Abstract: The wide range change of grid impedance under the grid voltage proportional feed-forward control can easily lead to the resonance or instability of grid-connected inverters, so an impedance reshaping and resonance suppression strategy that combines the improved grid voltage feed-forward control with advanced correction is proposed. It first connects a Second-Order Generalized Integrator (SOGI) in the traditional grid voltage proportional feed-forward link to reduce the positive feedback caused by the coupling of grid voltage proportional feed-forward and line impedance, which improves the system stability margin to a certain extent. Then, the advanced phase correction is introduced to the current feedforward channel to compensate the system phase margin. Third, the phase angle margin at the intersection of the inverter output impedance and grid impedance is improved to avoid the resonance occurrence, the inverter robustness is strengthened with the wide range change of grid impedance, and the specific implementation process and parameter design ideas are given. Finally, the feasibility of the proposed strategy is verified by simulation experiments.

    Key words: weak grid; LCL-type inverter; second-order generalized integrator; phase compensation; impedance reshaping