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36th European Photovoltaic Solar Energy Conference and Exhibition; 1593-1599, The condition of a solar PV panel can be evaluated by its measured electrical characteristics. The singlediode model parameters extracted from a measured current-voltage curve may indicate the possible presence of degradation. Aging of PV cells is a common source of degradation and manifests itself typically in increased series resistance values, causing a decline in the voltage characteristics of a PV panel. However, the current and voltage characteristics of a PV panel change considerably with changing environmental conditions, especially with changing irradiance and temperature. Accordingly, the single diode model parameter values change along variations in the surrounding environmental conditions, making the comparison of any two distinct current-voltage curves measured in outdoor conditions difficult. This gives a reason for converting the identified single diode model parameters of a measured curve from actual operating conditions to common reference conditions. In this light, we study the relation between the PV panel voltage and series resistance under different environmental conditions. We also investigate the feasibility of parameter reversion back to standard test conditions.

24th European Photovoltaic Solar Energy Conference, 21-25 September 2009, Hamburg, Germany; 4357-4359, Photovoltaic (PV) systems used in applications for sustainable mobility dramatically suffer from mismatching effects. In fact, the energy losses due to shadows and soil, but also referable to manufacturing tolerances and ageing, lower the power production of the PV string significantly and make the adoption of such energy source unattractive. It is a common practice, especially if the PV string is made of a small number of cells, to connect the cells in series, thus connecting the resulting string at the input of a battery charger in order to adapt the current profile to the battery needs. Nevertheless, such solutions guarantee a poor battery recharging and this estranges the customer from the PV technology even if it has a large potential in this field of application. In this paper the development of a new PV kit for sailing applications and for sustainable mobility is presented. It has been initially designed for the Class 40 racing craft “Telecom Italia” of Giovanni Soldini, but now it is on the market as a plug-and-play device for a variety of uses.

Photovoltaic modules parametric identification is often performed based on data available in the data sheet and referred to standard test conditions. On-line identification is trickier when irradiance and temperature sensors are not available. In this paper, an identification procedure is presented aiming to identify some module fault conditions that often occur during its lifetime. The proposed approach is applied to a large database of current vs voltage curves that are experimentally measured on a real photovoltaic plant.

This is the version of the paper distributed at the IEEE ICCEP 2019 Conference that has taken place in Otranto (Italy) from 2 to 4 July 2019.

The single diode equivalent circuit allows describing photovoltaic panels behavior quite accurately. The values of the five parameters appearing in this model are usually identified in Standard Test Conditions, at which irradiance and temperature values are given. Instead, when this identification has to be performed on field, suitable environmental sensors are required. In this paper, a method is presented for identifying the single diode model parameters as well as the irradiance and temperature conditions at which the panel is actually working. The method has the measured panel current vs voltage curve as the only input and it is suitable for being implemented on an embedded system for field applications. The method is validated through a large database of experimental results.

This is the version of the paper distributed at the IEEE ICCEP 2019 Conference that has taken place in Otranto (Italy) from 2 to 4 July 2019.

The single diode equivalent circuit allows describing photovoltaic panels behavior quite accurately. The values of the five parameters appearing in this model are usually identified in Standard Test Conditions, at which irradiance and temperature values are given. Instead, when this identification has to be performed on field, suitable environmental sensors are required. In this paper, a method is presented for identifying the single diode model parameters as well as the irradiance and temperature conditions at which the panel is actually working. The method has the measured panel current vs voltage curve as the only input and it is suitable for being implemented on an embedded system for field applications. The method is validated through a large database of experimental results.

