• 한국초전도학회:학술대회논문집
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• 한국초전도학회 2006년도 High Temperature Superconductivity Vol.XVI
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• pp.69-69
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• 2006

• 전력전자학회:학술대회논문집
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• 전력전자학회 2013년도 전력전자학술대회 논문집
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• pp.337-338
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• 2013

Combination the several type of single phase power conversion utilized simply topology are proposed in this paper. Totally four kind of converter are investigated, they are Boost AC/AC Converter, Buck AC/AC Converter, Boost AC/DC Converter, and Buck DC/AC Converter. Two types action mode are presented to determine the functional of circuit. First is AC chopper action mode, representation of the AC/AC converter. AC chopper action mode offered the sinusoidal current waveform, better power factor, faster dynamics, and smaller input/output filter. They present high robustness, offer safe commutation and have high efficiency. The second is full bridge action mode, determined the transformation AC to DC power and otherwise. Four switching devices and one magnetic contactor will establish the mode operation of circuit and manage the flow of power proceed in proper. The correction and advance of the kind of converter are verified by simulation.

• Journal of Power Electronics
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• 제14권6호
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• pp.1293-1302
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• 2014

A flyback inverter using voltage sensorless maximum power point tracking (MPPT) for photovoltaic (PV) AC modules is presented. PV AC modules for a power rating from 150 W to 300 W are generally required for their small size and low price because of the installation on the back side of PV modules. In the conventional MPPT technique for PV AC modules, sensors for detecting PV voltage and PV current are required to calculate the PV output power. However, system size and cost increase when the voltage sensor and current sensor are used because of the addition of the auxiliary circuit for the sensors. The proposed method uses only the current sensor to track the MPP point. Therefore, the proposed control method overcomes drawbacks of the conventional control method. Theoretical analysis, simulation, and experiment are performed to verify the proposed control method.

• 전력전자학회논문지
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• 제12권5호
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• pp.378-385
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• 2007

AC PDP(Plasma Display Panel)는 소비전력이 크고 유지구동전압이 높다는 단점이 있다. 이런 단점을 개선하기 위하여 에너지 회수회로를 설치하고 유지구동전압을 낮춘 회로가 제안되었다. 그러나 이 회로는 방전유지 구간 시작 시점에서 패널의 전압이 방전유지구동전압보다 낮기 때문에 스위칭소자들이 하드 스위칭 동작을 하는 단점이 있다. 본 논문에서는 CIM(Current Injection Method)을 이용하여 미리 인덕터에 전류를 흘려주어 방전유지 구간 시작 시점에서도 스위칭소자들이 영전압 스위칭동작을 하여 전 구간에서 영전압 스위칭 또는 영전류 스위칭동작을 할 수 있는 새로운 구동방식을 제안한다. 그리고 회로를 해석하여 CIM 구간을 설계하고 시뮬레이션과 실험을 통하여 유용성을 입증하였다.

• Journal of Power Electronics
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• 제8권4호
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• pp.332-344
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• 2008

High frequency AC (HFAC) power distribution systems delivering power through a high frequency AC link with sinusoidal voltage have the advantages of simple structure and high efficiency. In a multiple module system, where multiple resonant inverters are paralleled to the high frequency AC bus through connection inductors, it is necessary for the output voltage phase angles of the inverters be controlled so that the circulating current among the inverters be minimized. However, the phase angle of the resonant inverters output voltage can not be controlled with conventional phase shift modulation or pulse width modulation. The phase angle is a function of both the phase of the gating signals and the impedance of the resonant tank. In this paper, we proposed a pulse phase modulation (PPM) concept for the resonant inverters, so that the phase angle of the output voltage can be regulated. The PPM can be used to minimize the circulating current between the resonant inverters. The mechanisms of the phase angle control and the PPM were explained. The small signal model of a PPM controlled half-bridge resonant inverter was analyzed. The concept was verified in a half bridge resonant inverter with a series-parallel resonant tank. An HFAC power distribution system with two resonant inverters connected in parallel to a 500kHz, 28V AC bus was presented to demonstrate the applicability of the concept in a high frequency power distribution system.

