Subcell Modeling of Partially Shaded Photovoltaic Modules

Increased photovoltaic installations in densely built-up areas give rise to non-uniform irradiation causing partial shading. Non-uniform irradiation further leads to non-uniform temperature, leading to a reduction in output and the formation of deteriorating hotspots. A detailed model involving subcell level behavior is pivotal in understanding the impact of partial shading. In this paper, such a model is developed that analyzes the output of photovoltaic (PV) modules under different translucent and opaque shades while incorporating the diffused light effects. This model further includes the temperature variation of the module and also captures the bypass diode characteristics. The proposed model is experimentally validated for horizontal, vertical, slant, and patch shading patterns with varying shading intensities. This subcell model is shown to perform better than four existing methods of partial shading output prediction. It improves the output open-circuit voltage and short-circuit current prediction accuracy by more than 10% when compared with the average irradiance-based modeling approach, which is the best among the existing methods. Overall, an output prediction accuracy of more than 93% is achieved for opaque shading and more than 95% for translucent shading. As this paper provides the output of PV modules under partial shading, it finds direct application in partial shading detection, prevention of hotspots, and global maximum power point tracking, thereby enhancing their life and efficiency.