Improved Fractional-Order Sliding-Mode Voltage Controller-Based MPDPC Strategy for PV Grid-Connected

An improved fractional-order sliding-mode voltage controller is proposed for the problems of system jitter and high total harmonic distortion (THD) of grid-connected current in the model predictive direct power control (MPDPC) strategy for PV grid-connected systems under external disturbances. The algorithm uses fractional order calculus theory in the DC side bus voltage outer loop, firstly, constructs fractional order non-singular fast terminal sliding mode surface function to weaken system jitter and improve system dynamic performance; then constructs fractional order double power exponential convergence law and introduces weighted integral gain and saturation function, which can effectively avoid the increase of switching gain when the system is not in the sliding mode phase and improve system control accuracy; finally, designs The new fractional-order voltage loop controller is applied to the PV grid-connected system. The research results show that the improved fractional-order sliding-mode voltage controller can meet the basic requirements of the grid-connected PV system, effectively suppress system jitter, reduce the grid-connected current THD, and improve the robustness and dynamic performance of the system.