• Journal of Electrical Engineering and Technology
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• v.10 no.3
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• pp.766-776
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• 2015

It is well known that series arc faults in Low Voltage DC (LVDC) distribution system occur at unintended points of discontinuity within an electrical circuit. These faults can make circuit breakers not respond timely due to low fault current. It, therefore, is needed to detect the series fault for protecting circuits from electrical fires. This paper proposes a novel scheme to detect the series arc fault using Wavelet Singular Value Decomposition (WSVD) and state diagram. In this paper, the fault detector developed is designed by using three criterion factors based on the RMS value of Singular value of Approximation (SA), Sum of the absolute value of Detail (SD), and state diagram. LVDC distribution system including AC/DC and DC/DC converter is modeled to verify the proposed scheme using ElectroMagnetic Transient Program (EMTP) software. EMTP/MODELS is also utilized to implement the series arc model and WSVD. Simulation results according to various conditions clearly show the effectiveness of the proposed scheme.

• The Proceedings of the Korean Institute of Illuminating and Electrical Installation Engineers
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• v.10 no.5
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• pp.101-107
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• 1996

This paper proposed the voltage compensation analysis method in distribution system by EMTP. SVC (Static Var Compensator) of the thyristor controlled reactor type is used for compensation system. EMTP(E1ectr-o Magnetic Transient Program) model of SVC is proposed to analysis the voltage improvement characteristics at the high voltage system bus. It is composed with three parts ; rms detector, voltage regulator and gate pulse generator. The control signal of TCR is determined by rms value which was measured in system. As the result of EMTP simulation, all of the SVC characteristics like TCR current, firing pulse and bus voltage is very reliable. This method could be used to analysis the planning and the operation of compensation system in the large scale factory.

• Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
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• v.17 no.2
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• pp.10-16
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• 2003

An electronic ballast for driving automotive HID lamps is presented. The circuit topology is composed of a fly back converter, a half bridge inverter, and igniter using voltage doubler. A prototype was developed and tested on a 35W lamp with a 12V input voltage. To avoiding acoustic resonance the half bridge inverter is operated at 400Hz and provided a squared-wave voltage source to the lamp. The transient and steady state characteristics of the tested HID lapm are measured and analyzed.

• The Transactions of the Korean Institute of Power Electronics
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• v.7 no.5
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• pp.499-508
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• 2002

In this paper, a novel wireless parallel operation algorithm of N+l redundant UPS system with no control interconnections for load-sharing is presented. The proposed control system eliminates the sensing noise and interconnections interference of conventional parallel operation system. To reduce a reactive power deviation in wireless control method, this technique automatically compensates for inverter parameter variation and line impedance imbalances with wireless auto-tuning method. In addition, to increase reliability on transient characteristics of parallel operation, a virtual injected impedance is adopted to eliminate a circulation current among inverter modules. Simulation results are provided in this paper to prove the proposed novel wireless algorithm.

• Journal of Information Display
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• v.10 no.2
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• pp.62-67
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• 2009

To understand panel driving more accurately, the optical properties and their distributions in the LCD panel itself, excluding the backlight, were investigated by measuring the transmittance of a one-dot pixel as a function of time. First, the behavior of time-dependent transmittance was analyzed, and it was found that the off-state TFT was not in a steady state but in a transient state during the holding period. Second, the time average, max, min, and range values of the transmittance curves were examined by varying the common voltage level and gray scale. Third, the analysis of such properties was expanded to cover those of the entire panel in all the gray scales. Lastly, the relationship between their properties and distributions was also investigated along with the contour plots.

• Proceedings of the KIPE Conference
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• 2010.07a
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• pp.162-163
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• 2010

본 논문에서는 LED조명의 휘도조절을 위해 PWM dimming시 발생하는 LED전류의 과도 상태제거를 위한 전류 제어 기법을 제안한다. 제안된 LED전류 제어 기법은 과도상태가 존재하지 않으므로 Dimming신호의 동작 시비율이 매우 작은 영역에서도 전류 제어를 통해 낮은 휘도를 정밀하게 표현할 수 있다. 또한 전류의 Overshoot이 발생하지 않으므로 휘도를 일정하게 유지할 수 있는 장점을 가진다. 본 논문에서는 제안된 LED전류 제어 기법의 동작원리를 설명하고, LED휘도 조절을 위한 전원시스템을 구현하여 PSIM 을 통해 제안된 기법의 타당성 및 우수성을 검증한다.

