• 전력전자학회:학술대회논문집
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• 전력전자학회 1998년도 Proceedings ICPE 98 1998 International Conference on Power Electronics
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• pp.1-6
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• 1998

To achieve fast control action, direct control methods should be used. "Direct Mean Torque Control" (DMTC) combines the good dynamic performance of Direct Torque Control (DTC) with the advantages of inherently constant switching frequency and time equidistant control for implementation in a digital signal processor. Since DMTC is a predictive control algorithm, the model and its correction deserves special investigations. This paper proposes a steady-state Kalman filter which is well suited for fast computation.mputation.

• Journal of Electrical Engineering and Technology
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• 제5권4호
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• pp.538-544
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• 2010

This paper proposes an estimation algorithm for the separate primary and secondary leakage inductances of a three phase $Y-\Delta$ transformer using least squares method. The voltage equations from the primary and secondary windings are combined into a differential equation to estimate the separate primary and secondary leakage inductances in order to use the line current of the delta winding. Separate primary and secondary leakage inductances are obtained by applying least squares method to the differential equation. The performance of the proposed algorithm is validated under transient states, such as magnetic inrush and overexcitation, as well as in the steady state with various cut-off frequencies of low-pass filter. The proposed technique can accurately generate separate leakage inductances both in the steady and transient states.

• 전력전자학회논문지
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• 제7권2호
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• pp.158-164
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• 2002

본 논문은 기존의 1차 예측 기법과 반복 제어기법을 이용하여 LC 필터와 정류 부하 등의 비선형 부하를 가지는 UPS 인버터의 출력전압 파형의 개선에 관한 연구이다. 기존의 1차 예측 기법은 정류부하에 대하여 우수한 특성을 가지므로 출력전류의 예측에 적합하나 정류 부하와 같은 비선형적인 부하의 정상 상태 오차를 보상하기에는 충분하지 못한 단점을 가진다. 따라서, 정상상태 오차를 최소화 할 수 있는 반복제어 기법을 적용하여 UPS 출력전압을 개선시키고자 한다. 제안된 제어기법에 대한 타당성을 시뮬레이션으로 검증하고, 이를 바탕으로 LC 필터를 가지는 3 kVA, 60 Hz UPS시스템을 제작하여 실험으로 검증한다

• 전력전자학회:학술대회논문집
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• 전력전자학회 1998년도 Proceedings ICPE 98 1998 International Conference on Power Electronics
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• pp.153-158
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• 1998

In this paper, a prototype of the auxiliary resonant commutated snubber circuit(ARCS) with a high frequency transformer power regeneration loop is described for voltage source type sinewave inverter system. This is a new soft switching topology developed for three phase voltage source soft-switching inverter, active power filter and reactive power compensator has significant advantage of current rating reduction for auxiliary active switching devices. In addition, this paper presents a novel prototype of voltage-source soft switching space vector-modulated inverter with ARCS mentioned above, which is more suitable and acceptable for high-power utility interactive power conditioning, along with a digital control scheme. The steady-state operating analysis of ARCS has the remarkable features and the practical design procedure of this resonant snubber are illustrated on the basis of computer simulation analysis. The operating performance evaluations in the steady-state of this three phase voltage source soft switching inverter are discussed and compared with the three phase voltage source hard switching inverter.

• Journal of Power Electronics
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• 제10권4호
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• pp.419-427
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• 2010

A parallel control strategy in capacity proportion frequency allocation mode for shunt active power filters (APFs) is proposed to overcome some of the difficulties in high power applications. To improve the compensation accuracy and overall system stability, an improved selective harmonic current control based on multiple synchronous rotating reference coordinates is presented in a single APF unit, which approximately implements zero steady-state error compensation. The combined decoupling strategy is proposed and theoretically analyzed to simplify selective harmonic current control. Improved selective harmonic current control forms the basis for multi-APF parallel operation. Therefore, a parallel control strategy is proposed to realize a proper optimization so that the APFs with a larger capacity compensate more harmonic current and the ones with a smaller capacity compensate less harmonic current, which is very practical for accurate harmonic current compensation and stable grid operation in high power applications. This is verified by experimental results. The total harmonic distortion (THD) is reduced from 29% to 2.7% for a typical uncontrolled rectifier load with a resistor and an inductor in a laboratory platform.

