• 전기학회논문지
• /
• 제64권2호
• /
• pp.342-348
• /
• 2015

In this paper, fuel cell power generation system that is being studied in recent railway field was applied to compensate for the voltage drop due to the load as driving electric vehicle. PSIM simulation program is to be used to implement the modeling of the electric railway for AC AT feeder system. For it, It was applied to the product-type single-phase PLL algorithm, step-down converter is controlled as power so as to have the fuelcell generation system. Based on it's result, a reactive power due to the catenary impedance in accordance with the current flowing is compensated as linked with fuelcell generation system which supplied the current to the power supply grid. and then its performance was confirmed that voltage compensation effect obtained at SubStation (SS), SubSectioning Post (SSP), Sectioning Post (SP).

• 전기학회논문지
• /
• 제64권2호
• /
• pp.260-267
• /
• 2015

An LCL-type isolated dc-dc converter is analyzed, using ac approximation. Analyses to express characteristics on the proposed converter are derived under steady and ideal elements conditions in this paper. The two operating modes can be identified from the analysis results representing different device conduction sequences. This converter is capable of achieving required output voltage(step up or down) operations with inductance ratio while operated at fixed frequency with constant duty ratio-50%. Experimental results show that the designed converter based on Q has zero voltage switching and constant output voltage at different load variations to verify the analysis.

• International Journal of Safety
• /
• 제1권1호
• /
• pp.36-42
• /
• 2002

This paper is aimed at predicting the life of rubber insulating gloves under normal operating stresses from relatively rapid test performed at higher stresses. Specimens of rubber insulating gloves are subject to multiple stress conditions, i.e. combined electrical and thermal stresses. Two modes of electrical stress, step voltage stress and constant voltage stress are used in specimen aging. There are two types of test for electrical stress in this experiment: the one is Breakdown Voltage (BDV) test under step voltage stress and thermal stress and the other is lifetime test under constant voltage stress and temperature stress. The ac breakdown voltage defined as the break-down point of insulation that leakage current excesses a limit value, l0mA in this experiment, is determined. Because the very high variability of aging data requires the application of statistical model, Weibull distribution is used to represent the failure times as the straight line on Weibull probability paper. Weibull parameters are deter-mined by three statistical methods i.e. maximum likelihood method, graphical method and least squares method, which employ SAS package, Weibull probability paper and FORTRAN, respectively. Two chosen models for predicting the life under simultaneous electrical and thermal stresses are inverse power model and exponential model. And the constants of life equation for multistress aging are calculated using numerical method, such as Gauss Jordan method etc.. The completion of life equation enables to estimate the life at normal stress based on the data collected from accelerated aging test. Also the comparison of the calculated lifetimes between the inverse power model and the exponential model is carried out. And the lifetimes calculated by three statistical methods with lower voltage than test voltage are compared. The results obtained from the suggested experimental method are presented and discussed.

• 한국정보통신학회논문지
• /
• 제10권4호
• /
• pp.652-658
• /
• 2006

본 논문은 승압형 컨버터, 강압형 컨버터 및 저주파 인버터를 이용한 고휘도 Short-Arc 램프용 전자식 안정기의 설계 및 제작에 관하여 기술하였다. 제안한 안정기는 130 [Hz]의 구형 저주파를 램프에 인가함으로써 고압 방전 램프에서 발생할 수 있는 음향공명현상을 제거하였으며, 25 [kHz]의 고주파 전압을 중첩시켜 아크튜브의 전극에서 발생할 수 있는 열적 불균형을 해소하였다. 또한 전압 전류의 합을 이용한 정전력 제어를 수행하여, 주위 환경 및 램프의 노화에 따른 램프 전압의 변화에 대하여 안정한 점등상태를 유지하였다. 실험 결과로부터, 제작한 전자식 안정기의 램프 전압, 전류 및 전력은 각각 123.8 [V], 8.1 [A] 1,002 [W]로 측정되었다.

• Journal of international Conference on Electrical Machines and Systems
• /
• 제1권1호
• /
• pp.67-76
• /
• 2012

Due to the increasing amount of applications of power electronic ac-dc converters, it is necessary to design a single-stage converter that can reliably perform both buck and boost operations. Traditionally, this can be achieved by double-stage conversion (ac/dc-dc/dc) which ultimately leads to less efficiency and a more complex control system. This paper discusses two types of modern ac-dc converters. First, the novel impedance-source ac-dc converter, abbreviated as custom Z-source rectifier, is analyzed; and then, switched inductor (SL) Z-source ac-dc converter is proposed. This paper describes the Z-source rectifiers' operating principles, the concepts behind them, and their superiorities. Analysis and simulation results show that the proposed custom Z-source rectifier can step up and step down voltage; and the main advantage of the SL Z-source ac-dc converter is its high step-up capability. Low ripple of the output dc voltage is the other advantage of the proposed converters. Finally, the SL Z-source ac-dc converter is compared with the custom Z-source ac-dc converter.

