Model predictive current control with modified synchronous detection technique for three-phase 3L-NPC multi-functional solar photovoltaic system

In this paper, a model based predictive current control (MPCC) with a modified synchronous detection technique (SDT) is developed for a 3L-NPC multi-functional inverter based solar photovoltaic (SPV) system. This 3L-NPC multi-functional grid tied inverter (MFGTI) perform maximum power point tracking, harmonic compensation, load balancing and power factor control. The proposed SDT consists of two-stages, fundamental component of sensed voltage is extracted using three 1-ph enhanced phase locked loops (EPLL) in the first stage, where as in the second stage, the reactive power injection is controlled by controlling the phase of the injecting currents to operate the point of common coupling (PCC) at the desired power factor. In order to achieve a fast dynamic control, a MPCC is employed for MFGTI. The discrete-time model of three-phase/3L-NPC MFGTI is used to predict the compensation currents for the possible 27 switching-states. The optimal switching-state that minimizes the objective-function is applied in the next sampling instant. The proposed control approach provides fast dynamic response for sudden change in active and reactive powers, high current tracking performance. Simulations are carried out using Matlab/Simulink and the results are presented to highlight the effectiveness of the proposed control technique.