• Proceedings of the KIEE Conference
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• 2005.07b
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• pp.1750-1752
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• 2005

This paper presents a variable speed wind generation system where fuzzy logic controllers is used as efficiency optimizer. The fuzzy logic controller increments the machine flux by on-line search to improve the generator efficiency in case of light load. The speed of the induction generator is controlled according to the variation of the wind speed in order to produce the maximum output power The generator reference speed is adjusted according to the optimum tip-speed ratio. The complete control system has been developed by simulation study.

• The Transactions of The Korean Institute of Electrical Engineers
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• v.57 no.10
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• pp.1696-1702
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• 2008

This paper proposes a voltage compensation device direct control strategy to realize the distributed, autonomous voltage control of the distribution system, which based on voltage data collected from customers of the remote site under the ubiquitous-based distribution system. In the proposed method, The ULTC and the SVR(Step Voltage Regulator)s compensate autonomously the voltage for self-compensation area based on the voltage data furnished from the ubiquitous device of customers. Also, the SVRs overcome the limit of single-operation of ULTC by the interlocking operation with the ULTC and enhance the voltage compensation capability for the customer. In particular, an optimization design method and a fuzzy design method are compared to determine the effective control method of the voltage compensator under the ubiquitous-based on-line operation environments. In fuzzy method, the tap of voltage compensator is defined as output member. Finally, the proposed two methods are implemented in Visual C++ MFC, the effectiveness is proved by simulation based on the worst virtual voltage data. Also, an optimal voltage compensation strategy is determined under on-line environments based on analyzed results.

• Journal of Ocean Engineering and Technology
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• v.22 no.3
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• pp.34-40
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• 2008

his study discusses the design of an automatic berthing control algorithm for ships with a haw thruster and a stern thruster, as well as a rudder. A nonlinear mathematical model for the law speed maneuvering of ships was used to design a MIMO (multi-input multi-output) nonlinear control algorithm. The algorithm consists of two parts, the forward velocity control and heading angle control. The control algorithm was designed based on the longitudinal and yaw dynamic models of ships. The desired heading angle was obtained by the so-called "Line of Sight" method. An optimal control force allocation method forthe rudder and the thrusters is suggested. The nonlinear control algorithm was tested by numerical simulations using MATLAB, and showed good tracking performance.

• Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
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• v.12 no.2
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• pp.69-76
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• 1998

This paper presents a novel algorithm for determining the optimal operation of a cogeneration plant with back-pressure and extraction-condensing turbine/generators. The proposed algorithm determines the optimum load of boilers and turbine/generators, using only one parameter, the steam mass flow rate, which can be obtained directly from on-line measurement during plant operation. The proposed algorithm consists of the non -linear operating cost function, and its correlated constraints. Furthermore, it has been successfully applied to an actual industrial cogeneration plant, with satisfactory results. Comparison of these results with actual operating data has revealed that using the proposed algorithm results in at least 1.2~4.5[%] operating cost saving, depending on the process steam load. Furthermore the proposed algorithm can be easily installed in a process control computer because the required input data can be easily obtained from information available on-line.n-line.

• Transactions of The Korea Fluid Power Systems Society
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• v.4 no.1
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• pp.18-24
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• 2007

The continuously variable transmission (CVT) of which speed ratio can change continuously in a fixed range has the benefits of low fuel consumption and exhaust gas because it enables the engine of a vehicle to operate in a high efficiency range regardless of vehicle speed. The speed ratio of belt type CVT is controlled by adjusting line pressure. The one of the line pressure control methods, mechanical-hydraulic control is usually adopting VDT's control method, in which the secondary solenoid valve has two functions both a regulator and a line pressure controller. However, this control method could not show the high performance of CVT with optimal driving capability because of the limitation of simple control algorithm, and it could not gain market share sufficiently in spite of the advantage of CVT with low fuel consumption. On the other hand, the electro-hydraulic control method gives the enhancement of power performance and low fuel consumption by implementing various driving mode using the proportional control or PWM control. The key of CVT technique is to develop a control algorithm of the electro-hydraulic solenoid valve in order to implement the speed ratio efficiently. In this paper, the line pressure control algorithm is proposed and the hydraulic system is controlled using metal belt type CVT test rig and the embedded ECU platform.

