A Current Saturation Strategy for Enhancing the Low Voltage Ride-Through Capability of Grid-Forming Inverters

Abstract

This brief proposes a new current saturation strategy (CSS) for grid-forming (GFM) inverters to comply with the existing low-voltage ride-through (LVRT) capability requirements. The proposed control philosophy enables the GFM inverters to follow one of the standardized grid codes by limiting the output current during LVRT via a new control parameter, the power factor angle (PFA). First, a nonlinear mathematical model capturing the full-order averaged dynamics of a GFM inverter embedded with current limiting control has been developed. Following this, the proposed CSS has been analytically evaluated by developing a simplified equivalent circuit model. Finally, numerical and experimental results are presented to verify the accuracy of the CSS for assessing the large-signal stability of a GFM inverter subjected to severe symmetrical grid faults.