• 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.

• The Transactions of the Korean Institute of Electrical Engineers B
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• v.50 no.5
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• pp.214-220
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• 2001

This paper presents the design schemes for the improvement of force characteristics in a controlled permanent magnet liner synchronous motor (Controlled-PM LSM). The dependence of motor performance on the various design schemes, such as the slot shapes, the magnetization patterns of permanent magnet and the skewing, has been investigated in detail by using finite element method (FEM). The analysis results are verified by the experiment that is performed by a testing machine. From this study, it is known that the skewing of the magnet is the most efficient method in the aspects of detent force reduction and higher force density.

• Proceedings of the KIEE Conference
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• 1999.11b
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• pp.73-75
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• 1999

The performance of a SRM in terms of torque and power factor depends on the two-axis inductances (Ld and Lq) and iron loss of the machine. Finite element method has been used to determine these parameters for a motor with segmented rotor structure. Fock and Hart Method has been conducted to compare to verify the accuracy of proposed analysis method.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2014.10a
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• pp.84-89
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• 2014

Data-driven method for fault diagnostics system often use machine learning technique. To use such technique proper signal processing should be implemented such as time synchronous averaging (TSA) for ball bearing systems. However, for journal bearing diagnostics systems not much has been researched, and yet a proper signal processing method has not been studied. Therefore, in this research an optimal datum unit for a reliable journal bearing diagnostics system along with angular resampling process is being suggested. Before extracting time and frequency domain features, angular resampling is applied to each cycle of vibration data. As to preserve the characteristics of vibration signal, averaging method is replaced by finding the optimal datum unit which strengthens statistical characteristics of vibration signal. Then 20 features were extracted for various cases, and those features are being evaluated by two criteria, separability and classification accuracy.

• Progress in Superconductivity and Cryogenics
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• v.14 no.3
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• pp.5-8
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• 2012

Superconducting windings of synchronous machine have to be operated in below the critical temperature, critical current density and critical magnetic field. If one of these characteristics does not satisfied, then the quench occurred in superconducting winding. Especially the armature current dramatically increased as the superconducting generator is short-circuited at the rated load condition and magnetic field in field winding increased due to the armature current. Therefore, damper is required to reduce the magnetic field of field winding which increases reliability of the superconducting generator. Damper dimension can be decided by time constant[1-2]. In this paper the basic model is high-power and low-speed superconducting generator. Damper time constant was calculated from the changed damper thickness and material. Magnetic flux of field coil at the basic model and changed damper time constant model is analyzed.

• The Transactions of the Korean Institute of Electrical Engineers B
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• v.52 no.7
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• pp.299-306
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• 2003

Doubly-Fed Induction Generator(DFIG) is adequate to maximize the energy capture from wind energy, whereby the turbine speed can be adjusted to a speed, at which a rated tip speed ratio be kept. In this paper, a power analysis for DFIG and its characteristics of power flow in grid-connected operation, are dealt with in speed range of super- and sub-synchronous region. In a test of the machine, whereby a doubly excited circuit configuration in stator as well as rotor with back to back PWM inverter have been equipped, a constant input torque is given and in that condition, power new in stator and rotor circuit have been measured and compared with theoretical value. Furthermore, the power factor in stator and rotor circuit have been examined.

• Proceedings of the KIEE Conference
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• 2001.04a
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• pp.271-273
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• 2001

This paper presents a adaptive speed controller for field oriented controlled (FOC) permanent magnet synchronous motor (PMSM) drives. However, achieving FOC requires machine specific knowledge, and tracking of drifting motor parameters in order to maintain control. The proposed controller based on Minimum Controller Syntheses (MCS) algorithm does not require exact knowledge of motor parameters. This controller structure simplifies the design and implementation of the adaptive controller requiring less effort to synthesis than a standard MRAC system. Simulation results using Matlab/Simulink show that the proposed controller has good dynamic performances and it is insensitive to parameter variations.

• Proceedings of the KIEE Conference
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• 2001.07a
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• pp.149-151
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• 2001

This paper proposes the design of STATCOM(static synchronous compensator) stabilizer for improving power system stability using fuzzy logic controller(FLC). The STATCOM DC voltage regulator contributes negative damping to the power system as the installation of STATCOM DC voltage regulator. STATCOM stabiliser is superimposed on the AC voltage regulator to compensate the negative damping effect. To evaluate usefulness of the proposed method, we perform the nonlinear simulation on a single-machine infinite bus system. As results of the simulations, the proposed method shows better control performance than PI controller in terms of damping effects.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2003.08a
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• pp.55-58
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• 2003

IPMSM (Interior Permanent Magnet Synchronous Motor) is widely used in many applications such as an electric vehicle, compressor drives of air conditioner and machine tool spindle drives. In order to maximize the efficiency in such applications, this paper is proposed the optimal control method of the armature current. The controllable electrical loss which consists of the copper loss and the iron loss can be minimized by the optimal control of the armature current. The minimization of loss is possible to realize efficiency optimization control for the proposed IPMSM The proposed control algorithm is applied to IPMSM drive system, the operating characteristics controlled by efficiency optimization control are examined in detail by simulation.

• Proceedings of the KIEE Conference
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• 2006.07b
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• pp.625-626
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• 2006

This paper presents the new simulation model for the performance analysis of Surface-Mounted Permanent Magnet Synchronous Motor(SMPMSM) Drive System which is integrated with a controller and a power converter. To enhance reusability and compatibility, the system model is expressed by the association of independent sub-modules reflecting the real physical construction. This concept allows another independent sub-module to be effectively inserted in the model for the comprehensive analysis of larger systems such as a Machine Tool and HEV. The developed model which is composed of MATLAB/Simulink's basic blocks can rapidly analyze not only the entire behavior of system, but also the functional relationship between each components for the effective development of controller.