• 한국세라믹학회지
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• 제33권3호
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• pp.332-338
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• 1996

This study was investigated on the recycle feasibility of the waste AC(Ammonium Carbonate) solution produ-ced in a commercial AUC(Ammonium Uranyl Carbonate) conversion plant. AUC particles were produced with the AC solution which was prepared with AC solid-agent instead of ammonia and carbon-dioxide gases. As the results particles of monoclinic shapes has been obtained regardless of the pH change if the carbonate concentration is sufficient in the mother liquore. Also a lot of twinned or aggregated particles were formed in case of the increase of pH in the reaction system but not affected in the change of temperature. Consequen-tly the characteristics of the particles which converted for AUC were produced withAC solution to UO2, particles specific surface area shape sintered density and others were similar to that of the particles which were produced with gases only when the pellets are fabricated in the nuclear fuel manufacturing process So the waste AC solution which is produced in the commercial AUC conversion plant is possible to recycle.

• Journal of Power Electronics
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• 제19권1호
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• pp.24-33
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• 2019

A new modeling method for AC-AC switched capacitor converters (SCCs) is introduced in this study. The proposed analytical method aims to accurately describe the input-output characteristics of AC-AC SCCs and establish a mathematical model for static voltage conversion ratio and equivalent resistance, which are key performance metrics for SCCs. A quantitative analysis of converter regulation capability is addressed on the basis of the modeling method. In this analysis, the effects of the control parameters and individual components on SCCs are illustrated extensively. Component stresses, such as the peak value and transient variation of the voltage/current of the converter, are also presented. The effectiveness of the proposed method is verified by comparing it with the existing modeling method and applying it to an AC-AC SCC with a conversion ratio of three. Two 1 kW prototypes are built in a laboratory, and their experimental results exhibit good agreement with the theoretical analysis.

• 대한전기학회:학술대회논문집
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• 대한전기학회 2002년도 추계학술대회 논문집 전기기기 및 에너지변환시스템부문
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• pp.320-322
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• 2002

The paper presents an electrical model of a grid-connected wind energy conversion system (WECS) with a variable speed drive, a fixed pitch angle, a synchronous generator as a wind generator and AC-DC-AC conversion scheme for simulating dynamic behaviors and performance responding to varying wind speed input. The electric output of the WECS is controlled by the AC-DC-AC conversion scheme, the objective of which is to capture the maximum active power under varying wind conditions and to keep the voltage of WECS terminal bus at a specific level. Aerodynamic models are used to incorporate the power characteristics to wind speed. The modeling and simulation of the WECS are realized on PSCAD/EMTDC environment.

• 전력전자학회논문지
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• 제11권5호
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• pp.431-439
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• 2006

본 논문에서는 PMW Cuk AC-AC 컨버터를 위한 새로운 commutation 회로를 제안한다. 제안된 commutation 회로는 컨버터 전류의 commutation을 위하여 개선된 Undeland 스너버를 이용한다. 개선된 스너버 회로는 주 스위치의 전압/전류 스트레스 저감, 효율 개선과 같은 장점을 갖는다. 본 논문에서는 실험을 통하여 제안된 commutation 회로의 효과와 적용 가능성을 확인하였다.

• Journal of Power Electronics
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• 제3권4호
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• pp.249-258
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• 2003

This paper presents a high-efficient and cost effective three-phase AC/DC-DC/AC power conversion system with a single two-switch type active Auxiliary Resonant DC Link (ARDCL) snubber circuit, which can minimize the total power dissipation. The active ARDCL snubber circuit is proposed in this paper and its unique features are described. Its operation principle in steady-state is discussed for the three phase AC/DC-DC/AC converter, which is composed of PWM rectifier as power factor correction (PFC) converter, sinewave PWM inverter. In the presented power converter system not only three-phase AC/DC PWM rectifier but also three-phase DC/AC inverter can achieve the stable ZVS commutation for all the power semiconductor devices. It is proved that the proposed three-phase AC/DC-DC/AC converter system is more effective and acceptable than the previous from the cost viewpoint and high efficient consideration. In addition, the proposed two-switch type active auxiliary ARDCL snubber circuit can reduce the peak value of the resonant inductor injection current in order to maximize total system actual efficiency by using the improved DSP based control scheme. Moreover the proposed active auxiliary two-switch ARDCL snubber circuit has the merit so that there is no need to use any sensing devices to detect the voltage and current in the ARDCL sunbber circuit for realizing soft-switching operation. This three-phase AC/DC-DC/AC converter system developed for UPS can achieve the 1.8% higher efficiency and 20dB lower conduction noise than those of the conventional three-phase hard-switching PWM AC/DC-DC/AC converter system. It is proved that actual efficiency of the proposed three-phase AC/DC-DC/AC converter system operating under a condition of soft switching is 88.7% under 10kw output power.

