• The Transactions of the Korean Institute of Electrical Engineers B
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• v.48 no.11
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• pp.646-654
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• 1999

This paper deals with PWM patterns for harmonic reduction in inverter fed traction motors and the gear changing techniques for the variable speed drive of traction motor. GTOs are used as switching device of inverter because traction motor is a large load. To derive PWM rattern which can minimize the harmonics with the limited switching frequency, the output current and torque characteristic of SPWM and SHE PWM was analyzed. GTO inverter used for traction motor drive includes harmonics in the output current and torque by the limitation of switching frequency. However, the hybrid PWM method that adopt SPWM in the range of low frequency and SHE PWM in upper frequency range can achieve less harmonic characteristics in GTO inverters. If the traction motor is driven in variable speed by the proposed PWM pattern, 7 times of gear changing is needed. At the instant of the mode change, magnetic flux and torque may be altered and the large current flow. To reduce such an undesirable transient behavior, it is also presented the technique for the gear changing of inverter fed traction motor drive operated with the hybrid PWM. The results are verified by simulations and experiments.

• Journal of Power Electronics
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• v.18 no.1
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• pp.195-203
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• 2018

In the variable speed Wind Turbine based on ElectroMagnetic Coupler (WT-EMC), a synchronous generator is coupled directly to the grid. Therefore, like conventional power plants, WT-EMC is able to inherently support grid frequency. However, due to the reduced inertia of the synchronous generator, WT-EMC is expected to be controlled to increase its output power in response to a grid frequency drop to support grid frequency. Similar to the grid frequency support control of Type 3 or Type 4 wind turbine, inertial control and droop control can be used to calculate the WT-EMC additional output power reference according to the synchronous generator speed. In this paper, an experimental platform is built to study the grid frequency support from WT-EMC with inertial control and droop control. Two synchronous generators, driven by two induction motors controlled by two converters, are used to emulate the synchronous generators in conventional power plants and in WT-EMCs respectively. The effectiveness of the grid frequency support from WT-EMC with inertial control and droop control responding to a grid frequency drop is validated by experimental results. The selection of the grid frequency support controller and its gain for WT-EMC is analyzed briefly.

• Journal of Korea Technology Innovation Society
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• v.14 no.3
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• pp.552-577
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• 2011

We have analyzed technology transfer and commercialization process and factors affecting the outcomes of technology commercialization of public research institutes in Korea. A technology commercialization process model was presented as an input, intermediate outcomes/capabilities, output (outcome) structure using the structural equation model. Input variables include R&D input, technology commercialization strategy/support, collaboration, social capital. The model also includes R&D capabilities and technology commercialization performance as intermediate variable and output variable respectively. The technology commercialization performance was measured as the number of technology transfer and spin-off. We conducted survey and 88 institutes responded. Empirical results show that R&D input influence R&D capabilities and R&D capabilities influence the output of technology transfer and commercialization. Collaboration activities and social capital also appear to have a positive effect on the output. However, the effect of strategy and support on the output appear to be not statistically significant.

• The Journal of the Convergence on Culture Technology
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• v.8 no.5
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• pp.591-596
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• 2022

Since 4-bar linkage widely used in various industrial fields has a fixed link length, it is inconvenient to add an independent link structure or control device to change the movement of output link. Therefore, this paper proposes a new concept of variable 4-bar linkage mechanism to selectively adjust the movement of the output link to fit desired situations, and applied to the commercial table fans, which is a representative product using a 4-bar linkage system. The optimal rotation angle steps for efficiency are determined experimentally and the appropriate lengths of linkage to fit each step are calculated analytically. Changes in the linkage length are implemented by the rotational motion using a grooved cylindrical cam and the feasibility of the proposed variable linkage mechanism is verified through fabrication and measurement. The presented variable link mechanism is expected to improve the efficiency of industrial robots and fuel valve systems.

