Universal Constrained Power Flow Control for Four-Wire Grid-Tied Power Electronics Converters

Low-voltage four-wire grids have undergone significant changes in recent decades. New power electronics-based resources have been integrated into the system, enhancing its flexibility but also impacting its stability and safety. As a result, modern control strategies must consider safety aspects and directly contribute to converter protection while supporting the network during faults. In this paper, we build upon the nonlinear model predictive control formulation proposed in [1] for three-wire systems and tackle the control design challenges and performance requirements that are present in four-wire grid-connected power electronics converters. This entails not only extending the modeling to describe the dynamics of the system's common-mode components, but also capturing the coupling of the different variable components through the control problem's constraints. The new extended formulation is tested through simulations of both symmetrical and asymmetrical faults, showing effective current and voltage limitation while performing as demanded by grid codes.