• Title/Summary/Keyword: electrical power system

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Properties of ZnO:Ga Transparent Conducting Film Fabricated on O2 Plasma-Treated Polyethylene Naphthalate Substrate (산소플라즈마 전처리된 Polyethylene Naphthalate 기판 위에 증착된 ZnO:Ga 투명전도막의 특성)

  • Kim, Byeong-Guk;Kim, Jeong-Yeon;Oh, Byoung-Jin;Lim, Dong-Gun;Park, Jae-Hwan;Woo, Duck-Hyun;Kweon, Soon-Yong
    • Korean Journal of Materials Research
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    • v.20 no.4
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    • pp.175-180
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    • 2010
  • Transparent conducting oxide (TCO) films are widely used for optoelectronic applications. Among TCO materials, zinc oxide (ZnO) has been studied extensively for its high optical transmission and electrical conduction. In this study, the effects of $O_2$ plasma pretreatment on the properties of Ga-doped ZnO films (GZO) on polyethylene naphthalate (PEN) substrate were studied. The $O_2$ plasma pretreatment process was used instead of conventional oxide buffer layers. The $O_2$ plasma treatment process has several merits compared with the oxide buffer layer treatment, especially on a mass production scale. In this process, an additional sputtering system for oxide composition is not needed and the plasma treatment process is easily adopted as an in-line process. GZO films were fabricated by RF magnetron sputtering process. To improve surface energy and adhesion between the PEN substrate and the GZO film, the $O_2$ plasma pre-treatment process was used prior to GZO sputtering. As the RF power and the treatment time increased, the contact angle decreased and the RMS surface roughness increased significantly. It is believed that the surface energy and adhesive force of the polymer surfaces increased with the $O_2$ plasma treatment and that the crystallinity and grain size of the GZO films increased. When the RF power was 100W and the treatment time was 120 sec in the $O_2$ plasma pretreatment process, the resistivity of the GZO films on the PEN substrate was $1.05\;{\times}\;10^{-3}{\Omega}-cm$, which is an appropriate range for most optoelectronic applications.

Processing and Properties of Calcium Cobaltite Layer Structure Oxide Thermoelectrics (칼슘 코발트 층상 산화물계 열전반도체의 제조와 물성)

  • Kwak, Dong-Ha;Park, Jong-Won;Yoon, Sun-Ho;Choi, Jung-Chul;Choi, Seung-Chul
    • Journal of the Microelectronics and Packaging Society
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    • v.15 no.1
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    • pp.1-6
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    • 2008
  • Thermoelectric properties of calcium cobalt layer structure oxide system, $Ca_3Co_2O_6$ and $Ca_3Co_4O_9$ were investigated at the temperature range of 300 to 1000K for the application of thermoelectric generation. In the composition, the Ca site was partially substituted with Bi, Sr, La, K and the Co site was partially substituted with Mn, Fe, Ni, Cu, Zn. The thermoelectric properties of Bi substituted $Ca_3Co_4O_9$. $Ca_{2.7}Bi_{0.3}Co_4O_9$ for electrical conductivity, Seebeck coefficient and power factor were $85.4({\Omega}$cm)^{-l}, $176.2{\mu}V/K$ and $265.2{\mu}W/K^m$, respectively. The unit thermoelectric couple was fabricated with the p-type of $Ca_{2.7}Bi_{0.3}Co_4O_9$ and n-type ($Zn_{0.98}Al_{0.02}$)O thermoelectrics whose figure-of-merit(Z) were $0.87{\times}10^{-4}/K$ and $0.41{\times}10^4/K$, respectively. The generated thermoelectric power was about 30mV at the temperature difference of 120K in the unit thermoelectric couple.

