Evaluation of LFC performance in renewable sources-based interconnected power systems using an effective cascade control strategy

Recent energy market liberalization, coupled with its economic and environmental benefits, has resulted in a significant integration of renewable energy (RE) sources into the power system. However, this high penetration of renewables, along with random load demands poses challenges to power system stability. To address these challenges, this paper presents a novel load frequency control (LFC) strategy that uses a recently developed optimization technique known as the sand cat swarm optimization (SCSO) algorithm to optimize the parameters of the proposed (1+PDn)-FOPI cascade controller, with integral time absolute error (ITAE) as the objective function. Initially, a two-area, two-unit non-reheat thermal system, with and without RE sources, is employed to validate the SCSO-tuned (1+PDn)-FOPI control strategy. This analysis is then extended to a more realistic two-area, four-unit hydro-thermal power system, also with and without RE sources. To highlight the superiority of the (1+PDn)-FOPI controller, its performance is compared with various state-of-the-art single and cascade controllers under varying load conditions, system nonlinearities, and RE source fluctuations. The proposed controller achieves a relative improvement of 50% to 70% in the objective function for Test System-1 and 45% to 60% for Test System-2 compared to all other controllers. The controller’s robustness is further confirmed by its stable performance despite a $\pm$20% variation in system parameters. Additionally, the effectiveness of the SCSO algorithm is validated by comparing its performance with the genetic algorithm (GA), differential evolution (DE), and whale optimization algorithm (WOA). Simulation results show that the SCSO algorithm provides a more efficient solution for the LFC problem, while the proposed (1+PDn)-FOPI controller achieves superior performance by reducing oscillations and improving response speed.