• The Transactions of the Korean Institute of Power Electronics
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• v.26 no.3
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• pp.176-182
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• 2021

This research proposes a high-frequency circuit that can accurately predict the differential mode noise of single-phase inverters at the circuit design stage. Proposed single-phase inverter high frequency circuit in the work is a form in which harmonic impedance components are added to the basic single-phase inverter circuit configuration. For accurate noise prediction, parasitic components present in each part of the differential noise path were extracted. Impedance was extracted using a network analyzer and Q3D in the measurement range of 150 kHz to 30 MHz. A high-frequency circuit model was completed by applying the measured values. Simulations and experiments were conducted to confirm the validity of the high-frequency circuit. As a result, we were able to predict the resonance point of the differential mode voltage extracted as an experimental value with a high-frequency circuit model within an approximately 10% error. Through this outcome, we could verify that differential mode noise can be accurately predicted using the proposed model of the high-frequency circuit without a separate test bench for noise measurement.

• The Transactions of the Korean Institute of Power Electronics
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• v.20 no.1
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• pp.51-58
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• 2015

In order to decrease the size of a switch mode power supply, high switching frequency can be an efficient way to reduce the size of passive components in the converter. In this paper, a 500-kHz high-frequency LLC resonant converter is proposed with an accurate design method of magnetizing inductance, as well as the relationship between the switching frequency and the size of the passive components. Simulation and experimental results are presented to verify the proposed methods and equations, including the temperature data of each passive and active device of the converter. Using those results, dominant power losses in the prototype converter under 500-kHz high-frequency operation are investigated, compared with the results from a 100-kHz converter. In addition, operating waveforms and power conversion efficiency will be shown to obtain design considerations for the high switching frequency LLC resonant converter.

• The Transactions of The Korean Institute of Electrical Engineers
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• v.66 no.6
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• pp.898-904
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• 2017

DFT(Discrete Fourier Transform) is one of the most widely used method to estimate the phasor of a relaying signal. The harmonics are eliminated by the DFT. However, high frequency components, except for harmonics, are not removed and cause an error in DFT-based phasor estimation process. This paper suggests high frequency noise reduction method by using a newly designed low-pass filter to estimate a signal phasor. When selecting a stop-band cut-off frequency of the low-pass filter, high frequency components generated by faults are considered. To reduce the phasor estimation delay caused by a low-pass filter, this paper proposes a low-pass filter whose settling time is reduced. An adverse effect of high frequency noise on DFT-based phasor estimation is reduced. To evaluate the performance of the proposed method, signals which are collected under a fault condition at a 345[kV] transmission system modeled by EMTP-RV are used.

• Proceedings of the IEEK Conference
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• 1999.11a
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• pp.1113-1116
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• 1999

In this papers, we proposes a efficient compression method of an image using the extraction of boundary region of DCT in MPEG-1. DCT coefficients have from low frequency to high frequency various components. After performing DCT to an image, the data is compressed to contain the boundary Region by quantization, and the information of boundary Region can be extracted by inverse DCT. In those, I chose frequency components susceptible to the boundary through the many experiences. In this paper, boundary can be selected by dividing low frequency by big quantization coefficient and dividing high frequency by small quantization coefficient without degrading visual qualify in MPEG-1. Also it is predicted that to reduce high frequency value will be good in noisy environments.

• Smart Structures and Systems
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• v.31 no.2
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• pp.155-169
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• 2023

The quasi-static component of the moving vehicle-induced dynamic response is promising in damage detection as it is sensitive to bridge damage but insensitive to environmental changes. However, accurate extraction of quasi-static component from the dynamic response is challenging especially when the vehicle velocity is high. This paper proposes an adaptive quasi-static component extraction method based on the modified variational mode decomposition (VMD) algorithm. Firstly the analytical solutions of the frequency components caused by road surface roughness, high-frequency dynamic components controlled by bridge natural frequency and quasi-static components in the vehicle-induced bridge response are derived. Then a modified VMD algorithm based on particle swarm algorithm (PSO) and mutual information entropy (MIE) criterion is proposed to adaptively extract the quasi-static components from the vehicle-induced bridge dynamic response. Numerical simulations and real bridge tests are conducted to demonstrate the feasibility of the proposed extraction method. The results indicate that the improved VMD algorithm could extract the quasi-static component of the vehicle-induced bridge dynamic response with high accuracy in the presence of the road surface roughness and measurement noise.