• 한국산업융합학회 논문집
• /
• 제21권6호
• /
• pp.265-271
• /
• 2018

DC-DC buck converter is a critical building block in the power management integrated circuit (PMIC) architecture for the portable devices such as cellular phone, personal digital assistance (PDA) because of its power efficiency over a wide range of conversion ratio. To ensure a safe operation, avoid unexpected damages and enhance the reliability of the converter, fully-integrated protection circuits such as over voltage protection (OVP), under voltage lock out (UVLO), startup, and thermal shutdown (TSD) blocks are designed. In this paper, these three fully-integrated protection circuit blocks are proposed for use in the DC-DC buck converter. The buck converter with proposed protection blocks is operated with a switching frequency of 1 MHz in continuous conduction mode (CCM). In order to verify the proposed scheme, the buck converter has been designed using a 180 nm CMOS technology. The UVLO circuit is designed to track the input voltage and turns on/off the buck converter when the input voltage is higher/lower than 2.6 V, respectively. The OVP circuit blocks the buck converter's operation when the input voltage is over 3.3 V, thereby preventing the destruction of the devices inside the controller IC. The TSD circuit shuts down the converter's operation when the temperature is over $85^{\circ}C$. In order to verify the proposed scheme, these protection circuits were firstly verified through the simulation in SPICE. The proposed protection circuits were then fabricated and the measured results showed a good matching with the simulation results.

• Journal of Power Electronics
• /
• 제9권6호
• /
• pp.835-844
• /
• 2009

In this paper a new buck-boost type DC-DC converter is presented. Its voltage gain is positive, all active elements operate under soft-switching condition independent of loading, magnetic isolation and self output short-circuit protection exist, and very fast dynamic operation is achievable by a simple bang-bang controller. This converter also exhibits appropriate PFC characteristics since its input current is inherently proportional to the source voltage. When the voltage source is off-line, it is sufficient to add an inductor after the rectifier, then near unity power factor is achievable. All essential guidelines to design the converter as a DC-DC and a PFC regulator are presented. Simulation and experimental results verify the developed theoretical analysis.

• 대한전기학회:학술대회논문집
• /
• 대한전기학회 2001년도 하계학술대회 논문집 B
• /
• pp.1032-1034
• /
• 2001

As well known, a solar cell has an optimal operating point to be able to get the maximum power $P_{max}$. So, many $P_{max}$ tracking controllers using the line voltage of a solar cell have been popularly used. But it may vary depending on the miss match between the solar cell output and the load. In this paper, we investigate the possibilities of $P_{max}$ control using the current tracking controller and the output voltage and the output current instead of the solar cell output power. And we also examine about the optimal power converter using ZVCS step up and down chopper circuit to operate the solar cell at an optimal voltage using these variables. And then, we show some experimental results to confirm the successful operation.

• 전력전자학회논문지
• /
• 제1권1호
• /
• pp.38-46
• /
• 1996

The commutation operation of the current source converter for switched reluctance motor drives is analyzed in this paper. The commutation operation in the current source converter consists of two modes. At turn-off of phase switch, the phase current decreases sinusoidally, and the sum of two phase currents during commutation period is constant. At this time, the capacitor voltage increases quickly with changing polarity and decreases slowly when another phase switches turn on or off. Frequency of step-down DC chopper in the current source converter is low because of the dump such as BJTs and GTOs are possible as phase switches instead of Power MOSFET and IGBTS. They may result in reductions of conduction losses and manufacturing cost in the current source converter comparing to the voltage source converter of SRM.

• 대한전기학회:학술대회논문집
• /
• 대한전기학회 2007년도 제38회 하계학술대회
• /
• pp.1704-1705
• /
• 2007

A step-down procedure employing low voltage thermal transfer standard(LVTS) and micropotentiometer is described for the establishing the ac low voltage standards in the range of 2 mV to 200 mV below 1 MHz. Techniques are given for measuring input impedance with insertion method and calculating the loading error for the ac-dc transfer difference of the LVTS.