• 반도체디스플레이기술학회지
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• 제20권4호
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• pp.108-113
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• 2021

In this paper, a totem pole PFC was structured in two methods with FET and diode for low-speed switch while GaN FET was used for high-speed switch. Internal power loss, power conversion efficiency and steady-state characteristics of the two methods were compared in the totem pole bridgeless PFC circuit which is widely applied in large-capacity and high-efficiency switching rectifier of 500W or more. In order to compare and confirm the steady-state characteristics under equal conditions, a 2kW class totem pole bridgeless PFC was constructed and the experimental results were analyzed. From the experimental results, it was confirmed that the low-speed switch operation has a large difference in efficiency due to the internal conduction loss of the low-speed switch at a low input voltage. Especially, input power factor and load characteristic showed no difference regardless of the low-speed switch operation.

• 한국철도학회:학술대회논문집
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• 한국철도학회 2000년도 추계학술대회 논문집
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• pp.258-264
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• 2000

This study is to establish test method and evaluation technology of drive system appropriate to high speed train. The transmission system of high speed train serve in the severe condition compared with those of other trains, namely, they have to transmit high power to run with high speed and they have to make maximum use of the limited space. This paper reports the reviews and results for the test and evaluation method of reduction gearbox for high speed train and discusses various test items and methods about assembly and parts of gearbox transmission.

• 대한전기학회논문지:전기기기및에너지변환시스템부문B
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• 제55권7호
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• pp.337-345
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• 2006

This paper proposes a high speed SRM drive system for blower application with a new 4-level inverter and precise excitation position generator. For a high speed blower, a proper inverter and control method are proposed and the output characteristics are analyzed. In order to get a fast build-up and demagnetization of excitation current, a 4-level inverter system is proposed. The proposed 4-level inverter has additional charge capacitor, power switch and diode in the conventional asymmetric converter. The charged high voltage is supplied to the phase winding for fast current build-up, and demagnetization current is charged to additional capacitor of the 4-level inverter. In addition, a precise excitation position generator can reduce turn-on and turn-off angle error according to sampling period of digital control system. The proposed high speed SRM drive system is verified by computer simulation and experimental results.

• 한국철도학회:학술대회논문집
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• 한국철도학회 2004년도 추계학술대회 논문집
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• pp.334-341
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• 2004

This study is to establish design method and evaluation technology for drive system appropriate to high speed tilting train. The transmission system of high speed train serves in the severe condition compared with those of KHST(G7), namely, they have to transmit high power to run with high speed and they have to make maximum use of the limited space. This paper reports the reviews and results of the design and evaluation method for reduction gearbox of high speed tilting train and discusses various design items and methods about assembly and parts of reduction gearbox.

• 한국철도학회:학술대회논문집
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• 한국철도학회 2010년도 춘계학술대회 논문집
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• pp.1026-1032
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• 2010

In this paper, To estimate the train exterior noise and environment noise which are occur when High-Speed EMU is driving with the speed of 370km/h, Estimated sound source about noise that is appeared during operation based upon noise SPL values. Based on aero-dynamic noise source and wheel-rail noise source, these were already used to the existed research, we have estimated each sound power about measured noise, and computed the sound source to apply on the High-Speed EMU, and also calculated the sound power in case of the maximum operation speed of 370km/h.

• 한국철도학회:학술대회논문집
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• 한국철도학회 2010년도 춘계학술대회 논문집
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• pp.470-474
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• 2010

Up until now, power centralized trains have been produced due to the maintenance convenience and comfortableness, but there are some problems, such as limitation of viscosity and maintenance difficulty of railroad due to recently increasing axle mass. In order to improve the problems, power decentralized trains have been developed to improve traction power. In the case of using electrical braking system, it is possible to improve braking friction power. Induction motors have been developed for power decentralized high speed train because of less structural defection, and low maintenance and production cost. However, induction motors have limitations, such as assuring enough power capacity and efficiency with reduced size. PMSM (Permanent magnet synchronous motor) have been newly developed to improve shortcomings of induction motors. The PMSM can be produced small and light weighted. Also if the PMSM and induction motors have the same size and power capacity, the PMSM have better power efficiency. In this pater, the prototype and modified type of PMSM for "High-speed Electric Multiple Unit-400km/h eXperimmen" will be introduced.

• Journal of Communications and Networks
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• 제17권3호
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• pp.231-240
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• 2015

To facilitate the base station planning in high speed railway communication systems, it is necessary to consider the functional relationships between the base station transmit power and space parameters such as train velocity and cell radius. Since these functions are able to present some inherent system properties determined by its spatial topology, they will be referred to as the power-space functions in this paper. In light of the fact that the line-of-sight path persists the most power of the received signal of each passing train, this paper considers the average transmission rate and bounds on power-space functions based on the additive white Gaussian noise channel (AWGN) model. As shown by Monte Carlo simulations, using AWGN channel instead of Rician channel introduces very small approximation errors, but a tractable mathematical framework and insightful results. Particularly, lower bounds and upper bounds on the average transmission rate, as well as transmit power as functions of train velocity and cell radius are presented in this paper. It is also proved that to maintain a fixed amount of service or a fixed average transmission rate, the transmit power of a base station needs to be increased exponentially, if the train velocity or cell radius is increased, respectively.

• 한국철도학회논문집
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• 제7권2호
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• pp.120-124
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• 2004

Computer aided simulation is an essential part in planning, design, and operation of railway systems. To determine the adequate performance and specification of railway system, it is necessary to calculate train performances such as distance, speed, power during train's running. This paper presents result of train performance simulation using the program that developed for Korea high speed train. To verify result of simulation, we have compared that with experiment data.

• 한국철도학회:학술대회논문집
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• 한국철도학회 2003년도 춘계학술대회 논문집
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• pp.554-560
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• 2003

The transmission systems of high speed train serve in the severe condition compared with those of other trains, namely, they have to transmit high power to run with high speed and they have to make maximum use of the limited space. To clarify the capability of reduction gear unit for Korea High Speed Train, torque and temperature, vibration on the reduction gear unit were measured and test data were analyzed. This paper reports test methods and test results that performed to verify reliability of reduction gear unit during running test of Korea High Speed Train. It is confirmed from these results that the performance of reduction gear unit has not any problem.

• Journal of Electrical Engineering and Technology
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• 제12권6호
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• pp.2099-2105
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• 2017

In a power system that has a high wind penetration, the output power fluctuation of a large-scale wind turbine generator (WTG) caused by the varying wind speed increases the maximum frequency deviation, which is an important metric to assess the quality of electricity, because of the reduced system inertia. This paper proposes a stable power-smoothing scheme of a doubly-fed induction generator (DFIG) that can suppress the maximum frequency deviation, particularly for a power system with a high wind penetration. To do this, the proposed scheme employs an additional control loop relying on the system frequency deviation that operates in combination with the maximum power point tracking control loop. To improve the power-smoothing capability while guaranteeing the stable operation of a DFIG, the gain of the additional loop is modified with the rotor speed and frequency deviation. The gain is set to be high if the rotor speed and/or frequency deviation is large. The simulation results based on the IEEE 14-bus system demonstrate that the proposed scheme significantly lessens the output power fluctuation of a WTG under various scenarios by modifying the gain with the rotor speed and frequency deviation, and thereby it can regulate the frequency deviation within a narrow range.