Adaptive active fractional-order damping strategy for ensuring stability and energy quality in sustainable generation

This work presents a novel advanced adaptive fractional-order control strategy for grid-tied power inverters with an LCL filter, a common setup in renewable energy conversion systems. The developed control technique merges the structure of the fractional-order proportional–integral–derivative (FOPID) controller and a robust model reference adaptive control philosophy, resulting in a completely novel approach to the adaptive FOPID control framework. The resulting controller is applied to the grid-injected current regulation of the power system. Stability proofs in discrete-time by means of the Lyapunov criterion are provided. Additionally, the controller parameters are tuned using a hybrid meta-heuristic optimizer, facilitating the design stage of this adaptive nonlinear control algorithm for non-specialized control designers in adaptive control theory. The developed active damping strategy is easily adapted to other inverter topology or filter structures, requiring minimal adjustments in implementation or tuning, which enhances its reuse feature. Experimental results utilizing a three-phase 6.75 kW laboratory test bench, equipped with a TMS320F28335 DSP microcontroller, demonstrate the feasibility of the implemented controller to ensure system stability and energy quality. The control law is computationally efficient, consuming approximately 40% of the available processing capacity of the microcontroller. The total harmonic content is 3.70% (phase A), 4.24% (phase B), and 3.88% (phase C), respecting the IEEE 1547 standard.