Constant power control of grid connected inverters during unbalanced faults

This paper includes the theoretical analysis and experimental validation of a control strategy for the direct power and current control of grid-connected inverters. The studied control strategy allows for constant active and reactive power delivery during unsymmetrical faults and with supply voltage distortion, without the use of a PLL or FLL. It has been proven that only positive sequence current harmonics are necessary to deliver constant P and Q during unbalanced grid faults. The resulting stationary frame control has been experimentally validated during unbalanced voltage sags and swells.