• Journal of Power Electronics
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• v.10 no.1
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• pp.97-105
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• 2010

This paper presents the modeling, control and simulation of an interconnection system (ICS) of cascaded distributed generation (DG) modules for both grid-tied and stand-alone operations. The overall configuration of the interconnection system is given. The interconnection system consists of a cascaded DC/DC boost converters and a DC/AC inverter. Detailed modeling of the interconnection system incorporating a cascaded architecture has not been considered in previous research. In this paper, suitable control systems for the cascaded architecture of power electronic converters in an interconnection system have been studied and modeled in detail. A novel control system for DC/DC boost converters is presented based on a droop voltage controller. Also, a novel control strategy for DC/AC inverters based on the average large signal model to control the aggregated DG modules under both grid-tied and stand-alone modes is demonstrated. Simulation results indicate the effectiveness of the proposed control systems.

• The Transactions of the Korean Institute of Power Electronics
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• v.21 no.5
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• pp.404-410
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• 2016

To avoid the stability issues of LLCL filters, passive or active damping methods to eliminate the resonance phenomena are required. In this paper, system stability of a current control is analyzed when the active damping scheme based on the virtual resister is utilized in single-phase grid converter systems with LLCL input filters. The control performance according to the parameters of the virtual resistance is investigated. The validity of stability analysis was verified by simulation and experimental results.

• Proceedings of the KIPE Conference
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• 2015.07a
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• pp.177-178
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• 2015

This paper presents a neutral point deviation compensating control algorithm applied to a 3-level NPC converter. The neutral point deviation is analyzed with a focus on the current flowing out of or into the neutral point of the dc link. Based on the zero sequence components of the reference voltages, this paper analyzes the neutral point deviation and balancing control for 3-level NPC converter. An analytical method is proposed to calculate the injected zero sequence voltage for NP balancing based on average neutral current. This paper also proposes a control scheme compensating for the neutral point deviation under generalized unbalanced grid operating conditions. The positive and negative sequence components of the pole voltages and ac input currents are employed to accurately explain the behavior of 3-level NPC converter. Simulation and experimental results for a test set up of 30kW are shown to verify the validity of the proposed algorithm.

• ETRI Journal
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• v.37 no.1
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• pp.197-202
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• 2015

A smart grid is a modernized electrical grid that uses information about the behaviors of suppliers and consumers in an automated fashion to improve the efficiency, reliability, economics, and sustainability of the production and distribution of electricity. In the operation of a smart grid, demand side management (DSM) plays an important role in allowing customers to make informed decisions regarding their energy consumption. In addition, it helps energy providers reduce peak load demand and reshapes the load profile. In this paper, we propose a new DSM scheduling scheme that makes use of the day-ahead pricing strategy. Based on the Rubinstein-Stahl bargaining model, our pricing strategy allows consumers to make informed decisions regarding their power consumption, while reducing the peak-to-average ratio. With a simulation study, it is demonstrated that the proposed scheme can increase the sustainability of a smart grid and reduce overall operational costs.

• The Transactions of The Korean Institute of Electrical Engineers
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• v.62 no.8
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• pp.1059-1065
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• 2013

Doubly Fed Induction Generator(DFIG) systems occupy the largest proportion of worldwide wind energy generation market. DFIG systems are very sensitive to grid disturbances especially to voltage dips due to the structure of the stator connected to grid. In the past, when a grid fault occurs generators are separated from grid(trip method) in order to protect the systems. Nowadays, due to the growing penetration level of wind power, many countries have made some requirements that wind turbines are required to have Low Voltage Ride Through(LVRT) capability during grid faults. In this paper, a flux tracking LVRT control strategy based on system modeling equations is proposed. The validity of the proposed strategy is verified through computer simulations.

• 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.

• Proceedings of the KIEE Conference
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• 2011.07a
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• pp.706-707
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• 2011

The insertion of the crowbar system in the doubly fed induction generator rotor circuit for a short period of time during grid disturbance enables a more efficient way of limiting transient rotor current and hence protecting the rotor side converter (RSC) and the DC - link capacitor. When crowbar is activated at fault occurrence and clearance time, RSC is blocked while DC -link capacitor and the grid side converter (GSC) can be controlled to provide reactive power support at the PCC and improve the voltage which helps to comply with grid codes. In this paper, control strategies for crowbar system to limit the rotor current during fault is presented with RSC and GSC controllers are modified to control PCC voltage during disturbance to enhance DFIG wind farm to comply with some strict grid codes. Model simulated on MATLAB/Simulink verify the study through simulation results presented.

• Journal of Power Electronics
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• v.19 no.2
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• pp.591-601
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• 2019

With the development of renewable energy, grid-connected inverter technology has become an important research area. When compared with traditional silicon IGBT power devices, the silicon carbide (SiC) MOSFET shows obvious advantages in terms of its high-power density, low power loss and high-efficiency power supply system. It is suggested that this technology is highly suitable for three-phase AC motors, renewable energy vehicles, aerospace and military power supplies, etc. This paper focuses on the SiC MOSFET behaviors that concern the parasitic component influence throughout the whole working process, which is based on a three-phase grid-connected inverter. A high-speed model of power switch devices is built and theoretically analyzed. Then the power loss is determined through experimental validation.

• The Transactions of the Korean Institute of Power Electronics
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• v.26 no.5
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• pp.334-341
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• 2021

Operation modes and control strategies for single-phase mobility charging station utilizing photovoltaic (PV) generation and energy storage systems (ESS) are proposed. This approach generates electric power from PV to transmit the mobility, ESS, and then transfer it to the grid when surplus electric power is generated during daytime. However, the PV power cannot be generated during night-time, and ESS and the mobility system can be charged using grid power. The power balance control based on power fluctuations and the resonant current control that can compensate harmonic components have been added to increase the stability of the system. The MATLAB/Simulink simulation was carried out to verify the proposed control method, and the 2-kW single-phase grid-tied PV-ESS smart mobility charger was built and tested.

• Journal of KIISE:Computer Systems and Theory
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• v.35 no.9_10
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• pp.452-465
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• 2008

This paper proposes a light-weight, seamless integrated access control for global e-Science resource sharing. E-Science, based on Grid Computing, was designed to help scientists to remotely control and process the Grid resources such as high-end equipments and remote machines. As many researchers engage in the e-Science Grids, the researchers in a grid often have to wait for or give up use of the Grid resources, even when there are idle resources in other Grids. In this case, provided that proper compensation is given, Grid resource sharing is helpful both for the researchers and the Grids which provide their resources. But, sharing Grid resources globally is not simple, as each e-Science Grid is especially designed for resource sharing in its Virtual Organization(VO) and already has its unique access control policy for its resources. This paper proposes a new integrated access control for e-Science Grid resource sharing. The access control is light-weight without any priori service level agreement(SLA)s among the Grids which share their resources and seamless because the users can use the resources shared as the ones belonging to their Grids without their additional registration to the other Grids.