Enhanced jellyfish search-optimized cascaded fuzzy-FOPI control of a three-phase dynamic voltage restorer for power quality improvement

Abstract Power quality disturbances, particularly voltage sags and swells, pose significant challenges to modern distribution networks with increasing penetration of nonlinear loads and renewable energy resources. Dynamic voltage restorers (DVRs) are highly effective custom power devices for mitigating such disturbances; however, their performance depends strongly on the employed control strategy. This paper proposes an advanced hybrid control framework for a three-phase DVR based on a cascaded fuzzy logic controller (FLC) and fractional-order proportional-integral (FOPI) controller, optimally tuned using the Enhanced Jellyfish Search (EJS) algorithm. To overcome the limitations of conventional trial-and-error fuzzy tuning, EJS is employed to optimize 34 hybrid controller parameters (encompassing both the fuzzy membership functions and FOPI gains) by minimizing the integral squared error (ISE) in the synchronous dq reference frame. The proposed controller is validated in MATLAB/Simulink under severe symmetrical and asymmetrical faults, including LLLG, LLG, LL, and LG conditions. Comparative results against conventional PI and non-optimized fuzzy controllers demonstrate superior transient response, voltage restoration, and harmonic suppression. The proposed EJS-optimized Fuzzy-FOPI DVR achieves near-zero overshoot, reduced settling time, and a low total harmonic distortion of 0.76%, satisfying IEEE standards and providing a reliable, high-performance solution for power quality enhancement.