• Journal of Power Electronics
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• v.15 no.2
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• pp.399-410
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• 2015

A 6.5 V/50 kA high-frequency switching power supply (HSPS) system composed of 10 power modules is developed to meet the requirements of copper-foil electrolysis. The power module is composed of a two-leg pulse width modulation (PWM) rectifier and a DC/DC converter. The DC/DC converter adopts two full-wave rectifiers in parallel to enhance the output. For the two-leg PWM rectifier, the ripple of the DC-link voltage is derived. A composite control method with a ripple filter is then proposed to effectively improve the performance of the rectifier. To meet the process demand of copper-foil electrolysis, the virtual impedance-based current-sharing control method with load current full feedforward is proposed for n-parallel DC/DC converters. The roles of load current feedforward and virtual impedance are analyzed, and the current-sharing control model of the HSPS system is derived. Virtual impedance is used to adjust the current-sharing impedance without changing the equivalent output impedance, which can effectively reduce current-sharing errors. Finally, simulation and experimental results verify the structure and control method.

• Journal of the Korean Solar Energy Society
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• v.38 no.5
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• pp.27-36
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• 2018

The purpose of this paper is to apply the numerical solution procedure to compute conduction time series factors (CTSF) for construction materials with large thermal capacities. After modifying the procedure in Ref. [9], it is applied to find the CTSF for the wall type 19 and the roof type 18 of ASHRAE. The response periods for one hr pulse load are longer than 24hrs for these wall and roof. The CTSF generated using modified procedure agree well with the values presented in the ASHRAE handbook. The modified procedure is a general procedure that can be applied to find CTSF for materials with complex structures. For the large thermal capacity materials, it should be checked whether thermal response period of the material is over 24hr or not. With suggested solution procedure, it is easy to check the validity of the CTSF based on 24hr period.

• Journal of the Institute of Electronics and Information Engineers
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• v.52 no.2
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• pp.89-96
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• 2015

This paper presents a high efficiency, PSM/DCM/CCM triple mode boost DC-DC converter for mobile application. This device operates at Pulse-Skipping Mode(PSM) when it enters light load, and otherwise operate the operating frequency of 1.4MHz with Pulse-Width Modulation(PWM) mode. Especially in order to improve the efficiency during the Discontinuous-Conduction Mode(DCM) operation period, the reverse current prevention circuit and oscillations caused by the inductor and the parasitic capacitor to prevent the Ringing killer circuit is added. The input voltage of the boost converter ranges from 2.5V ~ 4.2V and it generates the output of 4.8V. The measurement results show that the boost converter provides a peak efficiency of 92% on CCM and 87% on DCM. And an efficiency-improving PWM operation raises the efficiency drop because of transition from PWM to PFM. The converter has been fabricated with a 0.18um Dongbu BCDMOS technology.

• The Transactions of the Korean Institute of Power Electronics
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• v.15 no.2
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• pp.150-158
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• 2010

The operational characteristics of a resonant DC/DC converter, which can harvest thermoelectric energy, is analyzed, depending on the relative magnitudes of the input voltage and the load voltage. The resonant converter consists of LC resonant circuit connected to DC input source and a resonant pulse converter in which the input energy is transferred to the load as the resonant capacitor voltage is peak. The resonant capacitor doubles the input voltage by the resonance phenomenon. By the relative magnitude between the input voltage and the output voltage, the resonant DC/DC converter operates in three different modes. For boost mode, the peak voltage of the resonant capacitor is smaller than the load voltage. For hybrid mode, the peak voltage of the resonant capacitor is bigger than the load voltage and every switching period has both the boost mode and the direct mode. For the direct mode, the input voltage is bigger than the load voltage and the converter transfers directly the input energy to the load without the switching operation. Operation principles and the feasibility of the converter for the thermoelectric energy harvesting are verified with PSPICE simulation and experiment.

• Proceedings of the Korean Society for Technology of Plasticity Conference
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• 2008.10a
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• pp.263-266
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• 2008

This paper is concerned with the analysis of elasto-plastic stress waves in a mode I semi-infinite cracked solid subjected to Heaviside pulse load. This study adopts a time-discontinuous variational integrator based on Hamiltonian in order to reduce the numerical dispersive and dissipative errors. This also utilizes an integration scheme of the constitutive model with 2nd-order accuracy which is formulated on the strain space for a rate and temperature dependent material model. Finite element analyses of elasto-plastic stress waves are carried out in order to compare the accuracy between a conventional Galerkin method and the time- discontinuous variational integrator.

• Proceedings of the KIEE Conference
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• 2002.07b
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• pp.1103-1105
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• 2002

A conventional AC-DC boost converter has much variation of input current as more increased the load or output voltage by the hysterical control method that is comparing area of current pulse by using PWM method and integration to sinusoidal input current. To improve the problems. in this paper, we propose the single-phase voltage doubler AC-DC converter circuit using the capacitor for boost:confirm characteristics of normal and transition state by using simulation, be stabilized voltage of doubler capacitor for boost, and Identify to get the sinusoidal input current with unity power factor.

• Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
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• v.27 no.1
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• pp.53-60
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• 2013

In this paper, a control algorithm for active power filter (APF), which compensates for the harmonics and power factor, boosting the DC-link voltage is proposed. The proposed scheme employs a pulse-width-modulation (PWM) voltage-source inverter. A simple algorithm to detect the load current harmonics is also proposed. The APF and charging circuit are implemented in one inverter system. Finally, the validity of the proposed scheme is investigated with simulated and experimental results for a prototype APF system rated at 3kVA.

• Journal of Power Electronics
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• v.12 no.1
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• pp.33-39
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• 2012

This paper describes operating and capacitor voltage balancing of the modular multilevel converter. The paper focuses on sizing of the cell capacitor and establishes approximate expressions for the capacitor voltage. Simulations and experiments results obtained from three-level modular converter are used to demonstrate its viability in medium voltage applications. It is shown that the modular converter can operate over the full modulation index linear range independent of load power factor.

• 제어로봇시스템학회:학술대회논문집
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• 2003.10a
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• pp.1867-1870
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• 2003

The analysis and simulation are the method to study the behavior, response, and specification of the driver device. This paper proposes brushless DC drive which using the vector control technique. The encoder is used detect the rotor position and decode to Three-phase step signal. The step signal is modulated with triangle signal and change to the pulse width modulation (PWM) signal. The PWM signal is used for control the input power of the motor based on the vector control technique. The experimental results of the driver circuit and motor response performed under the following condition: as the motor was started, change the load torque, and vary the supply voltage. The experimental performs with a dynamometer and the test results are compared to the simulation method is the same result.

• Structural Engineering and Mechanics
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• v.75 no.3
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• pp.357-367
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• 2020

The objective of this article is investigation of dynamic response of thick multilayer functionally graded (FG) beam under generalized dynamic forces. The plane stress problem is exploited to describe the constitutive equation of thick FG beam to get realistic and accurate response. Applied dynamic forces are assumed to be sinusoidal harmonic, sinusoidal pulse or triangle in time domain and point load. Equations of motion of deep FG beam are derived based on the Hamilton principle from kinematic relations and constitutive equations of plane stress problem. The numerical finite element procedure is adopted to discretize the space domain of structure and transform partial differential equations of motion to ordinary differential equations in time domain. Numerical time integration method is used to solve the system of equations in time domain and find the time responses. Numerical parametric studies are performed to illustrate effects of force type, graduation parameter, geometrical and stacking sequence of layers on the time response of deep multilayer FG beams.