Reconstruction of Impedance Criteria and Stability Enhancement Strategies for Grid-Connected Inverters

Grid-connected inverters play an indispensable and crucial role between new energy power generation devices and the power grid. As an important method for stability analysis of grid-connected inverters, impedance criteria have been widely applied. However, traditional impedance criteria have the problem of inaccurately representing system stability margins. Moreover, under weak grid conditions where grid impedance cannot be ignored, voltage disturbances at the point of common coupling will cause phase angle deviations in the output of the phase-locked loop, thereby affecting the stability of the control system. To address these issues, this paper establishes a stability analysis model based on the reshaping of impedance criteria and proposes a q-axis improved control compensation method, which expands the adaptability range of grid impedance for inverters and enhances the stability of grid-connected inverters. Finally, the correctness of the proposed algorithm is verified through experiments.