Constrained predictive control based on a large-signal model for a three-phase inverter connected to a microgrid

Abstract

Small-signal models are the mostly used to model and design in inverter-dominated microgrids. Conversely, this paper proposes a large-signal model for grid-forming inverters connected to a microgrid based on the active and reactive power dynamic equations. In this work, it is proposed to use this nonlinear model to develop a constrained predictive control for the inverters connected to a microgrid. The main features of this proposed control are: first, direct voltage control (in amplitude and frequency) is not necessary; second, stability is guaranteed under a wide range of line impedances (hence, the virtual impedance is not needed); and third, the proposed control can operate with unbalanced and nonlinear loads. Moreover, a theoretical stability analysis is presented. Selected experimental results show that the proposed control operates satisfactorily in case of a load step change, a load imbalance, and nonlinear loads.