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A Study on the Analysis of Electric Energy Pattern Based on Improved Real Time NIALM (개선된 실시간 NIALM 기반의 전기 에너지 패턴 분석에 관한 연구)

  • Jeong, Han-Sang;Sung, Kyung-Sang;Oh, Hae-Seok
    • Journal of the Korea Academia-Industrial cooperation Society
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    • v.18 no.4
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    • pp.34-42
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    • 2017
  • Since existing nonintrusive appliance load monitoring (NIALM) studies assume that voltage fluctuations are negligible for load identification, and do not affect the identification results, the power factor or harmonic signals associated with voltage are generally not considered parameters for load identification, which limits the application of NIALM in the Smart Home sector. Experiments in this paper indicate that the parameters related to voltage and the characteristics of harmonics should be used to improve the accuracy and reliability of the load monitoring system. Therefore, in this paper, we propose an improved NIALM method that can efficiently analyze the types of household appliances and electrical energy usage in a home network environment. The proposed method is able to analyze the energy usage pattern by analyzing operation characteristics inherent to household appliances using harmonic characteristics of some household appliances as recognition parameters. Through the proposed method, we expect to be able to provide services to the smart grid electric power demand management market and increase the energy efficiency of home appliances actually operating in a home network.

Classification Method of Multi-State Appliances in Non-intrusive Load Monitoring Environment based on Gramian Angular Field (Gramian angular field 기반 비간섭 부하 모니터링 환경에서의 다중 상태 가전기기 분류 기법)

  • Seon, Joon-Ho;Sun, Young-Ghyu;Kim, Soo-Hyun;Kyeong, Chanuk;Sim, Issac;Lee, Heung-Jae;Kim, Jin-Young
    • The Journal of the Institute of Internet, Broadcasting and Communication
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    • v.21 no.3
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    • pp.183-191
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    • 2021
  • Non-intrusive load monitoring is a technology that can be used for predicting and classifying the type of appliances through real-time monitoring of user power consumption, and it has recently got interested as a means of energy-saving. In this paper, we propose a system for classifying appliances from user consumption data by combining GAF(Gramian angular field) technique that can be used for converting one-dimensional data to the two-dimensional matrix with convolutional neural networks. We use REDD(residential energy disaggregation dataset) that is the public appliances power data and confirm the classification accuracy of the GASF(Gramian angular summation field) and GADF(Gramian angular difference field). Simulation results show that both models showed 94% accuracy on appliances with binary-state(on/off) and that GASF showed 93.5% accuracy that is 3% higher than GADF on appliances with multi-state. In later studies, we plan to increase the dataset and optimize the model to improve accuracy and speed.

The efficient DC-link voltage design of the Type 4 wind turbine that satisfies HVRT function requirements (HVRT 기능 요구조건을 만족하는 Type 4 풍력 발전기의 효율적인 직류단 전압 설계)

  • Baek, Seung-Hyuk;Kim, Sungmin
    • Journal of IKEEE
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    • v.25 no.2
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    • pp.399-407
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    • 2021
  • This paper proposes the DC-link voltage design method of Type 4 wind turbine that minimizes power loss and satisfies the High Voltage Ride Through(HVRT) function requirements of the transmission system operator. The Type 4 wind turbine used for large-capacity offshore wind turbine consists of the Back-to-Back converter in which the converter linked to the power grid and the inverter linked to the wind turbine share the DC-link. When the grid high voltage fault occurs in the Type 4 wind turbine, if the DC-link voltage is insufficient compared to the fault voltage level, the current controller of the grid-side converter can't operate smoothly due to over modulation. Therefore, to satisfy the HVRT function, the DC-link voltage should be designed based on the voltage level of high voltage fault. However, steady-state switching losses increase further as the DC-link voltage increases. Therefore, the considerations should be included for the loss to be increased when the DC-link voltage is designed significantly. In this paper, the design method for the DC-link voltage considered the fault voltage level and the loss is explained, and the validity of the proposed design method is verified through the HVRT function simulation based on the PSCAD model of the 2MVA Type 4 wind turbine.