• Journal of Korea Water Resources Association
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• v.41 no.12
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• pp.1211-1218
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• 2008

This study is for design of the detention system distributed in a watershed by the Multi-Objective Genetic Algorithms(MOGAs). A new model is developed to determine optimal size and location of detention. The developed model has two primary interfaced components such as a rainfall runoff model to simulate water surface elevation(or flowrate) and MOGAs to get the optimal solution. The objective functions used in this model depend on the peak flow and storage of detention. With various constraints such as structural limitations, capacities of storage and operational targets. The developed model is applied at Gwanyang basin within Anyang watershed. The simulation results show the maximum outlet reduction is occurred at detention facilities located in upper reach of watershed in the peak discharge rates. It is also reviewed the simultaneous construction of an off-line detention and an on-line detention. The methodologies obtained from this study will be used to control the flood discharges and to reduce flood damage in urbanized watershed.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2004.11a
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• pp.1012-1015
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• 2004

There have been several kinds of attempts to actively control the deflected noise behind the noise barrier. Omoto's work in 1993 would be one of the fundamental studies, where he placed the control sources uniformly parallel to the noise barrier. Following this study, Yang pointed that the average distance between the noise source and control sources is more important than the arrangement of control sources such as a straight line or an arc type distribution. In 2004, Baek tried to show optimal arrangement of control sources while keeping the average distance between the noise source and control sources. He used simulated annealing algorithm which is one of the natural algorithms for the selections of optimal control source positions, but the searching technique was a hybrid of the simulated annealing and the sequential searching to adapt to the vast amount of searching time. This study is about the performance comparison between the pure sequential searching and the hybrid one. The simulation results show very similar performance and a pure simulated annealing searching will be more beneficial for the noise reduction performance but at the cost of computing time.

• Journal of the Korean Institute of Telematics and Electronics
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• v.25 no.1
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• pp.42-48
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• 1988

MM(multimode) PWM(pulse width modulation) Suitable for high performance and harmonic effects minimization of VSI (voltabge source invertetr)-IM (induction motor)drive system is proposed. The approximated optimal, suboptimal and optimal PWM are implemented in the low frequency range, while square wave operation is realized in the hibh frequency range. The pulse width Modulator is capable of generating control signals to a transistorized inverter operating at about 1KHz. All functions except digital comparison have been implemented in softyware making the scheme economical, flexible and reliable. Pulse width modulator is built and tested experimentally. In order to confirm the effectiveness and the reliability of the theoretical proposition, this scheme is applied to 1Hp, Three phase IM. As results, it is concluded that the scheme of MM PWM is superior to other conventional switching scheme through the discussions or analysis carried out on the items such as line-to-line voltage, current and spectrum of current harmonic components observed at the output terminal of inverter, noise level of motor.

• Journal of Power Electronics
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• v.8 no.4
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• pp.345-353
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• 2008

In this paper, a novel loss minimization of an induction generator in wind energy generation systems is presented. The proposed algorithm is based on the flux level reduction, for which the generator d-axis current reference is estimated using support vector regression (SVR). Wind speed is employed as an input of the SVR and the samples of the generator d-axis current reference are used as output to train the SVR algorithm off-line. Data samples for wind speed and d-axis current are collected for the training process, which plots a relation of input and output. The predicted off-line function and the instantaneous wind speed are then used to determine the d-axis current reference. It is shown that the effect of loss minimization is more significant at low wind speed and the loss reduction is about to 40% at 4[m/s] wind speed. The validity of the proposed scheme has been verified by experimental results.

• Proceedings of the KIEE Conference
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• 1998.11a
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• pp.329-331
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• 1998

This paper presents a modified Learning Vector Quantization rule to control shunt capacitor banks and feeder voltage regulators in electric distribution systems with Kohonen Neural Network(KNN). The objective of the KNN is on-line decision of the optimal state of shunt capacitor banks and feeder voltage regulators which minimize $I^{2}R$ losses of the distribution system while maintaining all the bus voltages within the limits. The KNN is tested on a distribution system with 30 buses, 5 on-off switchable capacitor banks and a nine tap line voltage regulator.