Active-Damping Disturbance-Rejection Control Strategy of LCL Grid-Connected Inverter Based on Inverter-Side-Current Feedback

In the medium- and high-power grid-connected photovoltaic systems, the controller bandwidth is constrained due to the low switching frequency. This issue limits the resonant frequency of the traditional proportional multiresonant (PMR) controller and then makes it difficult to suppress the main low-frequency harmonics in the grid-connected current. In addition, it is difficult for PMR to maintain good performance under severe operating conditions, such as the grid voltage containing the resonant-frequency harmonic and the grid voltage sagging. Based on the abovementioned practical problems and on-site requirements, a novel first-order active-disturbance-rejection active-damping control strategy based on the inverter-side-current feedback (ICF-ADRC-AD) for the LCL grid-connected inverter is proposed in this article. The standard form of the system block diagram is deduced, and the stability and immunity of the system are analyzed. Finally, the effectiveness and superiority of the proposed control strategy under different operating conditions are verified by simulation and experiment. The control strategy proposed in this article improves the suppression effect of low-frequency total harmonic and resonance and also improves the stability and immunity of the system.