Transient Stability of Grid-Forming Converters with Flexible DC-Link Voltage Control

Abstract

This paper proposes a flexible dc-link voltage control scheme for grid-forming converters. In the approach, instead of cascading the dc-link voltage control with the power synchronization control, a paralleled connection of the two loops is employed, which leads to an additional control degree-of-freedom for flexible damping design. Further, the impact of this flexible dc-link voltage control on the transient stability of grid-forming converters is analyzed, considering both inverter and rectifier operation modes. It is shown that the method enhances the transient stability with the flexible damping design. The efficacy of control method and stability analysis are validated by experimental tests.