Analysis of Propagation Characteristics in 6, 10, and 17 GHz Semi-Basement Indoor Corridor Environment (6, 10, 17 GHz 반지하 실내 복도 환경의 전파 특성 분석)

  • Lee, Seong-Hun;Cho, Byung-Lok
    • The Journal of the Korea institute of electronic communication sciences
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    • v.17 no.4
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    • pp.555-562
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    • 2022
  • This study measured and analyzed the propagation characteristics at frequencies 6, 10, and 17 GHz to discover the new propagation demands in a semi-basement indoor corridor environment for meeting the 4th industrial revolution requirements. The measured indoor environment is a straight corridor consisting of three lecture rooms and glass windows on the outside. The measurement scenario development and measurement system were constructed to match this environment. The transmitting antenna was fixed, and the frequency domain and time domain propagation characteristics were measured and analyzed in the line-of-sight environment based on the distance of the receiving antenna location. In the frequency domain, reliability was determined by the parameters of the floating intercept (FI) path loss model and an R-squared value of 0.5 or more. In the time domain, the root mean square (RMS) delay spread and the cumulative probability of K-factor were used to determine that 6 GHz had high propagation power and 17 GHz had low propagation power. These research results will be effective in providing ultra-connection and ultra-delay artificial intelligence services for WIFI 6, 5G, and future systems in a semi-basement indoor corridor environment.

Composite Gas Measurement System using NDIR Method (NDIR 방법을 이용한 복합 가스 측정 시스템)

  • Eo, Ik-soo
    • Journal of the Korea Academia-Industrial cooperation Society
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    • v.19 no.3
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    • pp.624-629
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    • 2018
  • The current study was conducted to develop a portable composite gas detector allowing the detection of both $CO_2$ and $CH_4$ gases by means of the Non Dispersive Infra-Red (NDIR) method. The gas detector is configured to radiate infrared waves using infrared lamps, where the wavelength of the infrared light is reduced due to absorption throughout the chamber, and this reduction (absorption) is detected by the absorption detector, before being converted and amplified to a 3.5V~6V electrical signal, providing as accurate a measurement as possible. The conventional singe sensor method measures the relative measurement by absorbing only specified wavelengths of infrared radiation, which in the case of gas detection leads to problems with accuracy due to the lack of a reference sensor when detecting light with a wavelength of only $4.26{\mu}m$. The dual sensor employed in this study provides a comparative measurement between the reference value derived from the wavelength of $3.91{\mu}m$, which is not influenced by other gas sources, and the measurement value derived from the wavelength of $4.26{\mu}m$, in order to reduce the errors and enhance the reliability, thereby allowing low power consumption for portable devices and multi-gas detection for both $CO_2$ and $CH_4$ gases. The portable composite gas detector developed herein provides a measurement rage of 0ppm~5,000ppm for $CO_2$ gas, and 0.5%vol for $CH_4$, which allows the determination of whether the $CO_2$ and $CH_4$ contents in indoor air are less than 1,000ppm or not. The current study established that the composite gas detector can be interlinked with firefighting appliances through portable devices or home automation, and is anticipated to be very effective in fire prevention.

An Analysis of Optimal Operation Strategy of ESS to Minimize Electricity Charge Using Octave (Octave를 이용한 전기 요금 최소화를 위한 ESS 운전 전략 최적화 방법에 대한 분석)

  • Gong, Eun Kyoung;Sohn, Jin-Man
    • Journal of the Korea Academia-Industrial cooperation Society
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    • v.19 no.4
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    • pp.85-92
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    • 2018
  • Reductions of the electricity charge are achieved by demand management of the load. The demand management method of the load using ESS involves peak shifting, which shifts from a high demand time to low demand time. By shifting the load, the peak load can be lowered and the energy charge can be saved. Electricity charges consist of the energy charge and the basic charge per contracted capacity. The energy charge and peak load are minimized by Linear Programming (LP) and Quadratic Programming (QP), respectively. On the other hand, each optimization method has its advantages and disadvantages. First, the LP cannot separate the efficiency of the ESS. To solve these problems, the charge and discharge efficiency of the ESS was separated by Mixed Integer Linear Programming (MILP). Nevertheless, both methods have the disadvantages that they must assume the reduction ratio of peak load. Therefore, QP was used to solve this problem. The next step was to optimize the formula combination of QP and LP to minimize the electricity charge. On the other hand, these two methods have disadvantages in that the charge and discharge efficiency of the ESS cannot be separated. This paper proposes an optimization method according to the situation by analyzing quantitatively the advantages and disadvantages of each optimization method.

