• Journal of Electrical Engineering and Technology
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• v.10 no.1
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• pp.8-17
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• 2015

This paper analyses the power flow of a three-feeder/multi-bus distribution system by a custom Generalized Power Quality Conditioner (GUPQC). The GUPQC has been realized by three voltage source converters (VSCs) coupled back-to-back through a common DC-link capacitor on the DC-side. One feeder was controlled by the shunt compensator, whereas each of the other two feeders was controlled by the proposed novel series compensator. The GUPQC has the capability to simultaneously compensate voltage and current quality problems of a multi-bus/three-feeder distribution system. Besides that, the power can be transferred from one feeder to other feeders to compensate for poor power quality problems. Extensive simulation studies were carried out by using MATLAB/SIMULINK software to establish the ability of the GUPQC to improve power quality of the distribution systems under distorted supply voltage conditions.

• Proceedings of the KIEE Conference
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• 2003.10b
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• pp.187-189
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• 2003

Conventional Switched Mode Power Supplies(SMPS) with diode-capacitor rectifier have distorted input current waveform with high harmonic content. Typically, these SMPS have a power factor lower than 0,65. To improve with this problem the power factor correction(PFC) circuit of power supplies has to be introduced. Specially. to the reduce size and manufacture cost of power conversion device, the single-stage PFC converter is increased to demand as necessary of study. in this paper, The comparative analysis of power factor correction circuit using Feedforward control with average current mode flyback converter(single-stage) and boost converter(two-stage). Also, the validity of designed and manufactured high power factor flyback converter and boost converter is confirmed by simulation and experimental results.

• Proceedings of the KIEE Conference
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• 2003.07b
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• pp.1244-1246
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• 2003

Conventional Switched Mode Power Supplies(SMPS) with diode-capacitor rectifier have distorted input current waveform with high harmonic content. Typically, these SMPS have a power factor lower than 0.65. To improve with this problem. the power factor correction(PFC) circuit of power supplies has to be introduced. Specially, to reduce size and manufacture cost of power conversion device, the single-stage PFC converter is increased to demand as necessary of study. In this case single-stage PFC converter has been used DC-DC converter with boost converter. However in this paper, it is studied flyback converter of high power factor, high efficiency by feedforward control. Also, the validity of designed and manufactured high power factor flyback converter is confirmed by simulation and experimental results.

• Proceedings of the KIPE Conference
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• 2002.11a
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• pp.7-11
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• 2002

This paper proposes an APF(Active Power Filter) with WRIM(Wounded Rotor Induction Motor) controlled by sliding mode which can compensate harmonic currents generated in a power system. As non-linear loads increase gradually in industry fields, harmonic current generated In the electric power network system also increases. Harmonic current makes a power network current distorted and generates heat, vibration and noise In the power machinery, Many approaches have been applied to compensate harmonic currents generated in the power system. Among various control strategy, in this paper, a sliding mode controlled systems is designed and evaluated. This is a flywheel compensator based on secondary excitation of WRIM(wounded rotor induction motor) with SMC(sliding mode controller). The proposed system uses a flywheel as an energy storage device. The designed control scheme is verified through simulation.

• Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
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• v.28 no.11
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• pp.68-76
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• 2014

This paper presents an offset error compensation algorithm for the accurate phase angle of the grid voltage in single-phase grid-connected inverters. The offset error generated from the grid voltage measurement process cause the fundamental harmonic component with grid frequency in the synchronous reference frame phase lock loop (PLL). As a result, the grid angle is distorted and the power quality in power systems is degraded. In addition, the dq-axis currents in the synchronous reference frame and phase current have the dc component, first and second order ripples compared with the grid frequency under the distorted grid angle. In this paper, the effects of the offset and scaling errors are analyzed based on the synchronous reference frame PLL. Particularly, the offset error can be estimated from the integrator output of the synchronous reference frame PLL and compensated by using proportional-integral controller. Moreover, the RMS (Root Mean Square) function is proposed to detect the offset error component. The effectiveness of the proposed algorithm is verified through simulation and experiment results.

