• 전력전자학회:학술대회논문집
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• 전력전자학회 1997년도 전력전자학술대회 논문집
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• pp.9-13
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• 1997

In this paper, the operation regions of a three-phase voltage-source PWM converter are defined: linear modulation region, allowed current region, linear control region, unity power-factor region, and power-factor decreasing region. Particularly, the power-factor decreasing region is first examined and defined as the region where both the sinusoidal input current control and the stable DC link voltage regulation can not be obtained with a unity power-factor operation. To avoid these undesirable effects, the optimal current vector is derived, which ensures the sinusoidal input current and the stable DC link voltage regulation with maximum power-factor available, and, in consequence, it extends the operation region of the PWM converter. The validity of the proposed control scheme is proved by the computer simulation.

• 대한전기학회논문지:전력기술부문A
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• 제53권4호
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• pp.221-226
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• 2004

Power system has recently used Double-circuit Line and Multi-circuit Line in the industrial development. This has an advantage of system stability and reliability, but the complexity of the system has a disadvantage that makes it difficult to protect the power line. Double-circuit Line has two operation conditions in the Single-circuit operation and Double-circuit operation, so it has mutual impedance. To make it possible for the remaining single-line to operate independently while there is a fault with first line or when maintenance is needed, a trip region for the single-circuit operation should be set in order to set the relay trip region. An optimal trip region for each operation, a different operational conditions for the relay setting should be calculated. In this paper, trip regions of each operation condition have been compared by considering mutual impedance and fault resistance that led to the calculation of fault impedance. Also, as we know that one of the advantages in the distance relay is the back-up protection, we calculated the trip region(Zone-2) in consideration of the mutual impedance.

• 대한전기학회논문지:전기기기및에너지변환시스템부문B
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• 제53권4호
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• pp.221-221
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• 2004

Power system has recently used Double-circuit Line and Multi-circuit Line in the industrial development. This has an advantage of system stability and reliability, but the complexity of the system has a disadvantage that makes it difficult to protect the power line. Double-circuit Line has two operation conditions in the Single-circuit operation and Double-circuit operation, so it has mutual impedance. To make it possible for the remaining single-line to operate independently while there is a fault with first line or when maintenance is needed, a trip region for the single-circuit operation should be set in order to set the relay trip region. An optimal trip region for each operation, a different operational conditions for the relay setting should be calculated. In this paper, trip regions of each operation condition have been compared by considering mutual impedance and fault resistance that led to the calculation of fault impedance. Also, as we know that one of the advantages in the distance relay is the back-up protection, we calculated the trip region(Zone-2) in consideration of the mutual impedance.

• 농촌계획
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• 제22권2호
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• pp.1-8
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• 2016

This study is intended to prepare an revitalization plan of region where rural development project is completed through an analysis of the actual condition of facility operation and maintenance in the region where the project is completed. The results of survey of actual condition of facility operation in the region where rural development project was completed showed that the facilities were not self-sufficient in terms of operation and maintenance cost. Therefore, a prerequisite to the revitalization of region where the project is completed is to prepare an alternative plan for increasing the efficiency and applicability of currently already prepared facilities. Second, a project operation organization system should be streamlined and the competency of operation personnel should continue to be strengthened. Third, it is necessary to prepare a support system and establish cooperation networks for increasing the extensibility of project and continuing to induce community revitalization in the region where the project is completed in the future.

• 전력전자학회논문지
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• 제19권5호
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• pp.463-469
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• 2014

This paper proposes a maximum torque operation strategy for the direct torque control of a surface-mounted permanent-magnet synchronous motor (SPMSM). The proposed method analyzes the available operation region of the stator flux of the SPMSM under voltage and current constraints. Based on this analysis, the optimal stator flux trajectory that yields the maximum torque is obtained across the entire operation region, including constant torque and constant power regions. The proposed strategy is also applicable in the flux-weakening region II operation of the SPMSM, which has no speed limit. The validity of the proposed method is verified through experiments conducted on an 800 W SPMSM drive system.

