• KIEE International Transaction on Electrical Machinery and Energy Conversion Systems
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• 제4B권3호
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• pp.114-121
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• 2004

Switched reluctance motors have received much attention as a driving means for various industrial applications because they have simple construction, low cost and high efficiency. Nevertheless, the requirements of drive converters make it difficult to lower the overall system cost as compared with the DC motor application. Single phase switched reluctance motors (SPSRMs) provide a solution to the high cost problem since the number of switching power devices can be reduced and consequently the trials for application are increased. However, research involving SPSRMs, especially in the area of design work, is insufficient. This paper introduces a novel design methodology of single phase SRM. The design work for SPSRM comprises the determination of many variables such as stator and rotor pole arc as well as on, off and so on. Managing all variable combinations leads to lengthy computation time and a fault in the design process. For that reason, a reliable technique and brief procedure term are required in SPSRM design.

• 산업경영시스템학회지
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• 제23권54호
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• pp.27-36
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• 2000

The problem of discovering association rules is an emerging research area, whose goal is to extract significant patterns or interesting rules from large databases and several algorithms for mining association rules have been applied to item-oriented sales transaction databases. Data warehouses and OLAP engines are expected to be widely available. OLAP and data mining are complementary; both are important parts of exploiting data. Our study shows that data cube is an efficient structure for mining association rules. OLAP databases are expected to be a major platform for data mining in the future. In this paper, we present an efficient and effective algorithm for mining association rules using data cube. The algorithm can be applicable to enhance the power of competitiveness of business organizations by providing rapid decision support and efficient database marketing through customer segmentation.

• 에너지공학
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• 제26권4호
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• pp.57-66
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• 2017

열은 전력과 같이 이동속도가 빠르지 못하고 전력에 비해 손실이 비교적 크게 발생하므로 전력거래와 같이 한개의 운용센터를 두고 열 연계 시스템을 운용하는 것은 현실성이 없다. 현재 열 연계가 모두 이루어지고 있는 한국지역난방공사의 경우에도 인접한 2~4개 정도의 열병합발전소간에만 열 거래가 이루어지고 있는 실정이다. 따라서 본 논문에서는 열 거래를 위한 통합운용센터를 몇 개의 권역으로 나누어 각 권역마다 권역의 Hub 통합운용발전소를 두고 운용하는 것이 열매체의 특성을 반영하는데 적정하고 타당한 것으로 판단하여 집단에너지 사업자간 열 연계 메커니즘을 제안하였다. 제안된 메커니즘에 최적으로 열 거래를 행할 수 있는 알고리즘을 개발하고 이를 실제 사업자에 적용하여 제안한 알고리즘의 유용성을 검증하였다.

• 수산경영론집
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• 제51권4호
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• pp.137-146
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• 2020

In this study, the differences of institutional development processes of fishery products wholesale markets were compared between Korea and Japan in order to suggest improvement direction of trading system in Korea. The wholesale markets have shrunk while wholesale and distribution has been becoming larger in size in both countries. A summary of differences in the wholesale market trading systems between Korea and Japan is as follows: first, middle wholesalers play pivotal roles in wholesale transaction in Korea, and wholesale corporations take such roles in Japan. Second, most wholesale corporations take charge of listing in Korea whereas such corporations are in charge of buying in Japan. Third, Korea has high proportion of auction for transactions, in contrast to Japan with high proportion of relative transactions. Forth, Korea maintains more sales within the wholesale markers and has more small and medium customers than Japan. Finally, Korea investigates inside causes to find solutions for the decreased competitive power of the wholesale market, whereas Japan copes with the problem by searching for outside customers. To seek solutions for the decreased competitiveness of Korean fishery products wholesale markets, middle wholesalers' consignment should be limitedly allowed, and improvement direction of wholesale corporations should be investigated in the future study.

