Nonlinear Backstepping Control for Three-Phase Single-Stage Grid-Tied Photovoltaic Systems via an LCL-Filter

Abstract

This paper examines the modeling and nonlinear control of a Three-Phase Single-Stage Grid-Tied Photovoltaic System (TPSS-GTPS). The system structure is relatively simple, comprising a Photovoltaic (PV) generator connected to the grid through a three-phase Voltage Source Inverter (VSI) and an LCL filter designed to reduce harmonics in the grid current. The primary objective of the control system is to maximize the extraction of power from the Photovoltaic Generator (PVG) and deliver it to the utility grid with a Unity Power Factor (UPF), while ensuring the asymptotic stability of the closed-loop system. In order to achieve these objectives, a novel nonlinear controller was developed in the synchronous dq-frame following the backstepping approach. Evaluating the effectiveness of the designed controller, simulations were performed in the MATLAB/Simulink environment under various scenarios to consider the effects of irradiance and temperature on the PVG. The simulation results demonstrated that the controller successfully achieved all the specified objectives. Additionally, this study highlights the effectiveness of the LCL filter in reducing Total Harmonic Distortion (THD).