Characterization of Power Optimizer Potential to Increase Energy Capture in Photovoltaic Systems Operating Under Nonuniform Conditions

Power optimizers, which perform power conversion and distributed maximum power point tracking (DMPPT) at the subarray level, are available to mitigate losses associated with nonuniform operating conditions in grid-tied photovoltaic (PV) arrays, yet there is not a good understanding of their potential to increase energy capture. This paper develops and demonstrates a methodology for the use of a detailed software tool that can accurately model both partial shading and electrical mismatch at the subpanel level in a PV array. Annual simulations are run to examine the device-independent opportunity for power recovery in arrays with light, moderate, and heavy shading, and subpanel electrical mismatch variations based on measurements from a monocrystalline silicon array. It is found that in unshaded arrays, the potential energy gain is <1% using power optimizers, but in shaded arrays it increases to 3-16% for panel-level DMPPT and 7-30% for cell-level DMPPT. In the set of simulated cases, panel-level power optimization recovers 34-42% of the energy that is lost to partial shading.