*2.1. Main System Configuration*

The main objective of the system configuration illustrated in Figure 1 is to control the PV panel's MPP and force the system to work at this point [16]. This point changes according to the variation of the atmosphere status, including solar radiation and temperature. The PV array's output is linked to the DC-DC converter, which plays a fundamental function in the MPPT process. The circuit component design and the parameter values are given in Table 1. The MPPT controller controls the converter's duty cycle, which in turn controls the array voltage from which the maximum power is acquired and maintained. The output of the systems is connected to a 30 Ω resistive load.

**Figure 1.** System General Configuration illustrated by Simulink model.

**Table 1.** Boost converter design parameters [36].


#### *2.2. Models Specifications*

The simulations performed in this work are linked to the manufacturer's specifications specified at STC for the two cell modules, as mentioned in Table 2. The Current-Voltage and Power-Voltage curves for both cells are presented in Figure 2. As is apparent in *P-V* characteristics, the required MPPs where the maximum power is extracted from the panel are positioned in the curve's peaks.


**Table 2.** PV panels' electrical specifications under standard test conditions (STC).

**Figure 2.** *I-V* (Solid lines) and *P-V* (Dashed lines) characteristics for both MSX60 and ST40 modules.

The incident solar irradiance and temperature influence these characteristic curves. Consequently, a non-linear PV characteristic is observed due to the variation in climatic conditions. This, in turn, causes a considerable change in the MPP position. Notably, the load also influences the MPP. Hence, an MPPT algorithm is highly required to be implemented in the PV system to trace the MPP under varying conditions. Further, to examine the effect of the temperature and solar irradiance fluctuations, the two PV modules are tested and simulated for distinctive temperature and irradiance values. The photocurrent (*Iph*) and the reverse saturation current (*Is*) are formulated by Equations (1) and (2):

$$I\_{ph} = \frac{G}{G\_{STC}} (I\_{sc} + K\_i \left(T - T\_{STC}\right)) \tag{1}$$

$$I\_s = \frac{I\_{\rm sc} + K\_i \left(T - T\_{STC}\right)}{\exp\left(\frac{V\_{\rm sc} + K\_V \left(T - T\_{STC}\right)}{A \ V\_T}\right) - 1} \tag{2}$$

where *A* is the diode ideality factor while *VT* is the thermal voltage and *T* is the temperature in Kelvin. The constants *Ki* and *Kv* are the temperature coefficients of the short-circuit current *Isc* and the open circuit voltage *Voc*, respectively. The solar radiation (W/m2) and the Standard Test Condition (1000 W/m2 and 25 ◦C) are denoted by *G* and STC, respectively. *GSTC* is the solar irradiance under STC (1000 W/m2) and *TSTC* is the temperature under STC (25 ◦C). It can be deduced from the above equations that the photocurrent primarily depends on both the temperature and incident irradiance. On the other hand, the reverse saturation current only depends on temperature. Thus, the variation in irradiance and temperature strongly impacts the current and voltage levels. These implications are displayed in Figures S1 and S2, respectively (see Supplementary Materials).
