Number of maximum power points in photovoltaic arrays during partial shading events by clouds

This article presents a study of the number of maximum power points (MPPs) of photovoltaic (PV) module arrays during partial shading events by clouds. Around 9000 shadow edges were identified in measured irradiance data, and the electrical characteristics of 250–500 PV module arrays with different configurations were studied during the irradiance changes. It was found that most of the partial shading events caused by clouds do not cause multiple MPPs for PV arrays, even for a moment. The number of MPPs was found to decrease with the increasing number of parallel-connected PV strings, but to increase strongly with the increasing length of the strings. According to the results, the use of a total-cross-tied electrical PV array configuration leads to worse system performance compared to a simple series-parallel configuration during partial shading events. Dark shadows with sharp edges moving parallel to the PV strings caused the largest MPP numbers, up to 20. The results show that energy losses due to operation at a local MPP instead of the global one during partial shading events by clouds have only a minor effect on the total energy production of PV arrays.