• The Transactions of the Korean Institute of Electrical Engineers A
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• v.52 no.4
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• pp.213-218
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• 2003

In front of the opening of electric distribution market in 2004, it is indispensable to have a proper estimation of power quality index and rower quality cost calculation mechanism which are indispensable to stabilize highly industrialized society and to vitalize the Investment lot electric power system. However, there were not enough measures to reflect the voltage characteristics such as voltage sags and Interruptions which make electric load in unstable operation. This paper suggests power quality index and power quality cost which translate various kinds of voltage records into bus load drop index(BLDI) and bus power quality cost(BPQC) based on aggregated load CBEMA curve. A sample calculation result shows that this method can produces the acceptable power Quality index and costs for utilities and customers requirements.

• Proceedings of the KIEE Conference
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• 2002.11b
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• pp.9-14
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• 2002

In front of the opening of electric distribution market in 2004. it is indispensable to have a proper estimation of power quality index and power quality cost calculation mechanism are indispensable to stabilize highly industrialized society and to vitalize the investment for electric power system. However, there were not enough measures to reflect the voltage characteristics such as voltage sags and interruptions which make electric load in unstable operation. This paper suggests power quality index(LDI) and power quality cost(LDC) which translate various kinds of voltage records into load drop index and cost based on aggregated load CBEMA curve. A sample calculation result shows that this method can produces the acceptable power quality index and costs for utilities and customers requirements.

• The Transactions of The Korean Institute of Electrical Engineers
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• v.64 no.11
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• pp.1571-1577
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• 2015

A new mixed mode control of constant power and constant current for resistance spot welding inverter is proposed to improve the weld quality. The conventional control scheme adopts constant current or constant power control mode, however, it is not easy to guarantee the high weld quality because of the nonlinear resistance characteristics of the welding point. The proposed method utilizes the nonlinear characteristics by measuring the dynamic resistance in real time. Therefore, it is possible for the welder to be controlled adaptively depending on the welding state. Experimental results show that the proposed control scheme improves the weld quality by 6.8 times compared with the conventional constant current mode control.

• Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
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• v.21 no.4
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• pp.45-52
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• 2007

Electric power is an important element in any modern economy. The availability of a reliable power supply at a reasonable cost is important for the economic growth and development of a country. Electric power utilities throughout the world therefore strive to meet customer demands economically with high quality and reliability. As the power industry moves towards open competition, therefore, there has been a call for a methodology by which to evaluate power system reliability through the use of customer interruption characteristics. This paper presents the results of an investigation and analysis of interruption characteristics of an industrial customer in Korea. This study used a direct visit survey to determine the investigation and analysis of electric service quality and the characteristics of industrial customers in Korea. A customer survey conducted throughout Korea via personal interviews of 660 sample customers is presented here. Variation according to characteristics of interruption such as duration, time of day, frequency and day of interruption was also investigated

• Journal of the Korea Convergence Society
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• v.2 no.4
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• pp.21-27
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• 2011

Recently, new distributed power sources such as photovoltaic, wind power, fuel cell systems etc. are energetically interconnected and operated in the distribution feeders, as one of the national projects for alternative energy. When new power sources are considered to be interconnected to distribution systems, bi-directional power flow and interconnection conditions of new power sources may cause several power quality problems like voltage sag, voltage swell, harmonics, since new power sources can change typical characteristics of distribution systems. Under these situations, this paper deals with the analysis the power quality problems at primary and secondary feeders in distribution systems, when new power sources like photovoltaic (PV) systems are interconnected, by using the test devices for PV systems based on the LabVIEW S/W. This paper presents the test device which is consisted with model distribution system and model PV systems. By performing the simulation for power quality operation characteristic based on the test facilities, this paper presents the optimal countermeasures for power quality.

