• Proceedings of the KIPE Conference
• /
• 2016.07a
• /
• pp.359-360
• /
• 2016

This paper presents a new predictive current control (PCC) method to achieve the coordinate control of power and current of the matrix converter under unbalanced input voltages. In order to control the power fluctuation in the input side, the flexible source current reference is generated based on the positive-negative sequence components of the input voltage. The optimal switching state to adjust source and load currents is selected by minimization the cost function which is obtained from the sum of the absolute errors between the current references and their predictive values. Simulation results are given to validate the effectiveness of the proposed PCC method.

• Journal of the Korean Society of Safety
• /
• v.20 no.2 s.70
• /
• pp.50-55
• /
• 2005

This Paper Presents assessment of fuzzy measure Possibility far the electromagnetic field according to voltage fluctuation of the Jechon Area. To cope with substantial electromagnetic analysis, the safety assessment were analyzed the double 154kV T/L, 345kV T/L, Jechon-Ichon Jechon-Youngju, respectively. As the results of case study, in case of 345kV T/L, the electric field value was 11.4927kV/m, magnetic field value was 0.4622G at the Point about 7m away from the line in severest case. Tn assessment of fuzzy measure Possibility for the electromagnetic field, this paper use probability of fuzzy and measure of fuzziness technique.

• The Transactions of The Korean Institute of Electrical Engineers
• /
• v.60 no.11
• /
• pp.2017-2020
• /
• 2011

Flicker, which is also known as voltage fluctuation, is an electromagnetic phenomenon generated by large scale nonlinear loads, such as arc furnaces and welding machines. Since a severe and continuous flicker can cause to some damages to electrically sensitive loads as well as human's visual irritations, it needs to be appropriately managed by being accurately measured, quantified and assessed. In Korea, an equivalent 10-Hz flicker index, shortly ${\Delta}V10$, is used to determine the permission limit of flicker. This paper presents an efficient calculation of the flicker index by using a half-cycle sliding window and a recursive method, showing a concrete calculating procedure of ${\Delta}V10$ from the viewpoint of signal processing.

• Journal of Korean Society of Coastal and Ocean Engineers
• /
• v.3 no.4
• /
• pp.255-260
• /
• 1991

A voltage measuring system specified for the voltage fluctuation of the Pusan-Hamada submarine cable is developed by adding circuits of differential amplification and analog-to-digital conversion to a microprocessor-based data logger with a data modem. This system is charaterized by its small size. no power failure. fully unmanned operation. and precise instrumental drift correction. In addition to the cable voltage and current it measures an ambient temperature and a mercury cell voltage in order to calibrate temperature effect and check its long-term stability. The data acquired by this system show that the voltage signal. comprising fast random noises with a constant width of about 0.2V. fluctuates within a range of about 1V and the fluctuation frequency is similar to that of tidal motion. The source voltage of power feeding equipment (PFE) for the cable system seems to be affected when the room temperature changes rapidly.

• The Transactions of the Korean Institute of Electrical Engineers
• /
• v.31 no.7
• /
• pp.11-17
• /
• 1982

In this paper, a reliable and convenient evaluation method for the adequacy of any radial distribution line's voltage drop is proposed for improvement of the voltage regulation of the distribution line under operation. Using the voltage measurement of the first load branch point and the last point on the given distribution line its average line voltage drop and the line voltage drop variance by pure load variation are computed. And by these values and allowable or required line drop from proper voltage regulation view point, present adequency index and operation improvement index of the line drop are newly introduced for the evaluation of the given distribution line's voltage regulation. As a result of application to the 4 cases of study, the proposed method is proved to be reliable and convenient.

• The Transactions of The Korean Institute of Electrical Engineers
• /
• v.67 no.1
• /
• pp.1-7
• /
• 2018

IEC 61000-3-7 provides guidance for limiting flicker and enabling the connection of fluctuating load installations, that is, producing flicker in MV, HV and EHV power systems. In Korea, the flicker have been restricted by Japanese standard of ${\Delta}V_{10}$ method. ${\Delta}V_{10}$ was developed only for arc furnaces in 1960's. And now it is revealed that it is not suitable for application to other fluctuating load installations through many researches. $P_{st}$ which is a flicker index used in IEC 61000-3-7, indicates visual inconvenience due to voltage fluctuation across large range of frequency and can be applied to fluctuating load installations as well as arc furnaces. In this paper, we introduce how to calculate and assess flicker emission level for the individual fluctuating load installations connected in EHV system and how to manage the emission levels in the power system according to IEC 61000-3-7.

• Journal of Power Electronics
• /
• v.19 no.6
• /
• pp.1554-1565
• /
• 2019

When grid voltage is unbalanced, the grid-connected output current and power of Virtual Synchronous Generators (VSGs) are distorted and quadratic. In order to improve the power quality of a grid connected to a VSG when the grid voltage is unbalanced, a comprehensive coordinated control strategy is proposed. The strategy uses the positive sequence current reference command obtained by a VSG in the balanced current control mode to establish a unified negative sequence current reference command analytical expression for the three objectives of current balance, active power constant and reactive power constant. In addition, based on the relative value of each target's volatility, a comprehensive wave function expression is established. By deriving the comprehensive wave function, the corresponding negative sequence current reference value is obtained. Therefore, the VSG can achieve the minimum comprehensive fluctuation under the premise that the three targets meet the requirements of grid connection, and the output power quality is improved. The effectiveness of the proposed control strategy is verified by simulation and experimental results.

• Journal of Power Electronics
• /
• v.13 no.5
• /
• pp.854-860
• /
• 2013

The voltage variation problem at the point of common coupling (PCC) in a grid-connected wind turbine is investigated. The voltage variation problem is one of the most frequent power quality issues for the grid connection of large amounts of input power in a weak grid. Through the simplified modeling of the wind turbine and power network, the magnitude of PCC voltage variation is calculated by using the equivalent circuit parameters and output power of the wind turbine. The required amount of reactive power that can compensate the voltage variation is also presented analytically by using the vector diagram method. The proposed calculation and compensation method of the PCC voltage variation is verified by computer simulations and experiments.

• Proceedings of the KIEE Conference
• /
• 2003.07e
• /
• pp.162-165
• /
• 2003

A resonant type voltage source and power device and a control method using Pulse Density Modulation(PDM) power control and Pulse Width Modulation(PWM)voltage control for plasma sterilization are described. For the stability of discharge in the generating tube, it is desirable that the peak apply voltage is constant. The PDM power control is employed for sustaining the voltage constant at any generating tube input power. Moreover, to avoid the influence of input AC voltage fluctuation etc., PWM voltage control with generating tube peak voltage feedback is used. Both functions were confirmed by the experiment with inverter and generating tube. The effect of input synchronous PDM method for input current stabilizing is confirmed also.

• Proceedings of the KIEE Conference
• /
• 2002.04a
• /
• pp.139-142
• /
• 2002

A resonant type voltage source and power device and a control method using Pulse Density Modulation(PDM) power control and Pulse Width Modulation(PWM) voltage control for Ozone Generator are described. For the stability of discharge in the generating tube, it is desirable that the peak apply voltage is constant. The PDM power control is employed for sustaining the voltage constant at any generating tube input power. Moreover, to avoid the influence of input AC voltage fluctuation etc., PWM voltage control with generating tube peak voltage feedback is used. Both functions were confirmed by the experiment with 6.5[kHz], 1.8[kW] inverter and generating tube. The effect of input synchronous PDM method for input current stabilizing is confirmed also.