FPPT and Fixed-Time Sliding Mode Controller for Single-Stage Grid-Integrated PV Systems

This paper presents an FPPT algorithm designed for single-stage grid-integrated PV systems. The FPPT employs an enhanced scanning approach and collaborates with voltage, current, and PLL controllers to optimally harness and transfer predefined or maximum available power from the solar PV array to the grid. A chattering-free fixed-time sliding mode voltage controller is crafted to follow the DC-link voltage reference set by the FPPT. This controller features a refined control law that mitigates chattering—a crucial enhancement since its output serves as the reference for the current controller. A simplified form of a fixed-time sliding mode current controller is also designed to track the current reference. Additionally, a PLL algorithm based on the fixed-time sliding mode is developed to detect the grid voltage phase angle, supporting the inverter controllers. The stability proof of the closed-loop system is analytically obtained by defining a new form of candidate Lyapunov function, which leads to the development of advanced chattering-free, fixed-time nonlinear sliding surfaces, and control laws. Experimental validations and comparative simulations against conventional methods demonstrate the effectiveness of this approach, highlighting its precision, rapid response, and effective chattering reduction, which together improve the accurate delivery of power to the grid.