*4.1. Case Study 1*

A small number of experiments are conducted to confirm the present controller's successful operation and resilience. The initial test involves using the PV source to produce 100 kW while maintaining irradiation of 1000 W/m2. The result in Figure 5a can be used to demonstrate that the proposed HHO-AFOPID controller is superior to conventional controllers in terms of quick convergence, short settling times, and minimal oscillation on MPPT. The next test is carried out to generate the same amount of power from the PV source by changing the irradiation from 1000 W/m<sup>2</sup> to 700 W/m2. Here, the proposed controller also proves to be the best and shows its robustness in Figure 5b. Here, the controller also outperforms the aforementioned point of the criterion.

Later, a test was conducted by first turning down the PV source's irradiation intensity to 500 W/m2 and then back up to 850 W/m2. The suggested HHO-AFOPID controller in Figure 5c appears to be the most effective and reliable under these conditions.

As observed in the results, HHO-AFOPID exhibits the highest performance relative to following the MPP with high efficiency and little power loss under both constant and variable irradiation conditions. The magnitudes of *kpi*, *kdi*, *kii* , *μi*, and *λ<sup>i</sup>* are tabulated in Table 3 by incorporating various controllers with the suggested controller.


**Table 3.** Optimally tuned parameters of HHO-AFOPID acquired by horse herd optimization.

**Figure 5.** *Cont.*

**Figure 5.** Experiment of the proposed HHO-AFOPID controller (**a**) under constant irradiation, (**b**) under changing irradiation, and (**c**) under various irradiation levels: 850 W/m2 and 500 W/m2.
