Time Université

This paper proposes an innovative drive system for BLDC motors based on a Dual Half Bridge (DHB) converter in front of a three-phase Voltage-Source Inverter (VSI). The system is adapted for low power applications and it offers galvanic isolation with a relatively limited number of switches. The DHB is controlled to ensure a constant DC voltage at the output while the VSI achieves the electronic commutation between stator windings. The DHB and the VSI have one shared leg which reduces the number of the required power transistors. Compared with existing isolated solutions, the proposed architecture allows bidirectional power flow. With these features, the drive system turns out to be suitable for different applications with high-end technology such electrical vehicles, drones, smart grids or medical devices. The control procedure of this system is analyzer and evaluated through this paper.

PurposeThis research discloses the effect of religiosity on purchasing intention through serial-mediation paths in a halal-certified food context. Borrowing from the identity theory while supplemented by the theory of planned behaviour (TPB) and the knowledge–attitude–practice (KAP) theory, a 4-layered framework is developed to investigate such an issue.Design/methodology/approach264 questionnaires are collected in the field study conducted in Tunis, Tunisia. Quota sampling method is applied. Testing of the hypotheses is performed using partial least square analysis.FindingsThe findings reveal that religiosity affects the four mediators—awareness, trust, subjective norm and perceived behavioural control—which in turn affect attitude, and purchase intention towards halal-certified food is eventually aroused. These four serial-mediation paths are further proved to form the mechanisms.Research limitations/implicationsThe field study participants are limited to consumers in Tunis. Besides, a mechanism to collect the data from general public including lower educated consumers should be necessary.Originality/valueThis research is a pioneering work investigating the sequential intervening effect in the religiosity-intention relationship in halal-certified food. The authors provide unique and fruitful insights into this relatively untapped field for academia and firms.

LEDs lighting systems usage has known an extra ordinary growth in outdoor lighting applications. they are widely known for their low-electricity consumption. External drivers with certain fixtures are required to activate and control LEDs for street lighting. The choice of driver’s structure and the characteristics of its components affect the overall lighting system efficiency. The objective of this work is to design, simulate, and implement a 50 W LED driver for street lighting systems. Firstly, a PWM Voltage-mode control is employed. The second control technique used in this work is the peak inductor current controlled topology operating in continuous conduction. In addition, a simulation is conducted during the stage of design of both control techniques

The objective of this paper is to synthesize a D-Statcom based on the parallel and isolated topology. Converter parallelization allows increasing the maximal power that can be delivered by the D-Statcom without changing the current or the voltage ratings of the used power modules. In the proposed configuration, DC links of the two converters are separated which offers a considerable attenuation of the undesirable circulating currents flowing between the two converters. The main contribution is to develop an innovative strategy to limit, as much as possible, the low frequency components of the circulating currents without adding current sensors at the output of each inverter. This strategy is based on balancing the voltages across the two isolated DC link capacitors. The performances are evaluated through simulation results.

Text-line segmentation is one of the key factors which affect the performance of handwriting recognition system. One of the problems making this task crucial, is the presence of touching letters representing a connection between the characters of successive text-lines. This paper explains the concepts of touching characters and presents a survey of various approaches for their segmentation once detected, to join each component piece to its natural and real text-line.

The present contribution aims to study the combination effects of pre- and post-nitriding grinding and gas nitriding parameters (depth of cut, abrasive type, cooling mode, and nitriding depth) on the material grindability and generated surface integrity of AISI D2 tool steel. As a result, it is shown that grinding with sol-gel abrasive type increases AISI D2 surface hardness before gas nitriding when compared to Al2O3. To remove the brittle white layer, a fine post-nitriding during grinding experiments shows an improved grindability, yet an increase of total and arithmetic roughness with all grinding combination’s parameters. After AISI D2 gas nitriding at 24 and 36 h, using the sol-gel abrasive type and conventional cooling mode, a compressive residual state of stresses was induced for lower depth of cut in grinding. When drawing the evolution of grinding specific energy regarding process parameters, it was possible to distinguish between burned and non-burned surfaces. This has helped to perform comparison of the AISI D2 steel ground surface burning under various grinding conditions after and before nitriding. Moreover, it was observed that thermal cracks appear only on severe grinding with combination of Al2O3 abrasive type and conventional cooling mode.

While renewable resources contribute in the diversification of power supply, they also impose some challenges on power system operation. As a producer of a large part of the green energy, the wind turbine has a great impact on the static security of the power systems. This paper proposes the evaluation of wind power generation impacts on the static security. In presence of Doubly Fed Induction Generator (DFIG) wind turbine, the system operation is assessed under different contingencies. A performance index is used to classify the security status into critical, secure, and insecure class. The proposed study is performed on the IEEE 39-bus system under Matlab Simulink toolbox.

The integration of distributed generation sources in the distribution network changes the characteristics of the distribution system and will have an impact on protections coordination. This paper modeled a real distribution system using the software package ETAP version 12. A wind farm is introduced as Distributed Generator (DG) at bus 15, and the impact that DG produces on protections coordination is studied. The wind farm can product false tripping, blinding of the overcurrent relays and loss of selectivity between protections devices. To overcome these problems, this paper proposes an economical solution. The activation of the directional protection feature and the update of relay settings can achieve the correct coordination.

Under unbalanced grid conditions, the control of the instantaneous active and reactive power causes the injection of unbalanced currents into the utility grid. Especially, the power oscillating terms that appear due to the interaction between different sequences voltages and currents remains an important issue. This problematic requires the design of consistent arrangements to calculate the current references that should be exchanged with the grid by the grid side converter (GSC). This paper introduces a mechanism of negative-sequence injection based on the control of d-q currents coordinates. Besides, a comparison study of the design of current controllers, using a generic vector approach, to enhance unbalance-fault ride-through capability of dispersed generation has been proposed. The performance of entire control system is evaluated by time domain simulations with MATLAB/Simulink. The achieved results have helped to facilitate, according the preferential issue, the choice for fault ride through by simply changing the GSC converter currents reference.