• 전기학회논문지P
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• 제64권4호
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• pp.308-314
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• 2015

This paper has proposed a new boost rectifier. Adequate input current was obtained by keeping the duty ratio constant without complicated conventional control methods and the improvement of the waveform was increased. With a decrease of distortion up to 12.9[%], the scope of restriction on harmonics was set to 13.0[%]($3^{td}$ harmonics), 1.1[%]($5^{td}$ harmonics) and 0.6[%]($7^{td}$ harmonics), respectively. Because complicated methods of control are avoided, the circuit configuration is simple and practical. In particular, the said effect turned out to be highly efficient in the low boosting ratio range(boosting ratio$({\alpha})=1.25$). The feasibility of these facts has been proven both theoretically and experimentally.

• Journal of Power Electronics
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• 제11권3호
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• pp.311-318
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• 2011

LCL filters installed at converter outputs offer a higher harmonic attenuation than L filters. However, as a three order resonant circuit, it is difficult to stabilize and has a risk of oscillating with the power grid. Therefore, careful design is required to damp LCL resonance. Compared to a passive damping method, an active damping method is a more attractive solution for this problem, since it avoids extra power losses. In this paper, the damping capabilities of capacitor current, capacitor voltage, and grid-side current feedback methods, are analyzed under the discrete-time state-space model. Theoretical analysis shows that the grid-side current feedback method is more suitable for use in active power filters, because it can damp LCL resonance more effectively than the other two methods when the ratio of the resonance and the control frequency is between 0.225 and 0.325. Furthermore, since there is no need for extra sensors for additional states measurements, this method provides a cost-efficient solution. To support the theoretical analysis, the proposed method is tested on a 7-kVA single-phase shunt active power filter.

• 제어로봇시스템학회논문지
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• 제13권2호
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• pp.154-162
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• 2007

In this paper, we propose a new AC-DC converter control method to comply with harmonics regulation(IEC 61000-3) effective for the inverter system of an air conditioner whose power consumption is less than 2,500W. There are many different ways of AC-DC converter control, but this paper focuses on the converter control method that is adopting an input reactor with low cost silicon steel core to strengthen cost competitiveness of the manufacturer. The proposed control method controls input current every half cycle of the line frequency to get unit power factor and at the same time to reduce switching loss of devices and acoustic noise from reactor. This kind of converter is known as a Partial Switching Converter(PSC). In this study, theoretical analysis of the PSC has been performed using Matlab/Simulink while a 16-bit micro-processor based converter has been used to perform the experimental analysis. In the theoretical analysis, electrical circuit models and equations of the PSC are derived and simulated. In the experiments, micro-processor controls input current to keep the power factor above 0.95 by reducing the phase difference between input voltage and current and at the same time to maintain a reference DC-link voltage against voltage drop which depends on DC-link load. Therefore it becomes possible to comply with harmonic regulations while the power factor is maximized by optimizing the time of current flow through the input reactor for every half cycle of line frequency.

• Journal of Electrical Engineering and Technology
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• 제12권3호
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• pp.1090-1100
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• 2017

This paper presents the comparison of starting current characteristics of a three-phase induction motor fed by two types of soft starters. The first soft starter under investigation is a conventional AC voltage controller on the basis of a phase-control technique. The other is the proposed asynchronous PWM AC chopper which is developed from the conventional synchronous PWM AC chopper. In this paper, the proposed asynchronous PWM AC chopper control scheme is developed by generating only two asynchronous PWM signals for a three-phase main power circuit (6 switching devices) from a single voltage control signal which is compared with a single sawtooth carrier signal. By this approach, the PWM signals are independent and easy to implement since the PWM signals do not need to be synchronized with a three-phase voltage source. Details of both soft starters are discussed. The experimental and simulation results of the starting currents are shown. It is found that the asynchronous PWM AC chopper efficiently works as a suitable soft starter for the three-phase induction motor due to that the starting currents are reduced and are sinusoidal with less harmonic contents, when being compared with the starting current waveforms using the conventional phase-control starting technique. Also the proposed soft starter offers low starting electromagnetic torque pulsation.

• 전력전자학회논문지
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• 제19권1호
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• pp.64-70
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• 2014

In this paper, the new LLCL filter is proposed for grid connected three-phase PWM inverter for passive damping. LLCL filter inserts a small inductor in the branch of the capacitor of the traditional LCL filter to compose a series resonant circuit to reduce the switching-frequency component on grid current. Using LLCL filter, the switching-frequency current ripple components can be attenuated much better than the LCL filter, leading to a decrease in the total inductance. However, the resonance phenomena caused by zero impedance from the addition of LC branch in LLCL filter can be a big problem. Resonance phenomena of LLCL filter can be a source of grid system instability, so proper damping methods are required. However, it is difficult to apply a passive damping method in the conventional LLCL filter, because the damping resistor increase impedance of the LC branch. Therefore, switching frequency component of grid current can not much attenuated by low Q of LC series resonance effect. In this paper, a new LLCL filter is proposed to overcome the conventional LLCL filter with passive damping. The validity of the proposed method is proven by simulation and experimental result.

