Antonino Oscar Di Tommaso

Comprehensive Modeling and Experimental Testing of Fault Detection and Management of a Nonredundant Fault-Tolerant VSI

This paper presents an investigation and a comprehensive analysis on fault operations in a conventional three-phase voltage source inverter. After an introductory section dealing with power converter reliability and fault analysis issues in power electronics, a generalized switching function accounting for both healthy and faulty conditions and an easy and feasible method to embed fault diagnosis and reconfiguration within the control algorithm are introduced. The proposed system has simple and compact implementation. Experimental results operating both at open- and closed-loop current control, obtained using a test bench realized using a dSPACE system and the fault-tolerant inverter prototype demonstrate that the proposed solution is effective and feasible and makes all faults easily managed by the controller itself.

A Rotor Flux and Speed Observer for Sensorless Single-Phase Induction Motor Applications

It is usual to find single-phase induction motor (SPIM) in several house, office, shopping, farm, and industry applications, which are become each time more sophisticated and requiring the development of efficient alternatives to improve the operational performance of this machine. Although the rotor flux and rotational speed are essential variables in order to optimize the operation of a SPIM, the use of conventional sensors to measure them is not a viable option. Thus, the adoption of sensorless strategies is the more reasonable proposal for these cases. This paper presents a rotor flux and rotational speed observer for sensorless applications involving SPIMs. Computer simulations and the experimental results are used to verify the performance of the proposed observer.

A DSP-Based Resolver-To-Digital Converter for High-Performance Electrical Drive Applications

This paper presents a low cost, simple, and highly accurate resolver-to-digital converter (RDC) for electrical drive applications based on an integrated software approach, thus allowing a significant reduction of hardware components count with significant improvements in terms of reliability, reduction of fault rate, and susceptibility to electromagnetic interference (EMI). Particular attention has been addressed to cost which is 25% off over conventional RDC. Simulations and experimental tests confirm the high quality of the proposed system.

A New Software Tool for Design, Optimization, and Complete Analysis of Rotating Electrical Machines Windings

In this paper, a new software tool developed by the authors for ac winding design, optimization, and complete analysis is presented. In particular, this software can be used as a valid aid in design and analysis for a wide variety of motor and generator windings with generic number of phases (including the case of those machines in which some slots are left empty), pole pairs, slot number, and so on. The calculation of winding factors and the evaluation of their harmonic distribution is also accomplished. The software is implemented in the MATLAB programming environment. By means of some examples, covering the most relevant winding types, the capabilities of this software will be shown. In particular, integer and fractional slot, single- and double-layer winding, concentrated windings, imbrication, belt widening, and belt shifting techniques can be treated to reduce particular harmonics in the electromotive force (EMF) or in the magnetomotive force (MMF). Finally, the connections, the winding factor harmonic distribution, the total harmonic distortion (THD) of EMF and spatial distribution of both the MMF, the Görges polygon, and the flux density are shown together with an estimate of the differential leakage and the air-gap flux density spatial distribution. The software presented in this paper is very modular, highly structured, and flexible due to the conspicuous number of operations that it can fulfill. Clearly, for the sake of brevity and clarity, the authors limit to represent the main features of the software, without going into specific details of programming and coding. All the main mathematical relationships that are useful to solve the problem of design and optimization of the windings of rotating machines are hereafter presented.

A small power transmission prototype for electric vehicle wireless battery charge applications

In this paper a low cost prototype of wireless power transfer system based on air coupling is presented. The system here proposed can be useful for electric vehicle (EV) battery charging systems. It consists mainly of two copper wire coils, placed one in front of the other on the same axis. The inductor coil can easily be placed under the road surface (in a parking), while the other (the receiver coil) in the lower side of the vehicle. By exploiting the coils resonance coupling effect, electric energy can be transferred from the inductor coil to the receiver in order to charge the batteries. Low cost experimental tests carried out at DIEETCAM - University of Palermo, demonstrated the effectiveness of the proposed wireless power transfer prototype, being it capable to reach an efficiency of about 80% and more along a distance of 30 cm.

