• Proceedings of the Korean Society of Precision Engineering Conference
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• 2005.06a
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• pp.284-288
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• 2005

This paper proposes the direct detection method of phase angle for the power source, which is based on the PLL method. The proposed method using a bidirectional photo-coupler is used to directly detect the zero crossing of phase voltage and calculate the angular frequency in the controller based on a M/T algorithm. Through the method, the additional installation space in the traditional method using a potential transformer can be minimized and it can be easy to design. The paper presents straightforward schematic circuits, design and experimental results.

• Proceedings of the KIEE Conference
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• 1999.07f
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• pp.2478-2480
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• 1999

In this paper, the authors propose a current control system for three phase PWM AC/DC converter without the source voltage sensors. The sinusoidal input current and unity effective power factor are realised based on the estimated source voltage in the controller. The estimation of source voltage is performed based on Luenberger observer using actual currents. The estimated source voltage is used to accomplish unity power factor. The proposed method is proved by simulations.

• Proceedings of the KIEE Conference
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• 1993.11a
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• pp.121-125
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• 1993

This paper proposes two kinds of novel switching method for a single phase current-controlled voltage-type ac-to-dc converter. Proposed are modifications of the conventional hysteresis current control, and are named by the half suppressing method and unipolar method, respectively. The first one suppresses an inactive half of the four switching signals and uses active another half for current control. The second method uses only one, a quarter of switching signals suppresed the others. Both the simulation and experimental results show that proposed methods are more efficient in switch utilization and have comparable or better performance when compared with conventional method.

• Proceedings of the KSR Conference
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• 2000.11a
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• pp.727-732
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• 2000

This paper is on the development of a auxiliary power supply for the coach of Indian Railways. The auxiliary power supply system supplies the power for air-conditioners, air-compressors, lighting equipments, controllers, etc. It converts the input voltage, DC 110V which is supplied from battery, to AC 3${\Phi}$ 415V of 30kVA capacity. This is a low voltage-high current type converter system and largely consists of boost chopper and 3 phase inverter. Adopting a optimal control algorithm and simple power circuit, we realized the more reliable and competitive system for satisfaction of Indian Railway's strict requirement for vibration, temperature and dust. We completed the design, the manufacture and the field test of the system successfully and proved the system performance and reliability as a result of those tests.

• Proceedings of the KIEE Conference
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• 1997.11a
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• pp.426-428
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• 1997

This paper presents the linearized optimal PWM techniques for current source GTO converter. This proposed method is to linearize an optimal PWM modulation strategy so that the turn-on/off-periods of the GTO switches can be computed on-line in real-time for any modulation index. This allows the rapid and continuous regulation of the DC output current while producing the sinusoidal AC input current waveform and unit power factor.

• Journal of Power Electronics
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• v.12 no.2
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• pp.357-362
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• 2012

In this paper, a power electronic converter which is composed of two converters - bidirectional AC/DC converter and Series Active Power Filter (SAPF), is discussed. Structural schemas and ways of operation of control systems of converters, which are used to eliminate non sinusoidal parts of the network source voltage, are presented. At the same time, the control used stabilizes the value of the voltage feeding the load. Taking in consideration the combined functions which the device executes, it may be called Unified Voltage Conditioner - UVC.

• Proceedings of the KIPE Conference
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• 2013.07a
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• pp.399-400
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• 2013

본 논문에서는 수중음향 센서를 위한 전력증폭기용 전원회로로 멀티레벨 가변전압출력 AC-DC 컨버터의 제어 알고리즘을 제안한다. 제안하는 제어 알고리즘은 최종 출력으로 5-레벨 가변전압을 얻기 위한 2대의 Flying capacitor 3-level converter의 전력 균등분담 제어를 위해 사용되며, 플라잉 커패시터의 전압 밸런싱 제어를 위해 사용된다. 본 논문에서 제안하는 제어 알고리즘은 수중음향 센서를 위한 전력증폭기용 전원회로에서 유용하게 사용될 것으로 예상한다.

• Journal of Electrical Engineering and Technology
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• v.13 no.1
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• pp.345-351
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• 2018

This paper analyzes a resonant inverter to generate plasma. The resonant inverter consists of a full bridge converter, resonant network and reactor to generate a magnetic field for plasma generation. A plasma load has very distinct characteristics compared to conventional loads. The characteristics of plasma load are analyzed through experimental results. This paper presents the study on the resonant network, which was performed in order to determine how to achieve a constant current gain. Another important contribution of this study is the analysis of drop-out phenomenon observed in plasma loads which is responsible for unpredictable shutdown of the plasma generator that requires stable operation. In addition, the design process for the resonant network of a plasma generator is proposed. The validity of this study is verified through simulations and experimental results.

• Proceedings of the KIPE Conference
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• 2014.07a
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• pp.83-84
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• 2014

This paper proposes the development of double conversion Uninterruptible Power Supply using 3-Level Converter/TNPC Inverter. The Rectifier of proposed system is operating not only 3-Level boost PFC but also battery discharger. The Inverter is converting DC voltage to AC voltage. And in terms of the efficiency, 3-Level TNPC inverter is improved compared to the origin 2-Level type. To verify the validity of proposed system, experiments were carried out.

• Proceedings of the KIPE Conference
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• 2012.07a
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• pp.232-233
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• 2012

This paper presents an effective control scheme for an electric vehicle battery charger where a symmetrical bridgeless power factor-corrected converter and a buck converter are cascaded. Both converters have been popular in industries because of their high efficiency, low cost, and compact size, hence combining these converters makes the overall battery charging system strongly efficient. Moreover, this charger topology can operate at universal input voltage and attain a desired battery current and voltage without ripple. In order to achieve a unity input power factor and zero input current harmonic distortion, the proposed control scheme adopts duty ratio feed-forward control technique in both current and voltage control loop. Additionally, in the current loop, its reference is created by a phase-locked loop (PLL) block, leading to a pure sinusoidal input current although the input voltage waveform is being distorted. The feasibility and practical value of the proposed approach are verified by simulation and experiment with an 110V/60Hz ac line input and 1.5kW-72V dc output of the battery charging system.