• International Journal of Control, Automation, and Systems
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• v.6 no.5
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• pp.651-659
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• 2008

Autoreclosing techniques have been used in power systems to maintain system stability and continuity of supply. Environmental and economical issues have driven significant increases in the development of distributed generation (DG). DG connected to distribution systems, however, may impose negative influences with respect to power quality, protection, and stability, because DG can cause some challenges to protection, especially to reclosing. For this reason, in order to improve the reliability and safety of the distribution system, the rules and guidelines suggest that the DG system needs to be rapidly disconnected from the system before reclosing. We present, in this paper, an adaptive reclosing algorithm considering the DG. The algorithm consists of an angle oscillation's judgment, the emergency extended equal-area criterion (EEEAC), the calculation of an optimal reclosing time, and a reconnection algorithm. Our simulation results for three different DG technologies with Electromagnetic Transient Program (EMTP) indicate that we can maintain transient stability while the DG is protected against disturbances.

• Proceedings of the KIPE Conference
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• 2012.11a
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• pp.33-34
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• 2012

As the distributed power system with PV and ESS is highlighted to be one of the most prominent structure to replace the traditional electric power system, power flow scheduling is expected to bring better system efficiency. Optimal energy management system (EMS) where the power from PV and the grid is managed in time-domain using ESS needs an optimization process. In this paper, main optimization method is implemented using dynamic programming (DP). To overcome the drawback of DP in which ideal future information is required, prediction stage precedes every EMS execution. A simple auto-regressive moving-average (ARMA) forecasting followed by a PI-controller updates the prediction data. Assessment of the on-line optimal EMS scheme has been evaluated on several cases.

• 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.

• The Transactions of The Korean Institute of Electrical Engineers
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• v.59 no.10
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• pp.1776-1786
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• 2010

Intelligent distribution automation system have total monitoring and control capability. The system covers substation, distribution network, distributed generations and customers at HV system. Various intelligent distribution facilities installed at distribution systems have voltage sensor, current sensor, aging monitoring sensor. Intelligent Feeder Remote Terminal Unit (IFRTU) tied to intelligent distribution facilities process information from facilities and it checks information of fault, power quality and aging of distribution facilities. The information is transmitted to master station through communication line. The master station have remote monitoring system covers substation, distribution network, distributed generations and customers. It also have various application programs that maintain optimal network operation by using information from on-site devices.

• Journal of Electrical Engineering and Technology
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• v.13 no.5
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• pp.1778-1790
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• 2018

Based on the requirements and characteristics of multi-zone autonomous decision-making in modern power system, fully distributed computing methods are needed to optimize the economic dispatch (ED) problem coordination of multi-regional power system on the basis of constructing decomposition and interaction mechanism. In this paper, four fully distributed methods based on alternating direction method of multipliers (ADMM) are used for solving the ED problem in distributed manner. By duplicating variables, the 2-block classical ADMM can be directly used to solve ED problem fully distributed. The second method is employing ADMM to solve the dual problem of ED in fully distributed manner. N-block methods based on ADMM including Alternating Direction Method with Gaussian back substitution (ADM_G) and Exchange ADMM (E_ADMM) are employed also. These two methods all can solve ED problem in distributed manner. However, the former one cannot be carried out in parallel. In this paper, four fully distributed methods solve the ED problem in distributed collaborative manner. And we also discussed the difference of four algorithms from the aspects of algorithm convergence, calculation speed and parameter change. Some simulation results are reported to test the performance of these distributed algorithms in serial and parallel.

• Proceedings of the KIEE Conference
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• 2002.07d
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• pp.2292-2294
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• 2002

This paper presents the network of Distributed Control System(DCS) considering specification of nuclear power plant. The network is composed of field network, control network and information network. The protocol of control network is ring type and it is compared to ethernet type. This paper proposes the structure of DCS, the protocol of each network and analyzes the network traffic along data capacity of field network, control network, information network and the network performance. Network II.5 is used as traffic simulation tool.

• Journal of Power Electronics
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• v.16 no.4
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• pp.1578-1586
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• 2016

A power quality improvement scheme for grid connected inverters, even in the presence of the disturbances in grid voltages due to harmonic distortions and three-phase imbalance, is presented for distributed generation (DG) power systems. The control objective is to force the inverter currents to follow their references with robustness even under external disturbances in grid voltages. The proposed scheme is realized by a disturbance observer (DOB) based current control scheme. Since the uncertainty in a system can be effectively canceled out using an estimated disturbance by the DOB, the resultant system behaves like a closed-loop system consisting of a disturbance-free nominal model. For experimental verification, a 2 kVA laboratory prototype of a grid connected inverter has been built using a digital signal processor (DSP) TMS320F28335. Through comparative simulations and experimental results under grid disturbances such as harmonic distortion and imbalance, the effectiveness of the proposed DOB based current control scheme is demonstrated.

• Journal of Power Electronics
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• v.17 no.6
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• pp.1650-1657
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• 2017

In this study, the distributed secondary voltage control of islanded microgrids with multi-agent consensus algorithm is investigated. As an alternative to a time-triggered approach, an event-triggered scheme is proposed to reduce the communication load among inverter-based distributed generators (DGs). The proposed aperiodic control scheme reduced unnecessary utilization of limited network bandwidth without degrading control performance. By properly establishing a distributed triggering condition in DG local controller, each inverter is only required to send voltage information when its own event occurs. The compensation of voltage amplitude deviation can be realized, and redundant data exchange related to fixed high sampling rate can be avoided. Therefore, an efficient use of communication infrastructure can be realized, particularly when the system is operating in steady state. The effectiveness of the proposed scheme is verified by simulations on a microgrid test system.

• KEPCO Journal on Electric Power and Energy
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• v.5 no.2
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• pp.67-74
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• 2019

Recently, as the renewable distributed energy resources has increased, the variability within the electrical power distribution system has increased, so that there is a growing concern about the stable electrical power distribution system. For efficient management of future electrical power distribution system, it is necessary to improve the electrical power distribution system operation using new visualization technology. In this paper, we describe the current status of GIS introduction and related technology trends in the field of electrical power distribution, and analyze the necessity of GIS system for electrical power distribution system operation and problems to be solved when introducing GIS technology.

• Journal of Information Processing Systems
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• v.13 no.6
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• pp.1602-1612
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• 2017

Since rapidly disseminating of Internet of Things (IoT) as the new communication paradigm, a number of studies for various applications is being carried out. Especially, interest in the smart medical system is rising. In the smart medical system, a number of medical devices are distributed in popular area such as station and medical center, and this high density of medical device distribution can cause serious performance degradation of communication, referred to as the coexistence problem. When coexistence problem occurs in smart medical system, reliable transmitting of patient's biological information may not be guaranteed and patient's life can be jeopardized. Therefore, coexistence problem in smart medical system should be resolved. In this paper, we propose a distributed coexistence mitigation scheme for IoT-based smart medical system which can dynamically avoid interference in coexistence situation and can guarantee reliable communication. To evaluate the performance of the proposed scheme, we perform extensive simulations by comparing with IEEE 802.15.4 MAC protocol which is a traditional low-power communication technology.