• Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
• /
• v.27 no.7
• /
• pp.8-16
• /
• 2013

This paper investigates the electrical characteristics of popular power converters such as a half-bridge rectifier, a full-bridge rectifier, a buck converter, and an inverter when the arc is occurred at the input and the output of each converter. In order to generate an artificial arc, the arc generator has been implemented according to the design guideline suggested in UL1699. After that, the trend of the input and output voltage variation and the switching stress of the devices are analyzed. From the analysis, it has been confirmed that the generated arc causes an uncertain operation to the power converters. To reduce the unexpected disturbance effect of the arc, the capacitor adjustment method has been proposed, and its superiority has been experimentally verified.

• Proceedings of the KIEE Conference
• /
• 1999.07c
• /
• pp.1073-1075
• /
• 1999

This Paper Presents the process of load management for distribution Pole transformer at KEPCO. The purpose of this process is to establish reasonable peak load forecasting and prevention of Pole transformer damages caused by overload through the investigation of correlation coefficient for recent load characteristics. In this Paper, we newly proposed more reliable correlation coefficient using improved method and verified its reliability in various ways.

• Proceedings of the KIPE Conference
• /
• 2001.07a
• /
• pp.450-458
• /
• 2001

This paper deals with the translation and terminology adjustment of international standard IEC 60050-551 for international electrotechnical vocabulary in the field of power electronics. The standard has been prepared by IEC Technical Committee 22 : Power Electroncis, under the responsibility of IEC Technical Committee 1 : Terminology and is consists of 9 sections with 221 terms. This paper contains the results for 150 terms among them.

• Proceedings of the KIEE Conference
• /
• 2003.07d
• /
• pp.2690-2692
• /
• 2003

Amplifier linearity plays a major role in the design of mordern communication systems. An independently controllable AM/AM and AM/PM predistortion linearizers that consists of two bias feed resistance linearizers is proposed. This linearizer allows independent adjustment of the AM/AM and AM/PM curves by using two adjustable voltages to compensate the power amplifier non-linearities. The predistortion linearizer can improve the ACPR by SdB with cdma2000 multi carrier signals. By applying this linearizer to two-tone 880MHz power amplifier, an improvement of adjacent channel leakage power up to 5dBm has been achieved.

• Proceedings of the KIEE Conference
• /
• 1998.11a
• /
• pp.189-191
• /
• 1998

The development of the high- frequency induction-heating for 2700kW power range intend to make localization at forging and rolling mill part by technical innovation. And, the development makes to increase our's competitive power at technique, quality and cost. This paper describes the heart of high-frequency induction-heating technique, switching technique, a few problem in common using as an unsatisfied technique, load adjustment technique, system control, diagnostic system and auto-interface etc.

• The Transactions of the Korean Institute of Power Electronics
• /
• v.28 no.1
• /
• pp.1-7
• /
• 2023

A grid-connected 3-level NPC inverter is a power conversion device that connects renewable energy generators, such as photovoltaic or wind turbines to the grid. Although many studies have focused on this inverter, commercializing it requires strictly satisfying various safety and power quality-related standards. Among many standards, leakage current and grid current total harmonic distortion(THD) can be affected by external factors such as installation environment, aging, and grid conditions. Hence, inverter operations that can satisfy these standards need to be explored. In this study a 3-level NPC inverter operation algorithm using the Phase Opposition Disposition-PWM method that can effectively reduce leakage current and switching frequency adjustment to reduce THD effectively has been proposed.

• Journal of Power Electronics
• /
• v.16 no.6
• /
• pp.2327-2337
• /
• 2016

The mode-switching control of transient process is important to grid-connected 400 Hz solid-state power supply systems. Therefore, this paper analyzes the principle of on-grid and islanding operation of the system with or without local loads in the grid-connected process and provides a theoretical study of the effect of different switching sequences on the mode-switching transient process. The conclusion is that the mode switch (MS) must be turned on before the solid-state switch (STS) in the on-grid process and that STS must be turned off before the MS in the off-grid process. A strategy of mode-switching smooth control for transient process of the system is proposed, including its concrete steps. The strategy utilizes the average distribution of peak currents and the smooth adjustment of peak currents and phases to achieve a no-shock grid connection. The simulation and experimental results show that the theoretical analysis is correct and that the method is effective.

• Journal of the Korean Applied Science and Technology
• /
• v.37 no.4
• /
• pp.969-985
• /
• 2020

This study was conducted on 139 nursing students in their junior year of college in G City from October 29 to November 1, 2018, in order to identify the effects of personality type, academic stress and stress coping methods on college life adjustment. The results of the study showed that there were significant differences in college life adjustment (t=2.54, p=.012) according to gender (t=-3.55, p=.001), satisfaction of major (F=9.38, p<.001), satisfaction of interpersonal relationships (F=12.24, p<.001), and judging or perceiving (JP) among the MBTI preference pairs (t=2.54, p=.012). College life adjustment had a significant negative correlation with academic stress (r=-.56, p<.001). Factors that affected college life adjustment included academic stress (β=-.40, p<.001), satisfaction of interpersonal relationships (β=-.27, p<.001), and gender (β=.22, p=.002), and the explanatory power of these factors was 40.6%. Based on the findings of the study, it is necessary to develop and apply extracurricular programs to help nursing students reduce academic stress and improve their interpersonal relationships so that they can adjust well to college life.

• Journal of Electrical Engineering and Technology
• /
• v.12 no.6
• /
• pp.2268-2277
• /
• 2017

As constantly increasing wind power penetrates power grid, wind power plants (WPPs) are exerting a direct influence on the traditional power system. Most of WPPs are using variable speed constant frequency (VSCF) wind turbines equipped with doubly fed induction generators (DFIGs) due to their high efficiency over other wind turbine generators (WTGs). Therefore, the analysis of DFIG has attracted considerable attention. Precisely measuring optimum reference speed is basis of utilized maximum wind power in electric power generation. If the measurement of wind speed can be easily taken, the reference of rotation speed can be easily calculated by known system's parameters. However, considering the varying wind speed at different locations of blade, the turbulence and tower shadow also increase the difficulty of its measurement. The aim of this study is to design fuzzy controllers to replace the wind speedometer to track the optimum generator speed based on the errors of generator output power and rotation speed in varying wind speed. Besides, this paper proposes the fuzzy adaptive PID control to replace traditional PID control under rated wind speed in variable-pitch wind turbine, which can detect and analyze important aspects, such as unforeseeable conditions, parameters delay and interference in the control process, and conducts online optimal adjustment of PID parameters to fulfill the requirement of variable pitch control system.

• Proceedings of the KSME Conference
• /
• 2007.05b
• /
• pp.2528-2533
• /
• 2007

Thermoforming is one of the most versatile and economical processes available for the manufacturing polymer products. The drawback of thermoforming is difficult to get uniform thickness of final products. For the distribution of thickness strongly depends on the temperature distribution of sheet, the adjustment of heater power is very important In this paper, an optimization study for getting uniform temperature distribution was carried out using dual optimization steps. At first, the steady state optimal distribution of heater power is searched by numerical optimization to get uniform temperature of sheet surface. In the second step, time-dependent optimal heater inputs have been found out to decrease the temperature difference through the direction of thickness using Rseponse Surface Method and D-optimal method. The optimization results show that the time-dependent optimal heater power distribution gives acceptable uniform sheet temperature in the field of forming temperature..