• The Proceedings of the Korean Institute of Illuminating and Electrical Installation Engineers
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• v.8 no.2
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• pp.69-76
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• 1994

An effective method for reducing the harmonics in double connected modified current source inverter[MCSI] by switching taps on auto transformer is presented in this paper. The proposed system operates as like a 24 step MCSI by adding only tap changing auxiliary circuit which consists of several taps and static switching elements to the 12 step multiple inverter, which is double connected three-phase six-step MCSI with an auto transformer. The basic theories of the proposed inverter systems for analyzing the output waveforms are described. And to optimize the effectiveness of the harmonic reduction, the optimum turn ratio and the tap changing control angle of auto transformer are decided by digital simulation and its validity is verified by experiment. Although the construction of the proposed inverter is very simple, it is clarified that the output waveform of the inverter is almost the same as that of the conventional 24 step multiple inverter under the optimum condition.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.24 no.1
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• pp.36-41
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• 2011

Medical X-ray has been brought many changes according to the rapid development of high technology. Especially, for high-voltage generator which is the most important in X-ray generation the traditional way is to use high-voltage electric transformers primarily. However, since it is large and heavy and the ripple rate of DC high-voltage applied to X-ray tube is too big, it has a disadvantage of low X-ray production efficiency. To solve these problems, the studies about high-voltage power supply are now proceeding. At present, the high-voltage generator that generates high-voltage by making high frequency using inverter control circuit consisting of semiconductor device is mainly used. High-voltage generator using inverter has advantages in the diagnosis using X-ray including high performance with short-term use, miniaturization of power supply and ripple reduction. In this study, the X-ray high-voltage device with inverter type using pulse width modulation scheme to the control of tube voltage and tube current was designed and produced. For performance evaluation of produced device, the control signal analysis, irradiation dose change and beam quality depending on the load variation of tube voltage and tube current were evaluated.

• The Transactions of the Korean Institute of Power Electronics
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• v.5 no.6
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• pp.620-631
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• 2000

A torque ripple reduction technique of direct torque control(DTC) for high power induction motors driven by 3-level inverters with the inverter switching frequency limited around 0.5-1.0kHz level is presented. It is noted that conventional DTC algorithms to reduce torque ripple are devised for applications with relatively high switching frequency above 2-3kHz. Such conventional algorithms can not accomplish satisfactory torque ripple reduction for 3-level inverter systems with lower switching frequency. A new DTC algorithm, especially for low switching frequency inverter system, illustrates relatively reduced torque ripple characteristics all over the operating speed region. Simulation and experimental results show the effectiveness of the proposed control algorithm.

• The Transactions of The Korean Institute of Electrical Engineers
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• v.56 no.6
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• pp.1064-1070
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• 2007

This paper presents a grid-interactive current controlled voltage source inverter (CCVSI) with uniterruptible power supply (UPS), which uses an inner current control loop (polarized ramp time (PRT)) and outer feedback control loops to improve grid power quality and UPS. To reduce the complexity, cost and number of power conversions, which results in higher efficiency, a single stage CCVSI is used. The operation of this system could be divided into the power quality control (PQC) state mode and the UPS state mode. In PQC mode, the system operated to compensate the reactive power demand by nonlinear load or variation in load. In UPS mode. the system is controlled to provide a sinusoidal voltage at the rated value for the load when the gird fail. To verify the proposed system, a comprehensive evaluation with theoretical analysis, simulation and experimental results for 1KVA load capacity is presented.

• The Transactions of the Korean Institute of Power Electronics
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• v.18 no.1
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• pp.10-17
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• 2013

In this paper, a new active damping method of LCL filter without capacitor voltage sensors is proposed for 3 phase PWM Inverter. Normally, L filter or LCL filter is used as an output filter of grid connected PWM inverter. An LCL filter has more excellent performance than L filter to reduce harmonic current, so the small inductance value can be used. However, the resonance problem in LCL filter is happen due to the zero impedance by the addition of LC branch. To solve the resonance problem, the various active damping method has been proposed so far. Generally, the virtual resistor active damping methods is required to additional hardware sensors for measurement of capacitor voltage and current. In this paper, the new active damping method is proposed without any capacitor voltage or current sensors. In the proposed method, the resonance component of the capacitor voltage of LCL filter can be observed by a simple MRAS(Model Reference Adaptive System) observer without additional hardware sensors, and this component is suppressed by feedforward compensation. The validity of the proposed method is proven by simulation and experiment on the 3-phase PWM inverter system.

• 제어로봇시스템학회:학술대회논문집
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• 2004.08a
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• pp.14-19
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• 2004

This paper presents two approaches for designing a digital controller of UPS inverter with time response requirements and a fixed sampling time, which are inward and outward approaches based on a double loop feedback structure. In both approaches, the emulation method. is occupied. Thus we first design continuous-time controllers and then obtain digital controllers by using discretization. We apply the characteristic ratio assignment (CRA) in order to achieve the time response specifications. Also, the internal model control has been used for compensating phase delay in outward approach. The performances of the proposed controller are evaluated through several simulations carried out with Simpower system toolbox 3.0 of $Simulink^{(R)}$.

• Proceedings of the KIEE Conference
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• 1992.07b
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• pp.1206-1210
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• 1992

To satisfy the requirements of a stable speed control, comfortable ride and precise landing in the high-speed elevator. The induction motor driving elevator is controlled by inverter using vector control method which calculates optimum torque to apply to the Induction motor. This paper describes the control system of high-speed elevator that consists of the voltage-type PWM converter with an unity input power factor and sinusoidal input current and the voltage-type PWM inverter with a precise speed control and sinusoidal output current. The test results of actual elevator are presented.

• Proceedings of the KIEE Conference
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• 1995.11a
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• pp.281-283
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• 1995

Deadbeat controlled PWM Inverter is realized. This PWM inverter performs the instantaneous control method which is based on the real-time digital feedback control and the microprocessor-based deadbeat control. For the deadbeat current controller, the system's order becomes a high order and increases computation delay time. Therefore, The delay tine produces current ripple. To minimize the current ripple, a new method based on deadbeat control theory for current regulation is proposed. It is constructed by a reduced-order state observer which predicts the output current in next sampling instant.

• Proceedings of the KIEE Conference
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• 1990.07a
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• pp.346-350
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• 1990

This paper proposes a novel current control strategy for current regulated VSI-PWM transistor inverter. The conventional hysteresis control method has good dynamic responses. But the switching frequencies are high because it does not optimize switching patterns. Proposed current control strategy can optimize switching patterns. As regulator, three level comparators are used. The outputs of the comparators select appropriate inverter output voltage vectors via switching table stored in EPROM. The simulation and exparimental results in comparison to contentional hysteresis strategy are presented and discussed.

• Proceedings of the KIEE Conference
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• 2005.10c
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• pp.223-225
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• 2005

This paper presents a novel prototype of a current source resonant inverter using insulated gate bipolar transistors for driving a streamer reactor, streamer generation technology has been recognized as one of the best methods for water treatment, disinfection, industrial wastes utilization, and so on. However, some technological difficulties related to efficient streamer production have been significant problems restricting streamer usage in the industrial plants. Introduced in this paper is a pulse density modulated high frequency inverter for a plasma generate, which is developed with the aim to improve power conversion and control characteristics of the streamer reactor by using advances in power electronic technology. The developed system implements the feedforward control-based pulse density modulation control scheme with pulse width modulation feedback control strategy to compensate temperature and other environmental influences on streamer discharge.