• Journal of Power Electronics
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• v.15 no.5
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• pp.1329-1337
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• 2015

By placing distributed generation power sources beside a big nonlinear load, these sources can be used as a power quality enhancer, while injecting some active power to the network. In this paper, a new scheme to use the distributed generation power source in both operation modes is presented. In this scheme, a fuzzy controller is added to adjust the optimal set point of inverter between compensating mode and maximum active power injection mode, which works based on the harmonic content of the nonlinear load. As the high order current harmonics can be easily rejected using passive filters, the DG is used to compensate the low order harmonics of the load current. Multilevel transformerless cascade inverters are preferred in such utilization, as they have more flexibility in current/voltage waveform. The proposed scheme is simulated in MATLAB/SIMULINK to evaluate the circuit performance. Then, a 1kw single phase prototype of the circuit is used for experimental evaluation of the paper. Both simulative and experimental results prove that such a circuit can inject a well-controlled current with desired harmonics and THD, while having a smaller switching frequency and better efficiency, related to previous 3-phase inverter schemes in the literature.

• Journal of Information Technology Services
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• v.17 no.3
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• pp.139-156
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• 2018

Smart tolling, which improved the drawbacks of the existing high-pass system, was developed and built through the Smart Highway R & D project in 2007. In order to successfully introduce and spread Smart Tolling, it is need to analyze factors that affected by intent to use. This study conducted research based on literature studies and empirical studies, and developed a research model to analyze factors affecting the users' intention of smart tolling system based on technology acceptance model (TAM) and value based acceptance model. The main variables of the research model are service characteristics (convenience, reliability), technical characteristics (flexibility, stability), environmental characteristics (switching cost, effectiveness of policy) and intention to use. To test the hypotheses set in this study, frequency analysis, exploratory factor analysis, and confirmatory factor analysis were performed using the SPSS 22.0 program statistical package and AMOSS 18.0. The convenience and reliability presented by service characteristics did not affect the intention to use of smart tolling service.

• Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
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• v.14 no.1
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• pp.82-88
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• 2000

In this paper, We present a low cost auxiliary circuit of $S^4-PFC$converter with the feedback winding, which can improve the input current waveform with the maintenance of limited DC Bus Voltage and high efficiency. The converter with feedback winding was analyzed to demonstrate the proposed converter. Int order to verify the performance of the proposed converter, we designed the converter which operates at the output of 5[V], 65[W] and switching frequency of 100[kHz] within the universal line voltage. Implemented converter has decreased line current peak value by 50[%] compared with the conventional converters and the power utilization was increased in the line period.

• Transactions on Electrical and Electronic Materials
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• v.14 no.5
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• pp.235-241
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• 2013

A low power CMOS control circuit is applied in an integrated DC-DC buck converter. The integrated converter is composed of a feedback control circuit and power block with 0.35 ${\mu}m$ CMOS process. A current-sensing circuit is integrated with the sense-FET method in the control circuit. In the current-sensing circuit, a current-mirror is used for a voltage follower in order to reduce power consumption with a smaller chip-size. The N-channel MOS acts as a switching device in the current-sensing circuit where the sensing FET is in parallel with the power MOSFET. The amplifier and comparator are designed to obtain a high gain and a fast transient time. The converter offers well-controlled output and accurately sensed inductor current. Simulation work shows that the current-sensing circuit is operated with an accuracy of higher than 90% and the transient time of the error amplifier is controlled within $75{\mu}sec$. The sensing current is in the range of a few hundred ${\mu}A$ at a frequency of 0.6~2 MHz and an input voltage of 3~5 V. The output voltage is obtained as expected with the ripple ratio within 1%.

• Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
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• v.25 no.4
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• pp.117-123
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• 2011

Lightning and switching surges propagating through the grounding conductors lead to transient overvoltages, and electronic circuits in information technology systems are very susceptible to damage or malfunction from the electrical surges. Surge damages or malfunctions of electrical and electronic equipment may be caused by potential rises. To solve these problems, it is very important to evaluate the ground surface potential rises and hazardous voltages such as touch and step voltages at or near the grounding systems energized by electrical surges. In this paper, the performance of grounding systems against the surge current containing high frequency components on the basis of the actual-sized tests is presented. The ground surface potential rises and hazardous voltages depending on impulse currents for vertical or horizontal grounding electrodes are measured and analyzed. Also the touch and step voltages caused by the impulse currents are investigated. As a result, the ground surface potential rises, the touch and step voltages near the grounding electrodes are raised and the conventional grounding impedances are increased as the front time of the injected impulse currents is getting faster.

• Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
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• v.22 no.4
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• pp.35-45
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• 2008

This paper present the Three-Level converter using IM(Integrated Magnetics) method for high power application. In power conversion system, magnetic components are important devices used for energy storage, energy transfer, galvanic isolation and filtering. The proposed Three-Level converter is to reduce the number of magnetic components using transformer integrated with output inductor. This paper proposes reluctance model base on the magnetic analysis for the Three-Level converter. Also, the secondary rectification was discussed by a single core transformer winding. A protype featuring 540[V] input, 48[V] output, 40[kHz] switching frequency, and 3[kW] output power using IGBT.

• The Transactions of the Korean Institute of Power Electronics
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• v.11 no.2
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• pp.135-141
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• 2006

In this paper, LC output filters are designed to reduce output harmonics and harmonic analysis are peformed. Generally, multilevel inverters are used in high power application and operates with low switching frequency, which, in turn, generates large output harmonics. Output filters we used to reduce output harmonics. The design approach to reduce output harmonics of the 31eve1 multilevel inverter is discussed and DSP(TMS320C31) is used for the digital control of the system. The design example is given. The designed system is verified by simulation and experiment.

• Journal of Electrical Engineering and Technology
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• v.10 no.2
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• pp.574-585
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• 2015

This paper aims to improve the performance of conventional direct torque control (DTC) drives proposed by Takahashi by extending the idea for 5-level inverter. Hybrid cascaded H-bridge topology is used to achieve inverter voltage vector composed of 5-level of voltage. Although DTC is very popular for its simplicity but it suffers from some disadvantages like- high torque ripple and uncontrollable switching frequency. To compensate these shortcomings conventional DTC strategy is modified for five levels voltage source inverter (VSI). Multilevel hysteresis controller for both flux and torque is used. Optimal voltage vector selection from precise lookup table utilizing 12 sector, 9 torque level and 4 flux level is proposed to improve DTC performance. These voltage references are produced utilizing a hybrid cascaded H-bridge multilevel inverter, where inverter each phase can be realized using multiple dc source. Fuel cells, car batteries or ultra-capacitor are normally the choice of required dc source. Simulation results shows that the DTC drive performance is considerably improved in terms of lower torque and flux ripple and less THD. These have been experimentally evaluated and compared with the basic DTC developed by Takahashi.

• Journal of Korea Society of Industrial Information Systems
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• v.22 no.2
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• pp.71-78
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• 2017

In This Paper, A DC-DC Boost Converter for Portable Device has been Proposed. The Converter Which is Operated with 1 MHz High Switching Frequency is Capable of Reducing Mounting Area of Passive Devices Such as Inductor and Capacitor, Consequently is Suitable for Portable Device. This Boost Converter Consists of a Power Stage and a Control Block and a Protect Block. Proposed DC-DC Boost Converter has been Designed a 0.18 um Magnachip CMOS Process Technology, we Examined Performances of the Fabricated Chip and Compared its Measured Results with SPICE Simulation Data. Simulation Results Show that the Output Voltage is 4.8 V in 3.3 V Input Voltage, Output Current 95 mA Which is Larger than 20~50 mA.

• Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
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• v.20 no.1
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• pp.100-110
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• 2006

This paper presents the demagnetization and iron loss analysis of the single phase Flux Reversal Machine. It has a magnetic configuration similar to the switched reluctance machine but with multipole permanent magnets of alternate polarity on each stator salient pole embraced by concentrated coils. But it can be demagnetized by sudden over current and core losses increase because switching frequency is getting faster. This paper show demagnetization of permanent magnet and iron loss characteristic, and proposed a solution.