Characteristics of partially shadowed serial PV module output

Based on solar cell current equation and basic circuit theory, the branch output process of the partially shadowed serial solar module with bypass diode was carefully analyzed. The physical output process was divided into two phases: connection and disconnection of the bypass diode. Based on theoretical deduction, the subsection function was applied to accurately describe partially shadowed serial PV module current and power output characteristics. Finally the experiments were carried out for two serial PV module current and power output under non-uniform illumination. The experimental results demonstrate that the proposed method is correct and feasible： the subsection function can accurately describe the current and power output of partial shadowing of serial PV module with bypass diode; the single peak to power output curve, which is the basis of the traditional MPPT (maximum power point tracking), is also inexistent, so it is necessary to carry on improvement to the tracking method.