• Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
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• v.18 no.6
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• pp.230-237
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• 2004

In this paper the effects of inverter ripple currents to the Proton Exchange Membrane Fuel Cell Stack (PEMFCS) is analyzed by the impedance model. The proposed method employs the frequency analysis technique to derive an equivalent impedance model of the fuel cell stack and the effects of the inverter ripple current are investigated. The calculated results m then verified by means of experiments on commercially available PEMFCSs. The experimental results show that the ripple current can contribute up to 10[%] reduction in the available output power.

• Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
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• v.16 no.3
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• pp.110-115
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• 2002

This paper proposes the adaptive fuzzy control system using the microprocessesor for high precision control of automation systems which exist non-linearities such as saturation, relays, hysteresis, and dead zones. The proposed system which provides the improvement in terms of the control region in transient and adaptive control, first used the frequence-locked mothed driving a system to generate a output voltage proportional to the frequency diffierence of relnence input signal and feedback signal for fast transient response,, and when the error reaches the preset value, used the adaptive fuzzy logic for precision control. The theoretical and experimental studies have been carried out. The presented results from the above investigation show considerable improved performance in the precision control of servo control systems.

• Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
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• v.27 no.3
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• pp.1-6
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• 2013

In this study, we propose a fiber-optic hydrogen sensor using a polarization-diversity loop configuration composed of a polarization beam splitter, two quarter-wave plates, and a polarization-maintaining fiber coated with palladium whose thickness is ~400nm. One transmission dip of the output interference spectrum of the proposed sensor, chosen as a sensor indicator, was observed to spectrally shift with the increase of the hydrogen concentration, and the sensing indicator showed a wavelength shift of ~2.48nm at a hydrogen concentration of 4%. Except for a hydrogen concentration of 4%, the response time of the proposed sensor was measured as less than 12.5s and did not show significant dependence on the hydrogen concentration. In particular, the proposed fiber hydrogen sensor is more durable and highly resistant to external stress applied on a transverse axis of an optical fiber, compared with other hydrogen sensors based on side-polished fibers or fiber gratings.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.14 no.3
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• pp.991-996
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• 2013

In this paper, the ultrasonic horn having the natural frequency with 60 [kHz] for the dissimilar material bonding of the glass and solder tried to be designed. The ultrasonic horn was designed through the relational formula including the aspect ratio of the input terminal and output terminal, length of the ultrasonic horn. The modal analysis was performed for the propriety analysis of the designed horn. The parameters and response was set through the basic experiment. The dissimilar material bonding strength analysis using the ultrasonic transducer was done. The optimal process parameters having maximum bonding strength was derived.

• 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.

• Journal of Power Electronics
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• v.7 no.2
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• pp.159-173
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• 2007

In this paper, an intelligent sliding-mode position controller (ISMC) for achieving favorable decoupling control and high precision position tracking performance of permanent-magnet synchronous motor (PMSM) servo drives is proposed. The intelligent position controller consists of a sliding-mode position controller (SMC) in the position feed-back loop in addition to an on-line trained fuzzy-neural-network model-following controller (FNNMFC) in the feedforward loop. The intelligent position controller combines the merits of the SMC with robust characteristics and the FNNMFC with on-line learning ability for periodic command tracking of a PMSM servo drive. The theoretical analyses of the sliding-mode position controller are described with a second order switching surface (PID) which is insensitive to parameter uncertainties and external load disturbances. To realize high dynamic performance in disturbance rejection and tracking characteristics, an on-line trained FNNMFC is proposed. The connective weights and membership functions of the FNNMFC are trained on-line according to the model-following error between the outputs of the reference model and the PMSM servo drive system. The FNNMFC generates an adaptive control signal which is added to the SMC output to attain robust model-following characteristics under different operating conditions regardless of parameter uncertainties and load disturbances. A computer simulation is developed to demonstrate the effectiveness of the proposed intelligent sliding mode position controller. The results confirm that the proposed ISMC grants robust performance and precise response to the reference model regardless of load disturbances and PMSM parameter uncertainties.

