• Journal of international Conference on Electrical Machines and Systems
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• 제3권2호
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• pp.176-183
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• 2014

Three-phase four-wire distribution systems are used for both three-phase three-wire loads and single-phase two-wire consumer appliances in South Korea, Myanmar and other countries. Unbalanced load conditions frequently occur in these distribution systems. These unbalanced load conditions cause unbalanced voltages for three-phase and single-phase loads, and increase the loss in the distribution transformer. In this paper, we propose constant DC capacitor voltage control based strategy for the active load balancer (ALB) in the three-phase four-wire distribution systems. Constant DC capacitor voltage control is always used in active power line conditioners. The proposed control strategy does not require any computation blocks of the active and reactive currents on the distribution systems. Balanced source-side currents with a unity power factor are obtained without any calculation block of the unbalanced active and reactive components on the load side. The basic principle of the constant DC capacitor voltage control based strategy for the ALB is discussed in detail and then confirmed by both digital computer simulations using PSIM software and prototype experimental model. Simulation and experimental results demonstrate that the proposed control strategy for the ALB can balance the source currents with a unity power factor in the three-phase four-wire distribution systems.

• The Journal of the Institute of Internet, Broadcasting and Communication
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• 제16권4호
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• pp.159-164
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• 2016

In or to generate high electric power in increasing demand, power station should operate facilities to meet requirement. The scale of electric power equipment is increasing in both size and complexity. With unexpected accidents at power facilities or power stations happening, substantial socioeconomic losses in an industrial society is caused. A major cause of unexpected accidents is deterioration of dielectrics, isolating two conductors electrically. In order to detect the deterioration processes of power cables, the operation status of power cables should be monitored on a regular basis. We have invented and installed equipment at Korea Western Power Co., Ltd., located in Taean, in order to predict and prevent the deterioration status of dielectrics destruction of power cables. The main line in Y-connection to the secondary coils of transformer delivers electric power to the external devices. The equipment we developed is the one measuring insulation resistance of cables operation in on/off status with respect to the main line. We present the equipment in terms of operation and configuration of hardware side.

• Journal of the Institute of Convergence Signal Processing
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• 제9권4호
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• pp.321-328
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• 2008

In this paper, we propose the hardware architecture of two-dimensional discrete wavelet transform (2D DWT) and quantization for using JPEG2000. Color 2-D DWT processor is proposed that is to apply to JPEG 2000 Hard-wired Encoder. JPEG 2000 DWT processor uses the Daubechies' (9,7) bi-orthogonal filter, and we design by minimizing error of the DWT transformer by ${\pm}1$ LSB during compression and decompression. We designed the DWT filters that using by using shift and adder structure instead of multiplier structure which raise the hardware complexity. It is improve the operation speed of filters and reduce the hardware complexity. The proposed system is designed by the hardware description language Verilog-HDL and verified by Synopsys Design Analyzer using TSMC 0.25${\mu}m$ ASIC library.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• 제21권6호
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• pp.553-563
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• 2010

This paper presents a tapered slot-antenna(TSA) for optimal impulse-signal transmission in ultra-wide band(UWB). The proposed TSA provides radiates in end-fire direction, which meets an impulse-radio UWB(IR-UWB) system demands(e.g., low loss, thus less error throughout the UWB band). In order to minimize the pulse distortion, we used an wideband impedance transformer and a microstrip slotline. The pulse fidelity characteristics was evaluated with finite-difference time-domain(FDTD) analysis technique and pulse fidelity correlation equation. Approximately 93.89 % pulse fidelity was obtained between the two antennas in 0.5 m range. Additionally, derived chirp Z-transform algorithm enables us to utilize the zoom-in option on the pulse signal in few nano-seconds below. Thus, it is possible to analyze the pulse signal distortion, delay or dispersion characteristics.

• The Transactions of The Korean Institute of Electrical Engineers
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• 제61권10호
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• pp.1542-1547
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• 2012

Asynchronous phenomenon occurs on the synchronous generators under power system when a generator's amplitude of electromagnetic force, phase angle, frequency and waveform etc become different from those of other synchronous generators which can follow instantly varying speed of turbine. Because the amplitude of electromagnetic force, phase frequency and waveform differ from those of other generators with which are to be put into parallel operation due to the change of excitation condition for load sharing and the sharing load change, if reactive current in the internal circuit circulates among generators, the efficiency varies and the stator winding of generators are overheated by resistance loss. When calculation method of protection settings and logic for protection of generator asynchronization will be recommended, a distance relay scheme is commonly used for backup protection. This scheme, called a step distance protection, is comprised of 3 steps for graded zones having different operating time. As for the conventional step distance protection scheme, zone 2 can exceed the ordinary coverage excessively in case of a transformer protection relay especially. In this case, there can be overlapped protection area from a backup protection relay and, therefore, malfunctions can occur when any fault occurs in the overlapped protection area. Distance relays and overcurrent relays are used for backup protection generally, and both relays have normally this problem, the maloperation, caused by a fault in the overlapped protection area. Corresponding to an IEEE standard, this problem can be solved with the modification of the operating time. On the other hand, in Korea, zones are modified to cope with this problem in some specific conditions. These two methods may not be obvious to handle this problem correctly because these methods, modifying the common rules, can cause another coordination problem. To overcome asynchronizing protection, this paper describes an improved backup protection coordination scheme using a new logic that will be suggested.

