Studies on Diode Effects in Photovoltaic Array under Partial Shading Condition

Partial shading condition (PSC) is an unavoidable complication in the field of photovoltaic (PV) systems. Bypass diodes and blocking diodes have become a standard feature to improve the performance of PV strings or arrays under PSC. However, the output current-voltage (I–V) characteristic varies with different shading patterns, which increases difficulties in theoretical analysis. In this paper, the output characteristics of series string, parallel string and series-parallel (SP) array under PSC are analyzed theoretically. The light levels are extended from simple three-level illumination to N-level illumination. This provides a theoretical basis for constructing the structure of PV arrays and researching the operational process of PV arrays under PSC analytically.