Partial-Shading Assessment of Photovoltaic Installations via Module-Level Monitoring

Distributed maximum power point tracking (DMPPT) is a topic of much interest in improving photovoltaic (PV) system performance. This study uses measured performance data at the module level for 542 PV systems to estimate lost system performance due to partial shade. Because each of the monitored systems is equipped with module-level dc power optimizers, an estimate is made of the overall system shading loss and the performance improvement that the system has received from this use of DMPPT. The estimate of shade extent and performance improvement predicted by this approach is verified experimentally against a system that has site survey images, and measured production with and without module-level electronics. Summary data for this analysis across 542 systems find an average power loss of 8.3% due to partial shading, which would have increased to 13% were the systems not equipped with panel-level optimizers. It is estimated that on average, 36% of the power lost from partial shading has been recovered through use of module-level dc power electronics.