• The Transactions of the Korean Institute of Power Electronics
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• 제7권6호
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• pp.570-578
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• 2002

Cathodic protection is widely used to prevent corrosion of steel materials buried in the underground and sea. As a rectifier for cathodic protection, the conventional phase-controlled rectifiers have been used so far in spite of such shortcomings as large volume, heavy weight and floor power factor. In order to overcome such disadvantages, this paper proposes a new module-type switching rectifier for cathodic protection, which is composed of two parts, namely, AC/DC converter and module- type DC/DC converter. The AC/DC converter is a single-phase IGBT PWM rectifier, thus resulting in almost unity power factor and controlled DC output voltage. The module-type DC/DC converter operates under ZVS/ZCS switching condition to permit high frequency switching operation. It enables to use high-frequency transformer for electrical isolation, thus reducing volume and weight of overall system and improving system efficiency. It should be anticipated that the proposed rectifier techniques apply to the similar technical areas.

• Proceedings of the KIEE Conference
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• 대한전기학회 2009년도 제40회 하계학술대회
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• pp.1587_1588
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• 2009

In this paper, PCB embedded balanced-to-unbalamced duplexer using coupled LC resonator was introduced for low cost dualband WiMax front-end-module application. In order to obtain the function of bandpass filter and balun transformer, proposed duplexer was configured by using magnetically coupled LC resonator. Out-of-band suppression was enhanced by applying two m-Derived transform circuits to obtain transmission zeros at 2GHz and 4.8GHz. In order to reduce the size of embedded duplexer, BaSrTiO3 (BST) composite high Dk RCC film was applied to improve the capacitance density. This high Dk film provided the capacitance density of 12.2 pF/mm2. The simulation results shows that fabricated duplexer had an insertion loss of 2.9dB and 5.5dB and return loss of 15dB and 16dB for 2.5GHz~2.6GHz and 3.5GHz~3.6GHz, respectively. The maximum magnitude and phase imbalance were 0.01dB and 0.17dB, and 1degree and 2degree in its passband, respectively. The out-of-band suppression was observed approximately 29dB and 40dB below 1.9GHz and over 4.5GHz, respectively. It has a volume of 6 mm $\times$ 7 mm $\times$ 0.7 mm (height).

• Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
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• 제20권1호
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• pp.138-143
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• 2006

This research emphasis the commercialize and experiment in the quality of water treatment by making water treatment reactor. The hybrid water plasma torch used this research is excellent in tans of economical efficiency because of using existent neon transformer. Further more, It has excellent energy efficiency because it is manufactured by low electric power. Especially hybrid water plasma torch used this research has two filed of water plasma and inputs each strong point into the water. Following The data such as dissolved ozone(2.8[ppm]), hydrogen peroxide(100[ppm]), 2[PH], are very affordable data and immensely useful in sterilization. Those data have excellent result: perfect eradication of a colon bacillus within maximum 10 minute applying to sterilization processing of a colon bacillus.

• Journal of the Korean Society of Safety
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• 제33권5호
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• pp.15-20
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• 2018

This paper describes the fusing time characteristics of Light PVC Sheathed Circular Cord(VCTF) and Tray Frame Retardant(TFR) cables according to increased temperature under over current condition. The experimental equation will be used to determine the validity and reliability of the test results. The over current flowed 3, 5 and 10 times higher than the amount of allowable current using DC power supply with DAQ(Data Acquisition) measurement system. An infrared radiation heater, which was controlled by a variable AC auto transformer, was used to increase the temperature from room temperature to 50, 100 and 150 degrees Celsius. First, two type of cables were analyzed those with different cross-sectional areas with in the same structure and those with different structures with in the same cross-sectional areas. Then, it was determined how fusing time had been influenced according to the cross-sectional areas and different structures, respectively. The cable resistance was increased by joule heating according to increasing temperature. Therefore, the allowable current of cable is decreased. Finally, the fusing time of the cable was decreased due to increased temperatures at current flow, which were 3 times the amount of allowable current. The instantaneous breakdown was observed when current flow was 5 and 10 times over the amount of allowable current. The fusing time is directly affected by the structure of cable insulation.

• The Transactions of the Korean Institute of Power Electronics
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• 제3권3호
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• pp.231-239
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• 1998

This paper presents the dynamic analysis and control loop design of a zero voltage switching full bridge (ZVS-FB) PWM DC/DC converter. The small-signal model is derived incorporating the effects of phase shift control and the utilization of transformer leakage inductance and power FET junction capacitance to achieve zero voltage resonant switching. These effects are modeled by introducing additional feedforward and feedback terms for duty cycle modulation. Based on the results of the small-signal analysis, the control loop is designed using a simple two-pole one-zero compensation circuit. To show the validity of the design procedures, the small signal analysis of the closed loop system is carried out and the potential of the zero voltage switching and the superiority of the dynamic characteristics are verified through the experiment with a 2 kW prototype converter.