• 대한전자공학회논문지SD
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• 제37권1호
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• pp.19-28
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• 2000

고장에 대한 강인성, 높은 출력 전류 특성 및 모듈화의 용이성 때문에 병렬 인버터 시스템은 그활용도가 점차 높아지고 있다. 이러한 병렬 인버터 시스템에서 전체 시스템 전력균형 제어는 주로 주파수 드롭과 전압 드룹 제어 또는 유효전력 과 무효전력 제어를 통하여 이루어지고 있다. 그러나 이러한 제어방법들은 시스템 변수 변동 및 부하변동에 따라 늦은제어 응답특성을 가지는 단점을 가지고 있다. 이러한 단점을 해결하기위해, 본논문에서는 병렬 인버터 시스템의 각모듈 출력전력을 균등화 시키는 새로운 제어기를 제안하였다. 제안한 제어기는 하드웨어 구현의 용이성, 피크전류 차단 기능들의 특성을 가진다. 또한 본논문에서는 제안한 제어기의 설계 절차를 기술하였으며, 여러 부하조건 및 시스템 파라미터 변동조건에 따라 순시전력균형제어기 동작 특성의 효용성을 컴퓨터 시뮬레이션 및 실험을 통하여 확인 하였다.

• 한국철도학회논문집
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• 제11권3호
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• pp.248-256
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• 2008

본 논문은 고속철도 주변 통신회선에 발생되는 잡음전압의 실체 파악을 통해 전력유도잡음전압이 발생하지 않는 것을 증명하였으며, 국내통신회사 및 전파연구소에서 사용하고 있는 평형도 측정에서의 문제점과 계측 오류를 규명하며 표준 측정회로와 측정 조건을 ITU-T 국제 기준에 맞도록 개정할 것을 제안한다.

• Journal of Power Electronics
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• 제14권6호
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• pp.1147-1156
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• 2014

This study proposes a quasi-fixed-frequency hysteresis current tracking control strategy for modular multilevel converters (MMCs) on the basis of voltage partition principle. First, by monitoring the grid voltage and the deviation between the output and reference currents, the output voltage is determined, thus prompting the output current to quickly and efficiently track the given current. Second, the voltages of the upper/lower capacitor of the arm and the voltages between the upper and lower arms are balanced by combining these arms with virtual loop mapping and arm voltage balance control, respectively. In particular, the proposed method is designed for any level and number of sub-modules. The validity of the proposed method is verified by simulations and experimental results of a five-level MMC prototype.

• 전력전자학회:학술대회논문집
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• 전력전자학회 2000년도 전력전자학술대회 논문집
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• pp.30-33
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• 2000

Using power semiconductor switches such as IGBTs diodes and L-C circuits novel repetitive impulse voltage generator is developed. In the presented circuits high voltage pulse is generated by series-connection of capacitors and IGBTs. The charging of capacitors and voltage balance of IGBTs is done automatically. To verify the proposed circuit 20kV, 300A pulse generator is manufactured and tested.

• 전기학회논문지P
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• 제59권3호
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• pp.325-329
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• 2010

Capacitor has been used principally for the power factor compensation long ago. However now it does as passive filter to reduce harmonics of nonlinear load with reactor. Most of the customer's low-voltage feeder has been designed with approximately balanced and connected at the 3 phase four wire system. But voltage and current unbalance is appeared by the mixing operation of single or three phase load etc. The addition of reactor at the condenser may rise its terminal voltage. Voltage and current values above rating can act on electrical stress on the condenser. In this paper, we calculated and measured that voltage, current and capacity of condenser are changed under the voltage balance. We conclude that magnitude and deviation of phase voltage act on major point of electrical stress.

