Optimised PIDN–FACTS Control for Frequency Stability in Multi-Area Systems with Fuel Cell Integration

Abstract

The growing induction of renewable and cleaner energy sources has made present-day interconnected power grids more complex, where frequency stability and tie-line power control are significant issues. This work presents a realistic two-area interconnected system modelled in MATLAB/Simulink comprising gas, reheat-thermal, and hydro units, with nonlinear consideration and a modified Proportional-Integral-Derivative-Filter (PIDN) controller design. The impact of the inclusion of a Fuel Cell (FC) unit with the grid on frequency stability is analysed, and a coordinated control strategy with Flexible AC Transmission System (FACTS) devices is developed. Several FACTS devices, namely Thyristor Controlled Series Capacitor (TCSC), Unified Power Flow Controller (UPFC), Interline Power Flow Controller (IPFC), and Static Synchronous Series Compensator (SSSC), are designed and integrated with the grid to improve frequency stability. Three population-based optimisation algorithms, viz, Grey Wolf Optimisation (GWO), Artificial Bee Colony (ABC), and Differential Evolution (DE), are used for minimising the cost function, Integral of Time multiplied by Absolute Error (ITAE), for optimal tuning of PIDN and FACTS controllers. A comprehensive study is performed across four scenarios, including single-area and multi-area Step Load Perturbations (SLP). The control performance of each strategy is evaluated based on the obtained ITAE, settling times, peak overshoots, peak undershoots, and rise times. Results demonstrate that GWO outperforms ABC and DE by achieving better control dynamics. Moreover, inclusion of FC achieves a substantial reduction in ITAE compared to conventional approaches, with values as low as 0.002044. FACTS devices further enhance performance, with IPFC consistently achieving the best damping, lowering ITAE to nearly half of the baseline PIDN–GWO values in multi-area disturbances. Overall, the study establishes that coordinated deployment of optimised controllers, FACTS technologies, and cleaner energy sources can significantly strengthen frequency regulation.