This paper presents characteristics of ideal single diode, practical single diode and two diode equivalent circuit models for modeling of solar photovoltaic cell. Then it presents non-linear mathematical equations necessary for producing I-V and P-V characteristics from a single diode model.
The most common physical models take advantage of the similarity of solar cells and diodes; these are known as the diode models. One-, two- and three-diode models (which describe different charge carrier recombination mechanisms) are available. They are represented by equivalent circuits derived from physical principles [ 8 ].
A PV cell based on the two-diode model is considered in the construction of MG. The two-diode solar PV model yields more accurate results as compared to other existing models, especially at lower illumination levels . Hence the two diode model is considered as an appropriate model for PV cell where its voltage and current are related by:
One of the most used solar cell models is the one-diode model also known as the five-parameter model. This model includes a combination of a photo-generated controlled current source IPH, a diode, described by the single-exponential Shockley equation , and a shunt resistance Rsh and a series resistance Rs modeling the power losses.
The double diode model is derived physically with the concept of a solar cell constructed from polycrystalline silicon with two diodes, and series and parallel or shunt resistances. The shunt resistance, which is due to non-idealities and impurities on the p-n junction while the series resistance represents the losses to the current flow.
One basic equivalent circuit model in common use is the single diode model, which is derived from physical principles (e.g., Gray, 2011) and represented by the following circuit for a single solar cell: The governing equation for this equivalent circuit is formulated using Kirchoff’s current law for current $$I$$: $$I=I_L – I_D – I_ {sh}$$