• KEPCO Journal on Electric Power and Energy
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• 제2권4호
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• pp.577-582
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• 2016

최근 급속한 녹색환경 정책으로 LED를 이용한 조명 광원들이 설치 운용하고 있으나, 이들 광원의 전원 공급은 안정된 직류 전원 공급을 위해서 스위칭 모드 전원 공급(SMPS) 장치로 전원을 공급하고 있다. 그러나, 이들 전원 공급 장치는 공급 단가 때문에 설계 및 설치과정에서 스위칭에 따른 전력과 변환역률, 전기적 노이즈 및 돌입전류들은 간과하고 있다. 따라서, 본 연구에서는 SMPS는 고품질의 전원을 LED 조명 부하에 공급하기 위하여 스위칭 시에 다음과 같은 3가지 관점에서 회로를 연구하였다. 첫 번째, 역률과 효율을 약 85% 확보하고, 두 번째, 노이즈(고조파 포함) 최소화, 세 번째는 스위치-온 시 3A 돌입전류를 $100{\mu}sec$ 후 최소 0.3 A로 감소하여 돌입 전류 침입을 최소화 하고자 하였다. 본 연구에서는 IC형 구동기(LNK 409)를 적용하여 입력전압과 출력상황을 귀환 형태로 감시하도록 하였으며, 정전류 출력을 위하여 정전압을 유지할 수 있는 제어회로와 시상수를 개발하였다. 그러나, 부하 변동 시 미세한 전류의 불규칙으로 인한 발열 문제는 해결하지 못하고 있다. 이를 증명하고자 LED 조명 부하 46 W급을 대상으로 효과를 검증하였다.

• 한국음향학회지
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• 제16권4호
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• pp.76-84
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• 1997

본 논문은 이동통신기기의 핵심부품중 하나인 VCO를 IC로 설계한 내용을 기술하였다. 설계한 VCO는 배리캡을 사용한 LC 동조형발진기로 구현하였다. 사용한 발진소자중 인덕터는 실리콘 IC 구현상의 난점[8]으로 인해 외부로 구성하고 나머지부분을 모두 IC화 하였다. 제작하는데 사용된 마스크 수는 15개이며 칩 사이즈는 1150um${\times}$780um이다. 제작한 VCO IC를 테스트한 결과 전원전압 5V에서 제어전압을 1V에서 3V로 변화시킬때 880MHz 영역에서 동작하였으며 주파수 천이는 425KHz/V, 주파수 편이는 1.97MHz/T, 캐리어 레벨은 -7dBm, 전류소모는 16.7mA이었다. 또한, 위상 잡음은 50KHz 오프셋에서 -80dBc/Hz 이며 중심주파수에 대한 하모닉응답은 -41dBm 이다. 향후 송수신단을 단일 칩화하기 위해서는 외부회로도 실리콘 기판위에 구현할 수 있는 실리콘 MMIC[1][8]에 대한 연구가 수행되어야 할 것이다.

• 전력전자학회논문지
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• 제9권3호
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• pp.285-293
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• 2004

본 논문에서는 능동역률보상(PFC)의 구조를 가진 SEPIC 컨버터를 이용한 무전극 형광램프(electrodeless fluorescent lamps)용 전자식 안정기를 제안하였다. SEPIC 컨버터는 입력 전류의 낮은 고조파와 고역률의 특성을 가진다. 제안된 제어방법으로는 UC3854의 적분회로를 이용한 것으로 이 기술은 전류연속모드로 동작하는 역률보상 및 과전류보호를 제공하는 매우 간단한 제어 회로이다. 제안된 무전극 형광램프용 전자식 안정기는 3개의 무전극 형광램프용으로 설계되어 기존의 무전극 형광램프용 전자식 안정기보다 에너지 및 제작비 절약 효과가 크다. 제안된 안정기의 특성을 측정하기 위해 실험을 실시하였으며 이를 통해 고역률과 낮은 THD를 확인하였다.

• 대한전기학회:학술대회논문집
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• 대한전기학회 2004년도 추계학술대회 논문집 전기기기 및 에너지변환시스템부문
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• pp.160-163
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• 2004

A passive lossless turn-on/turn-off snubber network is proposed for the boost PWM converter. Previous AC/DC PFC Boost Converter perceives feed forward signal of output for average current-mode control. Previous Boost Convertor, the Quantity of input current will be decreased by the decrease of output current in light load, and also Power factor comes to be decreased. Also the efficiency of converter will be decreased by the decrease of power factor. The proposed converter presents the good PFC, low line current harmonic distortions and tight output voltage regulations using energy recovery circuit. All of the semiconductor devices in the converter are turned on under exact or near zero voltage switching(ZVS). No additional voltage and current stresses on the main switch and main diode occur. To show the superiority of this converter is verified through the experiment with a 640W, 100kHz prototype converter.

• Journal of Electrical Engineering and Technology
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• 제12권3호
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• pp.1137-1145
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• 2017

This paper proposes the dead time effect compensation algorithm using proportional resonant controller in pulse width modulation inverter of motor drive. To avoid a short circuit in the dc link, the dead time of the switch device is surely required. However, the dead time effect causes the phase current distortions, torque pulsations, and degradations of control performance. To solve these problems, the output current including ripple components on the synchronous reference frame and stationary reference frame are analyzed in detail. As a results, the distorted synchronous d-and q-axis currents contain the 6th, 12th, and the higher harmonic components due to the influence of dead time effect. In this paper, a new dead time effect compensation algorithm using proportional resonant controller is also proposed to reduce the output current harmonics due to the dead time and nonlinear characteristics of the switching devices. The proposed compensation algorithm does not require any additional hardware and the offline experimental measurements. The experimental results are presented to demonstrate the effectiveness of the proposed dead time effect compensation algorithm.