• Proceedings of the KIEE Conference
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• 2006.07c
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• pp.1689-1690
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• 2006

This study is for implementation of PC based Motor fault diagnosis system. By using harmonics and current signals of the motor, this system diagnoses the motor condition by accumulated harmonic contribution rate. In this proposed system that was composed of 5 parts. A sensor, connection box, evaluation board, device server, and main computer are those. There were two types of sensor, one was harmonic sensor the other was current sensors. The signal was acquired by sensor, and transferred to evaluation board. Second one is connection box. Because the output type of sensor and input type of evaluation board is different, connection box was necessary. Third one was evaluation board. The signal from the sensor was converted to digital signal in evaluation board. And this signal was transferred to device server. Fourth one was device server Device server transferred the data from evaluation board to main computer. And the last one was other parts controlled by main computer. In main computer, there were communication and diagnosis algorithms. The result was derived by main computer. In the result, there were 12 categories and 5 levels of motor conditions. The proposed system had some advantages comparing with stand alone type commercial motor fault diagnosis system. The first, by using remote access it was easier to get the conditions of motor. The second, there was no need to handle the sensors when users measured the motor signals. By this property, no one was necessary at motor location site. The third, this system was less restricted by times and places than commercial stand alone type diagnosis system. Therefore users can operate this system only using the main computer. Once the sensors are installed at the motor, users doesn't need to move to check up the condition of motors. Moreover, if there is ethernet hub, many motors can be not only diagnosed at once but also decreased its cost.

• Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
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• v.18 no.6
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• pp.183-190
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• 2004

This paper proposes a methodology to solve problems upon the circuit design applied to inductor load by applying a circuit to improve power factor with is partial switching PFC module to the power supply system for cooling/heating inverter air conditioner and by designing an input power section in compliance with IEC555-2 on the basis of better input power factor and minimized harmonic components of current. On the other hand, this paper suggested how to control the increase of output voltage along with tぉw current waves and partial switching PFC circuit as well, which can provide the output as twice as input voltage This study applied a method to control the compressors of air conditioner by means of increased the voltage applicable to compressor motor by lowering switching number conclusively, it could solve questions about efficiency, economics, electronic noise and so forth. and so that the reasonable voltage for running moor could be set up along with lower power consumption of air conditioner than estimated It was demonstrated that total sum of energy efficiency to operate system was increased to the extent of valid level. And all this merits and appropriateness was proved by computer simulation and experience.

• Journal of Power Electronics
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• v.10 no.6
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• pp.749-761
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• 2010

The switching frequency of a power device is a very important parameter in the design of a parallel active power filter (PAPF), but so far, very little discussion has been conducted on it in a quantitative manner in previous publications. In this paper, an extensive analysis on the effects of the switching frequency on the performance of a PAPF is made, and a specification of the switching frequency values with different compensation results is presented. A first-order inertia element and a second-order oscillation element are considered as approximate models of a PAPF, respectively. The compensation characteristic for each order of harmonic current is obtained at different switching frequencies. Then, the THDs of each model for the system loads of a rectifier with resistance and inductance loads are proposed. The compensation results of a PAPF controlled as a first-order inertia element are better than those of a PAPF controlled as a second-order oscillation element. With two types of system loads which are rectifier with resistance and inductance loads and rectifier with resistance, inductance and capacitance loads, the THDs of the source current after compensation are presented with different switching frequencies. The compensation characteristics for the most widely used digital control system are investigated. The situation with an analog control is the theoretical characteristic and it is the best situation. The compensation characteristic of the digital control is worse than the compensation characteristic of the theoretical characteristic. Based on these analyses, the specifications of compensation characteristics with different switching frequencies are quite straightforward. Finally, a practical design example is studied to verify the application.