• 한국전자통신학회논문지
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• 제4권3호
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• pp.224-229
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• 2009

본 논문은 LMS 알고리즘을 이용하여 적응횡단선 필터의 수렴 속도를 향상시키기 위한 효율적인 신호간섭 제어기법을 제안한다. 수신 데이터를 재사용하여 심볼 시간 주기에 계수들을 곱함으로써 적응되는 제안된 알고리즘의 수렴특성이 수렴 속도의 향상을 이론적으로 증명하기 위해 분석한다, 스텝-크기 매개변수 ${\mu}$가 증가됨에 따라 LMS 알고리즘의 수렴 속도가 제어된다. 고유치확산을 증가시킴에 따라 적응 등화기의 수렴속도를 천천히 제어하고 평균 자승 에러의 안정-상태 값을 증가시키는 효과를 나타내며 데이터-재사용 LMS 알고리즘이 적응횡단선 필터의 수렴속도를 (B+1)배만큼 증가시켜 신호간섭제어의 우수성을 입증한다.

• Journal of Astronomy and Space Sciences
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• 제26권1호
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• pp.59-74
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• 2009

Relative navigation system is presented using GPS measurements from a single-channel global positioning system (GPS) simulator. The objective of this study is to provide the real-time inter-satellite relative positions as well as absolute positions for two formation flying satellites in low earth orbit. To improve the navigation performance, the absolute states are estimated using ion-free GRAPHIC (group and phase ionospheric correction) pseudo-ranges and the relative states are determined using double differential carrier-phase data and singled-differential C/A code data based on the extended Kalman filter and the unscented Kalman filter. Furthermore, pseudo-relative dynamic model and modified relative measurement model are developed. This modified EKF method prevents non-linearity of the measurement model from degrading precision by applying linearization about absolute navigation solutions not about the priori estimates. The LAMBDA method also has been used to improve the relative navigation performance by fixing ambiguities to integers for precise relative navigation. The software-based simulation has been performed and the steady state accuracies of 1 m and 6 mm ($1{\sigma}$ of 3-dimensional difference errors) are achieved for the absolute and relative navigation using EKF for a short baseline leader/follower formation. In addition, the navigation performances are compared for the EKF and the UKF for 10 hours simulation, and relative position errors are mm-level for the two filters showing the similar trends.

• Journal of Power Electronics
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• 제15권5호
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• pp.1338-1347
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• 2015

DC injection is a critical issue in transformerless grid-connected inverters. DC injection control based on virtual capacitor has the advantages of low cost, low loss, high accuracy and easy implementation. In this paper, the principle of DC injection control based on virtual capacitor was analyzed. In addition, the applicable conditions, working process, steady state error and advantages were also discussed in detail. The design of the control parameters based on virtual capacitor was proposed in a grid-connected inverter with LCL filter. The robustness of the control parameters was also discussed. Simulation and experimental results verify the validity of the analysis and demonstrate that this research has a certain value in engineering applications.

• 대한전기학회:학술대회논문집
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• 대한전기학회 1996년도 하계학술대회 논문집 A
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• pp.295-299
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• 1996

When the current of a power converter is controlled with a digital controller, it generally shows the error due to execution time delay. The error may be considerable in such systems as active power filters wherein the current varies steeply even in steady state, as well as in transients. Therefore, it is of particular importance to compensate the time delay effect in a digitally-controlled active power filter. This paper introduces a modification of so-called predictive current control, by taking the control time delay into consideration. The results of simulation and experiment with a 10 kVA active power filter prototype show considerable improvement in current tracking capability, validating the proposed current control method.

• 전력전자학회:학술대회논문집
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• 전력전자학회 2001년도 Proceedings ICPE 01 2001 International Conference on Power Electronics
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• pp.737-740
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• 2001

This paper proposes a new ballast that is ignited by internal LC resonance of buck converter. In order to cancel the steady state current ripple, the proposed ballast utilizes the coupled inductor filter which minimizes the size and weight of the ballast. The operation mode of the proposed ballast is analyzed and the performance of the new ballast is verified by the experimental results from a HOW prototype ballast for metal halide discharge (MHD) lamp.