## 4 Experimental Results and Discussion
In the 500 VA instantaneous loading experiment, performed with PLC-PID, Fuzzy PID, and PSO-Fuzzy PID controllers, the minimum frequency values were 49.17 Hz (with a maximum undershoot of 0.83 Hz), 49.37 Hz (with a maximum undershoot of 0.63 Hz), and 49.5 Hz (with a maximum undershoot of 0.5 Hz), respectively. The settling times for PLC-PID, Fuzzy PID, and PSO-Fuzzy PID controllers were 15 s, 9 s, and 7 s, respectively. Figure 23: The 0–550 W loading experiment. In the 550 VA instantaneous unloading experiment, the maximum frequency values for PLC-PID, Fuzzy PID, and PSO-Fuzzy PID controllers were 50.83 Hz (with a maximum overshoot of 0.83 Hz), 50.67 Hz (with a maximum overshoot of 0.67 Hz), and 50.63 Hz (with a maximum overshoot of 0.37 Hz), respectively. The settling times for PLC-PID, Fuzzy PID, and PSO-Fuzzy PID controllers were 16 s, 12 s, and 8 s, respectively. Figure 24: The 550–0 W unloading experiment. Figure 25: The 0–500 VA (pf = 0.8) loading experiment. The results obtained using PLC-PID, Fuzzy PID, and PSO-Fuzzy PID controllers are given in Tables 5 and 6 for loading and unloading, respectively. The experimental results demonstrate that the PSO-Fuzzy PID controller is better than the Fuzzy PID and PLC-PID controllers. In the 1100 W (110%) instantaneous loading experiment, the PSO-Fuzzy PID controller achieved a settling time of 6 s and a maximum overshoot of 0.83 Hz, while the PLC-PID controller had values of 20 s and 1.9 Hz, respectively, and the Fuzzy PID controller showed 7 s and 0.93 Hz. Furthermore, the PSO-Fuzzy PID controller exhibited the lowest maximum oscillation and settling time in the 550 W (55%) and 500 VA inductive load experiments compared to all the methods. During the experiments, loading and unloading experiments were conducted under harsh conditions with instantaneous and large load fluctuations (55% and 110% of nominal power). Such instantaneous load fluctuations in real power systems are rarely observed at \begin{table}
\begin{tabular}{c c c c c c c} \hline  & \multicolumn{3}{c}{**Settling Time (s)**} & \multicolumn{3}{c}{**Max. Overshoot (\%)**} \\ \cline{2-7}
**Experiment** & **PLC-** & **Fuzzy PID** & **PSO-Fuzzy PID** & **PLC-** & **Fuzzy PID** & **PSO-Fuzzy PID** \\ \hline
1100–0 W & 19 & 9 & 8 & 4.6 & 3.26 & 2.6 \\
550–0 W & 13 & 6 & 5 & 2.2 & 1.74 & 1.14 \\
500–0 VA & 16 & 12 & 8 & 1.66 & 1.34 & 1.26 \\ \hline \end{tabular}
\end{table} 
Table 6: PID and aABC Fuzzy PID comparison for unloading experiments. \begin{table}
\begin{tabular}{c c c c c c c} \hline  & \multicolumn{3}{c}{**Settling Time (s)**} & \multicolumn{3}{c}{**Max. Overshoot (\%)**} \\ \cline{2-7}
**Experiment** & **PLC-** & **Fuzzy PID** & **PSO-Fuzzy PID** & **PLC-** & **Fuzzy PID** & **PSO-Fuzzy PID** \\ \hline
0–1100 W & 20 & 7 & 6 & 3.8 & 1.86 & 1.66 \\
0–550 W & 13 & 5 & 4 & 1.74 & 1.4 & 1.26 \\
0–500 VA & 15 & 9 & 7 & 1.66 & 1.26 & 1 \\ \hline \end{tabular}
\end{table} 
Table 5: PID and aABC Fuzzy PID comparison for loading experiments. Figure 26: The 500–0 VA (pf = 0.8) unloading experiment. these levels. With the proposed control method, under smaller or gradual load fluctuations (10% or 20% of nominal power), frequency fluctuations (overshoot and undershoot values) were observed to be 0.5 Hz or less, and the settling times were 3 s or more. It was observed that overshoot and settling time values were higher in experiments performed with inductive loads compared to experiments performed with resistive loads of the same or similar values. Standard frequencies are defined in the IEC 60196-2009 standard [68]. Although national regulations may vary, power systems generally allow frequency fluctuations of \(\pm\)1% (0.5 Hz). Therefore, frequency values ranging from 49.5 to 50.5 (Hz) are considered acceptable. Based on this, a settling time of less than 3 s is acceptable, even under the most challenging conditions (110% instantaneous load). In the 110% instantaneous load experiment conducted using the PSO-Fuzzy PID controller, the frequency was consistently maintained within the acceptable range.