1,721,104 research outputs found
A New SiC-GaN-Based Two-Phase Interleaved Bidirectional DC-DC Converter for Plug-In Electric Vehicles
No full textWide Band Gap (WBG) semiconductor technologies such as Silicon Carbide (SiC) and Gallium Nitride (GaN) are considered as the future of power electronic devices. Especially, in hard-switching applications where switching power losses are important, GaN devices are more attractive because of their very low gate charge amount. On the other hand, universal dc-dc power converters in Electric Vehicles (EVs) are coming into attention to be replaced with two power electronic modules: dc-dc battery charger and dc-dc traction drive. Unfortunately, current lateral GaN devices are not applicable in high power dc-dc traction drive, neither in universal dc-dc converters because of their limited current rating. As a solution, a two-phase dc-dc converter is proposed in this paper in which one phase is SiC-based MOSFET and the other one is GaN-based transistor. To reach the maximum utilization of the GaN device, the output power will be shared through the two phases, based on the current rating of the GaN device. First, the power stage design and the average model of the converter are presented. Then, power losses and efficiency of the converter is investigated in comparison with an all-SiC converter through spice-based simulations. The simulation results highlight the higher efficiency of the proposed converter
Tecniche per la visualizzazione di immagini tomografiche
No full textViene descritto un software realizzato per la visualizzazione di dati acquisiti con la tomografia assiale computerizzata
Vetri elettrocromici: connessioni nei telai mobili
No full textAbstract
Classificati come dinamici attivi i vetri elettrocromici (EC) possono reversibilmente modificare le loro caratteristiche ottiche (colore e trasparenza) in relazione ad un parametro prescelto o per intervento dell’utente. Il cambiamento avviene applicando una variazione di potenziale a un film multilayer in cui si induce una reazione di ossido-riduzione. I pannelli vengono normalmente montati su telai non apribili ma, essendo la fase ON degli EC normalmente riservata alle ore diurne ad elevato soleggiamento, vi può essere l’esigenza di aprire gli infissi, parzialmente o totalmente e per brevi o lunghi periodi, nelle fasi OFF e, in casi particolari, anche nelle fasi ON. È importante, in queste circostanze, che il segnale venga correttamente trasferito, dall’unità di alimentazione ai pannelli, attraverso contatti mobili: i contatti devono poter trasmettere efficacemente segnali elettrici caratterizzati da tensioni relativamente basse, avere una buona resistenza all’usura e agli agenti atmosferici ed essere accettabili anche dal punto di vista percettivo. Il DICAAR e il DIEE hanno in corso sperimentazioni con l’obiettivo di proporre soluzioni integrate, come ad esempio quella cardine-contatto, che permettano sia l’apertura di diversificate tipologie di infisso sia il trasferimento dei segnali di alimentazione.Electrochromic glass is part of the active dynamic glazing: it is able to reversibly modify its optical features (colour and transparency) according to a preset parameter or on direct command by user. The change occurs applying a weak voltage to a multilayer film in which a red-ox reaction is induced. Panes are usually applied on not opening frames and they normally work in the ON state during the high sunshine daylight hours. We revealed the need to partially or fully open the windows for long or short time, both in the OFF and, in special cases, ON state. In these specific cases the electrical signal must be rightly transferred trough movable contacts. Contacts must be able to efficiently transfer the electrical signal which is characterized by quite low voltage. They must have a good resistance to wear and weathering and also be acceptable from the perceptual point of view. The DICAAR and DIEE have ongoing trials with the objective to propose integrated solutions, such as the hinge-contact system, which enable both the opening of diversified types of window that the transfer of power signals
Predictive Control of Permanent Magnet AC motor Drive
No full textA predictive control algorithm for PMAC motor drives is presented in the paper. The proposed approach, implemented in rotor coordinates, allows to impose the reference values of d and q current components using recursive algorithms. The output of the digital control system directly imposes the timing control of the inverter by means of on/off state of the switches. Due to the time required for the execution of the algorithm, the vector control can be imposed with a delay of one sampling time. By introducing in the recursive algorithm the observed quantities instead of the measured ones, allows to impose the vector control without the delay. The state observer requires to introduce sampled data of two sampling time before the actual one and, hence, to employ a more powerful computing unit. The drive controlled by the proposed algorithms is simulated using Matlab Simulink tool. The results are compared with that obtained by simulating the traditional drive, where the d-q components of the current are controlled by PI regulators and PWM technique. The comparison highlights the better performance of the proposed direct digital control algorithm with respect to the traditional one