• The Transactions of the Korean Institute of Power Electronics
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• v.17 no.5
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• pp.423-430
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• 2012

An adaptive maximum power point tracking (MPPT) scheme employing a variable scaling factor is presented. A MPPT control loop was constructed analytically and the magnitude variation in the MPPT loop gain according to the operating point of the PV array was identified due to the nonlinear characteristics of the PV array output. To make the crossover frequency of the MPPT loop gain consistent, the variable scaling factor was determined using an approximate curve-fitted polynomial equation about linear expression of the error. Therefore, a desirable dynamic response and the stability of the MPPT scheme were maintained across the entire MPPT voltage range. The simulation and experimental results obtained from a 3 KW rated prototype demonstrated the effectiveness of the proposed MPPT scheme.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.33 no.4
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• pp.326-330
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• 2020

Small-scale production control systems for smart manufacturing are becoming increasingly necessary as the manufacturing industry seeks to maximize manufacturing efficiency as the demand for customized product production increases. Correspondingly, the development of an embedded system to realize this capability is becoming important. In this study, we developed an embedded system based on an open source system that is cheaper than a widely applied programmable logic controller (PLC)-based production control system that is easier to install, configure, and process than a conventional relay control panel. This embedded system is system is based on a low-power, high-performance Cortex M4 processor and can be applied to smart manufacturing. It is designed to improve the development environment and compatibility of existing PLCs, control small-scale production systems, and enable data collection through heterogeneous communication. The real-time response characteristics were confirmed through an operation test for input/output control and data collection, and it was confirmed that they can be used in industrial sites.

• The Transactions of the Korean Institute of Electrical Engineers P
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• v.64 no.2
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• pp.79-84
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• 2015

Voltage sags are considered the dominant disturbances affecting power quality. Dynamic voltage restorers(DVRs) are mainly used to protect sensitive loads from the electrical network voltage disturbances such as sags or swells and could be used to reduce harmonic distortion of ac voltages. The typical DVR topology essentially contains a PWM inverter with LC Filter, an injection transformer connected between the ac voltage line and the sensitive load, and a DC energy storage device. For injecting series voltage, the PWM inverter is used and the passive filter consist of inductor(L) and capacitor(C) for harmonics elimination of the inverter. However there are voltage pulsation responses by the characteristic of the LC passive filter that eliminate the harmonics of the PWM output waveform of the inverter. Therefore, this paper presented design and feedback performance of LC filter used in the DVRs. The voltage control by LC filter should be connected in the line side since this feedback method allows a relatively faster dynamic response, enabling the elimination of voltage notches or spikes in the beginning and in the end of sags and strong load voltage THD reduction. Illustrative examples are also included.

• Proceedings of the KIEE Conference
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• 2005.07b
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• pp.1530-1533
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• 2005

Total 12 units of high power klystron-modulator systems as microwave source is under operation for 2.5-GeV electron linear accelerator in Pohang Light Source(PLS) linac. RF power and beam power of klystron are precisely measured for the effective control of electron beam. A precise measurement and measurement equipment with good response characteristics are required for this. Input power of klystron is calculated from the applied voltage and the current on its cathode. Tiny measurement error severely effects RF output power value of klystron. Therefore, special care is needed to measure precise beam voltage. Capacitive voltage divider(CVD) unit is intended for the measurement of beam voltage of 400 kV generated from the pulsed klystron-modulator system. Main parameter to determine the standard capacitance in the high arm of CVD is dielectric constant of insulation oil. Therefore CVD should be designed to have a minimum capacitance variation due to voltage, frequency and temperature in the measurement range. This paper will discuss the analysis of capacitive voltage divider for a pulsed high-voltage measurement, and the empirical relations between capacitance and oil temperature variation.