Large-Scale Power Base’s Impact on Low Frequency Oscillation Characteristic in UHVAC Power Transmission System

The dynamic stability of ultra-high voltage alternating current (UHVAC) transmission system with large-scale power bases has not been clearly discussed before. This paper studies the low frequency oscillation (LFO) characteristic of UHVAC system through complex torque coefficient method (CTCM) and finds out the reasons why UHVAC system is more vulnerable to LFO problem. It is pointed out that the bulk capacity and long distance make UHVAC system's damping torque coefficient much smaller than conventional system's, which lets UHVAC system's operation point closer to the safety edge and decreases system's dynamic stability. The comparisons between UHVAC system and conventional system in practical multi-machine systems further validate the theoretical analysis. Finally, the suggestions for UHVAC systems are given based on the analysis in the view of dynamic stability.