• KIEE International Transaction on Electrical Machinery and Energy Conversion Systems
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• v.2B no.3
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• pp.109-114
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• 2002

This paper analysis the transient performance of the modified excitation system using 4-quadrant chopper for a synchronous machine connected to HVDC system. Conventionally, capacitors are used to supply reactive power requirement at a strong converter bus. And the installation of a synchronous machine is essential in an isolated weak network to re-start after a shutdown of HVDC and to increase the system strength. However, a conventional static excitation system has some problems which are harmonic instability and the system stress due to overvoltage. To reduce these problems, the new excitation system, which has 4-quadrant chopper, is proposed. As the proposed system provides the capability to allow reverse current and isolate between AC network and excitation power, problems of overvoltage and harmonic instability can be solved. The investigation is performed and confirmed by the time domain digital simulation using PSCAD/EMTDC program.

• Journal of Intelligence and Information Systems
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• v.9 no.3
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• pp.1-21
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• 2003

In this research, we developed a Multi-Agent based Negotiation Support System to be able to increase the competitive power of a company in dynamic environment and correspond to various orders of customers by diffusion of electronic commerce. The system uses the agent technology that is being embossed as new paradigm in dynamic environment and flexible system framework. The multi-agent technology is used to solve these problems through cooperation of agent. The system consists of six sub agents: Mediator, manufacturability Analysis Agent, Process Planning Agent, Scheduling Agent, Selection Agent, Negotiation-strategy Building Agent. In this paper, the proposed Multi-Agent based Negotiation Support System takes aim at the automation of transaction process from ordering to manufacturing plan through the automation of negotiation that is the most important in order-taking transaction.

• KIEE International Transaction on Electrical Machinery and Energy Conversion Systems
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• v.5B no.4
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• pp.374-381
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• 2005

The ability to provide quality power has become a significant issue in power systems. The main causes of poor power quality are harmonic currents, poor power factor, supply-voltage variations, etc. A technique of achieving both active current distortion compensation, power factor correction and also mitigating the supply-voltage variation (sag or swell) at the load side is presented in this paper. The operation and rating issues of the proposed Single-phase Unified Power Quality Conditioner are also highlighted. To reduce the total cost while simultaneously increasing the performance, the system is fully digitally controlled using the fixed-point TMS320F240 digital signal processor. The performances of the UPQC, which is composed by shunt and series PWM controlled-converters, have been verified on a laboratory prototype.

• The Transactions of The Korean Institute of Electrical Engineers
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• v.56 no.10
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• pp.1721-1730
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• 2007

SThis paper proposes a new dispatch scheduling algorithm in interconnected regional system operations. The dispatch scheduling formulated as mixed integer non-linear programming (MINLP) problem can efficiently be computed by generalized Benders decomposition (GBD) algorithm. GBD guarantees adequate computation speed and solution convergency since it decomposes a primal problem into a master problem and subproblems for simplicity. In addition, the inter-temporal optimal power flow (OPF) subproblem of the dispatch scheduling problem is comprised of various variables and constraints considering time-continuity and it makes the inter-temporal OPF complex due to increased dimensions of the optimization problem. In this paper, regional decomposition technique based on auxiliary problem principle (APP) algorithm is introduced to obtain efficient inter-temporal OPF solution through the parallel implementation. In addition, it can find the most economic dispatch schedule incorporating power transaction without private information open. Therefore, it can be expanded as an efficient dispatch scheduling model for interconnected system operation.

• The Transactions of the Korean Institute of Electrical Engineers A
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• v.51 no.4
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• pp.196-201
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• 2002

An important aspect of the study of power system markets involves the assessment of strategic behavior of participants for maximizing their profits. In models for imperfect competition of a deregulated system, the key tack is to find the Nash equilibrium. When the constraints are not considered in the power market, the equilibrium has the form of a pure strategy. However, the constraints are considered, the equilibrium has the form of a mired strategy. In this paper the bimatrix game approach leer finding a mixed equilibrium is analyzed. The Nash equilibrium of a mixed strategy will be used adequately for the analysis of market power.

• KIEE International Transaction on Electrical Machinery and Energy Conversion Systems
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• v.5B no.1
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• pp.57-62
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• 2005

Grid-connected photovoltaic (PV) systems were installed and monitored at the field demonstration test center (FDTC) in Korea in October 2002. Before long-term field testing of installed PV systems, the performances of PV components were evaluated and compared through short-term performance tests of each of the PV system components such as power conditioning system and PV module under standard test conditions. A data acquisition system has been constructed for measuring and analyzing the performance of PV systems to observe the overall effect of environmental conditions on their operation characteristics. Performances of PV systems have been evaluated and analyzed not only for component perspective (PV array, power conditioning unit) but also for global perspective (system efficiency, capacity factor, electrical power energy) by review of the field test and loss factors of the systems. These results indicate that it is highly imperative to develop an optimum design technology of grid connected PV systems. The objective of this paper is not only to evaluate and analyze the performance of domestic PV systems application through long-term field testing at FDTC but also to develop evaluation, analysis and optimum technology for long-term stability and reliability of grid-connected PV systems in Korea.

• Proceedings of the KIEE Conference
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• 2008.07a
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• pp.580-583
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• 2008

As the construction of renewable energy generators is on the rise and gets bigger in size, researchers pay more and more attention to the impact of such facilities on the power market as well as on the stability of power grid system. In Korea, while studies on the latter, including calculating the marginal capacity of renewable energy generators, is being made, those on the former has not yet been performed. As such, this paper analyses the impact of a big renewable energy generators on the price and transaction cost of domestic power market and proposes ideas to minimize such influence by applying the technology of forecasting renewable energy.

• KIEE International Transaction on Electrical Machinery and Energy Conversion Systems
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• v.11B no.3
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• pp.104-111
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• 2001

The design procedures and experimental results of a single-stage electronic ballast using half-bridge resonant inverter are presented in this paper. The proposed topology is based on a single-stage ballast which combines a boost converter and a half-bradge series resonant inverter. High power factor is achieved by using the boost semi-stage operating in discontinuous conduction mode and inverter semi-stage operated above resonant frequency to provide zero voltage switching is empolyed to ballast the fluorescent lamp Experimental results from the ballast system with 36W fluorescent

• KIEE International Transaction on Electrical Machinery and Energy Conversion Systems
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• v.2B no.4
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• pp.207-213
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• 2002

The paper introduces a switched reluctance motor drive system based on an 80C31 and an Intel 80C 196KB single-chip microprocessor control. Advance schemes are used in turn-on and turn-off angles with the power converter's main switches during traction and regenerative braking. The principles of traction speed control and braking torque control are given. The hardware and software patterns in the 80c31 and the Intel 80C196KB single-chip microprocessor control system are also presented.

• Journal of Korea Multimedia Society
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• v.14 no.1
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• pp.103-111
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• 2011

Legacy Java card which adapts a Java platform loads and executes an application when electronics power is provided. However, recently the most Java cards are embedded into a mobile terminal as USIM cards, therefore the power is continually provided for the smart cards. In this case, operation of a Java card system needs to consider its operating system to be advanced in memory management, object management and transaction mechanism. In this paper, we present a high performance Java Card system which is able to have efficient installation, loading and execution of application by applying a new memory management of the smart card that has safe power system.