Enhancing energy quality and grid stability with improved adaptive controller for renewable energy conversion systems under weak grid conditions

This work presents a systematic procedure for the parameterization of a robust adaptive proportional-integral controller applied to a grid-tied inverter with an LCL filter. The controller parameterization uses the Tasmanian devil optimizer, driven by performance indexes and controller stability constraints in the formulation of the optimization problem. Simulation results considering the renewable energy conversion system subject to periodic exogenous disturbances, grid impedance variations, and system uncertainties representing critical situations of real systems are presented. The optimized controller allows current tracking in less than one grid cycle (around 9 ms) during the initial transient regime, and when the grid inductance changes around 4.33 times the nominal value (from 0.3 mH to 1.3 mH), the transient regime ends in 11 ms without significant overshoot. Two extreme scenarios were also considered: when the grid inductance increases 17.66 times (from 0.3 mH to 5.3 mH) and 34.33 times (from 0.3 mH to 10.3 mH). The duration of transient regimes was again less than one grid cycle. Moreover, there are no significant tracking errors in the transient regimes associated with current reference changes, and the tracking error tends to a residual value in steady state in all scenarios, with values on the order of 10⁻⁶.