• Journal of Electrical Engineering and Technology
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• 제11권2호
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• pp.405-415
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• 2016

This paper presents a model predictive control for shunt active power filters in synchronous reference frame using space vector pulse-width modulation (SVPWM). The three phase load currents are transformed into synchronous rotating reference frame in order to reduce the order of the control system. The proposed current controller calculates reference current command for harmonic current components in synchronous frame. The fundamental load current components are transformed into dc components revealing only the harmonics. The predictive current controller will add robustness and fast compensation to generate commands to the SVPWM which minimizes switching frequency while maintaining fast harmonic compensation. By using the model predictive control, the optimal switching state to be applied to the next sampling time is selected. The filter current contains only the harmonic components, which are the reference compensating currents. In this method the supply current will be equal to the fundamental component of load current and a part of the current at fundamental frequency for losses of the inverter. Mathematical analysis and the feasibility of the suggested approach are verified through simulation results under steady state and transient conditions for non-linear load. The effectiveness of the proposed controller is confirmed through experimental validation.

• 한국광학회지
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• 제12권3호
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• pp.230-234
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• 2001

반전대칭이 없는 광굴절결정에 있어 위상접합이 만족되지 않은 상태에서 발생된 제2고조파의 세기가 외부전기장에 의존한다는 사실을 이용하여 광굴적결정의 광굴절율 변형현상에 관한 중요상수를 측정할 수 있는 방법을 개발하였다. 마커무늬의 전기장의존도에 관한 근사식을 구하였고 이를 이용하여 제2고조파의 세기변화로부터 공간전하장의 크기를 측정할 수있었다. 실험적으로 congruent $LiNbO_3$에 빛을 두가지 다른 세기로 비추어 유도되는 공간저하장의 시간의존성을 조사하였고 측정결과를 근사식과 비교분석하여 $LiNbO_3$의 광기전력상수, 암전도상수 및 광전도상수를 결정할 수 있었다.

• Structural Engineering and Mechanics
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• 제17권1호
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• pp.1-14
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• 2004

Numerical solution to linear bending analysis of circular plates is obtained by the method of harmonic differential quadrature (HDQ). In the method of differential quadrature (DQ), partial space derivatives of a function appearing in a differential equation are approximated by means of a polynomial expressed as the weighted linear sum of the function values at a preselected grid of discrete points. The method of HDQ that was used in the paper proposes a very simple algebraic formula to determine the weighting coefficients required by differential quadrature approximation without restricting the choice of mesh grids. Applying this concept to the governing differential equation of circular plate gives a set of linear simultaneous equations. Bending moments, stresses values in radial and tangential directions and vertical deflections are found for two different types of load. In the present study, the axisymmetric bending behavior is considered. Both the clamped and the simply supported edges are considered as boundary conditions. The obtained results are compared with existing solutions available from analytical and other numerical results such as finite elements and finite differences methods. A comparison between the HDQ results and the finite difference solutions for one example plate problem is also made. The method presented gives accurate results and is computationally efficient.

• 한국정밀공학회지
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• 제19권5호
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• pp.110-117
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• 2002

This paper proposes a optimization of the design variables of linear motor for the improvement of thrust. Especially, this paper treats the shoe, which can be good to flow of a magnetic flux in linear motor. Firstly, this paper uses a space harmonic analysis method(SHAM) based on Fourier series, for analyzing the characteristics of core type linear motor, including slot structure and shoe. And compare the magnetic flux densities of linear motor at air gap with the results of the SHAM and the Finite Element Method(FEM). Secondly, this paper uses a genetic algorithm, which is good to find the global solutions. The design variables are the pole pitch of magnet, the pitch of slot, the height of slot, the width of shoe and the width of magnet. The maximum thrust with optimum design variables is about 247 N which is improved about 16%.

