• 전기학회논문지P
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• 제61권4호
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• pp.161-167
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• 2012

Energy conversion systems such as power inverters and converters are basically significant in establishing photovoltaic power systems to enhance power effectiveness. This paper proposes a new converter control method by using the Lyapunov redesign approach. We construct the proposed control mechanism linearly composed of nominal control and auxiliary control laws. The former is generally designed through a well-known power electronic technology and the latter is implemented to compensate real-time control error due to uncertain natures of converter systems in practice. For realizing adaptive control capability in the proposed control mechanism, a control parameter vector is estimated by utilizing a steepest descent based optimization method. We carry out numerical simulation with Matlab(c) software to demonstrate reliability of the proposed converter control system and conduct a comparative study to prove its superiority by comparing with a generic converter control methodology.

• Journal of Power Electronics
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• 제18권4호
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• pp.975-984
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• 2018

This work presents a high efficiency phase shifted full bridge (PSFB) DC-DC converter for use in the second stage of a battery charger for neighborhood electrical vehicle (EV) applications. In the design of the converter, Lithium-ion battery cells are preferred due to their high voltage and current rates, which provide a high power density. This requires wide range output voltage regulation for PSFB converter operation. In addition, the battery charger works with a light load when the battery charge voltage reaches its maximum value. The soft switching of the PSFB converter depends on the dead time optimization and load condition. As a result, the converter has to work with soft switching at a wide range output voltage and under light conditions to reach high efficiency. The operation principles of the PSFB converter for the continuous current mode (CCM) and the discontinuous current mode (DCM) are defined. The performance of the PSFB converter is analyzed in detail based on wide range output voltage and load conditions in terms of high efficiency. In order to validate performance analysis, a prototype is built with 42-54 V / 15 A output values at a 200 kHz switching frequency. The measured maximum efficiency values are obtained as 94.4% and 76.6% at full and at 2% load conditions, respectively.

• 한국자동차공학회논문집
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• 제12권3호
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• pp.101-108
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• 2004

A FEM-based efficient method is developed for the shape optimization of 2-D structures. The combined SLP and Simplex method are coupled with finite element analysis. Selected set of master nodes on the design boundaries are employed as design variables and assigned to move towards their normal directions. The other nodes along the design boundaries are grouped into the master node. By interpolating the repositioned master nodes, the B-spline curves are formed so that the rest mid-nodes efficiently settle down on the B-spline curves. Mesh smoothing scheme is also applied for the nodes on the design boundary to maintain most finite elements in good quality. Finally, a numerical implementation of optimum design of an automobile torque converter piston subjected to pressure and centrifugal loads is presented. The results shows additional weight up to 13% may be saved after the shape optimization.

• Journal of Power Electronics
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• 제19권5호
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• pp.1108-1121
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• 2019

The non-inverting buck-boost converter (NIBB) is a step-up and step-down DC-DC converter suitable for wide-input-voltage-range applications. However, when the input voltage is close to the output voltage, the NIBB needs to operate in the buck-boost mode, causing a significant efficiency reduction since all four switches operates in the PWM mode. Considering both the current stress limitation and the efficiency optimization, a novel design methodology for the optimal phase-shift modulation of a NIBB in the buck-boost mode is proposed in this paper. Since the four switches in the NIBB form two bridges, the shifted phase between the two bridges can serve as an extra degree of freedom for performance optimization. With general phase-shift modulation, the analytic current expressions for every duty ratio, shifted phase and input voltage are derived. Then with the two key factors in the NIBB, the converter efficiency and the switch current stress, taken into account, an objective function with constraints is derived. By optimizing the derived objective function over the full input voltage range, an offline design methodology for the optimal modulation scheme is proposed for efficiency optimization on the premise of current stress limitation. Finally, the designed optimal modulation scheme is implemented on a DSPs and the design methodology is verified with experimental results on a 300V-1.5kW NIBB prototype.

• Journal of Electrical Engineering and Technology
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• 제13권1호
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• pp.333-344
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• 2018

This proposed paper aims for the high efficiency contactless power transfer in household dc power distribution. A 300 W five-level diode clamped multi-level converter with 300 Vdc input dc link bus is employed for the power transferring task and the output voltage range is controlled at 48 Vdc. The inner and outer solenoid coils are used for inductive power transfer (IPT) transformer with the 200 kHz switching frequency for designed power density. Therefore, to achieve the converter efficiency above 95%, the LLC series resonant with fundamental harmonic analysis (FHA) and the calculated switching angles are used as an optimized tool for designing the system resonant tank. The validations of this approached topology are illustrated in both MATLAB/Simulink simulation and implementation.

• 한국자동차공학회논문집
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• 제6권6호
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• pp.15-23
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• 1998

A three dimensional simulation of the fluid flow in an automotive torque converter was conducted adopting the mixing plane model implemented in the computational fluid dynamics program CFD-ACE. The present numerical results for performance characteristics showed a good agreement with the experimental results. In the flow of the torque converter, recirculating flow regimes were found mostly at the suction side of each element, which caused the performance decrease. The recirculating flow can be minimized by the optimization of the blade geometries.

• 제어로봇시스템학회:학술대회논문집
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• 제어로봇시스템학회 1990년도 한국자동제어학술회의논문집(국내학술편); KOEX, Seoul; 26-27 Oct. 1990
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• pp.96-100
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• 1990

Dynamic modelling and controller design technique for constant-frequency series resonant converter with buck type preregulator are mainly described in this paper. An equivalent circuit model is derived and a state equation is developed from this model. To improve the dynamic performance, a negative feedback of inductor current is added to the proportional and integral control of output voltage. Furthermore, an optimization technique with prescribed eigenvalue region is applied to the determination of feedback gains. With the presented design method, much better dynamic performance can be obtained.

• 제어로봇시스템학회:학술대회논문집
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• 제어로봇시스템학회 1987년도 한국자동제어학술회의논문집; 한국과학기술대학, 충남; 16-17 Oct. 1987
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• pp.664-666
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• 1987

In this study, the computation of optimum operating conditions for catalytic oxidation of sulfur dioxide to sulfur trioxide in CONVERTER which determines the yield ultimately in sulfuric acid plant is performed on an IBM/XT computer. The process simulator of rigorous converter model including mass & energy balance equations and supporting equations is linked to optimizer, which produces the desired results successfully.

• 전력전자학회:학술대회논문집
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• 전력전자학회 2015년도 전력전자학술대회 논문집
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• pp.159-160
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• 2015

Recently, it is increased to use the portable device with small size. It is also increasing for demand of a small size adapter. To reduce the size of components, switching frequency has to be increased. But it causes higher switching loss and temperature of components. Especially, the temperature of adapter must be limited because adapter can be easily touched when portable device is being charged. To reduce temperature of adapter, high efficiency is essential. To solve this problem, this paper proposes design of resonance frequency optimization for LLC converter with high efficiency and low temperature of passive components.

• Journal of Power Electronics
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• 제12권2호
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• pp.368-376
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• 2012

This paper deals with an optimization approach of 3D space placement of power components under volume and thermal constraints. It consists in optimizing semiconductors positions on a heat sink by respecting the components junction temperatures and minimizing the heat sink size. The aim is to remove risks on the 3D converter components placement and ensure their effective integration before carrying out the first physical prototype. This approach is based on coupling an optimization environment with a thermal finite element simulation tool. A pre-sizing step using analytical models is performed to set the optimization computations coupled to numerical simulation.