Improvement of subsynchronous torsional damping using VSC HVDC

This paper presents a study of SSTI related to VSC HVDC. The study was conducted with well established methods, which have been used in the design of SSDC and evaluation of SSTI in classic HVDC. Identical control systems for VSC HVDC as in the real plant are included in the study. The paper will show how the VSC and its control contribute to the electrical damping on subsynchronous oscillations. Different operation modes, load levels, control modes and AC network conditions have been considered in the study.