Control of grid-following converter-interfaced resources for improved transient stability of power systems

Abstract

Power-electronic converters are increasingly utilized to integrate renewable and distributed energy resources (DERs) with conventional power grids. The increasing penetration of converter-interfaced resources (CIRs) could, in turn, influence the transient stability of traditional synchronous generators (SGs) in power systems due to their fast response and low inertia nature. This paper evaluates the transient stability of power systems containing SGs and grid-following CIRs under various control schemes and penetration of CIRs. The critical clearing time (CCT) of the SGs is used as the criterion for assessing transient stability following a fault. It is demonstrated that stability margins can be improved by actively controlling the grid-following CIRs during fault and post-fault periods. The proposed method is shown to increase the CCT compared to the conventional/alternative approaches, particularly the common practice that requires CIRs to inject only reactive power to support/regulate voltage during the fault period. It is also shown that with increased penetration of CIRs, if controlled appropriately, the transient stability of SGs can be improved, which is not commonly expected in low-inertia systems.

Keywords

• Converter-interfaced resource (CIR)
• Critical clearing time (CCT)
• Grid-following converter
• Transient stability