*2.1. PV Panel Model*

The equivalent circuit of PV panel module is shown in Figure 1. The relation between current and voltage at output terminal for the PV panel module is expressed as:

$$I\_l / N\_p = I\_p - I\_{SD} \left[ \exp\left(\frac{q\left(V\_l / N\_s + R\_s I\_l / N\_p\right)}{a\_1 k\_B T}\right) - 1\right] - \frac{V\_l / N\_s + R\_s I\_l / N\_p}{R\_{sl}} \tag{1}$$

where *N<sup>s</sup>* and *N<sup>p</sup>* represents the number of solar cells connected in series and parallel respectively. It is clearly depicted from Figure 1 that only five parameters (*Ip*, *ISD*, *a*1, *R<sup>s</sup>* and *Rsh*) are needed to be estimated for minimum value of the RMSE.

**Figure 1.** Equivalent circuit of PV panel module model.
