• 전기학회논문지
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• 제67권12호
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• pp.1729-1734
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• 2018

Recently, interest in environmentally friendly transportation systems has been increasing, and study on railway systems has been aggressively conducted. Therefore, lots of studies have been done in railway advanced countries to improve performance of PWM converter. The research on the PWM converter for railway vehicle was mainly carried out on the converter mounted on railway vehicle such as the high-speed railway and metropolitan railway. In also, a lot of study has been carried out to improve converter performance installed in the ground. The high-capacity transform used in this paper converted from AC 22.9kV to AC 590V. The converter changed from AC 590V to DC 950V. In general, in the case of rectifier, the DC power supply system has a negative impact on inverter control characteristics because it can not avoid the pulsating component. In this study, it was performed current control for high-capacity converter using Matlab Simulink. The PWM converter is normally performed through the voltage and current at starting mode, powering mode, and braking mode. In the light-load test and the on-line test, we have studied for the PWM converter characteristics. Using this research, we have founded that the converter has excellent performance.

• 한국철도학회:학술대회논문집
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• 한국철도학회 2011년도 춘계학술대회 논문집
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• pp.82-92
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• 2011

This paper presents a PFC(Power Factor Correction) system to control the power factor of input current of the converter system which is working in the propulsion system of KTX high speed train. In the KTX train system, initially introduced from ALSTOM, the thyristor converter with phase controlling technique is adopted in the current fed type powering system. The input current induces harmonic losses highly because the waveform becomes rectangular shapes according to the filter inductor current increased as the train speed increasing gradually. Especially the interference with the signalling systems is severe concerned due to high current harmonics on the catenary line. To protect this problem, a frequency trap filter(notch filter) is operating with the input converter system. In this paper, an analysis work and PC simulation have been done on the PFC system to upgrade its performance and maintenance efficiency.

• 한국철도학회:학술대회논문집
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• 한국철도학회 2011년도 춘계학술대회 논문집
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• pp.948-953
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• 2011

In AC railway feeding system, three phase received from the network is changed to two phase power sources with different phases. The main circuit breaker installed train is automatically open by track signal when the train passes the neutral section. In order to continuously supply power source to train, the changeover system was used in Japan. Therefore, the train is able to operate under powering condition when it was passing through the neutral section. We investigated the control method to reduce the inrush current flowing main transformer in train. To examine the inrush current and operate the static semiconductor switch such as thyristor, we manufactured the small scale the changeover system and carried out performance tests.

• International Journal of Naval Architecture and Ocean Engineering
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• 제6권2호
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• pp.418-430
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• 2014

In this paper, a modelling technique for simulating self-propelled ships in waves is presented. The flow is modelled using a RANS solver coupled with an actuator disk model for the propeller. The motion of the ship is taken into consideration in the definition of the actuator disk region as well as the advance ratio of the propeller. The RPM of the propeller is controlled using a PID-controller with constraints added on the maximum permissible RPM increase rate. Results are presented for a freely surging model in regular waves with different constraints put on the PID-controller. The described method shows promising results and allows for the studying of several factors relating to self-propulsion. However, more validation data is needed to judge the accuracy of the model.

• 대한조선학회논문집
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• 제40권5호
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• pp.1-9
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• 2003

To predict the powering performance of full scale ships from the towing tank tests, resistance, propeller open water and self-propulsion tests are conducted. Model tests inevitably include the experimental error defined as the sum of two types of uncertainties, bias and precision errors. The induced errors in each element of model test are propagated through various routes and correlated with one another. The correlation coefficients are very important in the uncertainty analysis. The coefficient gives a direction(increase or decrease) for a value of error in individual elements. If the coefficient is not used accurately, the error bounds of the individual elements are overestimated or underestimated. In this study, the new methodology is applied to the uncertainty analysis of HMRI's towing tank tests, thus error bounds of each element is suggested and verified by several repetitive experiments.

• 한국해양공학회지
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• 제6권1호
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• pp.29-42
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• 1992

자유표면하에 잠긴 복잡한 3차원 물체 주위의 흐름을 해소하기 위한 수치계산법이 TUMMAC(Tokyo Univ. Modified Marker And Cell)법을 기초로 하여 개발되었다. 임의물체의 no-slip 3차원 물체표면조건을 보다 간단히 처리하기 위하여 "porosity"라는 개념이 도입되었으며, 담수성에 잠겨 있는 해저돌출물 주위의 유동을 계산하여 그 응용성을 검토하였다. 돌출물 후방의 복잡한 와동들의 상호간섭이 잘 시뮬레이션 되었다.시뮬레이션 되었다.

• 전력전자학회:학술대회논문집
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• 전력전자학회 2011년도 전력전자학술대회
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• pp.163-164
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• 2011

In this paper, a new half-bridge zeta converter employing a center-tapped rectifier is proposed. The proposed converter provides a bidirectional powering path in the rectifier. As a result, its improved rectifier voltage waveform reduces the output filter inductor size. Also, it maintains a wide ZVS range due to the characteristic of the conventional single-ended half-bridge zeta converter. The operational principles, the theoretical analysis, and the design considerations of the proposed converter are analyzed. To verify the performance of the proposed converter, experimental results from a 180W prototype are presented.

• 대한조선학회논문집
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• 제34권2호
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• pp.1-10
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• 1997

예인수조에서 저항추진 성능을 추정하기 위한 선형시험을 수행한 때는 계측정도에 나쁜 영향을 주는 불안정현상에 유의하여야 한다. 불안정현상을 일으키는 큰 원인인 수조수 수심에 따른 수온의 불균일, 연중 수온의 변화, 난류촉진장치, 저항시험 사의 이복현상에 대해 검토하였다. 그리고 수조수 순환, 수조동 난방, 탈기장지 및 난류촉진장치의 개선 등을 그 해결 방안으로 제시하였다.

• 전력전자학회논문지
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• 제20권6호
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• pp.534-539
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• 2015

The DC overhead line voltage of an electric railway substation swings depending on the accelerating and regenerative-braking energy of trains, and it deteriorates the energy quality of the electric facility in the DC railway substation and restricts the powering and braking performance of subway trains. Recently, an energy storage system or a regenerative inverter has been introduced into railway traction substations to diminish both the variance of the overhead line voltage and the peak power consumption. In this study, the variance of the overhead line voltage in a DC railway substation is modelled by RC parallel circuits in each feeder, and the RC parameters are estimated using the recursive least mean square (RLMS) scheme. The forgetting factor values for the RLMS are selected using simulated annealing optimization, and the modelling scheme of the overhead line voltage variation is evaluated through raw data measured in a downtown railway substation.

• 대한조선학회지
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• 제25권1호
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• pp.47-55
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• 1988

One of tuna longliners which have excellent operational record at the tropical Pacifical Ocean was selected as a parent hull form for the development of a new ship which could be operate at the high latitude northern Pacific Ocean. The parent hull was modified to adapt operational and enviromental condition of such a weather and sea states. This modification was carried out based on design experiences and model test results in towing tank. In this report modification techniques applied to the hull form design of a tuna longliner are summarized. The powering performance of the developed hull form is evaluated to show 19%, decrease of resistance campared with the parent hull form.