• 대한전기학회논문지:전기기기및에너지변환시스템부문B
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• 제52권4호
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• pp.170-176
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• 2003

This paper introduces an improved pulse generator using power semiconductors and L-C circuit. The proposed circuit consists of the series connected boost converter structure. In the presented circuits, high voltage pulse is generated by series-connection of capacitors and IGBTs. The charging of capacitors and voltage balance of IGBTs are obtained automatically. To verify the proposed circuit, 1.8㎸, 40A pulse generator is manufactured and tested.

• 전력전자학회:학술대회논문집
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• 전력전자학회 2008년도 하계학술대회 논문집
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• pp.277-279
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• 2008

In this paper, a novel active boost converter for SR drive is proposed. An active capacitor circuit is added in the front-end. Based on this active capacitor network, when boost switch turns off, this network seems as passive capacitor network. And the voltage of boost capacitor can keep balance with dc-link voltage automatically. In the capacitor network, discharging voltage is general dc-link voltage in parallel-connected capacitors; charging voltage is double dc-link voltage in series-connected capacitors. When boost switch turns on, two capacitors are connected in series, and discharging voltage is up to double dc-link voltage. So the fast excitation current can be obtained from this mode. Profit from fast excitation and fast demagnetization mode, the performance and output power can be improved. Some computer simulations are done to verify the performance of proposed converter.

• Journal of Electrical Engineering and Technology
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• 제9권5호
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• pp.1632-1642
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• 2014

This paper presents an interleaved resonant converter to reduce the voltage stress of power MOSFETs and achieve high circuit efficiency. Two half-bridge converters are connected in series at high voltage side to limit MOSFETs at $V_{in}/2$ voltage stress. Flying capacitor is used between two series half-bridge converters to balance two input capacitor voltages in each switching cycle. Variable switching frequency scheme is used to control the output voltage. The resonant circuit is operated at the inductive load. Thus, the input current of the resonant circuit is lagging to the fundamental input voltage. Power MOSFETs can be turn on under zero voltage switching. Two resonant circuits are connected in parallel to reduce the current stress of transformer windings and rectifier diodes at low voltage side. Interleaved pulse-width modulation is adopted to decrease the output ripple current. Finally, experiments are presented to demonstrate the performance of the proposed converter.

• Progress in Superconductivity
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• 제12권1호
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• pp.62-67
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• 2010

We investigated the voltage applicable to $Au/YBa_2Cu3O_7$ (YBCO) meander lines. The meander line was fabricated by patterning Au/YBCO thin films grown on sapphire substrates by photolithography. It was subjected to simulated AC fault currents, and the resistance was measured and analyzed. The samples were immersed in liquid nitrogen during the experiment for effective cooling. The voltage applicable to the meander lines depended on the fault duration. Dependence was strong at short fault durations, and weak at long durations. When the voltage was plotted as a function of the fault duration on a log-log scale, data fell more or less on straight lines for all meander lines. In other words, the voltage applicable to Au/YBCO meander lines on sapphire substrates was inversely proportional to $t^b$, where t is the fault duration and b ranges from 0.4 to 0.5. The results were analyzed quantitatively with the concept of heat balance. Under adiabatic condition, the voltage is to be inversely proportional to $t^{0.5}$ for all samples. Less value of b for some samples is thought to be due to cooling of the samples by liquid nitrogen.

• 대한전기학회논문지:전기기기및에너지변환시스템부문B
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• 제50권8호
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• pp.408-415
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• 2001

Using power semiconductor switches such as IGBTs, diodes and L-C circuits, novel repetitive impulse voltage generator is developed. In the presented circuits, high voltage pulse is generated by series-connection of capacitors and IGBTs. Therefore, the high voltage pulse is obtained by circuit configuration without any high voltage pulse transformer and high voltage dc source. Especially, the proposed circuit can operate up to several kHz and have high reliability and longer life than conventional ones. In also gives voltage balance of IBGTs automatically. So, the difference of characteristics of IGBTs and drive signal does not cause severe problems. To verify the proposed circuit, 20kV and 300A pulse generator is manufactured and tested.