• Proceedings of the KIEE Conference
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• 1997.07d
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• pp.1317-1319
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• 1997

This paper is to study and develope a measurement apparatus for ferroelectricity. The apparatus consists of wave generation part, high voltage amplifier part, measurement part, data acquisition part and the related controll circuits. Single or double excitation wave is digitalized and sent to the external RAM of wave generation part by personal computer. These datas saved in the RAM are converted to analog excitation wave through D/A converter. The frequency of excitation wave is depend on the read-out speed of the RAM by clock pulse. Such generated wave is applied to high voltage amplifier as a input voltage. The output of high voltage amplifier is applied to ferroelectrics and the response is obtained from the charge amplifier of measurement part. The response is sampled and converted to digital datas through AID converter. These digital datas are automatically saved in the external RAM of acquisition part. The computer takes the digital datas and calculates the electric displacement D, the electric field and the dielectric constant $\varepsilon$. We tested for PZT ceramic sample and could observed the D-E hysteresis lops and ${\varepsilon}_s$-E hysteresis loops with good forms.

• Proceedings of the KIPE Conference
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• 2000.07a
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• pp.560-563
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• 2000

In this paper we proposed AC/DC boost converter to improve input current harmonic reduction in TIG welder. The proposed harmonic reduction circuit with UC2854AN acting on constant switching frequency average current control has a three-loop control structure : the inner current loop the line voltage feed-forward loop and th outer voltage loop. Also we applied the constant current strategy on full bridge IGBT inverter to stabilized the output current using the analog PI controller. To demonstrate the practical significance of the proposed methods some simulation studies and experimental results are presented.

• Journal of the Korean Society for Precision Engineering
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• v.23 no.6 s.183
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• pp.64-71
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• 2006

A target of this paper is to study on the usefulness of the adaptive piezoelectric energy harvesting device as a wireless electrical power supply when it is driven by mechanical vibrations of low frequency. For this purpose, an adaptive control technique and a step-down converter are used. A THUNDER series a piezoelectric material (TH7-R), which has been developed by a NASA engineer is selected for this study. In order to provide a mechanical energy to the piezoelectric material, a mechanical motion vibrator is designed. The adaptive controller is implemented using a dSPACE DS1104 controller board. The do-dc converter with an adaptive control technique harvests energy at over five times the rate of direct charging without a converter.

• KIEE International Transactions on Electrophysics and Applications
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• v.4C no.3
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• pp.96-100
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• 2004

The Nd： YAG laser is commonly used throughout many fields such as accurate material processing, IC marking, semiconductor annealing, medical operation devices, etc., due to the fact that it has good thermal and mechanical properties and is easy to maintain. In materials processing, it is essential to vary the laser power density for specific materials. The laser power density can be mainly controlled by the current pulse width and pulse repetition rate. It is important to control the laser energy in those fields using a pulsed laser. In this paper we propose the constant-frequency current resonant half-bridge converter and monitoring of capacitor charging voltage. This laser power supply is designed and fabricated to have less switching loss, compact size, isolation with primary and secondary transformers, and detection of capacitor charging voltage. Also, the output stabilization characteristics of this Nd： YAG laser system are investigated. The test results are described as a function of laser output energy and flashlamp arc discharging constant. At the energy storage capacitor charges constant voltage, the laser output power is 2.3％ error range in 600[V].

• Proceedings of the KIPE Conference
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• 2017.11a
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• pp.7-8
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• 2017

The Phase-Locked Loop (PLL) is widely used in grid-tie inverter applications to achieve the synchronization between the inverter and the grid. However, its performance is deteriorated when the grid voltage is not pure sinusoidal due to the harmonics and the frequency deviation. Therefore it is important to design a high performance phase-locked loop (PLL) for the single phase inverter applications to guarantee the quality of the inverter output. In this paper a simple method to improve the performance of the PLL for the single phase inverter is proposed. The proposed PLL is able to accurately estimate the fundamental frequency component of the grid voltage even in the presence of harmonic components. In additional its transient response is fast enough to track a change in grid voltage within two cycles of the fundamental frequency. The effectiveness of the proposed PLL is confirmed through the PSIM simulation and experiments.

