*2.1. Photovoltaic Panel Module Model*

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

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

where *N<sup>s</sup>* and *N<sup>p</sup>* represent the number of solar cells connected in series and parallel, respectively. *I<sup>l</sup>* stands for cell current in the output, *I<sup>p</sup>* represents the photogenerated current, *ISD* stands for the reverse saturation current. *V<sup>l</sup>* , *a*, *R<sup>s</sup>* , *kB*, *T* and *q* are the cell output voltage, diode ideality constant, series resistance, Boltzmann constant (1.381 × <sup>10</sup>−<sup>23</sup> J/K), junction temperature (◦K), and electron charge (1.602 <sup>×</sup> <sup>10</sup>−<sup>19</sup> C), respectively. It is depicted in Figure 1 that only five parameters (*Ip*, *ISD*, *a*, *R<sup>s</sup>* and *Rsh*) are needed to be estimated for the minimum value of RMSE. <sup>௦</sup> ௌ <sup>௦</sup> − − ௌ <sup>௦</sup> ௦

/൯

ቇ − 1 − /<sup>௦</sup> + <sup>௦</sup>

/

௦

/ = − ௌ ቈ ቆ൫/<sup>௦</sup> + <sup>௦</sup>

**Figure 1.** Single diode model of photovoltaic panel module.
