• The Transactions of the Korean Institute of Power Electronics
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• v.11 no.4
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• pp.293-301
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• 2006

This paper proposes a control algorithm for STATic synchronous COMpensator(STATCOM), based on Space Vector Modulation(SVM) and Hysteresis Current Controller(HCC) techniques. STATCOM is used to reactive power compensation on a distribution network. The proposed algorithm utilizes the advantages of the fast dynamic response of the hysteresis current control and the reduced switching number of the SVM scheme. The controller determines a set of space vectors from a region detector and applies a space vector. A set of space vectors including the zero vector, to reduce the number of switching, is determined from output signals of two hysteresis comparators. The presented control system was tested with digital simulation in the Borland C++ program and demonstrate the advantage of the proposed hysteresis current controller.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.23 no.7
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• pp.534-538
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• 2010

X-ray systems for medical treatment use noninvasive procedures. Being capable of locally inspecting the inside of the body, X-ray systems are routinely used for basic diagnosis. X-ray systems to be used for medical purposes were originally made with a gas filled tube inside an induction coil in the initial stages of development but with this approach it becomes difficult to take a satisfactory picture through thick body sections, non invasively. However continued development made it possible to take non-invasive pictures of breasts, blood vessels and other body parts through thick body sections. Recently, high-voltage X-ray generators of more compact size, increased generation efficiency, and sophisticated output control have become possible. All of these features are made possible by the use of a high-frequency output from an inverter and a fast switching semiconductor device. In this paper, we describe a new X-ray generator operating with a resonant inverter in order to reduce switching loss and high frequency noise. In addition, in order to identify the differences amongst types of rectification, we have compared output and the quality of X-ray pictures obtained with full-wave rectification and dual-voltage rectification methods.

• Journal of Korea Multimedia Society
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• v.16 no.1
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• pp.75-86
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• 2013

This paper presents a technique to implement embedded systems using interrupts of the one-chip microcontroller with many peripherals based on a multiple finite state machines model. The multiple finite state machine model utilizes the structure of FSMD used for hardware design and the features of flow control by interrupts. The main finite state machine corresponds to the main program and the sub-state machines corresponds to the interrupt subroutines. Therefore, interrupts from the peripherals can be processed immediately in the sub-state machines. The request and reply variables are used to interface between the finite state machines. Additional operating system is not necessary for the context switching between the main state machine and the sub-state machine, because the flow-control caused by interrupt can be replaced with the switching. An embedded system modeled on multiple finite state machine with ASM charts can be easily implemented by the conversion of ASM charts into C-language programs. This implementation technique can be easily adopted to the hardware oriented embedded systems because of the detail description of the model and the fast response to the interrupt events in the sub-state machine.

• Journal of Ceramic Processing Research
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• v.20 no.5
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• pp.484-489
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• 2019

VO2 is an attractive candidate as a transition metal oxide switching material as a selection device for reduction of sneak-path current. We demonstrate deposition of nanoscale VO2 thin films via thermal atomic layer deposition (ALD) with H2O reactant. Using this method, we demonstrate VO2 thin films with high-quality characteristics, including crystallinity, reproducibility using X-ray diffraction, and X-ray photoelectron spectroscopy measurement. We also present a method that can increase uniformity and thin film quality by splitting the pulse cycle into two using scanning electron microscope measurement. We demonstrate an ON / OFF ratio of about 40, which is caused by metal insulator transition (MIT) of VO2 thin film. ALD-deposited VO2 films with high film uniformity can be applied to next-generation nonvolatile memory devices with high density due to their metal-insulator transition characteristic with high current density, fast switching speed, and high ON / OFF ratio.

• The Journal of the Institute of Internet, Broadcasting and Communication
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• v.22 no.2
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• pp.123-128
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• 2022

The torque of the SRM((Switched Reluctance Motor)) is proportional to the inductance slope, so it has a non-linear torque characteristic, and has a disadvantage in that the torque pulsation is large and noise is severe. In particular, the biggest obstacle to the commercialization of SRM is the pulsating torque generated from the rotating shaft, which has various adverse effects not only on the device itself but also on the peripheral devices. Therefore, various methods for reducing the pulsating torque have been published by domestic and foreign researchers, and there is a study result that the hysteresis controller has an advantage in that it can flow a smooth current compared to the chopping control. However, in determining the hysteresis band, if the band is too small, it has a disadvantage in that it may cause a switching loss due to many switching and an unstable initial start when the encoder is used. Therefore, in this paper, a variable hysteresis controller that can reduce torque ripple in a steady state while having a more stable and fast speed response through the change of the hysteresis band according to the speed error.

