• 대한전기학회:학술대회논문집
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• 대한전기학회 2007년도 제38회 하계학술대회
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• pp.487-488
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• 2007

Fault section detection and service restoration is very important in ungrounded distribution system. Techniques currently used to track down faults are time consuming and cumbersome. A new scheme is developed based on communication technology, and the simulation result shows that the method can satisfy the requirement proposed.

• Journal of international Conference on Electrical Machines and Systems
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• 제3권2호
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• pp.215-221
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• 2014

To satisfy the high voltage direct current (HVDC) grid connection demand for wind power generation system, a novel topology and control strategy of HVDC grid connection for open-winding permanent magnet synchronous generator (PMSG) based wind power generation system is proposed, in which two generator-side converter and two isolated DC/DC converters are used to transmit the wind energy captured by open winding PMSG to HVDC grid. By deducing the mathematic model of open winding PMSG, the vector control technique, position sensorless operation, and space vector modulation strategy is applied to implement the stable generation operation of PMSG. Finally, the simulation model based on MATLAB is built to validate the availability of the proposed control strategy.

• 전기학회논문지P
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• 제51권4호
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• pp.169-174
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• 2002

The developments of the solar and the wind power energy are neccessary since the future alternative energies that have no pollution and no limitation are restricted. Currently power generation system of existing problems, combined generation system of photovoltaic(400W) and wind power generation system(400W) was suggested. It combines wind power and solar energy to have the supporting effect from each other. However, weather condition, power compensation device that uses elastic energy of spiral spring to combined generation system was also added for the present study. In an experiment, when output of system gets lower than 12V(charging voltage), power was continuously supplied to load through the inverter by charging energy obtained from generating rotary energy of spiral spring operates in small scale generator.

• Journal of international Conference on Electrical Machines and Systems
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• 제1권4호
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• pp.425-433
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• 2012

As the demand for electric power increases rapidly and the amount of fossil fuels decreases year by year, making use of renewable resources seem very necessary. However, due to the discontinuous nature of renewable resources and the hierarchical topology of existing grids, power quality and grid stability will deteriorate as more and more distributed generations (DGs) are connected to the grids. It is a good idea to combine local utilization, local consumption, energy storage and DGs to form a grid-friendly micro grid, these micro grids can then assembled into an intelligent power system - the smart Grid. It can optimize power flow and integrate power generation and consumption effectively. Most importantly, the power quality and grid stability can be improved greatly. This paper depicts how the smart grid addresses the current issues of a power system. It also figures out the key technologies and expectations of the smart grid.

• KIEE International Transaction on Electrical Machinery and Energy Conversion Systems
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• 제3B권2호
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• pp.103-110
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• 2003

With significant development of power electronics technology, the proliferation of nonlinear loads such as static power converters has deteriorated power quality in power transmission and distribution systems. Notably, voltage harmonics resulting from current harmonics produced by the nonlinear loads have become a serious problem in many countries. Many photovoltaic power generation systems installed in building systems have harmonics that are the worst object for distribution systems as a utility interactive system, and it tends to spread out continuously. Proposed and implemented in this paper is a multi-function inverter control strategy that allows a shunt active filter function to the power inverter of the photovoltaic power generation system established on a building system. The effectiveness of the proposed system is demonstrated through the simulation of a hypothetical power system using PSCAD/EMTDC.

• KIEE International Transactions on Power Engineering
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• 제5A권3호
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• pp.252-259
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• 2005

Various problems such as increase of power loss and voltage instability may often occur in the case of low load power factor. The demand of reactive power increases continuously with the growth of active power and restructuring of electric power companies makes the comprehensive management of reactive power a troublesome problem, so that the systematic control of load power factor is required. In this paper, the load power factor sensitivity of generation cost is derived and it is used for effectively determining the locations of reactive power compensation devices and for enhancing the load power factor appropriately. In addition, voltage variation penalty cost is introduced and integrated costs including voltage variation penalty cost are used for determining the value of load power factor from the point of view of economic investment and voltage regulation. It is shown through application to a large-scale power system that the load power factor can be enhanced effectively using the load power factor sensitivity and the integrated cost.

• 전기학회논문지
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• 제63권10호
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• pp.1423-1427
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• 2014

Quantity of the solar power generation is heavily influenced by weather. In other words, due to difference in insolation, different quantity may be generated. However, it does not mean all areas with identical insolation produces same quantity because of various environmental aspects. Additionally, geographic factors such as altitude, height of plant may have an impact on the quantity. Hence, through this research, we designed a system to predict efficiency of the solar power generation system by applying insolation, weather factor such as duration of sunshine, cloudiness parameter and location. By applying insolation, weather data that are collected from various places, we established a system that fits with our nation. Apart from, we produced a geographic model equation through utilizing generated data installed nationwide. To design a prediction model that integrates two factors, we apply fuzzy algorithm, and validate the performance of system by establishing simulation system.

• Journal of Electrical Engineering and Technology
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• 제10권5호
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• pp.1983-1988
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• 2015

This paper proposes the enhanced application of superconducting magnetic energy storage (SMES) for the effective compensation of power fluctuations based on the interleaving technique. With increases in demand for renewable energy based photovoltaic (PV) generation system, the output power fluctuations from PV generation system due to sudden changes in environmental conditions can cause serious problems such as grid voltage and frequency variations. To solve this problem, the SMES system is applied with its superior characteristics with respect to high power density, fast response for charge and discharge operations, system efficiency, etc. In particular, the compensation capability is effectively improved by the proposed interleaving technique based on its parallel structure. The dynamic performance of the system designed using the proposed method is evaluated with several case studies through time-domain simulations.

• 전기학회논문지
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• 제62권5호
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• pp.596-603
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• 2013

The increase of distributed power generation is closely related to interest in microgird including renuable energy sources such as photovoltaic (PV) systems and fuel cell. By the growing interest of microgrid all over the world, many studies on microgrid operation are being carried out. Especially operation technique which is core technology of microgrid is to supply heat and electricity energy simultaneously. Optimal microgrid scheduling can be established by considering CHP (Combined Heat and Power) generation because it produce both heat and electricity energy and its total efficiency is high. For this reason, CHP generation in microgrid is being spotlighted. In the near future, wide application of microgrid is also anticipated. This paper proposes a mathematical model for optimal operation of microgrid considering both heat and power. To validate the proposed model, the case study is performed and its results are analyzed.

• Journal of Electrical Engineering and Technology
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• 제9권4호
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• pp.1202-1209
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• 2014

A novel integrated optimization method is proposed to combine both generation and transmission line expansion problem considering bus voltage limit. Most of the existing researches on the combined generation and transmission expansion planning cannot consider bus voltages and reactive power flow limits because they are mostly based on the DC power flow model. In this paper the AC power flow model and nonlinear constraints related to reactive power are simplified and modified to improve the computation time and convergence. The proposed method has been successfully applied to Garver's six-bus system which is one of the most frequently used small scale sample systems to verify the transmission expansion method.