Influence of Co-sputtered HfO2-Si Gate Dielectric in IZO-based thin Film Transistors (HfO2-Si의 조성비에 따른 HfSiOx의 IZO 기반 산화물 반도체에 대한 연구)

  • Cho, Dong Kyu;Yi, Moonsuk
    • Journal of the Institute of Electronics and Information Engineers
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    • v.50 no.2
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    • pp.98-103
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    • 2013
  • In this work, we investigated the enhanced performance of IZO-based TFTs with $HfSiO_x$ gate insulators. Four types of $HfSiO_x$ gate insulators using different diposition powers were deposited by co-sputtering $HfO_2$ and Si target. To simplify the processing sequences, all of the layers composing of TFTs were deposited by rf-magnetron sputtering method using patterned shadow-masks without any intentional heating of substrate and subsequent thermal annealing. The four different $HfSiO_x$ structural properties were investigated x-ray diffraction(XRD), atomic force microscopy(AFM) and also analyzed the electrical characteristics. There were some noticeable differences depending on the composition of the $HfO_2$ and Si combination. The TFT based on $HfSiO_x$ gate insulator with $HfO_2$(100W)-Si(100W) showed the best results with a field effect mobility of 2.0[$cm^2/V{\cdot}s$], a threshold voltage of -0.5[V], an on/off ratio of 5.89E+05 and RMS of 0.26[nm]. This show that the composition of the $HfO_2$ and Si is an important factor in an $HfSiO_x$ insulator. In addition, the effective bonding of $HfO_2$ and Si reduced the defects in the insulator bulk and also improved the interface quality between the channel and the gate insulator.

Impulse Based TOA Estimation Method Using Non-Periodic Transmission Pattern in LR-WPAN (LR-WPAN에서 비주기적 전송 패턴을 갖는 임펄스 기반의 TOA 추정 기법)

  • Park, Woon-Yong;Park, Cheol-Ung;Hong, Yun-Gi;Choi, Sung-Soo;Lee, Won-Cheol
    • The Journal of Korean Institute of Communications and Information Sciences
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    • v.33 no.4A
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    • pp.352-360
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    • 2008
  • Recently Task Group (TG) 4 of the Institute of Electrical and Electronics Engineers (IEEE) 802.15a has been recommended a system with ranging capability in existence of multiple Simultaneous operating piconets (SOPs) as well as low-cost, low-power. According to the ranging service, coherent and non-coherent based ranging schemes using ternary code have been adopted as a standard. However it is hard to estimate an accurate time of arrival (TOA) in case of using direct sequence based TOA estimation method because pulse repetition interval (PRI) offered by TG is more limited than the maximum excess delay (MED) of channel. To mitigate inter pulse interference (IPI) problem, this paper proposes a non-coherent TOA estimation scheme using non-periodic transmission (NPT) pattern. The proposed receiver is based on a non-coherent energy detection considering with motivation of low rate wireless personal area network (LR-WPAN). TOA information is estimated via proper comparison with a prescribed threshold after the sliding correlation and search back window (SBW) process for reducing TOA error. To verify the performance of proposed ranging scheme, two distinct channel models approved by IEEE 802.15.4a TG are considered. According to the simulation results, we could conclude that the proposed scheme have performed better performance than the conventional method on the existence of multiple SOPs.