• Title/Summary/Keyword: UPS systems

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A New Control Scheme of the Line-Interactive UPS Using the Series Active Compensator (직렬 능동 보상기를 이용한 Line-Interactive UPS의 새로운 제어 기법)

  • Jang, Hoon;Lee, Woo-Cheol;Hyun, Dong-Seok
    • The Transactions of the Korean Institute of Electrical Engineers B
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    • v.52 no.8
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    • pp.405-412
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    • 2003
  • This paper presents a three-phase Line-Interactive uninterruptible power supply (UPS) system with series-parallel active power-line conditioning capabilities, using synchronous reference frame (SRF) based controller, which allows an effective power factor correction, source harmonic voltage compensation, load harmonic current suppression, and output voltage regulation. The three-phase UPS system consists of two active power compensator topologies. One is a series active compensator, which works as a voltage source in phase with the source voltage to have the sinusoidal source current and high power factor under the deviation and distortion of the source voltage. The other is a parallel active compensator which works as a conventional sinusoidal voltage source in phase with the source voltage, providing to the load a regulated and sinusoidal voltage with low THD (total harmonic distortion). The control algorithm using SRF method and the active power flow through the Line-interactive UPS systems are described and studied. The simulation and experimental results are depicted in this paper to show the effect of the proposed algorithm.

The Research on the Indoor Temperature and Humidity Control of Green Roof by Solid Growing Medium in Summer (고형화된 식생기반재를 활용한 여름철 옥상녹화의 실내 온·습도 조절효과 연구)

  • Lee, Hyun-Jung;Yeom, Dongwoo;Lee, Kyu-In
    • KIEAE Journal
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    • v.15 no.3
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    • pp.93-99
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    • 2015
  • Purpose: Various studies on the soil-based green roof systems have been conducted, and a lot of green roof systems were developed. A growing medium board is one of them which was developed for better application and maintenance, however the effect and performance of this material need to be verified. On this background, the purpose of this study is to prove cooling load reduction of green roof by monitoring experiment on the full-scale mock-ups. Method: To do this, Solid growing medium boards were installed on the mock-ups, and indoor temperature and humidity were monitored and analyzed. Result: As a results, the green roof with solid growing medium board were verified effective for controlling indoor temperature in summer.

The Influence of Entrepreneurial Competences on Corporate Performance of Technology-based Start-ups (창업가역량과 창업보육 프로그램 지원이 기술창업기업 경영성과에 미치는 영향 : 창업기업 역량의 매개효과 중심으로)

  • Kim, Jinhan;Cho, Jinhyung;Lee, Saejae
    • Journal of Korean Society of Industrial and Systems Engineering
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    • v.43 no.1
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    • pp.132-142
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    • 2020
  • Many countries around the world are pursuing various support policies to foster start-ups national widely in order to secure new economic growth engines in the era of the Fourth Industrial Revolution. The South Korean government announced the diffusion strategy for the 2'nd round Start-up Boom in March 2019 and is promoting the support policies for start-up incubating by various programs. Many incubators and startup accelerators operate various kinds of programs to foster start-ups using government financial supports. The purpose of this study is to investigate the effects of entrepreneurship and technical capability of entrepreneurs as the internal factors of the technology-based start-ups and the effects of programs supported by the government as an external factor on the corporate performance of a start-up company, and the mediating effects of core competence of start-ups were analyzed using SPSS and AMOS. The results show that the entrepreneurship, technical capability and the programs supported by incubators or accelerators had no direct effects on the corporate performance of a start-up, but the core competence of the company had complete mediating effects. In addition, the type of program supported by the comprehensive accelerator programs or the marketing supports had effects on the core competence rather than simple financial supports. Lastly, the policy proposals for incubating program support and future research directions along with the limitation are suggested.

Evaluation of the fracture resistance of all-ceramic zirconia posts by 3 different methods

  • Jeong, Seung-Mi;Chung, Chae-Heon;Kang, Dong-Wan;Ludwig, Klaus;Kern, Matthias;Huels, Alfons
    • The Journal of Korean Academy of Prosthodontics
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    • v.38 no.6
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    • pp.757-764
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    • 2000
  • Statement of the problem. All-ceramic post-and-core restorations offer a number of advantages compared with systems that use metal build-ups. In certain clinical cases, however, fractures at the joint between the post and core build-up have been reported. Purpose. The objective, therefore, is to improve the joint between the post and the core build-up. Material and methods. Three different methods were used to prepare all-ceramic post-and-core restorations; pressing IPS Empress core build-ups to CosmoPost zirconia posts, cement-ing IPS Empress core build-ups to CosmoPost zirconia posts and Celay-milling of zirconia blanks. A series of ten restorations was prepared for each of the three methods. The post-and-core complexes were tested to failure with the load applied perpendicular to the post axis. The load and deflection at fracture were recorded. Results. The highest breaking load and highest deflection were recorded for the cementing technique with values of 25.3 N and $394{\mu}m$, respectively, The corresponding values for the pressed core build-ups and the milled zirconia core build-ups were 22 N and $301{\mu}m$, and 13 N and $160{\mu}m$, respectively. All the differences are statistically significant (p=0.05). Regarding the load-dependence of the deflection, the cemented core build-ups again demonstrated the highest value with $15.5{\mu}m/N$. The difference in the values of $13.6{\mu}m/N\;and\;13{\mu}m/N$ recorded for the pressed-on and milled core build-ups, respectively, were statistically insignificant. Conclusion. In regard to the high fracture resistance of zirconia post, adhesive cementing the core build-up to the post offers a viable alternative to the conventional pressing technique. The elastic bond between the rigid high-strength zirconia post and the core build-up presents an additional advantage.