• Journal of Power Electronics
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• v.11 no.4
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• pp.591-598
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• 2011

This paper investigates a power supply of medium voltage with enhanced ignition characteristics for plasma torches. A series resonant half-bridge topology is presented as a suitable ignition circuitry. The ignition circuitry is integrated into the main power conversion system of a multi-phase staggered three-level dc-dc converter with a diode front-end rectifier. A plasma torch rated at 3MW, 2kA and having a physical size of 1m is selected to be the high enthalpy source for a waste disposal system. The steady-state and transient operations of a plasma torch are simulated. The parameters of a Cassie-Mary arc model are calculated based on 3D magneto-hydrodynamic simulations. The circuit simulation waveform shows that the ripple of the arc current can be maintained within ${\pm}10%$ of its rated value under the presence of a load disturbance. This power conversion configuration provides a high enough ignition voltage, around 5KA, during the ignition phase and high arc stability under the existence of arc disturbance noise resulting in a high-performance plasma torch system.

• Journal of Power Electronics
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• v.17 no.5
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• pp.1231-1243
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• 2017

Grid-interactive power converters are normally synchronized with the grid using phase-locked loops (PLLs). The performance of the PLLs is affected by the non-ideal conditions in the sensed grid voltage such as harmonics, frequency deviations and the dc offsets in single-phase systems. In this paper, a single-phase PLL is presented to mitigate the effects of these non-idealities. This PLL is based on the popular second order generalized integrator (SOGI) structure. The SOGI structure is modified to eliminate the effects of input dc offsets. The resulting SOGI structure has a high-pass filtering property. Hence, this PLL is termed as a high-pass generalized integrator based PLL (HGI-PLL). It has fixed parameters which reduces the implementation complexity and aids in the implementation in low-end digital controllers. The HGI-PLL is shown to have the lowest resource utilization among the SOGI based PLLs with dc cancelling capability. Systematic design methods are evolved leading to a design that limits the unit vector THD to within 1% for given non-ideal input conditions in terms of frequency deviation and harmonic distortion. The proposed designs achieve the fastest transient response. The performance of this PLL has been verified experimentally. The results agree with the theoretical prediction.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.16 no.6
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• pp.471-476
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• 2003

Au/oxide/n-InP Schottky diodes were fabricated from heteroepitaxial InP layers grown on GaAs substrates by the metalorganic vapor phase epitaxy (MOVPE) method from a new combination of source materials: ethyldimethylindium (EDMIn) and tertiarybutylphosphine (TBP). Anodic oxidation technique by using a solution of 10 g of ammonium pentaborate in 100 cc of ethylene glycole as the electrolyte was used to deposit a thin oxide layer. The barrier heights determined from three different techniques, current-voltage (I-V) measurements at room temperature and in the temperature range of 273 K - 373 K, and room temperature capacitance-voltage (C-V) measurements are in good agreement, 0.7 - 0.9 eV which is considerably high as compared to the 0.45 - 0.55 eV in Au/n-InP Schottky diode without a Passivation layer. The ideality factors of 1.1 - 1.3 of the Schottky diodes were also determined from the I-Y characteristics. Deep level transient spectroscopy (DLTS) studies revealed only one shallow electron state at 92.6 meV below the bottom of the conduction band and no deep state in the heteroepitaxial InP layers grown from EDMIn and TBP.

• Journal of the Korean Society for Precision Engineering
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• v.26 no.4
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• pp.100-106
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• 2009

The current tendency toward light weight and fast machines has lead to a need to suppress vibration of flexible dynamic systems. Input shaping is an efficient tool to eliminate transient and residual vibration caused by motion of these systems. This paper proposes a new formulation of the design method for multi-mode input shapers to eliminate residual vibration in flexible dynamic systems. The essence of the proposed method is to minimize the number of impulses to be n+1 for n-mode input shapers. This paper also suggests a solution procedure to solve the complex-valued nonlinear matrix equation for the input shapers. The proposed method is applied to two-mode input shapers. This paper discusses characteristics of several input shapers obtained under the same condition. Simulations and experiments show that the proposed method is very useful for designing multi-mode input shapers.