• Journal of Power Electronics
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• v.6 no.1
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• pp.73-82
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• 2006

Plasma display panels (PDPs) have a serious thermal problem, because the luminance efficiency of a conventional PDP is about 1.5 1m/W and it is less than $3\~5\;lm/W$ of a cathode ray tube (CRT). Thus there is a need for improving the luminance efficiency of the PDP. There are several approaches to improve the luminance efficiency of the PDP and we adopted a driving PDP at high frequency range from 400kHz up to over 700kHz. Since a PDP is regarded as an equivalent inherent capacitance, many types of sustaining drivers have been proposed and widely used to recover the energy stored in the PDP. However, these circuits have some drawbacks for driving PDPs at high frequency ranges. In this paper, we investigate the effect of the parasitic components on the PDP itself and on the driver when the reactive energy of the panel is recovered. Various drivers are classified and evaluated based on their suitability for high frequency drivers. Finally, a current-fed driver with a DC input voltage bias is proposed. This driver overcomes the effect of parasitic components in the panel and driver. It fully achieves a ZVS of all full-bridge switches and reduces the transition time of the panel polarity. It is tested to validate the high frequency sustaining driver and the experimental results are presented.

• Proceedings of the Korean Vacuum Society Conference
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• 2014.02a
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• pp.292-292
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• 2014

Wide band gap semiconductors, such as III-nitrides (GaN, AlN, InN, and their alloys), SiC, and diamond are expected to play an important role in the next-generation electronic devices. Specifically, GaN-based high electron mobility transistors (HEMTs) have been targeted for high power, high frequency, and high temperature operation electronic devices for mobile communication systems, radars, and power electronics because of their high critical breakdown fields, high saturation velocities, and high thermal conductivities. For the stable operation, high power, high frequency and high breakdown voltage and high current density, the fabrication methods have to be optimized with considerable attention. In this study, low ohmic contact resistance and smooth surface morphology to AlGaN/GaN on 2 inch c-plane sapphire substrate has been obtained with stepwise annealing at three different temperatures. The metallization was performed under deposition of a composite metal layer of Ti/Al/Ni/Au with thickness. After multi-layer metal stacking, rapid thermal annealing (RTA) process was applied with stepwise annealing temperature program profile. As results, we obtained a minimum specific contact resistance of $1.6{\times}10^{-7}{\Omega}cm2$.

• The Transactions of the Korean Institute of Power Electronics
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• v.26 no.4
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• pp.271-276
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• 2021

Arc fault detector based on multilevel DWT with analysis of high-frequency noise components over 100 kHz is proposed in this study to improve the performance in detecting serial arcs and distinguishing them from inverter noise in PV systems. PV inverters generally operate at a frequency range of 20-50 kHz for switching operation and maximum power tracking control, and the effect of these frequency components on the signal for arc detection leads to negative arc detection. High-speed ADC and multilevel DWT are used in this study to analyze frequency components above 100 kHz. Such high frequency components are less influenced by inverter noise and utilized to detect as well as separate DC series arc from inverter noise. Arc detectors identify the input current of PV inverters using a Rogowski coil. The sensed signal is filtered, amplified, and used in 800kSPS ADC and DWT analysis and arc occurrence determination in DSP. An arc detection simulation facility in UL1699B was constructed and AFD tests the proposed detector were conducted to verify the performance of arc detection and performance of distinction of the negative arc. The satisfactory performance of the arc detector meets the standard of arc detection and extinguishing time of UL1699B with an arc detection time of approximately 0.11 seconds.

• Nuclear Engineering and Technology
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• v.51 no.5
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• pp.1470-1476
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• 2019

The nuclear power plants in South Korea have been designed in accordance with the U.S. Regulatory Guide 1.60 (R.G 1.60) design spectrum of which the peak frequency range is 2-10 Hz. The characteristics of the earthquakes at the Korea nuclear power plant sites were observed to be closer to that of Central and Eastern United States (CEUS) than the R.G 1.60, which is a lower amplification in a low frequency range, and a higher amplification in a high frequency range. The possibility of failure for sensitive power plant components in the high frequency range has been considered and evaluated. In this study, in order to improve the reliability of nuclear plant and administrative control procedures, seismic tests of an emergency diesel generator (EDG) were conducted using a shaking table under both high and low frequency ranges. From the tests, oil/lubricant leaks from the bolt connections, the fuel filter and the fuel inlet were observed. Therefore, the check list of nuclear plant components after an earthquake should include bolt connections of EDG as well as anchor bolts.

• Proceedings of the Earthquake Engineering Society of Korea Conference
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• 2000.04a
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• pp.97-104
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• 2000

Evaluating a Review-Level Ground Motion is a key to efficiently perform Seismic Margin Assessment of nuclear power plants whose purpose is to determine a ground motion level for which a plant has high-confidence-of-a-low-probability of seismic-induced core damage and to identify any weaker-link components. In this study a method to obtain RLGMs is reviewed which is recommended by Electric Power Research Institute and implemented to be applied to Limerick site in eastern and central U. S as a case study. This method provides reasonable and site-specific RLGMs as minimum required plant HCLPF for SMA that meet a target mean seismic core-damage frequency based on seismic hazard results and generic values of uncertainty and randomness parameters of the core-damage fragility curves. In addition high-frequency RLGM is justifiably modified to reflect the increased seismic capacity of high-frequency components and spatial variation and incoherence of input ground motion on a basemat of large structures by establishing a method to obtain high0-frequency reduction factors according to EPRI guidelines.