Examination on the parameter stability region of the VSC control system in VSC-HVDC transmission systems

Nowadays, the voltage source converter (VSC)-based high-voltage direct current (HVDC) transmission technology is widely adopted for the integration of renewable power generations. However, the grid-connected VSC systems may also cause power system instability issues. This study focuses on the parameter stability region of VSC control system in VSC-HVDC transmission systems. The small-signal linearised model of the whole power system is firstly established and on the basis of which the modal analysis method is applied to obtain the parameter stability region of VSC control system. The results show that the region is mainly affected by both the selection of the initial operating point of VSC and the dynamic interaction between the AC system and the VSC. From these two perspectives, the parameter stability regions of the VSC control system under different operating conditions are investigated. Meanwhile, it is found in the study that when modal coupling occurs between the oscillation modes corresponding to AC system and VSC, the parameter stability regions of the VSC control system obtained in the previous analysis will be deteriorated. Consequently, in terms of stability region, an evaluated method for VSC control system is proposed and validated through case study.