• Journal of Power Electronics
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• v.15 no.4
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• pp.1119-1130
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• 2015

This study investigates the multi-objective fuzzy optimization of crowbar resistance for the doubly fed induction generator (DFIG) low-voltage ride-through (LVRT). By integrating the crowbar resistance of the crowbar circuit as a decision variable, a multi-objective model for crowbar resistance value optimization has been established to minimize rotor overcurrent and to simultaneously reduce the DFIG reactive power absorbed from the grid during the process of LVRT. A multi-objective genetic algorithm (MOGA) is applied to solve this optimization problem. In the proposed GA, the value of the crowbar resistance is represented by floating-point numbers in the GA population. The MOGA emphasizes the non-dominated solutions and simultaneously maintains diversity in the non-dominated solutions. A fuzzy-set-theory-based is employed to obtain the best solution. The proposed approach has been evaluated on a 3 MW DFIG LVRT. Simulation results show the effectiveness of the proposed approach for solving the crowbar resistance multi-objective optimization problem in the DFIG LVRT.

• Proceedings of the KIEE Conference
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• 1996.07a
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• pp.12-14
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• 1996

In this paper, the simulation of the effects of variation of rotor resistance of induction motor for the performance of vector control is presented. Especially, this paper considered the effects as a difference variation of the rotor resistance between slip calculator and induction motor.

• Journal of Environmental Health Sciences
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• v.18 no.2
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• pp.117-124
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• 1992

Pretreatment with low concentration of Bleomycin and Cadmium rendered Chinese Hamster Ovary Cells more resistant to the induction of chromosome aberration by subsequent high concentration of same agent, however Mitomycin C did not function in that way. The cells pre-exposed to low dose of Cadmitim did not show cross-resistance to challenge dose of Mitomycin C for the induction of chromosome aberration, but cells pre-exposed to Bleomycin showed cross resistance. And the cells pre-exposed to low dose of Mitomycin C showed cross resistance to challenge of Bleomycin, but Cadmium did not.

• Proceedings of the KIEE Conference
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• 1996.07a
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• pp.267-269
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• 1996

Servo systems became indispensable to applications such as industrial robots and numerically controlled machinery. Especially, induction motor drives are widely used as ac-servo system owing to the fact that it is maintenance-free. At the present time, Quick torque control methods such as vector control have been employed that enables an induction motor to attain as quick torque response as a dc motor. However, these methods can not be realized without knowing several motor parameters accurately, because the methods need them to calculate flux or voltage command. Most of all, secondary resistance has to be identified accurately, because it's value varies greatly for operation of induction motors. In this paper, a new identification method of secondary resistance based on quick torque control system of induction motors is proposed. The proposed method is derived theoretically from motor circuit equation and can be realized very simply by detecting primary current and voltage command of the motor. Through the numerical simulation considered using PWM inverter, the validity of the proposed method was successfully confirmed.

• The Transactions of the Korean Institute of Electrical Engineers B
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• v.51 no.7
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• pp.331-338
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• 2002

An inverter-fed induction is driven by a harmonic voltage source so that it is necessary to be analysed by time-stepping F.E.M. But it takes so long time that disadvantageous to design. This paper presents a simple analysis method for inverter-fed induction motor using FEM and harmonic equivalent circuit. First, the rotor bar resistance and the leakage reactance are determinated by FEA for 1 slot region in rotor to consider the skin effect and the saturation. Secondly, the characteristic of the motor is analyzed by the harmonic equivalent circuits consisting of the obtained parameters from the FEA. This method is carried out to analyze an induction motor driven by the sinusoidal voltage and the inverter. The results are verified by comparing with those of the time-step F.E.A and the experiment.

• Proceedings of the KIEE Conference
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• 2001.07d
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• pp.2246-2248
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• 2001

This paper presents a new vector control scheme for induction motor. An exact knowledge of the rotor flux position is essential for a high-performance vector control. The position of the rotor flux is measured in the direct schemes and estimated in the indirect schemes. Since the estimation of the flux position requires a priori knowledge of the induction motor parameters, the indirect schemes are machine parameter dependent. The rotor and stator resistance among the parameters change with temperature. Variations in the parameters of induction machine cause deterioration of both the steady state and dynamic operation of the induction motor drive. Several methods have presented to minimize the consequences of parameter sensitivity in indirect scheme. In this paper, new estimation scheme of rotor flux position is presented to eliminate sensitivity due to variation in the resistance. The simulation is executed to verify the proposed vector control performance and to compare its performance with that of indirect and direct vector control.

• Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
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• v.13 no.4
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• pp.27-31
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• 1999

This paper covers starting characteristics and design of wound motor induction rmtor can used to double excited induction mootor. They are employing in many electrical equiprrent system of industrial field The stator is satre as that of conventional induction motor. But rotor was rewind with new style, as result both of starting torque and operating efficiency could be high, But starting current could be small. Could obtain the satre result as that of conventional induction rmtor with external resistance on the rotor. The structure could be simple, system cost could be low and the maintanence free, Because of no slip rings, no brushes and no external resistance.stance.

• Proceedings of the KIPE Conference
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• 1998.10a
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• pp.23-28
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• 1998

We propose a nonlinear feedback controller that can control the induction motors with high dynamic performance by means of decoupling of motor speed and rotor flux. The nonlinear feedback controller needs the information on some motor parameters. Among them, rotor resistance varies greatly with machine temperature. A new recursive adaptation algorithm for rotor resistance which can be applied to our nonlinear feedback controller is also presented in this paper. The recursive adaptation algorithm makes the estimated value of rotor resistance track its real value. Some simulation results show that the adaptation algorithm for rotor resistance is robust against the variation of stator resistance and mutual inductance. In addition, it is computationally simple and has small estimation errors. To demonstrate the practical significance of our results, we present some experimental results.

• The Transactions of the Korean Institute of Electrical Engineers B
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• v.53 no.9
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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.

• The Transactions of the Korean Institute of Power Electronics
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• v.23 no.1
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• pp.24-31
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• 2018

An induction heating (IH) resonant converter, as well as its coil design method, is proposed in this study to improve the heat capability of low- and high-resistance IH vessels. Conventional IH resonant converters have been designed only for heating high-resistance containers designed for IH application. Thus, the primary current in the resonant tank becomes extremely high to transfer the rated power when the converter heats the low-resistance vessel. As a result, the rated power cannot be transferred due to overcurrent flows against the rated switch current. Hence, the optimal number of coil turns and proper operating frequency to heat high- and low-resistance vessels are proposed in this study by analyzing an IH load model. Simulation and experimental results using a 2.4 kW prototype resonant converter and its IH coil validate the proposed design.