• Proceedings of the KIEE Conference
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• 1999.07c
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• pp.1262-1266
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• 1999

More precise operation and control is required to ensure the stability and security of modern large power systems that is a complicated and widely dispersed structure. To ensure the precise operation and control of modern power system, most of all, precise monitoring and measurement of the various state values of power system is required. This paper discusses phasor measurement unit using synchronization signals from the GPS satellite system- Synchronized Phasor Measurement Unit. Considering the power system operation state, the transmitting data format over modems is defined. To provide all available information, PMU process the measurements to generate three phase symmetrical component. This paper proposes the transmitted data format and implements the PMU model using EMTP/Models. The validity of proposed model is confirmed through several contingency on the simple power system.

• Journal of Power Electronics
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• v.13 no.5
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• pp.841-853
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• 2013

An application of doubly-fed induction generator (DFIG), which is one of adjustable speed generators, to a gas engine cogeneration system has been investigated. To operate during a blackout as an emergency power supply is one of important roles for the gas engine cogeneration system. However, the DFIG requires initial excitation for startup during a blackout because the DFIG has no excitation source. In this paper, we propose the "blackout start" as a new excitation method to generate a rated voltage at the primary side during a blackout. In addition, a stand-alone operation following a blackout has been investigated by using experimental setup with a real gas engine. Power flows in the generating set with the DFIG at the stand-alone operation have been investigated experimentally. Experimental investigation of the power flow suggests that the generating set with DFIG has optimal speed in minimizing whole system losses.

• The Transactions of The Korean Institute of Electrical Engineers
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• v.58 no.4
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• pp.671-678
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• 2009

This paper presents target operation voltage guidelines of each voltage control area considering both voltage stability and economical efficiency in real power system. EMS(Energy Management System) data, Real-time simulator, shows not only voltage level but lots of information about real power system. Also this paper performs optimal power flow calculation of three objective functions to propose the best target operation voltage. objective function of interchange power flow maximum and active power loss minimization stand for economical efficiency index and reactive power reserve maximum objective unction represents stability index. Then through simulation result using optimazation technique, the most effective objective function is chosen. To sum up, this paper divides voltage control area into twelve considering electric distance characteristics and estimate or voltage level by the passage of time of EMS peak data. And through optimization technique target operation voltage of each voltage control area is estimated and compare heir result. Then it is proposed that the best scenario to keep up voltage stability and maximize economical efficiency in real power system.

• The Transactions of The Korean Institute of Electrical Engineers
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• v.62 no.2
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• pp.149-154
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• 2013

Short term load forecasting for electric power demand is essential for stable power system operation and efficient power market operation. High accuracy of the short term load forecasting can keep the power system more stable and save the power market operation cost. We propose an optimal coefficient selection method for exponential smoothing model in short term load forecasting on weekdays. In order to find the optimal coefficient of exponential smoothing model, load forecasting errors are minimized for actual electric load demand data of last three years. The proposed method are verified by case studies for last three years from 2009 to 2011. The results of case studies show that the average percentage errors of the proposed load forecasting method are improved comparing with errors of the previous methods.

• The Transactions of the Korean Institute of Power Electronics
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• v.21 no.6
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• pp.497-505
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• 2016

Operating wind turbine generators at maximum power point requires maximum power point tracking (MPPT) control methods. However, conventional methods cannot track the appropriate maximum power point in situations involving wind turbine systems based on a series operation strategy. These systems comprise one or more local maximum power points, and conventional methods can detect only one local maximum power point closed by a current operation point. This study proposes an advanced MPPT method for the series operation strategy of a small, grid-connected wind turbine system. In determining the appropriate maximum point, operations at certain local maximum power points are analyzed. The results show one appropriate point, which is tracked by the proposed MPPT method. The effectiveness of the proposed method is verified by the experimental results.

• The Transactions of The Korean Institute of Electrical Engineers
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• v.57 no.10
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• pp.1726-1730
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• 2008

In this paper, the application schemes for coordinated control system of multiple FACTS were presented to enhance the voltage stability around the metropolitan areas. In order to coordinated control of FACTS devices, f-V analysis method which is one of the indices for voltage stability was performed with real time network data which is transferred from SCADA/EMS system. If the system is unstable after contingencies, the new operation set-point of FACTS would be determined using bus sensitivity from tangent vector at voltage instability point. Otherwise, we would determine the new operation set-point of FACTS for considering economical operation, like as active power loss minimization using Optimal Power Flow algorithm. In simulation, the SCADA/EMS 2007's data are used for studying the coordinated control algorithm of multiple FACTS devices that is installed or will be installed in KOREA power system

• Proceedings of the KIEE Conference
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• 2011.07a
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• pp.67-68
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• 2011

This paper analysed a protective equipment in power distribution system linked distribution power system when a superconducting fault current limiter(SFCL) is installed. This paper focused on a recloser, because the recloser is a general protective equipment. When power distribution system linked distribution power system, a fault current is increased by adding fault current of distribution power system. The increased fault current makes many problems. But SFCLs are limiting fault current and help the protective equipment to operate normal process. We analysed the operation of protective equipment in power distribution system linked distribution power system with SFCLs.

• Proceedings of the KIPE Conference
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• 1998.07a
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• pp.269-274
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• 1998

This paper describes a scaled model for PWM thyristor current-source inverter with a commutation circuit. The system consists of a 6-pulse thyristor bridge and an LC resonant circuit with thyristor switches, which offers thyristors to have turn-off capability for PWM operation with minimal switching losses. The proposed system can be used as a reactive power compensator with PWM operation for the utilitity application. There would be two advantages in the proposed system over the existing voltage source inverter. One is the low system cost due to using the conventional thyristors. Another is easy expansion of system operation voltage because th series operation of thyristor devices is already proven in HVDC system.

• The Transactions of The Korean Institute of Electrical Engineers
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• v.61 no.5
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• pp.664-668
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• 2012

This paper presents the operation strategy of KEPCO(Korea Electric Power COporation) ${\pm}80kV$ 60MW Bipole HVDC system that will be applied between Guemak C/S(converter station) and Hanlim C/S in Jeju island. Unlike intertie HVDC system, this system is located in AC power grid inside. Therefore, the enhancement of system security related with line flow and bus voltages can be major operation strategy. In this paper, in particular, the optimal operation algorithm in the abnormal(not steady state) power system is presented and simulated.

• Proceedings of the KIEE Conference
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• 2006.07a
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• pp.236-237
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• 2006

A microgrid is a new type of power system which is formed by the interconnection of small generator to distribution systems. Microgrids are able to supply electric power to their loads independently, which is called with islanding operation, even if they're separated from the power system. As a result, microgrids must be equipped with specific islanding detection schemes for the islanding operation of microgrids. This paper studies an islanding detection method considering reactive power. The proposed method is dealing with the reactive power of the cable which connects between a microgrid and a power system. To show the validity of the proposed method, many islanding operation cases are tested by varying the load conditions of microgrids.