• Proceedings of the KIEE Conference
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• 2003.07a
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• pp.403-405
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• 2003

In this paper, we applied a chaos search method for feeder reconfiguration problem in unbalanced distribution system. Chaos method, in optimization problem, searches the global optimal solution on the regularity of chaotic motions and more easily escapes from local or near optimal solution than stochastic optimization algorithms. The chaos search method applied to the IEEE 13 unbalanced test feeder systems, and the test results indicate that it is able to determine appropriate switching options for global optimum configuration.

• Proceedings of the Korean Institute of IIIuminating and Electrical Installation Engineers Conference
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• 2005.05a
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• pp.74-77
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• 2005

Most of the loads in industrial power distribution systems are balanced and connected to three power systems. However, voltage unbalance is generated at the user's 3-phase 4-wire distribution systems with single & three phase. Voltage unbalance is mainly affected by load system rather than power system. Unbalanced voltage will draws a highly unbalanced current and results in the temperature rise and the low output characteristics at the machine. It is necessary to analyse correct voltage unbalance factor for reduction of side effects in the industrial sites. Voltage unbalance is usually defined by the maximum percent deviation of voltages from their average value, by the method of symmetrical components or by the expression in a more user-friendly form which requires only the three line voltage readings. If the neutral point is moved at the 3-phase 4-wire system by the unbalanced load, by the conventional analytical method, line and phase voltage unbalance leads to different results due to zero-sequence component. This paper presents a new analytical method for phase and line voltage unbalance factor in 4-wire systems. Two methods indicate exact results.

• The Transactions of the Korean Institute of Electrical Engineers B
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• v.54 no.9
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• pp.403-407
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• 2005

Most of the loads in industrial power distribution systems are balanced and connected to three power systems. However, voltage unbalance is generated at the user's 3-phase 4-wire distribution systems with single & three phase. Voltage unbalance is mainly affected by load system rather than power system. Unbalanced voltage will draws a highly unbalanced current and results in the temperature rise and the low output characteristics at the machine. It is necessary to analyse correct voltage unbalance factor for reduction of side effects in the industrial sites. Voltage unbalance is usually defined by the maximum percent deviation of voltages from their average value, by the method of symmetric components or by the expression in a more user-friendly form which requires only the three line voltage readings. If the neutral point is moved by the unbalanced load at the 3-phase 4-wire system. Line and phase voltage unbalance leads to different results due to zero-sequence component. So that it is difficult to analyse voltage unbalance factor by the conventional analytical method, This paper presents a new analytical method for phase and line voltage unbalance factor in 4-wire systems. Two methods indicate exact results.

• Journal of Power Electronics
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• v.19 no.1
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• pp.234-243
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• 2019

Studying the control strategy of a microgrid under the load unbalanced state helps to improve the stability of the system. The magnitude of the power fluctuation, which occurs between the power supply and the load, is generated in a microgrid under the load unbalanced state is called negative sequence reactive power $Q^-$. Traditional power distribution methods such as P-f, Q-E droop control can only distribute power with positive sequence current information. However, they have no effect on $Q^-$ with negative sequence current information. In this paper, a stationary-frame control method for power sharing and voltage unbalance compensation in islanded microgrids is proposed. This method is based on the proper output impedance control of distributed generation unit (DG unit) interface converters. The control system of a DG unit mainly consists of an active-power-frequency and reactive-power-voltage droop controller, an output impedance controller, and voltage and current controllers. The proposed method allows for the sharing of imbalance current among the DG unit and it can compensate voltage unbalance at the same time. The design approach of the control system is discussed in detail. Simulation and experimental results are presented. These results demonstrate that the proposed method is effective in the compensation of voltage unbalance and the power distribution.

