R. Miceli

Back EMF Sensorless-Control Algorithm for High-Dynamic Performance PMSM

In this paper, a low-time-consuming and low-cost sensorless-control algorithm for high-dynamic performance permanent-magnet synchronous motors, both surface and internal permanent-magnet mounted for position and speed estimation, is introduced, discussed, and experimentally validated. This control algorithm is based on the estimation of rotor speed and angular position starting from the back electromotive force space-vector determination without voltage sensors by using the reference voltages given by the current controllers instead of the actual ones. This choice obviously introduces some errors that must be vanished by means of a compensating function. The novelties of the proposed estimation algorithm are the position-estimation equation and the process of compensation of the inverter phase lag that also suggests the final mathematical form of the estimation. The mathematical structure of the estimation guarantees a high degree of robustness against parameter variation as shown by the sensitivity analysis reported in this paper. Experimental verifications of the proposed sensorless-control system have been made with the aid of a flexible test bench for brushless motor electrical drives. The test results presented in this paper show the validity of the proposed low-cost sensorless-control algorithm and, above all, underline the high dynamic performances of the sensorless-control system also with a reduced equipment.

A mathematical model to determine the electrical energy production in photovoltaic fields under mismatch effect

Among the electrical energy production systems from renewable sources, the photovoltaic one represents today one of the most efficient and technically tested choice. In this paper the Authors present a mathematical model that allows the maximization of the generated power of photovoltaic (PV) plants under unequally radiation conditions.

Preisach function identification by neural networks

This paper presents a novel technique for the identification of the Preisach density function which is based on a neural-network approach and which requires a relatively limited amount of experimental parameters. The fundamental idea of this method is to identify Preisach function of the material by training a neural network with a set of loops whose identification function is known. In the final section of the paper, the method is verified on several cases.

A suitable control technique for fault-tolerant converters in Distributed Generation

The penetration of Distributed Generation (DG) in power systems is deeply changing the existing distribution networks which is becoming a very sophisticated and complex systems incorporating both active (generators) and passive systems (distribution systems, converters and loads). The necessary simplification can be obtained dealing with small networks, namely Micro-Grids, reproducing, in a smaller scale, the structure and the problems of large networks including production, transmission and distribution of the electrical energy. In order to achieve an adequate level of reliability, fault-tolerant operations of micro-grids become very important. This result can be achieved only using power converters with fault-tolerance capabilities. Therefore, this paper, presents a control algorithm for fault tolerant converters suitable for micro-grids. After describing the model of the power converter reformulated in terms of healthy leg binary variable, the paper shows how this control preserves power quality when the converter works in the linear range. The effectiveness of the proposed approach is shown through computer simulations.

Dynamics photovoltaic generators: Technical aspects and economical valuation

The strategy adopted from many European nations and not, to entrust the electric energy production to differently energetic sources has determined an increment of the scientific research for the solar resource exploitation. These scientific community activities follows with attention from the entrepreneurial world have concentrated on the innovative techniques and methodologies of the source conversion, solar concentration and the directions device optimization. This job focuses its attention on the simple application of solar-track device, based on consolidated technologies. The diffused application of these dispositive, could be, shortly, an important increment of electricity generation energy from solar source. In particular this job estimates, with economic indices and for different size of the photovoltaic systems and of the solar-track devices, the increment of electricity generation to guarantee its economically favorable for the investor.

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.

Investigation of motor current signature and vibration analysis for diagnosing rotor broken bars in double cage induction motors

This paper investigates the detectability of rotor broken bars in double cage induction motors using current signature and vibration analysis techniques. Double cage induction motors are commonly used for applications where successive loaded starts-up are mandatory. Experimental results were performed under healthy and faulty cases, and for different load conditions using each technique. Rotor broken bars fault detection based on sideband current components may fails due to the presence of inter bar currents that reduce the degree of rotor asymmetry, yielding to a decrease of the magnitude of these spectral components. But inter bar currents produce core vibrations in the axial direction, which can be detected using vibration analysis, in order to overcomes the limits of the classical (MCSA) in this condition.

Computer aided optimization via simulation tools of energy generation systems with universal small wind turbines

This paper considers the general issues in the project and the optimization of energy generation systems using small universal wind turbines, suitable in Distributed Generation (DG) and computer aided optimization for a better exploitation of wind source. Optimization in this field reveal to be more and more important because the local generation and consumption of electrical power, even for grid connected generators can suffers for unevenness of wind source exploitation, also in terms of wrong directions and in not regular wind flows. Computer aided design and optimization of small plants may give significant improvements in the development of the wind source also in accordance with the projections of future energy policies that foresee a significant increase of the wind generated energy for the future market. The effectiveness of computer aided optimization tools is illustrated in the present paper with the exposition of two case studies. In the first of them a Wind Electrical Energy Generating System is moved by a Modular Multiple Blade Fixed Pitch Wind Turbine coupled with an asynchronous wound rotor generator. In the second case study the optimization regards a Savonius wind turbine and a PM synchronous generator with particular reference to the development of wind source for the wind turbine and the reduction of saturation and of harmonic content in the emf for the electrical machines.

Economical Incentives and Systems of Certification for the Production of Electrical Energy from Renewable Energy Resources

In order to succeed in observing the international agreements undertaken in the Kyoto agreement protocol, today it is necessary to increase the electrical energy production from renewables energy resources (RERs). In this paper a complete description of the Italian incentive systems for the production of electrical energy from photovoltaic (PV) and other RERs is done. Moreover, some considerations about the effects of the incentive actions on the wide spread of RERs to produce electrical energy are reported; particular attention is paid in the economical analysis related to PY and wind systems.

A new high accuracy software based resolver-to-digital converter

Tracking resolver-to-digital conversion (R/D converter or simply RDC) has emerged as one of the most robust method for obtaining high resolution position and angular speed information from resolvers. In this paper low cost software based RDC is presented. The main features are: high accuracy, simple set up, high reliability and stability and good performances. Some experimental results, showing the capabilities of the proposed system, are presented and discussed. An output signal comparison between the proposed RDC and a commercial encoder is also presented.