ANFIS-driven MMC-UPQC With Renewable DC-link Support for Harmonic and Sag–Swell Compensation

This paper presents an Adaptive Neuro-Fuzzy Inference System (ANFIS)-controlled Modular MultilevelConverter-based Unified Power Quality Conditioner (MMC-UPQC) designed to enhance voltage and current quality in distribution systems subjected to severe nonlinear and dynamic disturbances.In the proposed configuration, a photovoltaic (PV) generator is coupled directly to the DC link of the MMC-UPQC, enabling the system to utilize renewable power for compensation while providing a stable DC-link voltage.The study evaluates the functioning of the ANFIS-controlled MMC-UPQC under three representative scenarios: distorted grid voltage conditions, balanced and unbalanced voltage sag-swell disturbances, and abrupt nonlinear load variations.Detailed MATLAB/Simulink simulations support that the proposed controller provides enhanced harmonic mitigation, voltage regulation, and transient response compared to conventional strategies.Under harmonic-rich grid conditions, the ANFIS-controlled series converter restores a nearly sinusoidal load voltage, while the shunt converter ensures sinusoidal grid currents despite nonlinear load behaviour.During sag-swell disturbances, the proposed controller exhibits rapid and precise compensating action, maintaining balanced and regulated load voltage even under deep and asymmetric deviations.Furthermore, during sudden load increments, the ANFIS-controlled MMC-UPQC effectively stabilizes the load voltage, filters harmonic currents, and ensures smooth instantaneous power exchange between the grid, PV system, and load.Quantitative analysis shows substantial performance improvements, including lower load voltage Total Harmonic Distortion (THD) (0.76%), reduced source current THD (0.65%), minimal DC-link ripple (0.05%), and faster dynamic convergence compared to conventional controllers.The results confirm that integrating ANFIS intelligence with MMC-UPQC technology and PV-supported DC-link operation provides a highly robust and adaptive solution for next-generation power distribution systems requiring enhanced power quality and renewable energy utilization.