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A New Three Winding Coupled Inductor-Assisted High Frequency Boost Chopper Type DC-DC Power Converter with a High Voltage Conversion Ratio

  • Ahmed Tarek;Nagai Shinichiro;Hiraki Eiji;Nakaoka Mutsuo
    • Journal of Power Electronics
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    • v.5 no.2
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    • pp.99-103
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    • 2005
  • In this paper, a novel circuit topology of a three-winding coupling inductor-assisting a high-frequency PWM boost chopper type DC-DC power converter with a high boost voltage conversion ratio and low switch voltage stress is proposed for the new energy interfaced DC power conditioner in solar photovoltaic and fuel cell generation systems. The operating principle in a steady state is described by using its equivalent circuits under the practical condition of energy processing of a lossless capacitive snubber. The newly-proposed power MOSFET boost chopper type DC-DC power converter with the three-winding coupled inductor type transformer and a single lossless capacitor snubber is built and tested for an output power of 500W. Utilizing the lower voltage and internal resistance power MOSFET switch in the proposed PWM boost chopper type DC-DC power converter can reduce the conduction losses of the active power switch compared to the conventional model. Therefore, the total actual power conversion efficiency under a condition of the nominal rated output power is estimated to be 81.1 %, which is 3.7% higher than the conventional PWM boost chopper DC power conversion circuit topology.

A Study on Photovoltaic/Wind/Diesel Hybrid Power System

  • Jeong, Byung-Hwan;Cho, Jun-Seok;Gho, Jae-Seok;Choe, Gyu-Ha;Kim, Eung-Sang;Lee, Chang-Sung
    • Journal of Power Electronics
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    • v.3 no.1
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    • pp.40-48
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    • 2003
  • In this paper, a hybrid power system with photovoltaic/wind/diesel generators is proposed to solve the defect of stand-alone type power system in a remote area. A hybrid power system has a power-balanced controller to equilibrate generation power with a given load demand and which is composed of common DC power system. To execute a power-balanced control, a hybrid power system is assumed that all of power generators have the characteristics of an equivalent current-source and load sharing control technique must be needed at the same time. So this paper discusses the structure of power-balance control for hybrid power system. And through the results of simulation, the proposed scheme was verified.

Power Line Communication Method with Splitting of Power Transmission Interval (전력전송구간을 분할하여 데이터 신호를 전송하는 전력선 통신방법)

  • Cho, Jae-Seung;Hwang, Il-Kyu
    • The Transactions of the Korean Institute of Power Electronics
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    • v.17 no.3
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    • pp.252-258
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    • 2012
  • This paper studies the power line communication method with splitting of power transmission interval in the small DC power system using pulse width modulation. The method divides the entire interval for transmitting power and data into a power transmission interval where power is supplied to a load and a data transmission interval where power from the power supply to the load is disconnected. The circuit is designed for the implementation to separate the power line from the power supply and load. The results of tests show the feasibility of the proposed power line communication method.

A Study on the Relationship between Nurses Relative Power and Interpersonal Conflicts (간호사의 상대적 권력과 대인갈등)

