H∞ repetitive current-voltage control of inverters in microgrids

In this paper, a dual-loop control scheme is proposed for inverters in three-phase four-wire microgrid applications to improve the power quality within the microgrid and the power quality of the current flowing between the microgrid and the utility grid. The control scheme involves an inner voltage loop and an outer current loop, with both controllers designed using the H-infinity repetitive strategy. This leads to a very low total harmonic distortion (THD) in both the microgrid voltage and the grid current. The proposed control structure is experimentally tested under different scenarios (e.g. in the standalone mode or the grid-connected mode, with linear, nonlinear or unbalanced loads etc.) and the it has shown excellent performance.