Steady-State Voltage Stability Analysis of AC-DC Hybrid Power System with VSC-HVDC

Several high voltage direct current transmission systems based on voltage source converter (VSC-HVDC) have been put into operation in recent years. Research on voltage stability analysis technology has practical significance. In this paper, by analyzing the operational characteristics of voltage source converter, and considering the effect of reactive current constraint on the dynamic reactive reserve of the converter station, a processing method for reactive current constraint based on bi-directional switching logic is presented. On this basis, the load margin of AC-DC hybrid power system with VSC-HVDC is computed by continuation power flow method (CPF), and an approach to identify limit-induced bifurcation point caused by reactive current over-limit is provided. The influences of different control modes and control mode shift of VSC on the voltage stability margin are analyzed. Simulation results on the modified IEEE 39-bus standard system verify that the proposed method is reasonable and effective.