Low-cost monitoring of photovoltaic systems at panel level in residential homes based on power line communication

Panel-level photovoltaic (PV) monitoring localizes abnormal PV panels, enables easy repair, and helps maintain the performance of the PV system. Panel-level PV monitoring system needs to be low-cost so that it can be widely deployed. Synchronization of monitoring time between PV panels is also needed to compare them under the same conditions. Simple fault detection scheme is needed to decide which PV panel is abnormal. For low-cost modules, this paper proposes a low-cost power line communication (PLC) module to monitor four PV panels simultaneously. It can reduce the cost of monitoring modules down to nearly one fourth according to the cost analysis. For time synchronization, a measurement and query scheme is proposed. At the measurement phase, the states of PV panels are measured simultaneously; at the query phase, the measured data are transferred one by one. For fault detection, the mean voltage of PV panels and voltage drop threshold are used. Voltages below the mean by the threshold are considered as abnormal. The proposed system was tested in the real field; it found and localized an abnormal PV panel. The proposed scheme is expected to widely spread the panel-level PV monitoring and help maintain the PV system performance.