Santiago Silvestre

Global MPPT Scheme for Photovoltaic String Inverters Based on Restricted Voltage Window Search Algorithm

String inverter photovoltaic (PV) systems with bypass diodes require improved global maximum power point tracking (GMPPT) algorithms to effectively reach the absolute maximum power operating point. Several GMPPT algorithms have been proposed to deal with this problem, but most of them require scanning wide voltage ranges of the PV array from nearly zero voltage to open-circuit voltage that increases the scanning time and, in turn, causes energy loss. This paper presents a novel GMPPT method which significantly restricts the voltage window search range and tracks the global power peak rapidly in all shading conditions. Simulation tests and experimental comparisons with another GMPPT algorithm are presented to highlight the features of the presented approach.

Artificial bee colony based algorithm for maximum power point tracking (MPPT) for PV systems operating under partial shaded conditions

An artificial bee colony based MPPT under partially shaded conditions is proposed.Photovoltaic systems are considered.A co-simulation methodology combining Simulink and Pspice has been adopted.Excellent efficiency and tracking performance compared to the PSO-based MPPT.The effectiveness of the proposed method has been confirmed experimentally. Artificial bee colony (ABC) algorithm has several characteristics that make it more attractive than other bio-inspired methods. Particularly, it is simple, it uses fewer control parameters and its convergence is independent of the initial conditions. In this paper, a novel artificial bee colony based maximum power point tracking algorithm (MPPT) is proposed. The developed algorithm, does not allow only overcoming the common drawback of the conventional MPPT methods, but it gives a simple and a robust MPPT scheme. A co-simulation methodology, combining Matlab/Simulink? and Cadence/Pspice?, is used to verify the effectiveness of the proposed method and compare its performance, under dynamic weather conditions, with that of the Particle Swarm Optimization (PSO) based MPPT algorithm. Moreover, a laboratory setup has been realized and used to experimentally validate the proposed ABC-based MPPT algorithm. Simulation and experimental results have shown the satisfactory performance of the proposed approach.

Analysis Model of Mismatch Power Losses in PV Systems

A novel procedure to extract and analyze the power losses, mainly due to mismatch effects, in a photovoltaic (PV) system is presented. The developed model allows the extraction of the main PV module and PV array parameters from I-V characteristics, as well as in dynamic behavior under real conditions of work. The method allows a good estimation of the mismatch effect on the total PV system power losses.

Review of System Design and Sizing Tools

Publisher Summary Sizing is one of the most important tasks during the design of a stand-alone photovoltaic (PV) system. The sizing procedure will determine the power rating of the PV array and the battery storage capacity needed to power the required load; the electrical configuration of the array may also be considered at this stage. More sophisticated sizing procedures will ensure that the reliability of power delivered to the load is appropriate for a given application and optimize the cost of the system. The essential features of photovoltaic system sizing can be understood in terms of the daily energy balance between the daily load and the energy delivered by the array. The reliability of electricity supply is an important factor in PV system design, and this is also reflected in some sizing procedures. One way to quantify the reliability of supply is by a parameter known as the loss-of-load probability, defined as the ratio between the estimated energy deficit and the energy demand over the total operation time of the installation.

Shading effects in characteristic parameters of PV modules

Main characteristic parameters of a PV module present substantial variations in case of partial shading, resulting in important reductions of the output power. A commercial PV module formed by 36 solar cells in series has been tested varying the shadow rate of one of its cells and changes in most important characteristic parameters have been analyzed. Using parameter extraction techniques we have obtained the evolution of series and shunt resistance of the PV module in function of shadow rate.

A fuzzy logic controller for stand alone PV systems

The main objective of this work is to improve the reliability of stand-alone PV systems by applying modern nonlinear control techniques to load management. The control technique implemented is based on load priority assignment and a fuzzy controller having two fuzzy variables and five fuzzy sets. The experimental implementation involved both data acquisition and simulation using LabVIEW and Matlab. The controller works in real time and issues enable/disable orders to the individual loads of the system. A new parameter called weighted loss of load probability (WLLP), which is a weighted sum of the LLP of the individual loads, is introduced in this paper to extend the LLP concept to systems where priorities are assigned at the load side. A comparison of the performance of a fuzzy controller systems versus a conventional system is presented showing that significant improvements of WLLP can be achieved by using this control technique.

Electron-beam-induced reactivation of Si dopants in hydrogenated GaAs: A minority carrier generation effect or an energetic electron excitation effect?

We study the changes in electronic properties of Si-doped GaAs epilayers exposed to a hydrogen or a deuterium plasma, and then submitted to electron-beams of different injection energies (between 10 and 50 keV). Using Hall effect measurements, we have observed the formation of Si–H or Si–D complexes and their dissociation induced by the electron-beam irradiation. A strong isotope effect is observed in the dissociation rate of these complexes. Moreover, increasing injection energy reduces the dopant reactivation efficiency. Both effects are quite difficult to explain assuming minority carrier induced dissociation and could be understood under the light of recent works on electronic excitation of Si–H complexes in GaAs, and also of Si–H (D) bonds at the surface of silicon.

A fast low-cost solar cell spectral response measurement system with accuracy indicator

A novel automated spectral measurement system is presented. Special attention has been focused on the design in order to obtain rapid measurement facilities, minimize hardware and simplify serial communications between the different subsystems involved, resulting in a low-cost measurement system. It is controlled by an HP-9000 computer, through a fully menu-driven interface, and the primary measurement instrument is an HP-4142B modular source-monitor. A new indicator of measurement accuracy is defined, implemented and displayed in real time. This automated system has been employed intensively to study characteristics of different solar cell types in order to optimize their fabrication process. As such this automated measurement system is clearly useful for both research and fabrication.

SPICE macromodeling of photovoltaic systems

SPICE piecewise linear resistor (PWLR) and piecewise current-controlled (PWCC) current source models are applied to represent conventional loads of PV systems, namely, a washing machine, a refrigerator, lights and a d.c.-a.c. converter. The parameter extraction for these models has been performed by experimental measurements. A complete system of 440 Wp has been simulated and the results compared to experimental measurements. Future application advanced dispatching strategies and intelligent load management are indicated as possible uses of these models.

Parameters extraction of photovoltaic module for long-term prediction using artifical bee colony optimization

In this paper, a heuristic optimization approach based on Artificial Bee Colony (ABC) algorithm is applied to the extraction of the five electrical parameters of a photovoltaic (PV) module. The proposed approach has several interesting features such as no prior knowledge of the physical system and its convergence is not dependent on the initial conditions. The extracted parameters have been tested against several static IV characteristics of different PV modules from different manufacturers. In order to assess the effectiveness of the extracted parameters, a dynamic model based maximum power point has been used and compared to real measurements data of a grid connected system located in the Centre de Developpement des Energies Renouvelables (CDER) in Algiers. In addition, comparison of the proposed ABC algorithm with some well-known heuristic algorithms such as, Particle Swarm Optimization (PSO) and Differential Evolution (DE), has given better results in terms of local minimum avoidance and accuracy.