• 전력전자학회:학술대회논문집
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• 전력전자학회 2001년도 전력전자학술대회 논문집
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• pp.405-408
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• 2001

This paper investigates the problem of the speed estimation of conventional speed sensorless stator flux-oriented induction machine drive in the field weakening region and proposes a new speed estimation scheme to estimate speed exactly in transients in the field weakening region. The error included in the estimated rotor speed is removed by not a low pass filter but Kalman filter.

• 대한전기학회:학술대회논문집
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• 대한전기학회 1997년도 추계학술대회 논문집 학회본부
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• pp.476-478
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• 1997

A new speed detection method using low resolution incremental encoders, especially excellent in the low speed region and in the transient state, is proposed. The half period error of an incremental encoder is greater than the period error. So it's not recommended to quadruple the number of pulses per revolution, because it increase the ripple of speed. To overcome this restriction a speed detection, method has been proposed. But it requires so many latch circuits. Therefore we propose a new speed detection method that has different concept and has fewer latch circuits.

• 한국정보통신학회논문지
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• 제14권10호
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• pp.2299-2304
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• 2010

유도 모터의 센서리스벡터 제어시스템은 모터의 시정수를 이용하여 자극의 위치를 추정하는 제어 시스템으로서 중 고속영역의 경우 벡터 제어가 잘 구현된다. 그러나 저속의 경우 모터로부터 얻는 전압정보가 너무 작아서 벡터 제어기의 구현이 어렵다. 본 논문에서는 슬립 주파수 추정을 이용하여 저속에서의 센서리스벡터제어 문제점을 개선시켜 광범위한 속도 영역에서 벡터제어가 가능한 센서리스 벡터제어기를 설계하였다. 제어기의 성능은 실험을 통하여 확인하였다.

• 한국철도학회:학술대회논문집
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• 한국철도학회 2002년도 추계학술대회 논문집(I)
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• pp.440-445
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• 2002

In this paper, traction system for urban transit maglev system is proposed. Using vector control strategy to control magnitude and frequency of output voltage transiently is general. But in case of traction system for railway vehicle, it is impossible that adapt vector control because there is one-pulse mode in a high speed region. So this paper proposes the control strategy using vector control in a low speed region and slip frequency control in a high speed region. And also proposes overmodulation method that makes to change in one-pulse mode softly. The performance of traction system will be verified by simulation results using ACSL.

• 전력전자학회논문지
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• 제9권5호
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• pp.467-477
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• 2004

본 논문에서는 극저속 영역에서 서보 전동기 구동 장치의 관성을 추정하는 기법을 제안한다. 대개의 서보 시스템에서 저속 영역의 성능 향상을 위해 사용되는 순시 속도 관측기는 관성계수와 같은 기계계 파라미터의 변동에 민감하다. 이와 같은 문제를 해결하기 위해 방사형 기저 함수망(Radial Basis Function Networks)을 이용하는 전동기관성을 추정기법을 제안한다. 실험을 통하여 제안한 추정기법의 타당성을 검증한다.

• 풍력에너지저널
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• 제3권2호
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• pp.34-41
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• 2012

The paper is focusing on investigating the control characteristics of the baseline controller of 5 MW wind turbine provided by NREL(National Renewable Energy Laboratory). The baseline controller consist of two control logics, a maximum power tracking control below the rated wind speed and a constant power control above the rated wind speed. In the low wind speed, the mean generator power for changing the turbulent intensity and the optimal constant is studied through numerical simulations using FAST program. On the other hand, the constant power control logic and the constant control logic are compared in the high wind speed. It is confirmed that optimal constant is closely related to the turbulent intensity in low wind speed region and the constant torque control has better performance than the constant power control with respect to mechanical load in high wind speed region.

• 대한전기학회논문지:전기기기및에너지변환시스템부문B
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• 제53권9호
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• pp.552-561
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• 2004

This paper is concerned with a new speed sensorless induction motor scheme which can be successfully applied to at any speed including even zero speed. The proposed method is robust against rotor resistance variations. In addition, simultaneous on-line estimations of speed and rotor resistance are realized based on a feedforward type torque control approach. The rotor flux with a low frequency sinusoidal waveform has been utilized to help the simultaneous estimation for both speed and rotor resistance. The control scheme has no current minor loop to determine voltage references. Since the proposed estimation does not depend on any derivative terms of currents and stator voltages, it offers a good performance at extremely low speed region for sensorless induction motor. Furthermore, the proposed control is simply using motor parameters and stator currents without determining any PI gains for current feedback and any signal injection for the rotor resistance estimation. Finally, both simulation and experimental results are given to show the effectiveness of this method.

• Journal of Mechanical Science and Technology
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• 제19권7호
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• pp.1449-1459
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• 2005

This paper shows the results of local flow speed measurement using tunable AC thermal anemometry, which is suitable for the accurate measurement of wide range flow speed. The measurement accuracy is verified through the comparison between the measurement data and the analytic solution of the sensor temperature oscillation in stationary fluid. The relation between the phase lag and the flow speed is experimentally investigated at various conditions. The measurement sensitivity for low flow speed improves in a low frequency region and that for high flow speed improves in a high frequency region. Also, the sensitivity increases with decreasing thermal conductivity of the surrounding fluid. The local flow speed could be measured as low as 1.5 mm/s and the highest measurement resolution was 0.05 mm/s in the range of 4.5 $\~$5.0 mm/s at 1 Hz in this experiment.

• 한국항공우주학회지
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• 제37권1호
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• pp.17-27
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• 2009

압축성 영역에서 개발된 2상 유동 RoeM과 AUSMPW+를 전 마하수 영역 해석을 위해 예조건화 하였다. 압축성 영역에서 개발된 풍상차분 수치기법들은 수치점성에서 음속을 포함하는 항들을 갖고 있는데, 이는 비압축성 영역에서 관련 수치점성 크기를 지나치게 크거나 작게 만들어 해의 정확도를 떨어뜨리거나 수치 불안정 현상을 일으킨다. 따라서 예조건화된 시스템 고유값을 수치점성에 고려하여 전 마하수 영역에서 해의 정확성을 확보하였고, 점근 분석을 통해 개발된 수치기법이 비압축 극한 영역에서 보존형 지배방정식과 일관됨을 확인하였다. 수치 예제들을 통해 예조건화된 2상 유동 RoeM과 AUSMPW+가전 마하수 영역에서 합리적인 해를 도출함을 알 수 있었다.

• 유체기계공업학회:학술대회논문집
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• 유체기계공업학회 2005년도 연구개발 발표회 논문집
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• pp.655-660
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• 2005

The feasible range of design variables for centrifugal pumps have been investigated. The present study has suggested a searching procedure to find the feasible ranges using only non-dimensional parameters. The results in the typical specific speed region and the low specific speed region have been presented.