Fractional Order Sliding Mode Control for Active Power Filter Based on Modular Multilevel Converter Integrated with Photovoltaic

The active power filter based on modular multilevel converter (MMC-APF) integrated with photovoltaic (PV) enables better PV integration capability while simultaneously regulating current quality. However, under unbalanced grid conditions, the volatility of PVs and the complexity of the power system pose challenges for restoring current quality. This paper proposes a fractional order sliding mode control (FOSMC) strategy for MMC-APF with PV, which can quickly eliminate harmonic currents under unbalanced grid conditions. First, the mathematical model of the MMC-APF with PV is established. Then, a dual-loop control structure is derived based on the mathematical model. According to the principles of SMC, the inner-loop current controller is designed. The sliding surface is further optimized using FO theory, enhancing the stability of the controller. Finally, in combination with maximum power point tracking (MPPT), the capacitor voltage controller is designed to ensure the stability of PV sub-modules (PSMs) voltages. The proposed FOSMC strategy is validated on the MATLAB/Simulink platform, demonstrating fast response speed, excellent control performance, effectiveness and superiority.