• Journal of Electrical Engineering and Technology
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• v.12 no.4
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• pp.1586-1592
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• 2017

Voltage sourced converter (VSC) based direct-current (DC) grid has the ability to control power flow flexibly and securely, thus it has become one of the most valid approaches in aspect of large-scale renewable power generation, oceanic island power supply and new urban grid construction. To solve the optimal power flow (OPF) problem in DC grid, an adaptive particle swarm optimization (PSO) algorithm based on fuzzy control theory is proposed in this paper, and the optimal operation considering both power loss and voltage quality is realized. Firstly, the fuzzy membership curve is used to transform two objectives into one, the fitness value of latest step is introduced as input of fuzzy controller to adjust the controlling parameters of PSO dynamically. The proposed strategy was applied in solving the power flow issue in six terminals DC grid model, and corresponding results are presented to verify the effectiveness and feasibility of proposed algorithm.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2010.06a
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• pp.51-51
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• 2010

We have proposed a new configuration for the improvement of neutron yield without the application of external ion sources in an inertial electrostatic confinement (IEC) device. The application of a double grid cathode to the IEC device is expected to generate a higher ion current than a single grid cathode. This paper verifies the effect of the double grid cathode by both fluid and particle simulation. Through the fluid simulation the optimal shape and applied voltage of the double grid cathode is determined, and through the particle simulation the usefulness of that is confirmed.

• The Transactions of The Korean Institute of Electrical Engineers
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• v.60 no.7
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• pp.1347-1353
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• 2011

While most of the existing protection schemes have been designed with local information around individual components, these local schemes are not considered capable of protecting the modern electric power gird with growing complexity. Recent blackouts in North America and Europe have renewed the emphasis on coordinated protection and control actions to avoid systemwide blackouts, utilizing all of the available grid information. Thus, this paper proposes a new methodology, Agent-based Colored Petri Net (ACPN) modeling for systematically representing, modeling and analyzing information flows and interactions among the entities of the electric power grid. The paper demonstrates its efficacy and accuracy by investigating an ACPN model of a wide area protection system for a typical power grid. The proposed modeling and analysis schemes may further provide a framework to help assure reliability and interoperability of diverse smart grid components.

• The Transactions of The Korean Institute of Electrical Engineers
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• v.60 no.2
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• pp.416-422
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• 2011

Smart grid is the next generation intelligent power grid that combines the existing electric power infrastructure and information infrastructure. It can optimize the energy efficiency in both directions, suppliers and power consumers to exchange information in real time. In smart grid environments, with existing network security threats due to the smart grid characteristics, there are additional security threats. In this paper, we propose a security mechanism that provides mutual authentication and key agreement between a remote user and the device. The proposed mechanism has some advantages that provides secure mutual authentication and key agreement and secure against a replay attack and impersonation attacks.

• The Transactions of The Korean Institute of Electrical Engineers
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• v.58 no.11
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• pp.2175-2184
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• 2009

This paper describes operational analysis results of the DC micro-grid using detailed model of distributed generation. Detailed model of wind power generation, photo-voltaic generation, fuel-cell generation was implemented with the user-defined model of PSCAD/EMTDC software that is coded with C-language. The operation analysis was carried out using PSCAD/EMTDC software, in which the power circuit is implemented by built-in model and the controller is modelled by user-defined model that is also coded with C-language. Various simulation results confirm that the DC micro-grid can operate without any problem in both the interconnected mode and the islanded mode. The operation analysis result confirms that the DC micro-grid make it feasible to provide power to the load stably. And it can be utilize to develop the actual system design and building.

• The Transactions of the Korean Institute of Power Electronics
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• v.23 no.6
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• pp.373-380
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• 2018

This study proposes a new islanding detection method that uses the phase shift of feed-forward voltage and evaluates the performance of an existing method and the proposed method when the grid frequency changes within the allowable range under steady-state conditions. The investigated existing method, which is slip mode frequency shift (SMS), uses current phase shift to detect islanding. The SMS method supplies reactive current to the grid under this condition, but the proposed method does not generate additional reactive power because it does not depend on the current control loop. The performance in steady-state grid condition is evaluated through simulations and experiments.

• The Transactions of the Korean Institute of Power Electronics
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• v.24 no.5
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• pp.349-355
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• 2019

A grid-connected inverter with critical loads should be able to supply a stable voltage to critical loads at mode change and during clearing time while detecting unintentional islanding. This study proposes a mode transfer method for a grid-connected inverter with critical loads. The proposed method, which integrates the grid-connected and islanded mode control loops into one control block, provides an autonomous and seamless mode transfer from the current control to the voltage control. Therefore, the proposed scheme can supply a stable voltage to critical loads at mode change and during clearing time. Experimental results are provided to validate the proposed method.

• The Transactions of the Korean Institute of Power Electronics
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• v.28 no.1
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• pp.1-7
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• 2023

A grid-connected 3-level NPC inverter is a power conversion device that connects renewable energy generators, such as photovoltaic or wind turbines to the grid. Although many studies have focused on this inverter, commercializing it requires strictly satisfying various safety and power quality-related standards. Among many standards, leakage current and grid current total harmonic distortion(THD) can be affected by external factors such as installation environment, aging, and grid conditions. Hence, inverter operations that can satisfy these standards need to be explored. In this study a 3-level NPC inverter operation algorithm using the Phase Opposition Disposition-PWM method that can effectively reduce leakage current and switching frequency adjustment to reduce THD effectively has been proposed.

• Proceedings of the KIEE Conference
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• summer
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• pp.120-122
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• 2004

This paper analyse impacts of Community Energy System (CES) on the grid during transition periods for integrating of the CES and the grid. In the near future, CES might be one of major energy supply structures. The basic concept of CES is that it supplies electrical and thermal energy to the local customer loads through the islanded power network separated from the grid. Therefore, the interconnection with the grid occurs only when the energy supply from the CES generators does not meet the demand of the local load. For avoiding impacting the grid during the transition operation modes of CES, it is necessary to thoroughly analyse the influences on the grid during those periods. In order to show them, in this paper, we model the CES with 2.34 WVA DG and simulate the impacts on the grid due to interconnection of CES The simulation results show that, in order to reduce bad influences of CES on the grid, CES need the efficient load management and generation control schemes during the transition periods.

• The Transactions of The Korean Institute of Electrical Engineers
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• v.56 no.2
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• pp.317-324
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• 2007

Most conventional hybrid systems using renewable energy sources have been applied for stand-alone operation, but Utility-interface may be an useful and viable option for hybrid systems. Grid-connected operation may have benefits such as reduced losses in power system distribution, utility support in demand side management, and peak load shaving. This paper addresses power control and dynamic performance of a grid-connected PV/wind/BESS hybrid system. At all times the PV way and the wind turbine are individually controlled to generate the maximum energy from given weather conditions. The battery energy storage system (BESS) charges or discharges the battery depending on energy gap between grid invertger generation and production from the PV and wind system. The BESS should be also controlled without too frequently repeated shifts in operation mode, charging or discharging. The grid inverter regulates the generated power injection into the grid. Different control schemes of the grid inverter are presented for different operation modes, which include normal operation, power dispatching, and power smoothing. Simulation results demonstrate that the effectiveness of the proposed power control schemes for the grid-interactive hybrid system.