• The Transactions of the Korean Institute of Electrical Engineers P
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• v.67 no.1
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• pp.1-8
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• 2018

ACL and DCL are have been conventionally used for reducing harmonic current on the input side of an ACMD. The current distortion ratio ITHD using ACL and DCL is only 35% to 85%, therefore to satisfy the IEEE Std. 519 requirements, the line filters has been focused as an alternative means. Those are installed between the AC power supply and the input of the ACMD, and must meet the IEEE Std. 519, be economical and be compact. To contribute to the widespread of using these line filters, we discussed concerning its topologies, simulation results, prototype test results as well as the cost evaluations. It included not only the proposed (NHHF) new hybrid harmonic filters which have both merits of simplicity and economic but also the past (BBHF) broadband harmonic filters and (HHF) hybrid harmonic filters.

• Journal of Electrical Engineering and Technology
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• v.13 no.2
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• pp.711-721
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• 2018

This paper presents a single-phase asymmetric half-bridge cascaded multilevel inverter based series active power filter (SAPF) for harmonic voltage compensation. The effect of level number on performance of the proposed SAPF is examined in terms of total harmonic distortion (THD) and system efficiency. Besides, the relationship between the level number and the number of switching device are compared with the other multilevel inverter topologies used in APF applications. The paper is also aimed to demonstrate the capability of the SAPF for compensating harmonic voltages alone, without using a passive power filter (PPF). To obtain the required output voltage, a new switching algorithm is developed. The proposed SAPF with levels of 7, 15 and 31 is used in both simulation and experimental studies and the harmonic voltages of the load connected to the point of common coupling (PCC) is compensated under two different loading conditions. Furthermore, very high system efficiency values such as 98.74% and 96.84% are measured in the experimental studies and all THD values are brought into compliance with the IEEE-519 Standard. As a result, by increasing the level number of the inverter, lower THD values can be obtained even under high harmonic distortion levels while system efficiency almost remains the same.

• Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
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• v.19 no.5
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• pp.23-29
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• 2005

The increasing use of nonlinear loads has resulted in an increase in the harmonic content of the load current for power transformers. Transformers subject to harmonic currents have higher losses and need to be derated. This paper presents a simple method for determining the capability of transformers to supply harmonic load currents and shows that the application of capacitor banks with a series connected reactor and harmonic filters will greatly increase the capability of transformers.. The EDSA program was used as a simulation tool for the case study.

• Proceedings of the KIEE Conference
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• summer
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• pp.48-50
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• 2004

The energization of high voltage transmission lines and transformers, that is an inevitable process in most countries as the first restorative action for wide-area blackout, may induce overvoltages such as sustained overvoltage, transient overvoltage and harmonic resonant overvoltage. And these may cause damages to power system equipments or failure of surge arresters. The harmonic resonant overvoltage originates in switching operations and nonlinear characteristics of equipments. Actually it is difficult to predict the occurrence of harmonic overvoltage, since they result from nonlinear characteristics of transformers and other equipments. This paper describes the analysis of domestic primary restorative transmission system using PSCAD/EMTDC. The harmonic resonance is verified and the solution to prevent harmonic resonance is proposed in this paper. As a result, the PSCAD/EMTBC simulation showed slightly conflictive results that had been presented by IEEE Power System Restoration Working Group report.

• Journal of the Korea Institute of Military Science and Technology
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• v.5 no.4
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• pp.81-87
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• 2002

In this paper, the transonic aeroelastic behavior of the generic fighter model is investigated in the time domain. The simulation of flutter flight test using forced harmonic motion of control surfaces including inertial coupling effects is conducted at the various conditions. The nonlinear aerodynamic effects are considered using a transonic small disturbance equation. A modal model obtained by a free vibration analysis is used for the structural model. The relations between the computed flutter boundary and the simulation results of the responses using the harmonic motions of control surfaces at various conditions are investigated.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2001.05a
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• pp.924-929
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• 2001

The flying height of contact slider is determined by vertical and pitching motions of slider. This paper performed the computer simulation for flying height change of contact slider. It is changed by many parameters, contact stiffness, contact damping, air bearing stiffness ratio, a location of mass center, and so on. Computer simulation is performed for knowing for what change of these parameters influences in flying height of contact slider. Disk surface is modeled in harmonic wave with from 10㎑ to 600㎑. Tri-pad slider is modeled in that contact slider has 2-DOF motion (vertical motion, pitching motion). Tri-pad contact slider is analyzed by numerical analysis method in computer simulation.

