• 대한전기학회:학술대회논문집
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• 대한전기학회 2001년도 하계학술대회 논문집 B
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• pp.986-988
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• 2001

This paper presents a digitally speed sensorless control system for induction motor with direct torque control (DTC). Some drawbacks of the classical DTC are the relatively large torque ripple in a low speed range and notable current pulsation during steady state. They are reflected speed response and increased acoustical noise. In this paper, the DTC quick response are preserved at transient state, while better qualify steady state performance is produced by space vector modulation (SVM). The system are closed loop stator flux and torque observer for wide speed range that inputs are currents and voltages sensing of motor terminal, model reference adaptive control (MRAC) with rotor flux linkages for the speed fuming signal at low speed range, two hysteresis controllers and optimal switching look-up table. Simulation results of the suggest system for the 2.2 [kW] general purposed induction motor are presented and discussed.

• 전력전자학회논문지
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• 제10권6호
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• pp.527-533
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• 2005

선형 하이브리드 스테핑 전동기는 간단한 구조와 저가의 구동 방식으로 위치 제어를 요구하는 일부 반도체 공정 및 사무실 자동화 기기 등에서 최근 각광을 받고 있다. 그러나, 구조가 간단한 반면 이로 인한 릴럭턴스 및 코깅 추력에 의한 리플 때문에 아직까지 고부가가치의 정밀 공정에는 적용이 제한되어 왔다. 본 논문에서는 선형 하이브리드 스테핑 전동기의 추력 리플 발생 원인을 분석하고 이를 통하여 리플 추력을 상쇄하는 고성능 폐루프 제어 방식을 제안한다. 실험실에서 제작된 선형 하이브리드 스테핑 전동기에 대한 다양한 실험 결과를 통하여 해석 및 제안된 방법의 타당성을 검증한다.

• Journal of Power Electronics
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• 제13권6호
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• pp.1032-1041
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• 2013

This paper investigates control algorithms for a doubly fed induction generator with a back-to-back three-level neutral-point clamped voltage source converter in medium voltage wind power systems under unbalanced grid conditions. Three different control algorithms to compensate for unbalanced conditions have been investigated with respect to four performance factors; fault ride-through capability, instantaneous active power pulsation, harmonic distortions and torque pulsation. The control algorithm having a zero amplitude of torque ripple shows the most cost-effective performance concerning torque pulsation. The least active power pulsation is produced by the control algorithm that nullifies the oscillating component of the instantaneous stator active and reactive powers. A combination of these two control algorithms depending on the operating requirements and the depth of the grid unbalance presents the most optimized performance factors under generalized unbalanced operating conditions leading to high performance DFIG wind turbine systems.

• Journal of Power Electronics
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• 제17권4호
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• pp.991-1003
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• 2017

The conventional sliding mode control (CSMC) has a number of problems. It may cause dc output voltage ripple and it cannot guarantee the robustness of the whole system for a matrix rectifier (MR). Furthermore, the existence of a filter can decrease the input power factor (IPF). Therefore, a novel global sliding mode control (GSMC) based on a hyperbolic tangent function with IPF compensation for MRs is proposed in this paper. Firstly, due to the reachability and existence of the sliding mode, the condition of the matrix rectifier's robustness and chattering elimination is derived. Secondly, a global switching function is designed and the determination of the transient operation status is given. Then a SMC compensation strategy based on a DQ transformation model is applied to compensate the decreasing IPF. Finally, simulations and experiments are carried out to verify the correctness and effectiveness of the control algorithm. The obtained results show that compared with CSMC, applying the proposed GSMC based on a hyperbolic tangent function for matrix rectifiers can achieve a ripple-free output voltage with a unity IPF. In addition, the rectifier has an excellent robust performance at all times.

• International Journal of Control, Automation, and Systems
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• 제1권3호
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• pp.351-357
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• 2003

A method of design optimization for minimization of force ripple and maximization of thrust force in a linear brushless permanent magnet motor without finite element analysis is represented. The design optimization method calculated the driving force in the function of electric and geometric parameters of a linear brushless PM motor using the sequential quadratic programming method. Using electric and geometric parameters obtained by this method, the normalized force ripple is reduced 7.7% (9.7% to 2.0%) and the thrust force is increased 12.88N (111.55N to 124.43N) compared to those not using design optimization.

• KIEE International Transaction on Electrical Machinery and Energy Conversion Systems
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• 제11B권4호
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• pp.156-163
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• 2001

In this paper an optimal switching angle control of a switched reluctance motor (SRM) drive system is investigated for achieving maximum energy conversion ratio. A new magnetizing method is proposed with a low switching frequency. The proposed algorithm maximizes the positive energy conversion region, which is directly related to the mechanical output, and reduces the reactive power region with the same field energy region. As a consequence, a torque ripple is also sufficiently reduced compared with that of the conventional switching angle magnetizing method. Experimental results show that the proposed scheme provides a high efficiency and a low ripple drive.

• Journal of Power Electronics
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• 제12권1호
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• pp.113-119
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• 2012

This paper describes the design and control of a phase shift full bridge converter with a current doubler, which can be used for the on-board charger for the lead-acid battery of electric forklifts. Unlike the common resistance load, the battery has a large capacitance element and it absorbs the entire converter output ripple current, thereby shortening the battery life and degrading the system efficiency. In this paper a phase shift full bridge converter with a current doubler has been adopted to decrease the output ripple current and the transformer rating of the charger. The charge controller is designed by using the small signal model of the converter, taking into consideration the internal impedance of the battery. The stability and performance of the battery charger is then verified by constant current (CC) and constant voltage (CV) charge experiments using a lead-acid battery bank for an electric forklift.

• 대한전기학회:학술대회논문집
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• 대한전기학회 2004년도 학술대회 논문집 정보 및 제어부문
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• pp.605-607
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• 2004

A class D digital audio amplifier with small size, low cost, and high quality is positively necessary in the multimedia era made of home theater system and the digital audio broadcasting (DAB). It is impossible to analyze the stability of the digital audio amplifier, which is based on the PWM signal processing. To solve this problem, the digital audio amplifier is analyzed using variable structure control theory which is one of nonlinear system theories. Moreover, the magnitude and the frequency of ripple signal, which generated by hysteresis in the comparator, is obtained using describing function which is useful to represent the input-output relation of nonlinear system.

• 대한전기학회:학술대회논문집
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• 대한전기학회 2006년도 추계학술대회 논문집 전기기기 및 에너지변환시스템부문
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• pp.92-94
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• 2006

Single phase switched reluctance motor has a high speed capability, due to its very robust rotor, and requires only one electronic power switch in its control circuitry. The latter feature considerably reduces the cost of the drive system. But it involves starting problem and strongly torque ripple, which means that the motor is not suitable for application that require constant torque or speed. To solve torque ripple and region of these problem, this paper presents a single phase Switched Reluctance Motor model with a barrier rotor pole. Also it is simulated the designed prototype model by FEM for the prediction of characteristics.

• 전력전자학회:학술대회논문집
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• 전력전자학회 2001년도 추계학술대회 논문집
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• pp.37-40
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• 2001

This paper is suggested an optimal switching angle of a switched reluctance motor drive system for maximum energy ratio. A new magnetizing method with a low-frequency increasing the energy conversion ratio that is related to the efficiency of motor is proposed As results, it improves the efficiency about 2[$\%$]. And a torque ripple is also reduced compared with that of the conventional switching angle magnetizing approach. In order to start softly regardless of a large ripple torque, the profile of phase current is predicted and current control mode was adapted when it is operated under the starting speed.