• Journal of Electrical Engineering and Technology
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• v.8 no.5
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• pp.1002-1011
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• 2013

This paper proposes the new adaptive protection algorithm for inverse-time overcurrent relays (OCRs) to ensure their proper operating time and protective coordination. The application of the proposed algorithm requires digital protection relays with microcontroller and memory. The operating parameters of digital OCRs are adjusted based on the available data whenever system conditions (system with distributed generation (DG)) vary. Moreover, it can reduce the calculation time required to determine the operating parameters for achieving its purpose. To verify its effectiveness, several case studies are performed in time-domain simulation. The results show that the proposed adaptive protection algorithm can keep the proper operating time and provide the protective coordination time interval with fast response.

• Journal of international Conference on Electrical Machines and Systems
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• v.2 no.1
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• pp.16-22
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• 2013

This paper presents the analysis and optimization of air-core permanent magnet linear synchronous motor with overlapping concentrated windings to achieve high thrust density, high thrust per copper losses and low thrust ripple. For the motor design, we adopt equivalent magnetizing current (EMC) method to analyze the magnetic field and give analytical formulae for calculation of motor parameters such as no-load back EMF, dynamic force, thrust density and thrust per copper losses. Further, we proposed a multi-objective optimization by genetic algorithm to search for the optimum parameters. The design optimization is verified by 2-D Finite Element analysis (FEA).

• 제어로봇시스템학회:학술대회논문집
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• 1999.10a
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• pp.125-128
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• 1999

A linear time-invariant model can be described either by a parametric model or by a nonparametric model. Nonparametric models, for which a priori information is not necessary, are basically the response of the dynamic system such as impulse response model and frequency models. Parametric models, such as transfer function models, can be easily described by a small number of parameters. In this paper aiming to take benefit from both types of models, we will use linear-combination of basis fuctions in an impulse response using a few parameters. We will expand and generalize the Kautz functions as basis functions for dynamical system representations and we will consider estimation problem of transfer functions using Kautz function. And so we will present the influences of poles settings of Kautz function on the identification accuracy.

• Journal of Electrical Engineering and Technology
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• v.5 no.3
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• pp.415-422
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• 2010

The distributed flexible alternative current transmission system (D-FACTS) is a recently developed FACTS technology. Distributed Static Series Compensator (DSSC) is one example of DFACTS devices. DSSC functions in the same way as a Static Synchronous Series Compensator (SSSC), but is smaller in size, lower in price, and possesses more capabilities. Likewise, DSSC lies in transmission lines in a distributed manner. In this work, we designed a fuzzy logic controller to use the DSSC for enhancing transient stability in a two-machine, two-area power system. The parameters of the fuzzy logic controller are varied widely by a suitable choice of membership function and parameters in the rule base. Simulation results demonstrate the effectiveness of the fuzzy controller for transient stability enhancement by DSSC.

• Proceedings of the KIEE Conference
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• 2002.04a
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• pp.190-197
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• 2002

The goal of this paper is to propose a virtual instrumentation system based on three dimensional current coordinates for monitoring power quality. A developed system with various experimental graphic screens and numerical results is made up 586-PC and DSP(digital signal processor) board, power quality analyzing and evaluating software for windows. Power parameters are analyzed using correlation signal processing techniques based on the correlation between voltage and current waveforms. Analysis results are visualized by 3-D current coordinates, and it is compared and evaluated with conventional time/frequency domain. To verify the validity of the proposed system, power and harmonic parameters of single phase induction motor drive system is analyzed and verified.

• Journal of Electrical Engineering and information Science
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• v.2 no.3
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• pp.113-122
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• 1997

An adaptive input-output linearization technique for a robust speed control of a brushless C(BLDC) motor is presented. By using this technique, the nonlinear moro model can be effectively linearized in Brunovski canonical form, an the desired speed dynamics can be obtained based on the linearized model. This control technique, however, gives an undesirable output performance under the mismatch of the system parameters and load conditions caused by the incomplete linearization. for the robust output response, the controller parameters will be estimated by a model reference adaptive technique where the disturbance torque and flux linkage are estimated. The adaptation laws are derived by the Popov's hyperstability theory nd positivity concept. The proposed control scheme is implemented on a BLDC motor using the software of DSP TMS320C30 and the effectiveness is verified through the comparative simualtions and experiments.

• Proceedings of the KIEE Conference
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• 1994.07b
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• pp.1442-1444
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• 1994

The short channel poly-Si TFT is important in aspect of transistor characteristics, packing density and aperture ratio. In this paper, we have reported the degradation phenomena of short channel poly-Si TFT's which had significantly degraded device parameters, such as threshold voltage shift and a great asymmetric degradation, due to gate and drain electrical stress. The reduced effective channel length and expanded depletion region may be the main reason of these significant device parameters.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.19 no.5
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• pp.477-479
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• 2006

Carbon films was grown on Si substrates using the method of electrolysis for methanol liquid. Deposition parameters for the growth of the carbon films were current density for the electrolysis, methanol liquid temperature and electrode spacing between anode and cathode. We examined electrical resistance and the surface morphology of carbon films formed under various conditions specified by deposition parameters. It was clarified that the high electrical resistance carbon films with smooth surface morphology are grown when a distance between the electrodes was relatively wider. We found that the electrical resistance in the films was independent of both current density and methanol liquid temperature for electrolysis. The temperature dependence of the electrical resistance in the low resistance carbon films was different from one obtained in graphite.

• Proceedings of the KIEE Conference
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• 2000.07b
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• pp.708-710
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• 2000

The interaction of electromagnetic forces and mechanical structure of switched reluctance motors(SRM) is the major cause of the noise and vibration. The stator part in SRM produces the most vibrations. Therefore, it is necessary to know the natural frequencies of the stator. In this paper, the variation of natural frequencies according to the design parameters is investigated to avoid the resonance. The natural frequency of the tested motor is founded by the frequency response function obtained by a experimental modal analysis.

• Journal of international Conference on Electrical Machines and Systems
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• v.2 no.3
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• pp.288-294
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• 2013

This paper introduces a novel method of on-line identifying the stator resistance and leakage inductance of dual three phase induction motor (DTPIM). According to the machine mathematical model, the stator resistance and leakage inductance can be estimated using the voltage and current values in harmonic subspace. Thus a method of voltage vector injection in harmonic subspace (VVIHS) is proposed, which causes currents in harmonic space. Then the errors between command and actual harmonic currents are utilized to regulate the machine parameters, including stator resistance and leakage inductance. The principle is presented and analyzed in detail. Experimental results prove the feasibility and validity of proposed method.