• Journal of Electrical Engineering and Technology
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• 제8권4호
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• pp.694-703
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• 2013

In electric power system, the line stability indices adopted in most of the instances laid stress on variation of reactive power than real power variation of the transmission line. In this paper, a proposal is made with the formulation of a New Voltage Stability Index (NVSI) which originates from the equation of a two bus network, neglecting the resistance of transmission line, resulting in appreciable variations in both real and reactive loading. The efficacy of the index and fuzzy based load flow are validated with IEEE 30 bus and Tamil Nadu Electricity Board (TNEB) 69 bus system, a practical system in India. The results could prove that the identification of weak bus and critical line in both systems is effectively done. The weak area of the practical system and the contingency ranking with overloading either line or generator outages are found by conducting contingency analysis using NVSI.

• 한국전기전자재료학회논문지
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• 제14권11호
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• pp.885-891
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• 2001

Ring/dot-type step-down piezoelectric transformer was manufactured by using Pb[(Mn$\sub$1/3/Sb$\sub$2/3)$\sub$0.05/Zr$\sub$0.475/Ti$\sub$0.475/]O$_3$ ceramics, which have excellent high-power piezoelectric properties. The characteristics of step-down piezoelectric transformer as a function of load resistance at output terminal was examined. Voltage gain was greatly dependent on drive frequency and load resistance, and showed maximum voltage gain at the resonance frequency. The output voltage was linearly increased as the input voltage increased. Voltage gain of the step-down piezoelectric transformer with respect to input voltage was very stable when the load resistance was in the range of 50-500 $\Omega$ .

• 한국전기전자재료학회논문지
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• 제20권4호
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• pp.332-336
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• 2007

In this study, multilayer piezoelectric transformer was manufactured using the PMN-PNN-PZT ceramic and then the electrical characteristics were investigated according to the variations of frequency and load resistance. The voltage step-up ratio of multilayer piezoelectric transformer showed the maximum value at the vicinity of 75 kHz and increased according to the increase of load resistance. When the output impedance coincided with the load resistance, the multilayer piezoelectric transformer showed the temperature rise of less than $20^{\circ}C$ at the output power of 20 W. As the results, the multilayer piezoelectric transformer manufactured at low co-firing temperature of $940^{\circ}C$ using PMN-PNN-PZT ceramics could be stably driven as the step-down transformers.

• 전기학회논문지
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• 제68권1호
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• pp.19-26
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• 2019

As global demand for energy, energy prices, and power generation has increased worldwide, the government is turning to supply-oriented electricity supply and demand policies, such as behavior-based energy efficiency programs. In order to measure the implementation effect of the behavior-based energy efficiency program, the energy reduction must be accurately calculated by calculating the customer baseline load.

• 한국전자통신학회논문지
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• 제17권1호
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• pp.85-90
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• 2022

본 연구에서는 소비자의 부하를 반영하여 실시간 전력품질을 평가할 수 있도록 하는 방법을 개발하였다. 이를 위하여 전력품질 상태를 [Ideal], [Measured], [Acceptable]로 분류하고, Ideal AHP를 사용하여 측정값이 어느 정도인지를 평가할 수 있도록 하였으며, 소비자 부하특성을 반영할 수 있도록 부하를 저항부하, 전동기부하, 전자제품부하로 분류하고 부하의 특성을 반영한 전력품질을 평가할 수 있도록 하였다. 향후, 1:1 행렬과 관련한 심도 있는 연구를 진행하고, 연간단위의 전력품질과 통합하여 종합적인 전력품질 평가를 할 계획이다.

• Journal of Electrical Engineering and Technology
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• 제12권4호
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• pp.1575-1585
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• 2017

This paper presents a synchronous generator with a distributed system of multiple parallel three-phase power cells. This generator can immediately output high DC. Each power cell comprises three-phase windings and a three-phase synchronous rectification bridge with a deadbeat control of load power feedforward, which can improve the characteristics of dynamic response and reflect the load variance in real time. Furthermore, each power cell works well independently and modularly using the method of automatic maximum current sharing. The simulation and experimental results for the distributed controller of multiple power cells demonstrate that the deadbeat control method can respond quickly and optimize the quality of the energy. Meanwhile, automatic maximum current sharing can realize the validity of current sharing among power cells.

• ETRI Journal
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• 제39권3호
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• pp.373-382
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• 2017

A new internally compensated low drop-out voltage regulator based on the cascoded flipped voltage follower is presented in this paper. Adaptive biasing current and fast charging/discharging paths have been added to rapidly charge and discharge the parasitic capacitance of the pass transistor gate, thus improving the transient response. The proposed regulator was designed with standard 65-nm CMOS technology. Measurements show load and line regulations of $433.80{\mu}V/mA$ and 5.61 mV/V, respectively. Furthermore, the output voltage spikes are kept under 76 mV for 0.1 mA to 100 mA load variations and 0.9 V to 1.2 V line variations with rise and fall times of $1{\mu}s$. The total current consumption is $17.88{\mu}V/mA$ (for a 0.9 V supply voltage).

• Journal of KIEE
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• 제10권1호
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• pp.35-42
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• 2000

An equivalent load sharing control based on the frequency and voltage droop concept for parallel operation of two three-phase Uninterruptible Power Supply (UPS) systems with no control interconnection lines is presented in this paper. First of all, due to the use of active power and reactive power as control variables, the characteristics of output powers according to amplitude and phase differences between output voltages of two UPS systems are analyzed. Secondly, simulation results under different line impedance demonstrate the feasibility of the wireless parallel operation control. Finally, experiments are presented to verify the theoretical discussion with two three-phase 20kVA UPS systems employed TMS320C32, a kind of real time digital signal processor (DSP).

• Journal of Electrical Engineering and Technology
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• 제3권3호
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• pp.354-362
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• 2008

In this paper, a new algorithm of optimal voltage control is proposed for the Distribution Automation System (DAS) based on constants of four terminal network modeling. In the proposed method, the voltage profiles along feeders are estimated from the measurement of the current and power factor by a Feeder Remote Terminal Unit (FRTU) installed at each node. Whenever the voltage profile violates the restriction, the voltage control strategy is applied to keep the voltage levels along the feeders within the pre-specified range through the modification and coordination of the transformer under-load tap changers (ULTC), step voltage regulator (SVR), as well as shunt condenser. In the case studies, the estimation and control of the voltages have been testified in a radial distribution system with 11 nodes.

• Journal of Electrical Engineering and Technology
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• 제13권2호
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• pp.580-590
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• 2018

Active distribution system (ADS) considering distributed generation (DG) and electric vehicle (EV) is an effective way to cut carbon emission and improve system benefits. ADS is an evolving, complex and uncertain system, thus comprehensive model and effective optimization algorithms are needed. Battery swapping station (BSS) for EV service is an essential type of flexible load (FL). This paper establishes ADS planning model considering BSS firstly for the minimization of total cost including feeder investment, operation and maintenance, net loss and carbon tax. Meanwhile, immune binary firefly algorithm (IBFA) is proposed to optimize ADS planning. Firefly algorithm (FA) is a novel intelligent algorithm with simple structure and good convergence. By involving biological immune system into FA, IBFA adjusts antibody population scale to increase diversity and global search capability. To validate proposed algorithm, IBFA is compared with particle swarm optimization (PSO) algorithm on IEEE 39-bus system. The results prove that IBFA performs better than PSO in global search and convergence in ADS planning.