This paper proposes an energy management system (EMS) for a photovoltaic (PV) grid-connected charging station with a battery energy storage system (BESS). The main objective of this EMS is to manage the energy delivered to the electric vehicle (EV), considering the price and CO2 emissions due to the grid’s connection. Thus, we present a multi-objective two-stage optimization to reduce the impact of the charging station on the environment, as well as the costs. The first stage of the optimization provides an energy schedule, taking into account the PV forecast, the hourly grid’s CO2 emissions factor, the electricity price, and the initial state of charge of the BESS. The output from this first stage corresponds to the maximum power permitted to be delivered to the EV by the grid. Then, the second stage of the optimization is based on model predictive control that looks to manage the energy flow from the grid, the PV, and the BESS. The proposed EMS is validated using an actual PV/BESS charging station located at the University of Trieste, Italy. Then, this paper presents an analysis of the performance of the charging station under the new EMS considering three main aspects, economic, environmental, and energy, for one month of data. The results show that due to the proposed optimization, the new energy profile guarantees a reduction of 32% in emissions and 29% in energy costs.

In this paper, the use of the Dual Kalman Filter for the identification of photovoltaic system parameters is presented. The system includes the photovoltaic source, the dc/dc converter and the battery/dc bus and both its states and parameters in the actual operating conditions are identified. In particular, the proposed approach gives the confidence interval for the system settling time, which is used for the real-time optimization of the perturbative maximum power point tracking algorithm. The proposed technique is implemented by using a Field-Programmable Gate Array and it is validated by means of both simulation and experimental results.

