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82 results on '"Oh, Yun-Sik"'

10. A Method for Fault Section Identification of Distribution Networks Based on Validation of Fault Indicators Using Artificial Neural Network.

Author

Kim, Myong-Soo, An, Jae-Guk, Oh, Yun-Sik, Lim, Seong-Il, Kwak, Dong-Hee, and Song, Jin-Uk

Subjects
FAULT currents, FAULT location (Engineering), DISTRIBUTED power generation, COMMUNICATION infrastructure, ARTIFICIAL neural networks
Abstract

A fault section in Korean distribution networks is generally determined as a section between a switch with a fault indicator (FI) and a switch without an FI. However, the existing method cannot be applied to distribution networks with distributed generations (DGs) due to false FIs that are generated by fault currents flowing from the load side of a fault location. To identify the false FIs and make the existing method applicable, this paper proposes a method to determine the fault section by utilizing an artificial neural network (ANN) model for validating FIs, which is difficult to determine using mathematical equations. The proposed ANN model is built by training the relationship between the measured A, B, C, and N phase fault currents acquired by numerous simulations on a sample distribution system, and guarantees 100% FI validations for the test data. The proposed method can accurately distinguish genuine and false Fis by utilizing the ability of the ANN model, thereby enabling the conventional FI-based method to be applied to DG-connected distribution networks without any changes to the equipment and communication infrastructure. To verify the performance of the proposed method, various case studies considering real fault conditions are conducted under a Korean distribution network using MATLAB. [ABSTRACT FROM AUTHOR]

Published
2023
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12. An Optimization-Based Intentional Islanding Scheme for Service Restoration in Distribution Systems Considering Anti-Parallel Operation of Distributed Generations.

Author

Qiu, Bangjie, An, Jae-Guk, Song, Jin-Uk, and Oh, Yun-Sik

Subjects
DISTRIBUTED power generation, FAULT location (Engineering), ISLANDS, POWER resources, GENETIC algorithms
Abstract

An islanding operation of distributed generations (DGs) in emergencies due to a fault in distribution systems can be a means of power supply for important loads in outage areas by facilitating the self-sufficient capability of DGs forming microgrids. This paper presents an optimization-based intentional islanding scheme to derive a near-optimal service restoration (SR) plan. The anti-parallel operation of DGs is considered a new constraint that avoids more than two DGs in an island thereby, enabling simpler control and operation of the distribution system in an emergency. Each island is created by an island partitioning scheme based on the tree representation of the network and fast searching scheme for the tree structure considering load importance, and a genetic algorithm (GA) is utilized to explore possible SR solutions. Case studies on IEEE 69-bus distribution system according to various fault locations are conducted, and the simulation results show that the proposed scheme can restore more loads with higher priority in outage areas by the intentional islanding of DGs. Furthermore, the time for deriving the optimal solution can be reduced since the evaluations for infeasible solutions are not performed. [ABSTRACT FROM AUTHOR]

Published
2023
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15. Protection Coordination Using Superconducting Fault Current Limiters in Microgrids

Author

Oh， Yun-Sik, Raza Haider, Muhammad Saeed Uz Zaman, Kim， Chul-Hwan, Zahoor Ahmed, Muhammad Mehdi, and Syed Basit Ali Bukhari

Subjects
Interconnection, business.industry, Computer science, 020209 energy, 02 engineering and technology, Fault (power engineering), Reliability engineering, Power (physics), law.invention, Electric power system, Relay, law, Distributed generation, 0202 electrical engineering, electronic engineering, information engineering, Microgrid, business, MATLAB, computer, computer.programming_language
Abstract

Power generating units in the form of distributed generation (DG) are integrating with microgrid (MG) systems to supply reliable power to users. The trend of an integrated power supply is increasing continually to meet growing energy demands. Besides certain advantages of the MG system, some interconnection and system protection issues pose a challenge in terms of implementation. These problems need to be addressed in order to facilitate smooth operation of power systems. Superconducting fault current limiters (SFCLs) provide the best performance and unique protection features to electrical power systems during various fault conditions. This paper describes modeling, characterization, and implementation of SFCL in an MG system to enhance protection coordination. The proposed SFCL is modeled in MATLAB/ Simulink software and the performance of the system is validated through simulation results. It is also shown that the proposed SFCL provides a means of better relay coordination during various fault conditions. This is achieved by incorporating well-calculated design parameters of SFCL and its placement at optimal locations.

Published
2017

21. Shear stress induces noncanonical autophagy in intestinal epithelial monolayers

Author

Kim, Sun Wook, primary, Ehrman, Jonathan, additional, Ahn, Mok-Ryeon, additional, Kondo, Jumpei, additional, Lopez, Andrea A. Mancheno, additional, Oh, Yun Sik, additional, Kim, Xander H., additional, Crawley, Scott W., additional, Goldenring, James R., additional, Tyska, Matthew J., additional, Rericha, Erin C., additional, and Lau, Ken S., additional

Published
2017
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37. Passive islanding detection scheme based on autocorrelation function of modal current envelope for photovoltaic units.

Author

Haider, Raza, Kim, Chul Hwan, Ghanbari, Teymoor, Bukhari, Syed Basit Ali, Saeed uz Zaman, Muhammad, Baloch, Shazia, and Oh, Yun Sik

Abstract

Islanding detection in power systems poses a challenge that can result in technical problems and safety hazards. This study examines a new passive islanding detection method for photovoltaic‐based distributed generation (DG) units. The modal signal of the three‐phase current and its envelope are calculated for a targeted DG unit. Variance in the autocorrelation of the modal current envelope (VAMCE) is used as an islanding detection criterion in the proposed method. The proposed method employs autocorrelation function (ACF) of modal current envelope (derived by Hilbert‐transform‐based approach) to extract the transient content. Then, the variance of the ACF is calculated, called criterion VAMCE to distinguish between islanded and normal operating conditions. The main advantage of the proposed technique is more relevant to its more accuracy and smaller non‐detection zone in comparison with the other similar passive techniques. Since the VAMCE has significant variation during islanding conditions and negligible change in normal conditions, it can be used for detection of islanding condition effectively. The method was evaluated through several simulations under different islanded and normal operating conditions. The results confirm that the proposed method has better accuracy and speed compared to other similar methods. [ABSTRACT FROM AUTHOR]

Published
2018
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