• 정보보호학회논문지
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• 제29권1호
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• pp.225-234
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• 2019

비트코인은 탈중앙화와 분산원장을 특징으로 하는 암호화폐로서 "작업증명"이라는 채굴시스템을 통해 유지된다. 채굴 시스템에서는 블록 생성시간을 일정하게 유지하기 위해 채굴 난이도를 조정하게 되는데, 기존의 채굴 난이도 변경 방식은 미래의 해시파워를 반영할 수 없다는 문제가 있다. 따라서 실제시간과 예정시간 사이에 발생하는 오차로 인해 블록생성과 실세계 시간의 불일치를 가중시키게 되고, 결국 거래 기한을 맞추지 못하거나 코인 호핑 공격에 취약점을 노출시키게 된다. 블록 생성시간을 일정하게 유지시키기 위한 기존 연구도 여전히 오차 문제를 갖는다. 본 연구에서는 이러한 오차를 줄이기 위한 기계학습 기반 채굴 난이도 예측 방안을 제시한다. 이전 해시파워를 학습하여 미래의 해시파워를 예측하고 예측한 값을 이용하여 채굴 난이도를 조정한다. 우리의 실험 결과는 이와 같은 경우 기존 채굴 난이도 조정방식보다 오차율을 약 36% 더 줄일 수 있음을 보여준다.

• KIEE International Transaction on Electrical Machinery and Energy Conversion Systems
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• 제3B권1호
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• pp.10-15
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• 2003

This paper presents the digital computer performance evaluations of the three-phase self-excited induction generator (SEIG) driven by the variable speed prime mover such as the wind turbine using the nodal admittance approach steady-state frequency domain analysis with the experimental results. The three-phase SEIG setup is implemented for small-scale rural renewable energy utilizations. The experimental performance results give a good agreement with those ones obtained from the digital computer simulation. Furthermore, a feedback closed-loop voltage regulation of the three-phase SEIG as a power conditioner which is driven by a variable speed prime mover employing the static VAR compensator (SVC) circuit composed of the thyristor phase controlled reactor (TCR) and the thyristor switched capacitor(TSC) is designed and considered herein for the wind-turbine driven the power conditioner. To validate the effectiveness of the SVC-based voltage regulator of the terminal voltage of the three-phase SEIG, an inductive load parameter disturbances in stand-alone are applied and characterized in this paper. In the stand-alone power utilization system, the terminal voltage response and thyristor triggering angle response of the TCR are plotted graphically. The simulation and the experimental results prove the effectiveness and validity of the proposed SVC which is controlled by the Pl controller in terms of fast response and high performances of the three-phase SEIG driven directly by the rural renewable energy utilization like a variable-speed prime mover.

• International Journal of Computer Science & Network Security
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• 제21권4호
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• pp.255-263
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• 2021

Smart grid is a fully-automated, bi-directional, power transmission network based on the physical grid system, which combines sensor measurement, computer, information communication, and automatic control technology. Blockchain technology, with its security features, can be integrated with Smart Grids to provide secure and efficient power management and transmission. This paper dicusses the deployment of Blockchain technology in Smart Grid. It presents application areas and protocols in which blockchain can be applied to in securing smart grid. One application of each area is explored in detail, such as efficient peer-to-peer transaction, lower platform costs, faster processes, greater flexibility in power generation to transmission, distribution and power consumption in different energy storage systems, current barriers obstructing the implementation of blockchain applications with some level of maturity in financial services but concepts only in energy and other sectors. Wide range of energy applications suggesting a suitable blockchain architecture in smart grid operations, a sample block structure and the potential blockchain technicalities employed in it. Also, added with efficient data aggregation schemes based on the blockchain technology to overcome the challenges related to privacy and security in the smart grid. Later on, consensus algorithms and protocols are discussed. Monitoring of the usage and statistics of energy distribution systems that can also be used to remotely control energy flow to a particular area. Further, the discussion on the blockchain-based frameworks that helps in the diagnosis and maintenance of smart grid equipment. We have also discussed several commercial implementations of blockchain in the smart grid. Finally, various challenges have been discussed for integrating these technologies. Overall, it can be said at the present point in time that blockchain technology certainly shows a lot of potentials from a customer perspective too and should be further developed by market participants. The approaches seen thus far may have a disruptive effect in the future and might require additional regulatory intervention in an already tightly regulated energy market. If blockchains are to deliver benefits for consumers (whether as consumers or prosumers of energy), a strong focus on consumer issues will be needed.

