Transient Stability Analysis of Grid-Following VSCs Considering Voltage-Dependent Current Injection During Fault Ride-Through

Abstract

This article analyzes the transient stability of grid-following voltage source converters (GFL-VSCs) considering the voltage-dependent current injection (VDCI) dynamics during fault ride-through (FRT). The dynamic interaction between the VDCI and the phase-locked loop (PLL) under the weak grid is revealed to provide insight for their impact on system transient stability. The condition of existence of equilibrium points (EPs) of VSC-grid system during grid faults is first investigated by using a static model considering the VDCI. Then, a dynamic model is developed to characterize the capability of VSC in converging to the EPs during grid faults. It is revealed that the <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">K</i> -factor, which determines the characteristic of the VDCI, has a crucial impact on the transient stability of the system. Finally, case studies based on electromagnetic transient (EMT) simulation and experiment are given to validate the theoretical findings.