• The Transactions of the Korean Institute of Electrical Engineers
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• v.36 no.3
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• pp.171-178
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• 1987

A study of two phase chopper system with four separate groups of DC motors in powering. A novel two phase chopper system with four separate groups of DC motors which applies the principles of two phase chopper with two separate groups of DC motors is dealt with this article. The main circuit consists of eight sets of chopping parts, four diodes and four separate groups of DC motors. Four groups of DC motors are driven through the series and parallel connections to each other in accordance with the operating conditions of the choppers. Although the proposed chopper circuit requires more circuit elements than the conventional two phase chopper system with combined output or two phase chopper system with two separate groups of DC motors, it has the following advantages` (1). It is possible to drive twice as much motors as conventional system does, using esisting receiving-and equipments and motors. (2). It is possible to control load voltage continuously from 0 to source voltage by changing time-ratio from 0 to 1. (3). Load current division becomes equalized. Therefore it is possible to drive not only series motors but also shunt and separately exited motors. (4). When smoothing reactor L is small, harmonic components of the proposed circuit is not so large. Therefore, the value of L can be determined from viewpoints of allowable value of ripple-ratio and current unbalance factor.

• The Transactions of the Korean Institute of Electrical Engineers
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• v.40 no.2
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• pp.162-172
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• 1991

In proportion to the capacity enlargement of the induction motor system controlled by current source inverter, the capacitance of the commutating capacitor is enlarged and then the spike value of output voltage is increased at the moment of charge and discharge. Moreover, the output currnet includes a number of harmonic components. Such voltage spike and harmonics generate the torque ripple and lead to bad effects on the performance of the induction motor. In this study, all the harmonics excluding 17th and 19th harmonics were mostly elimunated by adopting 18-phase Triple High Frequency Current Source Inverter(HFCSI), and the spike component of output voltage was reduced by adding the Voltage Clamping Circuit(VCC). As a result, the torque ripple and the commutation loss were reduced and the performance of the system was improved. Experiments for speed control were carried out in the tripple current source inverter system for induction motor drive. Overall system was controlled by ONE CHIP MICROCOMPUTER(INTEL 8751). Control circuits were simplified and good experimental results in the constant V/F control were obtained due to the flexibility of the microcomputer.

• Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
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• v.20 no.1
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• pp.48-56
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• 2006

This paper studies particularly applicable method for sensorless PM BLDC motor drive system. The waveform of the motor internal voltages(or back emf) contains a fundamental and higher order frequency harmonics. Therefore the third harmonic component is extracted from the stator phase voltage. The resulting third harmonic signal keeps a constant phase relationship with the rotor flux for any motor speed and load condition. Also because of low resolution of estimated signal obtained by the proposed sensorless algorithm, to improve the wide range of speed response characteristic more exactly, we propose the rotor position signal synthesizer using PLL circuit based on estimated signals. Some experimental results are provided to demonstrate the validity of the proposed control method.

• Korean Journal of Optics and Photonics
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• v.10 no.2
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• pp.146-151
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• 1999

We demonstrated a harmonic mode locking scheme that used regeneratie phase modulation to get a high and stable repetition rate in a figure-of-eight fiber soliton laser. From the detected beat spectra of the laser output, a sinusoidal clock freguency tone of 400 MHz, the 96th harmonics of the fundamental mode locking frequency, was extracted with a high Q filter and was used to drive the phase modulator, resulting in stable output of soliton pulse train synchronized with the modulation signal. Generated soliton pulses had FWHM pulsewidth of 930 fs and 3.1 nm linewidth, yielding pulsewidth-bandwidth product of 0.359 that was close to the transform limit. As the modulation frequency always followed the beat frequency of laser modes, stable harmonic mode locking was achieved without the adjustment of the cavity length, which has been commonly required in actively mode-locked lasers.

