• 대한전기학회논문지:전기기기및에너지변환시스템부문B
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• 제49권9호
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• pp.618-625
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• 2000

Recently PWM inverters are widely utilized for many industrial applications e.g. high performance motor drive and PWM techniques are newly developed for an accurate output voltage. Among them space voltage vector PWM(SVPWM) inverter has high voltage ratio and low harmonics compared to the conventional sinusoidal PWM inverter. However output voltage of PWM inverter is distorted and has error duet o the conducting voltage drop of switching devices and the dead time that is inevitable to prevent the shoot-through phenomenon. This paper investigates 3-phase SVPWM inverter which has a new compensation method against dead time and voltage drop. Proposed algorithm calculates gate pulse periods which directly compensates the dead time and nonlinear voltage drop without modification of reference voltages. Direct compensation of gate pulse periods produces exact output voltage and does not need additional circuits. The propose algorithm is verified through the simulation and experiments.

• 대한전기학회:학술대회논문집
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• 대한전기학회 2002년도 하계학술대회 논문집 A
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• pp.156-158
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• 2002

In this paper, we analyze about voltage sag effect at load side during fault according to change of power system condition. through the case studies, we find that there is no close connection between substation bus transfer and voltage sag during fault. however, we find that other feeder connecting with the faulted transmission is directly affected by fault type and magnitude, therefore, the main subject can be divided into the utility and customer side countermeasures, utilities concentrate their effort to prevent the faults and to modify the fault clearing practice in power system. however, the faults in power system can never be completely eliminated. therefore, customer side solutions usually involve the power conditioning equipment for sensitive loads aiso, we investigate that the several methods to reduce the number and severity of voltage sag and to dull the sensitivity of equipment for voltage sag have developed. moreover, about SEMI, the industry association for the semiconductor two voltage sag immunity standards.(SEMI F47, SEMI F42) The simulation is accomplished by PSS/E 26.

• 대한전기학회:학술대회논문집
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• 대한전기학회 1999년도 하계학술대회 논문집 C
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• pp.1085-1087
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• 1999

In this paper, we propose the method for assessing the effect of voltage sag in power distribution system using fuzzy risk assessment model. The proposed method is based on SCBEMA curve that expresses the representative susceptibility curve by voltage sag for each customer type. These corves are made using the CBEMA curves obtained from the experiment for the customers'sensitive equipment. In order to transform SCBEMA curves to the probability damage by voltage sag, the fuzzy risk assessment model is used in this paper. Case studies were performed to analyze the effect of voltage sag by varying parameters. The Monte Carlo simulation method and the historical reliability data in KEPCO are used for case studies.

• 한국정밀공학회지
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• 제28권6호
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• pp.716-723
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• 2011

The battery capacity of electric/hybrid vehicle is much larger than present automobile. For that reason, the connector of Green Car should be designed to transmit the high-electric voltage. In addition, the electromagnetic wave should be shielded to protect communication and signal circuits. In this study, shielding performance of the connector was analyzed through electromagnetic shield analysis, and a connector of Green Car was designed using thermoelectrical analysis, which is capable of transmitting the high-electric power. In the design of connector structure, the improved stability and workability was considered.

• 전기전자학회논문지
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• 제3권2호
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• pp.243-249
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• 1999

YBaCuO계 초전도체로 자기 센서를 제작하였다. 초전도 자기 센서는 약 95K에서 초전도 특성이 나타나며 액체질소온도에서 외부 자계를 인가할 때 전기저항이 증가하였다. 자계 인가로 인해 센서에서 발생되는 전압강하는 0에서부터 $100{\mu}V$이상으로 변화하였다. 전기저항의 변화는 자계에 의존하며, 센서의 감도는 2.9 ohm/T가 된다. 이 센서는 약 $1.5{\times}10^{-5}T(=1.5{\times}10^{-1}G)$까지의 자기를 감지 할 수 있다. 외부자계에 의한 전기저항의 증가는 초전도재료를 관통하는 자속으로 인한 Josephson 접합의 변화에 기인한다.

