• 한국신재생에너지학회:학술대회논문집
• /
• 2008.10a
• /
• pp.310-314
• /
• 2008

The exploitation of the wind energy resource is a rapidly growing area world-wide. The number of installed units is continuously increasing, and it is important to respect and to deal with the impact of wind turbine. This paper addresses the power quality characteristics of U57 Wind Turbine. 750kW gearless type wind turbine for low wind speed, named U57, is developed by UNISON. The power quality measurement system consists of measuring WTG output current, line-to line voltage and wind speed signal. With using measured data, power quality measurement is evaluated about maximum power, reactive power, voltage fluctuation, harmonics according to IEC 61400-21.

• Proceedings of the KIEE Conference
• /
• 2004.10a
• /
• pp.224-226
• /
• 2004

Digital Kalman filter is presented as a powerful approach to obtain the reference estimation of the control current for shunt active power filter. This algorithm provides the best estimate of the fundamental and harmonic frequency components from the sampled values of the line current or voltage. By adopting of the digital Kalman filtering algorithm, the structure of the control algorithm eliminates the need of a Phase locked loop(PLL) for the synchronization of the reference signal used in the compensation and it not sensitive to the distortion of the line voltage. The effectiveness of the algorithm is confirmed by the computer simulations.

• Proceedings of the KIEE Conference
• /
• 1997.07a
• /
• pp.221-223
• /
• 1997

This paper deals with the slip power recovery system using switch mode converter in the inverter DC side, which recovers slip power of induction machine to AC line with the aid of the boost converter. As a results, the motor speed can be controlled by the duty ratio of boost switch, not by inverter firing angle. This results that the reactive power produced by phase controlled inverter and diode rectifier can be greatly reduced and linear speed regulation can be obtained. Moreover, the harmonic components of line current caused by the commutation in inverter and rectifier can be considerably suppressed. Therefore, most of the problems in conventional system can be solved.

• Proceedings of the KSR Conference
• /
• 2004.10a
• /
• pp.1480-1485
• /
• 2004

In this paper, a real-time digital kalman filtering algorithm is used to obtain the reference estimation of the control current for shunt active power filter. This algorithm provides the best estimate of the fundamental and harmonic frequency components from the sampled values of the line current or voltage waveform. By adopting of the digital Kalman filtering algorithm, the structure of the control algorithm eliminates the need of a Phase locked loop(PLL) for the synchronization of the reference signal used in the compensation and it not sensitive to the distortion of the line voltage. The effectiveness of the algorithm is confirmed by the computer simulations.

• Proceedings of the KIEE Conference
• /
• 1998.07c
• /
• pp.943-945
• /
• 1998

This paper presents a method of modeling of DSTATCON (Distribution-line Static Condenser) for installation in a specific plant and analyze the effectiveness of the DSTATCON from the viewpoints of voltage regulation and harmonic mitigation in a distribution line. For the reliable modeling, detailed information on distribution system and loads is performed by field measurements. The DSTATCON has been modeled according to the control algorithm of real controller. The effectiveness of the DSTATCON installation is verified by simulation using EMTDC.

• Journal of the Korean Magnetics Society
• /
• v.5 no.4
• /
• pp.299-303
• /
• 1995

In order to improve the read-out signal waveform, a shielded magnetoresistive (SMR) head has been designed and studied by applying the transmission-line model. The bias and signal field distribution, the voltage output, the harmonic output signal and resistance value of MR element are simulated as functions of bias current and recording displacement. The results show that the SMR head has good linear character with respect to the medium recording signal in high recording frequency of about 2.5 MHz. The amplitude and waveform of reroduction signal have been obviously improved. The saturation effect on the symmetry and amplitude of reproducing output have also been analyzed.

