• 전력전자학회:학술대회논문집
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• 전력전자학회 2012년도 전력전자학술대회 논문집
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• pp.47-48
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• 2012

In generally, grid connected single-phase flyback inverter is operated as boundary or discontinuous conduction mode. However, the flyback inverter can be operated in continuous conduction mode (CCM) due to its operating conditions in spite of it is designed to operate under boundary or discontinuous conduction mode. This situation causes unintended distortion to output current. In this paper, a current shaping method on unfolding bridge to reduce the output current distortion.

• Journal of Electrical Engineering and Technology
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• 제3권2호
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• pp.243-253
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• 2008

This paper deals with the analysis, design, and implementation of a single phase AC-DC Zeta converter with high frequency transformer isolation and power factor correction(PFC) in two modes of operation, discontinuous current mode of operation(DCM), and continuous current mode of operation(CCM). A Digital Signal Processor(DSP) based implementation is carried out for validation of the Zeta converter developed design in discontinuous mode of operation. A comparison of both modes of operation is presented for a 1kW power rating from the point of view of steady state and dynamic behavior, power quality, simplicity, control technique, device rating, and converter size. The experimental results of a developed prototype of Zeta converter are presented for validation of the developed design. It is observed that CCM is most suitable for higher power applications where it requires some complex control and sensing of the additional variables.

• 대한전기학회:학술대회논문집
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• 대한전기학회 2002년도 추계학술대회 논문집 전기기기 및 에너지변환시스템부문
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• pp.200-203
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• 2002

This paper presents Continuous-current mode of $S^4$-PFC(Single-Stage Single-switch Power Factor Correction) converter. Proposed converter operates in the continueous current mode(CCM) at full load and discontinuous current mode(DCM) at light load. So, characteristic of proposed converter is no bus voltage stress and Zero Voltage Switching(ZVS) using resonant auxiliary circuit. And. This paper presents characteristic of $S^4$-PFC converter and effect of circuit parameter of proposed converter through the input inductor, PFC capacitor's variation. All of these theory and characteristic verified through the experiment with a 72W(12V, 6A), $90^{kHz}$ prototype converter.

• 전기학회논문지
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• 제65권3호
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• pp.419-427
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• 2016

This paper proposes a design method of LCL-filter for a grid-connected three-phase inverter using a discontinuous PWM (DPWM) method. When using a DPWM method, many harmonic voltages are generated in the inverter output compared to a continuous PWM (CPWM) method. Therefore, an optimized grid-connected filter design is required for a DPWM method. The proposed design method provides generalized formula to design accurate LCL-filter without trial and error procedures. An inverter side inductance is designed by analyzing the current ripple injected to the grid. The Optimized parameters of LCL-filter can be designed by analyzing the total harmonic distortion (THD) and the ripple attenuation factor of the output current. The proposed LCL filter design method is demonstrated by simulation and experimental results.

• 대한전기학회:학술대회논문집
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• 대한전기학회 2006년도 춘계학술대회 논문집 전기기기 및 에너지변환시스템부문
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• pp.347-350
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• 2006

The high efficiency full-bridge LLC resonant converter using a contact-less transformer is proposed for the photovoltaic power generation system. For the series resonance with a series capacitor, the LLC resonant converter utilizes the leakage inductance and magnetizing inductance of a contact-less transformer. Unlike the conventional series resonant converter operated to the continuous resonant current at above resonance frequency, the proposed converter operates to the discontinuous resonant current at the narrow frequency control range below resonance frequency. Due to the discontinuous mode resonant current, the proposed converter can be achieved the zero voltage switching (ZVS) in the primary switches and the zero current switching (ZCS) in the secondary rectification diodes without any auxiliary circuit. In this paper, the experimental results of the proposed full-bridge LLC resonant converter using a contact-less transfonner are verified on the simulation based on the theoretical analysis and the 150W experimental prototype.

