A. Massi Pavan

Least squares support vector machine for short-term prediction of meteorological time series

The prediction of meteorological time series plays very important role in several fields. In this paper, an application of least squares support vector machine (LS-SVM) for short-term prediction of meteorological time series (e.g. solar irradiation, air temperature, relative humidity, wind speed, wind direction and pressure) is presented. In order to check the generalization capability of the LS-SVM approach, a K-fold cross-validation and Kolmogorov–Smirnov test have been carried out. A comparison between LS-SVM and different artificial neural network (ANN) architectures (recurrent neural network, multi-layered perceptron, radial basis function and probabilistic neural network) is presented and discussed. The comparison showed that the LS-SVM produced significantly better results than ANN architectures. It also indicates that LS-SVM provides promising results for short-term prediction of meteorological data.

Fault diagnosis in photovoltaic arrays

This paper proposes a simple automatic technique for fault diagnosis in photovoltaic (PV) arrays, based on the analysis of the an omalies observed in the I-V characteristic. Firstly, the I-V characteristic of the PV array is simulated using Matlab/Simscape tool for different faulty conditions; which is experimentally validated by generating different faults on a PV string installed at the Renewable Energy Laboratory of the University of Jijel (Algeria). Subsequently, we compare the I-V characteristic of the PV string under different faults scenarios, in order to identify the anomalies. Finally, six categories are generated: Normal operation, connection fault, connection fault with shadow effect, partial shadow fault, a group of fault which include shadow effect with faults on bypass diode (open circuit bypass diode, inversed bypass diode, shunted bypass diode), and a group of fault which include: bypass diode fault, cell fault, module fault, and shadow effect with shunted by pass diode fault. The results show that the technique can accurately detect and localize faults occurring in the photovoltaic string.

An innovative photovoltaic field simulator for hardware-in-the-loop test of power conditioning units

In this work a review of photovoltaic (PV) field simulators and a project for the development of an innovative Hardware-In-the-Loop (HIL) PV field simulator are presented. The simulator is conceptually designed to be part of a future PV field demonstrator to be realized in the area of Trieste (Italy), which will include measurement facilities, networked PV fields, university laboratories and other research centers.

Leading the way toward fuel parity in photovoltaics: The utility-scale market in Sicily, Italy

The global photovoltaic (PV) market has been growing exponentially since almost twenty years. This huge demand for photovoltaic systems has been mainly driven by public subsidies in the form of a variety of national incentive schemes. However, in Countries where successful incentive schemes have been pioneered and are now - as planned - being brought to an end, the PV market is called to the challenge of surviving without any incentive to the end user. Grid and fuel-parity represent the keystone of this emerging new phase in the history of this renewable energy technology. In this paper we present a sensitivity analysis showing that in Sicily, Italy, the Levelized Cost of Energy from utility-scale PV plants is already competitive - if not even cheaper - with that from conventional power plants.

On the photovoltaic explicit empirical model: Operations along the current-voltage curve

Modelling of PhotoVoltaic (PV) devices is today used for a number of activities such as systems monitoring, power forecasting, fault diagnosis, etc. Explicit empirical models based on the datasheet parameters are quite easy to implement in computer-aided calculations and therefore they allow fast evaluations of the electrical behavior, whatever is the test condition (steady-state, transient, etc.). This paper focus on the introduction of a correction factor for one of these models in order to improve its performance for operating points different than maximum power point (MPP). The comparison between the current-voltage (I-V) characteristics predicted by the former and the proposed models clearly shows the effectiveness of the proposed correction factors. The model is tested for different environment conditions and for different materials constituting the PV cells.

Grid parity in the Italian domestic PV market a sensitivity analysis

Grid parity, where the cost of the kilowatt-hour produced by photovoltaics is less than the price of the kilowatt-hour acquired from the grid, is a recent success that in Italy made photovoltaics competitive even without incentives, and leads the continuing record-breaking growth at the global level of this technology. In this work, we show a sensitivity analysis for the Levelized Cost of Energy in the Italian domestic photovoltaic market. Moreover, we also propose a sensitivity analysis regarding the payback time related to the investment in a PV plant considering a 50% tax-reduction that is today available in the Italian market.

Monitoring applications of electrical and climate data for PV systems using Linux RTAI

This work presents the design and development of an innovative system aimed at detecting, recording and transmitting electrical and climate data from a PV field. Data are to be taken both from the PV modules and from the power conditioning system of a given PV field, through appropriate sensors, to monitor: climate data (irradiance, temperature), electrical quantities (voltage, current, power), performance of the PV generator as a function of climate parameters, performance of the power conditioning system over different working conditions. The system will exchange data through a communication network (i.e. Ethernet/TCP-IP) to download data, visualize quantities and operative states. The proposed system is designed to be integrated into any PV field, independently from the plant layout, the inverter type, the presence of preexisting data loggers, sensors, etc. Such a result is achieved using an open architecture, which assures an extremely high flexibility of utilization.

Coordinated voltage control of multi-converter power plants operating in transmission systems. The case of photovoltaics

Photovoltaic power plants connected to the high voltage transmission network are requested to support grid voltage regulation. This paper proposes a voltage and reactive power control for PV power plants based on a hierarchical voltage control which is typical in transmission systems but that has not been considered so far for distribution systems. The effectiveness of the proposed control scheme is duly discussed in the paper and tested through simulations.

Intentional islanding in medium voltage distribution grids

The penetration of Distributed Generators connected to the electric grid requires today new control strategies in order to participate in local ancillary services. This paper presents a control strategy for a Front-End Converter enhancing not only these new requirements but also the intentional islanding for a portion of the public medium voltage distribution grid. The simulation of the proposed control shows that a proper coordination with the Distribution System Operator can guarantee the needed continuity of service of a portion of the MV grid even during emergency mode operations.

Impact of Distributed Generation on power losses on an actual distribution network

Distributed Generation (DG) operating in a distribution network influences active power losses. In this paper power losses have been estimated for an actual low voltage distribution network and compared for different situations according to the DG penetration and placement of the power units. A practical method to place new DGs is presented. The basic idea is to minimize power losses, while complying voltage network limits, calculated with power flows using historical data over a discrete number of possible points of connection.