Multistage control for frequency and voltage stability in a multi-area power network with nonlinear dynamics

Modern power systems are composed of both renewable and conventional sources, due to mismatch in generation and demand and non-linearities of power system, face significant challenges of load frequency control and voltage regulation, so they require an intelligent control strategy for stable operation. In this regard, the reptile search algorithm (RSA) tuned optimal cascaded two-degree-of-freedom proportional integral control with a proportional derivative filter controller RSA-(CC-2DOF (PI-PDF)) is presented in this study. To ensure stable operation, this controller is employed for load frequency control and automatic voltage regulation. To enhance the stability, an interline power flow controller is integrated into the tie-line between the two areas. For a realistic approach, physical constraints such as generation rate constraints (GRCs) and communication time delays (CTDs) are incorporated into the system and analyzed with and without these constraints. To showcase the efficacy of the controller, its performance is compared with the state-of-the-art optimal controllers and to check the robustness proposed controller is subjected to random load variations. The proposed controller demonstrates superior proficiency as it achieves stabilization of frequency in minimum settling time of 3.21 sec and 13 sec in area 1 & area 2 respectively. This excellent response of controller outpaces the other controllers like IGWO-TID, CMO-FOPID, MFO-PIPD and CBO-PI-(1+PD), which shows much longer settling time i.e. 3.8 sec, - 6.45 sec, 6.2 sec and 3.7 sec for frequency to settle. Likewise, either zero or minimal undershoot and overshoot i.e., 0.00001 approximate to 0 Hz, -5.39 x 10- 3Hz for area 1 and 1 x 10-3Hz, -0.35 x 10- 3Hz for area 2 of the system is observed for the suggested controller in contrast to other controllers, where the highest overshoot of 0.018 Hz is observed for the CMO-FOPID controller. Similarly, for tie line power deviation stable response can be seen within 2.31 sec.Furthermore comparative analysis of performance index i.e. ITAE value of proposed controller turns out to be the lowest i.e. 0.15408 as compare to other controllers (GWO-TID: 0.24128, CMO-FOPID: 1.01393, MFOPIPD: 0.24009 and CBO-PI-(1+PD): 0.19569). This stark comparison shows the unparallel adeptness of the proposed controller in real-world operating conditions in counteracting frequency and voltage fluctuations, not only in the case of abrupt load change but also in the case of parametric variations.