• International Journal of Aeronautical and Space Sciences
• /
• 제17권4호
• /
• pp.631-640
• /
• 2016

A dual-mode power management for a hybrid-electric UAV with a cruise power of 200W is proposed and empirically verified. The subject vehicle is a low-speed long-endurance UAV powered by a solar cell, a fuel cell, and a battery pack, which operate in the same voltage bounds. These power sources of different operational characteristics can be managed in two different methods: passive management and active management. This study proposes a new power management system named PMS2, which employs a bypass circuit to control the individual power sources. The PMS2 normally operates in active mode, and the bypass circuit converts the system into passive mode when necessary. The output characteristics of the hybrid system with the PMS2 are investigated under simulated failures in the power sources and the conversion of the power management methods. The investigation also provides quantitative comparisons of efficiencies of the system under the two distinct power management modes. In the case of the solar cell, the efficiency difference between the active and the passive management is shown to be 0.34% when the SOC of the battery is between 25-65%. However, if the SOC is out of this given range, i.e. when the SOC is at 90%, using active management displays an improved efficiency of 6.9%. In the case of the fuel cell, the efficiency of 55% is shown for both active and passive managements, indicating negligible differences.

• 통합자연과학논문집
• /
• 제16권4호
• /
• pp.139-145
• /
• 2023

Due to changes in the distribution system and increased demand for renewable energy, interest in technology to increase the limit capacity of distributed energy grid connection using grid flexible resources is also increasing. Recently, the distribution system system is changing due to the increase in distributed power from renewable energy, and as a result, problems with the limited capacity of the distribution system, such as waiting for renewable energy to connect and increased overload, are occurring. According to the power generation facility status report provided by the Korea Power Exchange, of the total power generation capacity of 134,020 MW as of 2021, power generation capacity through new and renewable energy facilities is 24,855 MW, accounting for approximately 19%, and among them, power generation through solar power accounts for a total portion of the total. It was analyzed that the proportion of solar power generation facilities was high, accounting for 75%. In the future, the proportion of new and renewable energy power generation facilities is expected to increase, and accordingly, an efficient operation plan for the distribution system is needed. Advanced country-type NWAs that can integrate the operation and management of load characteristics for each line of the distribution system, power distribution, regional characteristics, and economic feasibility of distributed power in order to improve distribution network use efficiency without expanding distribution facilities due to the expansion of renewable energy. An integrated operating system is needed. In this study, in order to improve the efficiency of distribution network use without expanding distribution facilities due to the expansion of renewable energy, we developed a method that can integrate the operation and management of load characteristics for each line of the distribution system, power distribution, regional characteristics, and economic feasibility of distributed power. We want to develop an integrated operation system for NWAs similar to that of advanced countries.

• 조명전기설비학회논문지
• /
• 제26권8호
• /
• pp.18-26
• /
• 2012

Recently, there have been suggestions that power factor should be considered to increase the efficiency of electric power supply when evaluating the performance of the electric appliances in standby mode and the related studies have been conducted to improve the efficiency standard of standby power. But, they lack the analysis of the standby power characteristics with the changes of power factor. This study is conducted to analyze the standby power characteristics of TV which is a typical home appliance and reaches a conclusion that the apparent power can be a more reasonable index which reflects the efficiency of electric power supply. It is also found that LED TVs show the best performance in standby mode. Moreover, an example to set standby power standards on TVs to be applied in the future is suggested, considering the energy efficiency policies for appliances.

• KIEE International Transactions on Power Engineering
• /
• 제5A권1호
• /
• pp.56-61
• /
• 2005

This paper presents an evaluation of the interruption costs for commercial customers in Korea using customer survey methodology. When various research results are examined, the evaluation of direct interruption costs becomes much more simplified. Especially, in the case of commercial customers, it is known that the evaluation of direct interruption costs is more useful. Accordingly, this paper selected the customer survey method to evaluate the interruption costs for commercial customers in Korea considering interruption and customer characteristics.

• 한국안전학회지
• /
• 제16권1호
• /
• pp.25-30
• /
• 2001

This paper studies the effect of vibration characteristics of tube line conveying fluid with the power steering system of bus. We modelled fluid-filled tube line using I-DEAS software to investigate vibration characteristics of the power steering tube line. And we obtained the natural frequency of tube line through finite element analysis. Analytic solutions were compared with experimental solutions to verify finite element model. We tested the tube line to examine an effect of pressure pulse by vane pump and variation of geometry of tube. From both the experimental results and the modeling results for vibration characteristics of the tube line conveying fluid, we confirmed that vibration characteristics induced by pulse propagated along the power steering tube line and resonance occurred around the natural frequency with pulse excitation.