Caratterizzazione di un tomografo di terza generazione
No full textAim of this paper is both the description and the characterisation of a third generation X-ray microtomography. The setuo has been completely made in our laboratory for the non destructive analysis of composite materials. The characterisation tests, which evidence limits and possibilities of the system are discussed
Discrete-Time Parameter Identification of a Surface-Mounted Permanent Magnet Synchronous Machine
No full textA novel online discrete-time parameters identification algorithm suitable for surface-mounted permanent magnet synchronous machines (SPMs) is presented in this paper. It is developed by means of the Model Reference Adaptive System (MRAS) technique and the Popov Hyperstability Criterion in order to identify SPM discrete-time model parameters. In particular, good accuracy of discrete-time parameters is required by digital control systems, especially by predictive control algorithms, which present a low robustness against parameters mismatches. Hence, an extensive simulation study is firstly carried out in the Matlab Simulink environment with the aim of testing the effectiveness and robustness of the proposed identification algorithm against inverter un-idealities. Then, the proposed identification procedure is experimentally validated on a predictive controlled radial-flux SPM, driven by a Field Programmable Gate Arrays (FPGA) control board
An adaptive Rotor Flux Observer for Direct Field Oriented Induction Motor Drives
No full textAt the present time the direct field oriented (DFO) control is the widely used control technique in high-performance induction motor (IM) drive. It requires the implementation of a state vector observer for the detection of rotor flux vector. The IM drive performance is strictly connected to that of the rotor flux observer. The motor parameter variations cause the observer mismatching and hence, the IM drive performance degradation. In the present paper an adaptive observer is proposed which allows the on-line rotor time-constant tuning. The identification of the rotor time constant is performed by an MRAS approach. The adaptive observer is synthesized using the Lyapunov stability theory. To improve the speed convergence of the identifier and the selectivity characteristic of the proposed adaptive observer, a time-varying gain has been introduced. The stability of the overall system has been verified using the Lyapunov stability theory. The simulation results evidence the good performance of the proposed observer and of the overall DFO controlled drive. In particular, the interactive effects between observer and identifier gains are evidenced and, thus, used for the selection of the identifier time-varying gain
A Sliding Mode Control Technique for Direct Speed Control of Induction Motor Drives
No full textIn the present paper a sliding mode based 1M drive control technique is proposed. It allows to control the speed and the stator flux magnitude, using just their measure and/or estimation, imposing directly the inverter voltage configuration. The mathematical modellisation of the proposed algorithm and the simulation results are reported to confirm the goodness of the proposed control technique
Optimal Torque Control of Synchronous Reluctance Motor Drive by Predictive Algorithm
No full textA predictive digital control of the synchronous reluctance motor drive is presented in this paper. The proposed control uses a recursive algorithm in which the reference values of d and q current components in rotor coordinates are imposed. The digital control system directly synthesizes the output vector which consists of the inverter on/off switches states. This technique results in avoiding the implementation of the traditional PI controllers and PWM technique. Under transient operation, the proposed algorithm allows the imposition of both the reference d-q current components, in order to achieve the maximum torque variation available during each sampling interval. The algorithm takes into account the magnetic cross saturation effects and the inverter voltage saturation constraint. So, the proposed control gets the fastest torque trajectory that can be exploited by the drive. Especially starting from rest, it can be shown that the proposed algorithm guarantees optimal torque step response. After the steady state torque is reached, the d-q current values, corresponding to the above torque, do not guarantee any further condition. Therefore, the proposed algorithm easily drives the above current components to the minimum Joule losses operating conditions, simultaneously keeping constant the torque value achieved. Hence, the proposed control algorithm gets the fastest start-up and the maximum efficiency, at the same time. A computer simulation study, using the Matlab Simulink tool, is conducted on the drive with the aim of highlighting the better performance of the proposed algorithm compared to the traditional and predictive (non optimal) ones
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