Current Issue : January - March Volume : 2018 Issue Number : 1 Articles : 5 Articles
This paper focuses on the extraction of an accurate small-signal equivalent circuit for\nmetal-oxide-semiconductor field-effect transistors (MOSFETs). An analytical modeling approach was\ndeveloped and successfully validated through the comparison between measured and simulated\nscattering parameters. The extraction of the equivalent circuit elements allowed for the estimation\nof the intrinsic unity current-gain cutoff frequency, which is a crucial figure of merit for assessing\nthe high-frequency performance. The experimental data show that the cutoff frequency of the tested\ndevices exhibits a nearly ideal scaling behavior with decreasing gate length....
Electric arc furnaces (EAFs) contribute to almost one third of the global steel production.\nArc furnaces use a large amount of electrical energy to process scrap or reduced iron and are relevant\nto study because small improvements in their efficiency account for significant energy savings.\nOptimal controllers need to be designed and proposed to enhance both process performance and\nenergy consumption. Due to the random and chaotic nature of the electric arcs, neural networks\nand other soft computing techniques have been used for modeling EAFs. This study proposes a\nmethodology for modeling EAFs that considers the time varying arc length as a relevant input\nparameter to the arc furnace model. Based on actual voltages and current measurements taken\nfrom an arc furnace, it was possible to estimate an arc length suitable for modeling the arc furnace\nusing neural networks. The obtained results show that the model reproduces not only the stable arc\nconditions but also the unstable arc conditions, which are difficult to identify in a real heat process.\nThe presented model can be applied for the development and testing of control systems to improve\nfurnace energy efficiency and productivity....
High energy density storage device exhibiting a reliable lifecycle is needed in the 21st\ncentury. Hence, energy storage research is critical for reducing energy consumption. Supercapacitors\nexhibit such characteristics via interfacial ion electrosorption and fast redox reactions. They are a\nfeasible solution for transportation applications, among others, due to their superb characteristics.\nIn this paper, we provide a background on supercapacitors, review public data on commercially\navailable supercapacitors for performance characteristics, and finally summarize their performance\nin terms of energy density, equivalent series resistance, and device time consistency....
Current differential protection is the main protection of transmission lines which include\nmulti-circuit lines on the same tower, and whose sensitivity and reliability of differential protection\nis mainly affected by the distributed capacitive current. For the four-circuit line on the same tower,\ndue to the influence of coupling between the loop road, the distributed capacitance current increases\nsignificantly when compared with ordinary lines, affecting the sensitivity of the current differential\nprotection, especially for different voltage levels throughout the four-circuit lines on the same tower.\nThe relationship of the electrostatic coupling between the circuits is more complex, and increases\nthe difficulty of the compensating the distributed capacitance current. This paper is based on the\nelectrostatic coupling principle of four-circuit lines on the same tower, establishes the distributed\nparameter model of four-circuit transmission lines on the same tower, and discusses the effect of\ncircuit operation mode on the compensation of capacitance current differential protection when\ndifferent faults occur on the complex four-circuit transmission lines on the same tower. A new\ncompensation scheme suitable for capacitive current compensation is proposed. Simulation results\nshow that this capacitive current compensation scheme can effectively improve the performance of\ncurrent differential protection....
This paper proposes a super capacitor energy storage-based modular multilevel converter\n(SCES-MMC) for mine hoist application. Different from the conventional MMCs, the sub-modules\nemploy distributed super capacitor banks, which are designed to absorb the regenerative energy\nof mine hoist and released in the traction condition, so as to improve energy utilization efficiency.\nThe key control technologies are introduced in detail, followed by analysis of the configuration and\noperation principles. The feasibility of the proposed SCES-MMC topology and the control theory are\nalso verified. Simulation results show that SCES-MMC can adapt to the variable frequency speed\nregulation of the motor drive, which shows good application prospects in the future for mediumand\nhigh-voltage mine hoist systems....
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