• The Transactions of the Korean Institute of Electrical Engineers P
• /
• v.55 no.3
• /
• pp.141-145
• /
• 2006

The line current problem(2-dimensional space : point source) is not easy to analyze the magnetic field using the standard finite element method(FEM), such as overhead trolley line or transmission line. To supplement such a defect this paper is proposed the coupling scheme of analytical solution and FEM. In analysis of the magnetic field using the standard FEM. If the current region is a relatively small compared to the whole region. Therefore the current region must be finely divided using a large number of elements. And the large number of elements increase the number of unknown variables and the use of computer memories. In this paper, an analytical solution is suggested to supplement this weak points. When source is line current and the part of interest is far from line current, the analytical solution can be coupling with FEM at the boundary. Analytical solution can be described by the multiplication of two functions. One is power function of radius, the other is a trigonometric function of angle in the cylindrical coordinate system. There are integral constants of two types which can be established by fourier series expansion. Also fourier series is represented as the factor to apply the continuity of the magnetic vector potential and magnetic field intensity with tangential component at the boundary. To verify the proposed algorithm, we chose simplified model existing magnetic material in FE region. The results are compared with standard FE solution. And it is good agreed by increasing harmonic order.

• Journal of the Korean Society for Aeronautical & Space Sciences
• /
• v.34 no.4
• /
• pp.11-16
• /
• 2006

Effects of an orifice on suppression of pressure oscillation in a fluid feeding line are investigated numerically through the installation of an orifice inside the feeding line. Based on linear acoustic theory, acoustic-damping effect of an orifice is emphasized in this study. When an orifice is installed at the node of pressure oscillation corresponding to the anti-node of velocity oscillation, damping capacity is maximized. On the other hand, the orifice installed at the anti-node of pressure oscillation has little damping capacity. As the blockage ratio and thickness of an orifice increase in the feeding line, damping factor increases. The feeding line with smaller diameter has more damping capacity, but damping factor increases more appreciably with blockage ratio in the feeding line with larger diameter.

• Journal of Electrical Engineering and Technology
• /
• v.3 no.3
• /
• pp.391-400
• /
• 2008

Multi-pulse topology of converters using elementary six-pulse GTO - VSC (gate turn off based voltage source converter) operated under fundamental frequency switching (FFS) control is widely adopted in high power rating static synchronous compensators (STATCOM). Practically, a 48-pulse ($6{\times}8$ pulse) configuration is used with the phase angle control algorithm employing proportional and integral (PI) control methodology. These kinds of controllers, for example the ${\pm}80MVAR$ compensator at Inuyama switching station, KEPCO, Japan, employs two stages of magnetics viz. intermediate transformers (as many as VSCs) and a main coupling transformer to minimize harmonics distortion in the line and to achieve a desired operational efficiency. The magnetic circuit needs altogether nine transformers of which eight are phase shifting transformers (PST) used in the intermediate stage, each rating equal to or more than one eighth of the compensator rating, and the other one is the main coupling transformer having a power rating equal to that of the compensator. In this paper, a two-level 48-pulse ${\pm}100MVAR$ STATCOM is proposed where eight, six-pulse GTO-VSC are employed and magnetics is simplified to single-stage using four transformers of which three are PSTs and the other is a normal transformer. Thus, it reduces the magnetics to half of the value needed in the commercially available compensator. By adopting the simple PI-controllers, the model is simulated in a MATLAB environment by SimPowerSystems toolbox for voltage regulation in the transmission system. The simulation results show that the THD levels in line voltage and current are well below the limiting values specified in the IEEE Std 519-1992 for harmonic control in electrical power systems. The controller performance is observed reasonably well during capacitive and inductive modes of operation.

• The Transactions of the Korean Institute of Power Electronics
• /
• v.10 no.3
• /
• pp.226-232
• /
• 2005

Recently, many nation have released standard such as IEC 61000-3-2 and IEEE 59, which impose a limit on the harmonic current drawn by equipment connected to AC line in order to prevent the distortion of an AC Line. Therefore, Plasma Display Panel(PDP) which is highlightened in digital display device also has the Power Factor Correction(PFC) circuit to meet the harmonic requirements. In PDP power module, the conventional boost converter is usually used for the PFC circuit. However, it comes serious thermal problem on it's bridge diode due to heat of PDP, and therefore the system stability is not guaranteed. In this paper, the bridgeless boost converter, which is used for PFC circuit of the PDP power module, is designed and verified the possibility of the application In a practical product in a view of efficiency, component count, temperature and etc.