• Journal of Power Electronics
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• v.17 no.6
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• pp.1587-1599
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• 2017

This paper proposes a real-time implementation of an optimal operation of a double stage grid connected wind power system incorporating an active power filter (APF). The system is used to supply the nonlinear loads with harmonics and reactive power compensation. On the generator side, a new adaptive neuro fuzzy inference system (ANFIS) based maximum power point tracking (MPPT) control is proposed to track the maximum wind power point regardless of wind speed fluctuations. Whereas on the grid side, a modified predictive current control (PCC) algorithm is used to control the APF, and allow to ensure both compensating harmonic currents and injecting the generated power into the grid. Also a type 2 fuzzy logic controller is used to control the DC-link capacitor in order to improve the dynamic response of the APF, and to ensure a well-smoothed DC-Link capacitor voltage. The gained benefits from these proposed control algorithms are the main contribution in this work. The proposed control scheme is implemented on a small-scale wind energy conversion system (WECS) controlled by a dSPACE 1104 card. Experimental results show that the proposed T2FLC maintains the DC-Link capacitor voltage within the limit for injecting the power into the grid. In addition, the PCC of the APF guarantees a flexible settlement of real power exchanges from the WECS to the grid with a high power factor operation.

• Asia-pacific Journal of Multimedia Services Convergent with Art, Humanities, and Sociology
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• v.8 no.6
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• pp.853-861
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• 2018

This paper proposes the application of harmonic constraints to address the problems caused by abnormal voltage increases when electric railway vehicles are running. The AC line that supplies the train with power during operation is used to provide electricity of 25kV/60 Hz, but gradually the size and frequency of harmonics involved in the line are varied with the technological evolution of the railroad vehicle electrical equipment. An increase in heat losses due to the failure of the instrument transformer (PT), the main circuit device, which is a serious problem with the recent train safety operation, or to the main displacement voltage. When high frequency components are introduced through low frequency Transformers of the main circuit device, the high intensity of the components is caused by the high intensity of the core and the current flow of the parasitic core is increased, thus generating heat. To solve this problem, the recent adjustment of the sequence has applied artificial NOTCH OFF of the power converter. However, the method of receiving and controlling the OFF signal operates by interaction between the ground and the vehicle's devices, thus it is invalid in the event of failure, and an actual accident is occurring. Therefore, the harmonic currents were required to prevent possible flow of harmonics, and conducted a study to prevent accidental occurrence of train accidents and to verify feasibility of the device through the simulations of the train's experimental analysis and the simulations of the train for safe operation.

• Journal of the Society of Naval Architects of Korea
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• v.60 no.5
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• pp.375-387
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• 2023

The subsea power cables are increasingly important for harvesting renewable energies as we develop offshore wind farms located at a long distance from shore. Particularly, the continuous flexural motion of inter-array dynamic power cable of floating offshore wind turbine causes tremendous fatigue damages on the cable. As the subsea power cable consists of the helical structures with various components unlike a mooring line and a steel pipe riser, the fatigue analysis of the cables should be performed using special procedures that consider stick/slip phenomenon. This phenomenon occurs between inner helically wound components when they are tensioned or compressed by environmental loads and the floater motions. In particular, Vortex-induced vibration (VIV) can be generated by currents and have significant impacts on the fatigue life of the cable. In this study, the procedure for VIV fatigue analysis of the dynamic power cable has been established. Additionally, the respective roles of programs employed and required inputs and outputs are explained in detail. Demonstrations of case studies are provided under severely sheared currents to investigate the influences on amplitude variations of dynamic power cables caused by the excitation of high mode numbers. Finally, sensitivity studies have been performed to compare dynamic cable design parameters, specifically, structural damping ratio, higher order harmonics, and lift coefficients tables. In the future, one of the fundamental assumptions to assess the VIV response will be examined in detail, namely a narrow-banded Gaussian process derived from the VIV amplitudes. Although this approach is consistent with current industry standards, the level of consistency and the potential errors between the Gaussian process and the fatigue damage generated from deterministic time-domain results are to be confirmed to verify VIV fatigue analysis procedure for slender marine structures.

• The Sea:JOURNAL OF THE KOREAN SOCIETY OF OCEANOGRAPHY
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• v.18 no.2
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• pp.53-64
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• 2013

