• Proceedings of the KIEE Conference
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• 2001.04a
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• pp.195-197
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• 2001

This paper presents the circuit modeling and Control methods of PWM DC/DC Converter with Isolated dual outputs. The dual output converter topology is consisted of the two switch and single secondary winding. The control algorithm which is used by an adjusted PI control methods, of Dual Output PWM DC/DC converter is proposed in this paper. The proposed adjusted PI control method has faster response characteristics than conventional PI control methods at load change. The validity of the proposed adjusted control method is verified with the several interesting simulation results.

• Proceedings of the KSR Conference
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• 1999.05a
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• pp.322-327
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• 1999

In most railway vehicle applications, a single phase AC/DC converter is used greatly and is essential equipment for Korea High Speed Train. A diode bridge rectifier and a phase-controlled thyristor bridge rectifier generate harmonics in power system. Nowadays, power factor and harmonics become major issue in electrical equipment for railway vehicle. Many researchers have been trying to improve the power factor and ac-side harmonics. Therefore the PWM converter is used to operate at unity Power factor and to reduce ac-side current harmonics. This paper describes the circuit for AC/DC PWM converter of Korea High Speed Train and proposes control algorithm to realize the sinusolidal input current waveform and the effective unity power factor. The validity of the proposed control method is verified through the experimental result.

• Proceedings of the KIPE Conference
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• 2013.07a
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• pp.26-27
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• 2013

본 논문에서는 3상 Z-소스 PWM 정류기의 DC-link단 과도응답 특성을 개선하기 위해 PI제어기를 사용한 대신에 제어 대상에 대한 정확한 수식이 없이도 제어기 설계가 가능한 퍼지 PI제어기를 이용하였다. 제안한 퍼지 PI-제어기 기반의 PWM 정류기는 교류측 전압과 전류 센서 없이 DC-link단 전압과 전류 센서만을 이용하여 교류측 전압과 전류를 추정하였으며, 이를 PSIM 시뮬레이션을 통하여 검증 하였다.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 1998.06a
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• pp.527-533
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• 1998

An optimized PWM switching strategy for an induction motor voltage control is developed and demonstrated. Space vector modulation in voltage source inverter offers improved DC-bus utilization and reduced commutation losses, and has been therefor recognizedas the perfered PWM method, especially in the case of digital implementation. Three-phase invertor voltage control by space vector modulation consists of switching between the two active and one zero voltage vector by using the proposed optimal PWM algorithm. The prefered switching sequence is defined as a function of the modulation index and period of a carrier wave. The sequence is selected by suing the inverter switching losses and the current ripple as the criteria. For low and medium power application, the experimental results indicate that good dynamic response and reduced harmonic distortion can be achieved by increasing switching frequency.

• Journal of Institute of Control, Robotics and Systems
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• v.8 no.2
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• pp.97-103
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• 2002

This paper deals with a PWM(Pulse Width Modulation) current amplifier using digital controller in order to generate a gradient magnetic field far the MRI(Magnetic Resonance Image) system. Because of tolerance of discrete devices, it is difficult to set accurate values of the control parameters and to make an analog-controlling circuit. However, using digital controller, it is possible to set exact control parameters and to adopt a modern control techniques. It is shown that the digital controller will highly enhance the output current response and it will improve the quality of the MRI.

• Korean Journal of Poultry Science
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• v.34 no.1
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• pp.31-36
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• 2007

This experiment was conducted to determine the effect of betaine on immune response in laying hens. A total of 72 ISA-brown laying hens were divided into four groups of 18 hens each and fed corn-soybean meal based diets with addition of 0, 300, 600 and 1,200 ppm betaine for four weeks. The effect of betaine on splenocyte proliferations with mitogens, concanavalin A(Con A) and pokeweed mitogen(PWM), were assayed after incubation using [3H] thymidine uptake. Proliferations of splenocyte were significantly increased by activation of mitogen Con A or PWM. Mitogen effects of Con A were increased by Con A plus betaine injection(0.1 mM), whereas PWM effects did not affect in PWM plus betaine injection(0.1 mM) in vitro. Splenocyte of laying hens fed betaine tended to proliferate in the presence of PWM, but appeared to be slightly suppressed in the presence of Con A in vivo. Proliferation of splenocytes which were stimulated by Con A or Con A+betaine injection(0.1 mM) were increased in dietary 600 ppm betaine, but inhibited in dietary 1,200 ppm betaine supplementation. Spleen weights and sheep red blood cell(SRBC) titers of hens fed betaine tended to increase compared to those of control, but were not significantly different. These results suggested that betaine could increase splenocyte proliferation in vitro.

