Resilient Adaptive Control for Single-Phase Grid Following Distribution Inverters

most frequency-domain control design methods for single-phase grid-connected inverters are based on the assumption that the grid's frequency remains close to the nominal value. Resonant controllers have been demonstrated to be an effective solution, attaining robust performance thanks to the embedded internal model of a sinusoid at the grid frequency. However, the performance of these compensators is not guaranteed as the grid frequency deviates from its nominal value, which is becoming an even likelier condition with the growing penetration of non-conventional renewables at the distribution level. This paper introduces a novel control strategy that ensures performance despite arbitrary grid frequency variations. The key feature of the controller is introducing an adaptive internal model that follows the grid's frequency and adjusts the control gains accordingly. The controller design requires no information about bounds on frequency excursions, which is a necessary assumption for designing robust controllers. Hence, it is called resilient since it operates properly for abnormal frequency excursions.