Third-order nonlinear sliding-mode controller for improving the performance of a grid-connected PV system

Abstract

The performance of Photovoltaic (PV) power generation systems, using traditional Vector Current Controllers based on Proportional–Integral Action (CVC-PI), exhibits marked non-linearity and is strongly influenced by meteorological variations. Due to its robustness in the face of these challenges, Sliding Mode Control (SMC) has been widely used in this field, but SMC has certain inconveniences, notably the phenomenon of chattering and ripples in active (P) and reactive (Q) power. These limitations remain partially unresolved, even with the use of Second-order SMC (SMC-2). To address these limitations, this work proposes a robust, non-linear control based on the Third-order SMC in Dual Mode conversion (DM-SMC-3). To demonstrate the effectiveness of the proposed DM-SMC-3 control, a comparative study was carried out between DM-SMC-3, SMC-2, SMC and CVC-PI in terms of chattering reduction, dynamic response time, overshoot, P and Q power ripples and the Total Harmonic Distortion (THD) of the current injected into the electrical grid. The DM-SMC-3 is also used to guarantee Maximum Power Point Tracking (MPPT). The system is designed and simulated using Matlab/Simulink software. The simulation results demonstrated the significant contribution of the DM-SMC-3, with a 99% reduction in overshoot compared to other controllers. THD was reduced to 0.58%. The average reference tracking efficiency was 99.68%, and 99.41% under the temperature and irradiation conditions used. What is more, the DM-SMC-3 takes just 35ms to reach the Maximum Power Point (MPP). It also reduced P and Q power ripples, demonstrating the robustness of the proposed controller in the face of chattering.