There is a growing interest in photovoltaic (PV) systems since they represent a strong option for power supply around the world. Therefore, there is also a growing necessity for developing tools to analyze the behavior of the PV systems under realistic conditions. Hence, better planning, design and operative strategies can be developed. This thesis addresses the issues related with the modeling of PV systems operating under uniform and mismatched irradiance conditions. Moreover, this work considers the PV array connected in different configurations. In this way, the first part of the thesis presents the state-of-the-art in modeling techniques, it including circuital representations of PV cells and modules and its behavior under different scenarios, operation characteristics of different configurations, the effects of the operation under shading conditions, available modeling techniques, among others. The Series-Parallel (SP) is one of the most studied configuration, then some modeling techniques for SP arrays are introduced in this thesis. Such procedures allowed to understand the operation of PV arrays to detect the main aspects that need to be considered in a modeling process. The first technique is based on the ideal single diode model but considers the operation of the modules in the second quadrant by using a linear model to represent the bypass diodes. The approach allows to avoid introducing errors which may cause overestimation in the predicted power when the array is exposed to partial shading conditions. A second approach introduces a combination between the single diode model to represent the modules and a linear model to represent the bypass diodes; the mathematical relationships between the voltages and currents in the modules are typically implicit expression which requires the use of special functions as the Lambert-W function. However, the approach introduced a procedure to avoid the use of such a function, which allows to reduce the computation bur- den. The third approach is based on the single diode model for representing the PV modules and the Schottky model for representing the bypass diode; it proposes a procedure to calculate the maximum power point (MPP) for a given condition operation, without the need of calculating the whole power vs. voltage curve as it is typically performed. Instead, the procedure calculates some points in the neighborhood of the local maximum power points (LMPP) to define the MPP, it providing a fast calculation of the power delivered by the array for a given operating condition. Moreover, the procedure applies the mathematical treatment introduced in the second approach to avoid using the Lambert-W function. Finally, the fourth approach is based on simplified versions of the single diode model and the Schottky model; such versions are named ideal single diode model and ideal switch model, respectively. The main purpose of the approach is to introduce a procedure for modeling the shading considering its dynamic behavior which enables to achieve a more realistic operating condition to calculate the power provided by the array. Other PV configurations, such as the Total Cross Tied (TCT) or the Bridge Linked (BL), may present better performances in comparison with the SP configuration for some opera- ting conditions. However, there is no detailed procedures for modeling such configurations. In fact, the available techniques allow to analyze only one configuration which means that for each configuration a modeling algorithm is required, it making the evaluation of several configuration a complex and time consuming task. In other words, there is not a modeling procedure capable to represent any configuration. Therefore, a general modeling procedure for analyzing any PV configuration operating under uniform or shading conditions is introduced in this thesis. The possibility of studying any connection allows to consider structures without any connection pattern, in this way the thesis introduces the concept of irregular structure as a new option for obtaining improved power profiles at a particular operating condition. The general modeling procedure is a useful tool for reconfigurations analysis, planning and design of PV arrays. All the modeling approaches presented in this work were validated through simulations and experimental tests. Most of them were implemented using Matlab scripts based on widely known programming structures and mathematical functions, those codes can be reproduced in languages such as C and C + + Resumen: Hay un creciente interés en los sistemas fotovoltaicos (PV) debido a que ellos representan una opción fuerte para abastecimiento al rededor del mundo. Por esto, también hay una necesidad creciente de desarrollar herramientas para analizar el comportamiento de dichos sistemas bajo condiciones realistas. Por tanto, mejor planeamiento, diseño y estrategias de operación pueden desarrollarse. Esta tesis aborda los problemas relacionados con el modelado de sistemas fotovoltaicos operando bajo condiciones uniformes y no uniformes. Más aun, este trabajo considera el arreglo fotovoltaico conectado en diferentes configuraciones. De esta forma, la primera parte de la tesis presenta el estado del arte en técnicas de modelado, esto incluyendo las representaciones circuitales de las celdas y modelos fotovoltaicos y su comportamiento en diferentes escenarios, características de operación de diferentes configuraciones, los efectos de la operación bajo condiciones de sombreado, técnicas de modelado disponible, entre otros. La configuración serie paralelo (SP) es una de las estudiadas, por tanto, algunas técnicas para modelar arreglos SP son introducidas en esta tesis. Tales procedimientos permiten entender la operación de arreglos fotovoltaicos para detectar los aspectos principales que se deben considerar en un proceso de modelado. La primera técnica está basada en el modelo ideal de un solo diodo, pero considera la operación en el segundo cuadrante utilizando un modelo lineal para representar el diodo de bypass. Esta aproximación evita errores que provocan sobre estimación en el cálculo de la potencia cuando el arreglo está expuesto a condiciones de sombreado parcial. Una segunda aproximación introduce una combinación entre el modelo de un solo diodo y un modelo lineal para el diodo de bypass; las relaciones matemáticas entre voltajes y corrientes en el módulo son típicamente implícitas lo cual requiere el uso de funciones especiales como la función Lambert W. Sin embargo, la aproximación introduce un procedimiento para evitar el uso de tal funciona, lo cual permite reducir la carga computacional. La tercera aproximación está basada en el modelo de un solo diodo para representar los módulos y el modelo Schottky para representar los diodos de bypass; se propone un procedimiento para calcular el punto de máxima potencia (MPP) para una condición de operación dada sin la necesidad de calcular toda la curva potencia vs voltaje como es realizado normalmente. En cambio, el procedimiento calcula algunos puntos en la vecindad de los puntos máximos locales (LMPP) para definir el MPP, logrando un cálculo rápido de la potencia entregada por el array en una condición de operación. Más aun, el procedimiento aplica tratamiento matemático introducida en la segunda aproximación para evitar el uso de la función Lambert W. Finalmente, la cuarta aproximación está basada en versiones simplificadas del modelo de un solo diodo y el modelo Schottky; tales versiones son llamadas modelo ideal de un solo diodo y modelo de interruptor ideal, respectivamente. El propósito principal de esta aproximación es introducir un procedimiento para modelar la sombra considerando su comportamiento dinámico lo cual permite obtener una condición de operación más realista para calcular la potencia entregada por el arreglo. Otras configuraciones PV tales como la Total Cross Tied (TCT) o la Bridge Linked (BL) pueden presentar mejor desempeño en comparación con la SP para algunas condiciones de operación. Sin embargo, no hay procedimientos detallados para modelar dichas configuraciones. De hecho, las técnicas disponibles permiten analizar solo una configuración lo cual significa que para cada configuración un algoritmo es requerido. Esto haciendo que la evaluación de diferentes configuraciones sea una tarea compleja y que consume mucho tiempo. En otras palabras, no hay un procedimiento de modelado capaz de representar cualquier configuración. Por esto, un procedimiento de modelado general para analizar cualquier configuración operando bajo condiciones uniformes o de sombrado parcial es introducido en esta tesis. La posibilidad de estudiar cualquier conexión permite considerar estructuras sin ningún patrón de conexión, de esta forma esta tesis introduce el concepto de arreglo irregular como una nueva opción para obtener perfiles de potencia mejorados para ciertas condiciones de operación. El procedimiento de modelado general es una herramienta útil para aplicaciones como reconfiguración, planeamiento y diseño de arreglos fotovoltaicos. Todas las aproximaciones presentadas en este trabajo fueron validadas en pruebas de simulación y experimentales. La mayoría de ellas se implementaron en códigos de Matlab basados en estructuras de programación ampliamente utilizadas, estos códigos pueden ser reproducidos en lenguajes como C o C + + Doctorado