• The Transactions of the Korean Institute of Power Electronics
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• v.12 no.1
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• pp.27-36
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• 2007

This paper proposes a current control scheme of the PWM converters under nonideal source voltage conditions such as unbalance and distortion. For the distorted source voltage, the harmonic current controllers are introduced to the conventional current controller. These control loops can eliminate the 5th and 7th order harmonics which are hardly to be done by using filters. For the unbalanced source voltage, a negative sequence current controller is introduced either to reduce the DC-link voltage ripples or to eliminate the source current unbalance. Experimental results show the validity of the proposed control scheme.

• Journal of Power Electronics
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• v.15 no.2
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• pp.544-554
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• 2015

This paper presents a steady-state operation analysis of full-bridge series-resonant inverters focusing on the distorted load current due to low-quality-factor resonant circuits in induction heating and other applications. The regions of operation based on the zero-voltage switching (ZVS) and non-zero-voltage switching (NON-ZVS) operations of the asymmetrical voltage-cancellation control technique are identified. The effects of a distorted load current under a wide range of output powers are also analyzed for achieving a precise ZVS operating region. An experimental study is performed with a 1kW prototype. Simulation and experimental studies have confirmed the validity of the proposed method. An efficiency comparison between the variable frequency method and the conventional fixed-frequency method is provided.

• Journal of Power Electronics
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• v.17 no.3
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• pp.704-715
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• 2017

For three-phase synchronization applications, the synchronous reference frame phase-locked loop (SRF-PLL) is probably the most widely used technique due to its ease of implementation and satisfactory phase tracking performance under ideal grid conditions. However, under unbalanced and distorted grid conditions, its performance tends to worsen. To deal with this problem, a variety of filtering stages have been proposed and used in SRF-PLLs for the rejection of disturbance components at the cost of degrading the dynamic performance. In this paper, to improve dynamic performance without compromising the filtering capability, an effective hybrid filtering stage is proposed and incorporated into the inner loop of a quasi-type-1 PLL (QT1-PLL). The proposed filtering stage is a combination of a moving average filter (MAF) and a modified delay signal cancellation (DSC) operator in cascade. The time delay caused by the proposed filtering stage is smaller than that in the conventional MAF-based and DSC-based PLLs. A small-signal model of the proposed PLL is derived. The stability is analyzed and parameters design guidelines are given. The effectiveness of the proposed PLL is confirmed through experimental results.

• Proceedings of the KIPE Conference
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• 1998.07a
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• pp.129-133
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• 1998

This paper deals with a characteristic of output for high frequency resonant inverter type x-ray generator in short exposure time. In the same tube-voltage, the waveform is stable in long exposure time (200msec) but more decreasing exposure time (50msec), the waveform is distorted. The ripple factor of tube-voltage waveform distorted more and more increase tube-voltage and in this case output is also unstable. High-frequency resonant inverter type X-ray generator using PSU source which introduced in resent is stable tube-voltage waveform and low ripple factor.

• Journal of information and communication convergence engineering
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• v.5 no.3
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• pp.273-280
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• 2007

The numerical methods for finding the optimal parameters in 640 Gbps (16 channels $\times$ 40 Gbps) WDM system with optical phase conjugator (OPC) are proposed, which effectively compensate the distorted overall WDM channels. The considered optimal parameters are the OPC position and the dispersion coefficient of fibers. The numerical approaches are accomplished through two different procedures. One of these procedures is that the optimal OPC position is previously searched and then the optimal dispersion coefficient is searched at the obtained optimal OPC position. The other is the reverse of the above procedure. From the numerical results, it is confirmed that two optimal parameters depend on each other, but less related with the searching procedure. The methods proposed in this research will be expected to alternate with the method of making a symmetrical distribution of power and local dispersion in real optical link which is a serious problem of applying the OPC into multi-channels WDM system.