  • 이명옥
    • Journal of Korean Academy of Nursing
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    • v.27 no.1
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    • pp.169-177
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    • 1997
  • This study aims at empirically clarifying the relationship between power and the interpersonal conflict, including nurses' understanding of their relative power, the causes of interpersonal conflicts with the nurses, and strategies to resolve conflicts, in order to understand how nurses' relative power affect their conflicts. For the empirical survey, the population was defined as all the nurses working at a medical organization in Seoul, Korea. 1083 nurses were selected as the sample for the questionnaire survey and statistical analyses. For the sampling, 32 medical organizations were selected by a stratified random method and sub-samples were arbitrarily drawn from each organization to obtain the final sample of 1083 nurses who responded to the questionnaire designed by the reseacher. According to the result of the study, most nurses experience conflict more than once a month, and 70.4% of the respondents answered that interpersonal conflicts were directly or indirectly caused by power relations. which indicates that they perceive power relations as the main cause of interpersonal conflicts. Nurses experienced the most conflicts with interns and residents(29.7%), then patients and their families(24.3%), higher-positioned nurses(12.3%), nurse colleagues(7.7%), lower-positioned nurses(6.5%), and staff doctors(5.1%). If we classify these into three groups. the frequency of the conflicts, from most frequent to least. is in the order of doctors. nurses, and patients. In terms of relative power, nurses perceive that they have greater power than patients and their families, lower-positioned nurses, and nurse colleagues. In contrast, nurses perceive that they have less power than interns and residents, higher-positioned nurses. and staff doctors. Among these groups. nurses perceive that they have the most power over patients and the least over staff doctors. These results indicate that nurses tend to experience more conflicts with members of groups that are stronger than themselves in terms of relative power, Nurses use positive strategies such as the compromise strategy(32.3%) or the collaboration strategy (20.3%) to manage conflicts, more than other strategies. However, they use avoidance or competition strategy more at the earlier stage, compromise strategy more in the mid stage, and collaboration strategy more at the later stage of the interpersonal conflict. In relation to power, nurses use the collaboration strategy or the compromise strategy more when their perceived power is greater than or equal to their counterpart's, and they use the avoidance strategy or the accommodation strategy if their power is less. In terms of source of power, nurses' perceived relative power is greater in the order of referent power. expert power, reward power, legitimate power. and coercive power. where referent power is perceived as having the greatest power and coercive power is least. Most nurses(69.3%) used their power to resolve a conflict. with positive outcomes. Expert power was used most frequently. Overall. this study strongly indicates that the enhancement of power of nurses to have equal power relations with doctors would heighten the success of conflict resolution, since power is the main cause of conflicts. Specifcally. nurses experience most conflicts with doctors against whom they perceive the greatest gap in power. and the choice of a conflict management strategy depend upon their power relations.

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Design and Process Development in High Voltage Insulated Gate Bipolar Transistors (IGBTs)

  • Kim, Su-Seong
    • The Magazine of the IEIE
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    • v.35 no.7
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    • pp.57-71
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    • 2008
  • The last decade has witnessed great improvements in power semiconductor devices thanks to the advanced design and process, which have made it possible to significantly improve the electrical performances of electronic systems while simultaneously reducing their site, weight and perhaps most importantly reducing their cost. Among the power semiconductor devices, IGBT will be a key semiconductor component for power industry since it has a huge potential to cover large areas of power electronics from small home appliances to heavy industries. Currently, only a few limited power semiconductor manufacturers supply most of the industrial consumptions of power IGBT and its modules. Therefore, a large portion of technology in the power industry is dependent on other advanced countries. In this regard, to independently build power IGBT devices and the relevant power module technology, Korean government initiated a new 5-year project 'Power IT,' which also aimed at booming the business of the power semiconductor and the allied industries. With the success of this power IT project, it is expected that the power semiconductor technology will be a basis to foster the high power semiconductor industry and moreover, there will be more innovative developments in the Korea region and globally Also, forming the channel between the customers and suppliers, it is possible to effectively develop the customized power products, which could strengthen the competitiveness of Korean power industry. Furthermore, the power industry including semiconductor manufacturers will be technologically self-supporting and be able to obtain good business opportunities, and eventually increase the share in the growing power semiconductor market, which could be positioned as a major industry in Korea.

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A Study on the Compensation of Reactive Power by Power MOSFET INVERTER (전력용 MOSFET Inverter에 의한 무방전력보상에 관한 연구)

  • 이계호;김동필
    • The Transactions of the Korean Institute of Electrical Engineers
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    • v.36 no.3
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    • pp.163-170
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    • 1987
  • It is known that reactive component of AC power in the power system gives no energy to outside and cuses enlargiment of power apparatus, voltage fluctuation and unstability of power system. The power conversion system and control system which are composed of power semiconductor devices such as tyristor, transistor, GTO and so on have been appeared as new sources of reactive power. So the cmpensation of reactive power in power semiconductor systems is one of impending problem on the point of energy conservation and inprovement of power factor. This paper treates the fundamental review of the current type power compensation system that compensates the reactive power by MOSFET inverter. This inverter detects not only the reactive power of fundamental wave but also that of all harmoics created in the power semiconductor system and is scheduled to control by sampled value.

