Load Frequency Regulation for Thermal Units Integrated with Renewable Energy Sources and Energy Storage Systems

This paper presents an advanced load frequency regulation strategy for interconnected thermal power systems integrated with renewable energy sources and energy storage systems. A two-area non-reheat thermal power system is investigated, where photovoltaic generation is incorporated in Area 1 and wind turbine generation in Area 2 to assess the impact of renewable penetration on system dynamics and frequency stability. To improve the dynamic response under varying operating conditions, a novel multi-stage TDn(1+PIDn) controller is proposed. The TDn stage enhances transient shaping, while the PIDn stage provides superior damping and steady-state accuracy. The controller parameters are optimally tuned using the pied kingfisher optimizer (PKO) and compared with particle swarm and grey wolf-based optimizers. Furthermore, vanadium redox flow batteries, superconducting magnetic energy storage, and hydrogen–air fuel cells are integrated into the hybrid system to mitigate frequency oscillations caused by renewable intermittency. Offline simulations and real-time validation using the OPAL-RT OP4512 simulator are conducted under different dynamic scenarios. The obtained results demonstrate that the proposed PKO-TDn(1+PIDn) method achieves the best transient performance, for example, reducing the ∆F1 overshoot, undershoot and settling time by 28%, 15% and 7.5%, respectively, relative to its closest-performing counterpart while attaining the minimum ITAE value of 0.037309. Consistent improvements are observed across the key performance metrics, confirming the robustness and effectiveness of the scheme for modern hybrid power systems.