• The Transactions of the Korean Institute of Power Electronics
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• v.12 no.2
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• pp.183-190
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• 2007

In this paper, a robust controller for PWM converter is proposed. The proposde converter controller consists of a PI controller for DC output voltage and a current controller using error-space approach for maintaining the sinusoidal current waveform and unity power factor. Conventionally, the try and error method has been used to design the current controller considering the switching frequency of the devices and sampling frequency of the digital controller. But this proposed method is based on characteristic ratio assignment(CRA) method which has the advantage to design the optimal gain to meet the referenced response and overshoot within the limit range. First, the CRA based current controller algorithm is explained. Then the validity of proposed controller is verified through the PSiM simulation and experience results.

• The Transactions of The Korean Institute of Electrical Engineers
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• v.62 no.11
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• pp.1628-1632
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• 2013

HEP(Head Electric Power) system, supplying 3-phase service power to the coach vehicles, is a kind of special auxiliary power equipment which is boarded on 8200 series electric locomotives in KORAIL. This equipment shares high voltage DC link with a main propulsion converter/inverter systems. It was difficult to use high frequency PWM technique so that GTO has been used as a power device same like the main power system. Due to low PWM frequency(300Hz) of HEP inverter, the output voltage has less power quality comparing to normal SIV(Static Inverter) system. In this paper, an optimal PWM strategy is presented for new IGBT type HEP inverter system. Several PWM techniques were investigated to improve output voltage quality under fixed lower filter inductance and not high PWM frequency. Finally PC simulations have been done to clarify its availability.

• The Transactions of the Korean Institute of Power Electronics
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• v.7 no.6
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• pp.563-569
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• 2002

This paper proposes an inverter for the grid-connected photovoltaic system based on the transformer-less inverter. This system consists of a high frequency DC-DC converter, high frequency transformer, diode bridge rectifiers, a DC filter, a low frequency inverter, and an AC filter. The 20kHz switched high frequency converter is used to generate bipolar PWM pulse, and the high frequency transformer transforms its voltage twice, which is subsequently rectified by diode bridge rectifiers for a full-wave rectified 60 Hz sine wave power output. Even though the high frequency link system needs more power semiconductors, a reduced size, light weight, and saved parts cost make this system more comparative than other power conditioning systems due to elimination of 60Hz transformer.

• Journal of Power Electronics
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• v.15 no.3
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• pp.577-586
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• 2015

The combination of voltage feedforward and feedback control is a conventional approach for correcting the power factor in single-phase ac-dc boost converters. The feedback duty ratio increases significantly with an increase of the line frequency and input inductance. Therefore, the performance of the conventional approach is highly dependent on the bandwidth of the feedback controller. As a result, the input power quality can be significantly exacerbated due to uncompensated duty ratios if the feedback controller is limited. This paper proposes an input impedance and current feedforward control method to reduce the control portion of the feedback controller. The findings in this paper are 1) the theoretical derivation and analysis of variations of line frequency and input inductance on a power factor correction approach, 2) guaranteed consistent performance in a wide range of conditions, and 3) that a low switching frequency can be utilized by the proposed method. A MATLAB/Simulink model and a 1.2kW dual boost converter are built to demonstrate the effectiveness of the proposed method.

• Proceedings of the Korean Institute of Intelligent Systems Conference
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• 2006.05a
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• pp.257-260
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• 2006

카오스 로봇의 하드웨어 구현에서 로봇의 차제 또는 바퀴가 정확하기 자기 위치를 인식하고 지시한 방향과 거리만큼 이동하는 것이 가장 중요하다. 이를 위해 정확한 방향을 움직일 수 있는 각속도 센서는 로봇에서 매우 중요한 위치를 차지한다. 정확한 각속도 센서를 설계하기 위해서는 정확하게 전압을 주파수로 바꾸어주는 VF(Voltage to Frequence) 컨버터의 설계가 선행되어야 하며 이를 만족하는 것으로 선형성이 보장되어야 한다. 이에 본 논문에서는 VF 컨버터에서 선형성을 개선시키기 위한 방법을 제시하고 제시한 방법을 기초로 한 VF 컨버터를 설계하였다.