Juan David Bastidas-Rodriguez

Reconfiguration analysis of photovoltaic arrays based on parameters estimation

Abstract A method to determine the photovoltaic (PV) series–parallel array configuration that provides the highest Global Maximum Power Point (GMPP) is proposed in this paper. Such a procedure was designed to only require measurements of voltage and current of each string, which avoids to perform experiments in each module. The ideal single-diode model parameters of each module in the string are obtained from the analysis of the voltage vs. current characteristics of the string. Using the estimated parameters, all feasible PV array configurations are evaluated to determine the array configuration that provides the highest GMPP. Finally, the proposed solution is validated using simulations and experimental data.

A genetic algorithm for identifying the single diode model parameters of a photovoltaic panel

In this paper the identification of the single-diode model of photovoltaic (PV) generators operating in outdoor conditions has been carried out. The non-linear equation system, describing the PV source in five operating points, is re-written as an optimization problem and it is solved by using a genetic algorithm. The parameters of the single-diode model are evaluated for different combinations of irradiance and temperature conditions. Contrary to several approaches proposed in literature such analysis shows that all the parameters need to be adjusted with respect to the environmental conditions to reduce the errors in the current, power and energy predictions.

Model-Based Degradation Analysis of Photovoltaic Modules Through Series Resistance Estimation

The long power production warranties guaranteed by the manufacturers of photovoltaic (PV) modules (25 years) are a vital factor for the economical viability of PV systems. Nevertheless, recent studies have demonstrated that the modules may experience an early degradation, which turns into the reduction of the power production or even the damage of the entire PV module. In this paper, a method aimed at detecting the module degradation is introduced. It detects and quantifies the degradation by means of two indicators, which are aimed at estimating the increment of the modules series resistance, this parameter being one of the most affected by some degradation mechanisms. The increase of the series resistance value is estimated through the evaluation of the error in predicting the position of the maximum power point, which is obtained by comparing the experimental measurements with the single-diode model. The proposed method is experimentally validated, and it is compared with other methods reported in the literature. The results show that the proposed indicators are able to accurately estimate the increments of the series resistance with a low sensitivity to the irradiance and temperature values. This feature improves the accuracy and the reliability of the diagnosis processes and monitoring systems.

Photovoltaic modules diagnostic: An overview

Diagnostic functions will be making the difference in photovoltaic systems. The need of a daily, monthly and yearly quantification of the energy produced by a plant is a feature required by the customers for comparing the actual performances of their system with the expected values in order to quantify the real return on investment time. In some cases, monitoring facilities are offered by the producers of the power processing system but some companies also offer power production monitoring as a service. The power and energy monitoring is a first step towards a more complete diagnosis of the photovoltaic modules and prognosis about the expected lifetime, which would be welcome by the market. The modules productivity is a too coarse information for understanding the problems affecting the modules and for performing the right repairing. Thus, new and even more advanced diagnostic algorithms must be developed in order to monitor the status of the cells and to predict failures before they lead to a significant reduction on the energy produced by the module. Such failures might be not only due to cells malfunctioning, but also to faults of the bypass diode the module is equipped with. This might happen due to repeated shadowing or to lightning. In this paper the techniques for photovoltaic modules diagnosis proposed in the recent literature are overviewed. The main features of some commercial products are also given. Some elements to be used as a starting point for the development of algorithms for diagnostic and prognostic purposes at module level are proposed.

Quantification of photovoltaic module degradation using model based indicators

One of the most important characteristics of the photovoltaic (PV) modules is their long lifetime (around 25 years). However, recent investigations have shown that PV modules may suffer significant degradation before that time; that is why the development of diagnostic techniques is important for the customers of PV systems. In this paper two indicators to quantify the degradation of a PV module are presented. Such indicators use the single-diode model to represent a PV module without degradation and combine such information with the experimental measurements to estimate the increase in the series resistance and/or the decrease in the parallel resistance with respect to reference values. The estimation of those variations allows the quantification of the module degradation. Simulation results comparing the proposed indicators with the fill factor (a traditional indicator to quantify the electrical quality of a PV module), and other indicators to estimate the series resistance are presented to illustrate the advantages of the proposed indicators.

Cargador de baterías fotovoltaico con control por modos deslizantes y limitación de la derivada de corriente de carga

In stand-alone photovoltaic (PV) systems, battery chargers are important to guaranteethe energy supply when sunlight is not available. Such chargers need to track the maximumpower point (MPPT) and limit the derivative of the batteries’ charging current to extendtheir lifetime. This paper proposes a battery charging system composed of a Buck converter,a cascade control of the battery current and the PV panel voltage, and the Perturb andObserve (P&O) MPPT technique. P&O generates the reference of the panel voltage for theexternal loop of the cascade control implemented with a P regulator, whose control action isthe reference of the batteries’ charging current. Such current reference passes through aderivative limiter before reaching the internal current control loop, which is implementedby a sliding-mode controller (SMC). This paper includes transversality and reachabilityanalyses of the SMC, as well as the procedure to design the P regulator. The proposedsystem is validated by simulations in PSIM software to show its capacity to perform MPPTand limit the battery’s charging current derivative at the same time.

Modelo Matemático de Arreglos Fotovoltaicos en Puente-Vinculado Operando bajo Condiciones Irregulares

Resumen en: This paper presents a mathematical procedure to model a photovoltaic array (N rows and M columns) in bridge-linked configuration operating under regular ...