• The Transactions of the Korean Institute of Power Electronics
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• v.7 no.3
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• pp.289-296
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• 2002

New discrete-time modeling and simulation techniques are proposed which take advantages of the special features of PWM converter power stages and their compensation circuits. These techniques provide reduction of system order, and allow for the faster simulation without any numerical convergence problem. A buck converter with two-stage output filter Is employed to confirm the usefulness of the proposed techniques. The simulation results show these techniques can simulate the responoes of PWM converter system up to high frequencies.

• Proceedings of the KIEE Conference
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• 2009.07a
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• pp.1017_1018
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• 2009

LLC 하프브리지 공진형 컨버터는 일반적으로 게이트 구동드라이버, 구형파 발생부, 공진회로 및 정류회로로 구성되어 있다. 구형 파발생기는 두 개의 스위치 소자가 각각 50%의 주기와 약간의 데드타임을 가지고 반복하여 동작함으로써 구형파 전압을 발생하며, 공진회로에 구형파 전압이 인가되어도 높은 차수의 고주파 전류를 필터링하여 기본적으로 정현파 전류만 흐르도록 한다. 본 연구에서는 LLC 컨버터를 이용하여 LED를 구동을 하였고 시뮬레이션 결과를 실제 실험을 통해서 비교하였다.

• The Journal of the Acoustical Society of Korea
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• v.15 no.5
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• pp.30-37
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• 1996

In the communication system, adaptive equalizer using LMS algorithm has slow convergence rate in spite of effectiveness and simplicity. In this paper, we designed the wavelet transform based adaptive equalizer to overcome this problem. The performance of this new approach is compared with that of the time domain LMS algorithm by convergence rate with respect to change of channel distortion and filter order. As a result, the wavelet transform based adaptive equalizer shows the improvements in the speed of convergence compared with LMS algorithm based adaptive equalizer.

• The Transactions of The Korean Institute of Electrical Engineers
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• v.65 no.6
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• pp.1019-1025
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• 2016

This paper proposes a parallel reduced-order square-root unscented Kalman filter for state estimation of a sensorless permanent-magnet synchronous motor. The appearance of an unscented Kalman filter is caused by the linearization process error between a real system and classical Kalman model. The unscented transformation can make a more accurate Kalman model. However, the complexity is its main drawback. This paper investigates the design and implementation of the proposed filter with Potter and Carlson square-root form. The proposed parallel reduced-order square-root unscented Kalman filter reduces memory and code size, and improves numerical computation. And the performance is not significantly different from the unscented Kalman filter. The experimentation is performed for the verification of the proposed filter.

• Proceedings of the KIPE Conference
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• 2010.07a
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• pp.448-449
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• 2010

This paper proposes a sensorless control strategy for the Interior Permanent Magnet Synchronous Motor (IPMSM) by using the parallel reduced-order Extended Kalman Filter. The sensorless control strategy is composed with two EKFs alternately computed every sampling period with a new model. The new model is based on the extended electromotive force (EEMF) which has a simple structure, making position estimation possible without approximation. The proposed strategy can save computation time and estimate rotor speed and position. To verify the merit of the proposed strategy, simulation and experimental results validate the theoretical analysis and show the feasibility of the proposed control strategy.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.17 no.1
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• pp.11-19
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• 1992

This paper proposes a reduced order method which reduces passband error by changing controllability and observability gramian based on weighted functions in the linear time invariant system. In the case that the 4-order model is the reduced to 3-order model in the low-pass filter, the QEI in the proposed method is improved to 6.15724 compared to 10.16464 in the balanced realization method and the sensitivity is improved to 5.45962 compared to 7.790568. The frequency property curves show that the proposed method is superior to the balanced realization method.

• Proceedings of the KIEE Conference
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• 1998.11a
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• pp.171-175
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• 1998

This paper proposes a speed sensorless vector control of induction motor using a minimum-order EKF(extended kalman filter). Minimum-order EKF has the advantage of reducing the computational estimation cost because the stator current is not estimated. EKF does not deteriorate the performance of the overall speed control system, even though the measurements are relatively noisy. The estimated rotor speed is used for vector control and overall speed control. Computer simulations of the speed sensorless vector control are carried out to test the usefulness of the minimum-order EKF algorithm.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.28 no.1
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• pp.49-60
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• 2017

In this paper, we presented the result of the study on high-power handling capability of the X-band circular waveguide cavity filter configured at the output of high power amplifier(120 W) for geostationary satellites. The dual mode circular waveguide cavity filter with 6th order is selected and the physical model of the filter is designed after determination of the size of resonator from mode chart. Multipactor margin analysis is performed by the SEM method and the VMF method. The result shows that the VMF method predicts lower multipactor breakdown thresholds than the SEM method. Evaluating the multipactor margin obtained by the VMF method to ECSS criteria, we could decide to perform multipactor test. The multipactor test conducted in ESA facility shows that multipactor did not occur even until the RF power increased up to 540 W. In consequence, by both analysis and test, we could verify that the X-band circular waveguide cavity filter has the sufficient high-power handling capability to operate on orbit.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.40 no.1
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• pp.1-8
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• 2016

In this study, we propose a control algorithm for Inertially Stabilized Platforms (ISP), which combines Disturbance Observer (DOB) with conventional proportional integral derivative (PID) control algorithm. A single axis ISP system was constructed using a direct drive motor. The joint friction was modeled as a nonlinear function of joint speed while the accuracy of the model was verified through experiments and simulation. In addition, various Q-filters, which have different orders and relative degrees of freedom (DOF), were implemented. The stability and performance of the ISP were compared through experimental study. The performance of the proposed PID-plus-DOB algorithm was compared with the experimental results of the conventional double loop PID control under artificial vehicle motion provided motion simulator with six DOF.

• Journal of the Microelectronics and Packaging Society
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• v.28 no.2
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• pp.39-44
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• 2021

In this paper, two types of BPF(Band Pass Filter) which are hair-pin and interdigital have been designed for millimeter-wave application using two types of material which are LCP(Liquid Crystal Polymer) and PTFE(Polytetrafluoroethylene) and also, their performances such as bandwidth, insertion loss, and in-band flatness are compared. The proposed BPF are designed as third-order filters, and their pass band is from 26.5 GHz to 27.3 GHz. Interdigital BPF using PTFE substrate has most wide -3 dB S21 bandwidth of 7.8 GHz and hair-pin BPF using LCP substrate has most narrow -3 dB S21 bandwidth among the proposed four BPF. For in-band insertion loss, hair-pin BPF using PTFE substrate achieves low insertion loss better than -0.667 dB, and hair-pin BPF using LCP substrate exhibits relatively high insertion loss among the proposed four BPF better than -0.937 dB. However, the maximum difference in insertion loss performance among the proposed four BPF is 0.27 dB, which is too small to negligible. For in-band flatness, interdigital BPF using PTFE substrate shows greatest performance of 0.017 dB, and hair-pin BPF using LCP substrate exhibits the lowest performance of 0.07 dB. There are tiny difference in in-band flatness performance of 0.053 dB. As a results, it is considered that the BPF using LCP substrate can derive the performances similar to that of the BPF using PTFE substrate in Millimeter-wave band.