*4.3. Test under an Abrupt Variation in Temperature with Constant STC Irradiance*

Extending our study, to ensure the validity of the MPPTs in reaching the MPP, especially by the modified ones, another operating condition was inspired by [40] and performed on both solar cells using the four MPP tracking algorithms. Specifically, a sudden variation in temperature with a constant STC irradiance (1000 W/m2) was tested, as shown in Figure 10.

**Figure 10.** Sudden temperature change at 1000 W/m2.

With the same value of irradiation (1000 W/m2), the temperature was initially at 25 ◦C and then it suddenly increased to 60 ◦C at *t* = 0.35 s; then, at 0.65 s, a drop in temperature from 60 ◦C to 25 ◦C was applied abruptly; eventually, the temperature was kept steady at 25 ◦C until the simulation time ended at 1 s. In the MSX60 solar cell test, as seen in Figure 11a, first, before 0.35 s, the algorithms completed the STC case as analyzed herein. At 0.35 s, when temperature increased to 60 ◦C, P&O and INC algorithms could track the MPP, with identical reactions in 362 ms with 53.88 W output power, with an approximate error of 12 ms. Furthermore, both modified algorithms converged to a higher MPP of 54.22 W and responded faster than the classical methods, with a similar response time of 356.5 ms and a slight error of 6.5 ms. Moreover, with negligible steady-state oscillations, the updated algorithms can also detect the abrupt drop in temperature that occurred at 0.65 s with a 7.5 ms error and a minor reduction in the power (60.18 W) relative to P&O and INC (60.48 W) in 656.5 ms.

**Figure 11.** Cell performance under temperature sudden variation for (**a**) MSX60 and (**b**) ST40.

Moreover, as presented in the simulation results related to the ST40 panel as seen in Figure 11b, as the temperature increased abruptly to 60 ◦C, all algorithms succeeded in tracking the peak point. The P&O algorithm could reach the MPP of 37.62 W in 357.7 ms. However, the INC algorithm succeeded in tracking the MPP slightly quicker than the P&O algorithm with a tracking time of 357.3 ms but with lower power of 37.03 W. In contrast, both improved techniques can converge faster than the traditional algorithms to the same MPP as P&O had the same response in 354.2 ms and a small error of only 4.2 ms and could minimize the oscillations in the vicinity of the MPP.

Furthermore, the enhanced techniques could also reveal approximately the same power of 40.02 W with a very fast response and a sudden decrease in the temperature with only 0.6 ms. In addition, P&O could reach its MPP of 39.97 W with a response time of 652.5 ms, whereas INC could achieve an MPP of 40.1 W but slower with a time of 654.7 ms. P&O and INC algorithms were able to monitor the peak point, showing the same behavior in the MSX60 cell, while both M-VSS-P&O and M-VSS-INC functioned superiorly with approximately the same response. However, in the ST40 solar cell, according to the observations, both M-VSS-P&O and M-VSS-INC algorithms showed better performance than both P&O and INC in the two sudden temperature changes; but in the case of the temperature increment, the INC algorithm gave slightly less power than the other three algorithms and slightly higher power than the other algorithms when a decrement in the temperature occurred.
