Transient Voltage Stability Analysis and Enhancement of Grid-Following Converters Considering DC-link Voltage Control Dynamics

With the large-scale integration of renewable energy resources through grid-following converters, the voltage support capability of the system is weakened, thereby increasing the risk of voltage instability. Existing studies mainly focus on the transient voltage stability of induction motors (IMs), where the dynamics of voltage source converters (VSCs) are often neglected. However, VSCs with DC-link voltage control (DVC) also face the risk of transient voltage instability under grid faults, even when the voltage-supporting effect of VSCs during low-voltage ride through (LVRT) is considered. Such an instability phenomenon poses a tremendous threat to the stable operation of VSC-dominated power systems, which has not been addressed in existing research. To fill this gap, this paper provides a theoretical explanation of the VSC's transient performance under DVC and LVRT, and reveals the transient voltage instability mechanism of modern power systems with high penetration of VSCs. To mitigate such instability, this paper proposes an adaptive current-limiting control strategy after analyzing the impact of current limitation on transient voltage stability. Simulation results verify the correctness of the theoretical analysis and the effectiveness of the proposed control strategy.