• Proceedings of the KIEE Conference
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• 1987.07a
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• pp.714-718
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• 1987

• Proceedings of the KIPE Conference
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• 2007.07a
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• pp.101-103
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• 2007

Since they use the low switching frequency in multilevel inverter systems, they generate the high low frequency harmonic components. Generally, LC filter is used at the output terminal of inverter systems to solve this problem. But it causes a voltage drop at the output terminal by use of damping resistors, and causes the problem in which system efficiency decreases due to power loss of the damping resistor. In this paper, we proposed an output filter design method for NPC three-level inverter systems with low switching frequency. And we analyzed the efficiency of the proposed filter system, and the effectiveness of the proposed system is verified by simulation and experimental results.

• Journal of Electrical Engineering and Technology
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• v.3 no.2
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• pp.254-262
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• 2008

This paper presents an active use of doubly-fed induction-generator(DFIG)-based variable-speed wind-turbine for voltage control in power system operation. For reasonable simulation studies, a detail dynamic model of a DFIG-based wind-turbine grid-connected system is presented. For the research objective, an innovative reactive power control scheme is proposed that manipulates dynamically the reactive power from the voltage source converter(VSC) with taking into account its operating state and limits.

• The Transactions of the Korean Institute of Power Electronics
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• v.8 no.5
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• pp.442-449
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• 2003

This paper discusses how to generate the reference compensation voltages in Dynamic Voltage Restorers (DVR) by use of PQR instantaneous power theory. Sensed three-phase terminal voltages are transformed to PQR coordinates without time delay. Since the reference voltage in PQR coordinates is a single dc value, the voltage controller for DVRs is simple and easy to design. Proposed control method can be implemented by feedforward controllers or by feedback controllers. This paper verified the theory by a feedforward controller of a DVR with simulation and experiment.

• Journal of the Korean Society for Railway
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• v.4 no.1
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• pp.16-22
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• 2001

This paper describes two different systems which can compensate harmonic currents generated in the power system. As non-linear loads increase gradually in industry fields, harmonic current generated in the electric power network system also increases. Harmonic current makes a power network current distorted and generates heat, vibration, noise in the power machinery. Many approaches have been applied to compensate harmonic currents generated in the power network system. Among various approaches, in this paper, two kinds of approaches are compared and evaluated. They are flywheel compensator based on secondary excitation of wounded rotor induction motor(WRIM) and primary excitation of squirrel cage induction motor(SCIM). Both systems have a common structure. They use a flywheel as a energy storage device and use PWM inverters.

• Proceedings of the KIEE Conference
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• summer
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• pp.135-137
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• 2004

This paper describes new land use estimation method for long term load forecast using $R\startree$ algorithm. Where $R\startree$ algorithms is a proposed method for efficient spatial search. An estimation result showed that execute time of the proposed method is prior to execute time of conventional method.

• Magazine of the Korean Society of Agricultural Engineers
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• v.15 no.3
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• pp.3089-3095
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• 1973

The power transmission to the traction devices may be very important for the tractor performance and therefore this system has been studied very much in the past. On the other hand, the PTO(Power-take-off) has been considered as an accessary on the tractor with a few work for its power transmission. Because of increased use of PTO operation in various kind of farming operations in recent years, the function of PTO may become such important as the traction facilities. In this study, the power transmission characteristics of PTO drive was analyzed theoretically and some experimental work was done to study on it. The results of the study are as follows: 1) The most stable condition of PTO work was obtained when the intersection angle of the two curves for driving and driven torques was about ${\pi}/2$. 2) To obtain the most stable operation it is better to use both the speed control and the full control together. 3) Six steps differential gear may not be enough to use the PTO power smoothly. It is thought that the three steps differential gear on the shaft of PTO may be necessary additionally for a smooth operation. 4) When the traction facilities and the PTO are used at the same time, the torque of crank shaft becomes Tt + Tp, and the high efficiency and good stability of word will be obtained with the small variation of driving speed. 5) When the tractor was operated with 75% of the rated horse power and 70% of maximum speed, the best thermal efficiency could be obtained. 6) The most dangerous sound for human occured at the rated speed of PTO and tus it may be necessary to control the dangerous noise.

• Journal of Digital Convergence
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• v.18 no.12
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• pp.543-548
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• 2020

The purpose of this study is to implement various movements of multiple objects using a small number of power devices in producing a kinetic design, achieving an effect similar to a work comprised of multiple objects controlled using multiple power devices. While it is more typical to control various objects using multiple power devices, the use of multiple devices leads to higher costs and heavier overall weight. In addition, more power is required to operate the multiple power devices. This study applied a mechanism that allows multiple objects to perform various movements using a small number of power devices. The mechanism significantly reduces overall weight and power consumption. In addition, various movements could be expressed by increasing the rows and columns of objects through the use of the camshaft structure that changed the position and shape of the cam and the use of bevel gears. The significance of this study lies in presenting a new method of controlling multiple objects for designers involved in kinetic design.

• Journal of Power System Engineering
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• v.18 no.4
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• pp.112-116
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• 2014

Roll and pitching motions of a vessel can seriously degrade the performance of mechanical systems and the effectiveness of personnel. Many studies on roll stabilization and trimming control system design have focused on stabilizing the vessel through the use of fins, tanks, rudders and flaps. However the ultimate objective of such approaches must be to improve boarding sensitivity. This paper presents an anti-seasickness bed that consists of a rotator and bearing system that does not make use of electric power. The advantages of this system are its simple construction, usefulness, and safe operation. In this study, the rotation angles of the upper plate of a bed according to change weight of the rotator have been calculated to determine the stability. As a result, it can be concluded that proposed stabilizing bed can be of practical use in the field.

• Journal of Electrical Engineering and Technology
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• v.13 no.5
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• pp.1821-1830
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• 2018

With the wide application of intelligent household appliances, the optimization of electricity behavior has become an important component of home-based intelligent electricity. In this study, a multi-objective optimization model in an intelligent electricity environment is proposed based on economy and comfort. Firstly, the domestic consumer's load characteristics are analyzed, and the operating constraints of interruptible and transferable electrical appliances are defined. Then, constraints such as household electrical load, electricity habits, the correlation minimization electricity expenditure model of household appliances, and the comfort model of electricity use are integrated into multi-objective optimization. Finally, a continuous search multi-objective particle swarm algorithm is proposed to solve the optimization problem. The analysis of the corresponding example shows that the multi-objective optimization model can effectively reduce electricity costs and improve electricity use comfort.