• Proceedings of the KIEE Conference
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• 1987.11a
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• pp.90-94
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• 1987

A structured user-friendly procedures which enable users to program in GRAFCET form directly from sequence specifications have been developed. Using these procedures, we can program the programmable logic controller (PLC) in sequential control and realize programming, debugging, and real-time monitoring. GRAFCET has many advantages like parallelism expression, so we can expect higher productivity and easier maintenance than boolean language or relay-ladder diagram specification when adapts them to PLC.

• Proceedings of the KIEE Conference
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• 2003.07a
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• pp.302-304
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• 2003

This paper presents the methods to solve the problem about Power System Protection Program(PROSET). PROSET is a overall program system to protect power system and correct it. In the context of the PROSET, it is so difficult to edit database data when topology is changed. When the renewal of data is performed, all changed values are disappeared. Therefore, it will not be expected to know the present situation by using the information of the databases data. So it is necessary to solve this problem. Solution is copy of the user. Database of GRL,GRZ,KYP2D1,KYD2X1,L90 Relay module were developed. We made a database management system for PROSET, therefore I will show this management system briefly.

• The Transactions of the Korean Institute of Electrical Engineers P
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• v.57 no.1
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• pp.46-55
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• 2008

In this paper, we designed the bay control unit that is based on the microprocessors and integrates with the new technology of electrical, electronic, and mechanical fields. Nowadays the customers have required much more integrated multi-protection relay, monitoring, control devices and power management for better and easier maintenance, performance, electrical system analysis and communication according to new trend of switchboard This bay controller supplies those requirements of customers with easy handling and operation. This bay controller provides a graphic display with rear-lit liquid crystal LCD and push buttons as kinds of HMI(Human Machine Interface). This bay controller provides the parameter setting program, control setting program, various editors and fault recording and analysis program on Windows/95/98/NT/2000/XP for HMI. In addition, this bay controller can be set manually and this manual setting function helps user to interface easily.

• The Transactions of the Korean Institute of Electrical Engineers A
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• v.51 no.3
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• pp.143-152
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• 2002

Frequency is regarded as one of most important indices for the operating power systems. Several digital techniques for measuring frequency have been presented in the last decades. This paper proposes a design and implementation an adaptive scheme using phase angle difference calculation fort frequency measuring in power system. The advantages of the proposed technique are demonstrated by fault signals from EMTP simulation and user defined arbitrary signals by Excel program. The proposed technique is compared with the conventional methods. Performance teat results indicate that the proposed technique provides accurate measures in pretence of noise and harmonics and in case faults and is suitable for measurement near-nominal, nominal. and off-nominal frequencies. We can see that It will be useful in microprocessor based relays and digital metiers that need to measure power system frequency.

• Proceedings of the KIEE Conference
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• 1996.07b
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• pp.674-676
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• 1996

In this paper, we suggested the verification method of protective algorithms using EMTDC(Electro-Magnetic Transient DC). In other to verify protective algorithms using EMTDC, we first had to make a user defined component and then applied it to a simple power system with parallel line. By means of this method, We reduced the much time and effort to develop or improve the protective algorithm of digital protective relay. For the future, we apply this method to IDPACS(Integrated Digital Protection and Control System) and intend to implement more reliable digital protective relays.

• ETRI Journal
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• v.42 no.6
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• pp.846-858
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• 2020

The non-orthogonal multiple access (NOMA) technique offers throughput improvement to meet the demands of the future generation of wireless communication networks. The objective of this work is to further improve the throughput by including an underlay cognitive radio network with an existing multi-carrier NOMA network, using cooperative communication. The throughput is maximized by optimal resource allocation, namely, power allocation, subcarrier assignment, relay selection, user pairing, and subcarrier pairing. Optimal power allocation to the primary and secondary users is accomplished in a way that target rate constraints of the primary users are not affected. The throughput maximization is a combinatorial optimization problem, and the computational complexity increases as the number of users and/or subcarriers in the network increases. To this end, to reduce the computational complexity, a dynamic network resource allocation algorithm is proposed for combinatorial optimization. The simulation results show that the proposed network improves the throughput.

• Journal of Korea Multimedia Society
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• v.25 no.2
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• pp.325-334
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• 2022

Digital twin has the advantages of quality improvement and cost reduction, so it is widely applied to various industries. In this paper, a method to implement the major technologies of digital twin easily and quickly is presented. These include data management and relay servers, real-time monitoring applications including remote control interfaces, and direct connection protocols for video streaming. In addition, an algorithm for controlling a two-wheeled vehicle with a 2D interface is also proposed. The implemented system performs near real-time synchronization between the real environment and the virtual space. The delay time that occurs in remote control of the vehicle in the real environment was compared with the results of applying the proposed delay time reduction method. In addition, in the case of 2D interface-based control, an algorithm that can guarantee the user experience was implemented and applied to the actual environment and verified through experiments.

• Journal of the Korea Society of Computer and Information
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• v.19 no.10
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• pp.151-158
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• 2014

In this paper, we have designed and implemented the 'N-screen based solar power monitoring system' using N-screen technology by improving the existing monitoring system that can only be accessed or controlled by PC. The HW of the system is consists of solar power modules, inverter, and relay server. And SW is implemented in consideration of the following three points. First, we applied the N-screen technology in order to support various devices. Second, we applied 1:N communication technology that multiple devices can be connected simultaneously to the relay server. Third, we also considered the security problems between server and devices. The final system has been evaluated through the operational test and received good reviews from the technical and economic point. In the future, we are expecting that this technology will replace the existing monitoring systems in various fields, like smart home, smart building, smart city, smart industry, and smart agriculture, etc.

• The Journal of the Institute of Internet, Broadcasting and Communication
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• v.17 no.5
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• pp.35-42
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• 2017

NOMA (Non-orthogonal multiple access) system is the most promising multiple access technology to satisfy the requirements of the spectral efficiency and the performance of 5G cellular systems. NOMA system simultaneously serves multiple users in the power domain, and adapts SIC (Successive interference cancellation) at the receivers to cancel the interference from multiple users. Since in a realistic wireless fading channel the perfect SIC is impossible, the study of the effect of the imperfect SIC to a NOMA system is necessary. This paper considers a cooperative NOMA system with SIC error, and the performance of the system is analytically derived. And the optimum power allocation to minimize the system performance is obtained. When the transmit power is fixed, the distances between a base station and the relay is considered for different SIC errors. The derived analytical results are verified through Monte Carlo simulation, and the results are perfectly matched.

• KSII Transactions on Internet and Information Systems (TIIS)
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• v.8 no.12
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• pp.4305-4323
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• 2014

In this paper, we investigate the degrees of freedom (DOF) of the Y channel consisting of three single-antenna users and a two-antenna common access relay, where each user intends to exchange independent messages with the other two users with the assistance of the relay. We show that the DOF of this particular scenario is 1.5. In order to prove this result, we firstly derive a DOF upper bound based on cut-set bound by allowing cooperation among users, which shows that the total DOF is upper bounded by 1.5. Then we propose a novel transmission scheme based on asymmetric signal space alignment (ASSA) to demonstrate the achievability of the upper bound. Theoretical evaluation and numerical results confirm that the upper bound can be achieved by utilizing ASSA, which also proves the optimality of the ASSA-based scheme in terms of DOF. Combining the upper bound and achievability, we conclude that the exact DOF is 1.5. Moreover, we present a novel iterative joint beamforming optimization (I-JBO) algorithm to further improve the sum rate. Numerical simulations have been provided to demonstrate the convergence speed and performance advantage of the I-JBO algorithm.