• Journal of KIISE:Software and Applications
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• v.34 no.9
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• pp.804-816
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• 2007

Sample training data for machine learning often contain irrelevant information or redundant concept. It is also the case that the original data may include noise. If the information collected for constructing learning model is not reliable, it is difficult to obtain accurate information. So the system attempts to find relations or regulations between features and categories in the teaming phase. The feature selection is to remove irrelevant or redundant information before constructing teaming model. for improving its performance. Existing feature selection methods assume that the distribution of documents is balanced in terms of the number of documents for each class and the length of each document. In practice, however, it is difficult not only to prepare a set of documents with almost equal length, but also to define a number of classes with fixed number of document elements. In this paper, we propose a new feature selection method that considers the impurities among the words and unbalanced distribution of documents in categories. We could obtain feature candidates using the word impurity and eventually select the features through unbalanced distribution of documents. We demonstrate that our method performs better than other existing methods via some experiments.

• Proceedings of the KIEE Conference
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• 2000.07a
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• pp.147-149
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• 2000

This paper describes a power flow method for distribution systems, applying the method of symmetrical component to back/forward sweep method. The proposed algorithm is effective for unbalanced radial distribution system, with process of distributed resource(PQ & PV node), AVR(Auto Voltage Regulator), shunt capacitor. This proposed method compared conventional back/forward sweep method with the using three phase unbalanced distribution systems with 34 nodes.

• Proceedings of the KIEE Conference
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• 2001.07a
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• pp.401-403
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• 2001

This paper describes a power flow method for distribution systems, applying the method of symmetrical component to back/forward sweep method. The proposed algorithm is effective for unbalanced radial distribution system, with process of AVR(Auto Voltage Regulator), shunt capacitor. The proposed method was compared with the conventional Back/forward sweep method by using three phase unbalanced distribution systems of 123 nodes.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.21 no.5
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• pp.672-678
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• 2020

The parallel-feeding operation of an AC traction power supply system has the advantages of extending the power supply section and increasing the power supply capacity by reducing the voltage drop and peak demand caused by a train operation load. On the other hand, the parallel-feeding operation is restricted because of the circulating power flow induced from the phase difference between substations. Moreover, the power supply capacity is limited because of the unbalanced substation load depending on the trainload distribution, which can be changed by the train operation along the railway track. This paper suggests a Thyristor-controlled Phase Angle Regulator (TCPAR) to reduce the circulating power flow and the unbalanced substation load, which depends on the phase difference and the trainload distribution and provides a feasibility study. A dedicated control model of TCPAR is also provided, which uses substation power supplies as the input to control the circulating power flow and an unbalanced substation load depending on the phase difference and the trainload distribution. Simulation studies using PSCAD/EMTDC shows that the proposed TCPAR control model can reduce the circulating power flow and the unbalanced substation load depending on the phase difference and the trainload distribution. The proposed TCPAR can extend the parallel-feeding operation of an AC traction power system and increase the power supply capacity.

• Proceedings of the KIEE Conference
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• 2003.07a
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• pp.396-398
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• 2003

This paper presents the scheme for load model based dispersed generation system (DGs) installation and operation in unbalanced distribution systems. Groups of each individual load model consist of residential, industrial, commercial, official and agricultural load. The main idea of solving fuzzy nonlinear goal programming is to transform the original objective function and constraints into the equivalent multiple objective functions with fuzzy sets to evaluate their imprecise nature for the criterion of power loss minimization, the number or total capacity of DGs and the bus voltage deviation, and then solve the problem using genetic algorithms. The method proposed was applied to IEEE 13 bus test systems to demonstrate its effectiveness.

• The Transactions of the Korean Institute of Electrical Engineers A
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• v.51 no.9
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• pp.467-473
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• 2002

In this paper, a fault location algorithm is suggested for line to line faults in distribution networks. Conventional fault location algorithms use the symmetrical component transformation, a very useful tool for transmission network analysis. However, its application is restricted to balanced network only. Distribution networks are, in general, operated in unbalanced manners, therefore, conventional methods cannot be applied directly, which is the reason why there are few research results on fault location in distribution networks. Especially, the line to line fault is considered as a more difficult subject. The proposed algorithm uses direct 3-phase circuit analysis, which means it can be applied not only to balanced networks but also to unbalanced networks like distribution a network. The comparisons of simulation results between one of conventional methods and the suggested method are presented to show its effectiveness and accuracy.