The way of implementing an adaptive maximum power point tracking algorithm for photovoltaic (PV) applications in a field programmable gate array (FPGA) is described in this paper. A dual Kalman filter allows estimating the settling time of the whole system, including the PV source and the dc/dc converter controlling the operating point thereof, so that the tracking algorithm self adapts its parameters to the actual weather conditions. The real-time identification need of this application requires an FPGA platform, so that the intrinsic algorithm parallelism is exploited and the execution time is reduced. The tradeoff solutions proposed in this paper, accounting for the algorithm complexity and the limited FPGA hardware, as well as some solutions for optimizing the implementation are described. The proposed adaptive algorithm is implemented in a low-cost Xilinx Spartan-6 FPGA and it is validated through experimental tests.

2013 - 2014 In this thesis two adaptive Maximum Power Point Tracking (MPPT) techniques for PhotoVoltaic (PV) applications, which are based on two different real-time identification procedures are proposed. The algorithms are implemented on the same low-cost Field Programmable Gate Array (FPGA) device in charge of controlling the switching converter that processes the power produced by the PV array. The Perturb & Observe (P&O) algorithm is the most common MPPT technique. Its efficiency is mainly related to two parameters: the perturbation amplitude and the perturbation period Tp. The optimal values of such parameters depend on the PV array type and on the irradiance and temperature conditions thereof, as well as on the parameters of the power processing circuit. Thus, a method for dynamically adapt the P&O parameters would be very useful for increasing the P&O MPPT performances. Several approaches presented in the current literature are focused on the adaptation of the perturbation amplitude. In this thesis, on the contrary, the on-line optimization of the value of Tp is proposed. The effects of such a parameter on both the tracking speed and the stationary MPPT efficiency are pointed out. Besides, the need for a real-time identification technique for identifying the minimum acceptable value of Tp in the actual PV operating conditions is demonstrated. Two different identification procedures aimed at developing the aforementioned adaptive MPPT controllers have been studied: the Cross-Correlation Method (CCM) and the Dual Kalman Filter (DKF). The first one belongs to the non-parametric techniques and allows identifying the impulse response and the frequency response of the PV system. Instead, the DKF is a model-based approach which estimates the states and the parameters of the system. One of the aims of this thesis is to demonstrate the usefulness of these identification procedures for the optimization of the PV P&O MPPT performances. In order to achieve a good trade-off between the desired performances and the cost of the controller, hardware digital solutions, such as FPGA, are adopted. They are able to reduce the execution time by exploiting the intrinsic parallelism of the algorithm to be implemented. Then, in this work, the challenging design of a high performances hardware architecture for the identification algorithms is dealt with. Moreover, the implemented identification techniques are compared in terms of accuracy, identification time and used hardware resources. Several simulations and experimental tests demonstrate the feasibility of the developed identification procedures. In fact, the proposed adaptive MPPT controllers suitably change in few tens of milliseconds the value of Tp ensuring a stable MPPT behaviour. The developed FPGA-based architectures of both the identification techniques is promising for embedding other functions that are of interest in the field of PV systems, e.g. related to on-line monitoring or diagnostic purposes. The work has been developed in co-tutorship between the Systèmes et Applications des Technologies de l’Information et de l’Energie (SATIE) laboratory in the Université de Cergy-Pontoise (France) and the Circuiti Elettronici di Potenza laboratory in the Universitá degli Studi di Salerno (Italy). The work has been supported by the Université Franco-Italienne by means the Vinci project 2013 n. C2-29. [edited by author] XIII n.s.