*4.4. Test under Ramp Variation in Both Irradiance and Temperature*

Solar radiation and ambient temperature changed simultaneously with random changes during the 1 s period, as presented in Figure 12, to examine the MPPTs process. Before 0.15 s, the irradiation and temperature rose almost simultaneously. After that, at 0.25 s, the irradiation value was maintained at 1000 W/m<sup>2</sup> and the temperature increased from 40 ◦C until it reached 60 ◦C. Reaching 0.54 s, the radiation started to decline until it reached 500 W/m2 at 0.55 s and the system operated at that irradiance until the end of the simulation. At 0.7 s, the temperature started to change and decreased from 60 ◦C to reach 35 ◦C at 0.85 s and remained constant until the end of the simulation time.

**Figure 12.** Simultaneous ramp changes in both (**a**) solar irradiance and (**b**) temperature.

In Figure 13, the performances associated with these changes in irradiance and temperature are presented for both cells. From the observations of the output power curve for both cells, it is observed that the P&O algorithm was less efficient in dealing with these simultaneous ramp changes among the two cells. At the same time, the modified approaches were able to track the MPP through these operating conditions, showing a better dynamic response performance than both traditional P&O and INC algorithms and consequently improving the system efficiency.

#### *4.5. Test under Real Solar Radiation Measurements*

Finally, a test using practical measurement during a relatively dusty or cloudy day was studied. The actual radiation, extracted from REF [41], is shown in Figure 14a, while a focused scaling down of this radiation is shown in Figure 14b, which is used as an input to the simulation. The scaling down is performed due to the limitation of the simulation time. Figure 15 shows the performance of the modified P&O algorithm versus the conventional P&O for the MSX60 module. Furthermore, the theoretical maximum power is shown for comparison. The figure demonstrates the effectiveness of the modified technique, especially for critical times of a sudden increase in irradiation.

**Figure 13.** Performance under simultaneous ramp changes in both solar irradiance and temperature: (**a**) MSX60 (**b**) ST40.

**Figure 14.** Measured solar irradiance during a cloudy weather day: (**a**) Whole day and (**b**) scaling down of solar irradiance to cope with simulation.

**Figure 15.** Performance under influence of scaled measured solar radiation for MSX60. The actual theoretical maximum power is also shown.

Moreover, we performed a comparative study of our modified algorithms and other techniques published in the literature. Table 4 summarizes the comparison in terms of the oscillation level, efficiency, response time during an abrupt increase in irradiation, complexity of implementation, and cost. As illustrated, the proposed methodologies show very fast tracking speeds, higher efficiencies, and neglected oscillations around the MPP. Other techniques may provide a faster response and possible tracking capabilities for partial shading but at the expense of complex implementation and high cost. Furthermore, our proposed techniques can be extended to include the tracking of partial shading as has been proposed in [42]. Regarding future work, adding this feature will be considered to enhance the capabilities of the presented MPPT techniques.


**Table 4.** Comparison of the proposed algorithms with other algorithms proposed in the literature.
