The single-stage grid-connected photovoltaic (PV) topology has recently drawn attention as it can reduce overall losses and installation costs. This paper presents a new control approach for single-stage grid-connected PV systems. The proposed controller is a combination of a finite control set model predictive control (FCS-MPC) and a maximum power point tracking (MPPT) algorithm, which ensures the extraction of maximum power from the PV panels and good transient performance for the output voltage and current. The disadvantages of classical MPPT algorithms in tracking the global maximum power point under fluctuating environmental conditions are avoided by including additional constraints in the cost function of the FCS-MPC. Further, the controller is tested for partial shading in PV. The performance of the proposed controller is compared with the two-stage and single-stage PV configuration with different controls and MPPT algorithms. The simulation results show that the single-stage PV system with the proposed control can effectively extract the maximum power from the PV system and maintain a stable output signal for the transient condition. Finally, experimental results according to a control hardware-in-the-loop (C-HIL) approach are presented to validate the effectiveness of the proposed algorithm.

Model predictive control (MPC) as a current controller has gained attention in a grid-connected power electronic converter system. The multi-objective predictive control is in greater demand when the photovoltaic (PV) sources are integrated with the utility grid since the inverter alone must ensure all of the control objectives such as grid current following, constant power factor operation and accurate maximum power point tracking (MPPT) performance. In this regard, this paper aims to implement the multi-objective Finite Set Control (FCS) -MPC for a single-stage grid-connected PV system considering the two-stage system is less cost-effective, more loss and less reliable. Moreover, the classical MPPT fails to extract the maximum power under fluctuating and shaded environmental condition. Therefore, an improved MPPT algorithm is proposed in this work which is again combined with the multi-objective FCS-MPC to ensure the extraction of the maximum power from the PV and good transient performance of the grid-side voltage and current. Two different approaches for the dc-voltage tracking are compared, one is implemented with an outer-loop proportional integral controller and the second one is implemented directly in the MPC objective function. The output findings clearly show the single-stage PV system with the proposed control can ensure a fast and accurate maximum power tracking and maintenance of stable output signal throughout all the transient conditions.

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