EXPERIMENTAL EVALUATION OF ROBUST AND NONROBUST H∞ CONTROLLERS FOR THREE-PHASE GRID-CONNECTED CONVERTERS

The objective of this paper is to compare the performance of two H-infinity state feedback controllers based on linear matrix inequalities for grid-connected converters with LCL filters. The grid impedance is assumed as an uncertain parameter, belonging to a real interval. An H-infinity controller designed only for a nominal grid impedance condition leads to an unstable closed-loop behavior, while an H-infinity controller designed for the entire set of grid impedances, ensures the closed-loop stability, indicating the importance of providing robustness against parametric uncertainties in this application.