Vibration signature analysis for monitoring rotor broken bar in double squirrel cage induction motors based on wavelet analysis

Purpose – The purpose of this paper is to present a diagnosis technique, for rotor broken bar in double cage induction motor, based on advanced use of wavelet transform analysis. The proposed technique is experimentally validated. Design/methodology/approach – The proposed approach is based on a combined use of frequency sliding and wavelet transform analysis, to isolate the contribution of the rotor fault components issued from vibration signals in a single frequency band. Findings – The proposed technique is reliable for tracking the rotor fault components over time-frequency domain. The quantitative analysis results based on this technique are the proof of its robustness. Research limitations/implications – The validity of the proposed diagnosis approach is not limited to the analysis under steady-state operating conditions, but also for time-varying conditions where rotor fault components are spread in a wide frequency range. Practical implications – The developed approach is best suited for automotiv...

An Exact Method for the Determination of Differential Leakage Factors in Electrical Machines With Non-Symmetrical Windings

An exact and simple method for the determination of differential leakage factors in polyphase ac electrical machines with non-symmetrical windings is presented in this paper. The method relies on the properties of Görges polygons that are used to transform an infinite series expressing the differential leakage factor into a finite sum in order to significantly simplify the calculations. Some examples are shown and discussed in order to practically demonstrate the effectiveness of the proposed method.

Fault Tolerant Ancillary Function of Power Converters in Distributed Generation Power System within a Microgrid Structure

Distributed generation (DG) is deeply changing the existing distribution networks which become very sophisticated and complex incorporating both active and passive equipment. The simplification of their management can be obtained assuming a structure with small networks, namely, microgrids, reproducing, in a smaller scale, the structure of large networks including production, transmission, and distribution of the electrical energy. Power converters in distributed generation systems carry on some different ancillary functions as, for example, grid synchronization, islanding detection, fault ride through, and so on. In view of an optimal utilization of the generated electrical power, fault tolerant operation is to be considered as a suitable ancillary function for the next future. This paper presents a complete modeling of fault tolerant inverters able to simulate the main fault type occurrence and a control algorithm for fault tolerant converters suitable for microgrids. After the model description, formulated in terms of healthy device and leg binary variables, and the illustration of the fault tolerant control strategy, the paper shows how the control preserves power quality when the converter works in the linear range. The effectiveness of the proposed approach and control is shown through computer simulations and experimental results.

A platform-independent software for the design and analysis of windings of rotating electrical machines

In this paper the Authors present a highly modular and platform-independent software, being based on the MATLAB® programming environment, which is proposed as a valuable aid in the design and analysis of the windings of rotating electrical machines. Unlike the major part of the commercial software, the cases of both symmetric and asymmetric (unbalanced) windings with any number of phases are here considered. The software can perform a considerable amount of calculations in order to determine automatically the optimal structure of the winding starting from its specifications. It is also able to draw the winding map and gives the results of calculation for the harmonic winding factors. The realized software allow the designer to reduce the harmonics winding coefficient with the only drawback of a small reduction of the fundamental coefficient, both for e.m.f. and m.m.f.

A reexamination of voltage distortion for classical carrier-based vs B-Spline modulation of three-phase Voltage Sources Inverters

Voltage waveform improvement has been the object of several investigations for many years and a manifold of different solutions have been proposed to reduce the harmonic content in Voltage Source Inverters (VSI) power application. In many cases this improvements have been obtained by modifying the reference voltage modulating signal. The recent introduction of cardinal B-spline functions, used as carrier signals, has given rise to a new modulation technique whose main characteristic is a lower value of the Total Harmonic Distortion (THD). After the discussion on the B-Spline modulation principle and on its computational effort, a performance comparisons is carried out by means of Total Harmonic Distortion (THD) index and single significant harmonics investigation of experimental data. All comparisons are carried out taking both the reference voltage and the Root Mean Square (RMS) values of the output voltage into account showing how these two choices leads to different conclusions in terms of performance.