Investigation of voltage and transient stability of HVAC network in hybrid with VSC-HVDC and HVDC Link

This paper reports on the stability of power systems using a weak two area HVAC link, in hybrid with HVDC and VSC-HVDC transmission schemes as case studies. The purpose of the study is to show the mitigating effect of the VSC-HVDC system on both voltage and transient stability in power systems, as compared to other transmission schemes. In the study, steady state analysis was used to investigate voltage stability of a weak two area HVAC network, using PV and QV curves. Also, the responses of the voltage angle and voltage magnitude to a 3-phase short circuit fault, was also used for this analysis. The transient stability study was conducted using a 3-phase short circuit fault also, and the responses of the active and reactive power, the generator speed, and the rotor angle was used to analyze the transient stability of the networks. The study shows that the VSC-HVDC system improved both transient and voltage stability, whilst the classical HVDC scheme improved the transient stability, but was unstable with the voltage stability due to the actions of the HVDC controllers on the weak tie with the AC link.