A practical technique for on-line monitoring of a photovoltaic plant connected to a single-phase grid

•Automatic detection of main faults in PV systems is presented and tested.•Specific indicators detect bypass module, open-circuit string and partial shading.•The strategy efficiency is validated by experiments for two days.•The strategy allows the number of faulty PV modules and strings to be determined.•The method is effective and minimizes the use of sensors in the monitoring system. Improving the reliability and enhancing the performance of photovoltaic (PV) plants are important objectives that increase the competitiveness of the PV systems, especially for grid connected PV plants, for which, every kilowatt-hour is crucial, since only kilowatt-hours that are fed into the grid are remunerated. Therefore, monitoring and automatic faults detection during the PV panels operation are necessary to ensure the optimal use of the energy generated by the PV plant, and to provide a reliable power supply. In this research paper, two current and voltage indicators are used to analyze and to distinguish, in real-time, the faults related to bypassed PV modules, open-circuits strings and partial shading for a PV plant connected to a single-phase grid. Moreover, the presented strategy allows determining the total number of faulty PV modules and/or strings. The efficiencies of these indicators are tested by experiments, using a Control and Data Acquisition System, which proved the effectiveness of the proposed approach.