltage switches, etc. So that reason, new DC diagnostic devices are normally very expensive and have low efficiency, economically. We try to design a composite test device for 3$\sim$4 newly developed method, have economical benefit th industrial engineer.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• 2015.10a
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• pp.458-461
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• 2015

In this paper 2 types of voltage references and a current reference suitable for low-voltage, low-power circuits are proposed and designed with $0.35{\mu}m\;CMOS$ process. MOS transistors operating in weak inversion and bulk-driven technique are utilized to achieve low-voltage and low-power features. The first voltage reference consumes 1.43uA from a supply voltage of 1.2V while it has a reference voltage of 585mV and a TC(Temperature Coefficient) of $6ppm/^{\circ}C$. The second voltage reference consumes 48pW from a supply voltage of 0.3V while having a reference voltage of 172mV and a TC of $26ppm/^{\circ}C$. The current reference consumes 246nA from a supply voltage of 0.75V with a reference current of 32.6nA and a TC of $262ppm/^{\circ}C$. The performances of the designed references have been verified through simulations.

• Journal of IKEEE
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• v.24 no.1
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• pp.364-367
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• 2020

This paper presents the off-grid PV-ESS system of sequential voltage control method applied to OR logic gate. The conventional off-grid PV-ESS system with the low-voltage series connection has problems due to capacity expansion. To solve these problems, this paper proposes a noble PV-ESS system with high efficiency and low cost by applying sequential voltage control technique of the high-voltage series connection of analog circuit type. The input voltage of DC to AC inverter can be converted from the low-voltage by the combinations of series connection of the conventional cascaded 24V solar cell unit modules to the high-voltage of 384V in battery. The output voltage of the battery was 384V as the each input voltage of three phase DC to AC inverter, and the each output voltage of three phase 10kW DC to AC inverter is designed to be AC380V@60Hz as the line to line rms voltage value. To prove the validity of the theoretical analysis by PSIM simulation, the operating characteristics of sequential voltage control system with OR logic gate were confirmed through experiment results.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2009.11a
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• pp.161-161
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• 2009

Ion bombarded inorganic materials for LC alignment has been researched as it provides controllability in a nonstop process for producing high-resolution displays. Many optically transparent insulators such as $SiOx$ and a-C:H have been investigated as potential candidates for inorganic alignment materials. Even so, LC orientation on a new material with superior capacity is required to produce high-performance displays. Many inorganic materials with high permittivities can reduce the voltage losses due to the LC alignment layer that are a trade-off for its capacitance. The minimum voltage for device operation can be applied to the LC under low external voltage using these materials. This means that low power consumption for LCD applications can be achieved using a high-k alignment structure in which the LC can be driven effectively with a low threshold voltage. Among the many other potential high-k oxides, HfO2 is considered to be one of the most promising due to its remarkable properties of high dielectric constant, relatively low leakage current, large band gap (5.68 eV), and high transparency. Due to these characteristics, HfO2 can be used in LC alignment to increase the capacitance of the inorganic alignment layer for low-voltage driving of LCs.