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Forecasting of meteorological variables is crucial for accurate planning and management of electrical power grids, aiming at improving overall efficiency and performance. In this paper, an artificial neural network (ANN)-based technique is investigated for short-term forecasting of the hourly wind speed and solar radiation. Specifically, the non-linear autoregressive network with exogenous inputs (NARX) ANN is considered, compared to other models, and then selected to perform multi-step-ahead forecasting. Different time horizons have been considered in the range between 8 and 24 hours ahead. The main advantage of the proposed method is that it reconciles good forecasting performance with a very simple network structure, which is potentially implementable on a low-cost processing platform.

Il lavoro tratta del progetto di filtri EMI per convertitori DC/AC ad elevata power density

In molti dei campi di impiego dei convertitori elettronici di potenza (aeronautico, aerospaziale, automotive, etc.) è richiesta la realizzazione di sistemi di conversione che, in relazione a stringenti vincoli di progetto, presentino, a parità di potenza, dimensioni sempre più compatte e pesi ridotti. In tale ottica, l’ottimizzazione della densità di potenza (power density) del convertitore diventa un obiettivo essenziale

This paper deals with a method for the parameter identification of an improved dynamic model of a photovoltaic (PV) source, which encompasses a capacitor and an inductor. The method is based on piecewise-linear (PWL) circuit approximation and step load responses. Considering the PV I-V characteristic as a PWL function, if a transient occurs in a linear region, the PV source can be approximated according to Thévenin's theorem. The cases referred to either capacitive or inductive dominant time constant are explained. The identification of the circuit parameters by least squares regression (LSR) applied to experimental data is discussed and finally a case study is presented.

This paper analyses the performance of two magnetic materials used in the active filters for Common Mode (CM) electromagnetic interference (EMI) reduction in induction motor drives. In particular, active filters based on CM voltage compensation, very useful in bearing current suppression, are considered. The magnetic material is exploited for the core of the common mode transformer (CMT) that it is a crucial part of such devices because it performs the injection of the compensation voltage into the power connections between the inverter and the motor. The issues regarding the choice of the CMT core magnetic material and the windings design are discussed. The problem of the magnetic saturation, related to the desired high power/weight ratio is investigated. Furthermore, the power losses in the magnetic material under non-sinusoidal supply condition are evaluated through a suitable measurement system. A comparison of two CMTs, realized with ferrite and with nanocrystalline material cores, respectively, which are designed to perform the same filtering effect, is presented.

This paper is focused on measurement of conducted electromagnetic emissions in new dual voltage automotive electrical system. After an analysis of the existing EMC standards related to 14V vehicle electrical systems, a possible solution for measurement of conducted emissions generated by 42V automotive device and, in particular, by 14V device supplied through a step-down DC/DC converter from 42V to 14V is presented. As a case study, electromagnetic disturbances produced by a DC electrical drive devoted to fuel pumping, composed by a 14 V DC motor and a DC/DC step down converter are evaluated by means a suitable experimental measurements systems set up by the Authors, and critically analysed. The obtained results highlight the contribution due to the power converter on EMC phenomena and the related implications of the contemporary presence of more DC/DC converter in the same vehicle.

In this work a high frequency model of a photovoltaic (PV) plant is identified and implemented aiming to investigate the common mode (CM) currents circulating through the ground connections of the plant. From the identification of the impedance obtained by frequency response of photovoltaic module and by a suitable of the power conversion unit, an equivalent high frequency circuit representation has been developed. The lumped parameters circuit model is implemented in PSpice environment to obtain the CM leakage currents. Harmonics at frequencies multiple of the switching frequency and a strong resonance at about 12 MHz are detected.