• Journal of Power Electronics
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• 제16권6호
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• pp.2129-2138
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• 2016

The full-bridge inverter, widely used for single-phase photovoltaic grid-connected applications, presents a leakage current issue. Therefore, an AC bypass branch is introduced to overcome this challenge. Nevertheless, existing modulation strategies entail drawbacks that should be addressed. One is the zero-crossing distortion (ZCD) of the AC current caused by neglecting the AC filter inductor voltage. Another is that the system cannot deliver reactive power because the AC bypass branch switches at the power frequency. To address these problems, this work proposes an optimized hybrid modulation strategy. To reduce ZCD, the phase angle of the inverter output voltage reference is shifted, thereby compensating for the neglected leading angle. To generate the reactive power, the interval of the negative power output is calculated using the power factor. In addition, the freewheeling switch is kept on when power is flowing into the grid and commutates at a high frequency when power is fed back to the DC side. In this manner, the dead-time insertion in the high-frequency switching area is minimized. Finally, the performances of the proposed modulation strategy and traditional strategies are compared on a universal prototype inverter. Experimental results validate the theoretical analysis.

• 한국초전도ㆍ저온공학회논문지
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• 제6권2호
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• pp.29-34
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• 2004

The linear type flux pump aims to compensate a little bit decremental persistent current of the HTS magnet in NMR and MRI spectrometers. The flux pump mainly consists of DC bias coil, 3-phase AC coil and Nb foil. The persistent current in closed superconductive circuit can be easily adjusted by the 3-phase AC current, its frequency and the DC bias current. In the experiment, it has been investigated that the flux pump can effectively charge the current in the load coil of 543 mH for various frequencies in 18 minutes under the DC bias of 10 A and the AC of 5 $A_{rms}$. The maximum magnitudes of pumping current and load magnet voltage are 0.72 A/min and 20 ㎷, respectively. Based on simulation results by the FEM are proved to nearly agree with experimental ones.

• 한국초전도저온공학회:학술대회논문집
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• 한국초전도저온공학회 2002년도 학술대회 논문집
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• pp.241-244
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• 2002

We investigated over critical current characteristics of HTS tapes fabricated by KIMM. The critical current (Ic) of the HTS tapes was 68A/cm. In order to acquire over current I-V characteristics of HTS tapes, we applied AC that is 2-7 times of Ic to these tapes. When applied AC whose peak value is twice of Ic, we found out that total resistance of HTS tapes aid not change. In case of 3 times of Ic, resistances of HTS tapes began to increase slowly. However, superconducting regions of them were maintained stably in this condition. In addition, 280 $A_{peak}$was applied, superconducting regions began to be decreased gradually. Finally, 0.62m$\Omega$ of resistance was measured in HTS tapes which was applied AC correspond to 7 times of Ic at first cycle.

• 전력전자학회:학술대회논문집
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• 전력전자학회 2001년도 Proceedings ICPE 01 2001 International Conference on Power Electronics
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• pp.591-599
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• 2001

The paper identifies a severe form of core saturation instability in an DC/AC interaction system. It then seeks solutions to the problem by HVDC control means. This is achieved by a proper design of the Voltage Dependent Current Order Limiter (VDCOL), the Current Regulator and Timing Pulse generator. Supplementary control loops have also been introduced to result in a satisfactory performance as compared to that obtained one with the use of uncharacteristic harmonic filter on the AC side. Robustness of all the options has been demonstrated through recovery performance of the DC link in response to both I-phase and 3-phase 5 cycle faults on both rectifier and inverter commutating buses.

• 대한전기학회:학술대회논문집
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• 대한전기학회 1994년도 하계학술대회 논문집 A
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• pp.512-515
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• 1994

This paper propose the high power factor and efficiency buck-boost AC-DC converter because the input current is made sinusoidal wave in single phase alternating current source. The proposed converter is able to minimize switching loss by the partial resonant switching which is for switching devices to operate the zero voltage switching (ZVS) or zero current switching(ZCS) without increasing their voltage and current stresses.