Comparative Analysis, Modeling, and Experimental Validation of Current Regulation Strategies for a Grid- Tied Inverter with LCL Filter

Current regulation strategies for a grid-tied inverter with LCL filter in both stationary and synchronous reference frames are presented. Analytical models of the proportional-integral controller in the synchronous reference frame (Sy-PI), a stationary reference frame regulation strategy of synchronous reference frame current controller (St/Sy-PI), and the proportional resonant controller in the stationary reference frame (St-PR) are established. Detailed analysis reveals that these current regulators are inherently different. However, the perceived resemblance that appears in the literature amongst these three controllers is established by underlining the effect of cross-coupling elements which results in an identical forward path transfer function. Bode plot and root locus analysis are presented to determine the stability limits of control parameters. The results of current regulation strategies are validated using PSIM and verified by employing controller hardware in the loop with Typhoon.