• 대한전기학회:학술대회논문집
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• 대한전기학회 2004년도 추계학술대회 논문집 전기설비전문위원
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• pp.10-13
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• 2004

현재 고도의 정보화 사회에서는 계측기 및 정보통신기기의 발달로 정확한 신뢰성이 요구되고 있으나, 정전이나 순간적 전압강하와 같은 전력장애의 요인은 산업에 막대한 영향을 미치므로 경제적 손실 등의 치명적인 피해를 준다. 이 문제를 해결하는 방안으로 무정전전원장치(UPS : Uninterruptible Power Supply)의 필요성이 요구되는 현실입니다. 그러나 UPS을 사용함으로써 문제점도 야기되고 있는 주요 원인은 밧데리의 불량과 교체에 따른 환경적인 문제가 대두되고 있는 헌상입니다. 문제점을 해소하기 위한 방안으로 축전지없이 정전을 보상하는 방식을 채택시 축전지 설치장소 확보, 운영관리, 교체 등에 따른 경제적 손실을 크게 줄일 수 있으며, 또한 축전지 미사용으로 인한 환경공해 문제가 해결 할 수 있다. 이러한 문제점을 해결하고자 PS 장비의 효율성과 신뢰성 모두가 향상되고 또한 장비의 연간 유지보수 비용 절감 및 환경 공해로부터 문제를 해소 할 수 있는 다이나믹 무정전전원장치(Dynamic Uninterruptible Power Supply)의 필요성이 대두되고 있는 실정입니다.

• 전기학회논문지P
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• 제63권2호
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• pp.95-101
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• 2014

In this paper, UPS, with a built-in instantaneous sag drop compensation features, was developed to improve performance. The improved UPS, using instantaneous moving average method, compensates by quickly measuring the voltage and series inverter of half-bridge type, using line-interactive method that links with the voltage of the battery and power source, was developed. In addition, by developing a parallel inverter that uses a high-efficiency PWM switching method, overall UPS system was enhanced. To verify the performance of the proposed algorithm, single-phase 5[kVA] UPS systems were designed and the experimental system was constructed. The low-cost type of Cortex-M3 module CPU STM32F103R8T6 (32[bit]) is attached and the switching time of mode transfer was set within 4 [ms]. THD of the linear load operates in less than 3[%], and the stability of the output voltage operates in approximately ${\pm}2[%]$ range. The superior performance of the operations was confirmed with the system set as above.

• 전력전자학회논문지
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• 제5권4호
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• pp.370-376
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• 2000

분 논문은 기존의 전력선을 이용한 전력선 반송 통선 시스템의 선호 감쇠 저하 방법을 연구한다. 제안된 시스템은 별도의 통신 선로를 설치한 필요가 없고 정보화 시대에 발맞춰 원격 검침, 자정 자동화 등 여러면에서 효율적으로 사용할 수 있다. 기존 시스템은 커패시터에 의한 반송 전류의 증기와 더불어 통신전압의 강하로 정보전달의 어려움을 가지고 있다. 제안된 시스템은 내부저향이 작고 무효전력을 공급할 수 있으며 송수신단 상호간의 저임피던스 문제가 없는 특수한 구조의 스위칭 증폭기 시스템을 가진다. 본 연구는 콘덴서 부하에 의한 PLC(Power Line Carrier) 통신 장애 문제를 해결히는데 그 목적이 있다.

• 전력전자학회:학술대회논문집
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• 전력전자학회 2003년도 춘계전력전자학술대회 논문집(2)
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• pp.896-899
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• 2003

The electric railway has been widely used as a transportation all over the world. It also was opened in 1973 in korea and it has been steadily proceeded in making electric railway network for a big city and building Keongbu high speed , electric railway. That's why the system of electric railway is able to solve the environmental pollution and operate the useful energy in environmental ways, it helps to increase the ability of transportation and to decrease the cost. Because of the advantage of making the economic situation better, the system of electric railway is trying to do their best in developing technique of electric railway. Because of the increasing of transportation and the high speed operation, cars with regenerative braking system was adapted. Therefore, unbalanced voltage and current of three phase system and the drop and rise of voltage of feeding circuit is expected. Now that building the substation, newly spends lots of costs and time, it is a very difficult situation to solve the problem. We can guess that electric railway line can't receive power from the power system of bigger size in building newly electric railway. In this paper, it was proved that series voltage compensator was suitable as a solution according to voltage drop and voltage fluctuating through computer simulation.

• 대한전기학회논문지:전력기술부문A
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• 제53권12호
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• pp.678-684
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• 2004

Automatic reclosing is a typical protection method in power distribution systems for clearing the temporary faults. However, it has a fatal weakness in regards to voltage sags because it produces successive voltage sags. In this paper, we explored successive impact of voltage sag due to the automatic reclosing of power distribution systems. The actual tests of low voltage loads were accomplished for obtaining the susceptibility of voltage sags. The final results of the test yielded power acceptability curves of voltage sag, and the curves were transformed the 3-dimensional CBEMA(Computer Business Equipment Manufacturer Association) format. For the quantitative evaluation of the impact of successive voltage sags, an assessment formulation using the voltage sag contour was proposed. The proposed formulation was tested by using the voltage sag contour data of IEEE standard and the results of the test. Through the case studies, we verified that the proposed method can be effectively used to evaluate the actual impact of successive voltage sans.