• Journal of Korea Society of Industrial Information Systems
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• v.27 no.5
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• pp.25-36
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• 2022

This paper proposes a random sign reversal technique in space frequency block code for single carrier modulation. The traditional space time and frequency block coding technique may be confronted with radio environments openly, severe radio hijacking problems are to be overcome. In order to avoid such an open radio issue, random coded data protection technique for space-time block code was proposed, but this algorithm can change channel combination per an Orthogonal Frequency Division Multiplexing block. This kind of slow switching increases the probability that nearby receivers will detect the transmitted data. This paper proposes a fast switching algorithm per data symbols' basis which is a random sign reversal technique in space frequency block code for Single Carrier Modulation. It is shown in simulation that the proposed one has a superior performance in comparison with the performance of the receiver which do not know the random timing sequence of sign reversal.

• Asia-pacific Journal of Multimedia Services Convergent with Art, Humanities, and Sociology
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• v.8 no.6
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• pp.939-946
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• 2018

In this work, we present simple schematics for a three-terminal graphene-based nanoelectromechanical switch with the vertical electrode, and we investigated their operational dynamics via classical molecular dynamics simulations. The main structure is both the vertical pin electrode grown in the center of the square hole and the graphene covering on the hole. The potential difference between the bottom gate of the hole and the graphene of the top cover is applied to deflect the graphene. By performing classical molecular dynamic simulations, we investigate the nanoelectromechanical properties of a three-terminal graphene-based nanoelectromechanical switch with vertical pin electrode, which can be switched by the externally applied force. The elastostatic energy of the deflected graphene is also very important factor to analyze the three-terminal graphene-based nanoelectromechanical switch. This simulation work explicitly demonstrated that such devices are applicable to nanoscale sensors and quantum computing, as well as ultra-fast-response switching devices.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.19 no.3
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• pp.567-574
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• 2015

In this paper, a 50ns 256-kb EEPROM IP for MCU (micro controller unit) ICs is designed. The speed of data sensing is increased in the read mode by using a proposed DB sensing circuit of differential amplifier type which uses the reference voltage, and the switching speed is also increased by reducing the total DB parasitic capacitance as a distributed DB structure is separated into eight. Also, the access time is reduced reducing a precharging time of BL in the read mode removing a 5V NMOS transistor in the conventional RD switch, and the reliability of output data can be secured by obtaining the differential voltage (${\Delta}V$) between the DB and the reference voltages as 0.2*VDD. The access time of the designed 256-kb EEPROM IP is 45.8ns and the layout size is $1571.625{\mu}m{\times}798.540{\mu}m$ based on MagnaChip's $0.18{\mu}m$ EEPROM process.

• The Transactions of the Korean Institute of Power Electronics
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• v.8 no.1
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• pp.24-29
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• 2003

A 120kV/70A high voltage switch has been installed at Korea Atomic Energy Research Institute(KAERI) in Taejon to supply power with Korea Superconducting Tokamak Advanced Research(KSTAR) Neutral Beam Injection(NBI) system. NBI system requires fast cutoff of the flower supply voltage for protection of the grid when arc detected and fast turn-on the voltage for sustaining the beam current. Therefore the high voltage switch and arc current detection circuit are important part of the NBI power supply. There are much need for high voltage solid state switches in NBI system and a broad area of applications. This switch consisted of 100 series connected MOSFETs and adopted the proposed simple and reliable gate drive circuit without bias supply. Various results taken during the commissioning phase with a 100kW resistive load and NBI source arc shown. This paper presents the detailed design of 120kV/70A high voltage MOSFETs switch and simple gate drive circuit. Problems with the high voltage switch and gate driver during thefabrication and test and solutions are also presented.

• Journal of Power Electronics
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• v.17 no.1
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• pp.56-66
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• 2017

Fast and accurate fault detection is the primary step and one of the most important tasks in fault tolerant converters. In this paper, a fast and simple method is proposed to detect and diagnosis the faulty cell in a cascaded H-bridge multilevel inverter under a short circuit fault. In this method, the reference voltage is calculated using switching control pulses and DC-Link voltages. The comparison result of the output voltage and the reference voltage is used in conjunction with active cell pulses to detect the faulty cell. To achieve this goal, the cell which is active when the Fault signal turns to "0" is detected as the faulty cell. Furthermore, consideration of generating the active cell pulses is completely described. Since the main advantage of this method is its simplicity, it can be easily implemented in a programmable digital device. Experimental results obtained with an 11-level inverter prototype confirm the effectiveness of the proposed fault detection technique. In addition, they show that the diagnosis method is unaffected by variations of the modulation index.