Current Issue : October - December Volume : 2018 Issue Number : 4 Articles : 5 Articles
In this paper, we propose adaptive nonlinear controllers for the Single-Ended Primary\nInductance Converter (SEPIC).We also consider four distinct situations: AC-DC, DC-DC, Continuous\nConduction Mode (CCM) and Discontinuous Conduction Mode (DCM). A comparative analysis\nbetween classic linear and nonlinear approaches to regulate the control loop is made. Three adaptive\nnonlinear control laws are designed: Feedback Linearization Control (FLC), Passivity-Based Control\n(PBC) and Interconnection and Damping Assignment Passivity-Based Control (IDAPBC). In order to\ncompare the performance of these control techniques, numerical simulations were made in Software\nand Hardware in the Loop (HIL) for nominal conditions and operation disturbances. We recommend\nadaptive controllers for the two different situations: Adaptive Passivity-Based Feedback Linearization\nControl (APBFLC) for the PFC (Power Factor Correction) AC-DC system and IDAPBC-BB (IDAPBC\nBased on Boost converter) for the regulator DC-DC system....
In this work, the main reasons for the breakage of 500 kV transmission line\nare studied. Under low temperature condition, the coverage of the ice results\nin the disconnection between the aluminum tube and the steel anchor of\nstrain clamp. Using macroscopic analysis, structure stress analysis, force analysis\nand mechanical property test, the fractured strain clamps are investigated.\nThe crimping of the aluminum tube on the polished rod not on the grooves of\nthe steel anchor leads to the damage of the strain clamps, which is defined as\nimproper crimping. When improper crimping emerges, there will be only\nfriction force between the aluminum tube and the steel anchor without shear\nforce, and the tension of the conductor will be mainly supported by the steel\nstrands which should be supported by both the aluminum tube and steel\nstands. Therefore, the breaking force of the strain clamp will greatly decrease.\nThe failure analysis helps to promote the proper hydraulic crimping process\nand the safe operation of the transmission line....
One of the key issues of the accurate parameters analysis for the piecewise envelope current signal is to position the change point\nprecisely. Discretewavelet transform (DWT)modulusmaximamethod can detect change point, but the detection window of DWT\nwill cause suspicious change point. Besides, the amount of calculated data is very large in actual process of envelope current signal.\nTherefore, in this paper, the envelope is used instead of the original sampling data for DWT so as to reduce the calculation amount.\nWhat is more, combined with the sliding dislocation window method, the change point can be located accurately and the pseudochange\npoint can be eliminated. The simulation results as well as the electric locomotive current and forging machine current\nexamples show that it is feasible to detect the change point precisely through the proposed method, which provides possibilities for\nreal-time online monitoring of change point....
Aeroengine fans and compressors increasingly operate subject to inlet distortion in the transonic flow regime. In this paper,\ninnovations to low-order numerical modeling of fans and compressors via volumetric source terms (body forces) are presented.\nThe approach builds upon past work to accommodate any axial fan/compressor geometry and ensures accurate work input and\nefficiency prediction across a range of flow coefficients. In particular, the efficiency drop-off near choke is captured. The model\nfor a particular blade row is calibrated using data from single-passage bladed computations. Compared to full-wheel unsteady\ncomputations which include the fan/compressor blades, the source termmodel approach can reduce computational cost by at least\ntwo orders of magnitude through a combination of reducing grid resolution and, critically, eliminating the need for a time-resolved\napproach. The approach is applied to NASA stage 67. For uniform flow, at 90% corrected speed and peak-efficiency, the body force\nmodel is able to predict the total-to-total pressure rise coefficient of the stage to within 1.43% and the isentropic efficiency to within\n0.03%.With a 120âË?Ë? sector of reduced inlet total pressure, distortion transfer through the machine iswell-captured and the associated\nefficiency penalty predicted with less than 2.7% error....
To improve the reliability and efficiency in cooperative communications, a power optimized single relay selection scheme is\nproposed by increasing the diversity effort with an improved link-adaptive-regenerative (ILAR) protocol. The protocol determines\nthe forwarding power of a relay node by comparing the signal-to-noise ratio (SNR) at both sides of the node; thus it improves the\npower efficiency. Moreover, it also proposes a single relay selection strategy to maximize the instantaneous SNR product, which\nensures the approximate best channel link quality for good relay forwarding. And the system adjusts the forwarding power in real\ntime and also selects the best relay node participated in the cooperative forwarding. In addition, the cooperation in the protocol\nis analyzed and the approximate expression of the bit-error-rate (BER) and the outage probability at high SNRs are also derived.\nSimulation results indicate that the BER and outage probability of the relay selection scheme by the ILAR protocol outperformother\ncontrast schemes of current existing protocols. At BER of 10âË?â??2, the proposed scheme with ILAR protocol outperforms those of the\ndecoded-and-forward (DF), the selected DF (SDF), and the amplify-and-forward (AF) protocols by 3.5, 3.5 and 7 dB, respectively.\nMoreover, the outage probability of the relay system decreases with the growth of the relay number.Therefore, the proposed relay\nselection scheme with ILAR strategies can be properly used in cooperative communications for good reliability and high power\nefficiency....
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