Enhancing Frequency Stability in Interconnected Microgrids via a Two‐Degree‐of‐Freedom Interval Type‐2 Fuzzy Control Strategy

ABSTRACT

The increasing penetration of renewable energy sources and the large‐scale integration of electric vehicles pose significant challenges to load frequency control (LFC) in interconnected microgrids (IMGs), primarily due to heightened uncertainties and system nonlinearities. To tackle these challenges, this paper presents a novel multi‐loop type‐2 fuzzy inference‐based LFC strategy for coupled MGs incorporating diesel and hydro synchronous generation units. The proposed control framework adopts a two‐degree‐of‐freedom (2‐DoF) multi‐loop architecture, where the 2‐DoF structure separates set‐point tracking from disturbance rejection. In the outer loop, an interval type‐2 fuzzy tilt‐integral‐derivative controller with a filter (IT2FTIDN) is deployed to effectively handle nonlinearities and parameter uncertainties. Meanwhile, the Nie‐Tan (NT) type‐reduction scheme is employed to reduce the computational burden associated with interval type‐2 fuzzy inference. An inner‐loop fractional‐order tilt‐derivative (FOTD) controller is further introduced to improve transient performance and disturbance rejection. The starfish optimization algorithm (SFO) is employed to optimally tune the controller parameters for enhanced frequency regulation under diverse operating conditions. Extensive time‐domain simulations are carried out across diverse operating scenarios involving varying load, generation and parameter conditions. Comparative results show that the proposed IT2FTIDN–FOTD controller significantly outperforms existing state‐of‐the‐art approaches, delivering superior frequency stability, stronger robustness and faster dynamic responses under complex uncertainties. Moreover, the global search capability and robustness of the SFO against premature convergence are validated through comprehensive comparisons with heuristic benchmark algorithms.