## 4 Experimental Results and Discussion  
After implementing the three different controller designs outlined in Section 3, experiments were conducted, including no-load operation (step response), loading, and unloading tests. The results obtained from the experiments were recorded through the PLC/SCADA interface, and corresponding graphs were generated. For the loading and unloading experiments, instantaneous loading and unloading were conducted instead of gradual changes. This approach aimed to evaluate the response parameters of the SG and controllers under more challenging operating conditions. This section presents the results of the following experiments: initial no-load operation, resistive 1100 W (110%) instantaneous loading and unloading, 550 W (55%) instantaneous loading and unloading, and inductive load 500 VA (pf = 0.8) instantaneous loading and unloading. The results of the initial no-load operation (step response) experiment are shown in Figure 20. For the experiment using the conventional PID (PLC-PID) controller, the maximum frequency observed was 63.03 Hz, with a maximum overshoot of 26.06% relative to the nominal frequency (50 Hz), and the settling time was 28 s. For the experiment using the Fuzzy PID controller, the maximum frequency was 51.03 Hz, with a maximum overshoot of 2.06%, and the settling time was 17 s. In the experiment using the PSO-Fuzzy PID, no overshoot could be observed, and the settling time was reduced to 6 s.  
Figure 19: ITAE value in successive generations of PSO-Fuzzy PID. Figure 20: Step response. Figures 21 and 22 show the results of no-load to 1100 W load (0-110% loading) and 1100 W load to no-load (unloading) experiments, respectively. In the 1100 W loading experiment with the PLC-PID controller, the minimum frequency observed was 48.1 Hz, with a maximum undershoot of 1.9 Hz and a settling time of 20 s. In the experiment with the Fuzzy PID controller, the minimum frequency was 49.07(Hz), with a maximum undershoot of 0.93 Hz and a settling time of 7 s. For the  
Figure 21: The 0–1100 W loading experiment. Figure 22: The 1100–0 W unloading experiment. experiment using the PSO-Fuzzy PID controller, the minimum frequency was 49.17(Hz), with a maximum undershoot of 0.83 Hz and a settling time of 6 s.  
In the 1100 W unloading experiment, the maximum frequency values were 52.3 Hz (maximum overshoot of 2.3 Hz) for the PLC-PID controller, 51.63 Hz (maximum overshoot of 1.63 Hz) for the Fuzzy PID controller, and 51.3 Hz (maximum overshoot of 1.3 Hz) for the PSO-Fuzzy PID controllers. The corresponding settling times were 19 s for the PLC-PID, 9 s for the Fuzzy PID, and 8 s for the PSO-Fuzzy PID controller. Figures 23 and 24 show the results of the no-load to 550 W load (0-55% loading) and 550 W load to no-load (unloading) experiments, respectively. In the 550 W instantaneous loading experiment, conducted with the PLC-PID, Fuzzy PID, and PSO-Fuzzy PID controllers, the minimum frequency values observed were 49.13 Hz (with a maximum undershoot 0.87 Hz), 49.3 Hz (with a maximum undershoot 0.7 Hz) and 49.37 Hz (with a maximum undershoot 0.63 Hz), respectively. The settling time for PLC-PID, Fuzzy PID, and PSO-Fuzzy PID controllers were 13 s, 5 s, and 4 s, respectively. In the 550 W instantaneous unloading experiment, the maximum frequency values for PLC-PID, Fuzzy PID, and PSO-Fuzzy PID controllers were 51.1 Hz (with a maximum overshoot of 1.1 Hz), 50.87 Hz (with a maximum overshoot of 0.87 Hz) and 50.57 Hz (with a maximum overshoot of 0.57 Hz), respectively. The settling times for PLC-PID, Fuzzy PID, and PSO-Fuzzy PID controllers were 13 s, 6 s, and 5 s, respectively. Figures 25 and 26 display the results of the no-load to 500 VA (pF = 0.8) load and 500 VA (pF = 0.8) load to no-load (unloading) experiments, respectively.