An Improved Time-Delay Compensation Scheme for Enhancing Control Performance of Digitally Controlled Grid-Connected Inverter

Capacitor-current-feedback active damping is widely adopted in digital-controlled LCL-type grid-connected inverter to eliminate the system resonance generated by the LCL-filter. However, the digital-control-delay will lead to poor robustness against grid impedance. Furthermore, under weak grid conditions, the variable grid impedance may undermine the system stability. To address this issue, an improved time-delay compensation method is proposed in this paper. The novel scheme can effectively compensate the digital-control-delay, and thus enhance the stability of the system under various resonant frequencies with better dynamic response performance. By selecting the capacitor-current-feedback coefficient reasonably, stable operation can be maintained under grid impedance variations. Finally, simulation results validate the effectiveness and feasibility of the proposed approach.