Impedance-based Stability Analysis of Two- Terminal Cascaded Voltage Source Converter System

The voltage source converters (VSC) have been widely applied in power systems and the stability issue has become a hot topic in recent years. This paper focuses on the stability analysis of dc bus of the systems based on grid connected voltage source converters, which contain single VSC stations and two-terminal cascaded system. The DC side impedance model of each VSC has been established. The stability of single VSC system has been analyzed by determining whether the closed loop impedance has right-half-plane (RHP) pole or not. And, the stability of two-terminal cascaded system is determined by Nyquist Criterion. How the parameters influence the stability of the systems has been analyzed in detail. Finally, the impedance models and stability analysis have been verified by simulation.