• The Journal of the Institute of Internet, Broadcasting and Communication
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• v.17 no.3
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• pp.137-143
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• 2017

This paper presents a smart parking guidance system based on IoT car-stoppers. The car-stopper embedding an IoT sensor module has the advantage of easy installation compared to conventional parking sensors buried in ground. The parking status data are transferred to the IoT gateway by the sequential point-to-point communication between the car-stoppers. The data transferred from the IoT gateway are stored in the web server, and parking spaces can be monitored remotely through the Android app in a smart device. An active/sleep cycle method using a watch dog timer is employed to reduce the power consumption of the battery powered car-stopper. The power consumption of the car-stopper is measured to be 80 and 25 mW at the active and sleep mode, respectively. A configuration of ultra-low-power IoT sensor module is proposed to minimize the power consumption in the sleep mode. The operation of the implemented system has been verified in a real-world parking lot.

• Journal of the Korean Institute of Telematics and Electronics A
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• v.31A no.3
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• pp.18-27
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• 1994

An 8-bit 2-stage pipelined current mode A/D converter is designed with a new architecture, where the wideband track-and-hold amplifiers which have 2 integrators in parallel sample input signal twice per clock cycle. The conversion speed of the A-D converter is two times faster than that of conventional pipelined method. The converter is designed to be operated at the power supply voltage of 3.3V with the input dynamic range of 0-256$\mu$A. HSPICE simulation results show the performance of up to 55Msamples/s and power consumption of 150mW with the parameters of ISRC $1.5\mu$m BICMOS process. The chip area is 3${\times}4mm^{2}$.

• Proceedings of the Korean Nuclear Society Conference
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• 1997.05a
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• pp.458-463
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• 1997

A transient natural circulation behavior during a LOCA at hot-standby operation is evaluated for YGN Units 3/4. The plant initial condition is determined within the EOP limitation as suitable to hot-standby mode and the transient scenario is prepared as relevant to evaluation of transient natural circulation. A 0.4% cold leg break with loss of off-site power is calculated with RELAP5/MOD3.2, whose predictability has been verified for SBLOCA natural circulation test, S-NC-8B. Through one hour transient analysis, it is found that the plant has its own decay heat removal capability by natural circulation following a LOCA, at hot-standby mode. Additional calculation is performed to investigate an effect of HPSI flow on natural circulation.

• The Transactions of the Korean Institute of Power Electronics
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• v.2 no.3
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• pp.37-43
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• 1997

Microstepping control of two phase hybrid step motors provides high step resolution as well as smoothness of operation at low speed, and removes most of the resonance phenomena which is undesirable. This paper focuses on the development of a microstepping driver with enhanced performance. The developed microstepping driver can divide one step(l.8 degree) into 128 microsteps and supports current saving mode to remove the thermal problems which results from long time operation.

• Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
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• v.27 no.12
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• pp.63-73
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• 2013

The parameters of electromechanical modes offer considerable insight into the dynamic stability properties of a power system. This paper presents a results of a LFO(low-frequency oscillation) based on the time-synchronized signals measured by synchrophasor in the rolling blackout. Spectral analysis was performed, and critical parameters were estimated using the data acquired from synchrophasors installed in the KEPCO system. As significant modes, a 0.68 Hz oscillation mode that occurred prior to the forced load shedding in the rolling blackout was estimated. Such an oscillation mode can cause an uncontrollable blackout. Therefore, the system should be operated so that significant oscillation modes are not activated. This results can serve as a reference in the future for reliable system operation in the event of a similar blackout.

• Proceedings of the KIPE Conference
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• 2002.07a
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• pp.91-94
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• 2002

This paper presents a novel active common-mode EMI filter for the PWM inverter application. The proposed filter is based on the current sensing and compensation circuit and it utilizes a fast transistor amplifier for the current compensation. The amplifier utilizes an isolated low-voltage dc power supply for its biasing and it is possible to construct the active filter independent of the source voltage of the equipment. Thus the proposed active filter can be used in any application regardless of its working voltage. The effectiveness of the proposed circuit is verified by experimental results.

• Journal of Power Electronics
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• v.11 no.4
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• pp.512-519
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• 2011

This paper gives a detailed analysis of the direct torque control (DTC) strategy in a five-level drive and proposes a 24-sector switching table. The known problems in low-voltage drives such as bearings currents and an overvoltage phenomenon which leads to premature failure are reviewed and the occurrence of these problems in medium voltage drives has been investigated. Then a solutions to these problems is presented and the switching table to deal with these problems is modified. Simulation and experimental results on a 3kVA prototype confirm the proposed solution. In implementing the above strategy a TMS320F2812 is used.

• Proceedings of the KIPE Conference
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• 2001.07a
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• pp.308-311
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• 2001

Most of the battery charger for electric powered forklift truck are controlled by the method of 3-phased constant current and constant voltage. However, these chargers have several disadvantages like a large charger capacity, and a short battery life time. This paper presents a digital type battery charger based on multi-mode control adding a constant power control and several assistant controls in the conventional control. The whole control system is performed by a low cost one-chip micro-controller and completely digitize. So we can get a high precision control and a good reliability.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.22 no.10
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• pp.897-903
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• 2009

We have designed the backward wave oscillator. A power-pulsed generator oscillated at 24 GHz has higher frequency than current one. It is very inportant to prevent microwave from going into the beam diode, since intence microwave will harmfully affect beam generation. Due to the axial mode operation, there exist a critial value of beam energy for the oscillation. By changing the condition at the SWS end, an enhanced performance of the K-band oversized BWO is observed in a low magnetic field region about 0.8T.

• Proceedings of the KIPE Conference
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• 2010.11a
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• pp.173-174
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• 2010

In this paper, authors propose a new buck-boost converter of discontinuous conduction mode (DCM) added electric isolation. The proposed converter with DCM eliminates the complicated circuit control requirement and reduces the size of components. The general converters of high efficiency are made that the power loss of the used switching devices is minimized. To achieve the soft switching operation of the used control switches, the proposed converter uses a lossless snubber capacitor. The proposed converter achieves the soft-switching for all switching devices without increasing their voltage and current stresses. The result is that the switching loss is very low and the efficiency of converter is high. The soft switching operation of the proposed converter is verified by digital simulation and experimental results.