• 전력전자학회:학술대회논문집
• /
• 전력전자학회 2006년도 전력전자학술대회 논문집
• /
• pp.456-458
• /
• 2006

Power line communication: PLC which easy to install at anywhere near outlet for electric machine. PLC uses transmission line for voltage of which is 60 Hz. Signals don't affect to electric machine in PLC because they are very small voltage. One of the important thing is the processes of adding signal to power line and extracting the signal from power line, the other is to choose the strong modulation method which sends signals long distance without loosing in PLC channel. but PLC channel have very high and variable noise and attenuation and then it is very hard to transmit optimally between the transmitter and the receiver. After all, impedance and noise problems of PLC channel must be overcame. Noises of 2 kinds which are AWGN abd impulse noise and attenuation are orated. To overcome the noise. Recently, Multi-carrier Modulation: MCM methods like as OFDM and DMT which are divide the channel into many sub-channel have been studied. those are powerful communication methods in PLC. In this paper, PLC channels made up of 3 numbers of noise and attenuation are simulated for getting BER by Matlab simulink.

• 한국통신학회논문지
• /
• 제19권9호
• /
• pp.1782-1792
• /
• 1994

$Ti:LiNbO_3$채널형 광도파로와 Asymmetric Coplanar Strip(ACPS) 전극구조를 이용해서, $1.3{\mu}m$에서 동작하는 진형파형 위상 광변조기를 설계, 제작한 다음 변조특성을 관찰하였다. 위상정합이 개선되도록 ACPS 진행파형 전극을 설계하기 위해서 전극과 완충박막의 두께를 포함하여, 전극제원의 해석적 함수로 특성저항, 변조파의 유효굴절률 및 전극손실 등을 고려하였다. Ti 확산방법으로 저손실 채널형 광도파로 제작하였으며, double-spin image reversal 공정을 이용해서 $2.5{\mu}m$ 두께의 전극을 형성하였다. 9GHz 부근에서의 전극구조 공진형상 때문에 변조특성이 제한 되었지만, 2.5GHz 까지는 큰 왜곡없이 변조특성이 관찰되었다.

• Journal of Power Electronics
• /
• 제17권2호
• /
• pp.490-500
• /
• 2017

Fuel cell (FC) is a promising power supply in electric vehicles (EV); however, it has poor dynamic performance and short service life. To address these shortcomings, a super capacitor (SC) is adopted as an auxiliary power supply. In this study, the frequency decoupling control method is used in electric vehicle energy system. High-frequency and low-frequency demand power is provided by SC and FC, respectively, which makes full use of two power supplies. Simultaneously, the energy system still has rapidity and reliability. The distributed power system (DPS) of EV requires DC-DC converters to achieve the desired voltage. The stability of cascaded converters must be assessed. Impedance-based methods are effective in the stability analysis of DPS. In this study, closed-loop impedances of interleaved half-bridge DC-DC converter and phase-shifted full-bridge DC-DC converter based on the frequency decoupling control method are derived. The closed-loop impedance of an inverter for permanent magnet synchronous motor based on space vector modulation control method is also derived. An improved Middlebrook criterion is used to assess and adjust the stability of the energy system. A theoretical analysis and simulation test are provided to demonstrate the feasibility of the energy management system and the control method.

• 대한화학회지
• /
• 제58권2호
• /
• pp.160-168
• /
• 2014

The electrochemical behavior and corrosion inhibition of zinc in 0.5 M $H_2SO_4$ in the absence and presence of some chromones has been investigated using weight loss, potentiodynamic polarization, electrochemical impedance spectroscopy (EIS) and electrochemical frequency modulation (EFM) techniques. The presence of these investigated compounds in the corrosive solutions decrease the weight loss, the corrosion current density, and double layer capacitance but increases the charge transfer resistance. Polarization studies were carried out at room temperature, and showed that all the studied compounds act as mixed type inhibitors with a slight predominance of cathodic character. The effect of temperature on corrosion inhibition has been studied and the thermodynamic activation and adsorption parameters were determined and discussed. The adsorption of the investigated compounds on zinc was found to obey Langmuir adsorption isotherm.