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Design and Control Method for Critical Load Supply Equipment using MCFC Electricity Generation Systems (대용량 MCFC 발전시스템을 이용한 비상부하 전력 공급 장치 설계 및 제어방법)

  • Kim, Dong-Hee;Kim, Jong-Soo;Choe, Gyu-Yeong;Lee, Byoung-Kuk;Kawk, Cheol-Hoon
    • The Transactions of the Korean Institute of Power Electronics
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    • v.16 no.1
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    • pp.20-29
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    • 2011
  • This paper proposes critical load following back-up system using MCFC stack. This system enables MCFC generation system to supply power to critical load without UPS and to generate rated power under grid fault state. This back-up system includes 'Load Leveler' that is connected with 3-phase inverter and is controlled by additional algorithm that includes critical load following. The proposed system and algorithm are verified by computer simulation based on 5kW system.

A Study on Standardization of UPS (Uninterruptible Power Supply) for Traffic Signal Controller (교통신호제어기용 무정전전원장치 용량기준 연구)

  • Ko, Kwang-Yong;Lee, Choul-Ki;Kim, Min-Sung;Heo, Nak-Won;Jeong, Jun-Ha
    • The Journal of The Korea Institute of Intelligent Transport Systems
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    • v.11 no.5
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    • pp.1-6
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    • 2012
  • Unlike the past, modern urban intersections have dramatic growth in size and utilizations. As a result, continual traffic signal control is essential. Hence the individual or regional electrical blackout may bring about uncontrollable traffic congestion. Late summer of 2011 a regional blackout brought about traffic nightmare not including time and revenue loss associated with this disaster. Due to this disaster our national police agency and other government agencies are in process of introducing an UPS (uninterruptible power supply) system into essential intersections. This study estimates the power consumption necessary to sustain at least 2 continuous hours for a standard four-legged intersection. Prototype was studied using these standards. The field experiment of prototype showed positive results and was able to meet standard guidelines set forth. Prototype tested was able to meet standards in medium to large capacity of traffic size.

Model Predictive Control of Three-Phase Inverter for Uninterruptible Power Supply Applications under a Hexagonal Input Constraint Region (육각형 입력제약 공간을 이용한 무정전 전원장치의 모델예측제어)

  • Kim, Seok-Kyoon;Kim, Jung-Su;Lee, Young Il
    • Journal of Institute of Control, Robotics and Systems
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    • v.20 no.2
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    • pp.163-169
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    • 2014
  • Using the classical cascade voltage control strategy, this paper proposes an analytical solution to an MPC (Model Predictive Control) problem with a hexagonal input constraint set for the inner-loop to regulate the output voltage of the UPS (Uninterruptible Power Supply). Focus is placed on how to deal with the hexagonal input constraint set without any approximation. Following the conventional cascade voltage control strategy, the PI (Proportional-Integral) controller is used in the outer-loop in order to regulate the output voltage. The simulation results illustrate that the capacitor voltage rapidly goes to its reference in a satisfactory manner while keeping other state variables bounded under an unexpected load changes.

Workflow Oriented Domain Analysis (워크플로우 지향 도메인 분석)

  • Kim Yun-Jeong;Kim Young-Chul
    • The Journal of the Korea Contents Association
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    • v.6 no.1
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    • pp.54-63
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    • 2006
  • In this paper we will propose a domain analysis methodology that uses an extended workflow mechanism based on dynamic modeling to solve problems of a traditional domain analysis on legacy systems. This methodology is called WODA(Workflow Oriented Domain Analysis). Following procedures on WODA, we can identify common/uncommon component, and also extract the cluster of components. It will be effectively reusable on developing new systems with these components. With our proposed component testing metrics, we can determine highly reusable component/scenario on identifying possible scenarios of the particular system. We can also recognize most critical/most frequent reusable components and prioritize possible component scenarios of the system. This paper contains one application of UPS that illustrates our autonomous modeling tool, WODA.

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A Study on the Uninterruptible Power Supply(UPS) System with Superconducting, Magnet Energy Storage(SMES) (초전도 에너지 저장장치를 이용한 무정전 전원장치 시스템의 연구)

  • Kim, Tae-Wan;Ji, Ho-Chul;Jeong, Seung-Gi
    • Proceedings of the KIEE Conference
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    • 1997.07f
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    • pp.1919-1923
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    • 1997
  • Superconducting magnet energy storage(SMES) offers lower loss and more capacity than other energy storage systems. This paper deals with a configuration and a control method of uninterruptible power supply(UPS) with SMES, Proposed system is constituted of three partsinverter, dc chopper and superconducting coil. The control system is implemented with a general-purpose DSP, TMS320C31. The results of simulation and experiment with a 10kVA prototype show the validity of the system configuration and the control method.

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Quench Characteristics of the Superconduction Cable for a 0.7 MJ UPS (0.7 MJ UPS용 초전도 케이블의 ?치 특성)

  • 류경우;김해종
    • Journal of the Korean Institute of Electrical and Electronic Material Engineers
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    • v.11 no.7
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    • pp.565-570
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    • 1998
  • Recently a few MJ superconducting magnetic energy storage ($\mu$ SMES) devices become commerci-ally available as one of the energy storage devices for uniterruptible power supply (UPS) systems. For such a ($\mu$ SMES) devics, a few kA class superconducting cables with high current density, high stability and excellent pulse characteristics are required. To acquire data for the superconduction cables related to design and fabrication of a 0.7 MJ $\mu$ SMES device, we tested critical currents and quench characteristics for several winding tensions and various remping rates especially. It is shown from the results that winding tensions have much influence on quench currents of the $\mu$ SMES devices.

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