Le Chau-Duy
This paper presents a three-level F-type power factor correction (PFC) converter employing a fractional-order proportional–integral (FOPI) current controller with enhanced neutral-point voltage balancing capability. The proposed control strategy exploits the additional tuning flexibility of fractional-order control to improve low-frequency current regulation and DC-link capacitor voltage stability in multilevel converters. The steady-state and dynamic performance of the proposed FOPI-based current controller is systematically evaluated and compared with that of a conventional PI controller through time-domain simulations. The results demonstrate that both controllers achieve near-unity power factor and effective DC-link voltage regulation under nominal operating conditions. However, the FOPI-based controller exhibits superior transient performance, faster settling, and significantly reduced DC-link capacitor voltage imbalance during startup, grid voltage disturbances, and load variations. Although the proposed controller introduces a slightly higher low-order harmonic content and current total harmonic distortion, it effectively suppresses the DC component of the grid current, which is a dominant contributor to neutral-point voltage drift in three-level converters. A parametric analysis of the fractional order further reveals its critical influence on current quality and voltage balancing performance. The presented results confirm that the proposed FOPI-based control scheme provides a robust and effective solution for improving neutral-point voltage stability in three-level F-type PFC converters without additional hardware or modulation complexity.