Reference Value Generator of Maximum Power Point Coordinates of the Photovoltaic Panel External Characteristic

摘要

Generally, maximum power point tracking strategies designed to control the solar panels are based on using as references the coordinates of maximum power point of the solar panel external characteristic I(V). The tracking problem makes sense due to the variability of the external characteristic with respect to panel temperature, θ_(PV_P), and total radiation absorbed by the panel, G_(PV_P). This chapter presents a solution to obtain the coordinate of the maximum power point from the variables that may be directly measured: air temperature θ_(air) normal direct radiation G_(h-dir)and diffuse horizontal radiation G_(h-diff). A structure called reference value generator, composed by two blocks, Estimator block and Generator block, is used to calculate the coordinates. The first block estimates from θ_(air) G_(h-dir)and G_(h-diff) the values of θ_(PV_P) and G_(PV_P), while the second generates the desired coordinates.As starting point to develop the model of the solar panel and to extract the maximum power point coordinates, a two diodes electrical circuit was considered. Finally, a generator block consisting in a look-up model is designed. Because for practical cases only a small number of experimental external characteristics are available the generator uses a global interpolation method. The presentation is built on a case study that exploits experimental characteristics taken from references.