• Journal of Power Electronics
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• 제14권1호
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• pp.92-104
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• 2014

To insure stable operation and eliminate twice torque ripple, a topology for a six phase permanent magnet synchronous generator (SP-PMSG) with a neutral point connected together was analyzed in this paper. By adopting an extended transformation matrix, the mathematic model of the space vector control was established. The voltage and torque equations were deduced while considering the third harmonic flux and inductance. In addition, the suppression third harmonic method and the closed loop control strategy were proposed. A comparison analysis indicates that the cooper loss minimum method and the current magnitude minimum method can meet different application requirements. The voltage compensation amount for each of the methods was deduced which also takes into account the third harmonic effect. A simulation and experimental result comparison validates the consistency through theoretical derivation. It can be seen that all of the two control strategies can meet the requirements of post-fault.

• 대한전기학회:학술대회논문집
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• 대한전기학회 2003년도 하계학술대회 논문집 B
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• pp.849-851
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• 2003

This paper is deal with the method of design for optimum thrust model using genetic algorithms in slotless Permanent Magnet Linear Synchrous Motor (PMLSM). Characteristic analysis method is used 3D space harmonic analysis method. Design parameters are PM width and coil width.

• Journal of Electrical Engineering and Technology
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• 제1권3호
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• pp.327-331
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• 2006

This paper presents the analysis method for the torque characteristic of the 1-phase induction motor considering space harmonics in the air gap. The equivalent circuit method is used, where the circuit constants are obtained by classic theory. In addition, the space harmonic components in air gap magneto motive force are analyzed and added to the equivalent circuit to obtain accurate torque characteristics in low speed regions. Each torque component due to the harmonics is calculated and the total torque characteristic is obtained and compared with the measurement result.

• Fibers and Polymers
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• 제7권2호
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• pp.191-194
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• 2006

This paper adopts nonlinear vibration method to analyze the fluctuation process of fiber movement. Based on Hamilton Principle, this paper establishes differential equation of fiber axial direction movement. Using variable-separating method, this paper separates time variable from space variable. By using the disperse movement equation of Galerkin method, this paper also discusses stable region of transition curve and points out those influencing factor and variation trend of fiber vibration.

• 한국정보기술학회논문지
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• 제16권11호
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• pp.97-103
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• 2018

본 논문에서는 시변 최적 FIR 필터를 이용한 전력 신호의 고조파 검출 방법을 제안한다. 잡음이 고려된 전력 신호에 대해 고조파의 진폭과 위상각의 변화량이 확률적 정보로 고려된 시변 상태 방정식 모델에 대해 시변 최적 FIR 필터를 설계하여 고조파 성분을 검출한다. 제안한 검출 방법에 사용된 시변 FIR 필터는 유한 구간의 정보만을 사용하고 어떠한 초기 조건도 사용하지 않도록 설계되어 칼만 필터 기반의 검출 방법의 오차 누적에 따른 검출 성능 저하나 발산 문제를 해결할 수 있다. 또한 FIR 구조의 필터 사용을 통해 칼만 필터 대비 불확실성에 대해 보다 강인한 검출이 가능하다. 시변 최적 FIR 필터의 사용을 통해 시불변 최적 FIR 필터 기반 고조파 검출 방법 대비 보다 일반적인 해를 제공한다. 제안하는 검출 방법의 우수성을 검증하기 위해 시변 칼만 필터 및 적응 칼만 필터 기반 고조파 검출 방법과의 비교 시뮬레이션을 수행한다.

• Structural Engineering and Mechanics
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• 제29권6호
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• pp.659-671
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• 2008

A procedure to analyse the space frame structure fixed at base as well as resting on sliding bearing using total or absolute displacement in dynamic equation is developed. In the present method, the effect of ground acceleration is not considered as equivalent force. Instead, the ground acceleration is considered as a known value in the acceleration vector at degree of freedom corresponding to base of the structure when the structure is in non-sliding phase. When the structure is in sliding phase, only a force equal to the maximum frictional resistance is applied at base. Also, in this method, the stiffness matrix, mass matrix and the damping matrix will not change when the structure enters from one phase to another. The results obtained from the present method using absolute displacement approach are compared with the results obtained from the analysis of structure using relative displacement approach. The applicability of the analysis is also demonstrated to obtain the response of the structure resting on sliding bearing with restoring force device.