Lessons learned from testing utility connected by PV systems

Engineers from the Southwest Region Experiment Station (SWRES) have tested over 60 grid-connected, flat-plate photovoltaic (PV) systems in the last six years. The authors examine some common problems that have been observed and present recommendations for improving system reliability. In particular, it is pointed out that there are two common problems that lower energy production in grid-connected PV system: power conditioning system downtime (PCS) caused by fault sensing circuitry, and balance of system failures in the PV array. Another common finding is that manufacturers´ module ratings are over-optimistic, resulting in array outputs that do not meet nameplate ratings. It is found that the alarm circuitry designed to protect the PCS causes unacceptable amounts of system downtime. It is suggested that eliminating as many of the alarm thresholds to a reasonable level, will reduce energy loss. DC switch and fuse failures contribute to losses in the DC portion of PV systems