• Journal of the Korea Institute of Information and Communication Engineering
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• v.16 no.11
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• pp.2365-2373
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• 2012

To obtain Korea AS-level internet topology, we used three data sources, which include BGP data of UCLA IRL, IRR and IXP data. Using Internet topology generator models(Waxman, BA and GLP), we developed three graphs that have same number of nodes as Korea AS-level Internet. Then we compared each graph with the Korea AS-level Internet topology. Through this study we could find that the existing Internet topology generators can't simulate Korea AS-level internet.

• Journal of international Conference on Electrical Machines and Systems
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• v.3 no.2
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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.

• Journal of international Conference on Electrical Machines and Systems
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• v.2 no.4
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• pp.466-472
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• 2013

The paper presents a novel DC grid connection topology and control strategy for doubly-fed induction generator (DFIG) based wind power generation system. In order to achieve the wind power conversion, the stator side converter and the rotor side converter is used to implement the DFIG control based on the indirect air-gap flux orientation, and a DC/DC converter is used for the DFIG system to DC grid connection. The maximum power point tracking and DC voltage droop control can also be implemented for the proposed DFIG system. Finally, a 4-terminal DFIG-based multi-terminal DC grid system is developed by Matlab to validate the availability of the proposed system and control strategy.

• Journal of the Korea Society for Simulation
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• v.13 no.3
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• pp.43-54
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• 2004

Studies of Internet algorithms or policies require experiments on the real large-scale networks. But practical problems with large real networks make them difficult. Instead many researchers use simulations on the Internet topology models. So, It is Important that study about topology model that reflect characteristic of the internet exactly. We propose new topology model which reflect of hierarchical network and addition, removal of nodes and accompanied change of topologies. In the modeling scheme for network generation, we applied DEVS formalism and analyzed the topologies generated by our algorithms.

• Proceedings of the KIEE Conference
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• 2011.07a
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• pp.872-873
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• 2011

This paper presents a multi-domain topology optimization using the harmonically excited coil and the iron in order to focus pulsed magnetic field (PMF). The design sensitivity of the harmonic magnetic field is derived by adjoint variable method. As a result of the optimization, PMF is considerably concentrated on the objective domain with much less leakage than the initial model.

• Proceedings of the KIEE Conference
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• 2011.07a
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• pp.981-982
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• 2011

This paper discusses design aspects of slotless permanent magnet generator for high performance and low speed applications. The airgap flux density in was obtained from finite element analysis and the design of a PM generator. The relatively large diameter stator laminations of such machines tend, therefore, to have a very thin back of core and narrow teeth, which make them expensive and difficult to manufacture. this thesis proposes an alternative PM generator topology featuring a slotless stator whose laminations are manufactured from a split core. The test results with a resistive load confirm the satisfactory operation of generator.

• The Transactions of the Korean Institute of Electrical Engineers P
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• v.64 no.3
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• pp.104-110
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• 2015

This paper describes a power quality disturbance generator for the test of a microgrid. The generator provides phase-angle jump as well as voltage sag with simple structure. The main components of the generator are SCR thyristors and transformers, therefore, high reliability and high efficiency can be obtained without switching losses. The operating principle of the proposed scheme is described and the voltage and current characteristics in case of voltage sag with phase-angle jump is analyzed. The usefulness of the proposed topology is verified through simulations and experimental results.

• The Transactions of The Korean Institute of Electrical Engineers
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• v.62 no.8
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• pp.1108-1114
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• 2013

This paper presents a new winding topology for MW class offshore wind generator having modular and dual 3-phase. Based on proposed simplified relationship between magnetic flux and phase current in the air gap, several new windings for modular and dual 3-phase are made. In case of one inverter operation or faulty operation, the proposed model can have balanced 3-phase induced voltage whereas the conventional generator with modular winding has unbalanced induced voltage, which can be important issue in offshore generator. The model was applied into 6MW prototype machine with dual 3-phase. Using finite element analysis, induced voltage, inductance were investigated. The results show that the proposed modular winding can be applicable to dual inverter system with electrically balanced voltage.

• Proceedings of the KIPE Conference
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• 2001.10a
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• pp.295-300
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• 2001

A variety of high voltage DC power supplies employing the high frequency inverter are difficult to achieve soft switching considering a quick response and no overshoot response under the wide load variation ranges which are used in medical-use x-ray high voltage generator from 20kV to 150kV in the output voltage and from 0.5mA to 1250mA, respectively. The authors develops soft switching high voltage DC power supply designed for x-ray power generator applications, which uses series resonant inverter circuit topology with a multistage voltage multiplier instead of a conventional high voltage diode rectifier connected to the second-side of a high-voltage transformer with a large turn ratio. A constant on-time dual mode frequency control scheme operating under a principle of zero-current soft switching commutation is described. Introducing the multistage voltage multiplier, the secondary transformer turn-numbers and stray capacitance of high-voltage transformer is effective to be greatly reduced. It is proved that the proposed high-voltage converter topology with dual mode frequency modulation mode control scheme is able to be the transient response and steady-state performance in high-voltage x-ray tube load. The effectiveness of this high voltage converter is evaluated and discussed on the basis of simulation analysis and observed data in experiment.

• Journal of Power Electronics
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• v.16 no.4
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• pp.1455-1468
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• 2016

This paper presents a grid-connected dual stator-winding induction generator (DWIG) wind power system suitable for wide wind speed ranges. The parallel connection via a unidirectional diode between dc buses of both stator-winding sides is employed in this DWIG system, which can output a high dc voltage over wide wind speed ranges. Grid-connected inverters (GCIs) do not require booster converters; hence, the efficiency of wind energy utilization increases, and the hardware topology and control strategy of GCIs are simplified. In view of the particularities of the parallel topology and the adopted generator control strategy, we propose a novel excitation-capacitor optimization solution to reduce the volume and weight of the static excitation controller. When this excitation-capacitor optimization is carried out, the maximum power tracking problem is also considered. All the problems are resolved with the combined control of the DWIG and GCI. Experimental results on the platform of a 37 kW/600 V prototype show that the proposed DWIG wind power system can output a constant dc voltage over wide rotor speed ranges for grid-connected operations and that the proposed excitation optimization scheme is effective.