• 대한전기학회:학술대회논문집
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• 대한전기학회 2003년도 학술회의 논문집 정보 및 제어부문 B
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• pp.713-716
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• 2003

In recent, the contactless IC card is widely used in traffic, access control system and so forth. Contactless smart cards use a technology that enables card readers to provide power for transactions and communications without making physical contact with the cards. Usually electromagnetic signal is used for communication between the card and the reader. Contactless card is highly suitable for large quantity of card access and data transaction. And its use becomes a general tendency more and more because of the development of RF technology and improvement of requirement for user convenience. This paper describes the hardware module to process contactless protocol for implementation contactless IC card. And the hardware module consists of specific digital logic circuits that analyze digital signal from analog circuit and then generate data & status signal for CPU, and that convert the data from CPU into digital signal for analog circuit.

• 한국정보통신학회:학술대회논문집
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• 한국정보통신학회 2021년도 추계학술대회
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• pp.584-585
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• 2021

태양광, 풍력 등 신재생 에너지 생산이 다양해지면서 생산과 소비를 동시에 할 수 있는 마이크로그리드 시스템이 소개되었지만 국내에서는 아직까지 자동화된 전력거래 기술 도입이 필요하고 생산 및 중계인의 보호할 장치가 필요하다. 일반적으로 여름에는 태양광을 통한 전력 가격 하락이 예상되어 생산자 보호가 필요하다. 본 논문에서는 마이크로그리드 환경에서 블록체인(Blockchain)을 활용한 사용자 간 투명하고 안전한 선물 전력거래 시스템을 제안한다. 선물이란 간단히 말해서 고정된 가격과 미리 정해진 선물 가격에 구매자가 전력을 사는 의무를 가지거나 판매자가 전력을 팔아야 하는 의무를 갖게 되는 계약이다. 본 시스템은 블록체인 네트워크 내에서 신뢰할 수 있는 실행코드인 스마트 컨트랙트(Smart Contract)를 이용하여 사용자의 개입 없이 자동화된 동작으로 선물 가격을 검색하고 전력 거래를 체결하는 선물 거래 알고리즘을 제안한다. 만일 전력 생산자가 생산계획 시에 최대 생산 시기(하지)의 가격이 하락할 가능성이 있다고 생각이 되면 선물시장에서 선물을 먼저 팔아 놓고 최대 생산 시기(하지)에 선물을 되사서 이익을 내어 현물시장에서의 손실을 보전할 수 있다. 또 중계업자는 판매계약 체결 시에 전력 가격이 상승될 우려가 있으면 선물시장에서 먼저 선물을 매입하고 판매계약 이행 시 선물을 청산하여 이익을 실현시켜 현물시장에서의 손실을 보전할 수 있게 된다.

• KIEE International Transaction on Systems and Control
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• 제2D권2호
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• pp.78-91
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• 2002

In the thermal power plant, there are six manipulated variables: main steam flow, feedwater flow, fuel flow, air flow, spray flow, and gas recirculation flow. There are five controlled variables: generator output, main steam pressure, main steam temperature, exhaust gas density, and reheater steam temperature. Therefore, the thermal power plant control system is a multinput and output system. In the control system, the main steam temperature is typically regulated by the fuel flow rate and the spray flow rate, and the reheater steam temperature is regulated by the gas recirculation flow rate. However, strict control of the steam temperature must be maintained to avoid thermal stress. Maintaining the steam temperature can be difficult due to heating value variation to the fuel source, time delay changes in the main steam temperature versus changes in fuel flow rate, difficulty of control of the main steam temperature control and the reheater steam temperature control system owing to the dynamic response characteristics of changes in steam temperature and the reheater steam temperature, and the fluctuation of inner fluid water and steam flow rates during the load-following operation. Up to the present time, the Proportional-Integral-Derivative Controller has been used to operate this system. However, it is very difficult to achieve an optimal PID gain with no experience, since the gain of the PID controller has to be manually tuned by trial and error. This paper focuses on the characteristic comparison of the PID controller and the modified 2-DOF PID Controller (Two-Degrees-Freedom Proportional-Integral-Derivative) on the DCS (Distributed Control System). The method is to design an optimal controller that can be operated on the thermal generating plant in Seoul, Korea. The modified 2-DOF PID controller is designed to enable parameters to fit into the thermal plant during disturbances. To attain an optimal control method, transfer function and operating data from start-up, running, and stop procedures of the thermal plant have been acquired. Through this research, the stable range of a 2-DOF parameter for only this system could be found for the start-up procedure and this parameter could be used for the tuning problem. Also, this paper addressed whether an intelligent tuning method based on immune network algorithms can be used effectively in tuning these controllers.