Current Issue : October - December Volume : 2016 Issue Number : 4 Articles : 7 Articles
Introduction: This paper uses a dynamic voltage restorer (DVR) to improve the voltage quality from voltage sags.\nIt is difficult to satisfy various of compensation quality and time of the voltage sag by using single compensation\nmethod. Furthermore, high-power consumption of the phase jump compensation increases the size and cost of a\ndynamic voltage restorer (DVR).\nMethods & Results: In order to improve the compensating efficiency of DVR, an optimized compensation strategy\nis proposed for voltage sag of micro-grid caused by interconnection and sensitive loads. The proposed\ncompensation strategy increases the supporting time for long voltage sags.\nDiscussion: Firstly, the power flow and the maximum compensation time of DVR are analyzed using three basic\ncompensation strategies. Then, the phase jump is corrected by pre-sag compensation. And a quadratic transition\ncurve, which involves the injected voltage phases of pre-sag strategy and minimum energy strategy, is used to\ntransform pre-sag compensation to minimum energy compensation of DVR.\nConclusions: The transition utilizes the storage system to reduce the rate of discharge. As a result, the proposed\nstrategy increases the supporting time for long voltage sags. The analytical study shows that the presented method\nsignificantly increases compensation time of DVR. The simulation results performed by MATLAB/SIMULINK also\nconfirm the effectiveness of the proposed method....
A printed energy harvesting and storage circuit powered by ambient office lighting and its use to power a\nprinted display is reported. The autonomous device is composed of three printed electronic components:\nan organic photovoltaic module, a carbon-nanotubes-only supercapacitor and an electrochromic display\nelement. Components are fabricated from safe and environmentally friendly materials, and have been\nfabricated using solution processing methods, which translate into low-cost and high-throughput\nmanufacturing. A supercapacitor made of spray-coated carbon nanotube based ink and aqueous NaCl\nelectrolyte was charged using a printed organic photovoltaic module exposed to office lighting conditions.\nThe supercapacitor charging rate, self-discharge rate and display operation were studied in detail.\nThe supercapacitor self-discharge rate was found to depend on the charging rate. The fully charged\nsupercapacitor was used as a power source to run the electrochromic display over 50 times....
Instructional laboratories are common in engineering programs. Instructional laboratories\nshould evolve with technology and support the changes in higher education, like the increased\npopularity of online courses. In this study, an affordable and portable laboratory kit was designed\nto replace the expensive on-campus equipment for two control systems courses. The complete kit\ncosts under $135 and weighs under 0.68 kilograms. It is comprised of off-the-shelf components\n(e.g., Raspberry Pi, DC motor) and 3D printed parts. The kit has two different configurations.\nThe first (base) configuration is a DC motor system with a position and speed sensor. The second\nconfiguration adds a Furuta inverted pendulum attachment with another position sensor. These\nconfigurations replicate most of the student learning outcomes for the two control systems courses\nfor which they were designed....
The electrocaloric effect in thin films of an electrocaloric material has the potential to be used for\nefficient cooling systems for high power electronic devices. We numerically calculated the effect of\nparameters in electrocaloric refrigeration with a thermal switch of fluid motion on the thermal\nperformance. The system of changing air and water flow with the pulse generation of cold energy\nincreased the heat transfer efficiency to 67% at a frequency of 5 Hz. The optimum time delay of\nwater flow to increase the heat transfer efficiency was zero at low frequency and became half of\nthe time period to change heat for a high frequency of 100 Hz. When the heat transfer efficiency\nwas high, the final temperature change in water flow was not the maximum temperature change....
Flip chip technology has been widely adopted in modern power light-emitting diode\n(LED) fabrications and its output efficiency is closely related to the submount material properties.\nHere, we present the electrical, optical and thermal properties of flip chip light-emitting diodes\nmounted on transparent sapphire and borosilicate glass which have shown a higher output luminous\nflux when compared to the traditional non-transparent mounted LEDs. Exhibiting both better\nthermal conductivity and good optical transparency, flip chip LEDs with a sapphire submount\nshowed superior performance when compared to the non-transparent silicon submount ones,\nand also showed better optical performance than the flip chip LEDs mounted on transparent\nbut poor-thermal-conducting glass substrates. The correspondent analysis was carried out\nusing ANSYS 14 to compare the experimental thermal imaging with the simulation results.\nTracePro software was also used to check the output luminous flux dependency on different LED\nmounting designs....
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In this study, we use ITO glass to deposit thermoelectric thin films by using electrochemically\ndeposition method. With electrochemical deposition, we deposit Te-Bi-Sb thin films on ITO glasses,\ntrying to probe into different influences on thermoelectric characteristics by changing Sb3+ consistency\nand current density. The finished Te-Bi-Sb thin films will be observed by Scanning Electron\nMicroscope (SEM) to realize the microstructure, also, be identified the crystal structure with XRD, and\nelectrical analysis. The result finds out the thin film is a P-type thermoelectric material. Owing to the\nvariation of current density or electrolyte density affects and changes the structure of Te-Bi-Sb film,\nthe study categorizes three types of forming structures: Ball-type, Mixed-type, and Acicular-type; the\nion content of the precipitated film can be controlled by alter current or electrolyte density. Good\nthermoelectric material requires high Seebeck coefficient, and the best one in the study is in the\ncondition of 38mM-2.1mA/cm2, which results in 32.89Ã?¼V/K. Also, power factor is a criterion to\nevaluate a material, and bigger factor equals to better quality. In this study, we get the best power\nfactor in the condition of 15mM-2.1 mA/cm2, with the result of 49.5505Ã?±2/ÃÂ....
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