Voltage Stability Analysis at Converter Buses in Combined AC/DC Systems

This paper presented a method of estimating voltage stability for an AC/DC system based on nonlinear programming analysis of voltage stability for an AC system, and built the AC /DC model. This method converts the calculation of point of collapse (PoC) of AC/DC systems to a problem of optimizing load, which is solved by Sequential Quadratic Programming method (SQP). The method can handle various inequality constraints with strong robustness and good convergence and consider the effects of different High Voltage Direct Current (HVDC) transmission control modes on voltage stability. Finally numerical examples proved the validity of the proposed model and algorithm.