Quasi-static stability of HVDC systems considering dynamic effects of synchronous machines and excitation voltage control

Recent works have shown the impact of dynamic system on the power stability of HVDC systems by different modeling. This had been mainly studied from an empirical approach based on time-domain simulations but rigorous justification from a mathematical standpoint is deemed essential. Thus in this paper, a mathematical model of power/voltage stability in HVDC systems incorporating detailed machine representation and voltage control is presented. Based on this, analytic expressions of power/voltage stability indices are derived. These expressions explicitly reveal the fundamental difference between the corresponding power/voltage stability indices with and without considering dynamic effects of the machine and its excitation voltage control. Thereby, the dynamic impacts of the machine can be characterized quantitatively. The relationships between the indices and their quasi-static counterparts are also shown. Time-domain simulations also verify the dynamic impacts as predicted by the analytic models.