• Proceedings of the Earthquake Engineering Society of Korea Conference
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• 1997.10a
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• pp.159-166
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• 1997

The purpose of this thesis is to derive a theoretical model of the hysteretic resistance of the visco-elastic damper based on test results of harmonic excitation and to investigate of the basis of theory and experiment the effect of vibration control and response characteristics of portal frames degree vibration systems provided with the damper. The behaviour of a visco-elastic degree under dynamic loading is idealized by a model of the theory of visco-elasticity, i.e. a four-parameter model formed as a parallel combination of Maxwell fluid and Kelvin-Voigh models and its constitutive equation is derived. The model parameters are determined for a tested damper from the datas of harmonic excitation tests. The theoretical model of the damper is incorporated in equation fo motion of single degree of freedom. A computer program for solving the equation is written using Runge-kuttas's numerical integration scheme. Using this analysis program test cases of the earthquake excitation are simulated and the results of the simulation are the results of the simulation are the results of the simulation are compared with the test results.

• The Bulletin of The Korean Astronomical Society
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• v.44 no.2
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• pp.70.1-70.1
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• 2019

Multiple-harmonic electron cyclotron emissions, often known in the literature as the (n + 1∕2)fce emissions, are a common occurrence in the magnetosphere. These emissions are often interpreted in terms of the Bernstein mode instability driven by the electron loss cone velocity distribution function. Alternatively, they can be interpreted as quasi-thermal emission of electrostatic fluctuations in magnetized plasmas. The present paper carries out a one-dimensional relativistic electromagnetic particle-in-cell simulation and also employs a reduced quasi-linear kinetic theoretical analysis in order to compare against the simulation. It is found that the Bernstein mode instability is indeed excited by the loss cone distribution of electrons, but the saturation level of the electrostatic mode is quite low, and that the effects of instability on the electrons is rather minimal. This supports the interpretation of multiple-harmonic emission in the context of the spontaneous emission and reabsorption in quasi-thermal magnetized plasma in the magnetosphere.

• Advances in nano research
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• v.3 no.1
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• pp.29-37
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• 2015

In the current study, the nonlinear vibration properties of an embedded zigzag single-walled carbon nanotube (SWCNT) are investigated. Winkler-type model is used to simulate the interaction of the zigzag SWCNTs with a surrounding elastic medium. The relation between deflection amplitudes and resonant frequencies of the SWCNT is derived through harmonic balance method. The equivalent Young's modulus and shear modulus for zigzag SWCNT are derived using an energy-equivalent model. The amplitude - frequency curves for large-amplitude vibrations are graphically illustrated. The simulation results show that the chirality of zigzag carbon nanolube as well as surrounding elastic medium play more important roles in the nonlinear vibration of the single-walled carbon nanotubes.

• KIEE International Transaction on Electrical Machinery and Energy Conversion Systems
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• v.5B no.2
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• pp.162-167
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• 2005

This paper deals with the method of characteristic analysis of the capacitor-run single- phase induction motor having two poles (4-pole and 2-pole). This motor, which is referred to as a pole change motor in this paper, is capable of variable speed operation without inverters or drives. However, speed-torque curve can be distorted by the harmonic components contained in the magnetic flux density distribution. Therefore, the characteristics of this motor are analyzed using equivalent circuit considering harmonic components and the simulation results are compared with the experimental results.