• Journal of Power Electronics
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• v.18 no.6
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• pp.1729-1750
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• 2018

Voltage source inverters (VSIs) are widely used to drive induction motors in industry applications. The quality of output waveforms depends on the switching sequences used in pulse width modulation (PWM). In this work, all existing optimal space vector pulse width modulation (SVPWM) switching strategies are studied. The performance of existing SVPWM switching strategies is optimized to realize a tradeoff between quality of output waveforms and switching losses. This study generalizes the existing optimal switching sequences for total harmonic distortions (THDs) and switching losses for different modulation indexes and reference angles with a parameter called quality factor. This factor provides a common platform in which the THDs and switching losses of different SVPWM techniques can be compared. The optimal spatial distribution of each sequence is derived on the basis of the quality factor to minimize harmonic current distortions and switching losses in a sector; the result is the minimum ripple loss SVPWM (MRSLPWM). By employing the sequences from optimized switching maps, the proposed method can simultaneously reduce THDs and switching losses. Two hybrid SVPWM techniques are proposed to reduce line current distortions and switching losses in motor drives. The proposed hybrid SVPWM strategies are MRSLPWM 30 and MRSLPWM 90. With a low-cost PIC microcontroller (PIC18F452), the proposed hybrid SVPWM techniques and the quality of output waveforms are experimentally validated on a 2 kVA VSI based on a three-phase two-level insulated gate bipolar transistor.

• Proceedings of the KIEE Conference
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• 2008.04a
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• pp.221-222
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• 2008

This paper is proposed a high performance speed control of the synchronous reluctance motor through the artificial intelligent SV-PWM. SV-PWM is controlled using fuzzy control that is artificial intelligent control. SV-PWM can be maximum used maximum dc link voltage and is excellent control method due to characteristic to reducing harmonic more than others. Fuzzy control has a advantage which can be robustly controlled. Simulation results are presented to show the validity of the proposed algorithm.

• Journal of Electrical Engineering and Technology
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• v.7 no.4
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• pp.546-557
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• 2012

In Conventional Combined Vector and Direct Controls (VC-DTC) of induction motor, stator current is very rich in harmonic components. It leads to high torque ripple of induction motor in high and low speed region. To solve this problem, a control method based on the concept of fuzzy logic approach is used. The control scheme proposed uses stator current error as variable. Through the fuzzy logic controller rules, the choice of voltage space vector is optimized and then torque and speed are controlled successfully with a less ripple level in torque response, which improve the system's performance. Simulation results trough MATLAB/SIMULINK${(R)}$ software gave results that justify the claims.

• The Transactions of the Korean Institute of Power Electronics
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• v.4 no.5
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• pp.413-422
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• 1999

Auto-connected multipulse(12/24pulse) rectifier schemes are cost effective methods for reducing line current hamonics in PWM drive systems. Employing these schemes to enhance utility power quality requires careful attention to several design considerations In particular, excursion of dc-link voltage at no load, effect of pre-existing voltage distortion, impedance mismatches, unequal diode drops on rectifier current sharing and performance, are fully analyzed, Several corrective measures to improve the performance of 12/24­pulse rectifier systems are also discussed. Finally, experimental results on a 460V, 60Hz 400kVA commercial ASD, retrofitted with 12/24pulse rectifier systems are discussed in detail.

• Proceedings of the KIEE Conference
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• 1996.07a
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• pp.616-618
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• 1996

This paper presents an unipolar PWM which commutated switching device only in a half period. This method reduced switching loss significantly because of decreasing switching number in n period. In high speed motor drive needed high frequency above 300 Hz fundamental frequency, this method is suited very well. This paper described the principle of unipolar PWM method, analyzed harmonic spectrum and compared with bipolar PWM, Modified PWM and Overmodulation method in switching loss.

• Proceedings of the KIEE Conference
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• 1996.07a
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• pp.361-363
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• 1996

The output of solar cell should be operated in the maximum power point, since it is greatly fluctuated by insolation and temperature. Also, since the output of solar cell is a DC power, it needs the inverter to interact with utility line. In this paper, we made composed of PV system with a chopper that control the maximum power point and the inverter that drive to the high power factor and low harmonic by use of defected and compensated utility line voltage for synchronous phase with utility line.