A numerical modeling method of photovoltaic (PV) arrays and PV units is proposed. The method uses the discrete calculation results of PV cell circuit model as the basic data sources. The implementation mechanism of the method and the mathematical model are given in detail. In order to study the shadow shade conditions in PV array operations

shading models of different sizes (single photovoltaic cell

module

string

and array) are developed with simulation results. The results show that under different shading rates

the I-V output characteristic curve of a single PV cell or a module has only one step

and the P-V output characteristic curve has only one power peak. The step number of string’s I-V output characteristic curve is equal to the number of module’s different shading rates

but the power peak number is no more than the step number. The numerical relationship is tested as well. The relationship between the power peak number of PV array and the power peak number of each string is complex. The model is suitable for PV array with different scales and has good simulation flexibility. It can also be easily integrated with power electronic circuits to execute system simulations.