A Novel RC-ESO-ADRC for Harmonics Suppression and Robustness Improvement of Grid-Tied Inverters in a Weak and Distorted Grid

Repetitive control-based extented state observer (RC-ESO) enhances the estimation accuracy of periodic harmonic disturbances. However, it exhibits a slow convergence rate of disturbance estimation, limited steady-state estimation accuracy, and a lack of systematic design. An improved active disturbance rejection control (ADRC) current control scheme based on a novel RC-ESO (NRC-ESO) is proposed in this paper. An ideal compensation filter (ICF) is used to design the NRC-ESO, achieving a faster convergence rate for disturbance estimation. Additionally, a zero-phase low-pass filter is embedded in the NRC-ESO to reduce the current steady-state error and mitigate the impact of sensors high-frequency noise. The anti-disturbance ability, tracking performance, system stability, and detail parameter optimization design of the NRC-ESO-based ADRC (NRC-ESO-ADRC) are presented. The experimental results reflect the effectiveness of current harmonics suppression and robustness.