• The Transactions of The Korean Institute of Electrical Engineers
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• v.56 no.5
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• pp.834-840
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• 2007

A generator plays an important role in transferring an electric power to power system networks. The generator protection systems in Korea have been imported and operated through a tum-key from overseas entirely. Therefore, a study of the generator protection field has in urgent need for a stable operation of the imported goods, and for preparation of next generation protection system. The paper describes the fault detection algorithm using WT(Wave!et Transform) of currents for a generator protection. The fault current signals after executing a terminal fault modeling collect using a MA TLAB package, and calculate the wavelet coefficients through the process of a multi -level decomposition (MLD). The proposed algorithm for a fault detection using the Daubechies WT (wavelet transform) was executed with a C language for the command line function and for the real time realization after analyzing MATLAB's graphical interface. The advanced technique had complemented the defects of a DFT by applying a Daubechies WT. and had improved faster a speed and more accurate of fault discriminant than a conventional DFR.

• Proceedings of the KIPE Conference
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• 2008.06a
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• pp.136-138
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• 2008

The output voltage of synchronous generator is regulated constantly by field current control in excitation system. Most of ship generator exciter system uses the thyristor phase controlled rectifier. However this rectifier is difficult to realize that the speed control system because its control period is slower than MOSFET and IGBT type converter. Therefore, this paper deals with PMG(Permanent Magnet Generator) type digital excitation system using MOSFET for ship synchronous generator. The organization of this excitation system is very simple. When the generator is under the short circuit accident, the output voltage becomes zero state and AVR can not operate. Thus generator requires the function for flowing output current through CBS. The performance of the proposed system is evaluated on a 10kVA experimental prototype circuit in place of real ship generator.

• Journal of the Korean Solar Energy Society
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• v.30 no.4
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• pp.1-8
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• 2010

The mechanical parts of small windp ower generator less than 10kW are manufactured in the form of removing most of the accelerators. The braking system to protect blade from damages caused by high wind speed is manufactured in a manner having apparatus system(furling), manual brake or no brake. This study is on braking system in small size wind power generator, and carried out survey as following steps by applying electric braking system which uses armature reaction. We explained the principle of electric braking system and the principle of existing braking system. Also, this paper interpreted short circuit current through open circuit and short circuit, as well as checking brake system's action using armature reaction with real construction of control device.

• The Transactions of the Korean Institute of Electrical Engineers B
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• v.49 no.2
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• pp.93-101
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• 2000

This paper presents a novel method for the transient of eddy currents in the dampers of a super-conducting synchronous generator(SCG). The method proposes a 2-D corrected model which takes into account the influence of leakage fluxes of the field winding ends by increasing the effective air gap in order to consider the high precision of the analysis for the conventional 2-D model. The electromagnetic fields for the corrected model are analyzed by the time-stepping finite element method, thus the eddy currents in the dampers and electro-motive forces(EMF) in the stator windings are calculated. As the results, it is proved the presented method is comparatively accurate by comparing measured phase EMF values and the simulation ones, where about 6.4% error at the maximum value of EMF is occurred between them.

• Journal of Institute of Control, Robotics and Systems
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• v.15 no.12
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• pp.1163-1168
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• 2009

The power quality of wind energy becomes more and more important in connecting wind-farms to the grid, especially weak grid. This paper presents the simulation of a wind farm of a permanent magnet synchronous generator (PMSG) and a doubly fed induction generator (DFIG). Flicker mitigation is performed by using PMSG as a static synchronous compensator (STATCOM) to regulate the voltage at the point of common coupling (PCC). A benefit of the measure is that integrating two function of to control the active power flow and to reduce the voltage flicker in a wind farm. Simulation results show that controlling PMSG is an effective and economic measure in reducing the flicker during continuous operation of grid connected wind turbines regardless of short circuit capacity ratio, turbulence intensity and grid impedance angle.