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A Study on the Improving Power System Reliability According to the Reactive Power Problem in the Bulk Power Station (대전원단지의 무효전력 출력제약에 따른 영향에 대한 연구)

  • Song, Seok-Ha;Joo, Joan-Young
    • Proceedings of the KIEE Conference
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    • 2002.11b
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    • pp.73-75
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    • 2002
  • This paper presents the properly method of system security and facility countermeasures. We performed simulation for yearly peak of Korean power system in 2002 under the reactive power problem in a nuclear power plants. Analysis of the problems in power system operation by power flow, fault and stability study. Establishment of power system optimal operating plan by stabilizer and maintaining the reasonable voltage level.

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A Study on the Effective Enhancement of the Load Power Factor Using the Load Power Factor Sensitivity of Generation Cost and Integrated Costs (발전비용의 부하역률 감도와 종합비용을 활용한 효과적인 역률개선 방안 연구)

  • Lee, B.H.;Oh, M.H.;Kim, J.H.;Shim, K.B.
    • Proceedings of the KIEE Conference
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    • 2003.11a
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    • pp.284-286
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    • 2003
  • The low load power factor causes various problems such as the Increase of the power loss and the voltage instability. The demand of reactive power increases continuously with the growth of active power and the restructuring of electric power companies makes the integrated management of ractive power troublesome, from which the systematic control of load power factor is required. In this paper, the load power factor sensitivity of the generation cost and integrated costs are used for determining the locations and capacities of reactive power compensation devices effectively and for enhancing the load power factor appropriately. It is shown through the application to a small-scale power system that the system power factor can be enhanced effectively and appropriately using the load power factor sensitivity and integrated costs.

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A Study on the Effective Enhancement of the Load Power Factor Using the Load Power Factor Sensitivity of Generation Cost (부하역률 감도기법 적용에 의한 효율적인 부하역률 개선에 관한 연구)

  • Lee Byung Ha;Kim Jung-Hoon
    • The Transactions of the Korean Institute of Electrical Engineers A
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    • v.54 no.1
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    • pp.18-24
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    • 2005
  • Various problems such as the increase of the power loss and the voltage instability may often occur in the case of low load power factor. The demand of reactive power increases continuously with the growth of active power and the restructuring of electric power companies makes the comprehensive management of reactive power a troublesome problem, so that the systematic control of load power factor is required. In this paper, the load power factor sensitivity of the generation cost is derived and it is used for determining the locations of reactive power compensation devices effectively and for enhancing the load power factor appropriately. In addition, the voltage variation penalty cost is introduced and the integrated costs including the voltage variation penalty cost are used for determining the value of the load power factor from the point of view of the economic investment and voltage regulation. It is shown through the application to a large-scale power system that the load power factor can be enhanced effectively and appropriately using the load power factor sensitivity and integrated costs.

A Study on Determining an Appropriate Power Trading Contracts to Promote Renewable Energy Systems

  • Choi, Yeon-Ju;Kim, Sung-Yul
    • International Journal of Precision Engineering and Manufacturing-Green Technology
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    • v.5 no.5
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    • pp.623-630
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    • 2018
  • The renewable energy systems have been in the spotlight as an alternative for environmental issues. Therefore, the governmental policies are being implemented to spread of promote power generation system using renewable energy in various countries around the world. In addition, Korea has also developed a policy called the power trading contract which can profit from electricity produced from renewable power generation system through Korea Electric Power Corporation (KEPCO) and Korea Power Exchange (KPX). As a result, the power trading contracts can trade power after self-consuming in-house by using small-scale renewable power system for residential customers as well as electricity retailers. The power trading contracts applicable as a small-scale power system have a 'Net metering (NM)' and a 'Power Purchase Agreement (PPA)', and these two types of power trading contracts trade surplus power, but payment method of each power trading is different. The microgrid proposed in this paper is based on grid connected microgrid using Photovoltaic (PV) system and Energy Storage System (ESS), that supplied power to residential demand, we evaluate the operation cost of microgrid by power demand in each power trading contracts and propose the appropriate power trading contracts according to electricity demand.