Control Strategy Based on <inline-formula> <tex-math notation="LaTeX">$\text{H}\infty$ </tex-math></inline-formula> Repetitive Controller With Active Damping for Islanded Microgrid

To overcome the drawbacks of the proportional plus integral (PI) control based strategy, i.e., limitation for harmonic suppression and performance deterioration under load variation, a voltage control strategy based on the $\text{H}\infty $ repetitive controller with inverter-side current feedback damping is proposed for the inverter in islanded microgrid. The $\text{H}\infty $ repetitive controller provides good robustness against parameter perturbation and ensures the output voltage of low total harmonic distortion. Compared with other damping methods, a good resonance suppression and a better attenuation of the high-order harmonics can be achieved under the proposed strategy, which further improves the control performance of the voltage repetitive control system. A state space model including the damping coefficient is built to implement order reduction of the high-order controller, thereby simplifying the digital implementation while nearly without performance degradation. Moreover, the frequency response analysis shows that the order reduction can improve the adaptability of the controller to parameter variation. Finally, experiments and simulations verify the correctness of the analysis.