An Explicit Subcell-Based Photovoltaic Model and Its Application in Fault Diagnosis Under Partial Shading Conditions

Photovoltaic (PV) models under partial shading conditions are typically based on the scenario that one whole module or cell is shaded under uniform low irradiance. Nonuniform partial shading on one cell is seldom discussed. However, partial shading in real life is not usually in homogeneous irradiance. To fully examine the PV behavior under partial shading conditions, a cell has to be divided into several subcells to model nonuniform complex shading patterns. Therefore, this article develops a comprehensive mathematical PV model based on a single-diode model covering shading area, shading transmittance, and avalanche breakdown effect on reverse-biased cells. It simulates the output of subcells, cells, submodules, and modules by the calculation of explicit Lambert W function. The proposed model is validated in experimental tests, and its average relative error is under 5%. Compared with other related studies, the proposed model has a decent tradeoff between computation time and model accuracy. The characteristics of the I - V curves based on the proposed model and measured data reveal almost the same information about shading patterns. It demonstrates to be a valuable tool in the application of fault diagnosis.