A hybrid repetitive control strategy of grid-connected five-level inverter under LVRT operation

The utilization of multilevel inverters in grid-connected photovoltaic systems is examined, with a focus on digital PI controllers. A study analyzing the LCL filter and its central role in power electronics is also referenced. Furthermore, a current-control method for voltage-source inverters is explored, utilizing both feedback and repetitive control strategies. Firstly, a return branch is added to the LCL filter to achieve leakage current suppression. Secondly, the HPC suppresses the common-mode resonance current (CMRC) and improve the dynamic response speed under LVRT operation, which achieves a low total harmonic distortion (THD). Finally, the finiteness of this method is verified by simulation.