• International journal of advanced smart convergence
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• v.9 no.2
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• pp.105-113
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• 2020

In this paper, we proposed a soft switched synchronous boost converter, which can perform discharging the battery, is proposed. The proposed converter has low switching loss even at high frequency operation due to its soft switching characteristics. The converter operates in synchronous mode to minimize conduction loss because of changing the rectified diode to MOSFET with a low on resistance. In this reason, the efficiency of the converter can be greatly improved in high frequency. In this paper, the battery discharger with a switching frequency of 100 kHz, has been designed. The designed converter also simulated to prove the converter's characteristics of synchronous operation as well as soft switching operation. The simulation shows that the proposed converter always meets the soft switching conditions of turning on and off switching in the zero voltage and zero current states. Therefore, simulation results have confirmed that the proposed battery discharge had soft switching characteristics. The simulation results have confirmed that the proposed battery discharger had soft switching and synchronous operation characteristics.

• Journal of Power Electronics
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• v.18 no.3
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• pp.879-891
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• 2018

A bidirectional dc-dc converter is used in battery energy storage systems owing to the growing requirements of a charging and discharging mode of battery. The magnetic coupling of output or input inductors in parallel-connected multi modules of a bidirectional dc-dc converter is often utilized to reduce the peak-to-peak ripple size of the inductor current. This study proposes a novel design guideline to achieve minimal ripple size of the inductor current under bidirectional power flow. The newly proposed design guideline of optimized coupling factor is applicable to the buck and boost operation modes of a bidirectional dc-dc converter. Therefore, the coupling factor value of the coupled inductor does not have to be optimized separately for buck and boost operation modes. This new observation is explained using the theoretical model of coupled inductor and confirmed through simulation and experimental test.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2005.11a
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• pp.279-280
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• 2005

We have designed a single gap transflective liquid crystal display (LCD) driven by a fringe electric field and vertical field. The conventional FFS mode does not have an electrode on top substrate, it shows not only slow response time due to weak electric field but also slow discharging problem when electrostatic field is generated after fabricating the cell. To solve these problems, transflective LCD with ITO coated upper substrate was suggested but the transmittance was reduced significantly due to effects from vertical field. Hence, in the present paper, new transflective LCD with ITO coating only in the reflective region was characterized.

• The Transactions of the Korean Institute of Electrical Engineers
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• v.34 no.6
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• pp.213-219
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• 1985

Superconducting Magnetic Energy Storage (SMES) system can be used for power system stabilization by absorbing or discharging active and reactive power through thyristor-comtrolled converters. In this paper, we have proposed a control algorithm that the active and reactive powers of SMES are simultaneously controlled to increase power system dynamic stability. The proposed method was applied to one machine-infinite and three machines and three load model systems. And it has been shown that the proposed algorithm is more effective in power system stabilization than the conventional one that only the active power of SMES is controlled. Eigenvalue sensitivity analysis method is introduced to estimate the optimal location of SMES in the sense of the power system oscillation mode.

• Journal of Power Electronics
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• v.16 no.1
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• pp.133-141
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• 2016

This paper focuses on the development of a Five-Level Flying-Capacitor Dual Buck Inverter (FLFCDBI) based on the main circuit of dual buck inverters. This topology has been described as not having any shoot-through problems, no body-diode reverse recovery problems and the half-cycle work mode found in the traditional Multi-Level Flying-Capacitor Inverter (MLFCI). It has been shown that the flying-capacitor voltages of this inverter can be regulated by the redundant state selection within one pole. The voltage balance of the flying-capacitors can be achieved by charging or discharging in the positive (negative) half cycles by choosing the proper logical algorithms. This system has a simple structure but demonstrates improved performance and reliability. The validity of this inverter is conformed through computer-aided simulation and experimental investigations.

• Journal of Power Electronics
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• v.14 no.3
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• pp.458-467
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• 2014

In this paper, a single-phase current-source bidirectional converter topology for V2G applications is proposed. The proposed converter consists of a single-phase current-source rectifier (SCSR) and an auxiliary switching network (ASN). It offers bidirectional power flow between the battery and the grid in the buck or boost mode and expands the output voltage range, so that it can be compatible with different voltage levels. The topology structure and operating principles of the proposed converter are analyzed in detail. An indirect control algorithm is used to realize the charging and discharging of the battery. Finally, the semiconductor losses and system efficiency are analyzed. Simulation and experimental results demonstrate the validity and effectiveness of the proposed topology.

• Proceedings of the KIPE Conference
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• 2012.07a
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• pp.431-432
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• 2012

The proposed dc-dc convertor for a battery energy storage system(BESS) can reduce the power rating and bidirectional power flow. This system consist soft-switching bidirectional dc-dc converter so it can reduce the energy loss when charging and discharging mode. Thus it can achieve high efficiency. Also, overall system utilizes the voltage compensation circuit. It is composed of small size and low cost due to reducing the power rating. In this paper, we proposed system about verified by simulation.

• Journal of the Korean Society of Safety
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• v.9 no.4
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• pp.132-136
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• 1994

The new spray system is proposed by using a pipe with hygroscopic needle electrode In order to develop an air-cleaning ESP with high collection efficiency for submicron particles and high removal efficiency for NOx, SO$_2$, NH$_3$. Fundamental characteristics of charging water spray, which is not an usual wet type, are investigated experimentally. As a result, corona discharging mode and ozone generation rate are significantly affected by the operational conditions, such as the applied voltage and wet condition of the needle electrode.

• The Transactions of the Korean Institute of Power Electronics
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• v.16 no.5
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• pp.440-447
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• 2011

This paper deals with supercapacitor energy storage system for the compensation of the slow response characteristics of a fuel cell generation system for grid connection. A bidirectional dc/dc converter is used for the charging and discharging of the supercapacitor. The conventional converters use additional clamping circuit, etc. to reduce a voltage spike at the instant of switching and to provide wide range of soft switching. The proposed method provides simplified hardware implementation without any clamping circuit, and soft switching condition for both charging and discharging mode with proper switching patterns. The usefulness of the proposed scheme is verified through simulation and experimental results with 1 kW system.

• JSTS:Journal of Semiconductor Technology and Science
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• v.8 no.2
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• pp.128-133
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• 2008

Phase-change random access memory (PRAM) chip cell phase of amorphous state is rapidly changed to crystal state above 160 Celsius degree within several seconds during Infrared (IR) reflow. Thus, on-board programming method is considered for PRAM chip programming. We demonstrated the functional 512Mb PRAM with 90nm technology using several novel core circuits, such as metal-2 line based global row decoding scheme, PN-diode cells based BL discharge (BLDIS) scheme, and PMOS switch based column decoding scheme. The reverse-state standby current of each PRAM cell is near 10 pA range. The total leak current of 512Mb PRAM chip in standby mode on discharging state can be more than 5 mA. Thus in the proposed BLDIS control, all bitlines (BLs) are in floating state in standby mode, then in active mode, the activated BLs are discharged to low level in the early timing of the active period by the short pulse BLDIS control timing operation. In the conventional sense amplifier, the simultaneous switching activation timing operation invokes the large coupling noise between the VSAREF node and the inner amplification nodes of the sense amplifiers. The coupling noise at VSAREF degrades the sensing voltage margin of the conventional sense amplifier. The merit of the proposed sense amplifier is almost removing the coupling noise at VSAREF from sharing with other sense amplifiers.