## 1 Introduction
In general, whether there is a monitoring system or not, the parameters and magnitudes that are measured must be processed and analysed in order to obtain useful information to extract knowledge to help carry out intelligent supervision of the different elements of the plants and to make decisions in the shortest possible time regarding their operation and integration in the electricity grid or information that helps to improve the design and installation of future plants. Even in the absence of additional measurement sensors, PV plants generally produce a considerable amount of data [75], which creates a complex analysis and performance calculation process [27], so tools are needed to help manage this large volume of data, which, in addition to being acquired, must be processed, stored and analysed easily and effectively [30; 48; 81]. Some authors propose solutions and tools based on Big Data for the analysis of data from PV plants [27; 82; 83], highlighting among other aspects the importance of the correct organisation and storage of the data [78]. A system of this type is inherently complex due to the wide variety of systems and elements that must be integrated [83]. Different PV installations usually have different monitoring elements, with equipment of various models, which can record different types of parameters related to the production of the modules, the operation of the inverter itself, or some parameters of the grid signal, with different notations and/or units of measurement; and all this recorded information can be found in files with different types of formats. Even when monitoring is carried out by the plant's own inverters, all this information does not necessarily have to be homogeneous but usually may vary from one inverter model to another, even within the same company. Some leading companies in system technologies for PV applications, along with their inverter models and monitoring systems, provide Internet portals for the visualisation of the data recorded by their own equipment. These Internet portals provide access to display the data of numerous plants that owners have registered, and even have the option to display them in a shared way so that any user registered in the system can have access to them. However, on such platforms, the parameters that can be displayed and their graphical representations are often pre-configured or the configuration options are often very limited. These applications do allow the downloading of data in formats such as CSV. However, the files that can be downloaded are often highly disaggregated and have an organisation that may vary from one equipment model to another. Therefore, even with the use of these platforms, if you want to carry out a deeper and more personalised analysis of the data contained in these files, it is necessary to be able to manage them in an organised way in order to process all the information they contain. In this context, the aim of this work is the development and implementation of an application to store, in an orderly and automated way, all the data files from the monitoring of the inverters of a set of PV plants, and to have access to them in a flexible and versatile way, in order to be able to process the data and analyse them in a much more detailed and in-depth way. The need arises from the agreement between the authors' research group and the company called Solar del Valle S.L., whose activity consists of the installation and O&M of PV plants, in order to be able to make use of the data recorded in these plants and to be able to take advantage of all the information hidden in them. The work has resulted in a tool, called _S-lar_ 2, which has allowed us to analyse the data recorded by the inverters and additional sensors in a group of PV plants. An earlier version of this tool is available in some previous publications [79; 80].