• 전기학회논문지
• /
• 제56권5호
• /
• pp.884-891
• /
• 2007

Comparing with the conventional transformer without the air gap, a contact-less transformer with the large air-gap (4.8cm) between the long primary winding and the secondary winding has the increased leakage inductance and the reduced magnetizing inductance. By the increased leakage inductance and the reduced magnetizing inductance on the primary of the contact-less transformer, a good deal of the primary current circulates through magnetizing inductance, which results in a massive loss and the high voltage gain characteristics for load variations in contact-less power supply (CPS). To consider these characteristics, in this paper, the efficiency characteristics of the contact-less power supply using a series resonant converter is presented, described and verified through theoretical analysis, computer simulation and experimental test of 2.5kW prototype.

• 대한전기학회논문지:전력기술부문A
• /
• 제48권11호
• /
• pp.1410-1416
• /
• 1999

This paper aims at investigating the operating-mode characteristics of two-module Thyristor Controlled Series Compensator (TCSC) as an equivalent of the multi-module TCSC in a simple three-phase power transmission system. The load flow program is developed to analyze the steady-state characteristics of two-module TCSC system and to find the thyristor firing angles for the required real power flow. The stability calculation program is developed with Poincare mapping theory. Simulation studies of the TCSC power transmission system using EMTP are performed to evaluate the transient characteristics of two-module TCSC as a real power flow controller and to rpove the results of the load flow calculation and the stability analysis. In the process of the study, the operating-mode characteristics of two-module TCSC are evaluated and compared to those of single-module TCSC.

• 한국의류산업학회지
• /
• 제8권5호
• /
• pp.513-522
• /
• 2006

The purpose of this study was to analyze characteristics and meanings of the masculine factors related with power images in women's fashion since 2000. The method of study was to analyze the documentary about the power images since the 14th Century and then the fashion magazines since 2000. The results of this study were as follows: The power image of women's fashion was internalized by wearing of the masculine factors each of an era. After 2000, characteristics of women's fashion affected by masculine factors were an exaggeration of scale, deformation, inharmonious collage and changeful borrowing. They showed the structure of new cognition of modern society uncertainty, open and decentralized. And power images presented aesthetic characteristics such as independence, ideal, sign of a amusement and decentralized virility. In conclusion, power in women's fashion has a function of creativeness, product, positiveness from past to modern. In addition, the power, which is a symbol of perfection, rationality and ideal beauty, expresses a good feeling of psychology, social friendship, value of success and will be existed as a meaningful esthetic sign in women's fashion.

• 한국통신학회논문지
• /
• 제18권4호
• /
• pp.499-508
• /
• 1993

이 논문에서 CATV 및 MATV시스템용으로 널리 쓰이는 전력분배기의 설계법과 주파수특성해석을 다루고 있다. 즉, 윌킨슨형 파워디바이더를 집중정수회로화하여 CATV주파수대에 적합한 2분배기의 설계법을 이론적으로 고찰하고, 주파수특성을 해석하고 있다. 윌킨슨형 파워디바이더의 분배특성을 향상시키기 위해 보상회로를 부가한 최적설계법을 제시하여 특성평가를 하였으며, 그 결과 특성이 크게 향상됨을 이론적인 고찰과 실험을 통하여 증명하였다.

• 한국전기전자재료학회논문지
• /
• 제36권4호
• /
• pp.385-390
• /
• 2023

In this paper, the 1,700 V level SiC-based power MOSFET device widely used in electric vehicles and new energy industries was designed, that is, a single trench gate power MOSFET structure and a double trench gate power MOSFET structure were proposed to analyze electrical characteristics while changing the design and process parameters. As a result of comparing and analyzing the two structures, it can be seen that the double trench gate structure shows quite excellent characteristics according to the concentration of the drift layer, and the breakdown voltage characteristics according to the depth of the drift layer also show excellent characteristics of 200 V or more. Among them, the trench gate power MOSFET device can be applied not only to the 1,700 V class but also to a voltage range above it, and it is believed that it can replace all Si devices currently applied to electric vehicles and new energy industries.