• 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.

• 대한전기학회:학술대회논문집
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• 대한전기학회 2004년도 하계학술대회 논문집 B
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• pp.1205-1207
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• 2004

AC plasma power supply is used to control a ozone generator and a air pollution gas. AC plasma power supply is composed of power semiconductor switch devices and control board adapted SHE(Selected Harmonic Elimination) PWM method. AC plasma power supply with sinusoidal VVVF(variable voltage and variable frequency) is realized. Its output voltage range is from 0 [V] to 20[kV] and output frequency range is from 8[kHz] to 20[kHz]. Using proposed system, AC high voltage and high frequency discharge is tested in the DBD(dieletric barrier discharge) reactor, and the space distribution of a its non-thermal plasma is observed. In spite of the increasement of voltage and frequency, the proposed system have a stable operation characteristics. It is verified by the experimental results.

• 조명전기설비학회논문지
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• 제29권5호
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• pp.71-79
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• 2015

Recently, new Low Voltage DC (LVDC) power distribution systems have been constantly researched as uses of DC in end-user equipment are increased. As in conventional AC distribution system, High Impedance Fault (HIF) which may cause a failure of protective relay can occur in LVDC distribution system as well. It, however, is hard to be detected since change in magnitude of current due to the fault is too small to detect the fault by the protective relay using overcurrent element. In order to solve the problem, this paper presents an algorithm for detecting HIF using accumulated energy in LVDC distribution system. Wavelet Singular Value Decomposition (WSVD) is used to extract abnormal high frequency components from fault current and accumulated energy of high frequency components is considered as the element to detect the fault. LVDC distribution system including AC/DC and DC/DC converter is modeled to verify the proposed algorithm using ElectroMagnetic Transient Program (EMTP) software. Simulation results considering various conditions show that the proposed algorithm can be utilized to effectively detect HIF.

• 대한기계학회논문집B
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• 제25권3호
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• pp.442-450
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• 2001

Experiments were carried out on agglomeration of bipolarly charged particles in an alternating current electric field. Laboratory-scale setup was built and experiments were conducted at atmospheric condition. DOS(Di-octyl Sebacate) particles with 100% purity were generated by an atomizer. The particles were branched into two, each of which passed through a wire-to-plate type charging section where a positive or a negative DC high voltage was applied and was charged positively or negatively. These bipolarly charged particles together passed through an agglomeration section where an $\pm$20kV AC power was applied between two plates. The resident time in the agglomeration section was adjusted as l sec. Particle sampling was made by a cascade impactor (MOUDI). The effect of agglomeration system on the reduction ratio of particles below l ㎛ was 42∼45%. Effect of AC frequency on the particle size distribution was found insignificant.

• 조명전기설비학회논문지
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• 제23권5호
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• pp.72-79
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• 2009

태양 에너지는 재생 가능하고 오염이 없는 특성으로 바람직한 에너지 원이다. 계통에 이용하기 위해서는 dc-dc 컨버터와 계통 연계 do-ac 인버터가 필요하다. dc-dc 컨버터는 태양광 시스템이 높은 dc전압에 동작하기 위하여 필요하고, 인버터는 계통에 연결하기 위하여 필요한 전압과 주파수를 만들어 내는데 필요하다. 본 논문에서는 첫째로 단상 계통 연계 인버터에서 전류 루프 전달 함수가 유도되고, 둘째로 컨버터 측에서 컨덕턴스 증가 방식의 MPPT 방식이 제안하여 인버터 측에 최대 전력을 공급하는데 있다. 시뮬레이션 결과가 계통에서 태양광 인버터 시스템의 성능과 특성을 보여준다.

• 전기학회논문지P
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• 제66권4호
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• pp.188-193
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• 2017

In this paper, a ZVS-PWM high-frequency inverter with a PWM control function is applied to commercial system 220[Vrms], and a resonator type ZVS-PWM high-frequency inverter circuit with a fixed-two methods were proposed. The parameters of the transformer model equivalent circuit of a copier fixing device, which is an essential element in the parameter optimization of the proposed circuit, are obtained by using a high-frequency amplifier and its frequency characteristics are described. The proposed method compared to the existing single-ended ZVS-PFM high frequency inverter can suppress the voltage and current peak value of the power semiconductor switching device and reduce the switching loss. The efficiency of the proposed method itself is 98[%] at rated power output. Also, the efficiency of 96[%] can be obtained even at low output, so that the proposed high frequency inverter is very efficient inverter. The total efficiency from the commercial AC input to the inverter output is 93[%] at rated, which is considered efficient for use in copying machines. In addition, the diode bridge loss accounts for the largest portion of the overall system efficiency distribution. On the other hand, the nonparallel filter has a very low loss.

• 전력전자학회논문지
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• 제2권1호
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• pp.12-25
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• 1997

본 논문은 PNGV 계획에 따른 차세대 전기자동차의 개발을 위하여 고주파 교류 전력분배 시스템을 적용하여 이용할 수 있는 추진력 장치의 구현 가능성에 대한 조사 연구이다. 실행 가능한 관점에서 전력 분배와 에너지원의 결합이 쉽게 이루어 질 수 있고 변환이 가능한 여러 가지 형태의 시스템이 비교 검토되었으며, 현재 기술 수준으로 보아 가까운 장래에 실현 가능한 최적의 시스템 구성은 배터리와 내연기관엔진 및 유도전동기를 이용하는 하이브리드형이 제시되었다. 각 시스템의 원활한 전력수급과 운전특성을 위하여 단상 고주파 교류 전력분배 제어기법을 적용하였으며, 이 시스템의 타당성을 입증하기 위하여 시스템 구성에 따른 모델링과 컴퓨터 시뮬레이션을 실시하였다. 이 결과 차세대 전기자동차용으로 제시된 고주파 교류 전력분배에 의한 하이브리드형 추진력 시스템이 가능하며 운전특성도 우수함을 보여주었다.

• 조명전기설비학회논문지
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• 제14권6호
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• pp.35-42
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• 2000

본 연구에서는 몰드형 전력변압기의 절연열화 상태를 진단하기 위해 에폭시 수지의 보이드방전에 의한 절연열 화의 상태를 트리의 길이에 따라 열화 초기, 중기 및 말기로 구분하고 이때 방출된 음향선호흘 분석하였다. 또한 보이드방전에 의한 음향선호를 측정할 때 몰드변압기의 철심에서 발생되는 자기적 음향 노이즈가 중첩됨으로 이를 구분하기 위해 용량 500[kVA]인 실용 몰드변압기를 배전 계통 22.9[kV]의 선로에 접촉하였을 때, 자화전류 및 부하전류에 의해 각 상에서 발생되는 음향 노이즈 신호의 주파수 스펙트럼올 분석하였다. 실행 결과, 에폭시수지의 보이드방전애 의해 발생된 음향방출신호의 주파수 스펙트럼은 열화상태에 따라 약 50-230[kHz] 범위에서 측정되었으나, 배잔계동에 접속된 실용 몰드변압기의 자화전류 및 부하전류에 의해 발생된 자기회로의 음향 노이즈에 대한 주파수 스펙드럼은 약 4O-120[kHz] 대역인 것으로 나타났다.