• Journal of Power Electronics
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• v.3 no.2
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• pp.99-114
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• 2003

This paper presents a feasible development on a highly accurate quick response adjustable speed drive implementation fur general purpose induction motor which operates on the basis of sensorless slip frequency type vector controlled sine-wave PWM inverter with an automatic tuning machine parameter estimation schemes. In the first place, the sensorless vector control theory on the three-phase voltage source-fed inverter induction motor drive system is developed in slip frequency based vector control principle. In particular, the essential procedure and considerations to measure and estimate the exact stator and rotor circuit parameters of general purpose induction motor are discussed under its operating conditions. The speed regulation characteristics of induction motor operated by the three-phase voltage-fed type current controlled PWM inverter using IGBT's is illustrated and evaluated fur machine parameter variations under the actual conditions of low frequency and high frequency operations for the load torque. In the second place, the variable speed induction motor drive system, employing sensorless vector control scheme which is based on three -phase high frequency carrier PWM inverter with automatic toning estimation schemes of the temperature -dependent and -independent machine circuit parameters, is practically implemented using DSP-based controller. Finally, the dynamic speed response performances for largely changed load torque disturbances as well as steady state speed vs. torque characteristics of this induction motor control implementation are illustrated and discussed from an experimental point of view.

• The Transactions of The Korean Institute of Electrical Engineers
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• v.62 no.3
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• pp.355-364
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• 2013

Respect to the input AC voltage and output DC voltage, conventional three-phase PWM rectifier is classified as the voltage type rectifier with boost capability and the current type rectifier voltage with buck capability. Conventional PWM rectifier can not at the same time the boost and buck capability and its bridge is weak in the shoot- through state. These problems can be solved by Z-source PWM rectifier which has all characteristic of voltage and current type PWM rectifier. By shoot-through duty ratio control, the Z-source PWM rectifier can buck and boost at the same time, also, there is no need to consider the dead time. This paper proposes the input AC voltage sensorless control method of a three-phase Z-source PWM rectifier in order to accomplish the unity input power factor and output DC voltage control. The proposed method is estimated the input AC voltage by using input AC current and output DC voltage, hence, the sensor for the input AC voltage detection is no needed. comparison of the estimated and detected input AC voltage, estimated phase angle of the input voltage, the output DC voltage response for reference value, unity power factor, FFT(Fast Fourier Transform) of the estimated voltage and efficiency are verified by PSIM simulation.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.5 no.6
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• pp.1116-1121
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• 2001

Phase shifter has been used as a means of power-flow control and for transient stability improvement in AC transmission system. Until now, phase shifters have been based on an injection transformer. Conventional phase shifters with tap changers require regular maintenance and allow only step-like control of the phase angle. This paper propose a three-phase phase shifter using PWM AC/AC converter, which can improve system response and control stability in the applications. This paper deals with the circuit topology, operating principle so that the features of the phase shifter will be shown through computer simulation, especially using PSIM software.

• The Transactions of the Korean Institute of Power Electronics
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• v.13 no.1
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• pp.55-62
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• 2008

This paper proposes a feedback linearization control scheme of AC/DC PWM converters with LCL input filters using no damping resisters. This feedback linearization scheme can eliminate the non-linearity of the system. So, the controller of the system can be designed by using linear control theory, which gives a good transient response. The cascade structure of the controller makes the converter current be controlled within a certain limit. To reduce the number of sensors, the source voltage and current is estimated. The validity of the proposed control algorithm is verified by simulation and experimental results.