Enhanced ADRC With Selection Mechanism-Based PRC-ESO for Single-Phase Grid-Tied Inverters in a Weak Grid

Repetitive controller (RC)-based active disturbance rejection control (ADRC) schemes exhibit superior performance in periodic disturbance rejection of the single-phase grid-tied inverter (GTI) system with rapidly varying periodic disturbances (RVPDs) and modeling uncertainties. However, these schemes cannot deal with aperiodic disturbance signals. In addition, aperiodic disturbances deteriorate the learning behavior of the RC, resulting in a sluggish dynamic response of the RC-based ADRC schemes. To address these issues, an enhanced ADRC (EADRC) scheme is proposed, which integrates a switching mechanism (SM)-based plug-in RC-based extended state observer (PRC-ESO) to address the limitations of RC in handling aperiodic disturbances. The SM is presented for eliminating the negative influence of the aperiodic disturbance on the RC, thereby enhancing the tracking error convergence rate of the EADRC system. Then, an ideal magnitude and phase compensator is developed to enable the controlled plant of the RC to exhibit frequency characteristics with unity gain and zero phase shift, enhancing the RVPDs rejection performance of the EADRC system. The effectiveness of the proposed EADRC scheme is validated on a single-phase GTI system. The experimental results demonstrate that the proposed EADRC scheme exhibits strong robustness against modeling uncertainties and enhanced rejection performance for the RVPDs.