• Proceedings of the KIPE Conference
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• 2014.11a
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• pp.87-88
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• 2014

The paper presents a novel phase locked loop(PLL) control method for robust three-phase thyristor dual converters under sag, notch, and phase loss conditions. This method is applied to three line to line voltages of grid to derive three phase angle errors from three separated single-phase PLLs. They can substitute for abnormal phase to guarantee the synchronization in the various grid fault conditions. The performance of novel PLL with moving average method is verified through simulations.

• The Transactions of the Korean Institute of Electrical Engineers
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• v.45 no.4
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• pp.526-529
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• 1996

A novel control scheme for a Switched Reluctance Motor(SRM) drive is described. To increase torque, and to commutate easily, flat-topped phase current and fixed switching angle control is proposed. The conditions for flat-topped phase current are analyzed. It is achieved by voltage control with fixed switching angle. The proposed control system was tested to verify this suggestion. (author). refs., figs., tab.

• Journal of Power Electronics
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• v.8 no.4
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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.

• The Transactions of The Korean Institute of Electrical Engineers
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• v.56 no.12
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• pp.2127-2134
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• 2007

The simulation model has been already developed not for 7 phase but for 3 phase BLDC motor. It is necessary to develop a new simulation model of multi-phase BLDC motor including the phase delay angle especially in the high speed region. In this paper, the suitability of the proposed model is verified through the several computer simulations, and experimented results.

• Journal of Information Display
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• v.10 no.1
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• pp.19-23
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• 2009

In this paper, we review the proposed liquid crystal display (LCD) with a tunable viewing angle consisting of a conventional liquid crystal display (LCD) panel and a thermally variable retardation layer (TVRL) characterized by uniformly aligned LC film with transparent indium-tin-oxide electrodes for Joule heating. In the TVRL, nematic phase is transitioned into isotropic by Joule heating. The numerical calculation showed that the intrinsic wide viewing angle was achieved at the isotropic phase of the TVRL by Joule heating, whereas the narrow viewing angle was obtained at the nematic phase of the TVRL. The simulated and experimental results of the proposed LCD show continuous and symmetrical viewing angle characteristics by tuning the retardation of TVRL using Joule heating. The structure of the viewing angle control proposed here is adoptable to all LCD modes with wide viewing angle characteristics.

• The Transactions of the Korean Institute of Power Electronics
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• v.25 no.5
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• pp.404-411
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• 2020

Inductive power transfer (IPT) systems for electric vehicles generally require zero phase angle (ZPA) frequency tracking control to achieve high efficiency. Current sensors are used for ZPA frequency tracking control. However, the use of current sensors causes several problems, such as switching noise, degrading control performance, and control complexity. To solve these problems, this study proposes ZPA frequency tracking control without current sensors. Such control enables ZPA frequency tracking without real-time control and achieves stable zero voltage switching operation closed to ZPA frequency within all coupling coefficient and load ranges. The validity of the proposed control algorithm is verified on LCCL-S topology with a 3.3 kW rating IPT experimental test bed. Simulation verification is also performed.

• The Transactions of the Korean Institute of Electrical Engineers B
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• v.53 no.3
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• pp.206-211
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• 2004

In phase controlled rectifier, it's been known that a fast response is achieved by predictive current control without any overshoot. The frequent sampling period is essential to improve the firing accuracy in conventional predict current control. However, improving the firing accuracy if difficult to reduce the period of sampling efficiently because current sampling and predictive current control is carried out in every period and the ON-OFF current control is performed by comparing two different one. To improve the firing accuracy at the predictive current control, the calculated firing angle is loaded into the high-accuracy hardware timer. So the calculation of exact crossing point between the predictive and actual current is the most important. In this paper, the flow chart for proposed firing angle calculation algorithm is obtained for the fastest current control performance in transient state. The performance of proposed algorithm is verified through simulations and experiments.

• Proceedings of the KIEE Conference
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• 1995.07a
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• pp.350-352
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• 1995

The starting characteristics of single phase induction motor(SPIM) is described by control of phase and voltage. Auxiliary winding voltage is controlled by DC amplifier and phase is integrator. These processes enable comparison of torque with slip in each voltage and phase angle variations. Simulation and experimentation results of the motor's torque-slip characteristics using the controlled auxiliary winding voltage and phase angle arc shown and discussed. As a results, starting time is fast and main winding current is small when auxiliary winding voltage is low than rating voltage and starting characteristics is good in phase angle $90^{\circ}$.

• Journal of Electrical Engineering and Technology
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• v.5 no.4
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• pp.623-630
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• 2010

This paper presents the implementation and characteristic analysis of a drive system for a three-phase permanent magnet motor with independent excitation winding that is applicable for electric bicycles. The design features improves the phase current waveform, output power, and torque by using advance angle control. This adjusts the phase angle of each phase current in relation to back EMF. In addition, a DC-side PI current control is performed through PWM generation circuit using a low-cost one-chip microcontroller and a CPLD chip, resulting in reduced system costs. Finally, the validity of this control scheme for driving electric bicycles and output/torque improvement characteristics are verified through analysis and experimental results.

• Proceedings of the IEEK Conference
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• 1998.06a
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• pp.955-957
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• 1998

Switched reluctance motor(SRM) has the advantages of simple structure, low rotor inertia, and high poer rate per unit volume. However, position sensor isessential in SRM in order to synchronize the phase excitation to the rotor position. The position sensors increase the cost of drive system, and tend to reduce system reliability. This paper investigtes the speed control of sensorless SRM. The proposed system consists of position detection circuit, dwell angle controller, digital logic commutator, PI speed controller and 4-phase inverter. The performances in the proposed system are verified through the experiment.