FPPT and Fixed-time Sliding Mode Approaches for a Single-stage Grid-integrated PV System

This article introduces a flexible power point tracking (FPPT) algorithm for a single-stage grid-integrated photovoltaic (PV) system. The proposed FPPT algorithm utilizes the scanning approach, which can operate under partial shading conditions. This algorithm cooperates with the voltage controller, current controller, and phase-locked loop (PLL) to ensure extracting a predefined power (within the maximum available power) from the solar PV array and delivering the extracted power into the grid. To make this possible, the use of new forms of robust fixed-time sliding mode approaches is proposed. A chattering-free fixed-time sliding mode voltage controller is defined to track the DC-link voltage reference provided by FPPT. A simple fixed-time sliding mode current controller is designed to maintain the unity power factor and to track the current reference provided by the voltage controller. A PLL algorithm based on a novel fixed-time sliding mode approach is defined to detect the grid voltage information and provide it to the inverter controllers. Stability analysis of the closed-loop system is given using the Lyapunov theorem. The effectiveness of the suggested scheme is demonstrated using simulation results in comparison with the conventional schemes.