• 대한화학회지
• /
• 제58권4호
• /
• pp.359-365
• /
• 2014

The inhibition effect of cinnamon plant extract as a green corrosion inhibitor for steel in sulfide polluted salt water was studied by potentiodynamic polarization, electrochemical impedance spectroscopy (EIS), and electrochemical frequency modulation (EFM). The results showed that cinnamon plant extract in sulfide polluted salt water is a good corrosion inhibitor with inhibition efficiency reached to 80% at 250 ppm of the plant extract. The adsorption of cinnamon obeys Temkin adsorption isotherm, and acts as a mixed-type of inhibitor but dominantly as a cathodic inhibitor in sulfide polluted salt water.

• 대한전기학회:학술대회논문집
• /
• 대한전기학회 2004년도 추계학술대회 논문집 전기기기 및 에너지변환시스템부문
• /
• pp.153-156
• /
• 2004

This paper presents a new circuit topology of the half-bridge resonant inverter. As the proposed half-bridge inverter can be operated in the load freewheeling modes, pulse width modulation (PWM) control method can be used for the output power control. The proposed half-bridge inverter should keep unity output displacement factor under the load-impedance varying conditions, if a new PWM control scheme based on the resonant frequency tracking algorithm is adopted. In this paper, electrical characteristics, and losses analysis of the proposed half-bridge resonant inverter are described. Simulation and experimental results of the prototype experimental setup to verify the validity of the proposed half-bridge resonant inverter are presented and discussed.

• 전력전자학회:학술대회논문집
• /
• 전력전자학회 2004년도 전력전자학술대회 논문집(2)
• /
• pp.887-890
• /
• 2004

This paper presents a microprocessor controlled electronic ballast for HID lamps, which gives automatic switching between MH and HPS lamps. Lamp identification is carried out by checking variation of lamp impedance at warm-up phase. Direct spread spectrum is done by applying 1 kHz triangular wave for removing acoustic resonance. This frequency modulation of 1 kHz gives also low EMI level. The microprocessor controls the voltage of DC-bus, the voltage of ignition pulses, the power of output. A 250W electronic ballast is implemented with ATmega16 CPU.

• 전자공학회논문지A
• /
• 제29A권8호
• /
• pp.41-48
• /
• 1992

The characteristics of traveling-wave electrodes for high-frequency electroptic integrated devices are described from the view point of improvement of phase-matching based on the conformal mapping method. Specific calculations of the characteristic impedance, effective microwave index, and eletrode loss for asymmetric coplanar strip(ACPS) and coplanar waveguide(CPW) electrode structures are presented as a function of the geometric electrode parameters including the electrode thickness and buffer layer thickness. 5-10(x10S0-6Tm) thick Au-ACPS electrodes were successfully fabricated by electroplating and ECR etcher. The improvement of modulation bandwidth can be theoretically observed from the combination of electrode and buffer layer thickness.

• 대한화학회지
• /
• 제58권1호
• /
• pp.25-32
• /
• 2014

Corrosion inhibition of 304 stainless steel (SS) in 1 M HCl by aqueous extract of coriander seeds was studied using weight loss, potentiodynamic polarization, electrochemical impedance spectroscopy (EIS) and electrochemical frequency modulation (EFM) techniques. Values of inhibition efficiency obtained are dependent upon the concentration of extract and temperature. Generally, inhibition was found to increase with inhibitor concentration, but decrease with temperature. Physical adsorption mechanism has been proposed for the inhibition with Langmuir adsorption isotherm obeyed. Values of activation energy of the inhibited corrosion reaction of 304 SS are greater than the value obtained for the blank. Thermodynamic consideration reveals that adsorption of aqueous extract of coriander seeds 304 SS surface is spontaneous.

• Journal of Electrical Engineering and Technology
• /
• 제9권4호
• /
• pp.1269-1276
• /
• 2014

The main objective of this paper is to design DC-DC MPPT circuit using chaotic pulse width modulation to track maximum power from solar PV module for space application. The direct control method of tracking is used to extract maximum power. The nominal duty cycle of the main switch of DC-DC SEPIC converter is adjusted so that the solar panel output impedance is equal to the input resistance of the SEPIC converter which results better spectral performance in the tracked voltages when compared to conventional PWM control. The conversion efficiency of the proposed MPPT system is increased when CPWM is used as a control scheme