• Journal of IKEEE
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• v.9 no.2 s.17
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• pp.87-100
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• 2005

In this paper, a design of an integral augmented optimal variable structure system(IOVSS) is presented for the prescribed output control of uncertain SISO systems under persistent disturbances. This algorithm aims at removing the problems of the reaching phase by incorporating advanced optimal control theory. By means of an integral sliding surface, the reaching phase is completely removed, and the integral sliding surface can be defined from a given initial state to origin without any reaching phase. The ideal sliding dynamics of the integral sliding surface is obtained in the form of the state equation and is designed in an optimal sense by targeting the design of the integral sliding surface and equivalent control input. The corresponding control input is selected in order to generate the sliding mode on the predetermined integral sliding surface. As a result, the whole sliding output from a given initial state to origin is completely guaranteed against persistent disturbances. Moreover the prediction/predetermination of output is enabled, which helps in improving the performance over previously implemented VSS's. Through an illustrative example, the usefulness of the algorithm is shown.

• Journal of the Korean Institute of Intelligent Systems
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• v.15 no.1
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• pp.24-29
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• 2005

In the fuzzy control for the multi-variable system, it is difficult to obtain the fuzzy rule. Therefore, the parallel structure of the independent single input-single output fuzzy controller using a pairing between the input and output variable is applied to the multi-variable system. However, among the input/output variables which arc not paired the interactive effects should be taken into account. these mutual coupling of variables affect the control performance. Therefore, for the control system with a strong coupling property, the control performance is sometimes lowered. In this paper, the effect of mutual coupling of variables is considered by the introduction of a neuro-fuzzy controller using relative gain matrix. This proposed neuro-fuzzy controller automatically adjusts the mutual coupling weight between variables using a neural network which is realized by back-propagation algorithm. The good performance of the proposed nero-fuzzy controller is verified through computer simulations on 200MW boiler systems.

• The Transactions of the Korean Institute of Power Electronics
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• v.19 no.6
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• pp.572-581
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• 2014

A design and control method of DC/DC converter, which can control variable DC-link voltage to drive a fuel cell electric vehicle (FCEV), is proposed in this study. Given that a fuel cell has low-voltage and high-current characteristics, the required voltage for operating motor must be output through the DC/DC boost converter in the system to drive an FCEV. The proposed converter can choose the output voltage of battery or fuel cell in consideration of the driving mode, as well as control DC-link voltage in accordance with the back electromotive force. The switching lag-time to prevent shortage of pulse-width modulation inverter arms makes distorted current waveform caused by voltage distortion. Through this control method, the proposed converter can reduce the output voltage distortion and current ripple of the inverter, thereby reducing the distorted torque. Simulations and experimental results are presented to verify the reliability of the proposed DC/DC converter.

• The Transactions of the Korean Institute of Power Electronics
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• v.11 no.4
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• pp.321-327
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• 2006

In this paper, An Automatic Synchronous Switch Post Regulator for Multi-Output Flyback Converter is proposed. The proposed circuit is composed simply using a new automatic synchronous switch instead of conventional complex Switch Post Regulator owing to difficulty of drive circuit materialization and synchronization between main output and auxiliary output. By using the proposed circuit, we can make simple and inexpensive Multi-Output Converter with variable and accurate output voltage and proved adequacy of proposed circuit through experiment, simulation and theoretical analysis.

• Proceedings of the Korean Institute of IIIuminating and Electrical Installation Engineers Conference
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• 1990.10a
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• pp.47-52
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• 1990

This paper presents a cyclocoverter with a LC resonant circuit for a induction motor dr-ive. The cycloconverter can provide variab-le voltage and frequency three phase output while keeping the input displacement factor at 1.0. The input current wave forms are sinusoidal, and the wide output frequency ran-ge is appropriate for variable speed AC motor drives.

• The Transactions of the Korean Institute of Electrical Engineers
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• v.36 no.8
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• pp.539-546
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• 1987

In case of operating at Variable speed the induction motor by a frequency transformer, it will cause ripples in motor torque and considerably bad effects on the machines because the output side of the frequency transformer involves a great number of harmonics. This paper Presents the methods of decreasing torque ripples in induction motor and of improving current waveform, by means of forming the waveforms of output current into multi-step waveforms similiar to sinusoid, and also by means of eliminating the harmonic components maximally, in case of operating a 18-phase multi-inverter combining 3-step current source inverter.