Fractional-Order Super-Twisting Sliding Mode MPPT Control with Fixed-Time Convergence for Photovoltaic Systems under Partial Shading Conditions.

Abstract

The power-voltage characteristics of photovoltaic systems become nonconvex under partial shading conditions, leading to significant efficiency degradation due to varying solar irradiance and temperature. To address this challenge, an improved finite-time fractional-order super-twisting fast terminal sliding mode control strategy is proposed in this work, achieving fixed-time convergence to the global maximum power point independent of initial conditions. By integrating Caputo fractional calculus with a super-twisting reaching law, the proposed method effectively suppresses chattering while ensuring finite-time stability, with convergence time analytically bounded via Lyapunov theory.Under uniform irradiation, the proposed controller demonstrates significantly improved tracking efficiency compared to conventional methods. In partial shading scenarios, high tracking accuracy and a remarkably fast settling time are attained, confirming the controller's high precision, rapid dynamic response, and strong robustness against environmental uncertainties. The findings indicate that the proposed strategy is a highly effective solution for real-world PV systems under both uniform and partial shading conditions.