• Journal of Power Electronics
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• v.7 no.2
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• pp.109-117
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• 2007

In this paper, a novel proposal for a utility-interactive three-phase soft commutation sinewave PWM power conditioner with an auxiliary active resonant DC-link snubber is developed for fuel cell and solar power generation systems. The prototype of this power conditioner consists of a PWM boost chopper cascaded three-phase power conditioner, a single two-switch auxiliary resonant DC-link snubber with two electrolytic capacitors incorporated into one leg of a three-phase V-connection inverter and a three-phase AC power source. The proposed cost-effective utility-interactive power conditioner implements a unique design and control system with a high-frequency soft switching sinewave PWM scheme for all system switches. The operating performance of the 10 kW experimental setup including waveform quality, EMI/RFI noises and actual efficiency characteristics of the proposed power conditioner are demonstrated on the basis of the measured data.

• Proceedings of the KIEE Conference
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• 1992.07b
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• pp.1067-1070
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• 1992

Optimal Asymmetrical Pulse-width Modulated (APWM) technique for ac chopper is proposed which can improve the input power factor and eliminate the harmonics of output voltage up to a specified order, and also enables linear control of the fundamental component of the output voltage. The PWM switching patterns at the specified phase angle are obtained by Newton-Raphson method and theoretical comparisons are made with other PWM and APWM technique.

• Journal of Power Electronics
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• v.14 no.2
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• pp.362-368
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• 2014

This paper proposes a harmonic reduction approach for a pulse width modulation (PWM) AC-AC converters using Bee Colony Optimization (BCO). The optimal switching angles are provided by BCO to minimize harmonic distortions. The sequences of the PWM switching angles are considered as a technical constraint. In this paper, simulation results from various optimization techniques including BCO, Genetic Algorithm (GA), and Particle Swarm Optimization (PSO) are compared. The test results indicate that BCO can provide a better solution than the others in terms of power quality and power factor improvement. Lastly, experiments on a 200W AC-AC converter confirm the performance of the proposed switching pattern in reducing harmonic distortions of the output waveform.

• The Transactions of the Korean Institute of Power Electronics
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• v.11 no.5
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• pp.431-439
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• 2006

This paper proposes a new commutation circuit for a PWM Cuk AC-AC converter. The proposed commutation circuit utilizes a modified Undeland snubber as a commutation aid. The snubber circuit has some good features such as reduction of voltage/current stress of the main switches and improved efficiency. The experiment results show the adaptability and feasibility of the proposed commutation circuit.

• Journal of Power Electronics
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• v.15 no.1
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• pp.227-234
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• 2015

This paper presents the application of bee colony optimization (BCO) to obtain the optimal switching angles for single phase PWM AC choppers. The optimal switching angles are found in the region of 0-${\pi}$ based on the asymmetrical PWM technique. This PWM process results in improvements of the total harmonic distortion of the output voltage and in the input power factor. Simulation and experimental results are compared with the conventional PWM to verify the performance of the proposed PWM process.

• The Transactions of the Korean Institute of Electrical Engineers B
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• v.54 no.12
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• pp.609-615
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• 2005

A 30kW electrical power conversion system is developed for a variable speed wind turbine. In the wind energy conversion system(WECS) a synchronous generator with field current excitation converts the mechanical energy into electrical energy. As the voltage and the frequency of the generator output vary according to the wind speed, a 6-bridge diode rectifier and a PWM boost chopper is utilized as an ac-dc converter maintaining the constant dc-link voltage with only single switch control. An input current control algorithm for maximum power generation during the variable speed operation is proposed without any usage of speed sensor. Grid connection type PWM inverter converts dc input power to ac output currents into the grid. The active power to the grid is controlled by q-axis current and the reactive power is controlled by d-axis current with appropriate decoupling. The phase angle of utility voltage is detected using software PLL(Phased Locked Loop) in d-q synchronous reference frame. Experimental results from the test of 30kW prototype wind turbine system show that the generator power can be controlled effectively during the variable speed operation without any speed sensor.

• The Transactions of the Korean Institute of Power Electronics
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• v.3 no.2
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• pp.131-137
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• 1998

The solar cells should be operated at the maximum power point because its output characteristics are greatly fluctuated on the variation of insolation, temperature and load. Photovoltaic system needs an inverter which can interface the dc output power of solar cell with the residential ac load. The inverter has to supply a sinusoidal current and voltage to the load and the utility line with a high power factor. This paper proposes an utility interactive photovoltaic system designed with a step-up chopper and a PWM voltage source inverter. The step-up chopper operates in continuous mode by adjusting the duty ratio so that the photovoltaic system tracks the maximum power points of solar cell without any influence on the variation of insolation and temperature. The voltage source inverter operates in a manner that its output voltage is in phase with the utility voltage. The inverter supplies an ac power with high factor and low level of harmonics to the load and the utility power system.

• Proceedings of the KIPE Conference
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• 2014.07a
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• pp.142-143
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• 2014

본 논문에서는 Buck type의 단상 AC/AC 초퍼를 이용한 단상 voltage sag compensator를 제안한다. 제안된 회로는 sag보상 동작 시 사용된 변압기의 누설리액턴스가 단상 PWM Buck AC/AC converter에 미치는 영향이 작아 동작효율이 높고, sag가 발생하지 않는 상태일 때 입력과 출력이 절연되는 장점이 있다. 본 논문에서는 제안된 회로의 동작 및 특성을 설명하고, 타당성을 입증하기 위해 PSIM으로 시뮬레이션 하였다.

• Proceedings of the KIPE Conference
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• 2014.07a
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• pp.144-145
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• 2014

본 논문에서는 Buck type의 3상 AC/AC 초퍼를 이용한 3상 voltage sag compensator를 제안한다. 제안된 회로는 sag보상 동작 시 사용된 변압기의 누설리액턴스가 3상 PWM Buck AC/AC converter에 미치는 영향이 작아 동작효율이 높고, sag가 발생하지 않은 상태일 때 입력과 출력이 절연되는 장점이 있다. 본 논문에서는 제안된 회로의 동작 및 특성을 설명하고, 타당성을 입증하기 위해 PSIM으로 시뮬레이션 하였다.

• Proceedings of the KIPE Conference
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• 2003.07a
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• pp.106-109
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• 2003

This paper describes an AC voltage regulator using AC chopper and auxiliary transformer which is series connected with main input. It has many advantages such as fast voltage control, high efficiency and low THD. A detail study of step down AC voltage regulator is described and two kinds of novel step-up/down voltage regulator for AVR are proposed. The operation principle and PWM method of the proposed regulator are described. Experimental results show that it can be used as AC voltage regulator for special purpose very efficiently.