• Journal of Institute of Control, Robotics and Systems
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• v.20 no.9
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• pp.914-921
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• 2014

In this paper, an algorithm is suggested to detect an offset angle of the absolute rotor position sensor after the initial assembly of a PMSG. Unlike previous studies in a stationary state, this one is not designed to detect an electrical angle but rather the absolute position of the rotor is detected while operating the generator. Also,a position sensor, current sensors and voltage sensor were used to ensure reliability. This technique completes the detection of the sensor offset in two steps. In the first step, a zero-crossing of the EMF is measured using a voltage sensor to detect the electrical angle offset when the alternator is actuated by the engine. In the second step, a high frequency current is injected along the d-axis on-line during the control of the generation, eventually to obtain the inductance using a DFT (Discrete Fourier Transform), and then to ultimately extract the final electrical angle offset through the comparison of the inductance magnitude. The suggested algorithm was validated with PSIM simulation and, furthermore, was tested with actual experiments on a dynamometer.

• Proceedings of the KIEE Conference
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• 1997.11a
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• pp.253-256
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• 1997

This paper describes a novel design method for compensating field time-constant of micro-synchronous machine so that its terminal flux can show the same characteristics as large-scale synchronous machine's. In addition to it, the suggested design method can determine the field time-constant regulator's parameters considered the nonlinearities of micro-synchronous machine such as saturation and loading effect. This method applied to 5kVA micro-synchronous machine, and the digital time-constant regulator with digital AVR were designed such that the short field time-constant, $T_{do}'=1.12\;sec$, can take on the large-scale synchronous machine time constant, $T_{do}'=1.47\;sec$. After determining the parameters of controllers, the real time digital time-constant regulator and digital AVR algorithm were implemented by using the PC with Penumum processor, and the usefulness of suggested real time digital time-constant regulator was verified by observing its good performance on the excitation of micro-synchronous machine.

• The Transactions of the Korean Institute of Electrical Engineers P
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• v.67 no.2
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• pp.57-62
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• 2018

A brush-less type synchronous generator driven by an internal-combustion engine is used for emergency electric source. These types of generators have to maintain a certain range of output voltage even under the sudden load change conditions such as full load application and removal. This paper describes a method for suppressing the output voltage of a synchronous generator that operates excessively when the load fluctuates. The method used in this paper is a feedforward control method in which the main voltage control consists of a feedback loop using a typical PID controller and the load current is detected as a disturbance element and compensated directly. A feedforward system is constructed in which the load current is regarded as disturbance, and the appropriate feedforward controller configuration and parameters are found through simulation. Finally, it can be seen through the experiment that the feedforward control is performed properly. It can be seen that the generator terminal voltage is recovered to the steady state in a short period of time as compared with the existing PID control method even when the entire load of the generator is changed.

• Journal of the Korean Society of Safety
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• v.21 no.2 s.74
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• pp.52-56
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• 2006

This paper describes the methods for the detection of shorted-turn in the rotor of a cylindrical synchronous generator. A search coil is installed in the air-gap to detect the shorted-turn. The occurrence of a fault in the rotor winding results in a decrease of the induced voltages in the stator. And the magnitude of the rotor flux can be estimated by using the search coil and the estimated stator voltages respectively. And the magnitude of the estimated rotor flux is used for discriminating the rotor windings short or not by detecting the magnitude of the rotor flux. The method using a search coil located in the air-gap can detect not only the occurrence of a turn fault but also its position in the rotor winding. But the method using the estimated stator voltages gives the magnitude of the rotor flux, and only the number of a short-turn.

• The Transactions of the Korean Institute of Electrical Engineers B
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• v.50 no.3
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• pp.101-106
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• 2001

Air-cored superconducting synchronous generator(ASSG) is characterized by an air-cored machine with its rotor iron and stator iron teeth removed. For this reason, in the case of the shape optimum design of ASSG, other design variables different from an iron-cored machine should be considered, which will lead to substantial improvement on the performance. The major design variables that are considered by using Three-dimensional Finite element Method(3D FEM) in this paper are : 1) field coil width, 2) axial length of magnetic shield, and 3) armature winding method. End-ring of armature winding is considered in the calculation of EMF. When it comes to field coil width, as field coil width enlarges, its effective field increases but the maximum field on the superconductor decreases. this determines the critical current density. this study presents an effective field coil width, axial length of magnetic shield, and armature winding method, and also the analysis is verified by the experimental results.