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∞ 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∞ controller designed only for a nominal grid impedance condition leads to an unstable closed-loop behavior, while an H∞ 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.