Super twisting sliding mode controller for multi-functional grid-connected inverter in photovoltaic system

In this paper, the performance of a super twisting sliding mode controller (STSMC) is investigated for a multifunctional single-stage inverter that connects a photovoltaic (PV) system to the three-phase utility grid supplying the non-linear load. In this work, the single-stage inverter is controlled to improve power quality by compensating the current harmonics of nonlinear load and to inject maximum power from the PV system to the grid with ST-SMC controller. In this way, the ST-SMC controller is implemented to adjust the DC bus voltage to the value determined by the maximum power point tracking (MPPT) algorithm, as well as to the single-stage inverter current control using the synchronous reference frame theory. According to the simulation results, the ST-SMC controller provides high robustness and better performance in transient and steady state conditions. The results show that the total harmonics distortion (THD) of the grid current is reduced to 1.75% and the DC bus voltage reaches its set-point at 0.08 second with a small amount, approximately 0.05%, of the overshoot. In addition, the superiority and accuracy of the proposed scheme is verified by replacing conventional SMC and PI controllers with super twisting sliding mode controllers. Evaluate the suggested scheme’s performance is done using theMATLAB/Simulink software.