• Journal of Electrical Engineering and information Science
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• 제3권1호
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• pp.103-109
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• 1998

A new flux-weakening scheme for an Interior Permanent Magnet Synchronous Motor (IPMSM) is proposed. This control scheme enables the maximum torque operation for the fast acceleration in the constant power region according to the current and voltage limit condition. Especially the dynamic performance of the braking in the flux-weakening region is improved with the compensation of the stator resistance. Also since the onset of the flux weakening operation is adjusted according to the load conditions, the machine parameters, and whether motoring or braking region, the stable and precise transition operation into or out of the flux weakening region can be achieved. The effectiveness of the proposed scheme is verified through experiments with an IPMSM drive system.

• 전력전자학회:학술대회논문집
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• 전력전자학회 2005년도 전력전자학술대회 논문집
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• pp.30-32
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• 2005

In this paper, voltage control strategy for maximum torque operation of stator flux-oriented induction machine drive in the field-weakening region is proposed. In a conventional stator flux-oriented (SFO) induction machine drive system of the maximum torque capability cannot be obtained. The field-weakening method is used to vary the stator-flux reference in proportion to the inverse of the rotor speed. The proposed algorithm, based on the voltage control strategy, ensures the maximum torque operation over the field-weakening region. The proposed algorithm, voltage control strategy for maximum torque operation of capability, which is insensitive to the variation of machine parameters In the field-weakening region. The proposed algorithm is verified by simulation.

• 한국전산구조공학회:학술대회논문집
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• 한국전산구조공학회 2000년도 봄 학술발표회논문집
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• pp.332-339
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• 2000

In this paper the characteristics of vibration induced by subway trains running on track is discussed. The quantitative prediction of the vibration level and the countermeasure for reduction of necessary, is of importance for the better environment. It was made the constructed Bundang line as first step with the modified Young-Dan type to basis on the Japanese Young-Dan type. In this paper it was measured and analyzed to two region (①Susuh-Bokjung, ②Chorim-Suhyun region) of this, at present operational Bundang line when averaging velocity of train is 60(㎞/h). As the response characteristics of frequency induced by subway operation, it was confirmed that frequency band of neighborhood of 30∼80Hz in generally dominant. Also to assess the quantitative vibration as response level to be measured for each point of two region in subway operation, the vibrational response level was measured at the state to be not subway operation. And the level was approximately 1/5∼1/10 level comparing to subway operation.

• 전력전자학회논문지
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• 제3권2호
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• pp.156-164
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• 1998

3상 전압원 PWM 컨버터의 동작 영역을 동기 좌표계의 전류 벡터 평면에서 구분하고 그 특징을 설명하였다. 그 중 감역률 영역에서는 주어진 부하에 해당하는 입력 전류를 단위 역률로 제어하는 경우, 입력 전류는 왜곡되고 DC 링크 전압에는 맥동과 제어 오차가 발생하게 되어 주어진 부하 조건에서는 좋은 제어 성과를 얻을 수 없다. 본 논문에서는 이러한 문제점을 해결하는 최적 전류 벡터를 선정하는 방법을 제안하였다. 최적 전류 벡터의 선정으로 입력 전류를 가능한 최대 역률로서 정현적으로 제어하는 동시에 안정한 DC 링크 전압을 제어할 수 있게 하여 3상 전압원 PWM 컨버터의 동작 영역을 확장시킬 수 있다. 제안된 제어 방법을 실험을 통하여 증명하였다.

• Nuclear Engineering and Technology
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• 제54권8호
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• pp.3166-3175
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• 2022

The most numerical investigations of the thermal-hydraulic phenomena following the loss of the residual heat removal capability during the mid-loop operation of the pressurized water reactor were performed according to simplifications and are not sufficiently accurate. To perform more accurate and more reliable predictions of thermal-hydraulic accidents in a nuclear power plant using computational fluid dynamics codes, a more detailed methodology is needed. Modelling results identified that thermal stratification and natural convection are observed. Temperatures of lower monitoring points remain low, while temperatures of upper monitoring points increase over time. The water in the heated region, in the upper unheated region and the pipe region was well mixed due to natural convection, meanwhile, there is no natural convection in the lower unheated region. Water temperature in the pipe region increased after a certain time delay due to circulation of flow induced by natural convection in the heated and upper unheated regions. The modelling results correspond to the experimental data. The developed computational fluid dynamics methodology could be applied for modelling of two-component single/two-phase natural convection and thermal stratification phenomena during the mid-loop operation of the pressurized water reactor or other nuclear and non-nuclear installations at similar conditions.