Quantitative estimation of mismatch losses in photovoltaic arrays under partial shading conditions

Abstract

Partial shading can significantly reduce the output power of photovoltaic (PV) arrays due to mismatch losses. The mismatch losses mainly depend on the shading levels of shaded modules in the PV array. A judgment method for the states of the blocking diodes in PV modules under partial shading conditions is presented to quantify the electrical mismatch losses of PV arrays. A single diode model without any approximation is employed to find the electrical parameters of PV modules precisely from the manufacturer’s datasheet. The output characteristics of PV arrays at maximal power conditions are determined with the Lambert W function. The overall effect of the mismatch losses caused by partial shading on the output power of PV arrays with blocking diodes protection is analyzed in detail. Three types of PV arrays are utilized to quantify the mismatch losses in PV arrays under partial shading conditions. Simulation results indicate that the conventional crystalline technologies are more affected by partial shading than the thin-film technology. The PV arrays suffer from various degrees of power mismatch under partial shading conditions.