This study analyzed the ADCP records along with wind by KMA and discharge records at Seosan A-, B-district tide embankment by KRC for 33 days obtained in the Chunsu Bay, Yellow Sea, Korea spanning from July 29 to August 30, 2010. Various analyses include descriptive statistics, harmonic analysis of tidal constituents, spectra and coherence, complex correlation, progressive vector diagram and cumulative curves to understand the tidal and sub-tidal current characteristics caused by local wind and discharge effect. Observed current speed ranges from -30 to 40 (cm/sec), with standard deviation from 1.7 (cm/sec) at bottom to 18.7 (cm/sec) at surface. According to the harmonic analysis results, the tidal current direction show NNW-SSE. The magnitudes of semi-major axes range from 9.4 to 14.8 (cm/sec) for M2 harmonic constituent and from 4.4 to 7.0 (cm/sec) for S2, respectively. And the magnitudes of semi-minor axes range from 0.1 to 0.5 (cm/sec) for M2 and from 0.4 to 1.4 (cm/sec) for S2, respectively. In the spectral analysis results in the frequency domain, we found 3~6 significant spectral peaks for band-passed wind and residual current of all depth. These peak periods represent various periodicities ranging from 2 to 8 (days). In the coherency analysis results between band-passed wind and residual current of all depth, several significant coherencies could be resolved in 3~5 periodicities within 2.8 (days). Highest coherency peak occurred at 4.6 (day) with 1.2-day phase lag of discharge to band-passed residual current. The progressive vector of wind and residual current travelled to northward at all layers, and the travel distance at middle layer was greater than surface layer distance. The Northward residual current was caused by a seasonal southern wind, and the density-driven current formed by fresh water input effected southward residual current. The sub-tidal current characteristics is determined by seasonal wind force and fresh water inflow in the Chunsu Bay, Yellow Sea, Korea.

• Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
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• v.23 no.2
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• pp.138-147
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• 2009

In this paper, improved direct torque control(DTC) system for five-phase squirrel-cage induction motor(IM) is proposed. Due to the additional degrees of freedom, five-phase 1M drives present unique characteristics. Also five-phase motor drives possess many other advantages compared with the traditional three-phase motor drive system, such as reducing an amplitude of torque pulsation and increasing the reliability. The DTC method is advantageous when it is applied to the five-phase IM, because the five-phase inverter provides 32 space vectors in comparison to 8 space voltage vectors into the three-phase inverter. However, five-phase motor has structural drawback of 3rd space-harmonics current component, it is necessary to controlled 3rd harmonic current. So to control 3rd harmonic current and enhance dynamic characteristics of five-phase squirrel-cage IM drive, modified DTC method should be demanded. The characteristics and dynamic performance of traditional five-phase DTC are analyzed and new DTC for five-phase IM is presented. A more precise flux and torque control algorithm for the drives can be suggested and explained For presenting the superior performance of the proposed direct torque control, experimental results are presented using a 32-[bit] fixed point TMS320F2812 digital signal processor with 2.2[kW] induction motor.

• The Proceedings of the Korean Institute of Illuminating and Electrical Installation Engineers
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• v.7 no.3
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• pp.27-33
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• 1993

This paper presents the &tal controller for driving high frequency voltage fed PWM inverter that carrier frequency is over 2OkHz.We analyzed the conventional PWM to select a proper PWM pattern. as the result, obtained PWM pattern of the controller in which asynchronus staircase sinusoidal waveform is used as reference signal, and variable carrier ratio method was used for PWM control. The PWM controller is designed by fully digital method. Especially, Thk proposed controller is consisted of 8 bit one-chip microprocessor and digital logic. the former is for arithmetic and data processing, and the latter is for PWM pattern synthesis. Therefore, The responsibility and controllability is improved. Also, Data processing capability is improved using proper program to output modulation index with 9 bits. Circuits configuration of digital controller are made up of one chip 8051 and EPLD, and its controllability is tested by operating voltage fed inverter. Harmonics and current waveform is evaluated and analyzed for the voltage fed inverter system.

• Journal of the Korean Society of Marine Environment & Safety
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• v.21 no.1
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• pp.72-82
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• 2015

In order to effectively and economically apply the previous POM(Princeton Ocean Model) WAD(Wetting And Drying) to the coastal area, the POM WAD was modified such as the water elevation input of tidal harmonics in the open boundaries was included and a CTS(Computing Time Saving) technique was introduced to the model. The modified model was tested to the standing waves in the rectangular bay and the hydraulic experiments for the flow and heat diffusion in the 3D basin. The numerical results showed a good agreement with the analytical solutions of the standing waves and the observed values by the hydraulic experiments, respectively. And also when the modified model with the CTS technique was applied to Gwangyang Bay of Korea, the computing time was decreased by as much as 39.4%.