Comparación de estrategias de control para sistemas MPPT: optimización de la potencia entregada a la carga vs optimización de la potencia extraída del generador fotovoltaico

Abstract

espanolLos sistemas de seguimiento del punto de maxima potencia (MPPT) tratan de maximizar el rendimiento de una instalacion fotovoltaica mediante el ajuste dinamico del ciclo de trabajo (δ) del convertidor CC/CC empleado para conectar el generador con la carga. Tradicionalmente, el algoritmo de control empleado para la definicion del ciclo de trabajo determina el valor de este parametro con objeto de maximizar la potencia generada por el generador fotovoltaico. Estas tecnicas no tienen en cuenta el caracter no ideal del convertidor CC/CC, cuyo rendimiento real depende tambien del ciclo de trabajo (δ) con el que opera. Considerando las caracteristicas del convertidor CC/CC no puede afirmarse, a priori, que el metodo que optimiza la generacion de potencia del generador fotovoltaico maximiza tambien la entrega de potencia en la carga, objetivo final de un sistema MPPT. Este trabajo adapta el ampliamente extendido algoritmo "Perturbacion/Observacion, P&O" para optimizar la entrega de potencia en la carga, midiendo las variables que determinan el comportamiento del algoritmo a la salida del convertidor CC/CC, y compara el rendimiento obtenido con el que se obtiene con el planteamiento clasico de optimizacion de la potencia entregada por el generador fotovoltaico, en el que la medida de las variables que determinan el funcionamiento del algoritmo se realizan en la entrada del convertidor CC/CC. Se ha analizado un sistema fotovoltaico que emplea un convertidor boost para conectar el generador fotovoltaico (PVG) con la carga, el cual ha sido sometido a condiciones atmosfericas variables, en cuanto a radiacion y temperatura, y a distintos requerimientos de consumo de carga, obteniendo los rendimientos ofrecidos por el sistema para las dos filosofias de control. Estos resultados se discuten para determinar si hay una perdida significativa de rendimiento en el planteamiento clasico frente a la nueva propuesta y la conveniencia de desarrollar sistemas que optimicen la potencia util, esto es, la entregada a la carga EnglishThe maximum power point tracking systems (MPPT) try to maximize the performance of a photovoltaic installation by dynamically adjusting the duty cycle (δ) of the DC/DC converter used to connect the generator to the load. Traditionally, the control algorithm used to define the duty cycle determines the value of this parameter in order to maximize the power generated by the photovoltaic generator. These techniques do not take into account the non-ideal character of the DC/DC converter, whose real efficiency also depends on the duty cycle with which it operates. Considering the characteristics of the DC/DC converter can not be said, a priori, that the method that optimizes the power generation of the photovoltaic generator also maximizes the power delivery in the load, the final objective of an MPPT system. This work adapts the well-known algorithm "Perturbation / Observation, P&O" to optimize the delivery of power in the load, measuring the variables that deterThe maximum power point tracking systems (MPPT) try to maximize the performance of a photovoltaic installation by dynamically adjusting the duty cycle (δ) of the DC/DC converter used to connect the generator to the load. Traditionally, the control algorithm used to define the duty cycle determines the value of this parameter in order to maximize the power generated by the photovoltaic generator. These techniques do not take into account the non-ideal character of the DC/DC converter, whose real efficiency also depends on the duty cycle with which it operates. Considering the characteristics of the DC/DC converter can not be said, a priori, that the method that optimizes the power generation of the photovoltaic generator also maximizes the power delivery in the load, the final objective of an MPPT system. This work adapts the well-known algorithm "Perturbation / Observation, P&O" to optimize the delivery of power in the load, measuring the variables that determine the behavior of the algorithm at the output of the DC / DC converter, and compares its performance with the performance that it is obtained with the classical approach of optimizing the power delivered by the photovoltaic generator, in which the measurement of the variables that determine the operation of the algorithm are made at the input of the DC / DC converter. A photovoltaic system that uses a boost converter to connect the photovoltaic generator with the load has been analyzed, which has been subjected to variable atmospheric conditions, in terms of radiation and temperature, and to different load consumption requirements, obtaining the performances offered by the system for the two control philosophies. These results are discussed to determine if there is a significant loss of performance in the classical approach with respect to the new proposal and the convenience of developing systems that optimize the useful power, that is, the power delivered to the loadmine the behavior of the algorithm at the output of the DC / DC converter, and compares its performance with the performance that it is obtained with the classical approach of optimizing the power delivered by the photovoltaic generator, in which the measurement of the variables that determine the operation of the algorithm are made at the input of the DC / DC converter. A photovoltaic system that uses a boost converter to connect the photovoltaic generator with the load has been analyzed, which has been subjected to variable atmospheric conditions, in terms of radiation and temperature, and to different load consumption requirements, obtaining the performances offered by the system for the two control philosophies. These results are discussed to determine if there is a significant loss of performance in the classical approach with respect to the new proposal and the convenience of developing systems that optimize the useful power, that is, the power delivered to the load