• Journal of Power System Engineering
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• v.19 no.2
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• pp.84-89
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• 2015

The occurrence of algae caused by eutrophication of fresh water is a pollution source to destroy the aquatic environment. When the high voltage electric field is applied in the water, When a high voltage is applied to the electric field in the water, the algae can be broken the balance of cell membranes, and is dead. In this paper, we develop a water quality improvement system for generating an electric field having a higher energy than the zeta potential when a high voltage is applied to 4,000V. To ensure the mobility of the water quality improvement system, we designed the PV generation system using the optimal size technique that is based on the model of power lack ratio. By evaluating the output characteristics of the water quality improvement system, power generation characteristics of the PV generation system, and battery charging characteristics, we can show that the proposed system can be applicable to the water quality improvement system inhibiting the growth rate of the algae in the fresh water.

• Journal of the East Asian Society of Dietary Life
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• v.18 no.3
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• pp.345-352
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• 2008

This study investigated the utilization of tofu stake with turmeric manufacture by analyzing its effects on quality characteristics and shelf-life of tofu made with 0.5 CT(0.5% turmeric power), 1.0 CT(1.0% turmeric power), 1.5 CT(1.5% turmeric power), and 2.0 CT(2.0% turmeric power) in comparison with those ST(standard), In color lightness tofu stake springiness decreased with increasing turmeric power content, while cohesiveness was higher than ST. The gumminess of tofu stake decreased with increasing turmeric power content, while brittleness was higher than ST. Water content of turmeric power tofu stake was higher than ST. Weight of tofu stake increased with increasing turmeric power content, while cooking loss decreased with increasing turmeric power content. Thiobarbituric acid content of turmeric power tofu stake decreased with increasing turmeric power content. For overall acceptability, $0.5{\sim}1.0%$ turmeric power tofu stake attained the highest score.

• The Transactions of The Korean Institute of Electrical Engineers
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• v.65 no.4
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• pp.617-621
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• 2016

In addition to the energy storage facilities based on high power technologies, Electric double layer capacitors(EDLC) are today's candidate for power quality stabilization. However, its low energy density is often inhibiting factor for application of electric power industry. Hybrid supercapacitor is an promising energy storage device that positioned between conventional EDLC and Li-ion battery. This paper describes the preparation and characteristics of a hybrid supercapacitor and module for power quality stabilization. A cylindrical 3200F hybrid supercapacitor ($60{\times}74.5mm$) was assembled by using the $Li_4Ti_5O_{12}$ electrode as an anode and activated carbon as a cathode. It shows 2.5 times higher energy density than conventional EDLC with the same volume. In order to determine the characteristics of the hybrid supercapacitor Module for uninterruptible power supply (UPS), hybrid supercapacitor cells were connected in series with active balancing circuit. At even the high current density of 14A(10C), Module prepared by 18 cells showed the capacitance of 170F at 30~50V, suggesting the applicability for UPS.

• New & Renewable Energy
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• v.5 no.3
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• pp.4-12
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• 2009

The effect of change in DFIG (doubly-fed wind power generator) rotating speed and active power on the grid was analyzed to understand the characteristics of wind power using the wind power simulator connected to the grid at Gochang Power Quality Test Center. Electric power quality improvement devices (DVR, STATCOM, SSTS) and electric power quality disturbance application devices for 22.9 kV grid are equipped at Gochang Power Quality Test Center. Induction motor and VVVF inverter were used to emulate the blade of a wind power generator, and a simulator for Cage wound induction generator and DFIG was developed. The trial line were assumed to be 20 km and 40 km in length, and variable wind speed pattern was set using wind speed data from Ducjeokdo to verify the power characteristics of the wind power generator according to rotating speed.

• Journal of Electrical Engineering and Technology
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• v.9 no.4
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• pp.1171-1181
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• 2014

Different power quality (PQ) disturbance sources can have major impacts on the power supply grid. This study proposes, for the first time, an early warning approach to identifying PQ problems and providing early warning prompts based on the monitored data of PQ disturbance sources. To establish a steady-state power quality early warning index system, the characteristics of PQ disturbance sources are analyzed and summed up. The higher order statistics anomaly detection (HOSAD) algorithm, based on skewness and kurtosis, and hierarchical power quality early warning flow, were then used to mine limit-exceeding and abnormal data and analyze their severity. Cases studies show that the proposed approach is effective and feasible, and that it is possible to provide timely power quality early warnings for limit-exceeding and abnormal data.