A Model Predictive Control-based Flexible Power Point Tracker for Grid-tied Photovoltaic Inverters

In distributed photovoltaic (PV) systems, the grid operator may impose the limit of power injected by the PV system at the point of common coupling. This power limit might be lower than the power generated by the PV system during the peak generation hour. In this work, we propose a flexible power point tracking (FPPT) method based on model predictive control for grid-connected photovoltaic inverters. A finite control set-model predictive controller (FCS-MPC) for the control of the inverter DC bus voltage and the grid current is employed to operate at the desired reference voltage set by the FPPT algorithm and inject the desired PV-generated power into the utility grid. The grid-side controller injects the power with a unity power factor using the voltage-oriented control principle in a rotational d-q reference frame. The rotation of the d-q reference frame is synchronized by the phase-locked loop algorithm. The validity of the proposed control system is confirmed through experimental tests conducted with the aid of solar array and grid simulators, a microlabbox controller, and a two-level inverter paired with an R-L filter.