• Journal of Electrical Engineering and Technology
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• v.11 no.2
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• pp.367-376
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• 2016

This paper presents a cell balancing method for a single switch flyback converter with a multi-winding transformer. The conventional method using a flyback converter with a multi-winding transformer is simple and easy to control, but the voltage of each secondary winding coil might be non-uniform because of the unequal effective turn-ratio. In particular, it is difficult to control the non-uniform effect using turn-ratios because secondary coil has a limited number of turns. The non-uniform secondary voltages disturb the cell balancing procedure and induce an unbalance in cell voltages. Individual cell control by adding a switch for each cell can reduce the undesirable effect. However, the circuit becomes bulky, resulting in additional loss. The proposed method here uses the conventional flyback converter with an adjustment made to the output filters of the cells, instead of the additional switch. The magnitude of voltage applied to a particular cell can be reduced or increased according to the adjusted filter and the selected switching frequency. An analysis of the conventional converter configuration and the filter design method reveals the possibility of adequate cell balancing control without any additional switch on the secondary side.

• Proceedings of the KIPE Conference
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• 1999.07a
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• pp.671-674
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• 1999

In the PWM converter, PLL(Phase Locked Loop) is usually used as a tool which senses the angle of input voltage. This is sensitive to nois and needs additional hardware. In this work, we propose a sensorless control scheme of PWM converter using EKF(Extended Kalman Filter). EKF estimates a phase angle of input voltage from nonlinear state equation using measured phase currents. We control power factor and DC-link voltage utilizing the estimated phase angle. We demonstrate the effectiveness of the proposed estimation algorithm through simulations.

• Journal of Power Electronics
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• v.11 no.4
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• pp.507-511
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• 2011

This paper presents a single-switch buck converter with a ripple-free inductor current. In the proposed converter, the filter inductor current ripple is completely removed by utilizing an auxiliary circuit consisting of an additional winding of the filter inductor, an auxiliary inductor, and an auxiliary capacitor. Moreover, the ripple-free current characteristic is maintained under both light load and full load conditions. The theoretical analysis and performance of the proposed converter were verified with a 110W experimental prototype operating at a 107 kHz switching frequency.

• Korean Journal of Optics and Photonics
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• v.9 no.3
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• pp.151-155
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• 1998

A new Fabry-Perot tunable filter has been built with simple construction, which does not require any additional aligning and/or beam-confining components for the reduction of the diffraction loss. For this feature, one of the two fibers for the filter is processed to have a concave mirror whose curvature is the same as that of the wavefront of the Gaussian beam from the first fiber. After high reflection coatings, the two fibers are aligned to result in an FP filter whose bandwidth, free spectral range, and insertion loss is 1.47nm, 52nm, 5.6dB respectively.

• Proceedings of the KIEE Conference
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• 1993.11a
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• pp.323-325
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• 1993

In this paper, the decentralized suboptimal $H_2$ filtering problem is considered. An additional term is added to the centralized optimal $H_2$ filter so that the whole filter is decentralized. We derive a sufficient condition for existence of such decentralized filters. By employing the solution procedure for the exact model matching problem, we obtain a set of decentralized $H_2$ filters, and choose a suboptimal filter from this set of decentralized $H_2$ filters. Naturally the resulting filter is guaranteed to be stable.

• The Transactions of The Korean Institute of Electrical Engineers
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• v.57 no.9
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• pp.1612-1617
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• 2008

Since most disturbance observer (DOB) approaches have been limited to minimum-phase systems (or systems having no zero dynamics), we propose a new DOB structure that can be applied to non-minimum phase systems. The new structure features an additional system, which is called as V-filter, whose role is to yield a minimum phase system when connected with the plant in parallel. In order to design the V-filter systematically we first consider a class of linear systems that can be stabilized via PID controller. By inverting the controller's transfer function, we can simply construct the filter. A convenient way of designing V-filter is presented by using an iterative linear matrix inequality (LMI) algorithm. With an illustrative example the simulation result shows that substantial improvement in the performance has been achieved compared with the control system without the DOB.

• Proceedings of the KIEE Conference
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• 2000.07b
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• pp.1174-1176
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• 2000

This paper presents a new control strategy of the active power filter to compensate the fundamental and high order reactive power. Using the proposed control strategy, the calculation of active and reactive power of the load is not required. So the system configurations and the controller can be constructed very simply. To decrease the load of active power filter, the LC passive filter bank can be used without any additional strategy. In this paper, the algorithm of the proposed new control strategy is discussed and the experimental results are shown.

• Journal of Korea Society of Digital Industry and Information Management
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• v.17 no.2
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• pp.1-11
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• 2021

Salt and pepper is a type of impulse noise. It may appear due to an error in the image transmission process and image storage memory. This noise changes the pixel value at any position in the image to 0 (in case of pepper noise) or 255 (in case of salt noise). In this paper, we present an algorithm for SAP noise reduction. The proposed method consists of three steps. In the first step, the location of the SAP noise is detected, and in the second step, the pixel value of the detected location is restored using a weighted average of the surrounding pixel values. In the last step, a reliability matrix around the reconstructed pixels is constructed, and additional correction is performed with a weighted average using this. As a result of the experiment, the proposed method appears to have similar or higher objective and subjective image quality than previous methods for almost all SAP noise ratios.

• International Journal of Aeronautical and Space Sciences
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• v.14 no.1
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• pp.85-90
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• 2013

This paper presents a study on terrain referenced navigation (TRN). The extended Kalman filter (EKF) is adopted as a filter method. A Jacobian matrix of measurement equations in the EKF consists of terrain slope terms, and accurate slope estimation is essential to keep filter stability. Two slope estimation methods are proposed in this study. Both methods are based on the least-squares approach. One is planar regression searching the best plane, in the least-squares sense, representing the terrain map over the region, determined by position error covariance. It is shown that the method could provide a more accurate solution than the previously developed linear regression approach, which uses lines rather than a plane in the least-squares measure. The other proposed method is weighted planar regression. Additional weights formed by Gaussian pdf are multiplied in the planar regression, to reflect the actual pdf of the position estimate of EKF. Monte Carlo simulations are conducted, to compare the performance between the previous and two proposed methods, by analyzing the filter properties of divergence probability and convergence speed. It is expected that one of the slope estimation methods could be implemented, after determining which of the filter properties is more significant at each mission.

• Journal of Electrical Engineering and Technology
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• v.10 no.2
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• pp.653-658
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• 2015

This paper deals with an efficient optimization design method of a compact ultra wideband (UWB) filter which can improve the characteristics of the filter. The Evolution Strategy (ES) algorithm is adopted for the optimization and modified to suppress the ripple by inserting an additional step to the ES scheme. The algorithm has the ability to control the ripple of an insertion loss in a passband as a modified approach. During the modified ES, a structure of initial shape is changed a lot, while includes the stepped impedance (SI) and the composite right/left handed transmission line (CRLH-TL). And an optimized filter satisfies the UWB specifications on the stopband and passband with an acceptable insertion loss. The filter achieves a much developed shape, the size of $15{\times}14mm$, the 3dB bandwidth from 2.7 to 10.8GHz, the flat insertion-loss less than 1dB, the wide stopband with 12~20GHz, and an acceptable return loss.