Online Monitoring System for Stand-Alone Photovoltaic Applications—Analysis of System Performance From Monitored Data

Abstract

The Guidelines for the Assessment of Photovoltaic Plants provided by the Joint Research Centre (JRC) and the International Standard IEC 61724 recommend procedures for the analysis of monitored data to asses the overall performance of photovoltaic (PV) systems. However, the latter do not provide a well adapted method for the analysis of stand-alone photovoltaic systems (SAPV) with charge regulators without maximum power point tracker (MPPT). In this way, the IDEA Research Group has developed a new method that improves the analysis performance of these kinds of systems. Moreover, it has been validated an expression that compromises simplicity and accuracy when estimating the array potential in this kind of systems. SAPV system monitoring and performance analysis from monitored data are of great interest to engineers both for detecting a system malfunction and for optimizing the design of future SAPV system. In this way, this paper introduces an online monitoring system in real time for SAPV applications where the monitored data are processed in order to provide an analysis of system performance. The latter, together with the monitored data, are displayed on a graphical user interface using a virtual instrument (VI) developed in LABVIEW®. Furthermore, the collected and monitored data can be shown in a website where an external user can see the daily evolution of all monitored and derived parameters. At present, three different SAPV systems, installed in the Polytechnic School of University of Jaén, are being monitorized and the collected data are being published online in real time. Moreover, a performance analysis of these stand-alone photovoltaic systems considering both IEC 61724 and the IDEA Method is also offered. These three systems use the charge regulators more widespread in the market. Systems #1 and #2 use pulse width modulation (PWM) charge regulators, (a series and a shunt regulator, respectively), meanwhile System #3 has a charge regulator with MPPT. This website provides a tool that can be used not only for educational purposes in order to illustrate the operation of this kind of systems but it can also show the scientific and engineering community the main features of the system performance analysis methods mentioned above. Furthermore, it allows an external user to download the monitored and analysis data to make its own offline analysis. These files comply with the format proposed in the standard IEC 61724. The SAPV system monitoring website is now available for public viewing on the University of Jaén. (http://voltio.ujaen.es/sfa/index.html).