When the converter bus voltage of a voltage source converter-based high voltage direct current (VSC-HVDC) system drops below a certain predetermined threshold, the system enters low-voltage ride-through (LVRT) mode to avoid overcurrent and potential equipment failure, during which it operates as a controlled current source. The influence mechanism of LVRT control strategies on short-circuit current and overall system stability remains not yet fully and systematically investigated. First, this paper provides an overview of several LVRT strategies for VSC-HVDC systems and examines their effects on short-circuit current contribution. Next, it analyzes in detail the mechanisms through which active and reactive currents injected during LVRT impact system frequency stability, voltage stability, and synchronization stability. To address these interrelated issues, an optimized and comprehensive LVRT strategy incorporating short-circuit current constraints is proposed. The approach determines the active current ratio based on system frequency stability requirements and dynamically adjusts the active current recovery rate via phase control of the VSC-HVDC bus. The remaining capacity is allocated to reactive current support, thereby enhancing voltage and synchronization stability while maintaining sufficient short-circuit current margin and system frequency stability. Finally, simulations conducted on the PSS/E platform, using actual grid data from a selected cross-section system, validate convincingly the effectiveness of the proposed parameter optimization strategy for VSC-HVDC low-voltage ride-through.
Zhu et al. (Thu,) studied this question.