• KIEE International Transaction on Electrical Machinery and Energy Conversion Systems
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• 제5B권3호
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• pp.277-282
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• 2005

This paper describes a step-down AC voltage regulator using an AC chopper and auxiliary transformer, which is a series connected to the main input. The detail design of the AC regulator, logic and PWM pattern of the AC chopper is described and the three-phase AC regulator using two single­phase AC choppers with a three transformer configuration is proposed for three-phase application. The proposed three-phase system has the advantages of lower system cost due to reduced switch number and gate driver circuit as well as advantages of decreased size and weight because it uses a series compensated scheme. The proposed AC regulator has many benefits such as fast voltage control, high efficiency and simple control logic. Experimental results indicate that it can be used as a step-down AC voltage regulator for power saving purposes very efficiently.

• 전력전자학회:학술대회논문집
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• 전력전자학회 2013년도 전력전자학술대회 논문집
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• pp.337-338
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• 2013

Combination the several type of single phase power conversion utilized simply topology are proposed in this paper. Totally four kind of converter are investigated, they are Boost AC/AC Converter, Buck AC/AC Converter, Boost AC/DC Converter, and Buck DC/AC Converter. Two types action mode are presented to determine the functional of circuit. First is AC chopper action mode, representation of the AC/AC converter. AC chopper action mode offered the sinusoidal current waveform, better power factor, faster dynamics, and smaller input/output filter. They present high robustness, offer safe commutation and have high efficiency. The second is full bridge action mode, determined the transformation AC to DC power and otherwise. Four switching devices and one magnetic contactor will establish the mode operation of circuit and manage the flow of power proceed in proper. The correction and advance of the kind of converter are verified by simulation.

• 전력전자학회논문지
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• 제17권3호
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• pp.230-237
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• 2012

This paper proposes an active-clamp ac-dc converter with direct power conversion that has a simple structure and achieves high efficiency. The proposed converter is derived by integrating the step-down ac chopper and the output-voltage doubler. The proposed converter provides direct ac-dc conversion and dc output voltage without using any full-bridge diode rectifier. The step-down ac chopper using an active-clamp mechanism serves to clamp the voltage spike across the main switches and provides zero-voltage turn-on switching. The resonant-current path formed by the leakage inductance of the transformer and the resonant capacitor of the output-voltage doubler achieves the zero-current turn-off switching of the output diodes. The operation principle of the converter is analyzed and verified. A 500W prototype is implemented to show the performance of the proposed converter. The prototype provides maximum efficiency of 95.1% at the full load.

• Journal of Power Electronics
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• 제13권3호
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• pp.419-428
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• 2013

The modular multilevel cascade converter (MMCC) is a new family of multilevel power converters with modular realization and a cascaded pattern for submodules. The MMCC family can be classified by basic configurations and submodule types. One member of this family, the Hexverter, is configured as Double-Delta Full-Bridge (DDFB). It is a novel multilevel AC/AC converter with direct power conversion and comparatively fewer required components. It is appropriate for connecting two three-phase systems with different frequencies and driving an AC motor directly from a utility grid. This paper presents the dq model of a Hexverter with both of its AC systems by state-space representation, which then simplifies the continuous time-varying model into a periodic discrete time-invariant one. Then a generalized multivariable optimal control strategy for regulating the Hexverter's independent currents is developed. The resulting control structure can be adapted to other MMCCs and is flexible enough to include other control criterion while guaranteeing the original controller performance. The modeling method and control design are verified by simulation results.

• 대한전자공학회:학술대회논문집
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• 대한전자공학회 1998년도 하계종합학술대회논문집
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• pp.962-965
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• 1998

In this paper, single-phase PWM AC to AC converter that operates with unit powr factor and sinusidal input line currents is presented. The currentcontrol of this converter is based on the predicted current control method with fixed switching frequency and the line currents track to reference currents within sampling time interval.