In small modules, the cells are in placed in series so parallel mismatch is not an issue. Modules are paralleled in large arrays so the mismatch usually applies at a module level rather than at a cell level. For cells or modules in parallel:
Cells connected in parallel. The voltage across the cell combination is always the same and the total current from the combination is the sum of the currents in the individual cells.
Voltage mismatch for two cells in parallel. The individual cells are in red and blue. The green curve is the IV curve of the combination. The VOC of the combination lies between the VOC’s for the individual cells.
An easy method of calculating the combined open circuit voltage (Voc) of mismatched cells in parallel. The curve for one of the cells is reflected in the voltage axis so that the intersection point (where I1+I2=0) is the Voc of the parallel configuration.