• 전자공학회논문지 IE
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• v.48 no.3
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• pp.10-15
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• 2011

In the case of designing an acoustic transducer for high power application, we usually aim to transfer the source electric energy to the output acoustic energy as large as possible. For this purpose, we should match the impedance of the power amplifier to the impedance combined with the acoustic transducer impedance and the radiation impedance. Especially if we have electrical source with almost zero impedance, we need improve the power factor of the acoustic transducer in the load. In this paper, we propose a broad band impedance matching method by the improvement of power factor, which applies ABCD matrix.

• The Transactions of the Korean Institute of Power Electronics
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• v.2 no.1
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• pp.33-38
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• 1997

Generally, various semiconductor switching devices for power systems are used in battery chargers for electric vehicle. When these used, it takes the problems of transient-current or distortion of waveforms in power systems near by battery chargers because of harmonics and large peak-current, low power factor, etc., caused by the non-linearity of these devices. Recently, power factor control, line current peak-cut, harmonics reduction which was ignored in past is more and more important. In this paper, to solve those problems we will improve the characteristics of voltage rising and propose the high power factor converter circuit for battery chargers. Our proposed system convert commutated voltage to AC resonant wave in high frequency inverter and rectify the link voltages passed high-frequency transformer and transfer the DC voltages. Especially, the effect using these converter system can be improved very large by power factor control and we have to verify the possibilities of improvement through the experiment of Pb-Acid battery application.

• Proceedings of the IEEK Conference
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• 2002.06e
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• pp.311-314
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• 2002

In recent years, various power factor correction(PFC) circuits for the electronic ballasts have been proposed. In this paper, we have studied several passive PFC and compared with their characteristics, used in the electronic ballast for fluorescent. Especially, Improved Valley Fill Circuit (IVF) and the circuit IVF PFC combined with Charge Pumping Capacitors(CPCs) have been reaserched for High Power Factor. In conclusion, we have researched characteristics of Passive PFC and proposed the most effective PFC method.

• Journal of Power Electronics
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• v.7 no.4
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• pp.318-327
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• 2007

The design and performance analysis of a power factor corrected (PFC), single-phase, single switch flyback buck-boost ac-dc converter is carried out for low power battery charging applications. The proposed configuration of the flyback buck-boost ac-dc converter consists of only one switch and operates in discontinuous current mode (DCM), resulting in simplicity in design and manufacturing and reduction in input current total harmonic distortion (THD). The design procedure of the flyback buck-boost ac-dc converter is presented for the battery charging application. To verify and investigate the design and performance, a simulation study of the flyback buck-boost converter in DCM is performed using the PSIM6.0 platform. A laboratory prototype of the proposed single switch flyback buck-boost ac-dc converter is developed and test results are presented to validate the design and developed model of the system.

• Proceedings of the KIPE Conference
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• 2010.07a
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• pp.536-537
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• 2010

If DC voltage adjustment can be controlled very easily, it is much more effective rather than AC in transmission efficiency. The main reason why DC is more effective than AC, DC has the same role as the 70[%] of AC whenever the same power send. In addition, AC streams the surface of electrical wire, but DC streams overall of electrical wire. Digital load, which is operated by DC, has increased in modern times. The step of convert of AC-DC has to be reduced. When we turn the dispersed AC-DC converters into the concentrated AC-DC converter, it can improve the effective of the whole system. Further more, if digital society develops more than now and the time of electric vehicle comes, the need of DC will increase much more than these days. This paper suggests that DC output of distributed power source and high efficient 3 phase PWM converter can control the adjustment of output voltage, harmonic restraint, power factor improvement and dump power.

• The Transactions of the Korean Institute of Electrical Engineers
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• v.34 no.2
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• pp.47-55
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• 1985

In this paper, a multiple pulse-width modulated ac chopper mode power controller using power transistor is described. The controller is capable of handling up to 1/2 hp of power at any lagging load power factor angle and getting the optimal efficiency operating characteristics. The development, study, and experimental evaluation of the controller with induction motor load is described.

• Proceedings of the KIEE Conference
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• 1999.07f
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• pp.2613-2615
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• 1999

In the paper, a new single phase uninterruptible power supply(UPS) scheme is proposed. A conventional UPS can supply power to the load continuously. However, it may generate input current harmonics and the input power factor is very poor. This paper proposes a phase control converter for single phase UPS. It mainly consists of a minimized structure of power converter which is capable of providing a specified constant output voltage, phase controlled battery charger. The proposed scheme is validated with a computer simulation.

• Proceedings of the KIEE Conference
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• 2002.11b
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• pp.41-43
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• 2002

The contracted electric power and the demand factor of customers are used to predict the peak load in distribution transformers. The conventional demand factor was determined more than ten years ago. The contracted electric power and power demand have been increased. Therefore, we need to prepare the novel demand factor that appropriates at present. In this paper, we modify the demand factor to improve the peak load prediction of distribution transformers. To modify the demand factor, we utilize the 169 data acquisition devices for sample distribution transformers in winter, spring summer. And, the peak load currents were measured by the case studies using the actual load data, through which we verified that the proposed demand factors were correct than the conventional factors. A newly demand factor will be used to predict the peak load of distribution transformers.

• Journal of Electrical Engineering and Technology
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• v.12 no.4
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• pp.1340-1347
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• 2017

Utilization of Electric Vehicles (EVs) have been growing popularity in recent years due to increment in fuel price and lack of natural resources. Random unexpected charging by home EV charger in distribution is predicted in the future. The power quality problems such as fluctuation of power factor in a residential distribution network was explored with random EV chargers. This paper proposes a high-performance nonlinear sliding mode controller (SMC) for an EV charging system to compensate voltage distortions and to enhance the power factor against the unbalanced EV chargers. For the verification of the proposed scheme, MATLAB-Simulink simulations are performed on 22.9-kV grid. The results show that the proposed scheme can improve the power factor of a smart grid due to the EV chargers on the grid.

• The Transactions of the Korean Institute of Electrical Engineers B
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• v.52 no.7
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• pp.343-351
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• 2003

In this paper, interleaved boost converter is applied as a first-stage converter in switch mode power supply. The first-stage converter plays a role to improve power factor. Interleaved Boost Power Factor Corrector(IBPFC) can reduce input current ripple as a single voltage control loop only without inner current loop, because input current is divided each 50% by two switching devices. Each converter cell is also operated in discontinuous current mode and inductor current of each converter is discontinuous. Total input current which is composed by each converter cell is continuous current. Thus, IBPFC is able to improve input current ripple. IBPFC operating in discontinuous current mode can be classified as six modes from switching state and be carried out state space averaging small signal modeling. A control transfer function is obtained according to the modeling. Not only steady-state characteristics but also dynamic characteristics is considered. Single voltage control loop is also constructed by the control transfer function. From experimental result, improvement of power factor and input current ripple are verified.