• Journal of Advanced Marine Engineering and Technology
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• v.31 no.4
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• pp.356-362
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• 2007

The optimum design and the performance analysis software called POSEIDON for the HAWT (Horizontal Axis Wind Turbine) was developed by use of BEMT. The Prandtl's tip loss theory was adopted to consider the blade tip loss. The aerodynamic characteristics of NACA 63-415 airfoils were predicted via X-FOIL and the post stall characteristics were estimated by the Viterna's equations. All the predicted aerodynamic characteristics are fairly well agreed with the Velux wind tunnel test results. The rated power of the testing rotor is 1 kW at design conditions. The power, estimated by use of predicted lift and drag coefficient via X-FOIL becomes a little higher than experimental one.

• Journal of the Korean Society for Railway
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• v.7 no.4
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• pp.339-344
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• 2004

This paper proposes transformerless power conversion system consisting of a single-phase diode rectifier and a shunt hybrid filter for the electric-railway system. The hybrid filter consists of a single tuned LC filter per a phase and a low-rated NPC type multi-level inverter. Compared with conventional active filters. transformers are not used. Also, LC filter works as not only a harmonic filter tuned at the 3rd harmonic frequency but also a switching-ripple filter. The rating of the active filter can be decreased by using a NPC type multi-level inverter. The simulation results confirm the validity of the system.

• Proceedings of the KIEE Conference
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• 2006.07c
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• pp.1472-1473
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• 2006

During normal machine operation, partial discharge(PD) measurements were peformed with turbine generator analyzer(TGA) in two high voltage motors(rated 6.6 kV). These high voltage motors were installed with 80 pF capacitive couplers at the terminal box. TGA summarizes each plot with two quantities such as the normalized quantity number(NQN) and the peak PD magnitude (Qm). The trend analyses of NQN and $Q_m$ value are available for monitoring of the insulation condition in stator windings of high voltage motors.

• Journal of Electrical Engineering and Technology
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• v.7 no.2
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• pp.273-280
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• 2012

Most variable speed wind turbines have pitch control mechanisms and one of their objectives is to protect turbines when the wind speed is too high. By adjusting pitch angles of wind turbine, the inlet power and the torque developed by the turbine are regulated. In this paper, the difference between the real wind speed and its rated value is regarded as a disturbance, and a component called disturbance observer (DOB) is added to the pre-designed control loop. The additional DOB based controller estimates the disturbance and generates a compensating signal to suppress the effect of disturbance on the system. As a result, the stability and the performance of the closed loop system guaranteed by an outer-loop controller (designed for a nominal system without taking into account of disturbances) are approximately recovered in the steady state. Simulation results are presented to verify the performance of the proposed control scheme.

• Journal of Electrical Engineering and Technology
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• v.9 no.2
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• pp.508-513
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• 2014

Heavy load start but light load operation is a common case in practical drive applications. When an induction motor is employed for such applications, its rated power is usually chosen according to the heavy load start. Then, during light load operation, its efficiency and power factor are low. To solve this problem, it is proposed to adjust the motor windings from the startup to the normal operation conditions. In this paper, arrangement of the adjustable windings is introduced, air gap field with different windings is investigated, and steady state operation performance under various loads is examined. It can be seen that by using proper winding arrangement both startup and operation performances are satisfactory.

• Proceedings of the KIPE Conference
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• 2008.10a
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• pp.100-102
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• 2008

As Utility interactive fuel cell systems are widely used, it is required for each power conditioning system(PCS) to have higher generating performance and more stable connecting characteristics. This study is focused to minimization of power losses and hence higher efficiency related to the new half bridge type 3-stage utility interactive PCS topology. The loss factor of half-bridge converter becomes only 1.2[%] under the rated load, and hence total efficiency is maintained to be higher as 91[%].

• Proceedings of the KIPE Conference
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• 2012.07a
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• pp.329-330
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• 2012

The rising popularity of renewable energy sources resulted in development of the units of higher rated powers, where the large-scale plants and grid-connected type solar power systems are increased. Therefore, the importance of grid stabilization, which depends on each country or system-type, has been strengthened by different grid-codes or certifications. In this paper, the control scheme of three-phase photovoltaic system is enhanced, where both injected active and reactive powers are simultaneously controlled with the consideration of the certification of the Germany Association of Energy and Water Industries (BDEW). Experimental results are shown to verify the theoretical analysis.

• Proceedings of the KIPE Conference
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• 2015.11a
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• pp.85-86
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• 2015

In this paper, the bidirectional DC-DC converter is composed of the 900V Silicon-Carbide(SiC) devices to get high efficiency. The 900V SiC device is better than a similar current rated traditional SiC device. it has a lower drain-source resistance and output capacitance. therefore it can reduce the switching and the conduction losses of the DC-DC converter. The experimental results verify the improvement of efficiency and usefulness of 900V SiC device.

• Journal of the Korean Solar Energy Society
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• v.31 no.2
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• pp.107-112
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• 2011

A comparison study between two performance testing results, one is on the site calibration not needed and the other is needed, was proceeded for the understanding on the effect of site calibration on the complex terrain. As a result, it is revealed that all of uncertainty components is effected by the topographical features dramatically. And the maximum difference of uncertainty reached at around 8% of rated capacity of wind turbine. So, the site calibration is an effective method to remove the variable wind effect by the ground complexity and must be proceeded before the power performance testing of a wind turbine.

• Proceedings of the KSR Conference
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• 2009.05b
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• pp.527-532
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• 2009

Recently, Interior Permanent Magnet Machine(IPM) is widely used for traction motor in the high speed train. Due to the high efficiency and high power density of the IPM, it has lots of heat sources such as iron loss and copper loss. These heat sources can cause the demagnetization of permanent magnet, losses in output power and even irreversible defect of the IPM. To prevent the power loss caused by heat sources, the accurate thermal analysis has to be carried out. For the thermal analysis of the IPM, the thermal network is designed for this traction motor. The thermal analysis has executed at rated speed operation. The result of thermal network analysis can be used for the IPM design process.