• 전기학회논문지
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• 제58권7호
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• pp.1349-1355
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• 2009

This paper is studied on a novel power factor correction (PFC) AC-DC converter of high efficiency by soft switching technique. The input current waveform in the proposed converter is got to be a sinusoidal form composed of many a discontinuous pulse in proportion to the magnitude of a ac input voltage under the constant switching frequency. Therefore, the input power factor is nearly unity and the control method is simple. The proposed converter adding an electric isolation operates with a discontinuous current mode (DCM) of the reactor in order to obtain some merits of simpler control, such as fixed switching frequency, without synchronization control circuit used in continuous current mode (CCM). To achieve the soft switching (ZCS or ZVS) of control devices, the converter is constructed with a new loss-less snubber for a partial resonant circuit. It is that the switching losses are very low and the efficiency of the converter is high, Particularly, the stored energy in a loss-less snubber capacitor recovers into input side and increases input current from a resonant operation. The result is that the input power factor of the proposed converter is higher than that of a conventional PFC converter. This paper deals mainly with the circuit operations, theoretical, simulated and experimental results of the proposed PFC AC-DC converter in comparison with a conventional PFC AC-DC converter.

• Earthquakes and Structures
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• 제7권6호
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• pp.895-908
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• 2014

The main objective of critical excitation methods is to reveal the worst possible response of structures. This goal is accomplished by considering the uncertainties of ground motion, which is subjected to the appropriate constraints, such as earthquake power and intensity limit. The concentration of this current study is on the theoretical optimization aspect, as is the case with the majority of conventional critical excitation methods. However, these previous studies on critical excitation lead to a discontinuous power spectral density (PSD). This paper introduces some critical excitations which contain proper continuity in frequency domain. The main idea for generating such continuous excitations stems from the combination of two continuous functions. On the other hand, in order to provide a non-stationary model, this paper attempts to present an appropriate envelope function, which unlike the previous envelope functions, can properly cover the natural earthquakes' accelerograms based on multi-peak conditions. Finally, the proposed method is developed into the multiple-degree-of-freedom (M.D.O.F) structures.

• 전력전자학회논문지
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• 제18권4호
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• pp.297-304
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• 2013

This paper presents a improved control technique to overcome disadvantage when the inductor current of boost converter in PV system becomes DCM(Discontinuous Conduction Mode) due to the low insolation. MPPT(Maximum Power Point Tracking) output reference voltage could not be exactly followed by conventional dual-loop PI control method used typically because of the error between the actual current and measured current. Therefore, in this paper, Hybrid controller that changes the control method in DCM and CCM(Continuous Conduction Mode), and single state feedback controller are used to compensate that problem. The proposed control technique was verified by simulation using PSIM 9.0 and experiments.

• 대한전기학회:학술대회논문집
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• 대한전기학회 1990년도 추계학술대회 논문집 학회본부
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• pp.352-356
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• 1990

In this paper proposed a new analysis method that can be controlled DC separately excited motor using DC chopper. An analysis method can be broadly divided the state variables method and the state space averaging method. The state variable method is largely used for analysis method in the time area, but it is complicated analysis of the nonlinear circuit and modeling of the system. Therefore a boundary of the current continuous mode and discontinuous mode can be definited by the state space averaging method. Also this paper proposed a new approximation analysis method using state space averaging method in the discontinuous mode.

• 조명전기설비학회논문지
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• 제22권7호
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• pp.28-36
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• 2008

This paper presents a novel prototype of zero current switching pulse frequency modulation (ZCS-PFM )high frequency series resonant inverter using IGBT power module for electromagnetic induction eddy current heated roller in copy and printing machines. The operating principle and unique features of this voltage-fed half bridge inverter with two additional soft commutation inductor snubber are presented including the transformer modeling of induction heated rolling drum. This soft switching inverter can achieve stable zero current soft commutation under a discontinuous and continuous resonant load current for a widely specified power regulation processing. The experimental results and computer-aided analysis of this inverter are discussed from a practical point of view.