## 6 Discussion  
According to the results acquired in the preceding subsections, the remarks are as follows:  
1. The proposed TIDN-FOID controller provides the best results compared to PIDN and TIDN for structure-1, including thermal-thermal-biodiesel energy in area-1, thermal-GPPt energy in area-2, and hydrothermal energy in area-3. The results in Figure 4 show the superiority of TIDN-FOID compared to PIDN/TIDN, concerning the diminished level of peak overshoot (\(\Delta f_{1}\) = 0.0004 Hz, \(\Delta f_{2}\) = 0.0003 Hz, \(\Delta Ptie_{2-3}\) = 0.0021 p.u. MW, \(\Delta Ptie_{1-3}\) = 0.0004 p.u. MW), extent of oscillations, peak undershoot (\(\Delta f_{1}\) = 0.0153 Hz, \(\Delta f_{2}\) = 0.0093 Hz, \(\Delta Ptie_{2-3}\) = 0.0004 p.u. MW, \(\Delta Ptie_{1-3}\) = 0.0042 p.u. MW), and settling time (\(\Delta f_{1}\) = 62.36 s, \(\Delta f_{2}\)= 57.44 s, \(\Delta Ptie_{2-3}\) = 57.37 s, \(\Delta Ptie_{1-3}\) = 56.69 s). 2. The results in Figure 5 show the superiority of system dynamics, using performance index ISE, compared to IAE/ITAE/ITSE, concerning the diminished level of peak overshoot (\(\Delta f_{1}\) = 0.0004 Hz, \(\Delta Ptie_{2-3}\) = 0.0021 p.u. MW, \(\Delta Ptie_{1-3}\) = 0.0004 p.u. MW), extent of oscillations, peak undershoot (\(\Delta f_{1}\) = 0.0153 Hz, \(\Delta Ptie_{2-3}\) = 0.0004 p.u. MW, \(\Delta Ptie_{1-3}\) = 0.0042 p.u. MW), and settling time (\(\Delta f_{1}\) = 62.36 s, \(\Delta Ptie_{2-3}\) = 57.37 s, \(\Delta Ptie_{1-3}\) = 56.69 s). 3. In Figure 6, it is observed that the SHO-augmented TIDN-FOID controller provides the lowest value of \(Plx_{ISE}\), i.e., 0.00071; \(Plx_{ISE}\) values for WOA, PSO, CS, and FA are 0.00077, 0.00078, 0.00081, and 0.00083, respectively. Additionally, SHO provides the lowest computational time value. 4. In Figure 7, responses of the systems with and without biodiesel and GPPt are compared. The results in Figure 7 show the superiority of the system with biodiesel and GPP, concerning the diminished level of peak overshoot (\(\Delta f_{2}\) = 0 Hz, \(\Delta f_{3}\) = 0 Hz, \(\Delta Ptie_{1-2}\) = 0 p.u. MW, \(\Delta Ptie_{1-3}\) = 0 p.u. MW), extent of oscillations, peak undershoot (\(\Delta f_{2}\) = 0.009 Hz, \(\Delta f_{3}\) = 0.0012 Hz, \(\Delta Ptie_{1-2}\) = 0.0042 p.u. MW, \(\Delta Ptie_{1-3}\)= 0.0041 p.u. MW), and settling time (\(\Delta f_{2}\) = 52.11 s, \(\Delta f_{3}\)= 53.42 s, \(\Delta Ptie_{1-2}\) = 53.81 s, \(\Delta Ptie_{1-3}\) = 53.22 s). 5. In Figure 8, it is shown that the incorporation of time delay degrades the system. However, in order to make the system reflect real-world conditions, an association of time delay is needed; hence, the rest of the assessments were performed with time delay. With time delay, the level of peak overshoot (\(\Delta f_{1}\) = 0.0005 Hz, \(\Delta f_{2}\) = 0.00046 Hz, \(\Delta Ptie_{1-2}\) = 0.0018 p.u. MW, \(\Delta Ptie_{1-3}\) = 0.0011 p.u. MW), peak undershoot (\(\Delta f_{1}\) = 0.015 Hz, \(\Delta f_{2}\) = 0.011 Hz, \(\Delta Ptie_{1-2}\) = 0.0043 p.u. MW, \(\Delta Ptie_{1-3}\) = 0.0045 p.u. MW), and settling time (\(\Delta f_{1}\) = 68.11 s, \(\Delta f_{2}\) = 67.72, \(\Delta Ptie_{1-2}\) = 63.42 s, \(\Delta Ptie_{1-3}\) = 54.56 s) were much increased. 6. In Figure 9, it is shown that the system with RFB with time delay has a great impact in terms of the diminished level of peak overshoot (\(\Delta f_{1}\) = 0.00001 Hz, \(\Delta f_{3}\) = 0.00001 Hz, \(\Delta f_{2}\), \(\Delta Ptie_{1-2}\) = 0 p.u. MW, \(\Delta Ptie_{1-3}\) = 0.000001 p.u. MW), extent of oscillations, peak undershoot overshoot (\(\Delta f_{1}\) = 0.0141 Hz, \(\Delta f_{3}\) = 0.0061 Hz, \(\Delta Ptie_{1-2}\)= 0.0021 p.u. MW, \(\Delta Ptie_{1-3}\) = 0.0019 p.u. MW), and settling time overshoot (\(\Delta f_{1}\) = 50.11 s, \(\Delta f_{3}\) = 50.21 s, \(\Delta Ptie_{1-2}\)= 49.81 s, \(\Delta Ptie_{1-2}\) = 51.42 s). 7. Eigenvalue assessment was performed to comment on the stability of the system.