Optimized grid-connected three-phase photovoltaic inverter system using cascaded FOPIT-FOPI fractional controller

The global interest in grid-connected photovoltaic (PV) inverters is rapidly increasing, emphasizing their crucial role in sustainable energy systems. As more PV inverters are integrated into modern power grids, challenges related to stability and reliability become more pronounced. This paper presents an innovative dual-component controller, combining a cascaded fractional order proportional–integral-tilt (FOPIT) and a fractional order proportional–integral (FOPI) controller, known as FOPIT-FOPI controller, steered especially for grid-connected PV systems. The FOPIT component manages the DC link voltage of the two-stage inverter system, while the FOPI controller regulates the internal active and reactive current loops of the grid-tied inverter. A novel Marine Predators Algorithm (MPA) based design is employed to fine-tune the controller settings, minimizing the integral time-squared error (ITSE). The effectiveness of this controller is evaluated based on its impact on the rapid tracking of PV maximum power, its robustness during solar irradiance fluctuations, and its resilience to different grid-side requirements. A comparative analysis with a conventional PI controller, conducted using MATLAB/Simulink™, highlights its superior performance. Furthermore, the paper provides a detailed statistical performance comparison of the MPA-based controller design with featured metaheuristic-based algorithms. The results proved the effective employment of MPA in designing the new proposed cascaded FOPIT-FOPI controller.